CA1223089A - Barrierless high-temperature lift-off process - Google Patents
Barrierless high-temperature lift-off processInfo
- Publication number
- CA1223089A CA1223089A CA000495660A CA495660A CA1223089A CA 1223089 A CA1223089 A CA 1223089A CA 000495660 A CA000495660 A CA 000495660A CA 495660 A CA495660 A CA 495660A CA 1223089 A CA1223089 A CA 1223089A
- Authority
- CA
- Canada
- Prior art keywords
- layer
- polyimide layer
- temperature
- polyimide
- forming
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
- H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
- H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
- H01L21/76838—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the conductors
- H01L21/76877—Filling of holes, grooves or trenches, e.g. vias, with conductive material
- H01L21/7688—Filling of holes, grooves or trenches, e.g. vias, with conductive material by deposition over sacrificial masking layer, e.g. lift-off
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/027—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34
- H01L21/0271—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34 comprising organic layers
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/027—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34
- H01L21/0271—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34 comprising organic layers
- H01L21/0272—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34 comprising organic layers for lift-off processes
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic System or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
- H01L21/31—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to form insulating layers thereon, e.g. for masking or by using photolithographic techniques; After treatment of these layers; Selection of materials for these layers
- H01L21/3105—After-treatment
- H01L21/311—Etching the insulating layers by chemical or physical means
- H01L21/31127—Etching organic layers
- H01L21/31133—Etching organic layers by chemical means
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/10—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern
- H05K3/14—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern using spraying techniques to apply the conductive material, e.g. vapour evaporation
- H05K3/143—Masks therefor
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S438/00—Semiconductor device manufacturing: process
- Y10S438/942—Masking
- Y10S438/948—Radiation resist
- Y10S438/951—Lift-off
Abstract
ABSTRACT
A lift-off metal deposition process in which a high temperature polyimide layer (i.e. a polyimide having a high imidization temperature) is applied to a first polyimide layer. The two layers are anisotropically etched through a photoresist mask to form vias in the first polyimide layer. After application of a metal layer, the high-temperature polyimide layer is lifted off the first polyimide layer, which remains as a passivation layer.
A lift-off metal deposition process in which a high temperature polyimide layer (i.e. a polyimide having a high imidization temperature) is applied to a first polyimide layer. The two layers are anisotropically etched through a photoresist mask to form vias in the first polyimide layer. After application of a metal layer, the high-temperature polyimide layer is lifted off the first polyimide layer, which remains as a passivation layer.
Description
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BARRIER LESS HI TEMPERATURE LIFT-OFF PROCESS
Technical Field _ .
The invention relates to a method of forming metal layers under high-temperature conditions.
Cross-~eference to Related Applications Reference is made to US. Patent No. 4,624,740, issued November 25, 1986, entitled "Tailoring of Via Hole Sidewall Slope", by AND.
Abram, ARC Bismuth, CLUE. Holland and SUP.
Ilol:Land, assigned to the assignee of the present invention/ which discloses and claims a method of forming vies in a first polyamide layer through apertures in a second polyamide layer. The thickness of the second polyamide layer is varied in order to alter the slope of the via hole sidewalls.
Background At Many methods are known for forming a pat-turned conductor layer on a substrate. The two most common methods of forming such a layer are subtractive etching and lift-off techniques. In subtractive etching, after a blanket conductor layer is deposited on the substrate, the layer is etched through a photo mask in order to remove undesired portions thereof. In lift-off, a layer (typically an insulator such as polyamide) is deposited on a substrate, and is patterned through a photo mask The conductive layer is then deposited on the patterned insulator, and the Jo BYWAY
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insulator is removed from (i.e. "lifted off" of) the substrate, taking with it the undesired portions of the conductive layer. Of these two techniques, it has been found that lift-off is more desirable in that the solvents used to remove the insulator in lift-off cause less damage to the underlaying substrate than do the etch processes ego. a plasma etch or a reactive ion etch) used in subtractive etching. Also, the conductor profile resulting from lift-off ; processing minimizes step coverage problems in subsequent conductor layers.
An example of such a li~t-oEf process is disclosed in US. Patent No. 4,4$1,971, entitled "Lift-Off Wafer Processing", issued June 5, 1~84 to Mailgram and assigned to Fairchild Camera and Instrument Corp. As disclosed in this patent, a layer of pre-imidized polyamide it a copolymer ; of an aromatic cycloaliphatic Damon and a dianhydride) is coated on a semiconductor substrate, and a silicon dioxide barrier layer is formed on the polyamide. The barrier layer protects the polyamide layer during photo lithographic processing. After these layers are patterned through a photo resist mask, a metal layer is deposited on the structure. The polyamide layer is then stripped off the silicon, lifting off the undesired portions of the metal layer. By use of the particular polyamide I copolymer disclosed, the metal can be deposited at a temperature of 250C-300C, reducing physical faults in the deposited metal. Note that during both the deposition and lift-off of this polyamide copolymer, a harmful organic solvent such as ethylene chloride must be used.
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In the article by Momma et at, 'IPolyimide Liftoff Technology for High-Density LSI
Metallizationl', IEEE Transections on Electron Devices, Vol. ED-28, No. 5, May 1981 pp. 552-556, a lift-off metallization process is disclosed in which a polyamide having a high imidization temperature, sold under the trade name "PI" by the Hitachi Chemical Co., lid of Japan, has an overlaying molybdenum barrier layer formed thereon. The PI serves as the lift-off structure (i.e. the layer which is lifted off from the underlaying layers).
n In the article by Winter, "petal Deposition With Polyamide Lit Of Technique", IBM Technical H
D_~cl03ur- ~ulleti~, Vol. 17, No. 5, October 1974, p. 1309, a first layer of polyamide is patterned through a photo resist mask. After the metal is deposited, the photo resist mask is removed from the first polyamide layer and a second polyamide 20 layer is applied for passivation.
. .
As discussed above, special polyamide layers are needed in order to carry out high temperature lift-off processes. However, these special polyamides are typically used in conjunction with 25 overlaying barrier layers, which protect the polyamides from etching during the definition of a photo resist mask disposed on the barrier layer.
It would be advantageous to eliminate these barrier layers, since they add to manufacturing 30 cost.
r Summary of the Invention It is thus an object of the invention to provide an improved metal lift-off process.
* Registered Trade Mark BYWAY
I
It is another object of the invention to provide a lift-off structure which is compatible with high temperature metal deposition.
It is a further object OX the invention to provide an improved metal lift-off process using polyamide as the lift-off structure, wherein the polyamide layer is not protected by a barrier layer and can be processed using conventional solvents.
;
These and other objects of the invention are realized by a metal deposition process in which a high-temperature polyamide layer is applied to an underlaying polyamide layer. The two polyamide layers are anisotropically etched through a photo resist mask to form vies in the underlaying polyamide layer. After application of a metal layer, the high-temperature polyamide layer is lifted off the underlaying polyamide layer, which remains as a passivation layer. Note that there is no barrier layer between the high-temperature polyamide layer and the photo resist mask. The high-temperature polyamide layer can be processed using conventional solvents.
Brief Description of the Drawings The foregoing and other structures and teachings of the invention will become more apparent upon a description of the best mode as rendered below. In the description to follow, reference will be made to the accompanying draw-in, in which:
BYWAY
3~3~9 Figs. 1-3 axe cross-sectional views of a semiconductor structure undergoing the process steps of a first embodiment of the invention, and Figs. 4-8 are cross sectional views of a semiconductor structure undergoing the process steps of a second embodiment of the Invention.
Best Mode for Carrying Ox the Invention With reference to Figs. 1-3, a first embody-mint of the invention will now be described. As shown in Fig. 1, a substrate 10 has a layer of polyamide 14 spin-applied thereon. While substrate 10 is shown as being a bare silicon substrate, it is to be understood that any one of the semiconductor structures or device currently ; 15 manufactured in the industry ego. FRET or bipolar transistors, storage capacitors, resistors, etc.
could be arranged on substrate 10, and that the patterned conductor Layer to be described is patterned so as to form an electrical contact to any one of these structures. In other words, substrate 10 is shown as being bare merely for the purposes of more clearly illustrating the i invention.
Polyamide layer 14 can be made up of any one Of the known polemic acid/imides that are stable up to 350C. For example, polyamides sold under the names "PMDA-ODA" and Dupont 2555" by the Dupont Company of Wilmington, Delaware could be used. Polyamide layer 14 should be approxi-mutely as thick as the metal layer to be applied For a second, third, etc. level metal, polyamide layer 14 should be approximately 1.8-2.0 em thick.
BYWAY
I
In addition to providing passivation, polyamide layer 14 produces a "step" for the metal layer to cover. This enhances discontinuities in the metal layer, facilitating lift-off as described below.
It is to be understood that this embodiment of the invention relates to the formation of any level of metallurgy on the processed substrate.
If the invention is used to provide a first level of metallurgy, an additional passivating layer (e.g. silicon nitride, silicon dioxide or sputtered quartz) could be formed between polyamide layer 14 and substrate 10 for the purpose ox providing additional insulation This additional passivating layer would have to be lo etched separately (i.e. etched using a separate mask) from the etching of the polyamide layers as discussed below Further, if this embodiment of the invention is used to provide via studs to structures formed on the substrate or to other metal layers, a similar passivating layer could be used which would be patterned using the same mask as the polyamide layers (only the etch ambient or plasma would have to be chanced. Either way, the total thickness of the combination of polyamide 14 and the additional passivating layer should approximately equal the thickness of the metal layer to be applied. For the first level metal, the combined thickness should be 1.0-1.2 em; for second, third, etc. level metals, the combined thickness should be 1.8-2.0 em. The additional passivation layer can be made up of any insulator formed at a temperature which is less than the annealing temperature of underlaying conductor layers It is emphasized that while incorporation of these additional passivation layers is ;
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preferred in that they improve reliability, they can be deleted from the process of the invention if desired.
A layer of high-temperature polyamide 16 is then spin-coated onto the surface of polyamide layer 14. Polyamide 16 can be made of any one of the known "high temperature" polyamides which do not fully immediacy at temperatures below approximately 250C- 280C. Such polyamides are thus compatible with high-temperature metal deposition. An example of such a polyamide is Purloin PI-2566, sold by the Dupont Company of Wilmington, Delaware. "Purloin" is a trademark of the Dupont Company. Another such polyamide it sold under the trade name "PI" by the Hitachi Chemical Co., lid ox Japan. These high-temperat~l~e polyamides can be distinguished from the polyamide copolymer disclosed in the Mailgram patent in that these polyamides are not pre-imidized and they can be processed using solvents commonly used in the industry. Whichever of these two high-temperature ` polyamides is used, polyamide layer 16 should be at least as thick as the metal layer to be deposited.
The polyamide 16 should be heated to a temperature below its final cure temperature in order to facilitate subsequent etching. More specifically, it should be heated to at least 120C in order to harden, and preferably should be ; 30 heated to approximately 200C in order to drive off excess solvent. For example, a 2 em layer of PI-2566 is heated to 200C for approximately 20 minutes at temperature. Heating to 200C should be sufficient to fully immediacy polyamide layer 14.
BYWAY
~23~39 A layer of photo resist 18 is then applied to the surface of high-temperature polyamide layer 16. This layer of photo resist must be thick enough (e.g. 3 em) such that the underlying polyamide 16 will not be attacked when the vies are etched. That is, by making the photo resist sufficiently thick, there is no need for a barrier layer in order to protect portions of the polyamide layer 16 which are not to be removed during etching. The photo resist can be mud any novolac resin-based positive photo resist.
Preferably, the photo resist is chosen such that it can be exposed and developed (i.e. etched in an aqueous base such as sodium metasilicate (Nash)) as per conventional processing.
After photo resist 18 has been exposed and developed, the high-temperature polyamide 16 and polyamide 14 are anisotropically reactive ion etched (RYE) in an oxygen plasma. Note that during the course of this itch step, much or elf of the photo resist 18 is consumed. See Fig. 2.
Thus, vies having substantial vertical sidewalls are etched into the polyimlde layer 14.
j Then, as shown in Fig. 2, a 1.8-2.0 em layer of conductive material 20 ~1.0-1.2 em for first level metal) is formed on the structure, filling the vies formed in polyamide layer 14. Conductive material 20 may consist of any of the conductive materials used in forming patterned interconnection layers in semiconductor processing (e.g. metals such as aluminum, copper, etc.;
silicides of tungsten, titanium, molybdenum, etc.). A feature of the invention is that during the deposition of layer 20~ substrate 10 can be BYWAY
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g heated such that the physical defects in the resulting interconnection layer (e.g. cracks, etc.) can be minimized. The substrate can be heated to temperatures of approximately 200C-280C. Note that the only constraint on these deposition temperatures is that they must not be greater than the "full" imidization temperature of polyamide layer 16. On other words, during high temperature metal deposition, polyamide layer 16 should not be imidized beyond an insignificant (e.g. 2-5~) amount.
Finally, as shown in Fig. 3, high-temperature polyamide layer 16 is lifted off polyamide layer 14. This lift-off is performed by submersing the substrate in n-methyl pyrrolidone NIP solvent a approximately 80-90C for no more than 30 minutes.
Thus, the undesired portions of conductor layer 20 are removed. The remaining polyamide layer 14 serves to passivity the conductive layer. Note that polyamide layer 16 can be removed without affecting polyamide layer 14 because of the fact that polyamide 16 isn't fully imidized.
As described above, the process of the first embodiment of the invention utilizes a high-temperature polyamide without a barrier layer. In ; addition, the invention provides a polyamide layer which passivates the patterned conductor layer.
With reference to Fig. 4, a second embodiment of the invention will now be described. this embodiment relates to the formation of a patterned contact layer (i.e. a "pad metallization") which enhances the electrical contact between the final metallization level on the substrate and the chip ~Z~3~)~39 pads (i.e. "solder balls") or wire bonds which receive signals from sources external to the chip.
This contact layer also serves as a barrier layer, preventing the intermixing of the metallization metal with the chip pad or wire bond metals during the formation of the latter.
As shown in Fig. 4, an insulator layer 30 is first applied to a processed substrate loan A
final metallization level 32 is disposed on passivation 30 and is patterned to form an elongated area which provides the electrical contact to the solder ball or wire bond to be subsequently formed. Patterned conductor 32 Bills vies formed by insulation 30, and contacts semiconductor structures and/or previous patterned conductor layers wormed on substrate loan These underlying layers/structures are omitted from Figs. 4-8 in order to more clearly illustrate this embodiment of the-invention. It is to be emphasized that while insulator layer 30 and interconnection layer 32 could be processed in the manner of the first embodiment of the invention as described above, they are not limited thereto. In other words, interconnection layer 32 and insulator layer 30 could be made up of other materials and processed in other ways in addition to those materials and process steps of the first embodiment of the present invention Substrate lo is then covered by a final passivation layer 34. Passivation layer 34 can be made up of the aforementioned PMDA-ODA polyamide or its equivalent. Since polyamide 34 constitutes the final passivation layer, it should BYWAY
I
be relatively thick (in the order of 8 em) in order to protect the underlying structures. After polyamide 34 is spin-coated onto the substrate, it should be solidified by heating to 110C-130C for approximately 15 minutes at temperature.
A layer of high-temperature polyamide 36 is then applied to the surface of polyamide 34.
High-temperature polyamide 36 is made up of polyamides such as PI-2566 or PI, as discussed previously. Similarly to the first embodiment of the invention, the high-temperature polyamide 36 should be approximately as thick (e.g. 2-3 em) as the pad metallurgy to be subsequently formed.
Similarly to polyamide 34, the high-temperature polyamide 36 should be solidified by heating to 110-130C for approximately 15 minutes at temperature.
photo resist layer 38 is then deposited onto high-temperature Filmed layer 36. The photo-resist should be a positive photo resist as described in the first embodiment of the invention.
The positive photo resist is exposed and developed as per conventional processing, using aqueous bases such as potassium hydroxide (KOCH) or tetramethyl-ammonium hydroxide (TMAH). A feature of this embodiment of the invention is that by using a positive photo resist and the above-described enchants, the polyamide layers can be etched as the positive photo resist is developed.
; In other words, the photo resist is patterned and openings are created in the underlying polyamide BYWAY
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layers during the course of a single wet etch step. See Fig. 5.
Then, as shown in Fig. 6, the positive photo resist 38 is removed using n-butyl acetate or any other solvent (e.g. isopropyl alcohol or acetone) which removes photo resist without appreciably attacking underlaying polemic acids such as polyamide. Note that this removal step is not necessary, in that the photo resist could be removed as polyamide layer 36 is lifted off (as described below). By removing the photo resist separately, lift-off can be carried out more efficiently. After photo resist removal, the polyamide layers are heated to approximately lo 200C, which it sufficient to fully immediacy Leo achieve at least 98~ imidization) polyamide layer 34 and to immediacy high-temperature polyamide layer 36 by an inconsequential (2-5%) amount.
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The apertures formed in the polyamide 2Q layers are then briefly etched, using either plasma or wet etch techniques, in order to remove any impurities. A suitable wet enchant would be chromic-phosphoric acid, and a suitable atmosphere for plasma etching wound be OF or CF4+02. Again, while this step is not absolutely necessary, it contributes to the reliability of the overall process.
As shown in Fig. 6, a conductor layer 40 is then deposited. This metallurgy (e.g. a combination of chromium copper and gold or titanium, copper and gold) enhances the contact between the wire bond or solder ball to be subsequently formed and patterned conductor layer BYWAY
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32, while also providing an intermixing barrier there between. As in the first embodiment of the invention, the substrate 10~ should be heated to 200-280C during deposition in order to minimize the defects in the pad metallurgy layer.
Note that other metals (e.g. aluminum) could be used here.
Then, as sown in Fig. 7, undesired portions of the conductor layer 40 are removed by lifting off high-temperature polyamide layer 36 from polyamide layer 34, leaving behind pad metallurgy AYE. As in the first embodiment of the invention, the different volubility character- is tics ox the two polyamide films are produced by the extent to which they are imidized during the course ox previous processing steps it recall the cure step in which polyamide 34 is fully imidized while ; high-temperature polyamide 36 is not appreciably imidized). Polyamide 36 is then stripped using n-methyl-pyrrolidone at 80-95C for 30 minutes at temperature.
Finally, the lead-tin solder balls 42 are deposited on pad metallurgy AYE, using well known techniques (e.g. evaporating the solder through a metal mask), resulting in the structure as shown in Fig. 7. Alternatively, a wire bond metallurgy could be deposited on pad metallurgy AYE, again using conventional techniques.
The second embodiment of the invention as 30l described above can be modified as follows. In order to insure that sufficient contact is made between solder ball 42 and pad metallurgy AYE, it may be advantageous to configure the upper surface BYWAY
r of pad metallurgy AYE such that it overflows the vies formed in passivating polyamide layer 34. In order to do this, the process can be altered by eliminating the positive resist strip.
S Immediately before the vies are etched in order to remove impurities, briefly expose the structure to TMAH or KOCH solvents for a time sufficient to etch back the sidewalls of the opening formed in high-temperature polyamide layer 36 without appreciably affecting the vies in polyamide 34.
Thus, upon application of conductor layer AYE, the metal will overflow the vies in polyamide 34 by controllable amount Leo the extent to which the sidewalls ox the aperture in polyamide 36 were etched back). The process it then completed as described, resulting in a structure as shown in Fig. 8.
As described above, both embodiments of the invention present a method by which high-temperature polyamide layers are used to form liftoff structure without the need for a barrier layer. the first embodiment of the invention provides an efficient method of forming patterned interconnection layers, and the second embodiment of the invention provides an efficient method of providing an interconnection between the final metallization layer and the solder balls or wire bonds.
; It is to be understood that while modifications can be made by a person of ordinary skill in the art to the best mode as described above, such modifications fall within the general scope of the present invention.
BYWAY
BARRIER LESS HI TEMPERATURE LIFT-OFF PROCESS
Technical Field _ .
The invention relates to a method of forming metal layers under high-temperature conditions.
Cross-~eference to Related Applications Reference is made to US. Patent No. 4,624,740, issued November 25, 1986, entitled "Tailoring of Via Hole Sidewall Slope", by AND.
Abram, ARC Bismuth, CLUE. Holland and SUP.
Ilol:Land, assigned to the assignee of the present invention/ which discloses and claims a method of forming vies in a first polyamide layer through apertures in a second polyamide layer. The thickness of the second polyamide layer is varied in order to alter the slope of the via hole sidewalls.
Background At Many methods are known for forming a pat-turned conductor layer on a substrate. The two most common methods of forming such a layer are subtractive etching and lift-off techniques. In subtractive etching, after a blanket conductor layer is deposited on the substrate, the layer is etched through a photo mask in order to remove undesired portions thereof. In lift-off, a layer (typically an insulator such as polyamide) is deposited on a substrate, and is patterned through a photo mask The conductive layer is then deposited on the patterned insulator, and the Jo BYWAY
~3~89 ... . . . . ... . ... . . . . .. . . . . . . . . .
insulator is removed from (i.e. "lifted off" of) the substrate, taking with it the undesired portions of the conductive layer. Of these two techniques, it has been found that lift-off is more desirable in that the solvents used to remove the insulator in lift-off cause less damage to the underlaying substrate than do the etch processes ego. a plasma etch or a reactive ion etch) used in subtractive etching. Also, the conductor profile resulting from lift-off ; processing minimizes step coverage problems in subsequent conductor layers.
An example of such a li~t-oEf process is disclosed in US. Patent No. 4,4$1,971, entitled "Lift-Off Wafer Processing", issued June 5, 1~84 to Mailgram and assigned to Fairchild Camera and Instrument Corp. As disclosed in this patent, a layer of pre-imidized polyamide it a copolymer ; of an aromatic cycloaliphatic Damon and a dianhydride) is coated on a semiconductor substrate, and a silicon dioxide barrier layer is formed on the polyamide. The barrier layer protects the polyamide layer during photo lithographic processing. After these layers are patterned through a photo resist mask, a metal layer is deposited on the structure. The polyamide layer is then stripped off the silicon, lifting off the undesired portions of the metal layer. By use of the particular polyamide I copolymer disclosed, the metal can be deposited at a temperature of 250C-300C, reducing physical faults in the deposited metal. Note that during both the deposition and lift-off of this polyamide copolymer, a harmful organic solvent such as ethylene chloride must be used.
BYWAY
{ ~L~23~
In the article by Momma et at, 'IPolyimide Liftoff Technology for High-Density LSI
Metallizationl', IEEE Transections on Electron Devices, Vol. ED-28, No. 5, May 1981 pp. 552-556, a lift-off metallization process is disclosed in which a polyamide having a high imidization temperature, sold under the trade name "PI" by the Hitachi Chemical Co., lid of Japan, has an overlaying molybdenum barrier layer formed thereon. The PI serves as the lift-off structure (i.e. the layer which is lifted off from the underlaying layers).
n In the article by Winter, "petal Deposition With Polyamide Lit Of Technique", IBM Technical H
D_~cl03ur- ~ulleti~, Vol. 17, No. 5, October 1974, p. 1309, a first layer of polyamide is patterned through a photo resist mask. After the metal is deposited, the photo resist mask is removed from the first polyamide layer and a second polyamide 20 layer is applied for passivation.
. .
As discussed above, special polyamide layers are needed in order to carry out high temperature lift-off processes. However, these special polyamides are typically used in conjunction with 25 overlaying barrier layers, which protect the polyamides from etching during the definition of a photo resist mask disposed on the barrier layer.
It would be advantageous to eliminate these barrier layers, since they add to manufacturing 30 cost.
r Summary of the Invention It is thus an object of the invention to provide an improved metal lift-off process.
* Registered Trade Mark BYWAY
I
It is another object of the invention to provide a lift-off structure which is compatible with high temperature metal deposition.
It is a further object OX the invention to provide an improved metal lift-off process using polyamide as the lift-off structure, wherein the polyamide layer is not protected by a barrier layer and can be processed using conventional solvents.
;
These and other objects of the invention are realized by a metal deposition process in which a high-temperature polyamide layer is applied to an underlaying polyamide layer. The two polyamide layers are anisotropically etched through a photo resist mask to form vies in the underlaying polyamide layer. After application of a metal layer, the high-temperature polyamide layer is lifted off the underlaying polyamide layer, which remains as a passivation layer. Note that there is no barrier layer between the high-temperature polyamide layer and the photo resist mask. The high-temperature polyamide layer can be processed using conventional solvents.
Brief Description of the Drawings The foregoing and other structures and teachings of the invention will become more apparent upon a description of the best mode as rendered below. In the description to follow, reference will be made to the accompanying draw-in, in which:
BYWAY
3~3~9 Figs. 1-3 axe cross-sectional views of a semiconductor structure undergoing the process steps of a first embodiment of the invention, and Figs. 4-8 are cross sectional views of a semiconductor structure undergoing the process steps of a second embodiment of the Invention.
Best Mode for Carrying Ox the Invention With reference to Figs. 1-3, a first embody-mint of the invention will now be described. As shown in Fig. 1, a substrate 10 has a layer of polyamide 14 spin-applied thereon. While substrate 10 is shown as being a bare silicon substrate, it is to be understood that any one of the semiconductor structures or device currently ; 15 manufactured in the industry ego. FRET or bipolar transistors, storage capacitors, resistors, etc.
could be arranged on substrate 10, and that the patterned conductor Layer to be described is patterned so as to form an electrical contact to any one of these structures. In other words, substrate 10 is shown as being bare merely for the purposes of more clearly illustrating the i invention.
Polyamide layer 14 can be made up of any one Of the known polemic acid/imides that are stable up to 350C. For example, polyamides sold under the names "PMDA-ODA" and Dupont 2555" by the Dupont Company of Wilmington, Delaware could be used. Polyamide layer 14 should be approxi-mutely as thick as the metal layer to be applied For a second, third, etc. level metal, polyamide layer 14 should be approximately 1.8-2.0 em thick.
BYWAY
I
In addition to providing passivation, polyamide layer 14 produces a "step" for the metal layer to cover. This enhances discontinuities in the metal layer, facilitating lift-off as described below.
It is to be understood that this embodiment of the invention relates to the formation of any level of metallurgy on the processed substrate.
If the invention is used to provide a first level of metallurgy, an additional passivating layer (e.g. silicon nitride, silicon dioxide or sputtered quartz) could be formed between polyamide layer 14 and substrate 10 for the purpose ox providing additional insulation This additional passivating layer would have to be lo etched separately (i.e. etched using a separate mask) from the etching of the polyamide layers as discussed below Further, if this embodiment of the invention is used to provide via studs to structures formed on the substrate or to other metal layers, a similar passivating layer could be used which would be patterned using the same mask as the polyamide layers (only the etch ambient or plasma would have to be chanced. Either way, the total thickness of the combination of polyamide 14 and the additional passivating layer should approximately equal the thickness of the metal layer to be applied. For the first level metal, the combined thickness should be 1.0-1.2 em; for second, third, etc. level metals, the combined thickness should be 1.8-2.0 em. The additional passivation layer can be made up of any insulator formed at a temperature which is less than the annealing temperature of underlaying conductor layers It is emphasized that while incorporation of these additional passivation layers is ;
BYWAY
Jo ~2Z3~85~
.
preferred in that they improve reliability, they can be deleted from the process of the invention if desired.
A layer of high-temperature polyamide 16 is then spin-coated onto the surface of polyamide layer 14. Polyamide 16 can be made of any one of the known "high temperature" polyamides which do not fully immediacy at temperatures below approximately 250C- 280C. Such polyamides are thus compatible with high-temperature metal deposition. An example of such a polyamide is Purloin PI-2566, sold by the Dupont Company of Wilmington, Delaware. "Purloin" is a trademark of the Dupont Company. Another such polyamide it sold under the trade name "PI" by the Hitachi Chemical Co., lid ox Japan. These high-temperat~l~e polyamides can be distinguished from the polyamide copolymer disclosed in the Mailgram patent in that these polyamides are not pre-imidized and they can be processed using solvents commonly used in the industry. Whichever of these two high-temperature ` polyamides is used, polyamide layer 16 should be at least as thick as the metal layer to be deposited.
The polyamide 16 should be heated to a temperature below its final cure temperature in order to facilitate subsequent etching. More specifically, it should be heated to at least 120C in order to harden, and preferably should be ; 30 heated to approximately 200C in order to drive off excess solvent. For example, a 2 em layer of PI-2566 is heated to 200C for approximately 20 minutes at temperature. Heating to 200C should be sufficient to fully immediacy polyamide layer 14.
BYWAY
~23~39 A layer of photo resist 18 is then applied to the surface of high-temperature polyamide layer 16. This layer of photo resist must be thick enough (e.g. 3 em) such that the underlying polyamide 16 will not be attacked when the vies are etched. That is, by making the photo resist sufficiently thick, there is no need for a barrier layer in order to protect portions of the polyamide layer 16 which are not to be removed during etching. The photo resist can be mud any novolac resin-based positive photo resist.
Preferably, the photo resist is chosen such that it can be exposed and developed (i.e. etched in an aqueous base such as sodium metasilicate (Nash)) as per conventional processing.
After photo resist 18 has been exposed and developed, the high-temperature polyamide 16 and polyamide 14 are anisotropically reactive ion etched (RYE) in an oxygen plasma. Note that during the course of this itch step, much or elf of the photo resist 18 is consumed. See Fig. 2.
Thus, vies having substantial vertical sidewalls are etched into the polyimlde layer 14.
j Then, as shown in Fig. 2, a 1.8-2.0 em layer of conductive material 20 ~1.0-1.2 em for first level metal) is formed on the structure, filling the vies formed in polyamide layer 14. Conductive material 20 may consist of any of the conductive materials used in forming patterned interconnection layers in semiconductor processing (e.g. metals such as aluminum, copper, etc.;
silicides of tungsten, titanium, molybdenum, etc.). A feature of the invention is that during the deposition of layer 20~ substrate 10 can be BYWAY
~223~8~
g heated such that the physical defects in the resulting interconnection layer (e.g. cracks, etc.) can be minimized. The substrate can be heated to temperatures of approximately 200C-280C. Note that the only constraint on these deposition temperatures is that they must not be greater than the "full" imidization temperature of polyamide layer 16. On other words, during high temperature metal deposition, polyamide layer 16 should not be imidized beyond an insignificant (e.g. 2-5~) amount.
Finally, as shown in Fig. 3, high-temperature polyamide layer 16 is lifted off polyamide layer 14. This lift-off is performed by submersing the substrate in n-methyl pyrrolidone NIP solvent a approximately 80-90C for no more than 30 minutes.
Thus, the undesired portions of conductor layer 20 are removed. The remaining polyamide layer 14 serves to passivity the conductive layer. Note that polyamide layer 16 can be removed without affecting polyamide layer 14 because of the fact that polyamide 16 isn't fully imidized.
As described above, the process of the first embodiment of the invention utilizes a high-temperature polyamide without a barrier layer. In ; addition, the invention provides a polyamide layer which passivates the patterned conductor layer.
With reference to Fig. 4, a second embodiment of the invention will now be described. this embodiment relates to the formation of a patterned contact layer (i.e. a "pad metallization") which enhances the electrical contact between the final metallization level on the substrate and the chip ~Z~3~)~39 pads (i.e. "solder balls") or wire bonds which receive signals from sources external to the chip.
This contact layer also serves as a barrier layer, preventing the intermixing of the metallization metal with the chip pad or wire bond metals during the formation of the latter.
As shown in Fig. 4, an insulator layer 30 is first applied to a processed substrate loan A
final metallization level 32 is disposed on passivation 30 and is patterned to form an elongated area which provides the electrical contact to the solder ball or wire bond to be subsequently formed. Patterned conductor 32 Bills vies formed by insulation 30, and contacts semiconductor structures and/or previous patterned conductor layers wormed on substrate loan These underlying layers/structures are omitted from Figs. 4-8 in order to more clearly illustrate this embodiment of the-invention. It is to be emphasized that while insulator layer 30 and interconnection layer 32 could be processed in the manner of the first embodiment of the invention as described above, they are not limited thereto. In other words, interconnection layer 32 and insulator layer 30 could be made up of other materials and processed in other ways in addition to those materials and process steps of the first embodiment of the present invention Substrate lo is then covered by a final passivation layer 34. Passivation layer 34 can be made up of the aforementioned PMDA-ODA polyamide or its equivalent. Since polyamide 34 constitutes the final passivation layer, it should BYWAY
I
be relatively thick (in the order of 8 em) in order to protect the underlying structures. After polyamide 34 is spin-coated onto the substrate, it should be solidified by heating to 110C-130C for approximately 15 minutes at temperature.
A layer of high-temperature polyamide 36 is then applied to the surface of polyamide 34.
High-temperature polyamide 36 is made up of polyamides such as PI-2566 or PI, as discussed previously. Similarly to the first embodiment of the invention, the high-temperature polyamide 36 should be approximately as thick (e.g. 2-3 em) as the pad metallurgy to be subsequently formed.
Similarly to polyamide 34, the high-temperature polyamide 36 should be solidified by heating to 110-130C for approximately 15 minutes at temperature.
photo resist layer 38 is then deposited onto high-temperature Filmed layer 36. The photo-resist should be a positive photo resist as described in the first embodiment of the invention.
The positive photo resist is exposed and developed as per conventional processing, using aqueous bases such as potassium hydroxide (KOCH) or tetramethyl-ammonium hydroxide (TMAH). A feature of this embodiment of the invention is that by using a positive photo resist and the above-described enchants, the polyamide layers can be etched as the positive photo resist is developed.
; In other words, the photo resist is patterned and openings are created in the underlying polyamide BYWAY
~23~39`
.
layers during the course of a single wet etch step. See Fig. 5.
Then, as shown in Fig. 6, the positive photo resist 38 is removed using n-butyl acetate or any other solvent (e.g. isopropyl alcohol or acetone) which removes photo resist without appreciably attacking underlaying polemic acids such as polyamide. Note that this removal step is not necessary, in that the photo resist could be removed as polyamide layer 36 is lifted off (as described below). By removing the photo resist separately, lift-off can be carried out more efficiently. After photo resist removal, the polyamide layers are heated to approximately lo 200C, which it sufficient to fully immediacy Leo achieve at least 98~ imidization) polyamide layer 34 and to immediacy high-temperature polyamide layer 36 by an inconsequential (2-5%) amount.
.
The apertures formed in the polyamide 2Q layers are then briefly etched, using either plasma or wet etch techniques, in order to remove any impurities. A suitable wet enchant would be chromic-phosphoric acid, and a suitable atmosphere for plasma etching wound be OF or CF4+02. Again, while this step is not absolutely necessary, it contributes to the reliability of the overall process.
As shown in Fig. 6, a conductor layer 40 is then deposited. This metallurgy (e.g. a combination of chromium copper and gold or titanium, copper and gold) enhances the contact between the wire bond or solder ball to be subsequently formed and patterned conductor layer BYWAY
~23~
-13~
32, while also providing an intermixing barrier there between. As in the first embodiment of the invention, the substrate 10~ should be heated to 200-280C during deposition in order to minimize the defects in the pad metallurgy layer.
Note that other metals (e.g. aluminum) could be used here.
Then, as sown in Fig. 7, undesired portions of the conductor layer 40 are removed by lifting off high-temperature polyamide layer 36 from polyamide layer 34, leaving behind pad metallurgy AYE. As in the first embodiment of the invention, the different volubility character- is tics ox the two polyamide films are produced by the extent to which they are imidized during the course ox previous processing steps it recall the cure step in which polyamide 34 is fully imidized while ; high-temperature polyamide 36 is not appreciably imidized). Polyamide 36 is then stripped using n-methyl-pyrrolidone at 80-95C for 30 minutes at temperature.
Finally, the lead-tin solder balls 42 are deposited on pad metallurgy AYE, using well known techniques (e.g. evaporating the solder through a metal mask), resulting in the structure as shown in Fig. 7. Alternatively, a wire bond metallurgy could be deposited on pad metallurgy AYE, again using conventional techniques.
The second embodiment of the invention as 30l described above can be modified as follows. In order to insure that sufficient contact is made between solder ball 42 and pad metallurgy AYE, it may be advantageous to configure the upper surface BYWAY
r of pad metallurgy AYE such that it overflows the vies formed in passivating polyamide layer 34. In order to do this, the process can be altered by eliminating the positive resist strip.
S Immediately before the vies are etched in order to remove impurities, briefly expose the structure to TMAH or KOCH solvents for a time sufficient to etch back the sidewalls of the opening formed in high-temperature polyamide layer 36 without appreciably affecting the vies in polyamide 34.
Thus, upon application of conductor layer AYE, the metal will overflow the vies in polyamide 34 by controllable amount Leo the extent to which the sidewalls ox the aperture in polyamide 36 were etched back). The process it then completed as described, resulting in a structure as shown in Fig. 8.
As described above, both embodiments of the invention present a method by which high-temperature polyamide layers are used to form liftoff structure without the need for a barrier layer. the first embodiment of the invention provides an efficient method of forming patterned interconnection layers, and the second embodiment of the invention provides an efficient method of providing an interconnection between the final metallization layer and the solder balls or wire bonds.
; It is to be understood that while modifications can be made by a person of ordinary skill in the art to the best mode as described above, such modifications fall within the general scope of the present invention.
BYWAY
Claims (21)
1. A process for forming a patterned inter-connection layer on a processed semiconductor substrate, comprising the steps of:
forming a first polyimide layer on the processed substrate;
forming a high-temperature polyimide layer on said first polyimide layer;
forming a photoresist layer on said high-temperature polyimide layer;
exposing said photoresist layer and developing said photoresist layer in a solvent which does not appreciably attack said high-temperature polyimide layer;
etching said high-temperature polyimide layer and said first polyimide layer through said developed photoresist layer to form vias in said first polyimide layer, said high-temperature polyimide layer and said first polyimide layer etching at substantially the same rate, said photoresist layer being substantially removed during said etching step;
forming a conductor layer on said substrate, said conductor layer at least partially filling said vias formed in said first polyimide layer, said conductor layer being formed under high temperature conditions; and lifting off said high temperature polyimide layer from said first polyimide layer in order to remove undesired portions of said conductor layer.
forming a first polyimide layer on the processed substrate;
forming a high-temperature polyimide layer on said first polyimide layer;
forming a photoresist layer on said high-temperature polyimide layer;
exposing said photoresist layer and developing said photoresist layer in a solvent which does not appreciably attack said high-temperature polyimide layer;
etching said high-temperature polyimide layer and said first polyimide layer through said developed photoresist layer to form vias in said first polyimide layer, said high-temperature polyimide layer and said first polyimide layer etching at substantially the same rate, said photoresist layer being substantially removed during said etching step;
forming a conductor layer on said substrate, said conductor layer at least partially filling said vias formed in said first polyimide layer, said conductor layer being formed under high temperature conditions; and lifting off said high temperature polyimide layer from said first polyimide layer in order to remove undesired portions of said conductor layer.
2. The process as recited in Claim 1, wherein said high-temperature polyimide layer and said conductor layer have substantially the same thicknesses.
3. The process as recited in Claim 1, wherein said high-temperature polyimide layer is comprised of a polyimide material which does not fully imidize at temperatures below approximately 250°-280°C.
4. The process as recited in Claim 3, wherein prior to said step of forming said photoresist layer on said high-temperature polyimide layer, said first polyimide layer is substantially imidized without appreciably imidizing said high-temperature polyimide layer.
5. The process as recited in Claim 1, wherein said photoresist layer is developed in a solvent comprising sodium metasilicate.
6. The process as recited in Claim 1, wherein said step of etching said high-temperature polyimide layer and said first polyimide layer is carried out using reactive ion etching in an oxygen ambient.
7. The process-as recited in Claim 1, wherein said substrate is heated to a temperature below the imidization temperature of said high-temperature polyimide layer during said step of forming said conductor layer on said substrate.
8. The process as recited in Claim 1, wherein said step of lifting off said high-temperature polyimide layer is carried out using n-methyl pyrrolidone as the solvent.
9. A process of forming a patterned conductor layer on the surface of a processed semiconductor substrate having active and passive devices formed thereon and a patterned passivation layer formed on the devices, comprising the steps of:
forming a first polyimide layer on the patterned passivation layer of the processed semiconductor substrate;
forming a second polyimide layer on said first polyimide layer and heating said second polyimide layer in order to remove excess solvent therefrom, said second polyimide layer having an imidization temperature of approximately 250°-280°C;
forming a positive photoresist layer on said second polyimide layer;
exposing said positive photoresist layer and developing said positive photoresist layer in an aqueous base which does not appreciably attack said second polyimide layer;
anisotropically etching said second polyimide layer and said first polyimide layer through said developed positive photoresist so as to form vias having substantially vertical sidewalls in said first polyimide layer, said vias being aligned with openings in said patterned passivation layer, said second and first polyimide layers etching at substantially the same rate;
forming a conductor layer on the processed semiconductor substrate, said conductor layer at least partially filling said vias, the semiconductor substrate being held at a temperature of at least 200°C during formation of said conductor layer so as to minimize physical defects in said conductor layer; and removing undesired portions of said conductor layer and remaining portions of said positive photoresist layer atop said second polyimide layer by submersing the processed semiconductor substrate in a solvent which attacks said second polyimide layer without appreciably attacking said first polyimide layer.
forming a first polyimide layer on the patterned passivation layer of the processed semiconductor substrate;
forming a second polyimide layer on said first polyimide layer and heating said second polyimide layer in order to remove excess solvent therefrom, said second polyimide layer having an imidization temperature of approximately 250°-280°C;
forming a positive photoresist layer on said second polyimide layer;
exposing said positive photoresist layer and developing said positive photoresist layer in an aqueous base which does not appreciably attack said second polyimide layer;
anisotropically etching said second polyimide layer and said first polyimide layer through said developed positive photoresist so as to form vias having substantially vertical sidewalls in said first polyimide layer, said vias being aligned with openings in said patterned passivation layer, said second and first polyimide layers etching at substantially the same rate;
forming a conductor layer on the processed semiconductor substrate, said conductor layer at least partially filling said vias, the semiconductor substrate being held at a temperature of at least 200°C during formation of said conductor layer so as to minimize physical defects in said conductor layer; and removing undesired portions of said conductor layer and remaining portions of said positive photoresist layer atop said second polyimide layer by submersing the processed semiconductor substrate in a solvent which attacks said second polyimide layer without appreciably attacking said first polyimide layer.
10. The process as recited in Claim 9, wherein the patterned passivation layer comprises an insulator which can be formed at a temperature below the anneal temperature of any underlying conductors.
11. The process as recited in Claim 10, wherein said insulator is selected from the group consisting of silicon nitride, silicon dioxide, and sputtered quartz.
12. A process of forming an interconnection structure for coupling a metallization level of a processed semiconductor substrate to a conductor coupled to an external signal source, comprising the steps of forming a first polyimide layer on said metallization level of the semiconductor substrate;
forming a second polyimide layer on said first polyimide layer;
forming a layer of photoresist on said second polyimide layer;
exposing said photoresist and developing said photoresist in an aqueous base which attacks said second and first polyimide layers so as to form vias in said first polyimide layer to a selected portion of said metallization level;
heating the substrate to a temperature sufficient to substantially imidize said first polyimide layer and insubstantially imidize said second polyimide layer;
depositing a conductor layer on said second polyimide layer under high temperature conditions, said conductor layer at least partially filling said vias; and lifting off said second polyimide layer from said first polyimide layer in order to remove portions of said conductor layer lying outside said vias.
forming a second polyimide layer on said first polyimide layer;
forming a layer of photoresist on said second polyimide layer;
exposing said photoresist and developing said photoresist in an aqueous base which attacks said second and first polyimide layers so as to form vias in said first polyimide layer to a selected portion of said metallization level;
heating the substrate to a temperature sufficient to substantially imidize said first polyimide layer and insubstantially imidize said second polyimide layer;
depositing a conductor layer on said second polyimide layer under high temperature conditions, said conductor layer at least partially filling said vias; and lifting off said second polyimide layer from said first polyimide layer in order to remove portions of said conductor layer lying outside said vias.
13. The process as recited in Claim 12, wherein said aqueous base is selected from the group consisting of KOH and TMAH.
14. The process as recited in Claim 12, wherein said step of curing said first and second polyimide layers is carried out at a temperature within the range of 200°-280°C.
15. The process as recited in Claim 12, wherein said first and second polyimide layers are solidified by heating to 110°C-130°C immediately after formation.
16. The process as recited in Claim 12, wherein said second polyimide layer is lifted off said first polyimide layer by submersing said second polyimide layer in an n-methyl pyrrolidone solvent.
17. The process as recited in Claim 12, wherein said conductor layer comprises a combination of chromium, copper and gold.
18. The process as recited in Claim 12, wherein said conductor layer comprises a combination of titanium, copper and gold.
19. A method of forming wire bond contacts which connect the final metallization level of a processed semiconductor substrate to at least one external signal source, comprising the steps of:
forming a first polyimide layer on the final metallization layer;
forming a high-temperature polyimide layer on said first polyimide layer;
forming a positive photoresist layer on said high-temperature polyimide layer;
exposing said positive photoresist and developing said exposed positive photoresist in an aqueous base which attacks said high-temperature polyimide layer and said first polyimide layer to form vias in said first polyimide layer, said high-temperature polyimide layer and said first polyimide layer etching at substantially the same rate;
removing said positive photoresist layer;
heating the substrate so as to substantially imidize said first polyimide layer and insubstantially imidize said high-temperature polyimide layer;
depositing a layer of a first conductive material onto said substrate, said first conductive material at least partially filling said vias in said first polyimide layer, said substrate being heated to a temperature below the full imidization temperature of said high-temperature polyimide layer during said deposition of said conductive material;
lifting off the high-temperature polyimide layer from said first polyimide layer in order to remove portions of said conductive material lying outside said vias; and forming the wire bond contacts on remaining portions of said conductive material.
forming a first polyimide layer on the final metallization layer;
forming a high-temperature polyimide layer on said first polyimide layer;
forming a positive photoresist layer on said high-temperature polyimide layer;
exposing said positive photoresist and developing said exposed positive photoresist in an aqueous base which attacks said high-temperature polyimide layer and said first polyimide layer to form vias in said first polyimide layer, said high-temperature polyimide layer and said first polyimide layer etching at substantially the same rate;
removing said positive photoresist layer;
heating the substrate so as to substantially imidize said first polyimide layer and insubstantially imidize said high-temperature polyimide layer;
depositing a layer of a first conductive material onto said substrate, said first conductive material at least partially filling said vias in said first polyimide layer, said substrate being heated to a temperature below the full imidization temperature of said high-temperature polyimide layer during said deposition of said conductive material;
lifting off the high-temperature polyimide layer from said first polyimide layer in order to remove portions of said conductive material lying outside said vias; and forming the wire bond contacts on remaining portions of said conductive material.
20. A method of forming a solder ball contact which connects the metallization levels of the semiconductor substrate to at least one external signal source, comprising the steps of:
passivating the final metallization layer by spin-applying a first polyimide layer thereon;
spin-applying a high-temperature polyimide layer onto said first polyimide layer, said first polyimide layer being thicker than said high-temperature polyimide layer;
spin-applying a layer of positive photoresist onto said high-temperature polyimide layer;
exposing said positive photoresist and developing said exposed positive photoresist in an aqueous base which attacks said high-temperature polyimide layer and said first polyimide layer to form vias in said first polyimide layer without appreciably attacking the underlying metallization level, said high-temperature polyimide layer and said first polyimide layer etching at substantially the same rate;
removing said positive photoresist with a solvent which does not appreciably attack the underlying layers;
heating the substrate to approximately 200°C
for approximately 15-20 minutes, which is sufficient to fully imidize said first polyimide layer and insubstantially imidize said high-temperature polyimide layer;
depositing a layer of conductive material on said high-temperature polyimide layer, said substrate being heated to 200°-280°C during said deposition of said conductive material in order to minimize physical defects therein, said conductive material substantially filling said vias formed in said first polyimide layer to form a pad metallurgy in said vias;
lifting off the high temperature polyimide layer from said first polyimide layer in order to remove portions of said conductive material lying outside said vias; and depositing solder through a mask in order to form the solder ball contacts on said pad metallurgy.
passivating the final metallization layer by spin-applying a first polyimide layer thereon;
spin-applying a high-temperature polyimide layer onto said first polyimide layer, said first polyimide layer being thicker than said high-temperature polyimide layer;
spin-applying a layer of positive photoresist onto said high-temperature polyimide layer;
exposing said positive photoresist and developing said exposed positive photoresist in an aqueous base which attacks said high-temperature polyimide layer and said first polyimide layer to form vias in said first polyimide layer without appreciably attacking the underlying metallization level, said high-temperature polyimide layer and said first polyimide layer etching at substantially the same rate;
removing said positive photoresist with a solvent which does not appreciably attack the underlying layers;
heating the substrate to approximately 200°C
for approximately 15-20 minutes, which is sufficient to fully imidize said first polyimide layer and insubstantially imidize said high-temperature polyimide layer;
depositing a layer of conductive material on said high-temperature polyimide layer, said substrate being heated to 200°-280°C during said deposition of said conductive material in order to minimize physical defects therein, said conductive material substantially filling said vias formed in said first polyimide layer to form a pad metallurgy in said vias;
lifting off the high temperature polyimide layer from said first polyimide layer in order to remove portions of said conductive material lying outside said vias; and depositing solder through a mask in order to form the solder ball contacts on said pad metallurgy.
21. A method of forming a pad metallurgy which provides a conductive intermixing barrier between the metallization levels of a processed semiconductor substrate and the wire bond or solder ball contacts coupled to at least one external signal source, comprising the steps of:
passivating a final one of the metallization levels of the processed semiconductor substrate by spin coating a first polyimide layer thereon;
forming a high-temperature polyimide layer on said first polyimide layer, said high-temperature polyimide layer having a full imidization temperature within the range of 250°-280°C;
forming a positive photoresist layer on said high-temperature polyimide layer;
exposing said positive photoresist and developing said exposed positive photoresist in an aqueous base which attacks said high-temperature polyimide layer and said first polyimide layer to form aperatures in said high-temperature polyimide layer and vias through said first polyimide layer to an elongated portion of said final metallization level, said high-temperature polyimide layer and said first polyimide layer etching at substantially the same rate;
heating the substrate so as to substantially imidize said first polyimide layer and insubstantially imidize said high-temperature polyimide layer;
etching said high-temperature polyimide through said positive photoresist in order to etch back the sidewalls of said aperatures in said high-temperature polyimide layer without appreciably attacking said first polyimide layer or said final metallization level;
depositing a first layer of conductive material on said high-temperature polyimide under high temperature conditions, said first layer of conductive material at least partially overflowing said vias in said first polyimide layer to form a pad metallurgy; and lifting off the high-temperature polyimide layer from said first polyimide layer in order to remove undesired portions of said conductive material lying outside said vias.
passivating a final one of the metallization levels of the processed semiconductor substrate by spin coating a first polyimide layer thereon;
forming a high-temperature polyimide layer on said first polyimide layer, said high-temperature polyimide layer having a full imidization temperature within the range of 250°-280°C;
forming a positive photoresist layer on said high-temperature polyimide layer;
exposing said positive photoresist and developing said exposed positive photoresist in an aqueous base which attacks said high-temperature polyimide layer and said first polyimide layer to form aperatures in said high-temperature polyimide layer and vias through said first polyimide layer to an elongated portion of said final metallization level, said high-temperature polyimide layer and said first polyimide layer etching at substantially the same rate;
heating the substrate so as to substantially imidize said first polyimide layer and insubstantially imidize said high-temperature polyimide layer;
etching said high-temperature polyimide through said positive photoresist in order to etch back the sidewalls of said aperatures in said high-temperature polyimide layer without appreciably attacking said first polyimide layer or said final metallization level;
depositing a first layer of conductive material on said high-temperature polyimide under high temperature conditions, said first layer of conductive material at least partially overflowing said vias in said first polyimide layer to form a pad metallurgy; and lifting off the high-temperature polyimide layer from said first polyimide layer in order to remove undesired portions of said conductive material lying outside said vias.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/728,072 US4606998A (en) | 1985-04-30 | 1985-04-30 | Barrierless high-temperature lift-off process |
| US728,072 | 1985-04-30 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1223089A true CA1223089A (en) | 1987-06-16 |
Family
ID=24925304
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000495660A Expired CA1223089A (en) | 1985-04-30 | 1985-11-19 | Barrierless high-temperature lift-off process |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US4606998A (en) |
| EP (1) | EP0200082B1 (en) |
| JP (1) | JPS61252648A (en) |
| CA (1) | CA1223089A (en) |
| DE (1) | DE3685906T2 (en) |
Families Citing this family (42)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| IT1184535B (en) * | 1985-05-03 | 1987-10-28 | Gte Telecom Spa | THIN FILM LINES RECOVERY PROCESS |
| US4828964A (en) * | 1985-08-20 | 1989-05-09 | International Business Machines Corporation | Polyimide formulation for forming a patterned film on a substrate |
| US4890157A (en) * | 1986-01-31 | 1989-12-26 | Texas Instruments Incorporated | Integrated circuit product having a polyimide film interconnection structure |
| ZA87922B (en) * | 1986-02-28 | 1987-09-30 | Macdermid Inc | Photoresist stripper composition |
| US4943471A (en) * | 1986-05-20 | 1990-07-24 | Kanegafuchi Kagaku Kogyo Kabushiki Kaisha | Patterned thin film and process for preparing the same |
| US4886573A (en) * | 1986-08-27 | 1989-12-12 | Hitachi, Ltd. | Process for forming wiring on substrate |
| GB2212979A (en) * | 1987-12-02 | 1989-08-02 | Philips Nv | Fabricating electrical connections,particularly in integrated circuit manufacture |
| US4846929A (en) * | 1988-07-13 | 1989-07-11 | Ibm Corporation | Wet etching of thermally or chemically cured polyimide |
| GB2226991A (en) * | 1989-01-13 | 1990-07-18 | Ibm | Etching organic polymeric materials |
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| CN102157494B (en) | 2005-07-22 | 2013-05-01 | 米辑电子股份有限公司 | Wiring assembly |
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| US20070036890A1 (en) * | 2005-08-12 | 2007-02-15 | Feng Zhong | Method of making a fuel cell component using a mask |
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| US7862987B2 (en) * | 2007-11-20 | 2011-01-04 | International Business Machines Corporation | Method for forming an electrical structure comprising multiple photosensitive materials |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3985597A (en) * | 1975-05-01 | 1976-10-12 | International Business Machines Corporation | Process for forming passivated metal interconnection system with a planar surface |
| JPS55163860A (en) * | 1979-06-06 | 1980-12-20 | Toshiba Corp | Manufacture of semiconductor device |
| US4377115A (en) * | 1979-12-21 | 1983-03-22 | Kolze Bruce A | Furnace for burning particulate wood waste material |
| US4353778A (en) * | 1981-09-04 | 1982-10-12 | International Business Machines Corporation | Method of etching polyimide |
| US4451971A (en) * | 1982-08-02 | 1984-06-05 | Fairchild Camera And Instrument Corporation | Lift-off wafer processing |
| US4428796A (en) * | 1982-08-02 | 1984-01-31 | Fairchild Camera And Instrument Corporation | Adhesion bond-breaking of lift-off regions on semiconductor structures |
| JPS6018923A (en) * | 1983-07-13 | 1985-01-31 | Hitachi Ltd | Taper etching of polyimide resin layer |
| US4523976A (en) * | 1984-07-02 | 1985-06-18 | Motorola, Inc. | Method for forming semiconductor devices |
| US4624740A (en) * | 1985-01-22 | 1986-11-25 | International Business Machines Corporation | Tailoring of via-hole sidewall slope |
-
1985
- 1985-04-30 US US06/728,072 patent/US4606998A/en not_active Expired - Lifetime
- 1985-11-19 CA CA000495660A patent/CA1223089A/en not_active Expired
-
1986
- 1986-01-29 JP JP61015985A patent/JPS61252648A/en active Pending
- 1986-04-15 EP EP86105142A patent/EP0200082B1/en not_active Expired
- 1986-04-15 DE DE8686105142T patent/DE3685906T2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| EP0200082B1 (en) | 1992-07-08 |
| DE3685906D1 (en) | 1992-08-13 |
| EP0200082A3 (en) | 1988-11-17 |
| DE3685906T2 (en) | 1993-02-04 |
| US4606998A (en) | 1986-08-19 |
| EP0200082A2 (en) | 1986-11-05 |
| JPS61252648A (en) | 1986-11-10 |
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