CN101905858A - Method for preventing MEMS (Micro-Electromechanical System) device structural layer material from being electrochemically corroded - Google Patents
Method for preventing MEMS (Micro-Electromechanical System) device structural layer material from being electrochemically corroded Download PDFInfo
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- CN101905858A CN101905858A CN 201010235870 CN201010235870A CN101905858A CN 101905858 A CN101905858 A CN 101905858A CN 201010235870 CN201010235870 CN 201010235870 CN 201010235870 A CN201010235870 A CN 201010235870A CN 101905858 A CN101905858 A CN 101905858A
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Abstract
The invention discloses a method for preventing an MEMS (Micro-Electromechanical System) device structural layer material from being electrochemically corroded. The method comprises the following steps of: further settling a metal Ti layer on the surface of a precious metal layer in a metallization process of an MEMS device; and then covering the metal Ti layer by photoresist. Because the electrochemical potential of metal Ti in HF base corrosive liquid is lower than that of a structural layer semiconductor material, Ti instead of the semiconductor material forms a primary battery with the precious metal layer and is used as an anode of the primary battery for carrying out oxidation reaction in the HF base corrosive liquid, thereby effectively preventing the semiconductor structural layer material from being electrochemically corroded and ensuring the firm combination of the metal layer and other structural layers.
Description
Technical field
The present invention relates to MEMS device manufacturing technology field, relate in particular to the method that a kind of MEMS of preventing device architecture layer material is etched electrochemically, prevent that promptly structural material with the MEMS device of noble metal is at SiO
2The method that is etched electrochemically in the wet etching course.
Background technology
From the eighties in last century MEMS (Micro Electromechanical System, MEMS) technology flourish since, the market value of various MEMS devices rises rapidly.Micro-acceleration gauge from safe automobile air bag, the micropressure sensor in the tire, the gyroscope in the navigator, the micro-resonator in the wireless telecommunication system again, the micro-switch array in wave filter and the radar.These MEMS devices have promoted development of technology, have improved people's quality of the life.
The processing of MEMS device is the micromachined technology of utilizing same microelectronic integrated circuit (IC) manufacturing technology compatible mutually.Common MEMS device is a kind of sandwich construction, mainly comprises structure sheaf, sacrifice layer and metal level.The MEMS device is generally by semi-conducting material, as the polysilicon of low pressure gas phase deposition (LPCVD) or single crystal silicon material etc., as the device architecture layer, and select for use silica as device isolation layer or sacrifice layer, be widely used in IC technology mainly due to silica, can stand high temperature processes such as thin-film deposition and annealing, and in HF base corrosive liquid, corrosion rate faster be arranged, and some materials such as silicon, silicon nitride there is higher selectivity relatively.Sacrifice layer SiO
2The course of reaction that takes place in HF base corrosive liquid is: SiO
2+ 6HF → H
2SiF
6+ 2H
2O.
Because MEMS device function demand often needs precious metal material as structure sheaf, electricity connecting line layer and bond pad etc.Yet, this MEMS device that has noble metal is being carried out SiO with HF base corrosive liquid
2Wet etching the time, tend to the semiconductor structure layer material is produced serious electrochemical corrosion, the electric property and the mechanical performance of device are obviously worsened, as, the resistivity of structural material enlarges markedly, Young's modulus reduces, and mechanical strength descends and material internal stress gradient rising etc., thereby has reduced the yield rate and the reliability of MEMS device.
This class electrochemical corrosion is because the standard electric chemical potential of precious metal material is higher than the electrochemical potential of semiconductor structure layer material, in HF base corrosive liquid, the noble metal that links to each other constitutes galvanic cell with semi-conducting material, as the structural material of galvanic cell positive pole generation oxidation reaction and being corroded in HF base corrosive liquid.With the polysilicon structure layer is example, and the electrochemical corrosion reaction of its generation is:
Si+2HF+λh
+→SiF
2+2H
++(2-λ)e
-
SiF
2+2HF→SiF
4+H
2
SiF
4+2HF→H
2SiF
6
Wherein, h
+Be the valence band hole that noble metal provides, λ is the hole number of required participation reaction.Its product H
2SiF
6Water-soluble, cause the polysilicon structure laminar surface of MEMS device can form porous silicon.If release solution is dense hydrofluoric acid or the pure hydrofluoric acid of gaseous state more than 40%, also following reaction can take place:
Si+2H
2O+4h
+→SiO
2+4H
+
SiO
2+6HF→SiF
6 2-+2H
2O+2H
+
In addition, because structural material is corroded, layering also can take place in metal layer material attached to it, even peels off.Therefore, for yield rate and the reliability that improves device, explore at SiO
2The method of effectively avoiding structural material to be corroded in the wet corrosion technique is very important.
At present, avoid MEMS device architecture layer material at SiO
2Wet etching course in the method that is etched electrochemically roughly be divided into two classes.One class is by changing device architecture, as punching, shorten SiO on the device architecture layer
2The etching time of layer in HF base corrosive liquid perhaps reduces the area ratio that layer of precious metal is occupied in device architecture, weaken the attack of electrochemical corrosion to semiconductor structure layer.These class methods can alleviate the corrosion of HF base corrosive liquid to the semiconductor structure layer material, but effect is limited, and therefore finally cause device performance to change to the change that device architecture is done, so the scope of application of these class methods is very limited.Another kind of method is that to utilize additional circuit to change the electrochemical potential of structure sheaf semi-conducting material and layer of precious metal material poor, or by add redox buffer in corrosive liquid, slows down the electrochemical corrosion to structural material.These class methods can effectively be alleviated the influence of electrochemical corrosion, but complex process, cost height, are not suitable for the extensive manufacturing of MEMS device.
Summary of the invention
(1) technical problem that will solve
A key technical problem that faces at many MEMS device making technics midium or long terms, be of the electrochemical corrosion of HF base corrosive liquid to the semiconductor structure layer material, the method that provides a kind of MEMS of preventing device architecture layer material to be etched electrochemically is provided main purpose of the present invention, to prevent that MEMS device architecture layer material with noble metal is at SiO
2In the wet etching course by the electrochemical corrosion of HF base corrosive liquid.
(2) technical scheme
For achieving the above object, the invention provides the method that a kind of MEMS of preventing device architecture layer material is etched electrochemically, this method is in the metallization process of MEMS device, at the further deposit layer of metal Ti layer in layer of precious metal surface, covers this metal Ti layer then with photoresist.
In the such scheme, described metal Ti layer is finished in same single metal metallization processes with described layer of precious metal, and is positioned at described layer of precious metal surface.
In the such scheme, the thickness of described metal Ti layer is by SiO
2The length of wet etching time and structure sheaf and the noble metal exposed area in corrosive liquid is than decision, SiO
2The wet etching time is long more, and perhaps noble metal is bigger than more with the structure sheaf area, and required metal Ti layer is just thick more.
In the such scheme, this method realizes the covering protection of photoresist to whole metal Ti layer by photoetching.
In the such scheme, this method adopts photoetching to define etch pit, makes HF base corrosive liquid by the direct contact corrosion SiO of etch pit
2Layer.
In the such scheme, this method is to SiO
2Wet etching further comprises after finishing: remove the metal Ti layer that photoresist and precious metal surface are not exhausted by HF base corrosive liquid, obtain protected device architecture.
(3) beneficial effect
From technique scheme as can be seen, the present invention has following beneficial effect:
1, utilizes the present invention, because the electrochemical potential of metal Ti in HF base corrosive liquid is lower than the electrochemical potential of structure sheaf semi-conducting material, thereby Ti alternative semiconductors material, constitute galvanic cell with layer of precious metal, and in HF base corrosive liquid oxidation reaction takes place as the galvanic cell positive pole, thereby effectively avoided the semiconductor structure layer material to be etched electrochemically, and guaranteed the strong bonded of metal level and other structure sheaf.
2, utilize the present invention, need not increases complex process steps in the manufacturing process of MEMS device, just can effectively avoid at SiO
2Wet etching course in, the semiconductor structure layer material is etched electrochemically, and guarantees that device performance is not affected.This method can be used for SiO
2Long-time wet etching (1～2 hour), not only simple and reliable, and with the IC process compatible, can be extended to the step routine techniques of MEMS devices in batches in producing.This method need not original device architecture is carried out any change, and process implementing is simple, cost is low, is applicable to the batch making of device.
Description of drawings
Fig. 1 is the SiO that does not have MEMS device under the situation that layer of precious metal exists
2The schematic diagram of layer wet etching;
Fig. 2 has under the situation of layer of precious metal existence, and structure sheaf (as polysilicon) is at SiO
2Corrosion mechanism schematic diagram in the wet corrosion technique;
Fig. 3 is that the MEMS of avoiding device architecture layer provided by the invention is at SiO
2The method schematic diagram that is corroded in the wet corrosion technique;
Fig. 4 is at no metal level, layer of precious metal is arranged and has under the Ti protective layer condition, and the polysilicon structure layer is at SiO in the MEMS device
2The relation of resistivity and etching time in the wet corrosion technique;
Fig. 5 be in the MEMS device of band different-thickness Ti protective layer the polysilicon structure layer at SiO
2The variation relation of resistivity and etching time in the wet corrosion technique;
Among the figure: 1. structure sheaf (as polysilicon), 2.SiO
2Layer, 3. layer of precious metal (as Au, Pt), 4. metal Ti protective layer, 5. photoresist cover layer, 6. etch pit, 7. separation layer is (as SiN
x), 8. substrate (as silicon chip, quartz glass plate etc.).
The specific embodiment
For making the purpose, technical solutions and advantages of the present invention clearer, below in conjunction with specific embodiment, and with reference to accompanying drawing, the present invention is described in more detail.
This protection MEMS device architecture layer material provided by the invention is at SiO
2The method that is not etched electrochemically in the wet corrosion technique is in the metallization process of device, at layer of precious metal surface deposition layer of metal Ti layer, covers whole metal level then with photoresist.Because the electrochemical potential of metal Ti layer in HF base corrosive liquid is lower than the electrochemical potential of structure sheaf semi-conducting material, thereby Ti alternative semiconductors material, constitute galvanic cell with layer of precious metal, and in HF base corrosive liquid oxidation reaction takes place as the galvanic cell positive pole, thereby effectively avoided the semiconductor structure layer material to be etched electrochemically, and guaranteed the strong bonded of metal level and other structure sheaf.
In the metallization process of MEMS device, at the layer of precious metal surface deposition layer of metal Ti of required deposit layer, the metal Ti layer is finished in same single metal metallization processes with other layer of precious metal.By standard photolithography process (drying by the fire behind baking before gluing, the isothermal, exposure, development, the isothermal), realize the covering protection of photoresist then to whole metal level; And the etch pit by lithographic definition, make HF base corrosive liquid directly corrode SiO
2Layer.
According to SiO
2The length of wet etching time, and structure sheaf and the exposed area ratio of noble metal in corrosive liquid can be made the metal Ti layer of different-thickness.Crossing thin T i layer can be depleted in long-time wet etching course, can not prevent effectively that the semiconductor structure layer material from being attacked by electrochemistry; Blocked up Ti layer can increase the manufacturing cost of device.
The metal Ti layer is very easily oxidized generation 3 valency ion titanium Ti in HF base corrosive liquid
3+:
2Ti+6HF→2TiF
3+3H
2。
In the method disclosed in the present, HF base corrosive liquid penetrates photoresist and Ti reacts, the Ti of generation
3+Being free in photoresist and layer of precious metal surrounds in the zonule that forms.Because Ti
3+To Ti
4+Electrochemical potential be lower than the electrochemical potential of semiconductor structure layer material, Ti
3+Preferential and noble metal constitutes the galvanic cell circuit in HF base corrosive liquid.Ti
3+Contribute an electronics to give and be oxidized to Ti at the cation of galvanic cell negative pole generation reduction reaction
4+:
TiF
3+3HF+λh
+→H
2TiF
6+H
++(1-λ)e
-。
Because electrochemical reaction has taken place in metal Ti layer alternative structure layer material in HF base corrosive liquid, thereby has effectively avoided structural material to be etched electrochemically.
If there is not photoresist layer, following reaction can directly take place in Ti:
Ti+6HF→TiF
6 2-+2H
++2H
2
Ti+2H
2O→TiO
2+4H
++4e
-
TiO
2+6HF→TiF
6 2-+2H
++2H
2O
Its product TiF
6 2-Water-soluble, too fast the exhausting of metal Ti layer meeting can not be protected the semiconductor structure layer material.
Be example to contain polysilicon structure layer MEMS device architecture below, the present invention is described in more detail.
Fig. 1 is not for the MEMS device of metal level wet etching SiO in HF base corrosive liquid
2Schematic diagram.Wherein, SiO
2Layer has corrosion rate faster in HF base corrosive liquid, its course of reaction is:
SiO
2+6HF→H
2SiF
6+2H
2O
Its product H
2SiF
6Water-soluble, so SiO
2Layer is corroded.And compared to SiO
2Layer 2, polysilicon structure layer 1 is extremely slow with the HF reaction, can not cause excessive influence to device performance usually.
In Fig. 2, the MEMS device surface has layer of precious metal 3, and it links to each other with polysilicon structure layer 1.Because the standard electric chemical potential of precious metal material 3 is higher than the electrochemical potential of polysilicon structure layer 1 in HF base corrosive liquid, therefore in HF base corrosive liquid, the noble metal 3 that links to each other constitutes galvanic cell with polysilicon structure layer 1, in HF base corrosive liquid oxidation reaction takes place and is corroded as the polysilicon structure layer 1 of galvanic cell positive pole.Its reaction equation is:
Si+2HF+λh
+→SiF
2+2H
++(2-λ)e
-
SiF
2+2HF→SiF
4+H
2
SiF
4+2HF→H
2SiF
6
Its product H
2SiF
6Water-soluble, polysilicon structure layer 1 is corroded, and generates porous silicon, causes making device performance to reduce even inefficacy.
Among Fig. 3, when implementing the metallization process of MEMS device, at the layer of precious metal 3 surface deposition layer of metal Ti layers 4 of required deposit, metal Ti layer 4 is finished in same single metal metallization processes with other layer of precious metal 3.Photoetching process by standard then: dry by the fire behind baking before gluing, the isothermal, exposure, development, the isothermal, cover metal Ti layers 4 with AZ6130 photoresist cover layer 5.On photoresist cover layer 5, define etch pit 6 by photoetching again.Can make HF base corrosive liquid directly contact SiO by this etch pit 6
2Layer 2 makes SiO
2Wet etching unaffected.Because metal Ti layer 4 is very easily penetrated the HF base corrosive liquid of photoresist cover layer 5 and is oxidized to 3 valency ion titanium Ti
3+, and be free in the Ti that photoresist cover layer 5 and layer of precious metal 3 surround the zonule that forms
3+, the electrochemical potential in HF base corrosive liquid is lower than the electrochemical potential of polysilicon structure layer 1, therefore substitutes polysilicon structure layer 1 and constitutes galvanic cell and oxidized corrosion with noble metal 3, thereby effectively avoided polysilicon structure layer 1 to be etched electrochemically.Because the protection of photoresist cover layer 5 is arranged, can not cause the too fast dissipation of metal Ti layer 4, can protect polysilicon structure layer 1 not to be etched electrochemically for a long time.
As can be seen from Figure 4, for the MEMS device of the band layer of precious metal 3 that does not carry out any safeguard measure, the resistivity of its polysilicon structure layer 1 is along with SiO
2The prolongation of layer 2 etching time and enlarging markedly, in the resistivity of corrosion polysilicon structure layer 1 after 30 minutes greater than 1000 Ω cm; And for not with the MEMS device of noble metal and the MEMS device that the band layer of precious metal 3 of metal Ti layer 4 is arranged, the resistivity of its polysilicon structure layer 1 was at 60 minutes SiO
2Significant change does not take place in the wet etching course.
As shown in Figure 5, metal Ti layer 4 is consumed in the process of protection MEMS device polysilicon structure sheaf 1.SiO
2The wet etching time of layer 2 is long more, i.e. the time of polysilicon structure layer 1 required protection is long more, and the metal Ti layer 4 that needs is thick more.Therefore according to SiO
2The length of 2 wet etching time of layer, and polysilicon structure layer 1 and the exposed area ratio of noble metal 3 in corrosive liquid can be made the metal Ti layer 4 of different-thickness.Crossing thin metal Ti layer 4 can be depleted in long-time wet etching course, can not prevent fully that polysilicon structure layer 1 is etched electrochemically; Blocked up metal Ti layer 4 can increase the manufacturing cost of device.
SiO
2After the wet etching of layer 2 finishes, need to remove photoresist, and remove the metal Ti layer 4 that noble metal 3 surfaces are not exhausted by HF base corrosive liquid, obtain protected device architecture.
Above-described specific embodiment; purpose of the present invention, technical scheme and beneficial effect are further described; institute is understood that; the above only is specific embodiments of the invention; be not limited to the present invention; within the spirit and principles in the present invention all, any modification of being made, be equal to replacement, improvement etc., all should be included within protection scope of the present invention.
Claims (6)
1. a method that prevents that MEMS device architecture layer material is etched electrochemically is characterized in that, this method is in the metallization process of MEMS device, at the further deposit layer of metal Ti layer in layer of precious metal surface, covers this metal Ti layer then with photoresist.
2. the method that the MEMS of preventing device architecture layer material according to claim 1 is etched electrochemically is characterized in that described metal Ti layer is finished in same single metal metallization processes with described layer of precious metal, and is positioned at described layer of precious metal surface.
3. the method that the MEMS of preventing device architecture layer material according to claim 1 is etched electrochemically is characterized in that the thickness of described metal Ti layer is by SiO
2The length of wet etching time and structure sheaf and the noble metal exposed area in corrosive liquid is than decision, SiO
2The wet etching time is long more, and perhaps noble metal is bigger than more with the structure sheaf area, and required metal Ti layer is just thick more.
4. the method that the MEMS of preventing device architecture layer material according to claim 1 is etched electrochemically is characterized in that, this method realizes the covering protection of photoresist to whole metal Ti layer by photoetching.
5. the method that the MEMS of preventing device architecture layer material according to claim 1 is etched electrochemically is characterized in that, this method adopts photoetching to define etch pit, makes HF base corrosive liquid by the direct contact corrosion SiO of etch pit
2Layer.
6. the method that the MEMS of preventing device architecture layer material according to claim 1 is etched electrochemically is characterized in that, this method is to SiO
2Wet etching further comprises after finishing: remove the metal Ti layer that photoresist and precious metal surface are not exhausted by HF base corrosive liquid, obtain protected device architecture.
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|---|---|---|---|
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|---|---|---|---|
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| CN101905858B CN101905858B (en) | 2012-07-25 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115231511A (en) * | 2021-12-03 | 2022-10-25 | 绍兴中芯集成电路制造股份有限公司 | Device processing method, MEMS device and processing method thereof, and MEMS microphone |
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| CN1327086A (en) * | 2001-05-18 | 2001-12-19 | 北京大学 | Silicon etching liquid and its preparing method |
| CN1581448A (en) * | 2004-05-17 | 2005-02-16 | 西安交通大学 | Sealing method for protecting metal connecting line of micro mechanical device in corrosion process |
| US7094696B2 (en) * | 2002-02-21 | 2006-08-22 | Optical Etc Inc. | Method for TMAH etching of CMOS integrated circuits |
| CN100509611C (en) * | 2007-05-15 | 2009-07-08 | 东南大学 | Microelectron mechanical system obverse structure releasing protecting method |
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2010
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5726480A (en) * | 1995-01-27 | 1998-03-10 | The Regents Of The University Of California | Etchants for use in micromachining of CMOS Microaccelerometers and microelectromechanical devices and method of making the same |
| CN1327086A (en) * | 2001-05-18 | 2001-12-19 | 北京大学 | Silicon etching liquid and its preparing method |
| US7094696B2 (en) * | 2002-02-21 | 2006-08-22 | Optical Etc Inc. | Method for TMAH etching of CMOS integrated circuits |
| CN1581448A (en) * | 2004-05-17 | 2005-02-16 | 西安交通大学 | Sealing method for protecting metal connecting line of micro mechanical device in corrosion process |
| CN100509611C (en) * | 2007-05-15 | 2009-07-08 | 东南大学 | Microelectron mechanical system obverse structure releasing protecting method |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115231511A (en) * | 2021-12-03 | 2022-10-25 | 绍兴中芯集成电路制造股份有限公司 | Device processing method, MEMS device and processing method thereof, and MEMS microphone |
| CN115231511B (en) * | 2021-12-03 | 2023-02-03 | 绍兴中芯集成电路制造股份有限公司 | Device processing method, MEMS device and processing method thereof, and MEMS microphone |
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