WO2001044536A2

WO2001044536A2 - Sputtering targets and method of making same

Info

Publication number: WO2001044536A2
Application number: PCT/US2000/033997
Authority: WO
Inventors: Vladimir Segal; Stephane Ferrasse; William B. Willett
Original assignee: Honeywell International Inc.
Priority date: 1999-12-16
Filing date: 2000-12-15
Publication date: 2001-06-21
Also published as: EP1242645A2; US6878250B1; US20090020192A1; KR20020074171A; TW583327B; CN1592797A; US20020000272A1; WO2001044536A3; US6723187B2; US20100059147A9; HK1050032A1; US7767043B2; JP2003517101A; US20010054457A1; AU2103001A; US20020007880A1

Abstract

Described is a high quality sputtering target and method of manufacture which involves application of equal channel angular extrusion.

Description

DESCRIPTION

HIGH-STRENGTH SPUTTERING TARGETS AND METHOD OF MAKING

SAME

Technical Field

The invention relates to sputtering targets and methods of making same; and to sputtering targets of high purity metals and alloys.

Background Art

The invention relates to sputtering targets and methods of making same; and to sputtering targets of high purity metals and alloys Among these metals are Al, Ti, Cu, Ta, Ni, Mo, Au, Ag, Pt and alloys thereof, including alloys with these and or other elements. Sputtering targets may be used in electronics and semiconductor industries for deposition of thm films. To provide high resolution of thm films, uniform and step coverages, effective sputtering rate and other requirements, targets should have homogenous composition, fine and uniform structure, controllable texture and be free from precipitates, particles and other inclusions. Also, they should have high strength and simple recycling. Therefore, significant improvements are desired in the metallurgy of targets especially of large size targets.

A special deformation technique known as equal channel angular extrusion (ECAE) descπbed in U.S. Patents Nos. 5,400,633; 5,513,512; 5,600,989; and Patent No. 5,590,389 is used with advantage in accordance with the invention. The disclosures of the aforementioned patents are expressly incorporated herein by reference.

Disclosure of the Invention

The invention relates to a sputtering target made by a process including casting. The target has a target surface such that the surface of the target subjected to sputtering (referred to as target surface) has a substantially homogeneous composition at any location, substantial absence of pores, voids, inclusions and other casting defects, gram size less than about 1 m and substantially uniform structure and texture at any location. Preferably, the target comprises at least one of Al, Ti, Cu, Ta, Ni, Mo, Au, Ag, Pt and alloys thereof.

The invention also relates to a method of manufactuπng a target, as descπbed above. The method comprises fabricating an article suitable for use as a sputtering target comprising the steps of: a. providing a cast ingot; b. homogenizing said mgot at time and temperature sufficient for redistribution of macrosegregations and microsegregations; and c. subjecting said mgot to equal channel angular extrusion to re fine grams therein More particularly, a method of making a sputtering target comprising the steps of a. providing a cast mgot with a length-to-diameter ratio up to 2; b. hot forging said mgot with reductions and to a thickness sufficient for healing and full elimination of case defects; c subjecting said hot forged product to equal channel extrusion; and d. manufacturing into a sputtering target.

Still more particularly, a method of fabricating an article suitable for use as a sputtering target comprising the steps of: a. providing a cast mgot; b. solutiomzmg heat treating said cast mgot at temperature and time necessary to dissolve all precipitates and particle beaπng phases; and c. Equal channel angular extruding at temperature below agmg temperatures.

After fabπcating as described to produce an article, it may be manufactured into a sputtering target.

Brief Description of the Drawings

Preferred embodiments of the invention are described below with reference to the following accompanying drawings. FIGS. 1A-1D are schematic diagrams showing processing steps of billet preparation for ECAE;

FIG. 2 is a graph showing the effect of annealing temperature on billet strength after 4 and 6 passes of ECAE for Al 0.5 wt.% Cu alloy;

FIG. 3A is a schematic diagram disclosing an apparatus for gradient annealing of targets;

FIG. 3B is a schematic diagram showing temperature distribution through target cross-section C-C during gradient annealing;

FIG. 4 is an illustration of (200) pole figures for Al 0.5 wt.% Cu alloys processed with 2, 4 and 8 passes of route D, (in FIG. 5) respectively; FIG 5 is a graph showing the effect of number of passes and route on texture intensity after ECAE of Al w ith 0.5 wt.% Cu;

FIG 6 is a graph showing the effects of annealing temperature for route A after ECAE of Al with 0.5 wt.% Cu. FIG. 7 is a graph showing the effects of annealing temperature on texture intensity for route B after ECAE of Al with 0.5 wt.% Cu,

FIG. 8 is a graph showing the effects of annealing temperature on texture intensity for route C after ECAE of Al with 0.5 wt.% Cu,

FIG. 9 is a graph showing the effects of annealing temperature on texture intensity for route D after ECAE of Al with 0.5 wt.% Cu:

FIG. 10 is a pole figure illustrating the texture as a result of the process described; and

FIGS 1 1, 11A and 1 IB are schematic diagrams of an apparatus for ECAE of billets for targets.

Best Modes for Carrying Out the Invention

The invention contemplates a sputtering target having the following characteristics:

- substantially homogenous material composition at any location; - substantial absence of pores, voids, inclusions and other casting defects;

- substantial absence of precipitates;

- grain size less than about 1 μm;

- fine stable structure for sputtering applications;

- substantially uniform structure and texture at any location; - high strength targets without a backing plate;

- controllable textures from strong to middle, weak and close to random;

- controllable combination of gram size and texture;

- large monolithic target size;

- prolonged sputtering target life; - optimal gradient of structures through target thickness.

Targets possessing these characteπstics are producible by the processes described.

Because of high puπty, cast mgot metallurgy is useful m most cases for billet fabπcation in target production. However, casting results in a very coarse dendπtic structure with strong non-uniformity in the distribution of constitutive elements and additions across the mgot and large crystallites. Moreover, high temperature and longtime homogenizing cannot be applied in current processing methods because of the further increase of grains One embodiment of the invention solves this problem by using homogenizing time and temperature sufficient for redistπbution of macrosegregations and microsegregations followed by equal channel angular extrusion (ECAE) with a sufficient number of passes, preferably from 4 to 6, for gram refinement. Another embodiment eliminates other casting defects such as voids, porosity, cavities and inclusions which cannot be optimally removed by homogenizing and employs a hot forging operation. In currently known methods hot forging has a restricted application because reductions are limited and are typically used at low temperature working for grain refinement. Other processes do not solve that problem when slab mgots of the same thickness as the billet for ECAE are used. In the present invention, the as-cast mgot has a large length-to-diameter ratio, preferably up to 2. During hot forging, the mgot thickness changes to the thickness of the billet for ECAE. That provides large reductions which are sufficient for full healing and elimination of cast defects.

Still another embodiment of the invention is directed to precipitate- and particle-free targets. With currently known methods precipitate-free material may be prepared by solutionizing at the last processing step. However, m this case heating to solutionizing temperatures produces very large grains. The present invention provides a method for fabricating precipitate-free and ultra-fine grained targets. According to this embodiment of the invention, solutionizing is performed at a temperature and time necessary to dissolve all precipitates and particle beaπng phases and is followed by quenching immediately before ECAE. Subsequent ECAE and annealing are performed at temperatures below agmg temperatures for corresponding material conditions.

A further embodiment of the invention is a special sequence of homogenizing, forging and solutionizing operations. As-cast mgots are heated and soaked at the temperature and for the length of time necessary for homogenizing, then cooled to the starting forging temperature, then forged to the final thickness at the final forging temperature (which is above the solutionizing temperature) and quenched from this temperature. By this embodiment all processing steps are performed with one heating. This embodiment also includes another combination of processing steps without homogenizing: forging at a temperature of about the solutionizing temperature and quenching immediately after forging. It is also possible in accordance with the invention to conduct agmg after solutionizing at the temperature and for the length of time necessary to produce fine precipitates with an average diameter of less than 0.5 μm These precipitates will promote the development of fine and uniform grains duπng following steps of ECAE. An additional embodiment of the invention is a billet for ECAE after forging.

An as-cast cylindrical ingot of diameter do and length ho (FIG 1A) is forged into a disk of diameter D and thickness H (FIG. IB). The thickness H corresponds to the thickness of the billet for ECAE. Then two segments are removed from two opposite sides of the forged billet such as by machining or sawing (FIG. 1C), to provide a dimension A corresponding to a square billet for ECAE (FIG. ID). ECAE is performed m direction "C" shown on FIG. lC. After the first pass the billet has a near-square shape if the dimensions of the ECAE billet (AxAxH), the dimensions of the forged disk (DxH) and the dimensions of the cast ingot (doxho)are related by the following formulae:

DA .18A d₀ ²h₀=1.39.A²H

The invention further contemplates the fabπcation of targets with fine and uniform gra structure. ECAE is performed at a temperature below the temperature of static recrystalhzation with the number of passes and processing route adjusted to provide dynamic recrystalhzation during ECAE. Processing temperature and speed are, correspondingly, sufficiently high and sufficiently low to provide macro- and micro-uniform plastic flow.

A method for fabricating fine and stable gram structures for sputtering applications and to provide high strength targets is also provided. The billet after ECAE with dynamically recrystallized sub-micron structure is additionally annealed at the temperature which is equal to the temperature of the target surface during steady sputteπng. Therefore, the temperature of the target cannot exceed this sputtering temperature and for structure to remain stable duπng target life. That structure is the finest presently possible stable structure and provides the best target performance. It also provides a high strength target. FIG. 2 shows the effect of the annealing temperature on the ultimate tensile strength and yield stress of Al 0.5 wt.% Cu alloy after ECAE at room temperature with 6 or 4 passes. In both cases as-processed mateπal has high strength not attainable for that material with known methods. Yield stress is only slightly lower than ultimate tensile strength. The increase of the annealing temperature in a range from 125°C to 175°C that, it is believed, corresponds to possible variations of sputteπng temperature results in the gradual decrease of strength. However, even in the worst case with an annealing temperature of 175°C target strength and, especially, yield stress are much higher than the strength of aluminum alloy AA6061 at T-O condition which is the most widely used for fabπcation of backing plates (see FIG. 2). Thus, among other things, the invention provides the following significant advantages:

- High strength monolithic targets may be fabπcated from mild materials like pure aluminum, copper, gold, platinum, nickel, titanium and their alloys.

- It is not necessary to use backing plates with additional and complicated operations such as diffusion bonding or soldeπng. - Fabrication of large targets is not a problem.

- Targets may easily be recycled after their sputteπng life ends.

It is also useful to employ gradient annealing of targets after ECAE. For that purpose a preliminary machined target is exposed to the same thermal conditions as under sputtering conditions and kept at those conditions a sufficient time for annealing. FIG. 3 descπbes that processing. The target 1 is fixed in a device 2 which simulates sputteπng: a bottom surface A of the target is cooled by water while a top surface B is heated to the sputteπng temperature. Heating is advantageously developed at the thin surface layer by radiant energy q (left side of FIG. 3 A) or inductor 3 (πght side of FIG. 3A) In addition it is also possible to achieve gradient annealing of targets directly in a sputtering machine at the regular sputteπng conditions before starting the production run. In all these cases distribution of temperature through the target as shown in FIG. 3B through sections C-C of FIG. 1 is non-uniform and annealing takes place only inside a very thin surface layer (δ). Following sputtering the same distribution is maintained automatically. Thus, structural stability and high strength of as-processed material are conserved for the mam part of the target.

An additional embodiment comprises a two-step ECAE processing. At the first step ECAE is performed with a low number of passes, preferably from 1 to 3, in different directions. Then, the preliminary processed billet receives agmg annealing at low enough temperatures but for sufficient time to produce very fine precipitates of average diameter less than about 0.1 μm. After intermediate annealing ECAE is repeated with the number of passes necessary to develop a dynamically recrystallized structure with the desired fine and equiaxed grains.

It is also possible through use of the invention to control texture. Depending on the starting texture and the nature of the mateπals, various textures can be created. Four major parameters are important to obtain controlled textures: Parameter 1 : the number of repeated ECAE passes subjected to the same work piece This number determines the amount of plastic deformation introduced at each pass. Varying the tool angle between the two channels of the ECAE equipment enables the amount of plastic straining to be controlled and determined and therefore represents an additional opportunity for producing specific textures. Practically, m most cases, a tool angle of about 90° is used since an optimal deformation (true shear strain ε = 1.17) can be attained;

Parameter 2: the ECAE deformation route; that is defined by the way the work piece is introduced through the die at each pass. Depending on the

ECAE route only a selected small number of shear planes and directions are acting at each pass duπng plastic straining.

Parameter 3: annealing treatment that comprises heating the work piece under different conditions of time and temperature. Both post-deformation annealing at the end of the ECAE extrusion and intermediate annealing between selected ECAE passes are effective ways to create various textures. Annealing causes the activation of different metallurgical and physical mechanisms such as second-phase particle growth and coalescence, recovery and static recrystalhzation, which all affect more or less markedly the microstructure and texture of materials. Annealing can also create precipitates or at least change the number and size of those already present m the mateπal: this is an additional way to control textures.

Parameter 4: the oπginal texture of the considered mateπal. Parameter 5: the number, size and overall distπbution of second-phase particles present inside the mateπal. With consideration of these five major parameters, control of texture is possible in the ways descπbed below:

Table 1 describes major components of texture between 1 and 8 ECAE passes via routes A through D in the as-deformed condition for a strong initial texture and also for routes A and D for a weak initial texture. To describe major components both the 3 Euler angles (αβγ) according to the Roe/Matthies convention and ideal representation {xyz} <uvw> are used. Moreover, the total volume percentage of the component is given. For texture strength both the OD index and Maximum of pole figures are given. TABLE 1

TABLE 1 (continued)

TABLE 1 (continued)

TABLE 1 (continued)

Table 2 describes major components of features between 1 and 8 ECAE passes via route A through D for a strong initial texture and after annealing at (150C, lh), (225C, lh) and (300C, lh) TABLE 2

TABLE 2 (continued)

TABLE 2 (continued)

TABLE 2 (continued)

(1) The number of ECAE passes permits the control of texture strength.

The increase of the number of passes is an efficient mechanism of randomizing texture. There is an overall decrease of texture strength evidenced by the creation of new orientations and, more importantly, the large spreading of oπentations around the major components of the texture as evidenced in FIG 4. FIG. 4 is an illustration of (200) pole figures for Al with 0.5 wt.% Cu alloys processed 2, 4 and 8 passes of route D (FIG. 5) and shows spreading of orientations as "N" increases. This phenomenon is more or less effective depending on the investigated route and/or annealing treatment. For example in the as-deformed state, routes B and C result m somewhat higher textures than routes A and D (FIG. 5 and Table 1). FIG. 5 is a graph that shows the influence of ECAE deformation route and strength on texture formation as a function of number of ECAE passes. For medium to very strong starting textures, two ma areas can be distinguished in the as-deformed state(FIG.5):

Between passes 1 and 4 (with a tool angle of 90°), very strong to medium textures are obtained. In the investigation of A1.5Cu, for example, the OD index ranges from more than 7 times random to more than 48 times random which corresponds to maximum intensities of the ODF between 3000 mrd (30 times random) and more than 20000 mrd (200 times random).

For more than 4 passes (with a tool angle of 90°), medium-strong to very weak textures close to random are created. In the case of A1.5Cu alloys, OD index varies from around 11 times random to less than 1.9 times random depending on the route, which corresponds to maximum intensities of the ODF between 7000 mrd (70 times random) and around 800 mrd (8 times random).

The two mam domains are maintained after subsequent annealing, as shown in the graphs of FIGS. 6, 7, 8 and 9. However for some ECAE deformation routes (for example route B and C in the case of A1.5Cu), additional heating can give a strong texture, as discussed below. The existence of these two areas is a direct consequence of the microstructural changes occurring m the mateπal duπng intensive plastic deformation. Several types of defects (dislocations, microbands, shear bands and cells and sub-grains mside these shear bands) are gradually created during the 3 to 4 ECAE passes (for a tool angle of 90°). The internal structure of materials is divided into different shear bands while increasing the number of passes. After 3 to 4 ECAE passes, a mechanism termed dynamic recrystalhzation occurs and promotes the creation of sub-micron grains in the structure. As the number of passes increases these grains become more and more equiaxed and their mutual local mis-orientations increase giving rise to a higher number of high angle boundaries in the structure. The \ ery weak and close to random textures that are created are a consequence of three major characteristics of the dynamically recrystallized microstructures: the presence of high internal stresses at the gram boundaπes, the large number of high angle boundaries and the very fine gram size with a large grain boundary area (usually of the order of about 0.1-0.5 μm).

(2) The ECAE deformation route permits control of the major oπentations of the texture. Depending on the route, different shear planes and directions are involved at each pass (see FIG. 5 and Tables 1 and 2). Therefore shear bands of different orientations are created in the structure. For some routes these shear bands always intersect each other in the same way; for other routes new families are constantly introduced at each pass (Tables 1 and 2). All these options allow changes to the major components or orientations between each pass. The effect is particularly strong for a small number of passes before the advent of dynamic recrystalhzation. as discussed above. An important application exists in the possibility to create different types of strong textures already in the as-deformed state for a limited number of ECAE passes.

(3) Additional annealing has an important influence on both the major texture oπentations and strength (see FIGS. 6, 7, 8, 9 and Table 2).

For annealing temperatures below the static recrystalhzation, a change in both texture strength and mam oπentation is observed. This effect can be particularly strong for a low number of passes (less than about 4 passes) leading to remarkable migrations of major orientations accompanied with either a decrease or increase of texture strength. Such changes can be attributed to the instability of microstructural defects which are implemented m the crystal structure. Complex mechanisms such as recovery and sub-gram coalescence explain partly the observed phenomena. For dynamically recrystallized ultra-fine structure (after usually 4 passes) smaller modifications are encountered. They are usually associated with the transition from a highly stressed to a more equilibrium micro structure.

For annealing temperatures close to the beginning of static recrystalhzation, the same over-all results as in the above case are found. However, it is important to note that new and different textures than for low temperature annealing can be obtained, especially for a low number of ECAE passes (Table 2). This is due to static recrystalhzation which creates new grains with new orientations by diffusion mechanisms.

For annealing temperatures corresponding to developed stages of static recrystalhzation (full static recrystalhzation), textures tend to be weakened (as shown m FIGS. 6, 7, 8, 9 and Table 2). This is particularly true after 3 or 4 ECAE passes where very weak and almost random textures are created. These textures are characterized by four, six or eight fold symmetry with a higher number of cube (<200>) components.

Additional textural analysis of ECAE deformed Al and 0.5 wt.% Cu is shown in the pole figure described in FIG. 10. In this case the sample was given an initial thermochemical treatment of casting plus homogeneous plus hot forging plus cold rolling (~ 10%) plus two ECAE passes via route C plus annealing (250°C, 1 hour). The recrystallized microstructure had grain size of 40-60 μm and strong texture along {- 111 }<2-12>, {012}<-130>, {-133 }<3-l 3>. The result shows two ECAE passes (C) plus static recrystalhzation permits removal of the very strong (220) textural component of the as-forged condition.

By taking into account all the foregoing, results show that intermediate annealing between each pass provides several additional and significant opportunities to adjust desired textures. Two options are available: A. Intermediate annealing either at low temperature or just at the beginning of static recrystalhzation after a low number of passes (N<4) can give strong textures with new oπentations after subsequent deformation with or without annealing.

B. Intermediate annealing the case of full static recrystalhzation after a low or high number of passes can lead more easily to very weak textures after subsequent deformation with or without annealing.

It is also possible to repeat intermediate annealing several times in order to enhance the effects descπbed above.

(4) Starting texture has also a strong influence on both texture and strength especially after a limited number of passes (usually after 1 to 4 passes). For a higher number of passes the ECAE deformation is very large and new mechanisms are taking place which lessen the magnitude of the influence of the starting texture. Two situations are noted (FIG. 5 and Table 1 for route A and D):

A. For strong to medium starting textures, after further deformation with or without annealing, it is possible to obtain very strong to medium textures before 4 passes and strong-medium to very weak textures after approximately 4 passes according to the results descπbed m paragraphs 1 , 2 and 3.

B. For medium to very weak starting textures it will be more difficult to obtain very strong to strong textures at least m the as-deformed state. Weak starting textures are more likely to enhance and promote weak to random textures after ECAE deformation with or without annealing (Table 1). (5) Second phase particles have a pronounced effect on texture. Large

(>1 μm) and non-u formly distributed particles are not desired because they generate many problems such as arcing during sputteπng. Very fine (>1 μm) and uniformly distπbuted second phase particles are of particular interest and offer many advantages. Firstly, they tend to create a more even stress-strain state duπng ECAE deformation.

Secondly, they stabilize the already ECAE-deformed microstructure in particular after further annealing. In this case particles pm gram boundaries making them more difficult to change. These two major effects evidently affect the texture of mateπals. Especially: for a small number of passes (<4 passes), the effects described previously m sections (1) to (4) can be enhanced due to the presence of second phase particles in particular for strong textures. for a large number of passes, second phase particles are effective in promoting the randomization of texture.

In order to take advantage of the possibilities offered by the ECAE technique in terms of texture control, three types of results can be achieved:

A. Mateπals (sputteπng targets) with strong to very strong (ODF> 10000 mrd) textures. In particular this can be obtained for a small number of passes with or without subsequent annealing or intermediate annealing. A strong starting texture is a factor favoring the creation of strong textures. For example in the case of A1.5Cu alloy Table 1 gives all the major components of oπentations which were created for different deformation routes (A,B,C,D) between 1 and 4 passes. The as-deformed state as well as deformation followed either by low temperature annealing (150°C, lh) or by annealing at the beginning of static recrystalhzation (225°C, l h) or after full recrystalhzation (300°C, lh) are considered in this table. The original texture is displayed in FIG. 7. It is important to note that in most cases new types of textures have been found. Not only {200} and {220} textures are present but also { 111 }, {140}, {120}, {130}, {123}, {133}, {252} or, for example, {146}. For strong textures, one or two mam components are usually present.

B. Mateπal (sputtering targets) with weak to close to random textures with an ultra-fine gram size less than 1 μm. Whatever the route this can be obtained after more than 3 to 4 ECAE passes followed or not by annealing or intermediate annealing at a temperature below the beginning of recrystalhzation temperature. A very weak starting texture is a factor favoring the creation of close to random textures.

C. Statically recrystallized mateπals (sputteπng targets) with weak to close to random textures with a fine grain size above approximately 1 μm. Whatever the route this can be obtained after more than 3 to 4 ECAE passes followed by annealing or intermediate annealing at a temperature above the beginning of recrystalhzation temperature. A very weak starting texture is a factor favoring the creation of close to random textures. Another embodiment of the invention is an apparatus for performing the process to produce targets. The apparatus (FIGS. 11, 11A and 11B) includes die assembly 1, die base 2, slider 3, punch assembly 4,6 hydraulic cylinder 5, sensor 7. and guide pins 1 1. Also the die is provided with heating elements 12. Die assembly 1 has a vertical channel 8. A hoπzontal channel 9 is formed between die assembly 1 and slider 3. The die is fixed at table 10 of press, punch assembly 4, 6 is attached to press ram. In the original position a-a the forward end of slider 3 overlaps channel 1 , punch 4 is in a top position, and a well lubπcated billet is inserted into the vertical channel. During a working stroke punch 4 moves down, enters channel 8, touches the billet and extrudes it into channel 9. Slider 3 moves together with billet. At the end of stroke the punch reaches the top edge of channel 9 and then returns to the oπgmal position. Cylinder 5 moves the slider to position b-b, releases the billet, returns the slider to the position a-a and ejects the processed billet from the die. The following features are noted:

(a) During extrusion slider 3 is moved by hydraulic cylinder 5 with the same speed as extruded mateπal mside channel 9. To control speed, the slider is provided with sensor 7. That results in full elimination of fπction and mateπal sticking to the slider, m lower press load and effective ECAE;

(b) Die assembly 1 is attached to die base 2 by guide pms 11 which provide free run δ. During extrusion the die assembly is nestled to the base plate 2 by friction acted mside channel 8. When the punch returns to the original position, no force acts on the die assembly and slider, and cylinder 3 can easily move the slider to position b-b and then eject the billet from the die.

(c) Three billet walls in the second channel are formed by the slider (FIG. 11 A) that minimizes fπction in the second channel.

(d) The side walls of the second channel in the slider are provided with drafts from 5° to 12°. In this way the billet is kept inside the slider during extrusion but may be ejected from the slider after completing extrusion. Also, thm flash formed m clearances between the slider and die assembly may be easily trimmed.

(e) Die assembly is provided with heater 12 and spπngs 13. Before processing, spπngs 13 guarantee the clearance δ between die assembly 1 and die base 2. During heating this clearance provides thermoisolation between die assembly and die base that results in short heating time, low heating power and high heating temperature.

The apparatus is relatively simple, reliable and may be used with ordinary presses.

Claims

1 A sputtering target made by a process including casting having a target surface with the following characteristics: a) substantially homogenous composition at any location; b) substantial absence of pores, voids, inclusions and other casting defects; c) substantial absence of precipitates; d) grain size less than about 1 μm; and e) substantially uniform structure and texture at any location.

2. A sputtering target according to claim 1 comprising Al, Ti, Cu, Ta,

3. A sputtering target according to claim 1 comprising Al and about 0.5 wt.% Cu.

4. A method for fabricating an article suitable for use as a sputteπng target comprising the steps of: a. providing a cast ingot; b. homogenizing said mgot at time and temperature sufficient for redistribution of macrosegregations and microsegregations; and c. subjecting said mgot to equal channel angular extrusion to refine grains therein.

5. A method according to claim 4 further comprising, after subjecting said ingot to equal channel angular extrusion to refine grains therein, manufacturing same to produce a sputteπng target.

6. A method according to claim 4 wherein said mgot is subject to 4 to 6 passes of equal channel angular extrusion.

7. A method of making a sputtering target comprising the steps of: a. providing a cast mgot with a length-to-diameter ratio up to 2; b. hot forging said mgot with reductions and to a thickness sufficient for healing and full elimination of case defects; c. subjecting said hot forged product to equal channel extrusion; and d. manufacturing into a sputteπng target.

8. A method of fabπcatmg an article suitable for use as a sputtering target comprising the steps of: a. providing a cast mgot; b. solutionizing heat treating said cast mgot at temperature and time necessary to dissolve all precipitates and particle bearing phases; and c. Equal channel angular extruding at temperature below aging temperatures.

9. A method according to claim 8 further comprising manufactuπng to produce a sputtering target.

10. A method according to claim 4 including: a. homogenizing the ingot; b. hot forging of the ingot; and c. Equal channel angular extruding forged billet.

11. A method according to claim 7 including: a. hot forging the ingot; and b. equal channel angular extruding the forged billet.

12. A method according to claim 10 further comprising producing a sputteπng target.

13. A method according to claim 11 further comprising producing a sputteπng target.

14. A method according to claim 1 further comprising a solutionizing heat treatment prior to equal channel angular extrusion.

15 A method according to claim 1 further comprising water quenching after homogenizing

16. A method according to claim 7 including: a. heating the cast mgot before forging at a temperature and for a time sufficient for solutionizing; b. hot forging at a temperature above solutionizing temperature; and c. water quenching the forged billet immediately after forging.

17. A method according to claim 4 including: a. cooling the ingot after homogenizing to a forging temperature above the solutionizing temperature; b. Hot forging at a temperature above the solutionizing temperature; and c. water quenching the forged billet immediately after forging step.

18. A method according to claims 4, 7 or 8 including agmg after solutionizing and water quenching at a temperature and for a time sufficient to produce fine precipitates with an average diameter of less than 0.5 μm.

19. A billet for equal channel angular extrusion of targets fabπcated from a cast mgot of diameter do and length ho which has been forged into a disc of diameter do and thickness ho and from which two segments from two opposite sides of forged billet to provide a billet width A have been removed such a manner that thickness H corresponds to the thickness of the billet for equal channel angular extrusion, the wide A corresponds to the dimension of square billet for equal channel angular extrusion, and dimensions of the cast mgot and the forged billet are related by the formulae:

D=1.18A do 2ho=1.39.A2H

20. A method according to claims 4, 7 or 8 in which the step of equal channel angular extrusion is performed at a temperature below the temperature of static recrystalhzation and at a speed sufficient to provide uniform plastic flow, and for a number of passes and routes that provides dynamic recrystalhzation duπng processing.

21. A method according to claims 5, 9 or 13 including annealing after final target fabrication at the temperature which is equal to the temperature of the sputtered target surface during steady sputteπng.

22. A method according to claim 13 in which annealing after final target fabrication is performed gradientally by exposing the sputtered target surface to the same heating condition and exposing an opposite target surface to the same cooling condition as under target sputteπng during a sufficient time for steady annealing.

23. A method according to claim 22 in which gradient annealing of the target is performed directly m a sputteπng machine at sputteπng conditions before starting a production run.

24. A method according to claims 4, 7 or 8 which the step of equal channel angular extrusion includes a first extrusion with 1 to 5 passes into different directions intermediate annealing at a low temperature and for a time sufficient to produce very fine precipitates of average diameter less than about 0.1 μm, and a second extrusion with a sufficient number of passes to develop a dynamically recrystallized structure.

25. A method for controlling texture of sputtering targets by a process according to claim 4 wherein the step of equal channel angular extrusion is performed by changing the number of passes and billet orientation between successive passes in a manner to produce a desired final texture strength and oπentation.

26. A method for controlling texture of sputtering targets by a process according to claim 5 wherein the step of equal channel angular extrusion is performed by changing the number of passes and billet orientation between successive passes m a manner to produce a desired final texture strength and oπentation.

27. A method for controlling texture of sputteπng targets by a process according to claim 8 wherein the step of equal channel angular extrusion is performed by changing the number of passes and billet orientation between successive passes in a manner to produce a desired final texture strength and oπentation.

28 A method according to claim 25 including a preliminary processing performed before extrusion to produce strong oπginal texture of the same orientation as of the desired final texture after equal channel angular extrusion.

29. A method according to claim 25 including the additional step of recovery annealing performed between extrusion passes at temperatures below the temperature of static recrystalhzation.

30. A method according to claim 25 including the additional step of recovery annealing after equal channel angular extrusion at temperatures below the temperature of static recrystalhzation.

31. A method according to claim 25 including the additional step of recrystalhzation annealing performed between extrusion passes at a temperature equal to the beginning temperature of static recrystalhzation.

32. A method according to claim 25 including the additional step of annealing performed after the step of equal channel angular extrusion at a temperature equal to the beginning temperature of static recrystalhzation.

33. A method according to claim 25 including the additional step of recrystalhzation annealing performed between extrusion passes at temperature above the temperature of full static recrystalhzation.

34. A method according to claim 25 including the additional step of recrystalhzation annealing performed after the step of equal channel angular extrusion at temperatures above the temperature of full static recrystalhzation.

35. A method according to claims 4, 7 or 8 wherein at least different types of thermal treatments are performed between extrusion passes and after the final step of equal channel angular extrusion.

36. A method according to claim 4, 7 or 8 further comprising a thermal treatment for control of gram size and distribution of second phase particles.

37 A method for controlling the texture of an alloy, comprising the steps of defining equal channel angular extrusion routes for defining predetermined shear planes and crystallographic directions in the alloy, selecting at least a route from the defined routes for plastically deforming the alloy during equal channel angular extrusion; and subjecting the alloy to a predetermined number of passes through the selected routes.

38. An alloy produced by the method of claim 37 comprising a randomized microstructure and a texture with a substantially uniform gram size

39. An alloy produced by the method of claim 37 comprising a strong texture.

40. An alloy produced by the method of claim 37 comprising substantially random texture.

41. A method for controlling the texture of an alloy, comprising the steps of: defining equal channel angular extrusion routes for defining predetermined shear planes and crystallographic directions in the alloy; selecting at least one route from the defined routes for processing the alloy; processing the alloy through the selected at least one route; and recovery annealing the alloy at a temperature range and a time peπod determined for the alloy for obtaining substantially uniform gram size, global microstructure and texture.

42. A method for influencing the texture evolution of an alloy, comprising the steps: defining equal channel angular extrusion routes for defining predetermined shear planes and crystallographic directions the alloy; selecting at least one route from the defined routes for processing the alloy; processing the alloy through the selected at least one route; recovery annealing the alloy at a temperature range and a time peπod determined for the alloy; and further recovery annealing the alloy at a temperature greater than maximum temperature of the temperature range.

43 A method for controlling the texture of an alloy, comprising the steps of: defining equal channel angular extrusion routes for defining predetermined shear planes and crystallographic directions in the alloy; selecting at least one route from the defined routes for processing the alloy; processing the alloy through the selected at least one route; and post-extrusion processing the alloy to create a specific texture, a uniform gram size and a high texture strength for the alloy.

44. A method for controlling the texture of an alloy, which comprises the steps of: defining equal channel angular extrusion routes for defining predetermined shear planes and crystallographic directions m the alloy; selecting at least one route from the defined routes for processing the alloy; processing the alloy through the selected at least one route; and further processing the alloy under equal channel angular extrusion in order to create a specific texture, a uniform gram size and a high texture strength for the alloy.