SPUTTERING TARGETS, SPUTTER REACTORS, METHODS OF FORMING CAST INGOTS, AND METHODS OF FORMING METALLIC ARTICLES
The invention encompasses a method of forming a metallic article. An ingot of metallic material is provided, and such ingot has an initial thickness. The ingot is subjected to hot forging. The product of the hot forging is quenched to fix an average grain size of less than 250 microns within the metallic material. The quenched material can be formed into a three dimensional physical vapor deposition target. The invention also includes a method of forming a cast ingot. In particular aspects, the cast ingot is a high-purity copper material. The invention also includes physical vapor deposition targets, and magnetron plasma sputter reactor assemblies.
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This patent claims continuation-in-part priority to PCT application serial number PCT/US01/45650, which was filed Oct. 9, 2001, and which claims priority to U.S. provisional application Ser. No. 60/306,836, which was filed Jul. 19, 2001. This patent also claims continuation-in-part priority to U.S. provisional application Ser. No. 60/493,183, which was filed Aug. 7, 2003.
TECHNICAL FIELDThe invention pertains to methods of forming cast ingots, and also pertains to methods of forming high-purity metallic articles. Additionally, the invention pertains to methods of forming sputtering targets, and pertains to sputtering target constructions. Also, the invention pertains to sputter reactor assemblies. In particular aspects, the invention pertains to sputtering target constructions comprising, consisting essentially of, or consisting of, non-magnetic materials.
BACKGROUND OF THE INVENTIONPhysical vapor deposition (PVD) is a commonly used method for forming thin layers of material in semiconductor fabrication processes. PVD includes sputtering processes. In an exemplary PVD process, a cathodic target is exposed to a beam of high-intensity particles. As the high-intensity particles impact a surface of the target, they force materials to be ejected from the target surface. The materials can then settle on a semiconductor substrate to form a thin film of the materials across the substrate.
Difficulties are encountered during PVD processes in attempting to obtain a uniform film thickness across the various undulating features that can be associated with a semiconductor substrate surface. Attempts have been made to address such difficulties with target geometry. Accordingly, numerous target geometries are currently being commercially produced. Exemplary geometries are described with reference to
Each of the cross-sectional side views of
The Applied Materials™ target (
Exemplary sputtering apparatuses which can utilize Applied Materials™ target 10 of
The reactor 200 comprises a magnetron 202 symmetrically arranged about a central axis 204. The target 10, or at least its interior surface, is composed of a material to be sputter-deposited. The target can comprise, for example, Ti, Ta or high purity copper. Target 10 comprises an annularly-shaped downwardly facing vault 206 (i.e., the hollow 19 described with reference to
The magnetron reactor 200 includes one or more central magnets 224 having a first vertical magnetic polarization, and one or more outer magnets 226 of a second vertical magnetic polarization opposite the first polarization and arranged in an annular pattern. The magnets 224 and 226 can be permanent magnets, and accordingly can be composed of strongly ferromagnetic material. Inner magnets 224 are disposed within a cylindrical central well 228 (i.e., the cavity 17 of
A cylindrical inner pole piece 232 of magnetically soft material abuts the lower ends of inner magnets 224 and extends deep within target well 228 adjacent the inner target sidewall 212. Magnetic pieces 230 and 232 can be configured in size to emit a magnetic field (illustrated by dashed arrows within vault 206) that is substantially perpendicular to the magnetic field of the corresponding associated magnets 224 and 226. The magnetic field is, accordingly, also substantially perpendicular to the target vault sidewalls 210 and 212.
Reactor 200 includes a vacuum chamber body 222 which can have a dielectric target isolator (not shown) provided therein. Wafer 208 is clamped to a heater pedestal electrode 250 by appropriate mechanisms, such as, for example, a clamp ring (not shown). An electrically grounded shield (not shown) is typically provided to act as an anode with respect to the cathode target, and a power supply (not shown) is provided to negatively bias the cathode target. Various shields and power supplies which can be utilized with the apparatus of
A port 252 is provided to extend through body 222, and a vacuum pumping system 254 is utilized to pump a vacuum within chamber 200 through port 252. An RF power supply 256 is utilized to RF bias pedestal 250, and a controller 258 is provided to regulate various aspects of apparatus 200, including, for example, the RF controller 256 and the vacuum pump 254, as shown.
It can be desired to form sputtering targets having a small average grain size. It is frequently found that targets having a smaller average grain size of the materials utilized therein will produce more uniform deposited films than will targets having the same materials with a larger grain size. A postulated mechanism for the effect of the smaller grain size on uniformity of deposited films is that small grain sizes can reduce micro-arcing problems relative to large grain sizes. The improvement in deposited film uniformity that can be achieved with materials having smaller grain sizes has led to a desire to incorporate small grain size materials into sputtering targets. It is found that small grain size materials can be formed within two-dimensional sputtering targets simply by subjecting the target materials to high compression during formation of the materials. Since the two-dimensional targets are essentially flat, high-compression technology can be readily incorporated into the processes of forming two dimensional targets. In contrast, it has proven difficult to form three dimensional targets having small grain sizes therein. It would be particularly desired to form monolithic copper targets having the complex geometries of the
Numerous materials can be utilized in forming sputtering targets, with exemplary materials being metallic materials (such as, for example, materials comprising one or more of Cu, Ni, Co, Mo, Ta, Al, and Ti), of which some materials can be non-magnetic. One of the materials that can be particularly desired for utilization in sputtering targets is high-purity copper (with the term “high purity” referring to a copper material having a purity of at least 99.995 weight percent). High-purity copper materials are frequently utilized in semiconductor fabrication processes for forming electrical interconnects associated with semiconductor circuitry. It would be desirable to develop processing which could form three-dimensional high-purity copper targets having an average grain size of less than or equal to about 250 microns.
SUMMARY OF THE INVENTIONIn one aspect, the invention encompasses a method of forming a metallic article, such as, for example, a sputtering target. The metal of the metallic article can comprise, for example, one or more of Cu, Ni, Co, Ta, Al, and Ti, and in particular embodiments can comprise Ta, Ti, or Cu. In a particular aspect, the invention encompasses a method of forming a high-purity copper article. An ingot of copper material is provided, with such ingot having a copper purity of at least 99.995 weight percent, and further having an initial grain size greater than 250 microns, and an initial thickness. The ingot is subjected to hot forging at a temperature of from about 700° F. to about 1,100° F. under sufficient pressure and time to reduce a thickness of the ingot by from about 40% to about 90% of the initial thickness. The product of the hot forging is quenched to fix an average grain size of less than 250 microns within the high-purity copper material. The average grain size can be fixed to be less than 200 microns, and even to be less than 100 microns. In particular aspects, the quenched material is formed into a three dimensional physical vapor deposition target.
In another aspect, the invention encompasses a method of forming a cast ingot. A mold is provided. Such mold has an interior cavity. The interior cavity is partially filled with a first charge of molten material. The first charge is cooled within the interior cavity to partially solidify such first charge. While the first charge of molten material is only partially solidified, a remaining portion of the interior cavity is at least partially filled with a second charge of the molten material. The first and second charges are cooled within the interior cavity to form an ingot comprising the first and second charges of the material. In particular aspects, the cast ingot is a high-purity copper material.
In yet another aspect, the invention encompasses various target constructions having particular geometries, and/or having an average grain size of less than about 250 microns.
In yet another aspect, the invention encompasses various monolithic copper target constructions in which the average grain size of the copper is less than 250 microns.
Preferred embodiments of the invention are described below with reference to the following accompanying drawings.
In one aspect, the invention encompasses a method of forming a metallic article having a grain size of less than about 250 μm, preferably less than about 200 μm, and even more preferably less than about 100 μm. Such embodiment is described with reference to
Referring to
Apparatus 30 can be considered to comprise a press configured to press against the opposing ends 22 and 24 of ingot 20. Apparatus 30 comprises a first portion 32, and an opposing second portion 34. In operation, ingot 20 is placed between portions 32 and 34, with first end 22 proximate and facing first portion 32, and second end 24 proximate and facing second portion 34. Portions 32 and 34 are then displaced relative to one another to compress ingot 20 between them. The displacement of portions 32 and 34 is illustrated by arrow 37 in
The hot forging converts ingot 20 into a hot-forged product (shown in
Ingot 20 will typically initially comprise an average grain size of about 10,000 μm if the ingot is a cast material, and such grain size can be reduced to less than or equal to 250 μm, 200 μm, or even 100 μm with hot-forging of the present invention. For instance, in an exemplary process in which a thickness of a high purity copper ingot 20 is reduced to about 30% of an initial thickness in a time of less than about one hour, the resulting hot-forged product had a measured average grain size of from about 85 microns to 90 microns after quenching to a temperature of about 70° F.
Among the parameters that can affect a grain size ultimately formed within the hot-forged product obtained by the compression of
In the shown preferred embodiment, lubricating materials 36 and 38 are provided between ingot 20 and the portions 32 and 34, respectively, of apparatus 30. Lubricating materials 36 and 38 preferably comprise a solid lubricant, such as, for example, graphite foil. The solid lubricant can be preferred over liquid lubricants, as solid lubricants are found to be more suitable for the high temperatures employed in the hot forging process of the present invention. In less preferred embodiments, liquid lubricants can be utilized.
However, it is found that liquid lubricants typically burn under the processing conditions of the present invention.
The graphite foil 36 is preferably provided to a thickness of from about 0.01 inches to about, 0.100 inches, with a preferred thickness being from about 0.030 inches to about 0.060 inches. Graphite foil 38 has similar preferred thickness ranges. It is found that if either graphite foil 36 or foil 38 is thinner than 0.01 inches, it tears during processing of the present invention, and if the foil is thicker than 0.100 inches it can interfere with the forging process by contributing its own mechanical properties to the processing. Such contribution of mechanical properties of the lubricating foil to the processing can disrupt reproducibility of the processing conditions, and further can cause an average grain size associated with the ends of ingot 20 to be different than an average grain size within an interior region (i.e., a region between the ends) of ingot 20. The graphite foil can be provided to a desired thickness by stacking several thin sheets of graphite foil on top of one another to achieve the thickness of from about 0.030 inches to about 0.060 inches. Alternatively, a single sheet of solid lubricant having the desired thickness can be utilized.
After the compression of ingot 20 within apparatus 30, the resulting hot-forged product is quenched to fix an average grain size of less than 250 μm, 200 μm, or even 100 μm within the product. The term “fix” is used to indicate that the average grain size stops changing within the material after the quench, and more specifically, that the average grain size remains fixed within the material provided that the material is kept at temperatures below 100° F. If the material is reheated to temperatures above 100° F., and particularly to temperatures in excess of 150° F., an average grain size within the material can begin to increase. The quenching of the hot-forged product typically occurs within about 15 minutes of removing the hot-forged product from press 30, and typically comprises reducing a temperature of an entirety of the hot-forged product to less than or equal to about 150° F. Such can be accomplished by immersing the hot-forged product within a tank of fluid maintained at about room temperature (about 70° F.). In preferred embodiments of the present invention, an entirety of the hot-forged product is reduced to a temperature of less than or equal to about 70° F. within about 15 minutes of removing the hot-forged product from press 30.
Hot-forged product 40 can be formed into a″ sputtering target. An exemplary method of forming product 40 into a sputtering target is described with reference to
Another method for forming a target construction from product 40 is described with reference to
Press 50 is preferably operated under conditions in which product 40 is held within a temperature range of from about 1,300° F. to about 1,700° F. for a duration of time of less than or equal to about five minutes, and preferably of less than or equal to about three minutes, to allow the material of product 40 to extrude into the desired target shape. Product 40 can be initially pre-heated in an oven to a temperature greater than 1,300° F., and then subject to pressing within press 50. The oven pre-heating is generally preferred, as it is typically not practical to heat product 40 to a desired temperature in excess of 1,300° F. with press 50 alone.
After the material of product 40 is compressed into the desired target shape by press 50, it can be quenched under identical conditions to those discussed above for hot quenching of a forged product from apparatus 30 (
An advantage of utilizing the embodiment of
A lubricant can be applied to surfaces of product 40 during the processing of
The methodology of
Exterior surface 309 extends around end 307 (in the shown embodiment the exterior surface extends entirely around the closed end, but it is to be understood that the invention encompasses other embodiments (not shown) wherein the exterior surface extends only partially around an open end 307). Exterior surface 309 wraps around end 307 at rounded corners 304. Such rounded corners have a radius of curvature about a point (with an exemplary point 311 illustrated) of at least about 1 inch. In particular embodiments, the radius of curvature around corners 304 can be at least about 1.25 inches, 1.5 inches, 1.75 inches, 2 inches, or greater. It is preferred that the radius of curvature be small enough to avoid excess thinning of the target material at locations proximate curved regions 304. Excess thinning can be understood as thinning which detrimentally influences target performance.
Target 300 can comprise an inner shape defined by peripheral surface 308 which is substantially identical to, or in particular embodiments exactly identical to, a prior art Applied Materials™ target; and yet comprises an outer shape defined by peripheral surface 309 which is different than the prior Applied Materials™ target.
An advantage of forming curved corners 304 is that such can simplify the process of
The shown target has orifices 316 extending through flanges 318, and configured for attaching the target to a sputtering apparatus. It is to be understood, however, that the illustrated flanges 318 and orifices 316 are exemplary, and that other configurations can be utilized in target constructions of the present invention.
Target 300 can consist essentially of a material which comprises one or more of Ni, Co, Ta, Al, and Ti; and in particular embodiments that material can consist essentially of Cu or Ti.
Referring to
Referring to
A difficulty which has been found in utilizing the processing of
Shrinkage defect 72 occurs during cooling of the material of ingot 70 in a casting process. In applications of the present invention, it can be preferred that an ingot have a usable portion which is at least 14 inches in thickness, and in some applications it can be desired that the ingot initially be about 17 inches in usable thickness. One method of achieving such ingots would be to initially form ingots which are much thicker than is desired, and to then cut a significant amount of the ingot away to remove a shrinkage defect. However, it would be preferred to develop methods of forming ingots which substantially alleviate the formation of a shrinkage defect within the ingots.
A method of forming ingots in accordance with the present invention is described with reference to
Referring to
Referring to
In particular embodiments, each of the successive charges of molten material provided within interior cavity 102 after the first charge fill a volume corresponding to about 10% of the original volume of the interior cavity. Accordingly, if a first charge fills about 50% of a volume of the original cavity, each additional charge will fill about 10% of such volume of the original cavity, and there will be about five such additional charges utilized to entirely fill the ingot mold. In another particular embodiment, a first charge fills about 90% of the original volume of the interior cavity, and the remaining volume is filled with a single subsequent charge. The casting of the present invention can comprise vacuum casting which is performed in a vacuum chamber and under a pressure of about 200 mTorr.
Methodology of the present invention can be utilized to form three-dimensional targets having an average grain size of less than or equal to 250 microns, 200 microns, or even 100 microns. For instance, methodology of the present invention can be utilized to form monolithic copper targets having a copper purity of at least 99.995 weight percent, and having complex three dimensional shapes of the types exemplified in
Although particular metals and alloys are described above for the exemplary aspects of the invention being discussed, it is to be understood that any suitable composition can be utilized in the methodology and target constructions of the present invention. Among the numerous alloys and metal-containing compositions that can be utilized are compositions comprise copper together with one or more of Cd, Ca, Au, Ag, Be, Li, Mg, Al, Pd, Hg, Ni, In, Zn, B, Ga, Mn, Sn, Ge, W, Cr, O, Sb, Ir, P, As, Co, Te, Fe, S, Ti, Zr, Sc, and Hf. Exemplary compositions can consist essentially of less than or equal to about 99.99% copper by weight and at least one element selected from the group consisting of Cd, Ca, Au, Ag, Be, Li, Mg, Al, Pd, Hg, Ni, In, Zn, B, Ga, Mn, Sn, Ge, W, Cr, O, Sb, Ir, P, As, Co, Te, Fe, S, Ti, Zr, Sc, Sn and Hf. In particular instances, the at least one element can preferably be selected from Ag, Al, In, Zn, B, Ga, Mn, Sn, Ge, Ti and Zr. A total amount of the at least one element present in the constructions can preferably be from at least about 100 ppm by weight to less than about 10% by weight. More preferably, the at least one element can be present at from at least 1000 ppm to less than about 2%, by weight. Typically the at least one element will be present to about 0.5 atomic percent.
A specific composition which can be utilized in the various targets described herein is a composition comprising, consisting essentially of, or consisting of CuSn, with the Sn being present to from about 100 ppm (by weight) to about 3 atomic percent, and with a typically amount of Sn being about 0.5 atomic percent.
Another specific composition which can be utilized in the various targets described herein is a composition comprising, consisting essentially of, or consisting of CuAl, with the Al being present to from about 100 ppm (by weight) to about 3 atomic percent, and with a typically amount of Al being about 0.5 atomic percent.
Another specific composition which can be utilized in the various targets described herein is a composition comprising, consisting essentially of, or consisting of CuAg, with the Ag being present to from about 100 ppm (by weight) to about 3 atomic percent, and with a typically amount of Ag being about 0.5 atomic percent.
Claims
1-89. (canceled)
90. A method of forming a three-dimensional physical vapor deposition target, the method comprising:
- heating an ingot, the ingot defining first and second perpendicular directions;
- forging the ingot to reduce a thickness of the ingot by 60% to 90% along the first direction to form a hot-forged product having a reduced thickness along the first direction and an increased size along a second direction;
- quenching the hot-forged product; and
- forming the quenched hot-forged product into a three-dimensional physical vapor deposition target with a press, wherein the three-dimensional physical vapor deposition target has an average grain size of less than 250 microns.
91. The method of claim 90, wherein the ingot comprises copper.
92. The method of claim 90, wherein the step of heating the ingot comprises heating the ingot to a temperature greater than 700° F.
93. The method of claim 90, wherein the ingot contains at least 99.995 weight percent copper.
94. The method of claim 90, wherein the ingot is a copper alloy ingot.
95. The method of claim 90, wherein the ingot consists essentially of copper and at least one element selected from the group consisting of Cd, Ca, Au, Ag, Be, Li, Mg, Al, Pd, Hg, Ni, In, Zn, B, Ga, Mn, Sn, Ge, W, Cr, O, Sb, Ir, P, As, Co, Te, Fe, S, Ti, Zr, Sc, Sn and Hf.
96. The method of claim 95, wherein the total amount of the at least one element is from at least about 100 ppm to less than about 10% by weight.
97. The method of claim 90, wherein the three-dimensional physical vapor deposition target has an average grain size of less than 200 microns.
98. The method of claim 90, wherein the three-dimensional physical vapor deposition target has an average grain size of less than 100 microns.
99. The method of claim 90, wherein the step of forging the ingot comprises forging the ingot along only the first direction.
100. The method of claim 90, wherein the press comprises first and second portions movable towards one another.
101. A method of forming a three-dimensional physical vapor deposition target, the method comprising:
- heating an ingot to a temperature greater than 700° F., the ingot comprising copper and having first and second perpendicular directions;
- compressing the ingot along only the first direction to form a hot-forged product;
- quenching the hot-forged product; and
- forming the quenched hot-forged product into a three-dimensional physical vapor deposition target with a press, wherein the three-dimensional physical vapor deposition target has an average grain size of less than 250 microns.
102. The method of claim 101, wherein the ingot is a copper ingot having a purity of at least 99.995 weight percent.
103. The method of claim 101, wherein the ingot is a copper alloy ingot.
104. The method of claim 101, wherein the quenched hot-forged product has is larger in size along the first direction and smaller in size along the second direction than the ingot.
105. The method of claim 101, wherein the three-dimensional physical vapor deposition target has an average grain size of less than 200 microns.
106. The method of claim 101, wherein the three-dimensional physical vapor deposition target has an average grain size of less than 100 microns.
107. The method of claim 101, wherein compressing the ingot comprises compressing the ingot to reduce the thickness by 60% to 90%.
Type: Application
Filed: Jul 11, 2012
Publication Date: Nov 1, 2012
Applicant: HONEYWELL INTERNATIONAL INC. (Morristown, NJ)
Inventors: Chi tse Wu (Veradale, WA), Wuwen Yi (Veradale, WA), Frederick B. Hidden (Spokane, WA), Susan D. Strothers (Spokane, WA)
Application Number: 13/546,705
International Classification: C22F 1/08 (20060101); C21D 8/00 (20060101);