KR101147941B1 - Cylindrical target obtained by hot isostatic pressing - Google Patents

Abstract

A rotating target and a method for generating the target output are described. The target forming material is poured into a hollow formed between the cylindrical molds and the inner tube is held coaxially by the top and bottom closure bodies. The assembly is subjected to hot isostatic treatment at elevated temperatures and pressures. The method differs from the prior art in that the inner tube deforms during hot isostatic treatment and presses the target forming material against the outer mold which is virtually undeformed.

Description

Cylindrical target obtained by hot isotropic pressure treatment {CYLINDRICAL TARGET OBTAINED BY HOT ISOSTATIC PRESSING}

The present invention relates to a method for producing a rotatable sputtering target by outward hot isostatic pressing (HIP).

Advantages of rotating cylindrical targets, such as increased material usage and reduced arcing, are that they are more attractive for using non-traditional materials such as ceramics. The high heat needed to melt or vaporize these materials prevents the use of conventional target manufacturing methods such as casting. Nowadays, there are two most common routes for manufacturing rotary ceramic targets directly from the backing tube, which is

A plasma spray in which the powder comprising ceramic is heated by the gas plasma and sprayed at high speed on the backing tube in a controlled gas atmosphere. See, for example, US Pat. No. 6,461,686, wherein the target material is TiO _x (x <2). However, this method cannot be applied, for example, if the powder is too fine or if there is a possibility of sticking in the feeder, it is difficult to inject the powder into the nozzle jet.

Hot isotropic pressure treatment (HIPping). The target forming material here consists of a deformable cylindrical can having a relatively thin wall with an undeformed core, and the undeformed core is mounted coaxially with the cylindrical can. After the discharge of the intergranular gas by means of a gas tight seal, the can is kept at high temperature (250-1500 ° C.), while being subjected to high pressure (50 to 200 MPa, in particular by a fluid which is usually argon). After subsequent cooling and pressure normalization, the can is mechanically removed from the target material. Pressure and temperature increase the density of the powder with a solid glassy material having a density very close to the theoretical density.

Rotary sputtering targets obtained by the HIP method are disclosed in US Pat. No. 5,354,446 and US Pat. No. 5,435,965. An undeformed core is a solid metal cylinder in which a target material is dissolved in a hot isostatic treatment. Solid metal cylinders may be coated with an interlayer to mitigate thermal stress between the core and the target during operation of the target. (US Pat. No. 5,354,446) Solid metal may also be used to improve adhesion between the backing tube and the target material. It can be mechanically processed (threaded or sand blasted). (US Pat. No. 5,354,446) Instead of solid cylinders, it has been proposed in US Pat. No. 5,435,965 to use round tubes.

The wall of the outer can should not be too thick and the wall does not interfere with the isostatic action of the powder. The compressibility of the outer can depends on the dimensions of the can, the final thickness of the target material layer and the compactness of the powder. If the compressibility of the outer can material exceeds the threshold, the outer can will be buckled, ie the compressibility of the outer can is no longer uniform and the outer surfaces are corrugated together. When torsion occurs, the degree of compaction of the non-melting target material is no longer uniform, resulting in a non-uniform material. If the target material is melted during the HIP process, the material will continue to compact evenly. In both cases, the irregular shape of the can becomes difficult to control the can from the ingot and requires machining of the outer surface (shown in Table 2 of US Pat. No. 5,435,965). Such machining is expensive as well as additional process steps. Causes significant loss of material.

It is an object of the present invention to obviate the aforementioned disadvantages of the prior art. More specifically, it is an object of the present invention to eliminate the additional process steps of machining the outer surface of the ingot. In addition, the loss of material by this machining step is also prevented. Other problems of the existing technology will also be solved as disclosed in the description below.

A first aspect of the invention relates to a method for producing a rotary sputtering target described by combining the features of claims 1 and its dependent claims.

This way,

(A) Provide an inner tube. Finally this inner tube will be a carrier of the target material. The outer surface of this inner tube may or may not have a surface coating or surface treatment (such as threading, brushing or grit blasting) to improve the adhesion of the target material to the inner tube. Alternatively, such inner tubes may be treated with a coating having a median thermal expansion coefficient between the inner tube and the target material to relieve residual thermal stress after cooling. These coatings may be applied by known techniques such as plasma sprays.

(B) In the second step, the outer mold is mounted around the inner tube. Such a mold has an internal cavity in the shape of a rotating body having a central axis of rotation. The mold is mounted on a central axis of rotation coaxial to the axis of the inner tube. A hollow formed between the inner tube and the outer mold is provided to hold the target forming material. The inside of the mold may or may not be covered or surface treated with an anti-stick layer, such as Al ₂ O ₃ , a thermal spray layer, or foil.

(C) A bottom annular closed body is provided between the inner tube and the mold. The closed body seals between the mold and the inner tube, retaining the seam under extreme temperatures and pressures in the next step. Sealing can be performed by welding or soldering. Sealing can also be obtained by mechanical means, such as by threaded connections, for example by threading the outside of the end of the inner tube and the inner mantle of the annular closure body. The same can be done inside the outer lid of the annular closure body and the mold end. Alternatively, the inner tube may be threaded to the center of the end flange which is then bolted to the rim attached to the mold with a suitable seal between the flange and the rim.

(D) The hollow is filled with the target forming material. Typically, the method can be used for any kind of target forming material that can be supplied in powder form. The powder may be provided by, for example, injecting into the hollow between the inner tube and the mold. Non-limiting examples of powders are ceramic powders, more particularly oxides, nitrides or carbides of metals such as indium, tin, zinc, gallium, copper, titanium, aluminum and the like. Synthetic mixtures of these ceramic powders are also possible, for example zinc oxide (ZnO) can be mixed with aluminum oxide (Al ₂ O ₃ ). Pure metal powders and mixtures of these ceramic powders are also possible to achieve the desired properties of the rotary targets, a notable example being indium sesquioxide (In ₂ O ₃ ) mixed with tin (Sn) powder. Powders may be alloyed prior to injecting them in the cavity. One alloying process, ie mechanical alloying, is for example disclosed in European patent EP 0 871 793. Those skilled in the art will understand that the powder must rise appropriately before proceeding to the next step. Most commonly this is done by vibration.

(E) Provide an upper annular closure body to seal the upper annular closure body against the inner tube and the mold. Sealing is performed by any technique as described in the process of step (C) for sealing the bottom closure body.

(F) Drain and seal the hollow. Discharge is generally carried out through the discharge tube of the upper closure body. During discharge, the density is high. Elevated temperatures during discharge (> 100 ° C.) will help remove water and other volatile contaminants from the powder. The discharge tube is sealed when a sufficient vacuum is reached. Together with the mold, the inner tube and the bottom closure body form a closed container with a hole in the center.

(G) As a next step of manufacture, the vessel is subjected to a hot isostatic treatment. This treatment is generally carried out under an inert atmosphere at a pressure of 50 to 200 MPa and at elevated temperatures between 250 ° C and 1500 ° C. The resulting target material is dictated by the exact processing state of temperature, pressure and duration. Treatment cycles can be complicated by maintaining different levels of temperature and pressure for different periods of time to obtain optimal target materials.

Steps (A) to (G) are known in the art. All parts of the container are made of metal or an alloy selected for its use. Typical materials are stainless steel, titanium and alloys thereof, aluminum and alloys thereof, Hastelloy, Inconel and the like. All parts of the container are made of the same metal or alloy but need not be so in the present invention.

The contribution of the present inventors to the state of the art is that the problem with known processes is that they press the target forming material against an unmodified outer mold in which the inner tube is deformed and substantially undeformed during the hot isostatic treatment. It is to overcome.

To ensure this, the strength requirements of the inner tube and outer mold are reversed compared to existing fields. Indeed, in order to be able to deform the inner tube, pressure must be able to enter and deform the inner tube. Even if the outer mold is subjected to the same isostatic pressure, the outer mold must be unstrained with little pressure to substantially deform the inner tube. "Non-deformation" or "substantially little deformation" means that the outer mold deforms less than the inner tube, which means that the maximum reduction in the diameter of the outer mold measured along its longitudinal axis is the diameter of the inner tube. Means less than the maximum increase. In the case of non-deformation, which means "substantially no deformation", the twisted mold is explicitly excluded.

The task of the top and bottom closure bodies is to make these modifications insignificant even if they are deformed or the process has virtually no difference in the present invention.

Differences in the degree of deformation between the inner tube and the mold can be implemented in a number of ways, as follows.

The most obvious method is to use the dimensional properties of the inner tube and the mold to change the degree of formation. For example, the inner tube is made substantially thinner than the mold. In the HIP process, the inner tube expands more easily such that the target material is pressed against the outer mold. The inner tube can be for example 1/2 or 1/3 of the material thickness of the mold.

The inner tube can be made of a softer material, different from the mold. "Ductility" relates to plastic deformation of a material. In the present invention, ductility at elevated temperatures of the process is particularly suitable. Empirically, the ductility of a metal or metal alloy increases significantly above one third of its melting point.

The inner tube can have a region with low resistance to deformation, while the mold has a substantially uniform stiffness. This can be achieved, for example, by machining the groove in the longitudinal direction of the outer or inner surface of the inner tube. The material below the groove can expand more easily than the material above the groove. The machining of the grooves can also be alternating between the inner tube side and the outer side of the inner tube, so that the thickness of the material remains substantially the same, forming a corrugated tube in the longitudinal direction. Under pressure, the tube will extend partially or wholly in the circumferential direction. This approach can result in improved adhesion of the target material to the tube and increased strength of the inner tube.

It will be apparent to those skilled in the art that various ways of implementing the degree of degree of formation can be combined.

 In a limited case, the mold can be made non-deformable and rigid that can act as a high pressure vessel for hot isostatic treatment steps. In this case, pressure is applied through the end of the inner tube. Heating may be applied through a mold or through a pressure fluid.

After the hot hot isostatic treatment step (subordinate term 2), the mold and the bottom and upper annular closed bodies are removed (subordinate term 3). In order to facilitate this operation, a mold consisting of, for example, two multiple longitudinally divided shells firmly held together by a removable band can be used. The area where the shell is in contact with another shell is also anti-stick treated to facilitate removal of the target after the HIP process. The seal between the shells is expected to prevent fluid ingress during the hot isostatic treatment. Such a seal may be effected, for example, with copper or indium gasket.

As the outer shape of the rotary sputtering target is actually determined by the shape of the mold supply, the degree of freedom of the outer shape of the sputtering target is large. It is possible to produce a cylindrical cavity coaxial with the inner tube.

The cavity may also include a cylindrical middle portion and two cylindrical ends proximate the upper and bottom closure bodies, the outer diameter of the middle portion being smaller than the diameter of the end. (Subordinate Clause 5) The outer shape of this target is US Pat. No. 6,264,803. Increase target availability as disclosed in the call.

Since the inner tube can be deformed to a smaller size in the vicinity of the upper and lower annular closure bodies, these differently deformed end sections may or may not be machined. (Subclaim 6) The end sections are cut out or cut out. In any case, the adapter piece is needed to make a rotary target connectable to the drive system of the sputtering machine since the inner tube cannot maintain engineering tolerances during the hot isostatic treatment step.

According to a second aspect of the present invention, the rotary sputtering target results from the disclosed method which is distinct from the targets of the prior art having the properties set forth in claims 8-16.

Due to the nature of the process, the inner tube extends in the circumferential direction. (Independent Clause 8) The extension ε depending on the outer diameter of each inner tube before (d ₀ ) and after (d ₁ ) hot isostatic treatment. Will be different as

ε = In (d ₁ / d ₀ )

The consolidation ratio c (ie, the ratio of the final target material density to the powder material density) is dependent not only on d ₀ and d ₁ but also on the outer diameter D of the rotary target as shown below for pure cylinders.

c = (D ² -d ₀ ² ) / (D ² -d ₁ ² )

Preferably the method for generating the target will result in an extension of at least 2% (dependent claim 9). This method will be more beneficial when a 5% extension is required to form the material (subclause 10).

Another characteristic that distinguishes the current rotary target from the rotary sputtering target of the present invention is significant when the ends of the target still exist. The inner diameter of the inner tube is greater than the inner diameter of the end section. (Subordinate term 11) The extension received by the inner tube is equal to the relative difference between the original inner diameter measured at the end section of the target and the final inner diameter measured at the end section of the target. Preferably this difference is greater than 2% (subordinate term 12). It is more preferred that this difference is greater than 5%.

The method preferably uses a material having a high consolidation ratio. Preferably, the consolidation ratio applied to the method is at least 1.5 (subordinate term 14), most preferably at least 2 (subordinate term 15). The rotary sputtering target of this method is particularly preferably the following target forming material: Are manufactured.

Indium sesquioxide (TO) alloyed with tin (subordinate term 16)

Titanium oxide (TiO _x , x≤2) (dependent clause 17)

Impurities doped with ZnO: Al or ZnO: Ga (subordinate term 18)

The material used for the inner tube is in most cases preferably one of titanium or an alloy thereof, depending on the properties of the material which best matches the ceramic formed thereon (claim 19).

The invention will be explained in more detail with reference to the accompanying drawings.

1 illustrates a prior art mold configuration for forming a rotary target by hot isostatic pressure treatment.

FIG. 2A shows the production of a preform according to the first preferred embodiment before the hot isostatic treatment, and FIG. 2B shows the configuration of the configuration of the first preferred embodiment after the hot isostatic treatment.

FIG. 3A shows the production of a preform according to the second preferred embodiment before hot isostatic treatment, and FIG. 3B shows the configuration of the configuration of the second preferred embodiment after hot isostatic treatment.

4A shows the production of a preform according to a third preferred embodiment before hot isostatic pressure treatment, and FIG. 4B shows the configuration of the configuration of the third preferred embodiment after hot isostatic pressure treatment.

1 illustrates a prior art can 100 used to fabricate a target according to a hot isostatic pressure treatment method. The thick walled inner tube 102 is used as a threaded carrier to increase the adhesion of the target material of the tube. First, the bottom 108 is welded between the inner tube 102 and the outer tube 104. The powdery target forming material 110 is injected into the hollow between the inner tube 102 and the outer tube 104. The outer tube is coated with anti-stick paper 112. After densify of the powder, the top cover 106 is welded between the inner tube 102 and the outer tube 104. After the discharge of all residual gas, the cans are subjected to hot isostatic treatment. The outer can 104, bottom and top cover are then mechanically removed.

Figure 2a shows a first preferred embodiment of the present invention, preferably the inner tube is deformed while the mold remains substantially undeformed. The HIP can 200 includes an inner tube 202 and an outer mold 204, and a bottom annular closed body 106 is welded by a welding seam 212 between the inner tube 202 and the outer mold 204. do. Can 200 is coaxial with axis 220. The dimensions of the first embodiment are summarized in Table 1 (all dimensions are in mm).

2A Bore Outer diameter thickness 202 45 50 2.5 204 60 70 5 Inner diameter Outer diameter width 206 50 60 50

The length of the can is 200 mm. All pieces are made of titanium. The cylindrical cavity is produced with an inner diameter of 50 mm, an outer diameter of 60 mm and a length of 150 mm. The cavity is partially filled (up to 100 mm in height) with ISOT powder (indium sesquioxide oxide mechanically alloyed with tin) prepared according to EP 0 871 793. Filled cans are typically tapped and vibrated to achieve a tapping density of 3.5 g / cm 3. After filling, a second titanium upper annular closure body 210 is placed on top of the powder. The whole structure is welded together. The degassing tube 214 is positioned so that gas can be discharged. After filling the can, the powder is degassed at a temperature of at least 400 ° C. Here the gas removal tube 214 is gas sealed. Can 200 is now ready for hot isostatic pressure treatment.

During the hot isostatic treatment, the pressure rises slowly to 200 MPa while the temperature rises to 700 ° C. for the same time. The cans are maintained under hot isostatic pressure for about 4 hours. After this "dwell time", the can slowly cools and the pressure decreases.

After the hot isostatic treatment, the can can be deformed as shown in FIG. 2B. The diameter of the inner tube 202 'varies from 45 mm to 48 mm when measured in the middle of the tube. The outer diameter of the mold 204 varies from 70 to 68.5 mm. The density of the final ITO is 7 g / cm 3, which is about 98% of the quantitative ITO (7.14 g / cm 3). Consolidation ratio is two. The extension of the inner tube is 6.5%.

After the hot isostatic treatment, the outer can is removed and a smooth surface remains. End sections 218 and 216 that are less strained than the middle portion are removed from the target. After insertion of the connector piece, the target is ready for mounting to the sputtering apparatus.

According to a second preferred embodiment, an extended version of the first embodiment is made. Again a titanium inner tube with an initial inner diameter of 135 mm and an outer diameter of 141 mm, thus having a wall thickness of 3 mm and a length of 600 mm, is used. The outer mold has an outer diameter of 165 mm and a thickness of 6 mm. Titanium rings with a bottom closure body of 141 mm inner diameter, 153 mm outer diameter and 100 mm thickness are used. The cavity is filled with ISOT powder up to 400 mm in height. By vibrating, a tapping density of 3.5 g / cm 3 can be achieved. After filling the same top closure body as the bottom closure body is inserted. The entire structure is welded with three degassing tubes in such a way that gas is discharged through the degassing tubes. Degassing is carried out at a temperature of at least 400 ° C. Here the tube is vacuum sealed and the can is ready for hot isostatic treatment at a pressure of 200 MPa and a temperature of 500 ° C. In this way the inner tube is deformed, limiting the outer diameter of the can. The outer diameter of the inner tube is deformed from 135 to 139, ie with a 3% circumferential extension, with the outer diameter of the can 163.5. The density of the material is increased to 6.4 g / cm 3, yielding a consolidation ratio of 1.8. Very little material is lost as the mold is removed from the final target material.

The influence of the thickness of the outer mold is also studied more than in the third preferred embodiment. Here the same procedure is carried out with the same material as in the second embodiment, but the dimensions of the outer mold are different. The dimensions before and after the hot isostatic treatment are summarized in Table 2.

Inner tube Outer mold I'm after I'm after ID 127 139 160 (159) OD 133 (145) 200 199 L 600 594

All numbers are in mm. "ID" and "OD" represent an inner diameter and an outer diameter, respectively. The numbers in parentheses are calculated by taking the thickness of the tube or mold. The thick outer mold (20 mm) causes less deformation. The inner tube has an increased diameter of 12 mm, ie the material extends circumferentially by 9%. No torsion occurs and densification is uniform along the length of the tube. The outer surface of the target becomes smooth after removing the outer mold and no additional matching is necessary. At both ends of the inner tube, the inner diameter of the inner tube is less than the middle (approximately 130 mm) because of the transition between the less compressed annular closure bodies, and the inner tube is inflated (as shown in FIG. 2B, claim 11). In this way, the targets of the inventive method can be distinguished from other targets produced by other methods.

In accordance with the fourth preferred embodiment shown in FIGS. 3A and 3B, the bottom and top annular closed bodies 310 are of a particular shape to ensure proper compaction of the powder in the vicinity of the end section after hot isostatic treatment 310 ′. Has In the fifth preferred embodiment 400 shown in FIG. 4, the outer mold 404 can be made thin so that it can be locally weakened 420 so that the target surface obtains a particular shape after hot isostatic treatment.

Claims (19)

A method for manufacturing a rotary sputtering target, Providing an inner tube; Mounting an outer mold around the inner tube, the outer mold forming a cavity, the cavity having a rotatable body shape, the cavity being assigned to the same axis as the inner tube to create a hollow between the inner tube and the mold Forming; Providing a bottom annular closure body in the hollow and sealing the bottom closure body against the inner tube and the mold; Filling the hollow with a target forming material; Providing an upper annular closure body and sealing the annular closure body to the inner tube and the mold; Discharging and sealing the hollow, the inner tube, the mold, the top closure body and the bottom closure body to form a container having a hole in the middle; And And subjecting the container to hot isostatic pressure treatment. An inner tube is deformed during the hot isostatic treatment to pressurize the target forming material against an outer mold, The maximum decrease of the outer mold diameter measured along the longitudinal axis is less than the maximum increase of the inner tube diameter measured along the longitudinal axis Rotary sputtering target manufacturing method. The method of claim 1, And subsequently removing the mold from the container. The method of claim 2, And subsequently removing the upper annular closed body and the lower annular closed body. The method according to claim 1 or 3, And the cavity in the mold is a cylinder. The method according to claim 1 or 3, The cavity has a cylindrical middle portion and two cylindrical ends proximate the upper closure body and the bottom closure body, the intermediate portion has a first diameter, the end has a second diameter, and the second diameter is the first diameter. Rotary sputtering target manufacturing method characterized in that larger than 1 diameter. 4. The method according to any one of claims 1 to 3, And the end section of the rotatable sputtering target comprising a deformed portion of the inner tube that is less deformed than the middle portion of the inner tube further comprises the step of cutting away. 4. The method according to any one of claims 1 to 3, And subsequently assembling one or two adapter pieces for connecting the tubular target to the magnetron sputtering device in the inner tube. In a rotary sputtering target, Including an inner tube and a target material, The target material is disposed on an outer surface of the inner tube, The inner tube is made of inner tube material, The inner tube has an axis of symmetry, and wherein the inner tube material in a plane perpendicular to the axis extends at least 2% in the circumferential direction. The method of claim 8, And wherein the extension in the circumferential direction is at least 5%. In a rotary sputtering target, An inner tube, the inner tube further comprising a target material having a first end section and a second end section, the target material disposed on an outer circumferential surface of the inner tube between the first and second end sections; Has a first diameter in the end section, the inner tube has a second diameter between the first and second end sections, And said second diameter is greater than said first diameter. The method of claim 10, And the second diameter is 2% larger than the first diameter. The method of claim 10, And the second diameter is 5% larger than the first diameter. In the rotary sputtering target obtained by the method of claim 1, And the target forming material is consolidated with a factor of at least 1.5. In the rotary sputtering target obtained by the method of claim 1, And the target forming material is consolidated with a factor of at least 2.0. The method according to any one of claims 8 to 14, And said target forming material is an indium sesqui oxide alloyed with tin. The method according to any one of claims 8 to 14, And the target forming material is titanium oxide. The method according to any one of claims 8 to 14, And the target forming material is a zinc oxide impurity doped with aluminum or gallium. The method according to any one of claims 8 to 14, And the inner tube is made of titanium or a titanium alloy. delete

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