WO2007059546A2

WO2007059546A2 - Method for producing a tubular target

Info

Publication number: WO2007059546A2
Application number: PCT/AT2006/000476
Authority: WO
Inventors: Wilhelm SAGEMÜLLER; Peter Polcik; Christian Weratschnig
Original assignee: Plansee Metall Gmbh
Priority date: 2005-11-23
Filing date: 2006-11-21
Publication date: 2007-05-31
Also published as: AT8909U1; TW200721232A; WO2007059546A3

Abstract

The invention relates to a method for producing a tubular target having a tube made of the target material and a supporting tube, which are joined by internal high-pressure forming.

Description

METHOD FOR PRODUCING A TUBE TARGET

The invention relates to a method for producing a pipe target comprising a pipe or pipe sections of the target material and a support tube.

Rotary tube targets are known and described for example in US 4,422,916 and US 4,356,073. During sputtering, the tube target rotates around a magnetron located in the tube. Tube targets are predominantly used for the production of large surface coatings. The rotation of the tube target achieves a uniform removal of the sputtering material. Tube targets therefore have a high rate of utilization of the target material and a long target life, which is particularly important in expensive layer materials, as is the case with refractory metals (refractory metals having a melting point greater than 1800 ⁰ C) or precious metals. Thus, the utilization rate for planar targets is about 15 to 40% and for pipe targets at 75 to 90%.

The realized in the interior of the tube target target cooling is much more effective through the cheaper heat transfer in the tube than planar targets, which allows a higher coating rate. To ensure that even with high target utilization no cooling water leaks, further to increase the mechanical strength and to facilitate the fixation in the sputtering, the tube target usually consists of a tube or pipe sections of the material to be sputtered (hereinafter referred to briefly as target ) and a support tube. The support tube must be made of a non-magnetic material in order not to interact with the magnetic field that determines the Abtragbereich occur.

Many manufacturing processes are described for the production of the tube of the material to be sputtered. Many of these processes use a liquid-phase route, such as strand and centrifugal casting. Tubes can also be made by winding a thick band around a core and

Welding the contact areas are produced. In addition, a target can also be constructed from several pipe sections. Furthermore it is possible to deposit or apply the sputtering material by plasma spraying or hot isostatic pressing on a support tube.

The joining of the target and the support tube is a particular problem area. The bonding technique with low-melting solders (for example indium-containing solders) which is customary with planar targets is usually also used when joining a tube made of the target material with the support tube. However, a constant Lotspalt and its uniform Lotbefüllung over the circumference and the length of the tube target can be adjusted only with great effort. This is also made more difficult by delay in the soldering process. From the production of pot-shaped hollow cathodes and other joining techniques are known. Thus, EP 1 074 639 discloses a method for producing a hollow cathode sputtering target in which a composite plate consisting of the target and support tube material is produced by pressing, hot pressing, hot rolling and cold rolling. From this composite plate is the cup-shaped by a molding step

Hollow cathode sputtering target made. This process technology can only be used for very ductile target materials.

The object of the invention is therefore to provide a method for joining the target and support tube, which is reliable and leads to a fixed mechanical connection with defined heat transfer from the target to the support tube.

The object is solved by the independent claim.

In this case, the pipe or pipe sections of the target material and the support tube are joined together by hydroforming. The hydroforming or hydroforming is called an established process technology and is widely used, for example, for the production of components for the automotive industry. Internal-high-pressure forming is also described in EP 1 074 639 and WO 2004/024978 as a shaping method for the production of cup-shaped hollow cathode sputtering targets. In the method according to the invention, the tube or tube sections of the target material and the support tube are placed in a tool mold, wherein the support tube is positioned in the tube or in the tube sections of the target material and extends in the axial extent of the target material over the tube or pipe sections. The pipe sections are, for example, individual cylindrical pipe sections. The mold encloses the pipe or pipe sections. Also, the support tube is supported in the areas that extend beyond the target of mold parts. Subsequently, the tube ends of the support tube are closed by sealing stamp and the support tube is filled via the sealing plunger with a pressure transmission medium, whereby an internal pressure builds up. The pressure transfer medium is usually a liquid, preferably water with corrosion inhibitor, a water-oil emulsion or oil used. The pressure transfer medium usually has room temperature, but can also be heated in the case of oil up to 25O ⁰ C.

The internal pressure is chosen so high that the yield point of the support tube is exceeded and the tube or pipe sections of the target material are elastically or elasto-plastically deformed, so that the support tube, taking into account the elastic recovery at least partially to the pipe or pipe sections the Targetwerkstoff applies to form a joint surface. It may, depending on the target and support tube material, be advantageous to perform the transformation at higher temperatures of up to 250 ° C using oil as the pressure transmission medium.

In order to ensure a sufficient heat transfer between the target and the support tube, it is further advantageous if the joining surface between the target and the support tube is at least 20 area percent of the theoretically possible contact area. In this case, the outer side of the support tube and / or the inside of the tube or the pipe sections of the Targetwerkstoff be machined so that a micro or macro roughness, eg waviness, is formed. The preferred wave height is in the range of 10 microns to 2 mm and the wavelength at 15 microns to 100 mm. The elevations form the areas where a defined joining surface is formed. A gearing effect is achieved when the material of a joining partner flows into the recesses of the other joining partner.

The advantages of the method described are, in view of the use of the composite tube during sputtering, in the solid mechanical connection, which ensures a very good thermal contact between the target and the support tube, without the risk of melting the solder joint at a high heat input during sputtering. Moreover, it is advantageous if the target support tube material pairing is selected so that the support tube material has a higher coefficient of thermal expansion than the target material. Since in use the target has a higher temperature than the support tube, it is ensured that in use the mechanical and thus thermal connection is maintained.

From the method design, the inventive method is suitable for a variety of possible material combinations. The only restriction is that the support tube can be plastically deformed by applying radial stresses. Therefore, only metallic materials are suitable and, for process engineering reasons, again non-magnetic materials, such as austenitic steels, titanium, titanium alloys and copper alloys.

As target materials, in principle, all materials are suitable which can absorb forces defined under radial load at least in the region of their elastic deformation range. For example, the method is particularly suitable for refractory metals (V, Nb, Ta, Cr, Mo, W), for Al or Cu alloys.

In the case of refractory metals with low ductility (Cr, Mo, W), the structure and composition must be chosen such that the radial forces occurring during the joining process do not lead to any failure of the target material. Thus, excellent results were obtained with extruded molybdenum tubes with an oxygen content of less than 50 μg / g, a density greater than 99% of the theoretical density and a mean grain size transverse to the axial direction of less than 100 μm.

In the following the invention is explained in more detail by examples.

Example 1 :

MoO ₃ powder was reduced in a two-stage reduction process at 600 or 1000 ⁰ C to Mo metal powder with a grain size of 3.9 microns. In a rubber hose closed on one side with an inner diameter of 420 mm, a steel mandrel with a diameter of 141 mm was positioned in the middle. In the space between steel core and rubber wall, the molybdenum metal powder was filled.

The rubber hose was subsequently closed at its open end by means of a rubber cap. The sealed rubber tube was positioned in a cold isostatic press and compacted at a pressure of 210 MPa. The green compact had a density of 64% of the theoretical density. The outer diameter was about 300 mm. The green compact thus obtained was sintered in an indirect sintering furnace at a temperature of 1900 ⁰ C. The sintered density was 94.9% of the theoretical density.

After the sintering process, the tube blank was machined on all sides, the outside diameter being 243 mm, the inside diameter 142 mm and the length 1000 mm. The extrusion took place on a 25001

Indirect extrusion press. The tube blank was heated to a temperature of 1100 ^° C. in a gas-fired rotary hearth furnace. The lambda value was adjusted so that the atmosphere was slightly reducing, whereby oxidation of the molybdenum was prevented. After heating in the rotary hearth furnace, the extruded blank was inductively heated to a temperature of 1250 ⁰ C and rolled in a bed of glass powder, so that on the outside glass powder adhered on all sides. Subsequently, over a mandrel was pressed, whereby an extruded tube with a length of 2700 mm, an outer diameter of 170 mm and an inner diameter of 129 mm was formed.

The reshaped Mo tube was then machined (length 2004 mm, inner diameter 133 mm and outer diameter 163 mm). The support tube made of an austenitic steel was soft annealed, so that the lowest possible yield strength was set. Subsequently, the support tube was machined (length 2500 mm, inner diameter 124 mm, outer diameter 132 mm). The support tube was positioned in the Mo target tube. This assembly was placed in a double-sided tool that enclosed this. In the area of the free ends of the support tube, the inner diameter of the closed tool was 133 mm. At both ends of the support tube, hydraulic rings sealed by plastic rings were connected. Subsequently, the tube was filled with water containing a corrosion inhibitor. The water pressure was raised to 450 bar within 20 seconds. This resulted in plastic deformation of the steel pipe and elastic deformation of the molybdenum pipe. After a holding time of 5 seconds, the pressure was lowered. The elastic recovery of the two materials led to a positive connection, taking into account the different moduli of elasticity and the yield points. Following hydroforming, the two free ends of the support tube were machined by welding and turning in accordance with the given PVD system connections.

Example 2:

Tungsten-blue oxide powder was reduced to W metal powder with a grain size of 4.1 μm in a one-step reduction process. In a closed rubber shower with an inside diameter of 260 mm, a steel mandrel with a diameter of 129 mm was positioned in the middle. In the space between the steel core and the rubber wall, the W metal powder was filled. The rubber hose was subsequently closed at its open end by means of a rubber cap. The sealed rubber tube was placed in a cold isostatic press and the powder compacted at a pressure of 210 MPa. The green compacts thus produced were sintered in an indirect sintering furnace at a temperature of 2300 ° C. The sintered density was 93.7% of the theoretical density.

In a subsequent process step, the tube segments were densified hot isostatically at a temperature of 185O ⁰ C and a pressure of 1950 bar with a holding time of 3 hours to a density of 99% of the theoretical density.

The pipe segments were machined to a length of 250.5 mm, an inner diameter of 133 mm and an outer diameter of 163 mm. The inside was machined so that a ripple with a wave height of 0.5 mm and a wavelength of 20 mm was set.

The support tube made of austenitic steel was soft annealed. Subsequently, the support tube was machined to a length of 2500 mm, an inner diameter of 124 mm and an outer diameter of 132 mm. 8 pieces of W-pipe segments were pushed onto the steel pipe, inserted in a double-sided tool and enclosed by this. In the area of the free ends of the support tube, the inner diameter of the closed tool was 133 mm. At the two ends of the support tube sealed hydraulic rings were connected via plastic rings. Subsequently, the tube was filled with water containing corrosion inhibitor. The water pressure was raised to 450 bar within 20 seconds. This resulted in plastic deformation of the steel tube and elastic deformation of the tungsten tube sections. After a holding time of 5 seconds, the pressure was lowered. The elastic recovery of the two materials led to a positive connection, taking into account the different moduli of elasticity and the yield points. Subsequent to the hydroforming, the free ends of the support tube were machined by welding and turning according to the given PVD system connections. Example 3:

From a Mo sheet with a thickness of 10 mm round blanks were made with a diameter of 330 mm by water jet cutting. These blanks were clamped in a rotationally symmetrical tool and shaped under local preheating with a burner to about 650-750 ° C by means of flow pressures in the shape of a pot. The finished pot height was 220 mm and wall thickness 7.5 mm. Subsequently, the bottom of the pot was cut off and the tube segment was machined by turning and grinding to the following dimensions: length of 200 mm, inner diameter of 136.8 mm and outer diameter of 147.0 mm. The support tube made of austenitic steel was soft annealed. Subsequently, the support tube was machined to a length of 1200 mm, an inner diameter of 126.4 mm and outer diameter of 136.3 mm. 5 pieces of Mo pipe segments were pushed onto the steel pipe, inserted into a double-sided tool that enclosed them. In the area of the free ends of the support tube, the inner diameter of the closed tool was 136.8 mm. At the two ends of the support tube sealed hydraulic rings were connected via plastic rings. Subsequently, the tube was filled with water containing corrosion inhibitor. The water pressure was raised to 450 bar within 20 seconds. This led to a plastic deformation of the steel tube and an elastic

Deformation of the molybdenum tube. After a holding time of 5 seconds, the pressure was lowered. The elastic recovery of the two materials led to a positive connection, taking into account the different moduli of elasticity and the yield points. Following hydroforming, the two free ends of the

Support tube processed according to the predetermined connections for the PVD system by welding and turning.

Claims

claims

1. A method for producing a pipe target comprising a pipe or pipe sections of the target material and a support tube, the support tube with the pipe or the pipe sections from the

Targetwerkstoff is joined by hydroforming.

2. The method according to claim 1, characterized in that the tube or pipe sections of the Targetwerkstoff and the support tube are placed in a mold, wherein the support tube in the pipe or in the

Pipe sections is positioned from the target material, the tube ends of the support tube are sealed by sealing stamp, and the support tube is filled with a pressure transmission medium, whereby an internal pressure builds up, which is chosen so high that the

Yield point of the support tube is exceeded and at least partially applies the support tube to the pipe or the pipe sections of the target material to form a joint surface.

3. The method according to claim 2 or 3, characterized in that the joining surface between the tube or the pipe sections of the Targetwerkstoff and the support tube is at least 20 area percent of the theoretically possible contact area.

4. The method according to any one of claims 1 to 3, characterized in that the pressure-transmitting medium is a liquid, preferably water with corrosion inhibitor, a water-oil emulsion or oil.

5. The method according to any one of claims 1 to 4, characterized in that the outer side of the support tube and / or the inside of the tube or pipe sections of the Targetwerkstoff is processed so that it has a wavy surface.

6. The method according to claim 5, characterized in that the wave height is in the range of 10 microns to 2 mm and the wavelength in the range of 15 microns to 100 mm.

7. The method according to any one of claims 1 to 6, characterized in that for the pipe or the pipe section from the Targetwerkstoff a

Refractory metal is used.

8. The method according to claim 7, characterized in that molybdenum is used for the pipe or the pipe section from the Targetwerkstoff.

9. The method according to any one of claims 1 to 8, characterized in that for the pipe or pipe sections from the target material extruded material having an oxygen content of less than 50 micrograms / g, a density greater than 99% of the theoretical density and a mean grain size transverse to the axial Direction smaller than 100 microns is used.

10. The method according to any one of claims 1 to 9, characterized in that a non-magnetic material is used for the support tube.

11.Verfahren according to claim 10, characterized in that for the

Support tube austenitic steel, a copper material, preferably Cu-Cr-Zr, or a titanium material is used.