JPH03257158A - Sputtering target - Google Patents

Abstract

PURPOSE:To prevent the generation of particles from a target for forming the thin film of the high melting metal alloy of a semiconductor device during sputtering and to make improvement in product yield by removing the work defect layer generated in the surface part of the above-mentioned target at the time of machining. CONSTITUTION:The sintered body of a hard and brittle material, such as high melting metal alloy, is machined to a desired shape and size to obtain the target. The working unit is made small as compared with the distribution of material defects in order to fine the finish surface roughness of this target and to eliminate the work defect layer where cracks, dislodging holes, etc., exist. More specifically, the load per abrasive grain is decreased by a method for using the abrasive grains of a small and uniform grain size and a polisher having soft elasticity or viscoelasticity, etc., so that the stress induced in the material is lessened to a fracture stress value or below. For example, methods of successively smaller grain sizes, such as lapping, polishing, and mechanical polishing are successively executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a high melting point metal alloy sputtering target used for forming thin films such as electrode wiring materials of semiconductor devices.

(Prior Art) Polysilicon has conventionally been widely used as electrodes or interconnections of semiconductor devices, particularly as gate electrodes of MO8LSIs. However, as LSIs become more highly integrated, polysilicon has a large electrical resistance and signal propagation delays are becoming a problem.

On the other hand, in recent years, high melting point materials with low electrical resistance have been desired as materials for gate, source, and drain electrodes in order to facilitate device formation using Selfa Line, and high melting point metal alloys have been viewed as promising.

One of the effective methods for forming a high melting point metal alloy thin film for electrodes or wiring of such semiconductor devices is sputtering. The sputtering method is a method in which a target made of a high melting point metal alloy is bombarded with argon ions to release metal, and the released metal is deposited on a substrate facing the target plate. Therefore, the properties of a high melting point metal alloy film formed by sputtering are largely influenced by the properties of the target material.

Conventionally, such high-melting point metal alloy targets are produced by forming and vacuum sintering or pressure sintering an alloy sintered body using threatened alloy powder as a starting material, which is then machined into the desired shape and dimensions. Manufactured by processing (grinding).

(Problem U to be solved by the invention) However, when a high melting point metal alloy film is formed by sputtering using such a high melting point metal alloy target, fine particles are inevitably generated from the sputtering surface of the target. This often occurs and gets mixed into the refractory metal alloy film that is being deposited. The incorporation of such particles causes problems such as increasing the resistance of the electrode wiring and causing short-circuit defects. In particular, as the degree of integration increases from 4M to 16M, the electrode wiring width decreases, so the particles mixed into the deposited film as described above increase the short-circuit defect rate, resulting in a significant drop in product yield. There is.

The present invention has been made in view of the problems of the prior art described above, and makes it possible to produce high-quality high-melting point metal alloy thin films by significantly reducing the amount of particles generated from the target during sputtering operations. The aim is to provide a sputtering target that can dramatically improve product yield.

[Structure of the Invention] (Means and Effects for Solving the Problems) The sputtering target of the present invention is a sputtering target for a high melting point metal alloy used for forming a high melting point metal alloy thin film for manufacturing semiconductor devices. The sputtering target is characterized in that, at least on the surface thereof, a processing defect layer (fracture layer) consisting of minute cracks and missing portions generated during machining is substantially removed.

DETAILED DESCRIPTION OF THE INVENTION As a result of intensive research to achieve the above object, the present inventors have discovered that the generation of particles from the target during sputtering can be reduced by machining such as grinding a sintered body of a high-melting metal alloy. Surface defect layer and surface condition that occur during finishing,
It was discovered that this is caused by residual stress. That is, the conventional grinding finishing process is a processing method in which a workpiece is scraped off using hard abrasive grains of a grinding wheel rotating at high speed. In this method, T
When grinding a hard and brittle material such as an iW alloy sintered body, powder chips inevitably scatter from the machined surface. According to the findings of the present inventor, this is because micro-cracks occur on the ground surface due to the contact stress of the abrasive grains during grinding, and after the abrasive grains pass through, the shoulders of the cracks are pushed up by the sudden release of stress and become fragments. It is thought that it is generated by detachment. Normally, when processing hard and brittle materials, the cutting depth or load per abrasive grain is appropriately increased to the extent that cracks are included in the local stress field induced by the abrasive grain, and the material is processed by accumulating micro-fractures. is in progress.

Therefore, for example, in the case of a TiW alloy sintered body, a machining defect layer in which grinding marks, drop-off holes, microcracks, etc. are present is generated on the ground surface.

When sputtering is performed using a target having such a defect layer over its entire surface, fine particles are peeled off from the target surface starting from the defect portion due to the collision of ions in the plasma, and become the particles described above. The present invention was invented based on the above findings, and provides a high melting point metal alloy sputtering target used for forming a high melting point metal alloy thin film for manufacturing semiconductor devices, the target having at least a surface portion The basic feature is that there are virtually no processing defect layers such as microcracks or missing parts that occur due to mechanical processing.

The high melting point metal alloy is W, Mo, Ti or Ta.
It is composed of a combination of high melting point metals such as.

In order to fine the finished surface roughness and to substantially eliminate a processing defect layer in which cracks, drop-off holes, etc. exist, it is permissible to take care to make the processing unit smaller than the distribution of material defects. Specifically, the stress induced in the material is reduced by reducing the load per abrasive grain by using methods such as using well-aligned abrasive grains even if the grain size is small, or using a polisher with soft elasticity or viscoelasticity. must be below the breaking stress value.

Even in hard and brittle materials such as high melting point metal alloys, there are regions where the load is extremely small, where the material exhibits only plastic flow deformation and no cracks occur. Can be finished with a glossy surface.

Preferred examples of specific methods include lapping, which is used for the purpose of surface finishing, and boring, as well as mechanochemical boring, which is used for ultra-precision finishing.

However, it is actually difficult to directly finish a high-melting point metal alloy sintered body to the specified dimensions by the above-mentioned processing, and when efficient processing such as grinding is used, in order to remove the processing defect layer that has occurred, It is necessary to carry out the above-mentioned processing steps also under load.

In the above surface processing method, the abrasive grains used in the order of lapping, boring, and mechanochemical boring become smaller, so that the finished surface roughness becomes finer. By applying such a processing method to a target made of a high melting point metal alloy, the amount of particles generated can be significantly reduced. In other words, according to the findings of the present inventors, there is a correlation between the amount of particles generated and the surface roughness, and in order to suppress the generation of particles with a particle size that leads to defects in electrode wiring, it is necessary to improve the surface roughness of the machined surface. It is particularly preferable that the center line roughness Ra (center line roughness) is 0.05 μm or less.

(Example) Hereinafter, the structure and effects of the present invention will be explained in more detail with reference to Examples.

Kankitan 1 After cutting a TiW alloy containing 10% Ti by weight using a hot press into a size of 258 mm in diameter by wire electrical discharge machining, it was cut into a size of 258 mm in diameter using a chamber shaft rotary surface grinder, grinding wheel 5D270J55BW6, and grinding wheel circumference. Speed 1200m/min
, table rotation speed 12rμm, cutting speed 10μm/m
Grinding was carried out to a thickness of 6.35 mm under conditions of .

Next, the ground surface was lapped using a lens polisher for 60 hours with diamond abrasive grains of 15 μm and for 1° with 3 μm abrasive grains, and while the machining fluid attached to the lapping surface was removed using an ultrasonic cleaner, acetone degreasing was performed. Dry and finish.

The obtained machined surface was observed with a scanning electron microscope (SEM), and it was found that there were no remaining grinding marks or holes caused by the grinding process, and that there were a large number of holes caused by the deformation and destruction of the grinding abrasive grains. No microcracks were observed, confirming that the processing defect layer had been removed. In addition, a surface roughness measuring instrument (Ta
The roughness of the machined surface was measured using lysurf. The results are shown in Table 1. Note that the measurement results of the ground surface are also listed in Table 1 as comparative examples.

After setting this target in a magnetron sputtering device, sputtering is performed by Ar ion irradiation to form a TiW film on Po1y-8i at 300 OA.
Deposited. The amount of particles mixed into this film was measured, and the results are shown in Table 1. Note that the sputtering results on the ground surface are also listed in Table 1 as a comparative example. As is clear from the table, the amount of particles was significantly reduced, indicating that lapping can reduce the amount of particles generated during sputtering.

After grinding and lapping a TiW alloy sintered body with a diameter of 258 mm and containing 10% Ti by weight in the same manner as in Example 1, using 0.3 μm cerium oxide abrasive grains and an acrylic resin polisher. The target was polished for 10 hours under the conditions of a polisher pressure of 1 kg/cm 2 and a polisher of 10 m/min, and the processing liquid was removed by ultrasonic cleaning, followed by acetone degreasing and drying to finish the target.

As a result of SEM observation of the obtained processed surface, it was found that processing defect layers such as grinding marks, drop-off holes, and microcracks caused by the grinding process had completely disappeared, and the surface had been finished in a mirror-like state. Table 1 shows the measurement results of the surface roughness and residual stress of the machined surface. Compared to the ground surface shown as a comparative example, the surface unevenness is extremely small, and the plastic strain or elastic strain of the surface layer caused by grinding is very small. It had almost been removed.

Using this target, magnetron sputtering was performed to form a TiW film on Po1y-8i. The measurement results of the amount of particles mixed into this film are also listed in Table 1. As is clear from these results, it has been found that when the final finish is bolling, the particles generated from the target are significantly reduced due to the improved surface quality.

Example 3 A TiW alloy sintered body having a diameter of 258 mm and containing 10% Ti by weight was ground and lapped in the same manner as in Example 1, and then polished using 0.02 μm SiO2 powder and a cross polisher at a polisher pressure of 1 kg/ cm Positive rear speed 1
The target was subjected to mechanochemical boring processing for 20 hours under the conditions of 0 m/min, and after ultrasonic cleaning, acetone degreasing and drying were performed to finish the target.

As a result of SEM observation of the obtained processed surface, no processing defect layer caused by grinding was observed.

In addition, the surface roughness and residual stress of the machined surface are shown in Table 1.
The smoothness was extremely high compared to the ground surface, and the machined surface was in the same condition as an unstrained surface.

After magnetron sputtering was performed using this target to form a TiW film on Po1y-8i, the amount of particles mixed into the film was measured. As shown in Table 1, almost no particles were observed.
It was confirmed that by performing mechanochemical boriding processing as a final finish, it was possible to completely remove the processing defect layer and residual stress that cause particle generation.

It is possible to achieve a significant improvement in performance, and is extremely useful industrially.

Claims (1)

[Claims] 1. A sputtering target for a high melting point metal alloy used for forming a thin film of a high melting point metal alloy for manufacturing semiconductor devices, and processing defects such as micro cracks or missing parts that occur during machining in at least the surface portion of the sputtering target. A sputtering target characterized in that a layer (fracture layer) is substantially removed. 2. The sputtering target according to claim 1, wherein the surface roughness is Ra (center line roughness) of 0.05 μm or less. 3. The sputtering target according to claim 1, wherein the high melting point metal alloy is a W alloy based on W.