JP2970810B2 - Sputtering target, thin film, electrode or wiring, and semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a refractory metal-silicon mosaic target used for forming a thin film such as an electrode wiring material of a semiconductor device.
A refractory metal silicide target, or a sputtering target of any one of refractory metal targets made of a metal selected from the group consisting of Ti, Mo, W and Ta, and a thin film, an electrode or a wiring formed using the sputtering target, and these. The present invention relates to a semiconductor device using electrodes and wiring.

(Prior Art) Conventionally, polysilicon has been widely used as an electrode or wiring of a semiconductor device, particularly as a gate electrode of a MOS LSI. However, with the high integration of LSI, conventional semiconductor devices using polysilicon have large electric resistance,
Delay in signal propagation has become a problem. On the other hand, in recent years, various device forming techniques using self-alignment have been proposed, and in this case, a high melting point metal material is desired as a gate source and drain electrode material, and a high melting point metal silicide compatible with a silicon gate process. The thin film forming technology consisting of

One of the effective methods for forming such a high melting point metal silicide thin film for an electrode or a wiring of a semiconductor device is a sputtering method. The sputtering method is, for example, Ti, Mo, W or Ta
In this method, a metal is emitted by colliding argon ions with a mosaic-type target in which a high-melting metal and silicon are arranged in a mosaic pattern, and the emitted metal is deposited on a substrate facing the target plate. Therefore, the properties of the silicide film formed by such sputtering largely depend on the properties of the target material.

Conventional such mosaic targets have high purity,
Single-crystal silicon and high-purity high-melting-point metal are formed into, for example, a fan-shaped shape called a beam, and they are combined into a desired shape and size.

In addition to the mosaic-type targets described above,
A target comprising a high melting point metal silicide obtained by reacting a high melting point metal with silicon has also been proposed. Such a conventional silicide target is formed from a synthesized refractory metal silicide powder as a starting material and molded or sintered under vacuum or pressure to produce a silicide sintered body. In a predetermined shape and size.

(Problems to be Solved by the Invention) However, in the above-described conventional sputtering target, when a silicide film is formed by sputtering using the sputtering target, fine particles (particles) are inevitable from the sputtering surface of the target in the process. And this is mixed into the deposited silicide film. This causes problems such as an increase in the resistance of the formed electrode wiring and the occurrence of a short circuit. In particular, since the electrode wiring width further decreases as the integration degree of the semiconductor device increases to 4M and 16M,
Depending on the particle size of the particles mixed into the silicide film, the short-circuit defect rate is increased, so that there is a problem that the product yield is greatly reduced.

The present invention has been made in view of the above points,
An object of the present invention is to provide a sputtering target in which the amount of particles generated during sputtering, particularly at the beginning of sputtering, is significantly reduced, and the product yield is improved.

[Configuration of the invention]

SUMMARY OF THE INVENTION A sputtering target according to the present invention is a sputtering target used for forming a thin film for a semiconductor device, wherein at least a defect layer and a processing stress residual layer on a surface to be sputtered of the sputtering target are removed by an etching treatment. It is characterized by becoming.

Further, the present invention includes a thin film, an electrode or a wiring formed using the sputtering target.

Further, the present invention includes a semiconductor device using at least a part of the electrode or wiring formed in this way.

DETAILED DESCRIPTION OF THE INVENTION As a result of intensive research conducted by the present inventor to achieve the above-described object of the present invention, particles generated from a target during sputtering are generated by a machine such as grinding a beam constituting the target. It was found that it was caused by a surface defect layer, surface state, residual stress, and the like at the time of finishing.

In other words, grinding finishing is a processing method in which the workpiece is scraped off by the hard abrasive grains of a grinding wheel rotating at high speed. When processing, the granular chips scatter from the processing surface. In this method, a minute crack is generated on a processed surface due to contact stress with abrasive grains during grinding, and after passing through the abrasive grains, the shoulder portion of the crack is pushed up by rapid release of the stress and is separated as a fragment. In other words, when processing hard and brittle materials such as sputtering targets, the depth of cut or load per abrasive grain is appropriately increased so that cracks are included in the local stress field induced by the abrasive grains. The processing is advanced by the accumulation of fine crushing of such materials. Therefore, a processing defect layer inevitably occurs on the processed surface, in which grinding streaks, dropout holes, minute cracks, and the like are present. When sputtering is performed using a target having such a processing defect layer on the entire surface, collision of ions in plasma causes
Fine particles are separated and separated from the surface of the target starting from the processing defect portion and become particles, which are mixed into the formed film.

The present inventor has further studied based on the above findings, and as a result, by performing an etching treatment on the surface of the sputtering target, it is possible to quickly and effectively remove the processing defect layer as described above. And a sputtering target having a surface layer free of particles.

Therefore, the present invention is characterized in that a processing defect layer such as a grinding streak, a detachment hole, and a minute crack generated by machining on a surface portion of a sputtering target is removed by etching.

Examples of the sputtering target that is the object of the present invention include the above-described refractory metal-silicon mosaic target composed of silicon and a refractory metal such as Ti, Mo, W, or Ta, or a refractory metal silicide target. However, of course, the present invention can be applied to a metal target composed of a high melting point metal such as Ti, Mo, W or Ta alone.

In the present invention, at least the surface of the sputtering target subjected to the predetermined machining is subjected to etching. As an etching method in this case, wet etching is preferably used in terms of quickness and ease of operation. However, in the present invention, besides the wet etching, dry etching such as sputter etching or vapor phase chemical etching can be used, and is therefore included in the scope of the present invention.

To explain by taking wet etching as an example, the refractory metal constituting the target is, for example, (a) nitric acid-hydrofluoric acid solution or (b) nitric acid-hydrofluoric acid solution further added with phosphoric acid,
By etching with a hydrofluoric acid-based etching solution such as a solution containing at least one of a corrosion reaction control component such as acetic acid, the defect layer and the residual layer of processing stress can be removed without roughening the finished surface.

Further, the silicon constituting the target is, for example, a solution obtained by adding a corrosion reaction control component such as phosphoric acid to (a) a nitric acid-hydrofluoric acid solution, (b) a nitric acid-hydrofluoric acid solution,
(C) By etching with an etching solution such as a sulfuric acid-hydrogen peroxide solution or (d) an alkali solution such as a sodium hydroxide solution, it is possible to remove a defect layer and a residual layer of processing stress without roughening a finished surface. .

Further, in the case of treating a target of a high melting point metal silicide, for example, (a) a nitric acid-hydrofluoric acid solution or (b) a nitric acid-hydrofluoric acid solution further contains at least a corrosion reaction control component such as phosphoric acid or acetic acid. A hydrofluoric acid-based etching solution such as a solution containing one or more kinds is preferable.

Prior to the etching process, a degreasing process may be performed as necessary.

At the time of etching, the concentration of the etching solution,
The processing time and the etching amount can be appropriately selected depending on the grinding method and the type of the target. However, as described above, the defect layer and the processing stress residual layer can be sufficiently removed without roughening the finished surface. It is important that

By the way, in sputtering by Ar ion irradiation,
The point of impact of the ions is a high stress field and is exposed to high temperatures. Therefore, if residual stress remains on the target surface layer, the stress generated by the heat generated during sputtering increases, causing large cracks including some radiation cracks, thereby increasing the amount of particles generated. Therefore, it is desirable to completely remove the target surface layer portion where the residual stress remains.

After etching in this manner, it is necessary to completely remove the etching solution components remaining on the target surface by washing with water or the like according to a conventional method. Further, if necessary, a surface oxide by etching which may be formed on the target surface can be removed.

(Example) Example 1 A Mo beam was cut out from a Mo ingot to a thickness of 15.4 mm, and was used as a grinding wheel (SD200N100VD1E) using a surface grinder.
Grinding was performed to a thickness of 15 mm at a grinding wheel peripheral speed of 1100 m / min and a cutting speed of 10 μm / min. After degreased, the beam was immersed in a mixed acid of phosphoric acid-nitric acid-acetic acid-hydrofluoric acid (volume ratio: 5: 2: 2: 1) to remove the surface layer by 5 to 15 μm. Immediately after the etching, the substrate was washed with water (5 to 10 minutes), dried and finished.

The Si beam is cut out from the Si ingot to a thickness of 15.3 mm, and using a surface grinder, with a grinding wheel (SD400N75BA3.0), a thickness of 15 mm with a grinding wheel peripheral speed of 1100 m / min and a cutting speed of 10 μm / min.
mm. After degreased, this beam was immersed in a mixed acid of phosphoric acid, hydrofluoric acid and nitric acid (volume ratio of 5: 5: 2), and the surface layer was
2525 μm was removed. Immediately after etching, wash with water (5
~ 10 minutes), dried and finished.

A molybdenum-silicon mosaic target combining the above beams was set in a magnetron sputtering apparatus. FIG. 1 is a perspective view of a molybdenum-silicon mosaic target 1 in this case, and shows a state in which molybdenum 2 and silicon 3 are alternately combined.

The molybdenum-silicon mosaic-type target thus obtained was subjected to sputtering by Ar ion irradiation to deposit a 3000 μm silicide film on a 5-inch diameter Poly-Si wafer.

The amount of particles mixed in the film was measured (Example 1), and the results are shown in FIG. Further, as a comparative example, the amount of particles when a molybdenum-silicon mosaic type target finished by grinding was deposited at 3000 ° under the above conditions was measured (Comparative Example 1), and the results are also shown in FIG.

Further, FIGS. 3 and 4 are micrographs (SEM) showing the surface state of the Si beam, and FIG. 3 is the surface state immediately after the above-mentioned grinding, while FIG. 4 is the state after the etching process. This shows the surface condition. 5 and 6 are micrographs (SE) showing the surface state of the Mo beam.
M), and FIG. 5 shows the surface state immediately after the above-mentioned grinding, while FIG. 6 shows the surface state after the etching treatment.

As is clear from FIGS. 2 to 7, the molybdenum-silicon mosaic target whose beam surface has been etched has an extremely good surface state, and the amount of particles generated during sputtering is significantly reduced.
The effect is enormous.

Example 2 6.5 mm thick tungsten silicide (WSi _2.5 ) produced by hot pressing was 258 mm in diameter by wire electric discharge machining.
After cutting to the size of the above, using a vertical axis rotary surface grinder, the grinding wheel peripheral speed 1200m / min with a grinding wheel (SD270J155BW6),
Thickness 6 at table rotation speed 12 rpm, cutting speed 10 μm / min
mm. After the target was degreased with acetone, it was immersed in a mixed acid of hydrofluoric acid-nitric acid-phosphoric acid (volume ratio: 5: 2: 5) to remove the surface layer by an average of 10 μm. Immediately after etching, they were washed with water, dried and finished.

After the tungsten silicide target subjected to the etching process was set in a magnetron sputtering apparatus, sputtering was performed by irradiating Ar ions to deposit a 3000 μm silicide film on a 5-inch diameter Poly-Si wafer.

The amount of particles mixed into the film was measured, and the results are shown in Table 1. Further, as Comparative Example 2, the amount of particles was measured when a tungsten silicide target finished by grinding was deposited at 3,000 mm under the above conditions,
The results are shown in Table 1.

As is clear from Table 1, the molybdenum-silicon mosaic target having its beam surface etched has an extremely good surface condition, the amount of particles generated during sputtering is greatly reduced, and the effect is remarkable. It is.

Example 3 After cutting molybdenum silicide (MoSi _2.5 ) having a thickness of 6.5 mm produced by hot pressing into a size of 258 mm in diameter by wire electric discharge machining, using a vertical axis rotary surface grinder, a grindstone (SD270J155BW6). 6 mm thickness under the conditions of a grinding wheel peripheral speed of 1200 m / min, a table rotation speed of 12 rpm, and a cutting speed of 10 μm / min.
Grinding up to. After degreasing this target with acetone, phosphoric acid-nitric acid-hydrofluoric acid-acetic acid (volume ratio is 5: 2: 2:
It was immersed in the mixed acid of 1) to remove the surface layer by an average of 15 μm.
Immediately after etching, they were washed with water, dried and finished.

After the molybdenum silicide target subjected to the etching treatment was set in a magnetron sputtering apparatus, sputtering was performed by irradiating Ar ions to deposit a 3000-μm silicide film on a 5-inch diameter Poly-Si wafer.

The amount of particles mixed into the film was measured, and the results are shown in Table 1. Further, as Comparative Example 3, the amount of particles was measured when a tungsten silicide target finished by grinding was deposited at 3,000 mm under the above conditions,
The results are shown in Table 1.

As is clear from Table 1, the molybdenum-silicon mosaic target having its beam surface etched has an extremely good surface condition, the amount of particles generated during sputtering is greatly reduced, and the effect is remarkable. It is.

〔The invention's effect〕

As described above, according to the present invention, since a processing defect layer and a residual stress generated when the sputtering target is finished by grinding are removed by etching, the amount of particles generated from the target during sputtering is greatly reduced. Can be reduced.

Therefore, if the sputtering target of the present invention is used as a target, a great improvement in product yield can be expected, and this is extremely industrially advantageous.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a form of a molybdenum-silicon mosaic type target according to an embodiment of the present invention, FIG. 2 is a graph showing a change in the amount of particles present on a wafer, and FIGS. 5 is an SEM micrograph showing a state of a metal structure on a target surface. 1 .... Molybdenum-silicon mosaic type target, 2
…… Molybdenum beam, 3 …… Silicon beam.

Claims (5)

(57) [Claims] 1. A refractory metal-silicon mosaic target, a refractory metal silicide target, or a refractory metal target made of a metal selected from the group consisting of Ti, Mo, W and Ta used for forming a thin film for a semiconductor device. The sputtering target according to any one of the above, wherein a defect layer and a processing stress residual layer on at least a surface to be sputtered of the sputtering target are removed by an etching treatment. 2. The sputtering target according to claim 1, wherein the etching process is performed by a wet etching process. 3. A thin film formed by using the sputtering target according to claim 1. 4. An electrode or a wiring formed by using the sputtering target according to claim 1. 5. A semiconductor device using the electrode or wiring according to claim 4 for at least a part thereof.