JP2818206B2 - Sputtering target - Google Patents

Description

The present invention relates to a sputtering target used for forming a thin film such as an electrode wiring material of a semiconductor device, and more particularly, to a method for controlling the amount of particles generated during sputtering. The present invention relates to a sputtering target capable of significantly reducing the yield of a product by providing a thin film with few defects.

(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 type LSI. However, with high integration of LSI, polysilicon still has a large electric resistance, and thus delay in signal propagation has become a problem.

On the other hand, in recent years, in order to facilitate element formation by self-alignment, high melting point materials are desired for gate, source, and drain electrode materials, and a thin film forming technique made of a high melting point metal silicide compatible with a silicon gate process is promising. It has already been put to practical use for some products.

One effective method for forming such a high melting point metal silicide thin film for an electrode or wiring of a semiconductor device is a sputtering method.

This sputtering method is, for example, Ti, Mo, W, Zr, H
f, Nb, Ta or other high-melting metal and silicon are arranged in a mosaic pattern with a mosaic-type target, which is bombarded with argon ions to release the metal, and the released metal is deposited as a thin film on the substrate facing the target plate. Is the way. Therefore, the properties of the silicide thin film formed by such sputtering greatly depend on characteristics such as the composition and surface shape of the target material.

Such a conventional mosaic-type target is formed by processing high-purity single-crystal silicon and high-purity high-melting-point metal into, for example, a fan-like shape called a beam, and combining a plurality of those beams into a desired shape and shape. Manufactured by sizing.

In addition to the above-mentioned mosaic-type target, an alloy-like target made of a high-melting-point metal silicide obtained by reacting a high-melting-point metal with silicon has also been proposed. This conventional silicide target is prepared from a synthesized refractory metal silicide powder as a starting material, and is molded and vacuum-processed and sintered to prepare a silicide sintered body.
The obtained sintered body is obtained by forming the sintered body into a predetermined shape and dimensions by surface grinding or lathing.

(Problems to be Solved by the Invention) However, when a conventional sputtering target manufactured by the above-described machining is directly attached to a sputtering apparatus to form a silicide thin film by sputtering, fine particles are formed from the sputtering surface of the target in the process. Particles (particles) are inevitably generated,
There is a problem that these particles are mixed into the deposited silicide thin film. For this reason, the resistance of the formed electrode wiring is non-uniformly increased, and a short circuit is generated. In particular, as the degree of integration of the semiconductor device increases to 4M and 16M, the electrode wiring width further decreases and the wiring becomes longer, so that depending on the particle size of the particles mixed into the silicide thin film, the defect rate sharply increases. However, there is a problem that the yield of products is significantly reduced.

The present invention has been made in view of the above points,
It is an object of the present invention to provide a sputtering target capable of significantly reducing the amount of particles generated particularly during the initial stage of sputtering during the sputtering operation and greatly improving the product yield.

[Configuration of the invention]

(Means and Actions for Solving the Problems) A sputtering target according to the present invention is used for forming a thin film for manufacturing a semiconductor device or an electronic component element, and is a sputtering target containing a high melting point metal. At least the surface layer of the surface to be sputtered is characterized by being subjected to electrolytic polishing.

Further, the sputtering target is a mosaic target formed by integrally combining a high melting point metal piece and a silicon piece, or an alloy target formed into an alloy by using a high melting point metal silicide.

Further, refractory metals are Mo, W, Ti, Zr, Hf, Nb and
At least one metal selected from Ta is adopted.

The present inventor has conducted intensive studies to achieve the object of the present invention described above. As a result, particles generated from the target during sputtering are subjected to mechanical finishing such as grinding of a beam or alloy material constituting the target. It has been found that it is caused by a surface defect layer, a surface state, a residual stress, and the like formed at the time.

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, and hard and brittle materials such as high melting point metals, single crystal silicon, or silicon compounds are removed. In the case of grinding, granular chips scatter from the processing surface. As a cause of the scattering of the granular chips, a minute crack is generated on the processed surface due to the contact stress with the abrasive grains during grinding, and the shoulder portion of the crack is pushed up by rapid release of the stress after the abrasive grains pass,
This is because they are separated as fragments. For example, when processing a sputtering target made of a hard and brittle material, 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. Processing is proceeding by accumulation of micro-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 in which such a processing defect layer is present on the entire surface, the collision of ions in the plasma causes fine particles to be separated and separated from the target surface starting from the processing defect portion, and this becomes particles. It is mixed into the thin film.

The present inventor has conducted further studies based on the above findings, and as a result, it is possible to quickly and effectively remove the processing defect layer as described above by subjecting the surface layer of the sputtering target to electrolytic polishing. It has been found that the sputtering target has a surface layer that does not generate particles.

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

As the high melting point metal that is a component of the sputtering target according to the present invention, Mo, W, Ti, Zr, Hf, Nb and Ta
For example, a metal capable of forming a metal silicide thin film having a small specific resistance is used.

These metals are used alone or in combination of two or more.

Since these metals have low specific resistance and high corrosion resistance at high temperatures as compared with conventional electrode wiring materials, the use of the silicide for the electrode wiring of the semiconductor enables high-speed operation in the semiconductor device, In addition, there is an advantage that it is hardly susceptible to corrosion by chemicals and oxidation due to high-temperature treatment during semiconductor manufacturing.

The sputtering target to be the object of the present invention is a mosaic target formed by integrally combining a high-melting point metal piece made of Mo, W, Ti, Zr, Hf, Nb, Ta, or the like, and a silicon piece, or The present invention can be applied not only to an alloy target formed into an alloy by high-melting-point metal silicide but also to a metal target composed of a simple substance of the above-mentioned high-melting-point metal.

In the present invention, electrolytic polishing is performed on at least the surface of the sputtering target on which predetermined sputtering has been performed, on which sputtering is to be performed.

In this case, the electropolishing treatment method utilizes the dissolution phenomenon that occurs in the surface layer of the target body by immersing the target body or its element pieces in a tank filled with an electrolyte solution to form an anode, and then applying electricity. Then, a method of quickly and effectively removing a processing defect layer and a processing stress residual layer on the surface is adopted.

The electrolyte solution to be used varies depending on the type of components constituting the target such as a high melting point metal.In general, when the target base material is Mo, a mixed solution of methyl alcohol or distilled water and sulfuric acid, nitric acid, or hydrofluoric acid is used. used.
When the base material is W, a solution obtained by dissolving sodium hydroxide in distilled water, a mixed solution of glacial acetic acid and perchloric acid for Ti, Zr, and Hf, and a target having a high Si content are used. Use a mixed solution of methyl alcohol, butyl glycol and perchloric acid or a mixed solution of phosphoric acid, hydrofluoric acid and nitric acid.

Prior to the electrolytic polishing treatment, a degreasing treatment may be performed as necessary.

At the time of electrolytic polishing, the concentration of the electrolytic solution, the processing time, and the amount of polishing can be appropriately selected depending on the processing and grinding method and the type of the target, but as described above, the defect layer is not roughened without roughening the finished surface. In addition, it is important to set the processing conditions in a range where only the residual layer of the processing stress can be sufficiently removed.

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 in the processing defects in the target surface layer, the stress generated by the heat generated during sputtering increases, causing large cracks including some radiation cracks, and thereby increasing the particle generation layer. Therefore, it is desirable to remove as much as possible the processing defect layer of the target surface layer portion where the residual stress remains.

After performing the electropolishing treatment in this manner, it is necessary to completely remove the electrolyte solution components remaining on the target surface by performing water washing or the like according to an ordinary method to prevent corrosion of the target. It is.

As described above, according to the sputtering target of the present invention, since the surface layer of the target surface to be sputtered is subjected to electrolytic polishing, it is possible to quickly and effectively remove a processing defect layer generated by grinding or the like. is there. Therefore, the generation of particles emitted from the processing defect layer during sputtering is extremely small, so that a thin film with few defects is formed. As a result, the yield of products such as semiconductors in which a thin film is formed by sputtering can be significantly improved.

Conventionally, a processing defect layer generated by grinding or the like,
Some methods of removing the film by etching have been proposed. In this etching treatment, the target material is immersed in a solution that causes a corrosion reaction such as a mixed solution of nitric acid and hydrofluoric acid, and the processing defect layer on the surface is removed by a chemical reaction.

However, in the case of the etching process, since a chemical reaction is used, there is a disadvantage that the removal rate of the processing defect layer is low. In addition, when the alloy target formed by the mixed crystal of high melting point metal and silicon is etched, the silicon component is preferentially dissolved and removed due to the difference in the mixed crystal ratio, so that a step is formed on the target surface. Another problem is that a thin film having a predetermined composition cannot be formed.

On the other hand, in the electrolytic polishing treatment used in the present invention, the processing defect layer is dissolved and removed by an electrochemical reaction, so that the removal rate is extremely large and the processing can be performed in a short time. In addition, in the electrolytic polishing treatment, since both are dissolved and removed uniformly regardless of the mixed crystal ratio of the high melting point metal and silicon, a high quality thin film can be formed without generating a step on the target surface.

Embodiment Next, an embodiment of the present invention will be described more specifically with reference to the accompanying drawings.

Example 1 and Comparative Example 1 First, a sector-shaped Mo beam was cut out from a Mo ingot to a thickness of 15.4 mm, and using a surface grinder, the beam was cut with a grindstone (SD200N100VD1E) at a grinding wheel peripheral speed of 1100 m / min and a cutting speed. Grinding was performed to a thickness of 15 mm under the condition of 10 μm / min. Next, this beam was degreased, immersed in a mixed solution of distilled water and sulfuric acid, and subjected to electrolytic polishing to remove the ground surface by a thickness of 10 to 15 μm, and finally washed with water and dried.

On the other hand, a fan-shaped Si beam is cut out from a semi-crystalline Si ingot doped with a small amount of P to a thickness of 15.3 mm, and then a grinding wheel (SD400N75BA300) is used with a grinding wheel (SD400N75BA300).
Grinding was performed to a thickness of 15 mm under the conditions of 0 m / min and a cutting speed of 10 μm / min. Next, after degreasing this Si beam, it is immersed in a mixed solution of methyl alcohol, butyl glycol and perchloric acid to perform electrolytic polishing, and the ground surface is 10 to 15 μm in thickness.
After only removal, it was washed with water and dried.

The mosaic-type target 1 was formed by combining the fan-shaped Mo beam and the Si beam obtained as described above on the circumference as shown in FIG. The mosaic-type target 1 is formed into a substantially disc shape by alternately arranging fan-shaped Mo beams 2 and Si beams 3 on a circumference, and then integrally fixing them.

The mosaic-type target 1 thus obtained was set in a magnetron sputtering apparatus, and sputtering was performed by irradiating Ar ions, and a 100-inch poly-Si wafer having a diameter of 5 inches was coated with a silicide thin film having a thickness of 3 on the surface.
The operation of depositing at 000Å was performed continuously. Then, the amount of particles mixed in the thin film was measured, and the results are shown in FIG.

On the other hand, as Comparative Example 1, a molybdenum / silicon mosaic type target whose surface was merely finished by surface grinding was used, and a silicide thin film was 3,000 mm thick under the same conditions as in Example 1.
The amount of particles when deposited was measured, and the results are also shown in FIG.

As is clear from the results shown in FIG. 2, the molybdenum-silicon mosaic-type target of Example 1 in which the beam surface was subjected to electrolytic polishing was generated during sputtering because the processing defect layer was removed and the surface condition was extremely good. The amount of particles decreases rapidly immediately after the start of sputtering. Therefore, it is possible to efficiently manufacture a product having few defects, and it is possible to greatly improve the yield of the product.

On the other hand, in the case of the mosaic-type target of Comparative Example 1 in which only the surface grinding is performed and the electrolytic polishing is not performed, the reduction rate of the number of particles generated after the start of sputtering is small, so that the defect rate of the product is high, The yield tends to decrease.

Example 2 and Comparative Example 2 A molybdenum ingot cast as Example 2 was forged and rolled, and then subjected to lathe processing to form a disk material of φ250 mm × t15.4 mm. Next, the surface of the disc material was ground by a surface grinder and processed into a shape of φ250 mm × t15 mm. Next, electrolytic polishing was performed over the thickness of about 15 μm under the same conditions as in Example 1 to remove the processing defect layer and the processing strain layer on the surface, thereby obtaining a sputtering target.

The resulting sputtering target was used to irradiate Ar ions, and a Mo wafer was placed on a 5 inch diameter polysilicon wafer.
After depositing the thin film to a thickness of 3000 °, the amount of particles mixed in the thin film was measured, and the results shown in FIG. 2 were obtained.

On the other hand, as a comparative example 2, a Mo thin film having a thickness of 3000 mm was continuously formed under the same conditions as in example 2 under the same conditions as in example 2 with respect to a molybdenum sputtering target which was not subjected to electrolytic polishing while lathing and surface grinding were performed as in example 2. The amount of particles when the particles were deposited selectively was measured, and the results shown in FIG. 2 were obtained.

As apparent from the results shown in FIG.
Also in the sputtering target made of Mo, unlike Comparative Example 2, the processing defect layer and the like are removed from the surface layer thereof in advance, so that the amount of particles generated at the time of sputtering is sharply reduced. Therefore, a high-quality product can be manufactured from the initial operation of the sputtering apparatus, and the yield of the product can be greatly improved.

Further, in addition to the molybdenum-silicon mosaic-type targets or the targets made of molybdenum shown in Examples 1 and 2 and Comparative Examples 1 and 2, a simple substance of a high melting point metal such as W, Ti, Zr, Hf, Nb, Ta, or the like may be used. A comparison and test were also performed on a composite target or an alloy target formed in an alloy state by using the silicide thereof, with and without electrolytic polishing. A trend similar to the curve was confirmed.

Further, the electrolytic polishing method used in the present invention,
In addition to the simple electrolytic polishing method shown in the examples, a similar effect can be obtained by using an electrolytic lapping method combined with a mechanical polishing method, and a sputtering target processed by this method is also included in the scope of the present invention. It goes without saying that it is included.

〔The invention's effect〕

As described above, according to the sputtering target of the present invention, since the surface layer of the target surface to be sputtered is subjected to electrolytic polishing, it is possible to quickly and effectively remove a processing defect layer or the like generated by grinding or the like. Is possible. Therefore, generation of particles emitted from the processing defect layer or the like is extremely small, and a thin film with few defects is formed. As a result, the yield of products such as semiconductors in which a thin film is formed by sputtering can be significantly improved.

[Brief description of the drawings]

FIG. 1 is a perspective view showing the shape of a molybdenum-silicon mosaic target which is one embodiment of the sputtering target according to the present invention. FIG. 2 is a graph showing a change in the number of particles mixed in a thin film when a thin film is formed on a wafer using the sputtering target of the present invention, as compared with a conventional example. 1 .... Molybdenum-silicon mosaic type target, 2
…… Molybdenum beam, 3 …… Silicon beam.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-227771 (JP, A) JP-A-62-136564 (JP, A) JP-A-3-18020 (JP, A) JP-A-1- 215973 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) H01L 21/28-21/288 C23C 14/34

Claims (4)

(57) [Claims] 1. A sputtering target which is used for forming a thin film for manufacturing a semiconductor device or an electronic component element and contains a high melting point metal, wherein at least a surface layer of a surface to be sputtered of the sputtering target is subjected to electrolytic polishing. A sputtering target, comprising: 2. The sputtering target according to claim 1, wherein the sputtering target is a mosaic target formed by integrally combining a high melting point metal piece and a silicon piece. 3. The sputtering target according to claim 1, wherein the sputtering target is an alloy target formed of an alloy from a refractory metal silicide. 4. The sputtering target according to claim 1, wherein the refractory metal is at least one metal selected from Mo, W, Ti, Zr, Hf, Nb and Ta.