JPH11256322A - Metal silicide target material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new target material which can decrease the production of particles from the initial stage of use. SOLUTION: This target material has a structure comprising free silicon and a metal silicide which is substantially a compd. having >=2 atomic ratio Si/M of silicon to metal M wherein the M is tungsten or molybdenum. The target material has >=100% relative density and shows <=0.7 deg halfwidth of an MSi2 phase (101) peak in the X-ray diffraction intensity measurement. The target is obtd. by compacting and sintering a calcined material comprising high melting point silicide MSi2 and pure silicon Si or powders by pulverizing the calcined material, then, mechanically processing the sintered compact to adjust the surface roughness Ry of the sputtering face to <=1 μm and heat- treating the compact at >=800 deg.C and <=1250 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal silicide target used for forming an electrode or a wiring used in a semiconductor device and a method for manufacturing the same.

[0002]

2. Description of the Related Art With the recent high integration of LSIs,
Tungsten silicide or molybdenum silicide films are used as the electrodes and wirings. As a method for forming these silicide films, a sputtering method, a chemical vapor deposition method, and the like are used, and in particular, productivity of the film,
Sputtering is the mainstream because of its reproducibility and work safety. This sputtering method uses a target composed of tungsten and silicon to cause inert gas ions such as argon to collide with the target surface,
This is a method in which the emitted fine particles are formed as a thin film. As a specific target composition, in the case of stoichiometric metal silicide MSi ₂ , a large stress is applied to the formed metal silicide film, and therefore, a composition in which silicon is higher than the stoichiometric composition as long as the sheet resistance does not increase. Targets are usually used.

[0003] Further, as the above-mentioned target, in order to prevent the occurrence of cracks during use, to ensure uniformity and low resistance of the thin film, or to cause projections on the target surface due to local discharge during sputtering, In order to prevent generation of particles, a method of manufacturing a high-density target with few impurities has been studied. For example, Japanese Patent Application Laid-Open No. 61-145828 discloses that a high-purity high-melting-point metal powder and a high-purity silicon powder are mixed, pressed, heated and sintered to obtain a sintered body, and then melted with an electron beam to dissolve the silicide. A method for obtaining an article is disclosed. In addition, Japanese Unexamined Patent Publication No.
No. 141673 or Japanese Patent Application Laid-Open No. 61-141674
In Japanese Patent Application Laid-Open Publication No. H08-139, a high-density target is obtained by a method of mixing a molybdenum powder or a tungsten powder, molding and silicidation, pulverizing a pellet, and obtaining a sintered body by hot pressing.

[0004] As described in JP-A-63-219580, a high melting point metal powder such as molybdenum or tungsten and a silicon powder are subjected to a silicide reaction in vacuum to obtain a finer structure. A method of hot isostatic pressing of the calcined body has also been proposed. In addition, Tokuhei 6
As described in Japanese Patent No. 41629, focusing on the fact that the amount of carbon is related to the reduction of particles, after preparing a mixed powder of a metal powder and a silicon powder, a high vacuum is applied to reduce carbon and oxygen. Also disclosed is a method of adding a step of reducing carbon and oxygen by heating at a temperature. More recently, as described in JP-A-8-49068, a calcined body is heated from 1200 ° C. to 140 ° C. to improve the density.
There is disclosed a method in which sintering is performed at a high temperature and high pressure of 0 ° C. and 110 MPa or more to make the relative density 101% or more.

[0005]

The above-described high density, reduction of impurities and fine structure are effective methods for reducing particles of a molybdenum silicide or tungsten silicide target, respectively. However, the recent high integration of LSIs is remarkable, and the width of a thin film required for wiring and the like is becoming submicron, and a method other than the above-described conventional method for further reducing the generation of particles in fine devices has been developed. It has been demanded.

The present inventor has conducted various studies on the particle generation factors caused by the target, and found that they can be classified into three types according to the particle generation time. The first occurs throughout the life of the target, and this is due to the density of the target, the material such as the microstructure, and the like. In this regard, the present inventor has considered that the generation of particles generated throughout the target usage period can be achieved by miniaturizing the free Si phase found in the silicide target structure and avoiding dislocation concentration in the free Si phase by optimizing the sintering conditions. They have found that suppression is possible. The second occurs especially at the end of target use. As the target is used continuously, a film is deposited on the non-erosion portion of the target surface by reattachment of sputtered particles. Particles that have been separated and dropped at a certain point in time become particles. Thirdly, the occurrence is concentrated in the early stage of using the target. An object of the present invention is to provide a novel target material capable of reducing generation of particles from an early stage of use, paying particular attention to the third generation factor described above.

[0007]

The inventor of the present invention has pursued the cause of the generation of initial particles. For example, the surface of a sputtered surface is generally roughened to a predetermined size by a parallel polisher or the like, and then finished by a lap or the like. Will be At this time, if processing strain remains in the extreme surface layer part of the finished surface, completely different phases such as silicide compound and free silicon such as metal silicide target material exist, and in the case of brittle material, especially when ion bombardment during sputtering is applied At the same time, chipping and peeling of the target surface are likely to occur, which causes a large generation of initial particles. The present inventor has developed a target from which the residual strain on the surface has been removed.

That is, the present invention relates to a target material having an atomic ratio Si / M of silicon to metal M of 2 or more, metal M being tungsten or molybdenum, and having a structure substantially consisting of metal silicide as a compound and free silicon. Wherein the relative density, which is the ratio of the true density of the target material to the theoretical density calculated on the assumption that the target material is composed of stoichiometric high melting point silicide MSi ₂ and pure silicon Si, is 100% or more. And the half-width of the MSi ₂ phase (101) peak is 0.7 deg or less in the X-ray diffraction intensity measurement of the target material.
Get material.

The target of the present invention is preferably obtained by pressure-sintering a calcined body composed of high melting point silicide MSi ₂ and pure silicon Si or a powder obtained by pulverizing the calcined body. After machining the target to adjust the surface roughness of the sputtered surface to 1 μm or less by Ry,
It can be obtained by a method for manufacturing a metal silicide target material in which heat treatment is performed at a temperature of 0 ° C. or more and 1250 ° C. or less. The heat treatment is preferably performed under a high vacuum at a pressure lower than 10 minus 1 Pa in order to prevent surface deterioration.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventor used the half-width by X-ray diffraction intensity measurement as an index of residual strain to investigate the correlation between residual strain and particle generation. And MSi ₂
It has been found that when the half width of the phase (101) peak is 0.7 deg or less, it is effective in reducing initial particles.

In order to obtain a metal silicide target material as in the present invention, it is effective to carry out a working method that hardly causes residual strain on the surface, specifically, to carry out a mirror surface working so that Ry is 1 μm or less. is there. It is also effective to perform a heat treatment for removing residual strain after the processing.

When processing a target from a sintered body, for example, first, a raw material is indexed into a plate shape by slicing or the like, an outer peripheral shape is adjusted by a hollowing process, and then the target surface is adjusted to a predetermined plate thickness by a parallel polishing machine. Grinding. Finally, finishing is performed by lapping or the like. At this point, in order to make it difficult for residual strain to be generated on the surface of the target, it is indispensable to optimize the type of the grindstone and the processing conditions so as not to apply an excessive load during the processing.
Specifically, the finer the grain of the abrasive grain and the smaller the cut, the harder the strain remains. When such processing is performed, the roughness of the finished surface is inevitably reduced. That is, it can be said that the processing distortion does not remain as the surface becomes a mirror surface.

By the way, it is difficult to prevent the distortion from being added at all even if the mirror finishing is performed. Therefore, in addition to minimizing distortion during processing, it is also effective to remove the once applied distortion to reduce initial particles. Therefore, the strain removal by the heat treatment was examined. The present inventor conducted various investigations and found that 800 ° C
It was confirmed by X-ray diffraction measurement that the above heat treatment was able to remove the residual strain on the surface. On the other hand, if the temperature is increased to 1250 ° C. or more, the target material processed into a plate shape may warp.
It is appropriate to carry out at a temperature of at least 1250 ° C. The heat treatment is desirably performed in a vacuum so as not to form an oxide layer on the target surface. In the present invention, a target having a high density and a narrow half-value width in X-ray diffraction intensity measurement, that is, a reduced distortion can be obtained by the above-described method.

As a raw material composed of the above-mentioned metal silicide and free silicon, for example, a metal M powder and a silicon powder are blended stoichiometrically so that silicon is more than MSi ₂ which is a silicide composition. By heating, a calcined body in which metal silicide and free silicon are dispersed can be used, or a powder obtained by further pulverizing the calcined body can be used.

The silicide reaction referred to in the present invention is:
Molybdenum or tungsten reacts with silicon to form metal silicide. When the stoichiometric composition of MSi ₂ , that is, the atomic ratio Si / M between silicon and molybdenum or tungsten is adjusted so that silicon is more than ₂ , as in the present invention, silicide reaction causes a reaction with metal silicide. It becomes a tissue in which free silicon that did not exist is present. Therefore, in the present invention, the theoretical density is determined on the assumption that stoichiometric metal silicide MSi ₂ and pure silicon Si are present alone in the target structure. The specific method of calculation is as described later.

In the present invention, the theoretical density can be calculated as follows. Atomic ratio of silicon to tungsten Si / W =
For a target material of 2.75, the density and molecular weight of stoichiometric tungsten silicide WSi ₂ are as follows: Density 9.83 [g / cm ³ ] Molecular weight 240.022 [g / g-mol] The density and molecular weight of pure silicon are as follows. Density 2.33 [g / cm ³ ] Molecular weight 28.086 [g / g-mol]

The target material is substantially WSi ₂ : 1 [g]
−mol] and Si: only 0.75 [g-mol], the target material weight is (1 [g-mol] × 240.022 [g / g-mo].
l]) + (0.75 [g-mol] × 28.086 [g
/G-mol])=261.85 [g] The volume of the target material is (1 [g-mol] × 240.022 [g / g-mo]
l] /9.83 [g / cm ³ ]) + (0.75 [g-m
ol] × 28.086 [g / g-mol] /2.33
[G / cm ³ ]) = 33.458 [cm ³ ]

The density at this time is target material weight / target material volume = 7.803 [g / cm ³ ]. This is the theoretical density. On the other hand, the true density can be obtained by determining the volume of the target material by the Archimedes method and determining the weight by weighing the target material. The true density thus obtained is, for example, 7.90 [g / cm
³ ], the relative density is (true density × 100) / theoretical density = (7.90 [g / cm ³ ] × 100) /7.80
3 [g / cm ³ ] = 101.2%. In addition, in the present invention, the reason that the atomic ratio Si / M of silicon and the refractory metal exceeds 2 is that when Si / M is 2 or less, the film stress increases, and the problem of film peeling occurs. That's why. When used as an electrode or wiring of an LSI, if Si / M exceeds 4, there is a problem that the sheet resistance becomes high. Therefore, Si / M is preferably set to 4 or less.

[0019]

(Example 1) High-purity tungsten powder (purity 99.999% or more, average particle size 4.8 μm) and high-purity silicon powder (purity 99.999% or more, average particle size 2 μm)
m) was weighed to a compounding ratio of Si / W = 2.75 and mixed with a blender. The theoretical density at this time is 7.803 [g / cm ³ ] calculated by the above-described method. The mixed powder obtained by mixing was mixed at 1350 ° C. × 2 hr for 6 × 10 2
The silicidation reaction was performed under a high vacuum of less than minus square Pa to obtain a calcined body. This calcined body was placed in an argon atmosphere for 1 hour.
The powder is pulverized to a size of not more than 00 mesh (150 μm), and the pulverized powder is pressure-sintered by a hot isostatic press at a temperature of 1300 ° C. and a pressure of 500 atm. A relative density of 100% or more is confirmed by TEM observation of a free Si phase. A sintered body in which a region where no dislocations exist (1 μm square or more) was produced. A 300 mmφ tungsten silicide target material was obtained from the sintered body by machining. In addition, the surface was finished to a surface roughness Ry of 0.8 μm by using lapping for final finishing. This target material was subjected to a heat treatment under the conditions shown in Table 1 for the purpose of removing working strain. Heat treatment atmosphere is 10 minus 1
The adjustment was performed under reduced pressure from the power Pa.

Table 1 shows the results of X-ray diffraction intensity measurement (measurement of the half-width of the WSi ₂ (101) peak) of the obtained target material. For X-ray diffraction intensity measurement, Co-kα
Using a line, the X-ray incidence angle was measured at a low incidence angle (0.5 deg) to evaluate the outermost surface of the target. The obtained tungsten silicide target material was sputtered under the conditions shown in Table 2 so that the cumulative film thickness was 1 μm and 5 μm.
0.2 μm generated on 6 inch wafer at 0 μm
The above number of particles was measured. Table 1 shows the results.
Sample No. without heat treatment In the case of No. 4, the number of particles in the early stage of use is as many as 82, By removing the residual strain on the surface by performing a heat treatment at 800 ° C. or higher as in 1 to 3, the initial particles can be reduced. By the way, No. If the heat treatment temperature is too high as in 6, the surface oxidation is likely to occur during the heat treatment, and the surface roughness becomes coarse, thus offsetting the initial particle reduction effect.

[0021]

[0022]

(Example 2) High-purity molybdenum powder (purity of 99.999% or more, average particle size of 4.2 μm) and high-purity silicon powder (purity of 99.999% or more, average particle size of 2 μm)
m) was weighed to a mixing ratio of Si / Mo = 2.3 and mixed with a blender. The theoretical density at this time is 5.734 [g / cm ³ ] when calculated by the above-described method with the density of MoSi ₂ being 6.24 [g / cm ³ ]. The mixed powder thus obtained was subjected to a silicidation reaction at 1250 ° C. × 4 hr under a high vacuum of 6 × 10−2 Pa or less to obtain a calcined body. This calcined body is placed in an argon atmosphere for 100
Pulverize to mesh (150 μm) or less and pulverized powder
Pressure sintering by hot isostatic pressing under the conditions shown in
A molybdenum silicide target material having a diameter of 300 mm was obtained by machining. The heat treatment of this target material was performed under the conditions shown in Table 3. Heat treatment atmosphere is 10 minus 1
The adjustment was performed under reduced pressure from the power Pa.

As a result of measuring the X-ray diffraction intensity of the obtained target material, the true density and the relative density were determined in the same manner as in Example 1. Table 3 shows the results. Further, the obtained molybdenum silicide target material was sputtered under the conditions shown in Table 2 in the same manner as in Example 1 to produce a molybdenum silicide target material on a 6-inch wafer.
The number of particles of μm or more was measured. Table 3 shows the results.

[0025]

[0026]

According to the present invention, it is possible to suppress particles generated at the beginning of sputtering. Therefore, by using the target material of the present invention, the production yield of the semiconductor device or the reliability of the semiconductor device is improved, which is extremely industrially effective.

Claims (3)

[Claims] 1. A target material having an atomic ratio Si / M of silicon to metal M of 2 or more, wherein metal M is tungsten or molybdenum, and having a structure substantially composed of metal silicide as a compound and free silicon. A relative density which is a ratio of a true density of the target material to a theoretical density calculated on the assumption that the target material is composed of stoichiometric high melting point silicide MSi ₂ and pure silicon Si is 100% or more; A metal silicide target material characterized in that the half-width of the (101) peak of the MSi ₂ phase is 0.7 deg or less in the X-ray diffraction intensity measurement of the sputtering surface of the target material. 2. The surface roughness (R) of a sputtering surface of a target material.
2. The metal silicide target material according to claim 1, wherein y) is 1 μm or less. 3. A calcined body composed of high melting point silicide MSi ₂ and pure silicon Si or a powder obtained by pulverizing a calcined body is pressure-sintered, and then the obtained sintered body is machined into a target. A method for producing a metal silicide target material, comprising adjusting the surface roughness of a sputtered surface to 1 μm or less by Ry, and then performing a heat treatment at 800 ° C. or more and 1250 ° C. or less.