JPH0641629B2 - Sputtering target and method for manufacturing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a sputtering target and a method for manufacturing the same, and more particularly to a high-density, high-quality sputtering target used for forming thin films of electrodes and wiring materials for semiconductor devices, and a method for manufacturing the same.

BACKGROUND ART Sputtering is an effective method for forming high-resolution metal silicide thin films for electrodes or wiring in semiconductor devices. Sputtering is a method that excels in mass productivity and film formation safety. It involves bombarding a metal silicide disk-shaped target with argon ions to release the target's constituent metals, which are then deposited as a thin film on a substrate facing the target. Therefore, the properties of the silicide thin film formed by sputtering are greatly influenced by the characteristics of the target.

Due to the increasing integration and miniaturization of semiconductor elements, there is a strong demand for sputtering targets used in forming these high-isotope metal silicide thin films to reduce the amount of particles (fine particles) generated. This is because very fine particles of about 0.2 to 10 μm generated from the target during sputtering contaminate the thin film being deposited, causing defects such as short circuits between wirings and open wiring after the circuit is formed, resulting in serious problems such as a significant decrease in product yield.

Conventionally, various manufacturing methods such as those described below have been proposed as methods for making the structure of a target finer and densifying it in order to reduce the amount of particles generated from the target.

For example, in Japanese Patent Laid-Open No. 61-179534, a method for forming a sintered body of a high-separation metal (M) component and a Si component by melting Si
It is disclosed that a high density target can be obtained by impregnating a continuous silicon matrix with spherical or ellipsoidal MS particles having a particle size of 5 to 500 μm.
The structure is one in which _i2 is dispersed, and the impurity content of carbon and oxygen is 50 ppm or less.

On the other hand, Japanese Patent Application Laid-Open No. 63-219580 discloses a method of obtaining a high-density target by a method in which a mixed powder of a high-isotope metal (M) and Si is subjected to a silicide reaction in a high vacuum to form a pre-sintered body, and then hot isostatically pressed and sintered. In this case, a fine structure is obtained in which the maximum grain size of _MSi2 is 20 μm or less and the maximum grain size of free Si is 50 μm or less. This target has fine _MSi2 particles and free Si particles.
The target has a mixed structure in which particles and silicon dioxide particles are dispersed in each other, and the oxygen content is set to 200 ppm or less. Since the oxygen content is kept low using this target, it is possible to reduce the sheet resistance of the formed film.

Furthermore, in Japanese Patent Laid-Open No. 63-179061 or Japanese Patent Laid-Open No. 64-39374, a high-separation metal (M) and S
The mixed powder of i is subjected to a silicide reaction in a high vacuum to form a sintered body, which is then crushed, and a silicide powder for adjusting the composition is added and hot-pressed for sintering to form a high-density Si
We have obtained a target that suppresses aggregation.

However, in the case of the method of impregnating the pre-sintered body with molten Si, the use of molten Si significantly reduces the content of impurities such as carbon and oxygen, resulting in a high-density target; however, the inventors have discovered that, because the Si impregnated into the pre-sintered body exists continuously to form a matrix, and because Si impregnates large voids present in the pre-sintered body to form coarse Si portions, the Si, which is weaker in strength than the metal silicide, is damaged by thermal stress generated during sputtering, and further, because the Si is continuously present, the strength of the target as a whole is still insufficient, resulting in the metal silicide falling off and the generation of a great number of particles.

Furthermore, the inventors have discovered that in the case of a method in which a pre-sintered body is formed using crushed Si powder and then the pre-sintered body is press-sintered as is without being crushed, although a high-density target with a fine structure is obtained, carbon that has been mixed in and contaminated during the Si crushing process is not removed and remains in the target, so that in carbon-rich areas during sputtering, sputtered particles do not scatter sufficiently, inducing the generation of particles, and the carbon parts that have been incorporated into the film have poor etching properties, causing etching residues and broken wiring.

Furthermore, the inventors have discovered that in the case of a method in which a sintered body is formed using crushed Si powder, the sintered body is crushed, and silicide powder for composition adjustment is added, followed by hot press sintering, a fine-structured, high-density target is obtained, but the two crushing steps increase the amount of carbon contamination of the raw material and also increase the amount of oxygen mixed into the raw material, resulting in a large number of particles being generated, and the oxygen taken into the film increases the resistance.

On the other hand, even in the case of a high-density target with a density ratio of 99% or more, the inventors have confirmed through experiments that the amount of particles generated increases due to the influence of certain impurities, and that the number of defective products increases sharply when forming a wiring pattern by etching in film formation.

Conventionally, sputtering targets of this type have generally been manufactured by a powder sintering method, focusing on the ease of controlling the composition of the silicide film to be formed. That is, conventional metal silicide targets are manufactured by a method in which a metal silicide (hereinafter referred to as _MSi2 ) obtained by reacting and synthesizing a metal powder (M) such as tungsten or molybdenum with a silicon powder (Si) is hot-pressed or hot isostatically pressed together with Si (see Japanese Patent Application Laid-Open No. 61-141673).
No. 61-141674, Japanese Patent Application Laid-Open No. 1983-141674
This is obtained by a method of impregnating a silicide pre-sintered body with Si (Japanese Patent Laid-Open No. 61-58866, etc.).

However, in the former method of the above-mentioned conventional methods, since a sintered body is produced by adding Si powder to the synthetic _MSi2 powder, for example, the volume fraction of the Si phase is in the range of 8% to 25% in a sintered body having a composition of _MSi2.2 to _MSi2.9 .
Therefore, the Si phase is distributed throughout the angular _{MSi2 particles} obtained by milling.
It is not always easy to distribute the phases even by pressure sintering, resulting in a target with a non-uniform structure with defects such as agglomerates of _MSi2 with different sizes and the local presence of Si phases.

On the other hand, the melting point of the _MSi2 phase varies greatly depending on the type of metal M. For example, _WSi2 , _MoSi2 , _TiSi2 , Ta
The melting points of _Si2 are 2165°C, 2030°C, and 15°C, respectively.
The melting points are 40°C and 2200°C. Because the _MSi2 phase and the Si phase, which have such vastly different melting points, are pressure-sintered below the eutectic temperature, sintering does not proceed between the thermally stable _MSi2 particles, and as a result, the bond strength between the particles is weak and prone to fracture, resulting in pores remaining and insufficient densification.

When a silicide film is formed by sputtering using such a target, the bonds between particles are broken by the irradiation energy of Ar ions during sputtering, and the sputtering surface of the target is broken and chipped from the defects, generating particles.

In particular, in high density integrated circuits, the degree of integration is 4 Meg
As the density increases from 1.0 to 16 Mega, the electrode width and wiring spacing become finer, and therefore particles mixed into the deposited film as described above will cause a rapid decrease in product yield.

On the other hand, in the latter conventional method described above, the composition of the target is controlled by impregnating a silicide pre-sintered body controlled to a predetermined density with molten Si.
_MSi2 is synthesized by the silicide reaction between M powder and Si powder to produce a pre-sintered body of a predetermined density, or M
When using _Si2 powder to create a pre-sintered body of a predetermined density by sintering the press-molded body, it is very difficult to obtain a target of the target composition because the density varies depending on the processing temperature, time, and pressing pressure.

Furthermore, according to the findings of the present inventors, the MSi ₂
Since high purity products are generally used for the Si and the MSi ₂ phases, impurities do not diffuse and gather at the boundary between the MSi ₂ and the Si phases of the target.
i The interfacial bonding strength between _{the two} phases is weak.

Furthermore, _there is a problem that the difference _in electrical resistance between the MSi ₂ phase and the Si phase is very large, which makes the sputtering operation unstable.
The electrical resistivity of TiSi ₂ , TiSi ₂ , and TaSi ₂ is 7
On the other hand, the resistivity is small, at 0, 100, 16, and 45 μΩ cm.
The resistivity of the phase is extremely large at 2.3×10 ¹⁰ μΩ·cm.
Furthermore, since there is no interfacial layer at the boundary between the _MSi2 phase and the Si phase, the electrical resistance changes abruptly at the boundary. In particular, the structure of the target produced by the latter method is such that the high-resistivity Si phase and the low-resistivity _MSi2 phase are in direct contact with each other.

Therefore, when sputtering is performed using such a target, dielectric breakdown between the _MSi2 phase and the Si phase inevitably occurs above a certain voltage, causing a sudden current flow. In other words, when the voltage exceeds a certain level, a discharge occurs, causing the _MSi2 particles or parts of the Si phase, which have weak interfacial strength, to fall off and become particles.

The present invention has been made in consideration of the above points, and an object of the present invention is to provide a high-quality sputtering target that can substantially prevent particle generation and form a high-quality thin film, as well as a method for manufacturing the same.

DISCLOSURE OF THE INVENTION The sputtering target according to the present invention has a fine mixed structure in which metal silicides (stoichiometric composition: _MSi2 , where M is a metal) are linked in a chain form to form a metal silicide phase, and silicon particles are linked together to form a silicon phase that is discontinuously present in the gaps between the metal silicide phase, and the carbon content is 10
It is characterized by being 0 ppm or less.

Furthermore, within 1 ^mm2 of the mixed tissue cross section, the particle size is 0.5 to 30 μm.
There are 400 to 400 × 10 ⁴ metal silicides of Si
The maximum particle size is 30 μm or less.

The average particle size of the metal silicide is 2 to 15 μm.
The average particle size of the silicon is 2 to 10 μm.

The particle diameter here refers to the diameter of the smallest circle circumscribing the particle.

Furthermore, the density ratio of the target is set to 99% or more, and the oxygen content is set to 150 ppm or less.

The metal (M) of the metal silicide is tungsten, molybdenum, titanium, zirconium, hafnium, niobium,
The metal is at least one selected from the group consisting of tantalum, vanadium, cobalt, chromium and nickel.

It is also preferable to form an interface layer at the boundary between the metal silicide and the silicon phase. In this case, the thickness of the interface layer is 100 to 1000 μm.
It is recommended to set it to 0000 Å.

The silicon phase contains at least one element selected from the group consisting of boron, phosphorus, antimony and arsenic, and unavoidable elements, and has an electrical resistivity of 0.01 to 100 Ω·
cm.

Furthermore, the method for producing a sputtering target according to the present invention is a method for producing a metal silicide (stoichiometric composition: MSi ₂ , but M
is a metal) are linked in a chain to form a metal silicide phase,
A method for producing a sputtering target having a fine mixed structure in which a silicon phase formed by bonding silicon particles exists discontinuously in gaps between the metal silicide phase, and having a carbon content of 100 ppm or less, includes the steps of: I. preparing a mixed powder by mixing a metal powder (M) and a silicon powder (Si) so that the Si/M atomic ratio is 2.0 to 4.0; II. filling the mixed powder into a molding die and heating it at a low temperature in a high vacuum to reduce carbon and oxygen; III. heating the mixed powder in a high vacuum under low pressure to synthesize and sinter a metal silicide; and IV. heating to a temperature just below the eutectic temperature in a high vacuum or in an inert gas atmosphere under high pressure to densify the mixture.

It is also preferable to use high-purity metal powder having a maximum particle size of 10 μm or less as the metal powder (M), and high-purity silicon powder having a maximum particle size of 30 μm or less as the silicon powder (Si).

The method is also characterized in that a mixed powder of metal powder and silicon powder is subjected to reactive melt sintering, thereby simultaneously carrying out silicide synthesis, sintering, and densification.

Furthermore, the reactive melt sintering is preferably carried out using a hot pressing method or a hot isostatic pressing method.

The present inventors have analyzed the causes of particle generation in metal silicide targets made of sintered alloys from various angles, and have completed the present invention based on the findings obtained from the analysis. In other words, based on the judgment that particles in high-melting-point metal silicide targets manufactured by the powder sintering method in the past were generated by abnormal discharge occurring in pores (vacancies) present in the target, which caused the surrounding areas of the pores to become damaged and induce particles, in order to minimize the number of pores,
As mentioned above, various efforts have been made to increase the density of the target.

However, the present inventors have thoroughly investigated the source of particles in high-melting-point metal silicide targets and discovered that, in addition to particles caused by pores, the source is the loss of eroded Si portions due to the action of thermal stress, and the detachment of the _MSi2 phase due to the difference in sputtering rate between the _MSi2 phase and the Si phase. That is, since the target surface, which is heated by continuous irradiation with high-speed Ar ions, is cooled from the backside, the target surface is subjected to thermal stress generated by the temperature difference in the thickness direction and thermal deformation of the target, and as a result, the Si phase, which is weaker in strength than the _MSi2 phase, is destroyed, and the detached pieces become particles. In particular, S
The erosion surface of the i-phase is a smooth MSi
Compared to _{the two-} phase structure, the unevenness is severe, and protruding portions are easily chipped off by the action of thermal stress or fluctuating stress generated during the sputtering cycle, making it prone to particle generation.
Furthermore, since the Si phase is preferentially eroded by sputtering compared to the MSi2 _phase , when the _MSi2 phase is present in a continuous Si phase, the binding force of the _MSi2 phase decreases as the Si phase erodes, and single or multiple bonded _MSi2 phases fall off to become particles.

Therefore, the present inventors have found that by refining the Si phase, which is easily broken, and by forming a mixed structure in which fine _MSi2 particles are linked in a chain form and Si is present discontinuously in the gaps between the particles, it is possible to substantially suppress the loss of eroded Si portions due to the action of thermal stress and the generation of particles due to the dropout of the _MSi2 phase due to the difference in sputtering rates between the _MSi2 phase and the Si phase.

In addition, the inventors have investigated other particle sources, such as:
The focus was on the carbon that had been mixed into the target. After the sputtering operation, the eroded surface of the target was observed under magnification, and it was found that the carbon-contaminated areas did not disperse well but remained as protrusions on the eroded surface.
As a result, they discovered that the plasma discharge in that area became unstable, causing repeated abnormal discharges and resulting in the generation of particles.

Furthermore, the inventors have experimentally confirmed that the amount of carbon contained in the target significantly affects the etching properties of a silicide thin film formed by sputtering. Carbon easily combines with silicon to form SiC, which has high electrical insulation properties. The generation of SiC and its incorporation into the deposited film rapidly reduces the etching properties of the film. Specifically, when etching a substrate on which a thin film has been formed to form a circuit pattern for an integrated circuit (IC), a photoresist-coated substrate is exposed to a circuit pattern using an exposure device and then developed with a specified chemical. This results in a significant increase in the rate of SiC remaining as residue. This leads to a rapid increase in the incidence of circuit pattern defects and circuit breaks.

Furthermore, the carbon film mixed in as particles in the silicide film has a different optical reflectance compared to other regions and is easily exposed to light, which results in the formation of regions with locally different optical reflectance on the film surface, making it difficult to form uniform, high-precision circuit patterns.

Furthermore, the inventors have identified other particle sources, such as:
The present inventors have focused on the protrusions occurring in the MSi ₂ phase and the Si phase. Specifically, the erosion surface of a metal silicide target manufactured by a conventional manufacturing method was observed under a scanning electron microscope (SEM), and the results are shown in FIGS. 11A-11B and 12.
As shown in Figures 12A to 12B, it was found that the coarse _MSi2 phase and Si phase have many minute protrusions 3, and it was discovered that there is a close relationship between these protrusions 3 and the particles that are generated.

Further investigation revealed that the protrusions could be reduced by reducing the grain size of the MSi ₂ phase and Si phase in the target. In particular, when the maximum grain size of the MSi ₂ phase was 10 μm or less, and when the maximum grain size of the Si phase was 10 μm or less,
It has been found that the generation of particles can be substantially suppressed by setting the maximum particle size of the phase to 20 μm or less.

Furthermore, the present inventors have conducted extensive research into obtaining a target having a fine structure, a low carbon content, and a high density, and as a result have found that a mixed powder of fine M powder and Si powder is filled into a molding die, and after heating and holding it in a high vacuum, a silicide reaction is carried out under low pressure to synthesize a metal silicide, and then sintered under high pressure, whereby S is produced at a temperature lower than 1300°C, at which Si volatilization becomes significant.
The carbon and oxygen on the i surface react to form CO or _CO2 , reducing the carbon and oxygen content. The oxygen on the Si surface gasifies to SiO or _SiO2 , reducing the oxygen content. All of the metal (M) becomes fine _MSi2 . The fine _MSi2 bonds in a chain shape, filling the gaps between them with S.
The inventors have found that a mixed structure in which i exists discontinuously can be obtained, and that the elimination of pores and densification are promoted at a temperature just below the eutectic temperature, and have completed the present invention.

Furthermore, boron (B) is added to the boundary between the _MSi2 phase and the Si phase.
It was discovered that particle reduction can also be achieved by providing an interface layer containing at least one element selected from the group consisting of phosphorus (P), antimony (Sb) and arsenic (As) and unavoidable elements, thereby strengthening the bonding force between the phases and preventing a sudden change in electrical resistance.

Here, the metals (M) constituting the target include molybdenum (Mo), tungsten (W), titanium (Ti), zirconium (Zr), hafnium (H
Metals capable of forming a metal silicide thin film with low resistivity, such as niobium (Nb), tantalum (Ta), vanadium (V), cobalt (Co), chromium (Cr), and nickel (Ni), can be used alone or in combination of two or more kinds, but high-melting point metals such as Mo, W, Ti, Zr, Hf, Nb, and Ta are particularly preferred.

Compared to conventional electrode wiring materials, these metals have lower resistivity and higher corrosion resistance at high temperatures. Therefore, when their silicides are used for semiconductor electrode wiring, it becomes possible to increase the speed of calculations in semiconductor devices. In addition, they have the advantage of being less susceptible to corrosion by chemicals and oxidation due to high-temperature processing during semiconductor manufacturing.

The sputtering target according to the present invention has a mixed structure in which 400 to 400 x ¹⁰⁴ _MSi2 phases with a grain size of 0.5 to 30 μm are uniformly present within 1 ^mm2 of the mixed structure cross section by controlling three factors: grain size of the raw material powder, heating temperature, and pressing pressure.
The resulting structure is a fine one in which _{the two} phases and a silicon phase having an average particle size of 2 to 10 μm are dispersed.

Furthermore, elements such as B, P, Sb, As and unavoidable elements such as Fe, Ni, Cr, and Al contained in the Si raw material diffuse and migrate to the boundary between the _MSi2 phase and the Si phase during silicide synthesis, forming an interface layer and strengthening the interfacial bonding strength between the two.

The present invention was completed based on the above findings.

The configuration of the present invention will be described in further detail below.

When a mixed powder of M and Si is heated under an appropriate pressure,
Si softens and reacts with M to form granular _MSi2 , and the heat generated by the formation of _MSi2 locally raises the temperature at the contact points between M and Si, further softening the area. As a result, _MSi2 particles aggregate on the surface and around the _MSi2 particles, forming a chain of granular _MSi2 . If _MSi2 were used alone, Si with a high sputtering rate would be preferentially eroded as sputtering progressed, making _MSi2 more likely to fall off. Therefore, it is preferable that _MSi2 be bonded in a chain.

Furthermore, if the grain size of the _MSi2 phase exceeds 30 μm, protrusions form on the _MSi2 phase during sputtering, generating particles, whereas if the grain size is less than 0.5 μm, the _MSi2 phase easily falls off from the Si phase during sputtering, again causing particle generation. Therefore, the grain size of the _MSi2 phase is preferably 0.5 to 30 μm, and more preferably in the range of 2 to 20 μm.

In addition, the composition MSi _X has an X value of 2.0<X<4.0, and MS
If the grain size of _MSi2 satisfies the range of 0.5 to 30 μm, it is preferable that 400 to 400× ¹⁰⁴ _MSi2 particles are present within ^{1 mm2} of the cross section of the mixed structure. Furthermore, if the grain size is 2 to 20 μm, it is preferable that _2,000 to 300,
It is preferred that there are 000 of them.

The size of _MSi2 depends on the particle size of the metal particles that form the metal silicide, but most M particles exist in an agglomerated state, resulting in the formation of _MSi2 with different particle sizes. If the particle size variation becomes large, the erosion surface becomes uneven during sputtering, and the resulting unevenness increases the amount of particles generated. Therefore, it is necessary to make the particle size as uniform as possible, and the average particle size of the _MSi2 phase is preferably 2 to 15 μm. A more preferred range is 5 to 10 μm.

The average particle size here refers to the average particle size per 100 metal silicide particles.

Furthermore, the shape of each _MSi2 particle bonded in a chain is ideally approximately spherical. This is because spherical particles are less likely to fall out of the mixed structure with the Si phase, and particles with angular portions are more likely to generate particles due to abnormal discharge. From this perspective, M particles obtained by purification using an ion exchange method tend to aggregate during the reduction process, and _MSi2 particles formed by the coalescence of M particles have many irregularities. Therefore, it is necessary to treat them under reduction conditions that make aggregation less likely to occur, or to add a dispersant when mixing the powders to suppress aggregation. Alternatively, it is also preferable to use M particles produced by a chemical vapor deposition method, which provides good particle dispersibility.

Here, Chemical Vapor Deposition (Chemical Vapor Deposition)
CVD (hereinafter abbreviated as CVD) is a method in which raw materials such as halides, sulfides, and hydrides are converted into a gas phase at high temperatures, and then chemical reactions such as thermal decomposition, oxidation, and reduction are carried out, and the reaction products are then deposited on a substrate. CVD is widely used as a method for forming semiconductors and insulating films.

On the other hand, Si reacts with M particles to form _MSi2 ,
Excess Si is forced to flow around the _MSi2 particles, resulting in a form in which Si is present discontinuously in the gaps between the _{MSi2 particles} bonded in a chain.

If this Si is present continuously, as sputtering progresses, Si is eroded preferentially over _MSi2 , leading to particle shedding. In addition, the Si portion has low mechanical strength and is vulnerable to thermal shock due to the action of thermal stress generated in the target during sputtering, making it prone to breakage. Therefore, in order to suppress particles by improving strength, it is preferable that Si be present in the gaps between _MSi2 and that it be present discontinuously.

Furthermore, if the grain size of Si exceeds 30 μm, the action of thermal stress causes chipping of the Si erosion portion, and protrusions are formed on the Si phase during sputtering, which tends to generate particles. Therefore, the maximum grain size of Si is preferably 30 μm or less, and more preferably 20 μm or less.

Furthermore, if the Si grain size varies greatly, stress will be concentrated in the large grain size portion, making it prone to breakage due to repeated thermal stress. Therefore, the average Si grain size is preferably 2 to 10 μm, and more preferably 3 to 8 μm.

The grain size of Si here is the average value of the maximum and minimum lengths of the Si phase present in the gaps between _MSi2 , and is
The average particle size indicates the average particle size per 100 Si particles.

It is also desirable to use high-purity Si raw material powder or high-purity Si powder containing dopants. The impurities contained in this high-purity Si should be as low as possible, as they can cause deterioration of device characteristics. Incidentally, radioactive elements such as U and Th, which cause soft errors, should be 5 ppb or less.
Alkali metal elements such as Na and K, which cause mobile ion contamination, are 100 ppb or less, heavy metal elements such as Fe, Ni, and Cr, which become deep level impurities, are 1 ppm or less, carbon, which causes particle generation and etching defects, is 300 ppm or less, and oxygen, which causes increased resistance, is 500 ppm or less.
It is preferably pm or less.

The impurities contained in this Si powder, such as carbon, oxygen, Na, and K, adhere to the powder surface during the Si milling process. These impurities can be reduced by heat-treating the impurity-contaminated Si powder at 1200 to 1300°C for 2 to 6 hours in a high vacuum of ^10-4 Torr or less. Therefore, it is preferable to use heat-treated Si raw material powder for target production.

Generally, when a target is formed using Si raw material powder containing a dopant, the dopant diffuses and concentrates at specific sites such as crystal interfaces during the reaction synthesis. These dopant atoms cause lattice disorder or distort the lattice of _MSi2.
The Si phase migrates to the boundary between the Si phase and the Si phase to form an interfacial layer.

When this interface layer exists, the bonding strength between the _MSi2 phase and the Si phase is improved, and the _MSi2 phase is less likely to fall off from the mixed structure with the Si _phase .
If an interface layer with a high dopant concentration exists at the boundary between the phases, abrupt changes in electrical resistance will be eliminated, reducing the occurrence of abnormal discharges during sputtering. This is expected to have the effect of suppressing particles induced by abnormal discharges.

Furthermore, the present inventors have conducted extensive research to mitigate the sudden change in electrical resistance at the boundary between the _MSi2 phase and the Si phase, and as a result have found that a target obtained by sintering a Si powder containing at least one element selected from the group consisting of B, P, Sb, and As as a dopant and an unavoidable element and having controlled electrical resistance, and an M powder or an _MSi2 powder, has improved matching of the electrical resistance between the _MSi2 phase and the Si phase, resulting in a uniform sputtering rate, and also has excellent interfacial strength due to the formation of an interface layer at the boundary between the _MSi2 phase and the Si phase in which the above elements are diffused.

Among the above dopants, B, P, Sb, and As are
It is an element that has the effect of significantly reducing the electrical resistance of the i-phase.
When a Si phase containing these elements is used, the electrical resistance of both phases is matched, resulting in a uniform sputtering rate.
The film composition is stable and the film thickness is uniform. In addition, these elements in the Si phase cause lattice disorder and large lattice distortion during sintering.
The elements diffuse and move to the boundary between the _i2 phase and the Si phase, forming the aforementioned interface layer. In this case, unavoidable elements other than B, P, Sb, and As are also included in the interface layer, which brings about the same effect. For example, F
e, Ni, etc.

The thickness of this interface layer varies depending on the amount of dopant contained in the Si phase, but is preferably in the range of 100 to 10,000 Å.

When the thickness of the interface layer is 10,000 Å or more, S
A significant amount of dopant in the i-phase will change the film properties, and if the thickness is less than 100 Å, the above effects cannot be fully expected. Therefore, a more preferred range is 1,000 to 8,000 Å.

The thickness of this interfacial layer is generally detected by high-resolution secondary ion mass spectrometry (SIMS).

SIMS is a method for analyzing impurities in the surface layer with high sensitivity and three-dimensional analysis by sputter etching a sample with O2 ⁺ or Cs ⁺ primary ions and capturing the generated secondary ions. The thickness of the interface layer is determined by measuring the depth profile of the dopant contained in the Si phase up to the _MSi2 phase.

Here, the thickness of the interface layer is the distance from one inflection point located at the base of the dopant profile in the Si phase to another inflection point.

Furthermore, the resistivity of the Si phase is 0.01 to 100 Ω·
It is desirable to set the resistivity to 0.01 Ω cm range.
・When it is less than cm, the sputtering rate of Si increases and
is deeply eroded, causing the generation of particles and making it impossible to obtain the desired film composition.
If the resistivity exceeds 100 Ω·cm, the above effect cannot be fully expected. Therefore, it is more preferable that the resistivity of the Si phase is in the range of 0.1 to 10 Ω·cm.

On the other hand, the carbon-contaminated areas do not disperse well and remain as protrusions on the erosion surface, which results in unstable plasma discharge in those areas, causing repeated abnormal discharges and inducing the generation of particles. Also, if a large amount of carbon is mixed into the film, the following problems may occur during the formation of wiring by etching:
Since these portions remain as etching residues and cause wiring defects or disconnections due to the formation of insulators, the carbon impurity content must be suppressed to 100 ppm or less, preferably 50 ppm or less, and more preferably 30 ppm or less. This carbon content is detected by a carbon analyzer that utilizes the combustion-infrared absorption method.

Furthermore, if the target contains a large amount of oxygen impurities, oxygen will be mixed into the film during sputtering, increasing the film resistance, so the oxygen impurity content is preferably kept to 150 ppm or less, more preferably 100 ppm or less.
The oxygen content is detected by an oxygen analyzer that utilizes an inert gas fusion-infrared absorption method.

The sputtering target of the present invention has a mixed structure of fine grained _MSi2 phase and Si phase. This is because the _MSi2 phase is formed by sintering synthesis from a mixed powder prepared by preparing M powder and Si powder so that the X value of the composition _MSiX is 2.0<X<4.0. Therefore, the excess Si
This was because the remaining fraction remained around the MSi ₂ phase.

That is, when a mixed powder of M and Si is heated under an appropriate pressure, Si softens and reacts with M to form _MSi2 . Therefore, at the contact points between Si particles and M particles, MSi
The exothermic reaction that produces _MSi2 causes a local temperature rise and further softens the particles, which then aggregate on the surface and periphery of the particles that are converting to _MSi2 , and the conversion to _MSi2 progresses. On the other hand, the large amount of unreacted Si and excess Si that have softened somewhat are forced to flow around the particles that are converting to _MSi2 , causing densification, and the conversion to _MSi2 progresses.
The Si phase and the MSi 2 phase or the MSi ₂ phases are strongly bonded to each other by a diffusion reaction.

Here, the value of X in the composition MSi _X is 2.0<X<4.0
The reason for limiting the composition to the following is as follows.
If the X value in the composition of _SiX is less than 2.0, a large tensile stress is generated in the formed silicide film, which deteriorates the adhesion to the substrate and makes the film more likely to peel off. On the other hand, if the X value in the composition of _MSiX is more than 4.0, the sheet resistance of the film becomes high, making it unsuitable for use as an electrode wiring film.

Furthermore, the density ratio of the target is also related to the amount of particles generated; when the density is low, many pores exist in the target, and abnormal discharge is likely to occur in these areas, causing discharge areas to be missing and generating particles, so it is desirable that the density ratio of the target be 99% or more at all locations. Here, the density ratio (d = _dt / _ds ) is the ratio of the density ( _dt ) of the sintered body actually measured by the Archimedes method to the theoretical density ( _ds ) calculated from the composition ratio of the sintered body.

The inventors have also found that particle generation from the target during sputtering is due to protrusions formed in the _MSi2 phase and the Si phase, as well as to processing defect layers, surface conditions, or residual stresses that arise when the silicide sintered body is subjected to mechanical finishing such as grinding. Conventional target finishing by grinding is a processing method in which the workpiece is scraped away by hard abrasive grains from a grinding wheel rotating at high speed. When a hard yet brittle material such as a silicide sintered body made of metal silicide and silicon is ground using this method, granular chips inevitably fly off from the processed surface. According to the inventors' findings, this is thought to be caused by microcracks that form on the ground surface due to the contact stress of the abrasive grains during grinding, and then, after the abrasive grains pass through, the sudden release of stress pushes up the shoulders of the cracks, causing them to break off as fragments. Usually,
When machining hard and brittle materials, the cutting depth or load per abrasive grain is appropriately increased so that cracks are included in the local stress field induced by the abrasive grain, and machining proceeds by accumulating microfractures of the material. As a result, many machining defects such as grinding marks, voids, and microcracks are generated on the ground surface of the silicide sintered body.

When sputtering is performed using a target having such a defective layer over its entire surface, the collision of ions in the plasma causes fine particles to peel off from the target surface, starting from the defects, and these particles become the aforementioned particles.

Therefore, it is desirable to set the roughness of the surface of the target to 0.05 μm or less in terms of Ra (center line roughness) and to finish the target so that there are essentially no processing defect layers such as microcracks or defective portions that occur during mechanical processing.

Here, the surface roughness Ra (center line roughness) is defined in accordance with the Japanese Industrial Standard (JIS-B0601).
As defined in [1], a portion of measurement length l is extracted from the roughness curve in the direction of its center line, the center line of this extracted portion is the X axis, the direction of the longitudinal magnification is the Y axis, and the roughness curve is expressed as y = f(X). The value obtained by the following formula is expressed in micrometers (μm).

In order to reduce the roughness of the finished surface and substantially eliminate the layer of processing defects such as cracks and missing holes, it is essential to make the processing unit smaller than the distribution of material defects. Specifically, it is necessary to reduce the load per abrasive grain by using abrasive grains with small and uniform grain size, or by using a polisher with soft elasticity or viscoelasticity, so that the stress induced in the material is below the fracture stress value.

Therefore, even in the case of a hard and brittle material such as a sintered body containing a metal silicide phase, when the load is extremely small, the material will only undergo plastic flow deformation, and there will be areas where no cracks will occur, allowing the machined surface to be finished into a glossy surface with extremely little unevenness.

Specific preferred methods include lapping and polishing used for the purpose of surface finishing, and mechanochemical polishing used for the purpose of ultra-precision finishing.

Mechano-chemical polishing is a high-precision polishing method that combines the conventional mechanical polishing method using a grinding wheel with the chemical polishing method that utilizes the action of chemicals to micro-erode the surface of the material being polished.

However, it is difficult to actually finish a sintered silicide body to the desired dimensions directly by the above-mentioned processing, so it is necessary to first process the surface by an efficient surface treatment such as grinding, and then to perform the above-mentioned lapping and polishing processes in combination to remove the generated processing defect layer.

In the above-mentioned surface processing methods, the abrasive grains used become smaller in the order of lapping, polishing, and mechanochemical polishing, and the finished surface roughness also becomes finer. By applying such processing methods to metal silicide targets, the amount of particles generated is significantly reduced. That is, according to the findings of the inventors, there is a correlation between the amount of particles generated and surface roughness. To suppress the generation of particles with a particle size that can lead to electrode wiring defects, the surface roughness Ra (center line roughness) of the processed surface is preferably 0.02 μm or less, and more preferably 0.05 μm or less.

In sputtering using Ar ion irradiation,
The impact points of ions create high stress fields and are exposed to high temperatures. Therefore, if residual stress remains unevenly in the target surface, the heat generated during sputtering redistributes the stress, causing localized stress increases and large cracks, including radial cracks, resulting in a rapid increase in particle generation. From this perspective, the residual stress is preferably 15 kg/ ^mm² or less, and more preferably 5 kg/ ^mm² or less.

Next, the production method of the present invention will be specifically described.

The manufacturing method consists of the following steps: Step I: mixing M powder and Si powder in a predetermined ratio; Step II: heating the mixed powder at low temperature to reduce carbon and oxygen; Step III: filling the M/Si mixed powder into a molding die and synthesizing a high-melting-point metal silicide by silicidation in a hot press under high vacuum and low pressure; and Step IV: densifying and sintering under high pressure. The heating temperature and pressure in Steps III and IV are particularly important factors in obtaining a sintered body with a fine structure and high density.

First, step I of the manufacturing method is a step of blending and mixing M powder and Si powder so that the composition has an Si/M atomic ratio of 2.0 to 4.0.

In this process of mixing M powder and Si powder, the particle size of both powders affects the particle size of _MSi2 produced by silicide synthesis and the particle size of intervening Si. In order to obtain the above-mentioned fine structure, M powder with a maximum particle size of 10 μm or less and Si powder with a maximum particle size of 3 μm or less are mixed.
It is preferable to use Si powder with a particle size of 0 μm or less.

The reason why the X value of the composition _MSiX is limited to 2.0<x<4.0 is that if the X value is less than 2.0, a large tensile stress is generated in the formed silicide film, which deteriorates the adhesion to the substrate and makes the film more susceptible to peeling, while if the X value exceeds 4.0, the sheet resistance of the film becomes high, making it unsuitable for use as an electrode wiring film.

The raw material M powder and Si powder are mixed in an Si/M atomic ratio of 2.0 to
4.0 and dry mix thoroughly and uniformly using a ball mill or V-type mixer.
This is undesirable because the target structure and composition become non-uniform, resulting in deterioration of film properties.

Here, the powder mixing is preferably carried out in a vacuum or in an inert gas atmosphere to prevent oxygen contamination.

The amount of Si to be blended should be slightly in excess of the target composition, taking into account the loss of Si and the oxide film _SiO2 due to evaporation from the surface of the Si powder when heated at high temperatures. The excess amount is small, just under 5%, and is determined empirically, taking into account the temperature, time, pressure, etc. of subsequent processes.

In step II, the mixed powder prepared in step I is heated at a low temperature in a high vacuum to reduce carbon and oxygen. In this step, it is important to set the heating temperature, holding time, and degree of vacuum appropriately without applying pressure. That is, the heating temperature is 1000 to 1300°C.
If the heating temperature is less than 1000°C, impurities cannot be removed sufficiently.
If the heating temperature exceeds 1100 °C, the silicide reaction will start before the impurities have been sufficiently evaporated, resulting in a target with a high carbon and oxygen content.
It is more preferable to set the temperature to 1,300°C or less.
The holding time is preferably set to 1 to 10 hours in consideration of the heating temperature, and if it is less than 1 hour, the above effect cannot be expected to be fully obtained, while if it exceeds 10 hours, productivity will be reduced. Furthermore, the degree of vacuum in the furnace is preferably a high vacuum of ^10-4 Torr or less, more preferably ^10-5 Torr, in order to sufficiently reduce carbon and oxygen.
The following is the result.

However, if the hot press apparatus is suddenly evacuated, the mixed powder will scatter from the molding die, resulting in a sintered body that is insufficiently densified even after going through the steps described below. Therefore, it is preferable to gradually reduce the degree of vacuum inside the hot press apparatus until the pressure therein reaches 100 Torr or less.

In step III, the mixed powder degassed in step II is heated under high vacuum and low pressure to synthesize the _MSi2 phase. In this silicide synthesis step, the heating temperature and pressure must be set to appropriate conditions to gradually promote the silicide reaction, suppress the growth of _MSi2 particles, and allow the softened Si to flow into the gaps between the _MSi2 particles. Therefore, the heating temperature is set to 1000 to 1300°C.
If the heating temperature is less than 1000°C, the silicide reaction does not start easily, and if it exceeds 1300°C, the _MSi2 particles grow and become coarse due to the rapid silicide reaction.
It is more preferable to set the temperature at 1300°C.

At this time, the heating temperature is preferably less than 20° C./min to refine the synthesized MSi ₂ phase. The silicide synthesis is preferably carried out in a high vacuum of 10 ⁻⁴ Torr or less to control the silicide reaction rate and prevent the inclusion of impurity gases.

Furthermore, since the magnitude of the pressing pressure affects the particle size of the _MSi2 particles, it is preferable to set it between 10 and 100 kg/ _cm2. If the pressure is less than 10 kg/ _cm2 , the heat of the silicide reaction is low, the softening and flow of Si is not carried out well, and an inhomogeneous structure with segregated Si is obtained. On the other hand, if the pressure is 100 kg/ _cm2 or more, the contact pressure between the M powder and the Si powder increases, the heat generated by the silicide reaction increases, and the reaction progresses rapidly, resulting in coarsening of the _MSi2 particles. Therefore, it is more preferable to set the magnitude of the pressing pressure in the range of 30 to 60 kg/ _cm2 .

The atmosphere during this silicide synthesis is set to 1000 K to control the silicide reaction rate and prevent the inclusion of impurity gases.
It is desirable to carry out the treatment in a high vacuum of ^0-4 Torr or less.

Step IV is a step in which the sintered body is densified by heating it to a temperature just below the eutectic temperature under high pressure in a high vacuum or in an inert gas atmosphere.

In this densification sintering process, the pressing pressure, heating temperature and holding time are important to obtain a high density sintered body.

The pressing pressure is set to 100 to 1500 kJ/cm2 to promote densification of the sintered body.
Preferably, the pressure is 300 kg/ ^cm² , and the pressure is 10
If the pressing pressure is less than 300 kg/ ^cm² , the sintered body will have a low density with many remaining pores, while if the pressing pressure exceeds 300 kg/ ^cm² , the sintered body will have a high density, but the graphite molding die will be easily damaged.
It is more preferable to set it in the range of 250 kg/cm 2 to 300 kg/cm ² .

The sintering temperature (heating temperature) T is a temperature just below the eutectic temperature Ts.
That is, it is preferable to set the range of Ts-50≦T<Ts. Here, for example, M can be W, Mo, Ti, T
When using a, the eutectic temperature Ts is 1400,
1410, 1330, 1385°C. T is Ts-5
If T is less than 0, pores will remain and a sintered body with the desired high density will not be obtained. On the other hand, if T is greater than or equal to Ts, the Si phase will melt and flow out of the mold, resulting in a sintered body with a large deviation in composition ratio.

The holding time for heating and sintering is preferably 1 to 8 hours.
If the sintering time is less than 1 hour, many pores remain and a high-density sintered body cannot be obtained, while if the sintering time is more than 8 hours, the densification does not progress any further, resulting in a decrease in the production efficiency of the target. This sintering for densification is preferably carried out in a vacuum or inert gas atmosphere to prevent contamination by the incorporation of impurities. However, in a nitrogen atmosphere, Si ₃ N ₄
This is undesirable because

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1A is a scanning electron micrograph showing the metal structure of a target according to an embodiment.

FIG. 1B is a partial schematic diagram for explaining the metal structure photograph of FIG. 1A.

FIG. 2A is a scanning electron microscope photograph showing the metal structure of the targets according to the comparative example and the conventional example.

FIG. 2B is a partial schematic diagram for explaining the metal structure photograph of FIG. 2A.

FIG. 3A is a scanning electron micrograph showing the morphology of the erosion surface of the target according to the example.

FIG. 3B is a partial schematic diagram for explaining the surface morphology photograph of FIG. 3A.

FIG. 4A is a scanning electron microscope photograph showing the morphology of the erosion surface of the targets according to the comparative example and the conventional example.

FIG. 4B is a partial schematic diagram for explaining the surface morphology photograph of FIG. 4A.

FIG. 5A is a scanning electron microscope photograph showing enlarged projections present on the erosion surfaces of the targets according to the comparative example and the conventional example.

FIG. 5B is a partial schematic view for explaining the protrusions in FIG. 5A.

FIG. 6 is a scanning electron microscope photograph showing the results of elemental analysis of the surface of the protrusion shown in FIG. 5A.

FIG. 7A is a photograph of the metal structure of the target of the example taken with an optical microscope.

FIG. 7B is a partial schematic diagram for explaining the metal structure photograph of FIG. 7A.

FIG. 8A is a photograph of the metal structure of the target of the comparative example taken with an optical microscope.

FIG. 8B is a partial schematic diagram for explaining the metal structure photograph of FIG. 8A.

FIG. 9A is a photograph of the metal structure of a conventional target taken with an optical microscope.

FIG. 9B is a partial schematic diagram for explaining the metal structure photograph of FIG. 9A.

FIG. 10A is a scanning electron micrograph showing the morphology of the erosion surface of the target according to the example.

FIG. 10B is a partial schematic diagram for explaining the photograph of the erosion surface of FIG. 10A.

FIG. 11A is a scanning electron microscope photograph showing the morphology of the erosion surface of the target according to the comparative example.

FIG. 11B is a partial schematic diagram for explaining the photograph of the erosion surface of FIG. 11A.

FIG. 12A is a scanning electron micrograph showing the morphology of the erosion surface of a conventional target.

FIG. 12B is a partial schematic diagram for explaining the photograph of the erosion surface of FIG. 12A.

MODE FOR CARRYING OUT THE INVENTION The configuration and effects of the present invention will now be described in more detail with reference to the following examples.

[Examples 1 to 12] As shown in Table 1, high-purity W with a maximum particle size of 10 μm or less
Mo, Ta, and Nb powders were mixed with high-purity Si powder with a maximum particle size of 30 μm or less at an Si/M atomic ratio of 2.7 and mixed for 48 hours in a ball mill purged with high-purity Ar gas. The mixed powder was filled into a molding die, which was then inserted into a hot press machine and degassed at 1200°C for 3 hours in a vacuum of 8 × ^10-5 Torr to reduce impurities such as carbon and oxygen.

Next, silicide synthesis and densification sintering were carried out under the conditions shown in Table 1, and the resulting sintered body was ground and polished, and then electro-discharge machined to form a target having a diameter of 260 mm and a thickness of 6 mm.

[Comparative Examples 1 to 12] In Comparative Examples 1 to 12, a mixed powder was prepared by blending high-purity W, Ta, and Nb powders having a maximum particle size of 100 μm or less with high-purity Si powder having a maximum particle size of 200 μm or less so that the Si/M atomic ratio was 2.7. This was subjected to silicide synthesis and densification sintering under the conditions shown in Table 1 without degassing heat treatment in a vacuum, and the resulting sintered body was ground and polished and then electric discharge machined to form a target having a diameter of 260 mm and a thickness of 6 mm.

[Conventional Examples 1 to 3] High-purity W powder with a maximum particle size of 100 μm or less and a maximum particle size of 20
High purity Si powder of 0 μm or less and Si/M atomic ratio of 2.0
A mixed powder was prepared so that the
A pre-sintered body was formed by heating at 1300°C for 4 hours in a vacuum of ^0-4 Torr, and then impregnated with molten Si to produce a sintered body with a Si/W atomic ratio of 2.7. This sintered body was then ground and polished.
The target was finished by electrical discharge machining to a diameter of 260 mm and a thickness of 6 mm, and a target of Conventional Example 1 was obtained.

High purity W powder with a maximum particle size of 15 μm or less and a maximum particle size of 20 μm
A mixed powder was prepared by blending high purity Si powder of 8×10
The mixture was heated at 1250°C for 4 hours in a vacuum of ^-5 Torr to form a pre-sintered body, which was then filled into a pressure-tight sealing can.
This was hot isostatically pressed at 1180°C for 3 hours under a pressure of 1000 atoms to produce a sintered body, which was then ground and polished, and then electro-discharge machined to produce a target having a diameter of 260 mm and a thickness of 6 mm, thereby obtaining the target of Conventional Example 2.

High purity W powder with a maximum particle size of 100 μm or less and a maximum particle size of 20
High purity Si powder of 0 μm or less and Si/M atomic ratio of 2.5
A mixed powder was prepared so that the
After heating at 1300°C for 4 hours in a vacuum of ^0-4 Torr to form a pre-sintered body, the pre-sintered body was crushed and then mixed with Si/W.
Silicide synthesis powder was added so that the atomic ratio was 2.7.
This was hot pressed in an Ar gas atmosphere at 1380°C for 3 hours to produce a sintered body, which was then ground and polished, and then electro-discharge machined to produce a target having a diameter of 260 mm and a thickness of 6 mm, thereby obtaining the target of Conventional Example 3.

The results of microscopic observation of the cross-sectional structures of the example and comparative example targets are shown in Figures 1A, 1B, 2A, and 2B, respectively. As a result, in the structure of the target according to the comparative example, as shown in Figures 2A and 2B, Si2 segregates and _MSi21 becomes coarse, whereas in the example, as shown in Figures 1A and 1B, the maximum grain size is 10
MSi ₂ I of less than μm are bonded in a chain form, and S is present in the gaps between them.
It exhibited a fine and uniform structure with discontinuous i2.

In addition, as a result of analyzing the carbon and oxygen contents, the carbon content was 50 ppm or less and the oxygen content was 100 ppm or less in the example target, whereas the carbon content was about 250 ppm and the oxygen content was 1500 ppm in the comparative example target.
It contained a very large amount.

Each of the targets prepared in Examples 1 to 12, Comparative Examples 1 to 12, and Conventional Examples 1 to 3 was set in a magnetron sputtering apparatus, and then, an argon pressure of 2.3×10 ⁻³ To
Sputtering was carried out under the conditions of rr to deposit a silicide film to a thickness of about 3000 Å on a 5-inch Si wafer, and the amount of particles mixed in was measured. The results are shown in Table 1.

As is clear from the results shown in Table 1, the amount of particles generated from the target according to this example was extremely small compared to those of the comparative example and the conventional example. Furthermore, when the erosion surfaces of the targets of the example, comparative example and conventional example were observed with a scanning electron microscope (SEM),
As shown in Figures 4A and 4B, numerous protrusions 3 were observed on the erosion surfaces of the targets of the comparative example and conventional example, respectively, but no protrusions were observed on the erosion surfaces of the targets of the example, as shown in Figures 3A and 3B.

Furthermore, the results of enlarged observation of relatively large protrusions 3 observed on the erosion surfaces of the targets according to the conventional example and the comparative example are shown in Figs. 5A and 5B.
The surface of the protuberance 3 shown in the figure was analyzed using an X-ray microanalyzer (X
The results of elemental analysis by MA are shown in FIG.
As shown in FIG. 6, scattered white dots of carbon are observed on the surface of the protrusions, and this carbon is the cause of particle generation.

These results demonstrate that if the targets according to the examples are used to form electrode wiring for semiconductor devices, a significant improvement in the manufacturing yield of semiconductor products can be expected.

Next, the characteristics of the target are compared between the case where an interface layer is formed between the MSi ₂ phase and the Si phase (Example) and the case where no interface layer is formed (Comparative Example).

[Examples 101 to 114] High-purity W, Mo, Ti, Ta, Zr, with an average particle size of 2 μm
Hf, Nb, V, Co, Cr, Ni powder and their combinations with high purity Si powder (B,
P, Sb, As, and other unavoidable elements such as Fe and Ni) were mixed at a Si/M atomic ratio of 2.6, and high-purity A
The mixture was dry mixed for 72 hours in a ball mill purged with r gas.
This mixed powder was filled into a hot press mold made of high-purity graphite, and then placed in a vacuum hot press device.
The mixture was degassed for 2 hours at 1250° C. in a vacuum of ⁻⁵ Torr.

Next, a press pressure of 50 kg/cm ² was applied in a high vacuum of 5×10 ⁻⁵ Torr, and metal silicide (MSi ₂ ) was synthesized at 1250° C. After that, the atmosphere in the furnace was heated to 600 Torr by adding high-purity Ar gas.
The temperature was raised to rr and sintered at 1370°C for 2 hours. The resulting sintered body was ground, polished and then electro-discharge machined to a diameter of 260 mm and a thickness of 6 mm.
It was finished as a target.

[Comparative Examples 101 to 114] Comparative Examples 101 to 110 were made of high-purity W, Mo, Ti, Ta, Zr, Hf, Nb, V, Co, and the like, each having an average particle size of 25 μm.
Cr and Ni powders were mixed with high-purity Si powder having an average particle size of 40 μm so that the Si/M atomic ratio was 2.6, and then hot-pressed under the following conditions: hot-press temperature: 1380°C, hot-press pressure: 250 kg/ ^cm2 , holding time: 2 hours, furnace atmosphere: up to 1250°C in a vacuum of 8 × ^10-5 Torr, and from 1250 to 1380°C in argon gas at 600 Torr, to obtain a target having a diameter of 260 mm and a thickness of 6 mm manufactured by a conventional method.

Furthermore, as Comparative Examples 111 to 114, the average particle size was 80 μm
WSi ₂ , MoSi ₂ , TaSi ₂ and TiSi
_The Si/M2 powder and high-purity Si powder with an average particle size of 60 μm were mixed.
After mixing to an atomic ratio of 2.6, Comparative Examples 101 to
Hot pressed under the same conditions as 110, diameter 260 mm
A target having a diameter of 100 mm and a thickness of 6 mm was obtained by a conventional manufacturing method.

The average thickness, density ratio, and flexural strength of the interface layer were measured for the targets of Examples 101 to 114 and Comparative Examples 101 to 114, and the results are summarized in Table 2. As is clear from Table 2, the targets of Examples 101 to 114 exhibit high density and high flexural strength, which indicates that the _MSi2 phase and the Si phase are firmly bonded by the interface layer.

The cross-sectional structures of the targets of the example, comparative example, and conventional example were observed by an optical microscope, and are shown in Figures 7A to 7B, 8A to 8B, and 9A to 9B, respectively. As a result, as shown in Figures 7A to 7B, in this example, MSi2 phase and Si phase 2 with an average grain size of ₁₀ μm were observed.
It showed a fine mixed structure with

8A and 8B, in the case of the target according to the comparative example, both the Si phase 2 and the MSi ₂ phase 1 are coarse. Also, as shown in FIGS. 9A and 9B, in the target according to the conventional example, the Si phase 2 and the MSi ₂ phase 1 are coarse, and it is confirmed that the target has a structure that is prone to particle generation.

In addition, Examples 110 to 114 and Comparative Examples 101 to 114
Each target prepared in the above step 1 was set in a magnetron sputtering apparatus, and then the target was heated under an argon pressure of 2.3×10 ⁻³
Sputtering was carried out under the conditions above to deposit a silicide film to a thickness of about 3000 Å on a 5-inch Si wafer, and the amount of particles mixed in was measured. The results are shown in Table 2.

As is clear from the results shown in Table 2, the amount of particles generated from the target of this example was very small.

Furthermore, when the sputtering surfaces of the targets of the example, comparative example, and conventional example were observed by a scanning electron microscope (SEM), the results are shown in FIGS. 10A to 10B and 11A to 11C, respectively.
The metal structures shown in Figures 11B and 12A to 12B were observed.
A large number of protrusions 3 are observed on the sputtered surface of the conventional example (Fig. 10A) and the conventional example (Fig. 12A, Fig. 12B).
10B, no protrusions 3 were observed on the sputtering surface of the target of this example. This result demonstrates that if the target of the present invention is used to form electrode wiring for semiconductor devices, a significant improvement in yield can be expected.

Next, the influence of the processing defect layer, surface condition, and residual stress that occur when the silicide sintered body constituting the target is subjected to mechanical finishing such as grinding on the generation of particles will be confirmed by the following examples.

[Example 200] A sintered silicide (tungsten silicide) was cut into a size of 260 mm in diameter by wire electric discharge machining, and then ground using a vertical rotary surface grinder with a grinding wheel SD270J55B
W6, grinding wheel peripheral speed 1200 m/min, table rotation speed 1
6mm thick under the conditions of 2 rpm and 10 μm/min cutting depth
The target was then ground to a fine powder.

Next, after soldering a backing plate to the backside of the processed surface, the grinding surface is polished with diamond abrasive grains 1000 times using a lens polisher.
The surface was then subjected to lapping with 5 μm abrasive grains for 60 hours and with 3 μm abrasive grains for 10 hours, after which the machining fluid adhering to the lapped surface was removed with an ultrasonic cleaner, followed by degreasing with acetone and drying for finishing.

When the obtained processed surface was observed with a scanning electron microscope (SEM), it was found that no grinding marks or missing holes caused by the grinding process remained, and furthermore, no numerous microcracks caused by the deformation and destruction action of the grinding grains were observed, confirming that the processing defect layer had been removed.

Furthermore, the roughness of the machined surface was measured using a surface roughness measuring device (Talysurf), and the residual stress was measured using an X-ray stress measuring device by the parallel tilt method. The results are shown in Table 3. The measurement results for the as-ground sample are also shown in Table 3 as Comparative Example 200.

After this target was set in a magnetron sputtering device, sputtering was performed by Ar ion irradiation to deposit a silicide film on a 5-inch Si wafer.
The amount of particles mixed into this film was measured, and the results are shown in Table 3. The results of sputtering of the ground surface are also shown in Table 3 as Comparative Example 200. As is clear from Table 3, the amount of particles in the film formed using the target of Example 200 was significantly reduced, and it was found that the amount of particles generated during sputtering can be reduced by lapping.

[Example 201] A silicide sintered body with a diameter of 260 mm was ground and lapped in the same manner as in Example 200, and then polished for 10 hours using 0.3 μm cerium oxide abrasive grains and an acrylic resin polisher under conditions of a polisher pressure of 1 kg/ ^cm2 and a polisher speed of 10 m/min. The processing fluid was removed by ultrasonic cleaning, and the target was then degreased with acetone and dried to finish the target.

The obtained machined surface was observed under an SEM, and it was found that the machining defects such as grinding marks, voids, and microcracks caused by the grinding process had completely disappeared, and the surface was finished to a mirror finish. The measurement results of the surface roughness and residual stress of the machined surface are shown in Table 3. Compared to the ground surface shown in Comparative Example 200, the surface irregularities were extremely small, and the plastic strain or elastic strain in the surface layer caused by grinding had been almost completely removed.

This target was used to form a silicide film on a 5-inch Si wafer by magnetron sputtering. The amount of particles mixed into the film was measured and the results are shown in Table 3. As is clear from these results, polishing as a final finishing step significantly reduces the number of particles generated from the target due to improved surface quality.

[Example 202] A silicide sintered body having a diameter of 260 mm was ground and lapped in the same manner as in Example 200, and then polished for 20 minutes using 0.02 μm SiO ₂ powder and a cross polisher under the conditions of a polisher pressure of 1 kg/cm ² and a polisher speed of 10 m/min.
The target was finished by mechanochemical polishing for 1 hour, ultrasonic cleaning, degreasing with acetone, and drying.

SEM observation of the processed surface revealed no defects caused by the grinding process. Furthermore, the processed surface was extremely smooth compared to its surface roughness and residual stress, and the processed surface was in a state that was no different from a non-strained surface.

Magnetron sputtering was performed using this target to form a silicide film on a 5-inch Si wafer, and the amount of particles mixed into the film was measured. As a result, as shown in Table 3, almost no particles were found, and it was confirmed that the processing defect layer and residual stress that cause particles to be generated could be completely removed as a final finish.

INDUSTRIAL APPLICABILITY The sputtering target and its manufacturing method according to the present invention can provide a target having a high density and high strength fine structure that can substantially prevent particle generation, and is therefore extremely useful in forming high quality thin films, particularly for use as electrodes and wiring materials for semiconductor devices.

──────────────────────────────────────────────────── Continued from the front page (72) Inventor: Hiromi Shizu 1-25-7-208 Kameino, Fujisawa City, Kanagawa Prefecture (72) Inventor: Noriaki Yagi 2121 Totsuka-cho, Totsuka-ku, Yokohama City, Kanagawa Prefecture Tsukadai Corp. D103 (56) References: JP 61-179534 (JP, A) JP 61-76664 (JP, A) JP 61-145829 (JP, A)

Claims (13)

[Claims] [Claim 1] A metal silicide phase is formed by chain bonding of metal silicides (having a chemical composition of _MSi2 , where M is a metal), and the silicon phase formed by bonding of silicon particles has a fine mixed structure that exists discontinuously in the gaps between the metal silicides,
A sputtering target having a carbon content of 100 ppm or less. 2. The sputtering target according to claim 1, wherein 400 to 400 x 10 ⁴ metal silicides having a grain size of 0.5 to 30 μm are present within 1 mm ² of a cross section of the mixed structure, and the maximum grain size of Si is 30 μm or less. 3. The sputtering target according to claim 1, wherein the metal silicide has an average particle size of 2 to 15 μm, while the silicon has an average particle size of 2 to 10 μm. 4. The sputtering target according to claim 1, wherein the density ratio is 99% or more. 5. The sputtering target according to claim 1, wherein the oxygen content is 150 ppm or less. 6. The sputtering target according to claim 1, wherein the metal of the metal silicide is at least one metal selected from the group consisting of tungsten, molybdenum, titanium, zirconium, hafnium, niobium, tantalum, vanadium, cobalt, chromium, and nickel. 7. The sputtering target according to claim 1, wherein an interface layer is formed at the boundary between the metal silicide phase and the silicon phase. 8. The sputtering target according to claim 7, wherein the thickness of the interface layer formed at the boundary between the metal silicide phase and the silicon phase is 100 to 10,000 Å. 9. The sputtering target according to claim 1, wherein the silicon phase contains at least one element selected from the group consisting of boron, phosphorus, antimony, and arsenic, and unavoidable elements, and the sputtering target has an electrical resistivity of 0.01 to 100 Ω·cm. 10. A method for manufacturing a silicon silicide having a fine mixed structure in which metal silicides (having a chemical composition of MSi ₂ , where M is a metal) are linked together in a chain to form a metal silicide phase, and silicon particles are linked together to form a silicon phase that exists discontinuously in the gaps between the metal silicides,
A method for producing a sputtering target having a carbon content of 100 ppm or less, comprising: I. mixing a metal powder (M) and a silicon powder (Si) into a Si/
A method for manufacturing a sputtering target, comprising: a step of preparing a mixed powder by mixing the powders so that the M atomic ratio is 2.0 to 4.0, II a step of filling the mixed powder into a molding die and heating it at a low temperature in a high vacuum to reduce carbon and oxygen, III a step of heating it in a high vacuum under low pressing pressure to synthesize and sinter a metal silicide phase, and IV a step of heating it in a high vacuum or in an inert gas atmosphere under high pressing pressure to a temperature just below the eutectic temperature to densify it. [Claim 11] A method for manufacturing a sputtering target according to claim 10, wherein a high-purity metal powder having a maximum particle size of 10 μm or less is used as the metal powder (M), and a high-purity silicon powder having a maximum particle size of 30 μm or less is used as the silicon powder (Si). 12. The method for producing a sputtering target according to claim 10, wherein a mixed powder of a metal powder and a silicon powder is subjected to reactive melt sintering, and silicide synthesis, sintering, and densification are carried out simultaneously. 13. The method for producing a sputtering target according to claim 12, wherein the reactive melt sintering is carried out by using a hot pressing method or a hot isostatic pressing method.