JP6005842B2 - Sputtering silicide target and method for manufacturing the same - Google Patents

Description

  The present invention relates to a sputtering silicide target and a manufacturing method thereof, and more particularly, to a high-density sputtering target used for forming a silicide film in a semiconductor device and a manufacturing method thereof.

  Polysilicon has been conventionally used as an electrode or wiring of a semiconductor device. However, with the miniaturization and high integration of semiconductor devices, signal propagation delay due to resistance has become a problem. On the other hand, the use of a material having a high melting point is required as an electrode for facilitating the formation of wiring and the like by the self-alignment method.

For this reason, metal silicide wirings and electrodes having a lower resistivity than polysilicon and having compatibility with the gate process are used. Examples of metal silicides include tungsten silicide (WSi _x ), molybdenum silicide (MoSi _x ), tantalum silicide (TaSi _x ), titanium silicide (TiSi _x ), cobalt silicide (CoSi _x ), chromium silicide (CrSi _x ), nickel Examples thereof include silicide (NiSi _x ).

  Usually, such a metal silicide thin film is formed by sputtering a sputtering silicide target. As the sputtering silicide target, if the molar ratio x is 2 or less, the film stress is high when the film is formed, and the film is peeled off. For this reason, a silicide target for sputtering having a silicon / metal molar ratio of more than 2 is often used.

  By the way, when sputtering using a silicide target, particles may be generated from the target. These adhere directly to the film on the substrate, or adhere to the wall or the like in the chamber, peel off after deposition, and reattach to the film, causing problems such as short-circuiting or disconnection of wiring. As the integration and miniaturization of electronic device circuits have progressed, the generation of particles has become a very serious problem.

Conventionally, attempts have been made to reduce the amount of particles generated from such a metal silicide target. For example, Patent Document 1 discloses a metal silicide having a mixed structure of a granular MSi ₂ phase and a Si phase as a matrix phase, and having an interface layer having a predetermined thickness at the boundary between the MSi ₂ phase and the Si phase. A sputtering target and a manufacturing method thereof are disclosed.

  Further, Patent Document 2 discloses a fine structure in which metal silicides are bonded in a chain to form a metal silicide phase, and silicon phases formed by bonding silicon particles are discontinuously present in the gaps between the metal silicides. Disclosure of a sputtering target characterized by having an excellent mixed structure and an aluminum content of 1 ppm or less, and disclosure of low generation of particles during sputtering due to high density and high strength doing.

  Further, in Patent Document 3 of the present applicant, the area ratio of the silicon phase appearing on the sputter surface is 23% or less, the density is 99% or more, and the work-affected layer on the surface is partially removed, and the surface A sputtering target characterized by having a roughness of more than 0.05 μm and 1 μm or less is disclosed, whereby the generation amount of initial particles can be greatly reduced as compared with the conventional technique.

  However, it is not possible to suppress the generation of particles simply by reducing the abundance of the coarse silicon phase appearing on the sputtered surface of the metal silicide target and removing the work-affected layer on the surface over time. It was newly recognized that it was sufficient.

JP-A-3-130360 JP-A-5-214523 JP-A-6-306595

  In view of the above problems, an object of the present invention is to provide a high-density silicide target for sputtering and a method for producing the same, in which the amount of particles generated during sputtering is small.

  In order to solve the above-mentioned problems, the present inventors have conducted intensive research, and as a result, sintering in a temperature region close to the melting point of silicon and reacting the molten silicon with the solid-phase silicide, It has become possible to produce a high-density sputtering silicide target with significantly reduced pores (vacancies), and when sputtered using this, it has been found that the amount of particles can be significantly reduced.

Based on such knowledge, the present invention
1) A silicide target for sputtering, wherein the number of pores having a size of 50 μm ² or more in the target is 10 or less per 0.25 mm ² ;
2) The silicide target for sputtering rig as described in 1) above, wherein the number of pores having a size of 1 μm ² or more in the target is 20 or less per 0.01 mm ² ;
3) The silicide target according to 1) or 2) above, wherein a spherical silicide phase occupies 90% or more per 0.01 mm ² ;
4) The silicide target according to any one of 1) to 3) above, wherein the relative density of the target is 98% or more,
5) The silicide target for sputtering rig according to any one of 1) to 4) above, wherein the target material is TaSi _x (x> 2.0),
6) A metal powder and a silicon powder are mixed and synthesized by heating to form a metal silicide powder. Then, the metal silicide powder is mechanically pulverized, and then the fine metal silicide powder and the fine silicon powder are predetermined. And a method for producing a silicide target for sputtering rigs, characterized in that the mixed powder is uniformly mixed so as to have a molar ratio of, and the mixed powder is hot-pressed and sintered at a temperature at which silicon melts.

  The silicide target for sputtering according to the present invention has an excellent effect that the generation of particles can be extremely reduced during sputtering by significantly reducing the pores present in the target. That is, the yield during film formation can be improved.

It is a structure | tissue image (magnification: 200 times) when the target surface of Example 1 is observed with a scanning electron microscope (SEM). It is a structure | tissue image (magnification: 1000 times) when the target surface of Example 1 is observed with a scanning electron microscope (SEM). It is a structure | tissue image (magnification: 200 times) when the target surface of Example 2 is observed with a scanning electron microscope (SEM). It is a structure | tissue image (magnification: 1000 times) when the target surface of Example 2 is observed with a scanning electron microscope (SEM). It is a structure | tissue image (magnification: 200 times) when the target surface of Example 3 is observed with a scanning electron microscope (SEM). It is a structure | tissue image (magnification: 1000 times) when the target surface of Example 3 is observed with a scanning electron microscope (SEM). It is a structure | tissue image (magnification: 200 times) when the target surface of the comparative example 1 is observed with a scanning electron microscope (SEM). It is a structure | tissue image (magnification: 1000 times) when the target surface of the comparative example 1 is observed with a scanning electron microscope (SEM). It is a structure | tissue image (magnification: 200 times) when the target surface of the comparative example 2 is observed with a scanning electron microscope (SEM). It is a structure | tissue image (magnification: 1000 times) when the target surface of the comparative example 2 is observed with a scanning electron microscope (SEM). It is a structure | tissue image (magnification: 200 times) when the target surface of the comparative example 3 is observed with a scanning electron microscope (SEM). It is a structure | tissue image (magnification: 1000 times) when the target surface of the comparative example 3 is observed with a scanning electron microscope (SEM).

Conventionally, in a silicide target for sputtering, a metal powder and a silicon powder are mixed and mixed so as to have a predetermined molar ratio, and after the silicide is synthesized by heating the mixed powder, the metal silicide powder is mixed with the eutectic temperature. and sintering at a temperature just below the T _S, it has been performed to produce a target. However, in the method in which sintering is performed in such a temperature range that the raw material powder does not melt, the powders (solids) are bonded (necked), but there are parts that cannot be combined, and this is the target as pores (holes) Many remained inside. Such pores cause abnormal discharge (arcing) during sputtering and increase the number of particles. The eutectic temperature Ts of the metal silicide is about 950 ° C. to 1400 ° C., although it varies depending on the composition.

  For this reason, the metal powder and the silicon powder are mixed and synthesized by heating to form a metal silicide powder, and then the metal silicide powder is mechanically pulverized to obtain the fine metal silicide powder and the fine silicon powder. Is uniformly mixed so as to have a predetermined molar ratio, and this mixed powder is sintered by hot pressing in a temperature region immediately below the melting point of silicon, that is, by sintering at a temperature at which silicon melts. In this case, the molten silicon can be filled with the gap, and a sputtering target with significantly reduced pores can be obtained. Furthermore, since the reaction between the solid phase and the liquid phase is superior to the reaction between the solid phase and the solid phase, a more uniform tissue can be obtained.

The silicide target for sputtering of the present invention can be manufactured as follows. First, metal powder and silicon powder are prepared. As the metal powder, a known material can be used as a silicide for a semiconductor device, and examples thereof include tantalum, molybdenum, tungsten, cobalt, and nickel.
Next, the metal powder and the silicon powder are mixed using a ball mill or the like, and this is heated and synthesized using a heating device such as a heat treatment furnace to obtain a metal silicide alloy. The conditions for synthesizing the silicide are slightly different depending on the composition, but it is preferable to set the atmosphere: vacuum and temperature: 800 to 1350 ° C.

The obtained metal silicide lump is finely pulverized using mechanical pulverization such as a jet mill so that the maximum particle diameter becomes 100 μm. A silicon fine powder having a maximum particle size of 100 μm, which is pulverized by jet mill, is mixed with the fine silicide powder so that the final target has the following molar ratio to obtain a mixed powder.
Ta / Si _x (x> 2.0), Mo / Si _x (x> 2.15), W / Si _x (x> 2.25), Co / Si _x (x> 2.2), Ni / Si _x (x> 2.2)

This mixed powder is hot-pressed in a temperature region where silicon melts to produce a sintered body. This is one of the important points in the present invention. For example, in the case of TaSi _x (x> 2.0), this temperature range is preferably in the range of 1385 to 1400 ° C., although it depends on the composition. If the sintering temperature is less than 1385 ° C., the silicon does not melt sufficiently. On the other hand, if the sintering temperature exceeds 1400 ° C., oversintering occurs and the pores increase, which is not preferable. . Although the melting point of silicon is about 1414 ° C., the melting point of the compound drops when it becomes a compound. Therefore, silicon melts in the above temperature range. The sintering pressure can be 250 to 350 kg / cm ² . And the silicide target for sputtering of this invention is producible by machining the sintered compact produced in this way to a desired shape.

A silicide target for sputtering can be manufactured by the above manufacturing process, but this manufacturing process shows an example, and the present invention does not invent this manufacturing process. Of course, it is possible, and the present invention includes all of them.
For example, in the above example, a target was prepared by sintering a mixed powder of silicide powder and silicon powder, but a mixed powder of silicide powder and metal powder adjusted to have a predetermined composition was sintered. And a target can also be produced.

In the silicide target for sputtering according to the present invention, the number of pores having a size of 50 μm ² or more in the target is 10 or less per 0.25 mm ² , and preferably the number of pores having a size of 1 μm ² or more is 0 in the target. No more than 20 per 01 mm ² . Thereby, abnormal discharge starting from coarse pores can be suppressed, and plasma during sputtering can be stabilized.
The pore size can be obtained by observing the cut target cross-section and measuring and calculating the cross-sectional area of the pore. However, since the pore has a volume, the observed pore does not necessarily have the maximum cross-sectional area, but any cross-sectional area of the pore may be included in the present invention as long as the above numerical range is included. It should be understood that it is included.

In the silicide target for sputtering according to the present invention, it is preferable that a spherical silicide phase occupies 90% or more per 0.01 mm ² in the target. Here, the spherical shape represents a solid shape including a true sphere, a pseudo true sphere, an oblate sphere, and a pseudo oblate sphere, and means that the ratio of the maximum value to the minimum value of the length from the center to the outer periphery is 2 or less. .
Within this range, similar characteristics can be obtained even if there are some irregularities on the outer periphery. Further, depending on the composition, the silicide phases may be combined and it may be difficult to confirm as a single phase. In such a case, the joint portion can be extended and measured in a virtual shape.

  Hereinafter, description will be made based on Examples and Comparative Examples. In addition, a present Example is an example to the last, and is not restrict | limited at all by this example. In other words, the present invention is limited only by the scope of the claims, and includes various modifications other than the examples included in the present invention.

Example 1
High purity tantalum powder and high purity silicon powder were mixed in a ball mill and heated in vacuum to obtain an alloy lump of TaSix (x = 2.0). This silicide lump was pulverized by jet mill to obtain a silicide powder having a maximum particle size of 100 μm. To this silicide powder, silicon powder having a maximum particle size of 100 μm obtained by jet milling is mixed so that the Si content in the target is 27.96 wt%, and the mixed powder is heated using a hot press device. Sintering was performed at a temperature of 1385 ° C., a press load of 300 kg / cm ² , and a holding time of 2 hours to produce a sintered body. A silicide target for sputtering having a diameter of 300 mm and a thickness of 6.35 mm was produced by machining the sintered body.

The cross section of the sputtering target thus produced was polished and observed at any five locations on the target using a scanning electron microscope (SEM) (FIGS. 1 and 2). As a result, there were no pores of 50 μm ² or more in a visual field of 0.25 mm ² . The number of pores of 1 μm ² or more in the visual field of 0.01 μm ² was 1 on average. In addition, a spherical silicide phase in the field of view of 0.01 mm ² occupied 99% or more. The relative density of the target determined by the Archimedes method was 99.9%.
Next, this target was attached to a sputtering apparatus, magnetron sputtering was performed under the following conditions, and the number of particles having a diameter of 0.3 μm or more attached to the tantalum silicide thin film on the Si substrate surface was measured. As a result, 70 pieces were obtained.
(Sputtering conditions)
Atmospheric gas: Ar gas Atmospheric pressure: 1 pa
Sputter output: 1KW
Distance between target and Si substrate: 5cm
Sputtering time: 30 seconds

(Example 2)
High purity tantalum powder and high purity silicon powder were mixed in a ball mill and heated in vacuum to obtain an alloy lump of TaSix (x = 2.0). This silicide lump was pulverized by jet mill to obtain a silicide powder having a maximum particle size of 100 μm. A silicon powder having a maximum particle size of 100 μm by pulverizing with a jet mill is mixed with the silicide powder so that the Si content in the target is 28.73 wt%, and the mixed powder is heated using a hot press apparatus. Sintering was performed at a temperature of 1385 ° C., a press load of 290 kg / cm ² , and a holding time of 3 hours to produce a sintered body. A silicide target for sputtering having a diameter of 300 mm and a thickness of 6.35 mm was produced by machining the sintered body.

The cross section of the sputtering target thus produced was polished and observed at any five locations on the target using a scanning electron microscope (SEM) (FIGS. 3 and 4). As a result, there were no pores of 50 μm ² or more in a visual field of 0.25 mm ² . The average number of pores of 1 μm ² or more in the visual field of 0.01 μm ² was zero. In addition, a spherical silicide phase in the field of view of 0.01 mm ² occupied 99% or more. The relative density of the target determined by the Archimedes method was 99.8%. Next, this target was attached to a sputtering apparatus, and magnetron sputtering was performed under the same conditions as in Example 1 to measure the number of particles having a diameter of 0.3 μm or more attached to the tantalum silicide thin film on the Si substrate surface. As a result, it was 58 pieces.

(Example 3)
High purity tantalum powder and high purity silicon powder were mixed in a ball mill and heated in vacuum to obtain an alloy lump of TaSix (x = 2.0). This silicide lump was pulverized by jet mill to obtain a silicide powder having a maximum particle size of 100 μm. A silicon powder having a maximum particle size of 100 μm is mixed with the silicide powder so that the Si content in the target is 27.51 wt%, and the mixed powder is heated using a hot press apparatus. Sintering was performed at a temperature of 1390 ° C., a press load of 310 kg / cm ² , and a holding time of 2 hours to produce a sintered body. A silicide target for sputtering having a diameter of 300 mm and a thickness of 6.35 mm was produced by machining the sintered body.

The cross section of the sputtering target thus produced was polished and observed at any five locations on the target using a scanning electron microscope (SEM) (FIGS. 5 and 6). As a result, there were no pores of 50 μm ² or more in a visual field of 0.25 mm ² . The average number of pores of 1 μm ² or more in the visual field of 0.01 μm ² was three. In addition, a spherical silicide phase in the field of view of 0.01 mm ² occupied 99% or more. The relative density of the target determined by the Archimedes method was 98.9%. Next, this target was attached to a sputtering apparatus, and magnetron sputtering was performed under the same conditions as in Example 1 to measure the number of particles having a diameter of 0.3 μm or more attached to the tantalum silicide thin film on the Si substrate surface. As a result, 62 pieces were obtained.

(Comparative Example 1)
High purity tantalum powder and high purity silicon powder were mixed in a ball mill and heated in vacuum to obtain an alloy lump of TaSix (x = 2.0). This silicide lump was pulverized by jet mill to obtain a silicide powder having a maximum particle size of 100 μm. To this silicide powder, a silicon powder having a maximum particle size of 100 μm by pulverization with a jet mill is mixed so that the Si content in the target is 28.76 wt%, and the mixed powder is heated using a hot press apparatus. The sintered body was produced by sintering at a temperature of 1370 ° C., a press load of 280 kg / cm ² , and a holding time of 2 hours. A silicide target for sputtering having a diameter of 300 mm and a thickness of 6.35 mm was produced by machining the sintered body.

The cross section of the sputtering target thus produced was polished and observed at any five locations on the target using a scanning electron microscope (SEM) (FIGS. 7 and 8). As a result, there were 15 pores of 50 μm ² or more in a visual field of 0.25 mm ² . The average number of pores of 1 μm ² or more in the visual field of 0.01 μm ² was 25. In addition, a spherical silicide phase in the visual field of 0.01 mm ² occupied 43%. The relative density of the target determined by the Archimedes method was 97.2%. Next, this target was attached to a sputtering apparatus, and magnetron sputtering was performed under the same conditions as in Example 1 to measure the number of particles having a diameter of 0.3 μm or more attached to the tantalum silicide thin film on the Si substrate surface. As a result, it was 203 pieces.

(Comparative Example 2)
High purity tantalum powder and high purity silicon powder were mixed in a ball mill and heated in vacuum to obtain an alloy lump of TaSix (x = 2.0). This silicide lump was pulverized by jet mill to obtain a silicide powder having a maximum particle size of 100 μm. A silicon powder having a maximum particle size of 100 μm is mixed with the silicide powder so that the Si content in the target is 27.96 wt%, and the mixed powder is heated using a hot press apparatus. The sintered body was produced by sintering at a temperature of 1365 ° C., a press load of 290 kg / cm ² , and a holding time of 3 hours. A silicide target for sputtering having a diameter of 300 mm and a thickness of 6.35 mm was produced by machining the sintered body.

The cross section of the sputtering target thus produced was polished and observed at any five locations on the target using a scanning electron microscope (SEM) (FIGS. 9 and 10). As a result, there were 5 pores of 50 μm ² or more in a visual field of 0.25 mm ² . The number of pores of 1 μm ² or more in the visual field of 0.01 μm ² was 18 on average. Further, the spherical silicide phase in the field of view of 0.01 mm ² occupied 73%. The relative density of the target determined by the Archimedes method was 94.5%. Next, this target was attached to a sputtering apparatus, and magnetron sputtering was performed under the same conditions as in Example 1 to measure the number of particles having a diameter of 0.3 μm or more attached to the tantalum silicide thin film on the Si substrate surface. As a result, it was 174.

(Comparative Example 3)
High purity tantalum powder and high purity silicon powder were mixed in a ball mill and heated in vacuum to obtain an alloy lump of TaSix (x = 2.0). This silicide lump was pulverized by jet mill to obtain a silicide powder having a maximum particle size of 100 μm. To this silicide powder, a silicon powder having a maximum particle size of 100 μm by pulverizing with a jet mill is mixed so that the Si content in the target is 20.46 wt%, and the mixed powder is heated using a hot press device. Sintering was performed by sintering at a temperature of 1405 ° C., a press load of 310 kg / cm ² , and a holding time of 1 hour. A silicide target for sputtering having a diameter of 300 mm and a thickness of 6.35 mm was produced by machining the sintered body.

The cross section of the sputtering target thus produced was polished and observed at any five locations on the target using a scanning electron microscope (SEM) (FIGS. 11 and 12). As a result, the number of pores of 50 μm ² or more in the visual field of 0.25 mm ² was zero. The average number of pores of 1 μm ² or more in the visual field of 0.01 μm ² was 23. In addition, a spherical silicide phase in the field of view of 0.01 mm ² occupied 99% or more. The relative density of the target determined by the Archimedes method was 99.7%. Next, this target was attached to a sputtering apparatus, and magnetron sputtering was performed under the same conditions as in Example 1 to measure the number of particles having a diameter of 0.3 μm or more attached to the tantalum silicide thin film on the Si substrate surface. As a result, 125 pieces were obtained.

The sputtering target of the present invention has an excellent effect that the amount of particles generated at the time of sputtering can be reduced and the yield at the time of film formation can be improved. Therefore, it is useful as a sputtering target for forming a silicide film used as an electrode or wiring of a semiconductor device.

Claims (5)

In 50 [mu] m ² or more size pores at 0.25 mm 10 per ² or less with the target, in the target 1 [mu] m ² or more pores having a size of Ri der 0.01 mm ² per 20 or less, spherical A silicide target for sputtering, wherein the silicide phase occupies 90% or more per 0.01 mm ² . 50 [mu] m ² or more in size in the target pore 10 below is 0.25 mm ² per having, of 1 [mu] m ² or more in the target der pores than 20 per 0.01 mm ² having a size is, the target A silicide target having a relative density of 98% or more . In 50 [mu] m ² or more size pores at 0.25 mm 10 per ² or less with the target, in the target 1 [mu] m ² or more pores having a size of Ri der 0.01 mm ² per 20 or less, spherical A silicide target characterized in that the silicide phase occupies 90% or more per 0.01 mm ^{2 and} the relative density of the target is 98% or more .   4. The silicide target for sputtering according to claim 1, wherein the target material is made of TaSix (x> 2.0). 5.   A metal powder and a silicon powder are mixed and synthesized by heating to form a metal silicide powder. Then, the metal silicide powder is mechanically pulverized, and then the fine metal silicide powder and the fine silicon powder are mixed with a predetermined molar amount. A method for producing a silicide target for sputtering, characterized in that the mixed powder is uniformly mixed so as to obtain a ratio, and the mixed powder is hot-pressed and sintered at a temperature at which silicon melts.