JPH04308081A - Target for sputtering - Google Patents

Abstract

PURPOSE:To reduce the fraction defective of products by specifying the percentage of single crystals and/or macro-grains of the constituents of a target. CONSTITUTION:When plural target chips 1, 2 having different compsns. are combined, integrated and set on a substrate 4 to form a target for sputtering, the percentage of single crystals and/or macro-grains of the constituents of the target is regulated to >=20% by area in a cross section parallel to the surface to be sputtered and two or more among high m.p. metals and Si are used as the materials of the target chips. The high m.p. metals are W, Mo, Ta and Nb. Si and W or W and Ti are used for the material of target chip. The productivity of the target can be improved.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a sputtering target, which is used in film formation by sputtering to avoid attachment of fine particles, such as gate electrodes, wiring, and barrier metals of ultra-LSIs. The present invention relates to a sputtering target used for forming thin films, etc.

0002

[Prior art and its problems] In recent years, with the increasing integration of VLSIs, materials containing high-melting point metals such as tungsten, molybdenum, titanium, tantalum, and niobium are being used for VLSI electrode materials, wiring materials, barrier metal materials, etc. It is often used as. One useful method for thinning films of various materials is sputtering, and it is well known that this method is widely used in current VLSI manufacturing processes.

[0003] The prior art and its problems will be explained below by taking as an example the formation of a silicide film of a refractory metal by sputtering.

Conventionally, when forming the above-mentioned silicide thin film by the sputtering method, a sintered target obtained by pressure-sintering a mixed powder of silicide and silicon has been used. Sputtering film formation using such a sintered target has the following problems.

The first problem is the incorporation of impurities into the silicide film. This is the crushing of raw materials during target production.
Also, gas components and metal impurities inevitably get mixed into the target during the preparation process of raw material powder. These impurities are incorporated into the silicide film during sputtering film formation, causing malfunctions of VLSIs, and causing problems such as significantly lowering the production yield of VLSIs.

The second problem is the generation of particles during sputtering. Particles are fine particles scattered from the target and deposited on the wafer when the target is sputtered. The presence of particles on the wafer causes defects such as short circuits and disconnections in wiring and electrodes, significantly reducing production yield. Normally, the allowable size of particles is 1/10 or less of the wiring width. For example, in a 4 megabit LSI with a wiring width of about 0.8 μm,
．． It must be less than 0.08 μm. In sputtering film formation using a sintered target as described above, particle generation is significant and has become a major problem.

[0007] In order to solve the first problem mentioned above, a target piece in which polycrystalline silicon and polycrystalline high melting point metal are formed so that they have an appropriate area ratio on the sputtering surface is combined and integrated. Mosaic sputtering targets have been proposed and used. Since these mosaic targets are manufactured without going through a pulverization process or a powder adjustment process, it is possible to avoid contamination with impurities and is a useful means for obtaining a highly pure silicide film. On the other hand, although a slight decrease in the amount of particles generated was observed compared to conventional sintered targets, this is not a sufficient solution for practical use. That is, the above-mentioned second problem remains serious, and there has been a strong desire to develop a target that can suppress particle generation.

[0008] The above explanation has been given using the example of forming a silicide film of high melting point metals, but similar problems generally occur with other combinations of high melting point metals as well.

[0009]

[Means for Solving the Problems] As a result of intensive studies in order to solve these problems, the present inventors have found that by using a certain proportion of single crystals or giant grains of constituent substances in the target material. The present invention was completed based on the knowledge that particles can be suppressed.

That is, the present invention provides a sputtering target in which a plurality of target pieces having different compositions are combined and integrated and placed on a substrate, in which a proportion of single crystals and/or giant grains of the target constituent material is on the sputtering surface. To provide a sputtering target characterized by an area ratio of 20% or more in a cross section of the target parallel to . Here, giant grains have a grain size of 5
It means crystal grains of mm or more.

The target of the present invention will be explained in more detail below.

The target material of the present invention includes a metal consisting of single crystals and/or giant grains, or single crystals and/or giant grains. Also, in particular, silicon and refractory metals such as tungsten, molybdenum, titanium, tantalum, niobium, hafnium, zirconium, vanadium, rhenium,
It is also a preferred embodiment to use two or more selected from the group consisting of chromium, platinum, iridium, osmium, and rhodium (the high melting point metal in the present invention means a metal with a melting point of 1400° C. or higher). There are no limitations on the method for producing single crystals or giant grains used as the target material of the present invention, but generally, the floating zone method, the melting/solidification method such as the Czochralski method, the secondary recrystallization method, etc. can be considered.

[0013] These materials are made into targets by placing target pieces of different compositions, for example, 1/2 each side by side, or usually arranging them in a mosaic shape, and bonding them directly to a backing plate using a solder material such as indium. . Here, the ratio of target pieces with different compositions used corresponds to the composition of the target film, but at least one single crystal or giant grain of the constituent material has an area ratio of the ratio limited in the present invention. It is necessary to configure it so that The shape of the target of the present invention is not particularly limited,
It can be either circular or square. In addition, its size is, for example, in the case of a circular shape, a diameter of 75 to 300 mm and a thickness of 3 to 10 mm.
That's about it.

[0014] The fact that single crystals or giant grains of constituent substances occupy 20% or more of the area ratio in all cross sections of the target parallel to the sputtering plane means that the monocrystalline or giant grains of the constituent substances occupy 20% or more of the area ratio in all cross sections of the target parallel to the sputtering plane. This means that the total area occupied by one crystal or a plurality of giant grains is 20% or more of the area of the sputtering surface. Although the effect of the present invention is not completely absent even when the above-mentioned area ratio is less than 20%, a remarkable effect appears when the area ratio exceeds 20%. Further, at 20% or more, the higher the above-mentioned area ratio is, the higher the effect becomes.

The reason why particle generation on the film forming surface is suppressed by using the present invention is not necessarily clear, but it is thought to be as follows.

First, the use of single crystals or giant grains has dramatically reduced the number of fine voids in the target. The fine voids in the target induce abnormal discharge during sputtering, which is considered to be one of the causes of particle generation. In conventional sintered targets and mosaic targets using polycrystalline materials, countless fine voids exist at grain boundaries and the like. On the other hand, since single crystals and giant grains are themselves high-density materials, the above-mentioned adverse effects are drastically reduced.

The second method is to reduce segregated impurities in the target by using single crystals or giant grains. It is said that segregated impurities in the target are likely to induce abnormal discharge. The present inventors have completed the present invention based on the knowledge that the reduction of segregated impurities can be achieved by using single crystals or giant grains. Polycrystals have been used not only for sintered targets but also for conventional mosaic targets, but these polycrystals are generally produced by powder metallurgy or melting methods, and either method requires removal of gas components. However, gas components such as nitrogen, oxygen, and carbon dioxide tend to remain in the grain boundaries. These gas components combine with other metal elements present in the base material or as impurities to produce metal oxides, metal nitrides, metal carbides, etc., which exist as segregated impurities at grain boundaries and cause abnormal discharge. This is thought to be the cause. It goes without saying that impurities mixed in during the production of conventional sintered targets were also a cause of abnormal discharge. On the other hand, the target of the present invention has significantly fewer grain boundaries than conventional targets, so gas components such as nitrogen, oxygen, and carbon dioxide are uniformly dissolved in the base material, reducing the segregated impurities mentioned above. do. As a result, it is thought that abnormal discharge during sputtering was avoided and the number of particles generated was drastically reduced.

[0018] By using the target of the present invention, it is also possible to improve the film formation rate. Since the film-forming speed is directly related to the productivity during VLSI production, its improvement is very beneficial industrially. In order to increase the film formation rate, it is sufficient to increase the input power during sputtering. However, as the input power increases, the frequency of abnormal discharge also increases, and a large amount of particles are generated, making it difficult to improve the film formation rate using conventional techniques. On the other hand, in the target of the present invention, since the causes of abnormal discharge are dramatically eliminated, the input power can be increased while suppressing the generation of particles, and the film formation rate can be improved.

[0019]

As described above, according to the present invention, particles generated during sputtering can be suppressed, and furthermore, the film formation rate can be improved while suppressing particles. This has tremendous industrial value, such as improved productivity and reduced product defect rate, in manufacturing sites where particles have a large effect on yield, such as for VLSIs. In addition, the target of the present invention does not require pulverization or powder adjustment processes at the manufacturing stage, so it can be easily purified to a higher purity than conventional mosaic-shaped targets, and can be used for ultra-LS.
Ideal for I production. Furthermore, the effects of the present invention are expected to be applicable to mosaic targets in general, regardless of the material.

[0020]

[Examples] The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to these in any way.

[0021]

[Example 1] Shape as shown in Figure 1, purity 99.99
Using a 9% single-crystal tungsten plate and a 99.999% pure single-crystal silicon plate,
) to produce a tungsten-silicon mosaic target in which the area ratio of the tungsten portion (1 in FIG. 1) to the silicon portion (2 in FIG. 1) was 1:3.44.

The crystal planes of the tungsten part and the silicon part were the (111) plane and the (110) plane, respectively. The size of the target is 150 mm in diameter and 5 mm in thickness. Using this target, a thin film was formed using a DC magnetron sputtering device under the following conditions.

Input power: 600W Film forming time: 10 minutes Ar pressure: 0.5 Pa Substrate: 6 inch φ Si wafer (100)
After surface film formation, particles of 0.1 μm or more existing on the substrate were measured using a commercially available wafer/dust inspection device. The measurement results are shown in Table 1.

[0024]

[Example 2] The purity, area ratio, arrangement, and size are the same as in Example 1, the silicon part is entirely made of single crystal silicon, and the tungsten part has 20 giant grains (crystal planes are random).
A tungsten-silicon mosaic target was produced in the same manner as in Example 1, in which 80% of the crystal grains with a grain size of less than 5 mm (crystal planes are random) accounted for 80% of the target. The crystal plane of the silicon portion is the (110) plane.

Using this target, a film was formed under the same conditions as in Example 1, and particle measurements were performed. The measurement results are shown in Table 1.

[0026]

[Example 3] Same purity, area ratio, arrangement, and size as Example 1, silicon part has giant grains (crystal planes are random)
crystal grains with a grain size of less than 5 mm (random crystal faces) account for 75%, while in the tungsten part, giant grains (with random crystal faces) account for 25%, and grains with a grain size of less than 5 mm account for 75%. A tungsten-silicon mosaic target in which crystal grains (crystal planes are random) accounted for 75% was produced in the same manner as in Example 1.

Using this target, a film was formed under the same conditions as in Example 1, and particle measurements were performed. The measurement results are shown in Table 1.

[0028]

[Example 4] Using the target of Example 1, a film was formed under the same conditions as in Example 1 except that the input power was 1000 W, and particle measurements were performed. The measurement results are shown in Table 1.

[0029]

[Example 5] Shape as shown in Figure 2, purity 99.99
Using a 9% single-crystal tungsten plate and a 99.999% pure single-crystal titanium plate, we created a backing plate (4 in Figure 2).
A tungsten-titanium based mosaic target having an area ratio of 2.10:1.00 of the tungsten portion (1 in FIG. 2) and the titanium portion (3 in FIG. 2) was manufactured by bonding thereon.

The (111) crystal plane was used for both the tungsten part and the titanium part. The size of the target is 150 mm in diameter and 5 mm in thickness. Using this target, a thin film was formed using a DC magnetron sputtering device under the following conditions.

Input power: 700W Film forming time: 8 minutes Ar pressure: 0.5 Pa Substrate: 6 inch φ Si wafer (100)
After surface film formation, particles of 0.1 μm or more existing on the substrate were measured using a commercially available wafer/dust inspection device. The measurement results are shown in Table 2.

[0032]

[Example 6] The purity, area ratio, arrangement, and size are the same as in Example 5. Giant grains (crystal planes are random) account for 20% of the titanium part, and crystal grains with a grain size of less than 5 mm (crystal planes are random) ) accounted for 80% of the target, and the tungsten portion was entirely made of single-crystal tungsten. The crystal plane of the tungsten portion is the (111) plane.

Using this target, a film was formed under the same conditions as in Example 5, and particle measurements were performed. The measurement results are shown in Table 2.

[0034]

[Example 7] The purity, area ratio, arrangement, and size are the same as in Example 5. Giant grains (crystal planes are random) account for 25% of the titanium part, and crystal grains with a grain size of less than 5 mm (crystal planes are random) ) account for 75%, and on the other hand, giant grains (crystal planes are random) account for 25% of the tungsten part, with a grain size of 5.
A tungsten-titanium mosaic target in which 75% of crystal grains less than mm (crystal planes are random) was produced in the same manner as in Example 5.

Using this target, a film was formed under the same conditions as in Example 5, and particle measurements were performed. The measurement results are shown in Table 2.

[0036]

Example 8 A film was formed under the same conditions as in Example 5, except that the target of Example 5 was used and the input power was 1200 W, and particle measurements were performed. The measurement results are shown in Table 2.

[0037]

[Comparative Example 1] Same purity, area ratio, arrangement and size as Example 1, silicon part has huge grains (crystal planes are random)
crystal grains with a grain size of less than 5 mm (random crystal faces) account for 85%, while in the tungsten part, giant grains (with random crystal faces) account for 15%, and grains with a grain size of less than 5 mm account for 85%. A tungsten-silicon mosaic target in which crystal grains (crystal planes are random) accounted for 85% was produced in the same manner as in Example 1.

Using this target, a film was formed under the same conditions as in Example 1, and particle measurements were performed. The measurement results are shown in Table 1.

[0039]

[Comparative Example 2] A tungsten-silicon mosaic target made of polycrystalline tungsten and polycrystalline silicon and having the same purity, area ratio, arrangement, and size as in Example 1 was used as a conventional product, and under the same conditions as in Example 1. A film was formed. This target does not contain single crystals or macrograins within the meaning of the invention. After film formation, the same particle measurement as in Example 1 was performed. The measurement results are shown in Table 1.

[0040]

[Comparative Example 3] Using the conventional target of Comparative Example 2, a film was formed in the same manner as in Example 4, and particle measurements were performed. The measurement results are shown in Table 1.

[0041]

[Comparative Example 4] Conventional product with a molar ratio of tungsten and silicon of 1:2.75, purity of 99.999%, and relative density of 99%.
Using a sintered tungsten silicide target of the same size as in Example 1, a film was formed under the same conditions as in Example 1, and particle measurements were performed. The measurement results are shown in Table 1.

[0042]

[Comparative Example 5] Using the conventional target of Comparative Example 4, a film was formed in the same manner as in Example 4, and particle measurements were performed. The measurement results are shown in Table 1.

[0043]

[Comparative Example 6] The purity, area ratio, arrangement, and size are the same as in Example 5. In the titanium part, giant grains (crystal planes are random) account for 15%, and crystal grains with a grain size of less than 5 mm (crystal planes are random) ) account for 85%, and on the other hand, giant grains (crystal planes are random) account for 15% of the tungsten part, with a grain size of 5.
A tungsten-titanium mosaic target in which 85% of crystal grains less than mm (crystal planes are random) was produced in the same manner as in Example 5.

Using this target, a film was formed under the same conditions as in Example 5, and particle measurements were performed. The measurement results are shown in Table 2.

[0045]

[Comparative Example 7] A tungsten-titanium based mosaic target made of polycrystalline tungsten and polycrystalline titanium was used as a conventional product and had the same purity, area ratio, arrangement, and size as in Example 5, and under the same conditions as Example 5. A film was formed. This target does not contain single crystals or macrograins within the meaning of the invention. After film formation, the same particle measurement as in Example 5 was performed. The measurement results are shown in Table 2.

[0046]

[Comparative Example 8] Using the target of Comparative Example 7, a film was formed in the same manner as in Example 8, and particle measurements were performed. The measurement results are shown in Table 2.

[0047]

[Comparative Example 9] Conventional product with a molar ratio of tungsten and titanium of 2.34:1.00, purity of 99.999%, and relative density of 9
Using a sintered tungsten-titanium target of 9% and the same size as in Example 5, a film was formed under the same conditions as in Example 5, and particle measurements were performed. The measurement results are shown in Table 2.

[0048]

[Comparative Example 10] Using the target of Comparative Example 9, a film was formed in the same manner as in Example 8, and particle measurements were performed. The measurement results are shown in Table 2.

Table 1 Single crystal/giant grain
Input power Number of particles generated 2)
Occupied area ratio 1) (%) (W)
(%)
Example 1 100
600 10
Example 2 82
600 15 Example 3 25 60
0 30 Example 4
100 1000
13 Comparative example 1
15 600
76 Comparative Example 2
0 600
100 Comparative Example 3 0
1000
180 Comparative Example 4 0
600 30
5 Comparative example 5 0
1000 513
1): Area ratio occupied by single crystals and giant grains on the sputtering surface of the target 2): Comparative example 2
Relative values for the results Table 2 Single crystal/giant grains
Input power Number of particles generated 2)
Occupied area ratio 1) (%) (W)
(%)
Example 5 100
700
8 Example 6 74
700 15 Example 7 25 7
00 28 Example 8
100 1200
13 Comparative Example 6
15 700
91 Comparative Example 7
0 700
100 Comparative Example 8 0
1200
195 Comparative Example 9 0
700 2
85 Comparative Example 10 0
1200 476
1): Area ratio occupied by single crystals and giant grains on the sputtering surface of the target 2): Comparative example 7
Relative value for the result of

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram of a tungsten-silicon mosaic target in an embodiment of the present invention.

FIG. 2 is a conceptual diagram of a tungsten-titanium mosaic target in an embodiment of the present invention.

[Explanation of symbols]

1: Tungsten part 2: Silicon part 3: Titanium part 4: Target backing plate

Claims (5)

[Claims] [Claim 1] A sputtering target formed by combining and integrating a plurality of target pieces having different compositions and placing them on a substrate, wherein a single crystal and/or
Alternatively, a sputtering target characterized in that the proportion of giant grains is 20% or more in the cross section of the target parallel to the sputtering surface. 2. The sputtering target according to claim 1, wherein the target piece material is two or more selected from the group consisting of a high melting point metal and silicon. Claim 3: The high melting point metal is tungsten, molybdenum,
The sputtering target according to claim 2, which is titanium, tantalum, or niobium. 4. The sputtering target according to claim 1, wherein the target piece materials are silicon and tungsten. 5. The sputtering target according to claim 1, wherein the target piece materials are tungsten and titanium.