JP3134340B2 - Sputtering target - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sputtering target, and in a film formation by sputtering, particularly used as a film for preventing adhesion of fine particles (particles), for example, as a gate electrode, a wiring, and a barrier metal of a super LSI. The present invention relates to a sputtering target used for forming a thin film and the like.

[0002]

2. Description of the Related Art In recent years, with the increase in integration of VLSI, materials containing high melting point metals such as tungsten, molybdenum, titanium, tantalum, and niobium have been used as electrode materials, wiring materials, and barrier metal materials of VLSI. It has been heavily used. One useful method of thinning such various materials is a film forming method by sputtering, and it is well known that this method is widely used in the current VLSI manufacturing process.

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

Conventionally, when the above-mentioned silicide thin film is formed by a sputtering method, a sintered target obtained by sintering a mixed powder of silicide and silicon under pressure has been used. Sputter film formation using such a sintered body target has the following disadvantages and is a problem.

The first problem is that impurities are mixed into the silicide film. This is the crushing of raw materials during target production,
In addition, gas components and metallic impurities are inevitably mixed into the target in the step of adjusting the raw material powder. These impurities are incorporated into the silicide film during the film formation by sputtering, causing the operation failure of the VLSI, and causing a problem such as remarkably lowering the production yield of the VLSI.

The second problem is the generation of particles during sputtering. Particles are particles that are 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-circuiting and disconnection of wiring and electrodes, and significantly lowers the production yield. Normally, the allowable size of particles is set to 1/10 or less of the wiring width. For example, in a 4-megabit LSI having a wiring width of about 0.8 μm, it must be 0.08 μm or less. Particle formation is remarkable in sputtering film formation using the above-mentioned sintered body target, which is a major problem.

[0007] In order to solve the first problem described above, a polycrystalline body of silicon and a polycrystalline body of a refractory metal are combined by combining target pieces formed so as to have an appropriate area ratio on a sputtering surface. Mosaic sputtering targets have been proposed and used. Since these mosaic-like targets are manufactured without a pulverizing step and a powder adjusting step, impurities can be prevented from being mixed therein, and this is a useful means for obtaining a high-purity silicide film. On the other hand, although the amount of generated particles is slightly reduced as compared with the conventional sintered body target, it has not been sufficiently solved for practical use. That is, the second problem described above is still serious, and the development of a target capable of suppressing the generation of particles has been eagerly desired.

As described above, the formation of a silicide film of a high melting point metal has been described as an example. However, in general, similar inconveniences also occur with materials of other combinations of the high melting point metals, which are problematic.

[0009]

[Means for Solving the Problems] The present inventors have conducted intensive studies in order to solve such problems, and as a result, the use of a single crystal or a large grain of a constituent material in a target material at a certain ratio or more has been considered. It was found that the suppression of particles was achieved, and the present invention was completed.

That is, according to the present invention, in a sputtering target in which a plurality of target pieces having different compositions are combined and integrated and mounted on a substrate, the ratio of a single crystal and / or a large grain of the target constituent material occupies the sputtering surface. A sputtering target characterized by having an area ratio of 20% or more in a cross section of the target parallel to the target. Here, a giant particle means a particle size of 5
It means crystal grains of not less than mm.

Hereinafter, the target of the present invention will be described in more detail.

The target material of the present invention contains a metal composed of single crystals and / or giant grains, or a single crystal and / or giant grains. Also, in particular, use of two or more kinds selected from the group consisting of silicon and refractory metals such as tungsten, molybdenum, titanium, tantalum, niobium, hafnium, zirconium, vanadium, rhenium, chromium, platinum, iridium, osmium, and rhodium. (The high melting point metal in the present invention is 1400 ° C.
It means a metal having the above melting point). There is no particular limitation on the method for producing single crystals or giant grains used as the target material of the present invention. Generally, a melting / solidification method such as a floating zone method or a Czochralski method, a secondary recrystallization method, or the like can be considered.

For these materials, target pieces having different compositions are juxtaposed, for example, by 1/2, or are usually arranged in a mosaic shape, and are directly bonded to a backing plate using a solder material such as indium to obtain a target. . Here, the usage ratio of target pieces with different compositions is
Although the composition is set to correspond to the composition of the target film, it is necessary that at least one kind of the single crystal or the giant grains of the constituent material has an area ratio limited by the present invention. The shape of the target of the present invention is not particularly limited, and may be circular or square. For example, in the case of a circular shape, the size is 75 to 300 mm in diameter and 3 to 10 in thickness.
mm.

The fact that a single crystal or a giant grain of a constituent material occupies an area ratio of 20% or more in any cross section of the target parallel to the sputtering surface means that a single substance group of the target group having a cross section parallel to the sputtering surface. It 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. Even when the above-mentioned area ratio is less than 20%, the effect of the present invention is not completely absent, but a remarkable effect appears from the vicinity of more than 20%. Further, at 20% or more, the effect increases as the area ratio increases.

The reason why the present invention suppresses the generation of particles on the film formation surface is not necessarily clear, but is considered as follows.

First, it is pointed out that the use of single crystals or giant grains drastically reduces fine voids in the target. Fine voids in the target induce abnormal discharge during sputtering, which is considered to be a cause of particle generation. In a conventional sintered body target or a mosaic target using a polycrystalline body, countless fine voids exist at a grain boundary or the like. On the other hand, since the single crystal and the giant grain are themselves a high-density material, the above-mentioned adverse effects are drastically reduced.

Second, segregated impurities in the target can be reduced 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 found that segregation impurities can be reduced by using single crystals or giant grains, and have completed the present invention. Polycrystalline materials have been used for conventional mosaic targets as well as sintered targets, but these polycrystalline materials are generally produced by powder metallurgy or melting methods.Either method removes gas components. It is difficult, and gas components such as nitrogen, oxygen and carbon dioxide tend to remain at the crystal grain boundaries. These gas components combine with the base metal or other metal elements present as impurities to form metal oxides, metal nitrides, metal carbides, etc., which are present as segregated impurities at the grain boundaries and cause abnormal discharge. It is thought to be the cause. Needless to say, impurities mixed during the production of the conventional sintered body target also contributed to abnormal discharge. On the other hand, since the target of the present invention has much smaller grain boundaries than the conventional target, gas components such as nitrogen, oxygen and carbon dioxide are uniformly dissolved in the base material, and the segregated impurities described above are reduced. I do. As a result, it is considered that abnormal discharge during sputtering was avoided, and the number of generated particles was drastically reduced.

When the target of the present invention is used, an improvement in the film forming speed can be achieved. Since the deposition rate is directly related to the productivity in the production of VLSI, its improvement is very useful industrially. In order to increase the deposition rate, the power input during sputtering may be increased. However, the frequency of abnormal discharge increases with an increase in input power, and a large amount of particles are generated. Therefore, it has been difficult to improve the film forming speed by the conventional technology. On the other hand, in the target of the present invention, since the cause of the abnormal discharge is drastically removed, the input power can be increased while suppressing the generation of particles, and the deposition rate can be improved.

[0019]

As described above, according to the present invention, particles generated during sputtering are suppressed, and the film formation rate can be improved while suppressing particles. As a result, at a manufacturing site where particles greatly affect the yield, such as VLSI, its industrial value such as improvement in productivity and reduction in product defect rate is enormous. Further, since the target of the present invention does not require a pulverization and powder adjustment process in the production stage, it is easy to purify the same or more easily than the conventional mosaic target, and the ultra LS
Ideal for I manufacturing. In addition, the effects of the present invention are expected to be applicable to mosaic targets in general, regardless of the substance.

[0020]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.

[0021]

Embodiment 1 The shape shown in FIG.
Using a 9% single crystal tungsten plate and a 99.999% purity single crystal silicon plate, bonding is performed on a backing plate (4 in FIG. 1) to form a tungsten portion (1 in FIG. 1).
A tungsten-silicon-based mosaic target having an area ratio of the silicon part (2 in FIG. 1) of 1: 3.44 was manufactured.

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

Input power: 600 W Film formation time: 10 minutes Ar pressure: 0.5 Pa Substrate: 6 inch φ Si wafer (100) surface After film formation, particles of 0.1 μm or more existing on the substrate are commercially available wafers.・ Measured with a dust inspection device. Table 1 shows the measurement results.

[0024]

Example 2 The purity, area ratio, arrangement and size were the same as in Example 1, the silicon portion was all made of single-crystal silicon, and the tungsten portion had two giant grains (random crystal faces).
A tungsten-silicon-based mosaic target was prepared in the same manner as in Example 1, in which 0% was occupied by crystal grains having a grain size of less than 5 mm (crystal planes were random) and accounted for 80%. The crystal plane of the silicon part is the (110) plane.

Using this target, a film was formed under the same conditions as in Example 1, and the particles were measured. Table 1 shows the measurement results.

[0026]

Embodiment 3 The purity, area ratio, arrangement and size are the same as those in Embodiment 1, and the silicon part is a giant grain (the crystal plane is random).
Occupies 25%, and crystal grains having a grain size of less than 5 mm (crystal planes are random) occupy 75%, while also in the tungsten part, giant grains (random crystal faces) occupy 25% and a grain size of less than 5 mm. A tungsten-silicon based mosaic target in which crystal grains (crystal planes are random) occupy 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 the particles were measured. Table 1 shows the measurement results.

[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 changed to 1000 W, and the particles were measured. Table 1 shows the measurement results.

[0029]

Fifth Embodiment In a shape as shown in FIG.
Backing plate (4 in FIG. 2) using a 9% single crystal tungsten plate and a 99.999% purity single crystal titanium plate
Bonding was performed to produce a tungsten-titanium-based mosaic target having an area ratio of 2.10: 1.00 between the tungsten portion (1 in FIG. 2) and the titanium portion (3 in FIG. 2).

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

Input power: 700 W Film formation time: 8 minutes Ar pressure: 0.5 Pa Substrate: 6 inch φ Si wafer (100) surface After film formation, particles of 0.1 μm or more existing on the substrate are commercially available wafers.・ Measured with a dust inspection device. Table 2 shows the measurement results.

[0032]

Embodiment 6 The purity, area ratio, arrangement and size are the same as those of Embodiment 5. In the titanium portion, giant grains (crystal faces are random) occupy 20%, and crystal grains having a grain size of less than 5 mm (crystal faces are random). ) Occupies 80%, and a tungsten-titanium mosaic target made entirely of single-crystal tungsten was produced in the same manner as in Example 5. 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 the particles were measured. Table 2 shows the measurement results.

[0034]

Example 7 The purity, area ratio, arrangement and size of Example 5 are the same as those of Example 5, and the titanium portion has 25% of giant grains (random crystal faces) and a grain size of less than 5 mm (crystal faces are random). ) Occupies 75%, while also in the tungsten part, giant grains (random crystal faces) occupy 25%, and
A tungsten-titanium mosaic target in which crystal grains of less than mm (crystal planes were random) accounted for 75% 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 the particles were measured. Table 2 shows the measurement results.

[0036]

Example 8 Using the target of Example 5, a film was formed under the same conditions as in Example 5 except that the input power was 1200 W, and the particles were measured. Table 2 shows the measurement results.

[0037]

Comparative Example 1 The purity, area ratio, arrangement and size are the same as those in Example 1, and the silicon portion is a giant grain (the crystal plane is random).
Occupies 15%, and crystal grains having a grain size of less than 5 mm (crystal faces are random) occupy 85%. On the other hand, in the tungsten portion, giant grains (random crystal faces) occupy 15% and a grain size of less than 5 mm. A tungsten-silicon based mosaic target in which crystal grains (crystal planes are random) occupy 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 the particles were measured. Table 1 shows the measurement results.

[0039]

COMPARATIVE EXAMPLE 2 A tungsten-silicon based mosaic target made of polycrystalline tungsten and polycrystalline silicon having the same purity, area ratio, arrangement and size as that of Example 1 is used under the same conditions as in Example 1. A film was formed. This target does not contain single crystals or giant grains as defined in the present invention. After the film formation, the same particle measurement as in Example 1 was performed. Table 1 shows the measurement results.

[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 the particles were measured.
Table 1 shows the measurement results.

[0041]

[Comparative Example 4] A conventional product having a molar ratio of tungsten to silicon of 1: 2.75, a purity of 99.999%, and a relative density of 99%
Then, 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 the particles were measured. Table 1 shows the measurement results.

[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 the particles were measured. Table 1 shows the measurement results.

[0043]

Comparative Example 6 Purity, area ratio, arrangement and size were the same as those of Example 5. In the titanium portion, giant grains (crystal faces were random) accounted for 15%, and crystal grains having a grain size of less than 5 mm (crystal faces were random). ) Occupies 85%, while in the tungsten part, giant grains (crystal faces are random) occupy 15%, and the grain size is 5%.
A tungsten-titanium-based mosaic target in which crystal grains having a size of less than mm (crystal planes are random) occupy 85% 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 the particles were measured. Table 2 shows the measurement results.

[0045]

Comparative Example 7 A tungsten-titanium mosaic target made of polycrystalline tungsten and polycrystalline titanium and having the same purity, area ratio, arrangement and size as in Example 5 was used under the same conditions as in Example 5. A film was formed. This target does not contain single crystals or giant grains as defined in the present invention. After the film formation, the same particle measurement as in Example 5 was performed. Table 2 shows the measurement results.

[0046]

Comparative Example 8 Using the target of Comparative Example 7, a film was formed in the same manner as in Example 8, and the particles were measured. Table 2 shows the measurement results.

[0047]

Comparative Example 9 A conventional product having a molar ratio of tungsten to titanium of 2.34: 1.00, a purity of 99.999%, and a relative density of 9
Using a sintered tungsten-titanium target of the same size as in Example 5 at 9%, a film was formed under the same conditions as in Example 5, and the particles were measured. Table 2 shows the measurement results.

[0048]

Comparative Example 10 Using the target of Comparative Example 9, a film was formed in the same manner as in Example 8, and the particles were measured. Table 2 shows the measurement results.

Table 1 Single crystal / giant grain Input power Number of generated particles²⁾  Occupied area ratio ¹⁾ (%) (W) (%) Example 1 100 600 10 Example 2 82 600 15 Example 3 25 600 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 305Comparative Example 5 0 1000 513  1): Area ratio occupied by single crystals and giant grains on the sputtering surface of the target 2): Relative value to the result of Comparative Example 2 Table 2 Single crystal / giant grains Input power Number of generated particles²⁾  Occupied area ratio ¹⁾ (%) (W) (%) Example 5 100 700 8 Example 6 74 700 15 Example 7 25 700 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 285Comparative Example 10 0 1200 476  1): Area ratio occupied by single crystals and giant grains on the sputtering surface of the target 2): Relative value to the result of Comparative Example 7

[Brief description of the drawings]

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

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

[Explanation of symbols]

 1: Tungsten part 2: Silicon part 3: Titanium part 4: Backing plate of target

────────────────────────────────────────────────── ─── Continued on the front page Examiner Satoshi Sera (56) References JP-A-3-60119 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C23C 14/00- 14/58 H01L 21/285 H01L 21/285 301

Claims (5)

(57) [Claims] 1. A sputtering target formed by combining and integrating a plurality of target pieces having different compositions and mounting the same on a substrate.
Each target piece to be formed is composed of a single crystal, or
2, the proportion of big large target piece construction material, in a cross section parallel target strips to the sputtering surface
A sputtering target characterized by being one having an area ratio of 0% or more. 2. The target piece material is at least two members selected from the group consisting of refractory metals and silicon.
The sputtering target according to the above. 3. The sputtering target according to claim 2, wherein the refractory metal is tungsten, molybdenum, titanium, tantalum, or niobium. 4. The sputtering target according to claim 1, wherein the target piece material is silicon and tungsten. 5. The sputtering target according to claim 1, wherein the target piece material is tungsten and titanium.