JPS63307267A - Sputtering target and its production - Google Patents

Abstract

PURPOSE:To manufacture a sputtering target forming a film with uniform composition ratio, by compacting compound material into a disklike state and changing the composition ratio of this compound material in a direction from the outside of the disk toward the center. CONSTITUTION:The inside of a vessel 11 made of carbon resin is divided with partition plates 16 into concentrically annular parts 12, 13, 14 and a concentrically circular part 15 respectively different in the composition ratio between high-m. p. metal (Mo, etc.) and silicon. Further, the parts 12, 13, 14, and 15 are filled with powdered MoSi2.2, powdered MoSi2.3, powdered MoSi2.4, and powdered MoSi2.5, respectively. Subsequently, the above-mentioned powders are slightly compacted from above and the partition plates 16 are pulled out, and all the powders are heated and compacted in a vacuum of about 10<-2>Torr at a pressure of about 100kg/cm<2>, which is surface-treated and annealed in a hydrogen atmosphere. Further, the above compact is worked into prescribed dimensions, washed, and dried so as to be formed into the desired target. By using this target, a film having uniform composition ratio can be formed on a substrate.

Description

Detailed Description of the Invention [Object of the Invention] (Industrial Application Field) The present invention relates to a sputtering target used for forming a high melting point metal silicide film used as a gate electrode or wiring of a VLSI, and its manufacture. It is about the method.

(Prior art) Recently, silicides of high-melting point metals such as molybdenum and tungsten have been widely used as gate electrode and wiring materials for MO8 semiconductor devices, replacing the conventionally commonly used aluminum and conventionally common polysilicon. has been done.

Various methods have been developed as techniques for forming films mainly made of metal materials, and sputtering is a typical method. Sputtering is a technology in which positive ions in plasma are accelerated and collided with a target, and the ejected material is deposited on a wafer.
The first method is DC sputtering, in which a direct current electric field is applied to the target by an electromagnet, and positive ions are generated by glow discharge. This method is suitable for sputtering metallic materials.

The second method is RF sputtering, which is a method in which a high-frequency electric field is applied to a gas and the resulting electric field causes ions to collide, and is suitable for forming insulating material films such as 5102 and A205.

The third type is DC magnetron sputtering, which performs sputtering by placing the deposited material on the cathode of a magnetron, and is suitable for sputtering metal materials such as aluminum and high-melting point metal silicides such as Mo512 with high productivity. There is.

The fourth type is chemical sputtering, which uses a mixture of commonly used argon gas and O gas or N2 gas.The former uses, for example, a tank target to form a Ta2O film, and the latter uses a titanium target. Then, a TiN film is obtained.

The fifth method is bias sputtering, in which a positive or negative DC or high frequency bias is applied to the substrate on which a film is deposited by sputtering.

FIG. 9 shows a target used for such sputtering. This is a so-called bonding type target, in which a target 2 is placed on a backing plate 1 made of copper, and is fixed with a bonding material 3 such as an indium-based adhesive. Note that this backing plate 1 is fixed on a cathode assembly (not shown) that includes an electromagnet that provides a necessary magnetic field to the target and a cooling section that cools the electromagnet.

Such a bonding type target is usually used for a high melting point metal silicide film. For example, in the formation of a molybdenum silicide (MoSi) film, silicon is used to improve thermal stability and crack resistance, and to reduce stress, which is slightly higher than the stoichiometric composition x = 2 (MoSi2). The proportion of x = 2. 5 (M
Molybdenum silicide having a composition ratio of 0 812.5) is used as a target. As shown in FIG. 10, the composition ratio distribution of this target is in the range of x-2.5±0.03 over the entire surface of the target, indicating high uniformity.

Figure 11 shows that such a target is attached to a single-wafer type DC magnetron sputtering device, the atmosphere inside the device is filled with argon at a pressure of 4 x 10'pa, and sputtering is performed continuously at a sputtering power of 1.5 KW. This figure shows the sheet resistance distribution within the wafer when a film is deposited to a thickness of 3000 nm on the silicon oxide film formed above and then annealed at 900°C to 950°C. As can be seen from the figure, the film thickness is 3000±15
Although the sheet resistance is almost uniform at 0.8, the sheet resistance is significantly large at the outer periphery of the wafer.

The cause of this phenomenon is explained as being due to the difference in the emission angle distribution of sputtered particles. Figure 12 is a distribution diagram of the release angle of sputtered silicon particles by argon ions;
The figure is a distribution diagram of the release angle of molybdenum sputtered particles due to mercury ions.The release angle distribution of molybdenum sputtered particles 9 is wider from side to side than that of silicon sputtered particles, so the deposition rate of molybdenum sputtered particles is lower at the periphery of the wafer. It is thought that the sheet resistance becomes lower than that of the silicon sputtered particles and becomes rich in silicon, which increases the sheet resistance. Such an increase in sheet resistance causes a decrease in the manufacturing yield of semiconductor devices and a decrease in device performance.

Deterioration in device performance due to such non-uniform compositional ratios occurs not only in high melting point metal silicides but also in aluminum alloys, insulators, and the like.

For example, in aluminum alloys such as Al5L and Al5iCu, when the silicon content increases, silicon precipitates and reduces reliability, while when the silicon content decreases, penetration of the diffusion layer, which is the active region of the device, occurs, which affects the device performance. This is a fatal flaw.

Furthermore, in the case of insulators such as Ta205 and HfO2, variations in composition ratio cause the insulation properties to deteriorate and leakage current to increase.

(Problems to be Solved by the Invention) As described above, conventional sputtering targets have a problem in that the composition ratio of the film formed by sputtering is not uniform, which adversely affects device performance.

The present invention was made in order to solve such problems, and an object of the present invention is to provide a sputtering target and a method for manufacturing the same that can obtain a film having a uniform composition ratio.

[Structure of the invention]

(Means for solving the problem) According to the sputtering target according to the present invention,
A sputtering method in which a compound material is molded into a disk shape and placed on a substrate is characterized in that the composition ratio of the compound material in the target changes from the outside to the center of the disk.

Further, according to the method for manufacturing a sputtering target according to the present invention, there is a step of concentrically arranging cylindrical partition plates according to a desired number of divisions in a molded container, and a step of arranging cylindrical partition plates concentrically in a molded container according to a desired number of divisions, and increasing the distance between each partition plate toward the center. It includes the steps of filling different powders with a high proportion of silicon, removing the partition plate, and performing compression and sintering.

(Function) According to the sputtering target according to the present invention,
Since the composition ratio of the compound material changes from the outside to the center of the disk, the film formed by sputtering has a uniform composition ratio. This makes it possible to obtain uniform performance across the wafer.

According to the method for manufacturing a sputtering target according to the present invention, a compound material whose composition ratio has been adjusted in advance can be placed at a predetermined position, so that a desired sputtering Φ target can be reliably obtained.

(Example) The sputtering target according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 and FIG. 2 show the sputtering process according to the present invention.
It shows a target and its manufacturing method, and the first
The figure is a plan view, and FIG. 2 is a central sectional view thereof.

According to these, a disc-shaped sputtering target is placed in a container 11 made of carbon resin, with concentric annular parts 12 and 1 having different composition ratios of high melting point metal and silicon, respectively.
3.14 and a central disk-shaped portion 15 are formed, which are separated by a partition plate 16.

The outermost portion 12 has a composition ratio of silicon and molybdenum
-,2,2 powder (MoS12.
2) is filled. This mixing is performed by mixing high-purity molybdenum silicide powder and high-purity silicon powder, or high-purity molybdenum and silicon powder in the above ratio.

Similarly, part 13 contains powder of M o S l 2,s, part 14 contains powder of M o S 12,4,
Portions 15 are each filled with powder of M o S l 2 , 5. In this case, the target value of the composition ratio of the film actually formed is M o S l 2,s. After filling each portion with powder, the powder is lightly compressed from above, and then the partition plate 16 is removed.

After that, 10'To
The whole is heated and compressed under a vacuum of about 100 kg/ci, sandblasted to perform surface treatment, and then annealed in a hydrogen atmosphere.

Subsequently, the sputtering target of the present invention is completed by processing to predetermined dimensions, washing and drying.

Figure 3 shows the sputtering process shown in Figures 1 and 2.
This is a graph showing the distribution of the composition ratio in the target, and it can be seen that the composition ratio is 2.5 in the center and decreases stepwise toward the periphery.

Figures 4 to 7 show the sputtering process according to the present invention.
This shows the configuration of the target, and Figures 4 and 6
The figure is a plan view, and FIGS. 5 and 7 are central sectional views thereof. In these cases, a sputtering target is constructed by a combination of an annular portion and a disk-shaped portion.

First, in FIGS. 4 and 5, the composition ratio X of silicon and molybdenum is 2.5 (M o Si2
．． 5), an annular portion 22 having a composition ratio of 2.2 is fitted around the disk-shaped portion 23, and is fixed onto the backing plate 21 by a bonding hole 24. Each of these parts is formed into a predetermined shape by machining from a sintered material.

The embodiments shown in FIGS. 6 and 7 have a similar configuration, but in this embodiment, the sputtering target has a disc-shaped part 12 with a composition ratio of 2.5 and a part 33 with a composition ratio of 2.5. It consists of three parts: an annular part 32 with a composition ratio of 3, and an annular part 31 with a composition ratio of 2.1.

FIG. 8 shows the results of sputtering using the sputtering target in the second example.

That is, the sputtering target of the example was attached to a single-wafer type DC magnet 6-sputtering device, and the atmosphere inside the device was filled with argon at a pressure of 4 x 10'pa, and silicon was formed on a wafer with a sputtering power of 1.5 KW. A 3,000-layer molybdenum silicide film was deposited on the oxide film, and then annealed at a temperature of 950° C., and the sheet resistance distribution was measured. According to the figure, a highly uniform sheet resistance distribution was obtained over the entire surface of the wafer.

In the examples, molybdenum is used as a high melting point metal and molybdenum silicide is exemplified as a compound, but examples include tungsten, titanium, tantalum, hafnium, zirconium, vanadium, niobium, rhenium, osmium, Compounds of other refractory metals such as palladium, platinum, etc. can be used.

Furthermore, even in targets that use aluminum alloys such as AlSi, Al5iCu, or insulators such as T a OHf O2, the characteristics can be made uniform over the entire wafer surface by changing the composition ratio according to the present invention. can.

Note that the value of the composition ratio and the size of each part can be adjusted as appropriate depending on the type of compound and gas used, sputtering conditions, etc.

〔Effect of the invention〕

As described above, according to the sputtering target according to the present invention, since the composition ratio of the compounds constituting the sputtering target changes from the periphery toward the center, sputtered atoms are released during sputtering. Uniform characteristics within the sputtered substrate can be obtained without being affected by the angle.

In addition, according to the method for manufacturing a sputtering target according to the present invention, a sputtering target having the following properties:
Targets can be manufactured stably and easily.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing one embodiment of a sputtering target according to the present invention, FIG. 2 is a central sectional view thereof, and FIG.
The figure is a graph showing the composition ratio distribution of a film obtained when sputtering is performed using the sputtering target of the present invention. 5 and 7 are cross-sectional views thereof, FIG. 8 is a graph showing the sheet resistance distribution of a film obtained when sputtering is performed using the sputtering target of the present invention, and FIG. 9 is a graph showing the sheet resistance distribution of a film obtained by sputtering using the sputtering target of the present invention. A perspective view showing the target, FIG. 10 is a graph showing the composition ratio distribution within the target, FIG. 11 is a graph showing the sheet resistance distribution obtained by sputtering using a conventional sputtering target, FIGS. FIG. 13 is an explanatory diagram showing the emission angle distribution of atoms during sputtering. 1.21...Backing plate, 12,13゜14
．． 15.22,23. '31.32.33... Compound material, 16... Partition plate. Applicant's agent Mr. Sato × Figure 4 Figure 5

Claims (1)

[Claims] 1. In a sputtering target formed by molding a compound material into a disc shape and placing it on a substrate, the composition ratio of the compound material changes from the outside toward the center of the disc. A sputtering target characterized by the following: 2. The sputtering target according to claim 1, wherein the compound is a high melting point metal silicide. 3. Claim 2 in which the high melting point metal is molybdenum
Sputtering target as described in section. 4. The sputtering target according to claim 2, wherein the high melting point metal is tungsten. 5. The sputtering target according to claim 1, wherein the compound is an aluminum alloy. 6. The sputtering target according to claim 1, wherein the compound is a metal oxide. 7. The sputtering target according to claim 2, wherein the composition ratio is varied so that the proportion of silicon increases from the outside to the center of the disk. 8. A high melting point metal silicide material serves as a target piece that divides the disk, and this target piece consists of a disk-shaped center piece with the highest proportion of silicon and 1 arranged around it.
8. A sputtering target as claimed in claim 7, wherein the sputtering target is two or more concentric annular pieces. 9. The sputtering target according to claim 7, wherein the high melting point metal silicide material is integrally molded so as to have a composition ratio gradient. 10. A step of concentrically arranging cylindrical partition plates according to the desired number of divisions in a molded container, a step of filling between each partition plate with different powders having higher silicon percentages toward the center, and the partitions. A method for manufacturing a sputtering target, comprising a step of extracting a plate, and a step of compressing and sintering.