JP2789547B2 - Titanium silicide target for sputtering and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a titanium silicide target for sputtering capable of greatly reducing the number of generated particles and a method of manufacturing the same. A film formed by a sputtering process using the titanium silicide target of the present invention is very useful as a film for a highly integrated LSI having a very small wiring width, and a new highly integrated (4 Mbit, 16 Mbit, 64
Used for semiconductor devices such as LSI and VLSI.

[0002]

2. Description of the Related Art Polysilicon has been conventionally used as an electrode or wiring of an LSI semiconductor device, but a signal propagation delay due to a resistor has become a problem with the high integration of the LSI semiconductor device. On the other hand, it is desired to use a material having a high melting point as an electrode in order to facilitate the formation of a wiring or the like by a self-alignment method. In these situations,
Metal silicide wirings and electrodes that have lower resistivity than polysilicon and are compatible with the silicon gate process are used. Examples of such metal silicide, tungsten silicide (WSi _x), molybdenum silicide (MoSi _x), tantalum silicide (TaSi _x),
Titanium silicide (TiSi _x), cobalt silicide (CoSi _x), which is a refractory metal silicide such as chromium silicide (CrSi _x). Such a metal silicide film is formed by sputtering a silicide target for sputtering. As the silicide target for sputtering, when the molar ratio x is 2 or less, a film silicide target having a silicon / metal molar ratio exceeding 2 is used because the film stress is high when the film is formed and the film is easily peeled. Often.
In particular, only titanium silicide targets having a silicon / titanium molar ratio of 2.40 or more have been used.

[0003] Among such metal silicides, titanium silicide is attracting attention as one of the materials particularly useful for highly integrated VLSI in the future.

Conventionally, as described above, a titanium silicide target having a silicon / titanium molar ratio of only 2.40 or more is used, and a silicon / titanium powder / silicon / titanium molar ratio of 2.40 is used. It is manufactured by pressing and sintering a synthetic silicide powder produced by mixing and synthesizing as described above, and machining it to a predetermined size.

[0005]

In recent years, the integration density of LSI semiconductor devices has increased (4 Mbits, 16 Mbits,
64M bits), and the wiring width is being miniaturized to 1 μm or less. In this case, generation of particles from the target is recognized as a serious problem. Particles refer to particles scattered from a target at the time of sputtering.These particles directly adhere to a film on a substrate, or adhere to a peripheral wall or a component and peel off after being deposited, and adhere to the film,
It causes serious problems such as disconnection and short circuit of wiring. The particle problem becomes more and more serious as the integration and miniaturization of electronic device circuits progress. As the use of titanium silicide targets having a molar ratio of 2.40 or more increases, such targets have a very high integration VLSI due to the very large number of particles generated during sputtering.
It became a problem again that it was unsuitable for the purpose of use.

Conventionally, it has been recognized that the generation of particles of the metal silicide target largely depends on the coarse silicon free phase. Based on such recognition, for example, Japanese Patent Application Laid-Open No. 4-191366 discloses that in a silicide target composed of a refractory metal and Si, the average particle size of free Si particles is 30 μm.
Hereinafter, and discloses a silicide target and a manufacturing method thereof wherein a surface and free Si grains or grain size 40μm in the cross section is 50 / mm ² or less. Japanese Patent Application Laid-Open No. 5-1370 according to the present applicant is characterized in that the amount of the coarse silicon phase of 10 μm or more appearing on the sputtered surface of the metal silicide target is 10 pcs / mm ² or less, with the regulations further strengthened. A metal silicide target and a method for manufacturing the same are disclosed.

The above two patent publications are directed to general metal silicides including titanium, but in each of the embodiments, only tungsten silicide is dealt with. Not. As awareness of the usefulness of titanium silicide targets has increased and its use has increased, it has been newly recognized that titanium silicide is still inadequate due to the large number of particles generated under the above regulations. It became so.

An object of the present invention is to establish a technique for manufacturing a titanium silicide target for sputtering in which the number of generated particles is extremely small.

[0009]

Means for Solving the Problems The present inventor has continued his research on solving the particle problem, particularly for a titanium silicide target. As a result, in the case of a titanium silicide target, the molar ratio of silicon / titanium is the same as that of the prior art. Above 2.40, it is inevitable that the generation of particles exceeding the allowable limit cannot be avoided, so that the molar ratio of silicon / titanium is set to 2.00 to 2.35, the existing ratio of the Si phase is reduced, It has been found that particles can be extremely reduced by further reducing the size, increasing the target density, and removing the affected layer on the surface. Even if the molar ratio of silicon / titanium is reduced to 2.00 to 2.35,
It was also confirmed that there was no problem in the performance of film formation.
It has been found that the number of generated particles is 7000 to 8000 / wafer when the conventional titanium silicide target is used, but it can be reduced to 50 to 60 / wafer by the present invention. This aspect of particle depletion is unique to titanium silicide targets and is not found in other types of refractory metal silicides.

Based on this finding, the present invention provides (1) a silicon / titanium molar ratio of 2.00 to 2.35, an area ratio of a silicon phase appearing on a sputtered surface of 23% or less, The amount of coarse silicon phase having a size of 10 μm or more appearing at 10 μm / mm ² or less and the density is 99%
And a titanium silicide target for sputtering, characterized in that the surface roughness layer is reduced to 1 μm or less, and (2) the maximum grain size 2
0 μm or less silicon powder and titanium powder or titanium hydride powder having a maximum particle size of 60 μm or less are mixed so that the molar ratio of silicon / titanium is in the range of 2.00 to 2.35;
In the case of titanium hydride powder, the obtained mixed powder is synthesized after or after dehydrogenation to produce a titanium silicide powder, and the titanium silicide powder is hot-pressed to have a density of 99% or more. A sintered body is produced, the sintered body is machined to a predetermined size, and a surface treatment for removing a post-processed deteriorated layer is performed to reduce the surface roughness to 1 μm or less. % Or less, and a method for producing a titanium silicide target for sputtering, characterized in that a target having an abundance of a coarse silicon phase of 10 μm or more appearing on a sputtering surface of 10 μm / mm ² or less is provided. .

[0011]

According to the present invention, in the titanium silicide target, the molar ratio of silicon / titanium is reduced from 2.40 or more in the past to 2.00 to 2.35 to control the total amount of the generation probability of free silicon. The area ratio of the silicon phase appearing in the above is reduced to 23% or less to reduce the existing ratio of the Si phase, and the existing amount of the coarse silicon phase of 10 μm or more appearing on the sputtering surface is reduced to 10 / mm ² or less, and the Si phase is refined. To reduce internal voids that are a source of particles by increasing the target density to 99% or more, and to remove the process-induced deterioration layer on the surface and reduce the surface roughness to 1 μm or less, thereby reducing initial particles that are frequently generated at the beginning of sputtering. As a result, the amount of generated particles is significantly reduced as compared with the related art.

The raw material silicon powder is prepared by mixing a raw material such as a semiconductor polysilicon chip with a ball mill, for example, from 12 to 28%.
Grind for an hour in an argon atmosphere. Conventionally, this was sieved and used as it is. According to the present invention, the pulverized silicon powder is further finely pulverized by a pulverizer for fine pulverization to remove coarse particles of 20 μm or more. As the pulverizer for fine pulverization, any commercially available pulverizer that has taken measures against contamination can be used. For example, the following commercially available products are available:-Ultra-fine pulverizer Ongmill (manufactured by Hosokawa Micron Corporation)・ Supersonic jet crusher type I and PJM type (manufactured by Nippon Pneumatic Industries Co., Ltd.) ・ Current jet (manufactured by Nisshin Engineering Co., Ltd.) ・ Single-track jet mill (manufactured by Seishin Enterprise Co., Ltd.) ・ New ultrafine crusher ( Counter jet mill (manufactured by Itoman Engineering Co., Ltd.) By this secondary pulverization, coarse particles of 10 μm or more, particularly 8 μm or more, are practically reduced to almost zero.

As the raw material titanium powder, for example, a titanium powder finely pulverized by a ball mill or other pulverizer or a titanium hydride powder is used. For example, titanium powder or titanium hydride powder having a maximum particle size of 60 μm or less, preferably 45 μm or less is used. When sputtering is performed using a target having a high oxygen content, the release of oxygen causes
Undesirably, cracks in the target, oxidation of the formed film, and variations in the film quality occur. The oxygen content of the target can be reduced by using titanium hydride (TiH ₂ ) powder as a titanium source and then dehydrogenating it. Titanium hydride is also advantageous in that it can be easily ground.

As the raw material of titanium powder and silicon powder, it is preferable to use those in which the contents of radioactive elements, alkali metals, transition elements, heavy metals, oxygen and the like have been reduced to very small amounts. Such raw silicon powders having a purity of 5-9N (99.999-99.9999999wt%) or more are easily commercially available. As for the raw material titanium powder, titanium is generally produced by the Kroll method. Titanium produced by the same method has relatively few radioactive elements, but heavy metals such as iron have contamination from the reaction vessel of about 100 ppm, and oxygen is titanium. Since it has a strong affinity with, a few thousand ppm is contained.
Therefore, it is recommended to use a highly purified iodide obtained by a thermal decomposition method, a molten salt electrolysis method or the like.

Such titanium and silicon raw material powders are
Mixing is performed by a V-type mixer or the like at a predetermined ratio corresponding to a target titanium silicide within a range of i / Ti = 2.00 to 2.35. It is customary to increase the amount of silicon slightly in anticipation of silicon volatiles in the subsequent synthesis process. Such silicon volatiles can be accurately grasped in the equipment and conditions used, and it is desirable to minimize the silicon excess. These mixed powders undergo synthesis processing in a high-temperature vacuum furnace. Titanium hydride powder (Ti
When H ₂ ) is used, the dehydrogenation treatment and the synthesis treatment are performed together. Usually, after dehydrogenation, synthesis is performed by increasing the temperature. However, synthesis can be performed while dehydrogenation is performed. The synthesis reaction is exothermic. Silicide synthesis conditions are as follows: vacuum: 10 ^-3 to 10 ^-5 Torr Temperature: 800 to 1,150 ° C. _{Time: Ti + xSi → TiSi x (} x = 2.00~2.
Time sufficient for the synthesis reaction according to 35)

The silicide after the synthesis is cooled in a vacuum, cooled to 50 ° C. or lower, and then taken out of the furnace. Next, the synthetic silicide is pulverized by a ball mill, a vibration mill or another pulverizer, and classified to obtain a synthetic silicide powder. In order to prevent an increase in the amount of O ₂ during pulverization by a ball mill, it is necessary to take measures such as carrying out in an Ar substitution atmosphere. It is preferable to use titanium lining spheres, titanium spheres and the like for the purpose of preventing contamination of Fe and the like. The synthetic silicide powder is preferably 50 mesh or less, more preferably 20 mesh or less.
It is beneficial to sieve through a dry sieve to 0 mesh or less to make the particle size uniform.

When the molar ratio needs to be adjusted, a silicide powder having a molar ratio different from that of the raw silicide containing no coarse silicon is added as needed. The added silicide powder is also -50 mesh, preferably -20 mesh.
A mesh of 0 mesh is used. The raw material silicide powder and the added silicide powder are sufficiently mixed using, for example, a V-type mixer. Performing the composition adjustment using the silicide powder before hot pressing helps to prevent the generation of particles due to the agglomerated silicon. Particles incorporated in the agglomerated silicon also participate in the generation of particles. Therefore, the generation of particles is suppressed by adding the silicide powder to the composition ratio adjustment before hot pressing without adding the silicon powder which is likely to be agglomerated.

Thereafter, hot pressing is performed. It is important to carry out hot pressing so as to achieve a sufficiently high density of the silicide powder. In hot pressing, it is preferable to apply a preload and hold after pressing. The hot pressing conditions are as follows: Degree of vacuum: 10 ^-5 to 10 ^-6 Torr Temperature: 1000 to 1320 ° C. Press pressure: 250 to 600 kg · cm ² hours: 30 minutes to 3 hours Hold time: Longer is better 30 minutes minimum Hot press inserts the titanium silicide powder, starts heating, and when it reaches the target temperature of 1000 to 1320 ° C, starts applying a predetermined press pressure while maintaining that temperature level I do. The material is progressively reduced in thickness by the application of the pressing pressure, beyond a certain point the material thickness reaches a certain value and is not reduced further. In this state, the application of the press pressure is generally released, but in order to further increase the density, it is effective to apply a preload at the time of pressing and hold the state for 30 minutes or more after the above point. is there. This is called a hold here. Thus, a high-density sintered body having a density of 99% or more is obtained.

By pressing the fine synthetic silicide powder as a raw material at a high temperature for a sufficient time, the sintering between grains proceeds, and a uniform sintered structure is generated. In this case, the hot pressing is a solid phase sintering. Many conventional methods generate a liquid phase during sintering, which has been found to be prone to particle generation. Therefore, in the present invention, solid-phase sintering is performed under the above conditions.

After pressing, the pressed product is taken out and finished into a sputtering target of a predetermined size by machining. Thereafter, in the present invention, the affected layer is removed,
At the same time, a process-affected layer removing step for performing surface smoothing is incorporated. The process-affected layer removal step is performed by an appropriate surface treatment such as lapping, chemical etching, electrolytic polishing, and pre-sputtering. Thereafter, ultrasonic cleaning and vacuum drying are performed to obtain a product. Finally, the obtained target is bonded to a backing plate.
By this surface treatment, the surface roughness (R _a ) of about 5.0 μm before the treatment is reduced to 1.0 μm or less. It has been found that this process-altered layer removal step is very effective in suppressing the generation of initial particles. At the beginning of sputtering, a large amount of particles are generated, and they adhere to, for example, the inner wall of the apparatus and peel off and adhere to the coating. By suppressing the initially generated particles, the total number of particles adhering to the wafer can be significantly reduced.

Thus, the area ratio of the silicon phase appearing on the sputter surface is 23% or less,
The existence amount of coarse silicon phase of 0 μm or more is 10 / mm ²
Or less, a density of 99% or more, and a titanium silicide target having a silicon / titanium molar ratio of 2.00 to 2.35 having a surface roughness of 1 μm or less by removing a work-affected layer on the surface. Is achieved. The silicon / titanium molar ratio is increased from the conventional 2.40 or more to 2.00 to 2.35.
The total amount of free silicon is regulated by reducing the amount of free silicon, and at the same time, the area ratio of the silicon phase appearing on the sputtered surface is reduced to 23% or less through the control of the particle size of the raw material powder and the management of the synthesis and sintering processes. Appear 10
The abundance of the coarse silicon phase of not less than 10 μm is set to 10 or less / mm ² , the target density is set to not less than 99%, the internal voids are reduced, and the deteriorated layer on the surface is removed.
By setting the diameter to μm or less, these effects are combined, and the amount of generated particles has been significantly reduced as compared with the conventional case. It has been confirmed through many experiments that the area ratio of the silicon phase should be set to 23% or less and the amount of the coarse silicon phase having a size of 10 μm or more appearing on the sputtered surface should be set to 10 / mm ² or less through many experiments. The generation of particles can be drastically reduced with high reliability in combination with other requirements by reducing the existence ratio and making the miniaturization more strict.

Incidentally, the area ratio of the silicon phase appearing on the sputtered surface and the abundance of the coarse silicon phase of 10 μm or more are as follows:
This was performed by magnifying 100 times with a microscope, and visually measuring and counting.

[0023]

EXAMPLES Examples and comparative examples will be described below.

(Example 1) Si powder pulverized by a ball mill for 14 hours was sieved with a 200-mesh sieve.
i powder is further pulverized by a counter jet mill to obtain a Si powder having a maximum particle size of 8 μm and a T powder having a maximum particle size of 45 μm.
The iH ₂ powder was mixed with Si / Ti = 2.15, dehydrogenated at a temperature of 600 ° C, and synthesized at a temperature of 1000 ° C to obtain a titanium silicide powder. This titanium silicide powder was hot-pressed at 1200 ° C. and subjected to machining, surface treatment, and bonding to form a sputtering target. The characteristics of this target were as follows: Si / Ti = 2.13, S appeared on the sputtered surface
i-phase area ratio = 13.4%, 10 μm appearing on sputtered surface
The number of Si phases of m or more = 0 pieces / mm ² , density = 99.8%
And the surface roughness R _a = 0.6 μm. A titanium silicide film was formed by sputtering using this target, and particles on the wafer were measured by a laser method. There were only 5 particles of 0.5 μm or more on a 6-inch wafer.

Example 2 TiH was used as a titanium raw material powder.
_A target was produced in exactly the same manner as in Example 1 except that Ti powder (maximum particle size: 45 μm) was used instead of the _two powders. Exactly the same results as in Example 1 were obtained.

Comparative Example 1 A Si powder having a maximum particle size of 8 μm and a Ti powder having a maximum particle size of 45 μm were mixed so that Si / Ti = 2.65, which contains more Si than specified in the present invention. Synthesis was performed in the same manner as in Example 2 to obtain a titanium silicide powder. This titanium silicide powder was hot-pressed, subjected to machining, surface treatment, and bonding to finally form a sputtering target of TiSi _2.60 . The area ratio of the Si phase appearing on the sputtered surface of the TiSi _2.60 target = 30.0%, 10% appearing on the sputtered surface.
Number of Si phases having a size of μm or more = 0 pieces / mm ² , density = 99.9
% And surface roughness R _a = 0.6 μm. A titanium silicide film was formed by sputtering using this target, and particles on the wafer were measured by a laser method. The number of particles having a size of 0.5 μm or more was 150 on a 6-inch wafer. Since Si / Ti = 2.65 containing more Si than the range specified by the present invention, the area ratio of the Si phase appearing on the sputtered surface was increased to 30.0%, and the amount of particles increased.

(Comparative Example 2) A Si / Ti = 2.13 sputtering target was finally manufactured in the same manner using Si powder containing large particles having a maximum particle size of 45 μm and Ti powder having a maximum particle size of 45 μm. . Area ratio of Si phase appearing on the sputtering surface of this TiSi _2.13 target = 13.4
%, The number of Si phases of 10 μm or more (maximum Si phase size: 45 μm) appearing on the sputtered surface = 40 / mm ² , density = 9
It was 9.8% and the surface roughness _Ra = 0.6 μm. A titanium silicide film was formed by sputtering using this target, and particles on the wafer were measured by a laser method. The number of particles having a size of 0.5 μm or more was 500 on a 6-inch wafer. Since the Si powder having a large maximum particle size was used, the size of the Si phase became large and the amount of particles increased.

Comparative Example 3 TiS was prepared in the same manner as in Example 1.
i Titanium silicide target of _2.13 was produced, but the final product was obtained without removing the affected layer. At this time, the target surface roughness was 5 μm. When this target was used, there were 500 particles of 0.5 μm or more on a 6-inch wafer. The importance of the process of removing the affected layer is understood.

[0029]

According to the present invention, the particle problem of titanium silicide is practically solved, and the molar ratio of silicon / titanium is set to 2.0.
It is reduced to 0 to 2.35 to generate particles through the area ratio of the silicon phase appearing on the sputtered surface, the abundance of the coarse silicon phase of 10 μm or more appearing on the sputtered surface, the target density, and the removal of the work-affected layer on the surface. We succeeded in significantly reducing the volume. Titanium silicide, which is highly expected in the future as a film for a highly integrated LSI with a small wiring width, will be highly integrated (4 Mbit, 16 Mbit,
(4 Mbit, etc.) It contributes to practical use in semiconductor devices such as LSI and VLSI.

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Yasuhiro Yamakoshi 187-4 Usuba, Hachikawa-cho, Kitaibaraki-shi, Ibaraki, Japan Nikko Kyoishi Isohara Plant (56) References JP-A-5-1370 (JP, A) JP-A-3-130360 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C23C 14/34

Claims (2)

(57) [Claims] 1. The method according to claim 1, wherein the molar ratio of silicon / titanium is between 2.00 and
2.35, the area ratio of the silicon phase appearing on the sputter surface is 23% or less, and 10 μm appearing on the sputter surface.
The sputtering characterized in that the abundance of the above coarse silicon phase is not more than 10 / mm ² , the density is not less than 99%, and the work-affected layer on the surface is removed to reduce the surface roughness to 1 μm or less. For titanium silicide target. 2. A silicon powder having a maximum particle diameter of 20 μm or less and a titanium powder or a titanium hydride powder having a maximum particle diameter of 60 μm or less having a silicon / titanium molar ratio of 2.00 to 2.35.
In the case of titanium hydride powder, the obtained mixed powder is synthesized after or while performing dehydrogenation, and is synthesized to produce a titanium silicide powder, and the titanium silicide powder is hot-pressed. Then, a sintered body having a density of 99% or more is produced, the sintered body is machined to a predetermined size, and a surface treatment for removing a post-process deteriorated layer is performed to reduce the surface roughness to 1 μm or less. The area ratio of the appearing silicon phase is 23% or less and 10% appears on the sputter surface.
A method for producing a titanium silicide target for sputtering, wherein a target having an amount of a coarse silicon phase having a size of not less than 10 μm is not more than 10 / mm ² .