JP5144576B2 - Titanium target for sputtering - Google Patents

Description

The present invention reduces the impurities contained in the titanium target for sputtering, and at the same time, does not generate cracks or cracks even during high power sputtering (high speed sputtering), stabilizes the sputtering characteristics, and generates particles during film formation. The present invention relates to a high-quality sputtering titanium target that can be effectively suppressed.
In addition, about the impurity concentration described in this specification, all are displayed by the mass% (mass%).

In recent years, various electronic devices have been born from dramatic progress in semiconductors, and further improvements in performance and new devices are being developed every day.
Under such circumstances, electronics and device equipment are becoming smaller and the degree of integration is increasing. Many thin films are formed in these many manufacturing processes, but titanium also forms many electronic device thin films such as titanium and its alloy film, titanium silicide film, or titanium nitride film because of its unique metallic properties. Has been used.
When forming such a thin film of titanium (including an alloy and a compound), it is necessary to pay attention to the fact that it itself requires extremely high purity.

  Thin films used in semiconductor devices, etc. are becoming thinner and shorter, and the distance between them is extremely small and the integration density is improved, so the substances constituting the thin film or impurities contained in the thin film This causes a problem of diffusion into adjacent thin films. As a result, the balance between the constituent materials of the self-membrane and the adjacent membrane is lost, and a serious problem arises that the function of the membrane that must originally be owned is reduced.

  In the manufacturing process of such a thin film, it may be heated to several hundred degrees, and the temperature rises even during use of an electronic device incorporating a semiconductor device. Such a temperature increase further increases the diffusion rate of the substance, and causes a serious problem in the deterioration of the function of the electronic device due to the diffusion. In general, the above-described titanium and its alloy film, titanium silicide film, titanium nitride film or the like can be formed by physical vapor deposition such as sputtering or vacuum vapor deposition. Of these, the sputtering method used most widely will be described.

This sputtering method is a method in which positive ions such as Ar + are physically collided with a target placed on a cathode, and metal atoms constituting the target are emitted with the collision energy. Nitride can be formed by using titanium or an alloy thereof (such as TiAl alloy) as a target and sputtering in a mixed gas atmosphere of argon gas and nitrogen.
When impurities are present in the titanium (including alloy / compound) target during the formation of the sputtering film, coarse particles floating in the sputtering chamber adhere to the substrate, causing the thin film circuit to be disconnected or short-circuited. The problem is that the amount of particles that cause objects increases and a uniform film cannot be formed.

For this reason, it is needless to say that transition metals, refractory metals, alkali metals, alkaline earth metals or other metals that are conventionally impurities must be reduced, but these elements should be reduced as much as possible. However, the present situation is that the above-mentioned particles are generated and no fundamental solution has been found.
In addition, the titanium thin film may be used as a pasting layer for preventing particle generation when forming a titanium nitride Ti—N film, but the film is hard and sufficient adhesive strength cannot be obtained. There is a problem that the particles are peeled off and do not serve as a pasting layer, causing particles to be generated.

  Furthermore, recently, in order to increase production efficiency, there is a demand for high-speed sputtering (high power sputtering). In this case, the target may be cracked or cracked, which is a factor that hinders stable sputtering. There was a problem. As prior art documents, the following Patent Document 1 and Patent Document 2 can be cited.

International Publication No. WO01 / 038598 Special table 2001-509548 gazette

  The present invention solves the above problems, particularly reduces impurities that cause particles and abnormal discharge phenomena, and at the same time, does not generate cracks or cracks even during high power sputtering (high speed sputtering), and has improved sputtering characteristics. An object of the present invention is to provide a high-quality titanium target for sputtering that can stabilize and effectively suppress generation of particles during film formation.

  The present invention is 1) a high-purity titanium target containing S: 3 to 10 mass ppm and Si: 0.5 to 3 mass ppm as additive components, excluding the additive component and gas component, A sputtering titanium target characterized by having a purity of 99.995% by mass or more is provided.

  The present invention further includes 2) the purity of the sputtering target excluding additive components and gas components is 99.999% by mass or more, and 3) the average crystal grain size of the target according to 1), wherein the target has an average crystal grain size of 20 μm or less. The titanium target for sputtering described in 1) or 2) above, wherein 4) the average crystal grain size of the target before sputtering is 20 μm or less, and the average crystal grain size after starting sputtering is The titanium target for sputtering according to any one of 1) to 3) above, which is 70 μm or less.

  The titanium target for sputtering suppresses particles and abnormal discharge phenomenon by reducing impurities in the target, and does not generate cracks or cracks even during high power sputtering (high speed sputtering), stabilizes the sputtering characteristics, It has an excellent effect that a quality film can be formed.

The titanium target for sputtering of the present invention is a high-purity titanium target having a purity of 99.995% by mass or more. Furthermore, it is preferably 99.999% by mass or more. Needless to say, the purity of the titanium target excludes added components and gas components.
In general, a large amount of gas components such as oxygen, nitrogen, and hydrogen are mixed in comparison with other impurity elements. Although it is desirable that the amount of these gas components to be mixed is small, the amount that is usually mixed is not particularly harmful in order to achieve the object of the present invention.

  In this invention, it is one of the big characteristics that S: 3-10 mass ppm and Si: 0.5-3 mass ppm are contained as an additional component. By adding S and Si, the average crystal grain size of the target can be reduced to 20 μm or less at the stage of target production.

  Moreover, although the target is heated to about 700 ° C. during sputtering, the addition of S and Si can also suppress the coarsening of the crystal grain size due to heating. That is, even when subjected to such high-temperature heat, the average crystal grain size is maintained at 70 μm or less, that is, after starting sputtering of the target, even if such heating is applied, the average crystal grain size of the target is reduced. It can be maintained at 70 μm or less.

  The heat during sputtering also affects the crystal plane orientation. However, the addition of S and Si described above has an effect of effectively suppressing this change in crystal plane orientation. A change in crystal plane orientation is undesirable because it affects film formation speed and film quality. Therefore, suppressing the change in crystal plane orientation has the effect of maintaining the film formation quality constant.

  Moreover, as shown in the Example mentioned later, although an intensity | strength does not change a lot, the increase in elongation is recognized. This can obtain a great effect of suppressing the occurrence of cracks and cracks in the target.

In this case, as described above, the crystal grain size of the target before the start of sputtering and the thermal effect after the disclosure of sputtering are affected by the slightly coarsened crystal grain size. There is no big change. On the other hand, it has a great feature that an increase in elongation is recognized.
The high strength of the target and the large elongation have the effect of suppressing the occurrence of cracks and cracks in the target. Moreover, this phenomenon has an effect of suppressing the generation of cracks and cracks in the target not only in the target before the start of sputtering, but also under the influence of a high temperature of 700 ° C. during sputtering.

As the sputtering progresses, the generation of particles gradually increases. Conventionally, there has been a tendency for the crystal grain size to become coarse. However, in the present invention, it is possible to limit the grain size to 70 μm or less even when the crystal grain size is increased as described above. It is effective for prevention.
In addition, since the crystal orientation is stable, stable sputtering characteristics can be obtained, which is effective in film formation uniformity.

  Furthermore, since the strength of the target is high and high elongation is exhibited even if it is affected by heat, the stress on the target surface is reduced against thermal stress and thermal fatigue due to warpage during sputtering or ON / OFF of the sputtering power. It is possible to effectively prevent cracking of the target.

The above effects can be achieved when the titanium target itself is highly pure, and both contain S: 3 to 10 mass ppm and Si: 0.5 to 3 mass ppm as additive components, These numerical ranges show the range in which the effectiveness of the present invention can be realized.
If it is less than the lower limit, the object of the present invention cannot be achieved, and if it exceeds the upper limit, the characteristics as a high-purity target will be impaired and an impurity will be formed.

In order to produce high purity titanium, a known molten salt electrolysis method can be used. The atmosphere is preferably an inert atmosphere. During electrolysis, the initial cathode current density is preferably set to 0.6 A / cm ² or less, which is a low current density. Furthermore, the electrolysis temperature is preferably 600 to 800 ° C.
The electrodeposited Ti thus obtained, the additive element S: 3 to 10 ppm by mass and Si: 0.5 to 3 ppm by mass were mixed and melted by EB (electron beam), and this was cooled and solidified to form an ingot. The billet is manufactured by performing hot plastic working such as hot forging or hot extrusion at 800 to 950 ° C. By these processes, the cast structure in which the ingot is uneven and coarse can be broken and uniformly refined.

The billet thus obtained is repeatedly subjected to cold plastic deformation, such as cold forging or cold extrusion, and imparts high strain to the billet, so that the target crystal structure is finally 20 μm or less. Make uniform microstructure.
Next, the billet is cut to produce a preform corresponding to the target volume. The preform is further subjected to cold plastic working such as cold forging or cold extrusion to give a high strain and to process a target having a disk shape or the like.
Further, the target having a processed structure in which high strain is stored is rapidly heated using a fluidized bed furnace or the like and heat-treated at 400 to 500 ° C. for a short time. As a result, a target having a fine recrystallized structure of 20 μm or less can be obtained.

  These manufacturing processes show an example of the method for obtaining the high-purity titanium target of the present invention, containing S: 3 to 10 mass ppm and Si: 0.5 to 3 mass ppm, with the balance being Titanium and unavoidable impurities, excluding additive components and gas components, are not particularly limited to the above production steps as long as a titanium target for sputtering having a target purity of 99.995% by mass or more can be obtained. It is not a thing.

  Next, examples of the present invention will be described. In addition, a present Example is an example to the last, and is not restrict | limited to this example. That is, all the aspects or modifications other than the Example included in the scope of the technical idea of the present invention are included.

(Example 1-5)
S + Si was added to Ti having a purity of 99.995% by mass as shown below.
(Example 1) S: 3 massppm, Si: 3 massppm,
(Example 2) S: 5 massppm, Si: 2 massppm
(Example 3) S: 7 massppm, Si: 1 massppm
(Example 4) S: 10 massppm, Si: 0.5 massppm

(Comparative Example 1-2)
S + Si was added to Ti having a purity of 99.995% by mass as shown below.
(Comparative example 1) 0.5 massppm of S (this does not satisfy the conditions of the present invention), Si of 2 massppm
(Comparative Example 2) S: 5 massppm, Si: 0.3 massppm (this does not satisfy the conditions of the present invention).

  Ti added with the elements shown in Example 1-5 and Comparative Example 1-2 was dissolved by an electron beam, and Ti ingots were prepared using the manufacturing conditions in the above paragraphs [0021] to [0022] as appropriate. This was processed into a target shape. This was heated to 550 ° C. and 700 ° C., and the growth of crystal grains was observed. Table 1 shows the results of the crystal grain size at the time of target preparation and the crystal grain size after heating. About Example 1-5 and Comparative Example 1-2, all had a fine crystal of 20 micrometers or less in the stage produced to the target.

In addition, since there is segregation of components at the top and bottom portions at the stage of manufacturing the Ti ingot of the present invention, component analysis was performed on Example 5. The results are shown in Tables 2 and 3. Table 2 shows the top part and Table 3 shows the bottom part.
In this case, although there is a difference from the additive component, both the top portion and the bottom portion are within the range of the additive component of the present invention. Needless to say, when a large gap occurs between the top part and the bottom part, it is possible to appropriately select a place to be obtained from the ingot (remove the incompatible range).

(Change in average crystal grain size of Example 1-5 and Comparative Example 1-2)
As shown in Table 1, Example 1-5 was slightly coarsened at the stage of heating to 550 ° C., but there was almost no change. Even when heated to 700 ° C., it was coarsened to a maximum of 50 μm, but no coarsening exceeding 70 μm was observed.
On the other hand, Comparative Example 1 had fine crystals of 20 μm or less when the target was produced, but it was coarsened to 30 μm when heated to 550 ° C. Further, when heated to 700 ° C., it was coarsened to 180 μm.
Further, Comparative Example 2 had a fine crystal of 20 μm or less at the time of preparing the target, but was coarsened to 23 μm when heated to 550 ° C. Further, when heated to 700 ° C., it coarsened to 110 μm.

  These targets were sputtered using an actual production machine, and the generation state of particles was observed. In Example 1-5, although the generation of particles slightly increased from the initial stage of sputtering to the integrated power amount of 400 kWh, the generation of particles was kept low and almost unchanged. That is, in Example 1-5, generation of particles could be effectively suppressed.

  On the other hand, in Comparative Example 1-2, when the occurrence of the same particles was observed, the particles were kept relatively low from the initial stage of sputtering to the integrated power amount of 150 kWh. Development was observed. Thereafter, the generation of particles rapidly increased up to 250 kWh, and sputtering became unstable.

Next, for each Example 1-5 and Comparative Example 1-2, the orientation of crystals appearing on the target was examined. The results are shown in Tables 4 and 5. Table 4 shows the Basal plane orientation ratio, and Table 5 shows the (002) plane orientation ratio.
The plane orientation ratio of Basal is calculated by the formula shown in Table 6, and the (002) orientation ratio is calculated by the formula shown in Table 7.

As shown in Table 4, the basal plane orientation ratio is about 70-76% in heating at 550 ° C. and about 69-79% in heating at 700 ° C. for Example 1-5 of the present application. Yes, it does not fluctuate greatly.
On the other hand, in Comparative Example 1, although it was in the range of 61% at the time of target production, it became 71% at 550 ° C. heating and greatly increased to 76% at 700 ° C. heating, and the Basal plane orientation The rate has increased.
Further, in Comparative Example 2, although it was in the range of 62% at the time of preparing the target, it became 72% at 550 ° C heating, greatly increased to 75% at 700 ° C heating, and the Basal plane orientation ratio increased. did.
As is clear from the above, it can be confirmed that the change in the Basal plane orientation ratio is smaller in the example than in the comparative example.

As shown in Table 5, the surface orientation ratio of (002) is in the range of 1-5% at 550 ° C. heating and 1-6% at 700 ° C. heating for Example 1-5 of the present application. It was in range and did not fluctuate greatly.
On the other hand, in Comparative Example 1, although it is in the range of 9% at the time of producing the target, it becomes 29% at 550 ° C. heating, and the plane orientation ratio of (002) is 65% at 700 ° C. heating. Increased significantly.
Further, in Comparative Example 2, even when the target was in the range of 5%, it became 18% at 550 ° C. heating, and the plane orientation ratio of (002) increased greatly to 45% at 700 ° C. heating. .
As is clear from the above, it was confirmed that there was little change in the (002) plane orientation rate in the example as compared with the comparative example.

Next, regarding the various Ti targets of Examples 1-5 and Comparative Example 1-2, the maximum yield stress and elongation when the average crystal grain size of the present invention is 7 to 10 μm, and the thermal effect of the present invention. Table 8 shows the maximum yield stress and elongation when subjected.
Moreover, about various Ti targets of the said Example 1-5 and Comparative Example 1-2, when the average crystal grain size of this invention is 50-60 micrometers, it received the maximum yield stress and elongation, and the thermal influence of this invention. Table 9 shows the maximum yield stress and elongation when

As shown in Table 8 and Table 9 above, the present invention has a high maximum yield stress, but does not vary greatly depending on the additive element. The same applies to Comparative Example 1-2.
However, as can be seen from Tables 8 and 9, the elongation was small in Comparative Example 1-2, while a significant improvement in elongation was observed in Example 1-4.
In particular, in the range of the particle size of 50 to 60 μm heated in the vicinity of 700 ° C., the change in the maximum yield stress is not significantly different between the example and the comparative example, but the elongation is 10% in the comparative example 1. In Comparative Example 2, it was 12%, whereas in Example 1-4, it was 16 to 18%, showing a great improvement. This has a great effect on the crack prevention of the target.

  From the above, as in the present invention, as an additive component, S: 3 to 10 mass ppm and Si: 0.5 to 3 mass ppm are contained, and the purity of the target is 99.995 mass excluding the additive component and the gas component. % Or more of the titanium target for sputtering can produce a great effect that there is no generation of cracks or cracks, and the generation of particles during film formation can be effectively suppressed.

Reduces particles and impurities that cause abnormal discharge, and at the same time eliminates cracks and cracks during high-power sputtering (high-speed sputtering), stabilizes sputtering characteristics, and effectively generates particles during film formation Therefore, it is possible to provide a high-quality sputtering target for sputtering, which is useful for forming a thin film such as an electronic device.

Claims (4)

  It is a high-purity titanium target, and contains S: 3 to 10 mass ppm and Si: 0.5 to 3 mass ppm as additive components, and the purity of the target is 99.995 mass% excluding the additive components and gas components. A sputtering titanium target characterized by the above.   The titanium target for sputtering according to claim 1, wherein the purity excluding the additive component and the gas component is 99.999 mass% or more.   3. The sputtering target according to claim 1, wherein an average crystal grain size of the target is 20 μm or less. The average crystal grain size of the target before performing sputtering is 20 µm or less, and the average crystal grain size after starting sputtering is 70 µm or less. Titanium target for sputtering.