JP3177208B2 - High purity titanium 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 made of high-purity titanium, and more particularly to a sputtering target having a different crystal orientation, a different crystal structure, and a different crystal grain size from those of the prior art, corresponding to future semiconductor devices. The present invention relates to a sputtering target made of high-purity titanium and having an improved film formation rate.

[0002]

2. Description of the Related Art A sputtering target is a generally disk-shaped plate which serves as a sputtering source for forming electrodes, gates, wirings, elements, insulating films, protective films and the like of various semiconductor devices on a substrate by sputtering. . When the accelerated particles collide with the target surface, the atoms constituting the target are released into space by the exchange of momentum and are deposited on the opposing substrate. As sputtering targets, Al and Al alloy targets, refractory metals and alloys (W, Mo, Ti, Ta, Zr, Nb, etc. and W
Alloys thereof) targets such as -ti, metal silicide _{(MoSi X, WSi x, NiSi} x , etc.) targets, etc. have been typically used.

One of the important targets among these targets is a Ti target for forming a Ti wiring, a Ti protective film and the like.

As the width of circuit wiring is reduced to 0.5 μm or less, the aspect ratio of through-holes and contact holes is increasing to 2 or more, and collimation sputtering is used as a technique for embedding underlying Ti or TiN in these holes. The law is drawing attention. The collimation sputtering method is a method of performing sputtering with a collimator interposed between a target and a substrate, such that only the sputtered atoms having a direction perpendicular to the substrate reach the substrate through the collimator. It was made. As a feature of the collimation sputtering method, while the conventional normal sputtering has a bottom coverage ratio of less than 10% when the aspect ratio of the hole is 2 or more,
By using the collimation sputtering method, a requirement of a bottom coverage rate of 10% or more required in the process may be achieved, but there is a problem that the film forming rate is reduced to about 1/5 as compared with the conventional sputtering method.

On the other hand, particles generated during film formation are regarded as a major problem as a cause of circuit disconnection and short circuit.
How to suppress the generation of particles with the miniaturization of the circuit wiring width is a key factor of the film forming process in increasing the LSI manufacturing yield. Particularly, in recent years, TiN formed by reactive sputtering in a nitrogen atmosphere of a Ti target has begun to be widely used as a barrier layer. However, since a TiN deposited layer film has a high film stress and is brittle, a sputtering chamber other than a wafer is used. The TiN film continuously and thickly deposited therein easily peels off, and is a main source of particles. As one of the particle generation sources in such a reactive sputtering process, Ti deposited in a layer or island shape in a relatively shallow or non-eroded region such as an outer peripheral portion or a central portion of a Ti target due to sputtering.
There is an N layer, and a sputtering apparatus, sputtering conditions, and the like have been improved and studied in order to suppress generation of particles from the TiN layer.

In recent years, as the size of a wafer is increased from 6 inches to 8 inches and the width of circuit wiring is reduced to 0.5 μm or less, the uniformity of a thin film formed on a wafer by sputtering is improved. It is being studied for the purpose.

[0007]

The problems of the film formation rate in the collimation sputtering method, the particle problem and the improvement of the film thickness distribution have been conventionally improved and studied mainly from the viewpoint of the sputtering apparatus and sputtering conditions. However, the fact is that the quality of the target itself has not been deeply considered. In general, it is generally known that the structure and crystal structure (crystal grain size, crystal orientation, and the like) of the surface and inside of a crystalline material greatly affect the emission characteristics of sputtered atoms from a target. From this, it is considered that also in the Ti target, the difference and the non-uniformity of the structure and the crystal structure greatly affect the emission characteristics of the sputtered atoms and the directional characteristics thereof.

For example, J. Vac. Sci. Technol. A Vol.
5, No4, Jul / Aug 1967, pages 1755-1768, published by C.I.Wickersham Jr., "Crystallographic target effects in magne.
"Tron sputtering" describes the effect of crystal orientation on the film thickness uniformity of a sputtering thin film. Much research has been done on aluminum targets instead of titanium. JP-A-63-31297
No. 5 is based on the fact that the thickness of the aluminum thin film formed on the wafer by sputtering has a distribution in which the central part is thick and the peripheral part is thin, so that the crystal orientation content ratio of the central part of the aluminum target is {220} / An aluminum sputtering target is described, wherein {200} is greater than that of the outer periphery. JP-A-2-1
No. 5167 describes an aluminum sputtering target in which at least 50% of the area of the target surface is composed of a (111) crystal plane. JP-A-3-2369 describes that
As the aluminum target was consumed by magnetron sputtering, a ring-shaped groove was formed on the surface along with the rotation of the magnet, and the emission direction of atoms changed. It is proposed that the ratio {100} / {110} be reduced as it enters the interior from the target surface. JP-A-3-10709 discloses that the crystal orientation content ratio {220} / {200} of the sputtered surface of an aluminum target is 0.1%.
A target characterized by five or more is described. Furthermore, Japanese Patent Application Laid-Open No. Hei 4-234170 discloses that an aluminum target having a particle size of 2 mm or less and a <110> fiber structure has a fiber axis having a X axis that is at least 20 times the randomness.
A target having a line diffraction intensity is described.

SUMMARY OF THE INVENTION It is an object of the present invention to reduce or solve the problem of the film forming speed in the collimation sputtering method in a Ti target in which the crystal orientation has not been considered, and also to reduce the particle problem. And a Ti target capable of improving the film thickness distribution.

[0010]

In order to solve this problem, the present inventor has proposed a method for improving the crystal orientation and the crystal structure and the crystal grain size which have not been considered in the conventional Ti target. As a result of examining the influence, (a) the following equation measured by the X-ray diffraction method on the sputtering surface of the target:

(Equation 3) Is based on the fact that the crystal orientation content ratio A at each part of the target calculated by the above is 80% or less, preferably 50% or less. In addition, (b) measured by the X-ray diffraction method on the sputtering surface of the target. And the following formula

(Equation 4) The crystal orientation content ratio B at each part of the target calculated by the above is 20% or less, (c) the target crystal structure is a recrystallized structure, and (d) the average crystal grain size at each part of the target is 500 μm or less, preferably 100
μm or less, and (e) that the average grain size of each site is adjusted to be within ± 20% of the average grain size of the entire target by averaging the average grain size of each site. It has been clarified that the above-mentioned problems that could not be achieved with the quality of the conventional Ti target can be reduced or solved by employing them alone or in combination of one or more.

Based on this finding, the present invention provides: (1) The crystal orientation content ratio A at each part of the target measured by the X-ray diffraction method on the sputtering surface of the target is 80%
(2) The high-purity titanium sputtering target according to (1), wherein the crystal orientation content ratio A at each site is 50% or less; And (4) the high-purity titanium sputtering target according to (1) or (2), wherein the crystal orientation content ratio B at each site is 20% or less, and (4) the target crystal structure is a recrystallized structure. (1) The high-purity titanium sputtering target of (1) to (3), and (5) the high-purity titanium sputtering target of (1) to (4), wherein the average crystal grain size at each portion of the target is 500 μm or less. Titanium sputtering target, (6) Variation of average crystal grain size of each part with respect to average crystal grain size of entire target is ± 20%
(1) to (5), wherein the high-purity titanium sputtering target of (1) to (5) and (7) the average crystal grain size at each part of the target is 100 μm or less. (6) A high-purity titanium sputtering target is provided.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS When plastic working is performed by forging, rolling or the like in a target titanium manufacturing process in pure titanium, the (002) plane is ± 35 with respect to the target sputtered surface as the working ratio increases. A texture having an inclination of within ° is formed. X-ray diffraction method (00
2) When evaluating the crystal orientation of a typical texture of titanium having a plane inclination of ± 35 ° or less, each diffraction peak corresponds to a crystal plane parallel to the target sputtering plane. , As shown in Table 1, (002)
A crystal plane having an interplanar angle of 35 ° or less from the plane, that is, 3
(103) plane inclined at 0 °, (014) plane inclined at 24 °,
The diffraction peak of the (015) plane inclined by 20 ° tends to increase with the texture, and these crystal planes also have a (00) plane.
2) It is necessary to consider in addition to the surface. Based on these facts, in the present invention, the crystal orientation content ratio A and the crystal orientation content B are defined. Regarding the measuring method, the measurement sample is obtained by chemically removing a deteriorated layer on the surface of the sample by electrolytic polishing or the like, and then measuring the intensity of diffraction lines corresponding to each crystal orientation with an X-ray diffractometer. The intensity value of the obtained diffraction line is corrected by the relative intensity ratio of the diffraction line of each crystal orientation (refer to JCPDS Card), and the crystal orientation content ratios A and B are calculated from the corrected intensity. Table 1 shows the method of calculating the crystal orientation content ratio.
Shown in

[0013]

[Table 1]

On the sputtering surface of the target, the crystal orientation content ratio A of each portion measured by the X-ray diffraction method is 80% or less. In addition, the crystal orientation content ratio B is preferably set to 20% or less. Here, the crystal orientation content ratio A of each site
Is 80% or less, and preferably, the crystal orientation content ratio B is 2%.
It is generally known that the sputtered atoms have a high probability of popping out in the direction of the densest atomic row when the target is strongly crystallized in the (002) plane. Since each crystal grain plane has a higher ratio of (002) planes and a dense atomic row direction in the (002) plane, which is the closest atomic plane,
This is because the probability of sputtered atoms jumping out parallel to the erosion surface is increased. As a result, the number of sputter atoms captured on the slope corresponding to the micro unevenness of the target erosion surface means that the higher the crystal orientation of the (002) plane, the higher the number of sputter atoms. The number of TiN layers deposited in layers or islands increases.
When the crystal orientation content ratio A of each part is 80% or more and when the crystal orientation content ratio B is 20% or more, this tendency becomes more remarkable.

The target crystal structure is a recrystallized structure,
The average crystal grain size at each portion of the target is 100 μm or less, and the variation of the average grain size of each portion with respect to the average crystal grain size of the entire target obtained by averaging the average crystal grain size of each portion is within ± 20%. Is preferred. Here, the definition of the recrystallized structure, in which the variation of the average grain size of each portion with respect to the average crystal grain size of the entire target is ± 20% or less, aims at uniformity of the film thickness distribution. Further, the average crystal grain size at each portion of the target is set to 100 μm or less because the micromorphology of the erosion surface of the target is generally composed of crystal grains corresponding to the crystal structure of the target. The microscopic irregularities on the surface increase. This means that the probability that atoms sputtered in parallel to the target erosion surface are trapped on the slope corresponding to the irregularities increases as the crystal grain size increases, and as a result, the outer periphery of the target and The number of TiN layers deposited in layers or islands at the center increases. When the average crystal grain size is 100 μm or more, this tendency becomes remarkable.

It is preferable that the crystal orientation content ratio A of each part measured by the X-ray diffraction method on the sputtering surface of the target is 50% or less, and the crystal orientation content ratio B is 20% or less. Here, the crystal orientation content ratio A of each part is 5
0% or less, and the crystal orientation content ratio B is specified to be 20% or less, similarly to the above, because the sputtered atoms generally have a high probability of popping out in the direction of the densest atomic row. By keeping the orientation low, each crystal grain plane constituting the target erosion plane can be set to (00
2) This is to reduce the probability that sputtered atoms fly out parallel to the erosion plane with respect to the crystal plane other than the plane, and increase the ratio of sputtered atoms that fly out perpendicular to the target erosion plane. As a result, the number of sputtered atoms captured by the collimator during the collimation sputtering is reduced, and the number of sputtered atoms passing through the collimator is increased, so that the deposition rate is increased and the bottom coverage ratio of holes is improved. The crystal orientation content ratio B of each part is 2
0% or more and the crystal orientation content ratio A is 50% or more,
The influence of (002) plane crystal orientation becomes remarkable.

The high-purity titanium used as the material of the sputtering target of the present invention means 4N or more titanium. The adjustment of the quality of the target of the present invention can be performed by combining the plastic working such as rolling or forging and the heat treatment, but the specific degree of the quality adjustment depends on the purity of the target material, the casting structure, and the plastic working. And cannot be generally defined depending on the heat treatment method and the like. However, if the target material and the casting structure, the method of plastic working and heat treatment, and the like are specified, it is possible to easily find the plastic and heat treatment conditions for obtaining the above-mentioned predetermined quality.

For example, in order to realize a condition that the crystal orientation content ratio A at each part of the target is 80% or less and the crystal orientation content ratio B is 20% or less, the working ratio is set to 1 in the above steps. It is necessary to uniformly perform warm working at a temperature of 0.5 or less, and then to perform uniform heat treatment on the entire target in the recrystallization temperature range of the material to complete recrystallization.

The crystal orientation content ratio A at each portion of the target is 50% or less, and the crystal orientation content ratio B is 2%.
In order to realize the condition of 0% or less, of the above steps, the working ratio is set to 0.8 or less, uniform warm working is performed, and thereafter, the entire target is subjected to uniform heat treatment in the recrystallization temperature range of the material. It is necessary to complete the crystallization.

For example, the average crystal grain size at each portion of the target is 500 μm or less, and the variation of the average grain size of each portion with respect to the average crystal grain size of the entire target obtained by averaging the average crystal grain size of each portion is ±. In order to achieve the condition of 20% or less, the Ti ingot is hot-worked at a temperature higher than the recrystallization temperature of the material to destroy the cast structure to make the grain size uniform, and to obtain the final uniform fine recrystallized structure. In order to impart a uniform heat treatment to a predetermined final shape at a temperature lower than the recrystallization temperature, a uniform heat treatment is applied to the entire target in the recrystallization temperature range of the material to complete the recrystallization. . Here, the recrystallization temperature of the material mainly depends on the purity of the material and the plastic working state before the heat treatment.

In order to realize both conditions of the average crystal grain size and the crystal orientation content ratio, a processing method that satisfies both of the above conditions may be adopted.

The measurement of the average grain size at each site is performed according to JIS.
-The cutting method described in H0501 was used.

[0023]

Next, examples and comparative examples will be presented.

Example 1 A high-purity titanium ingot was subjected to plastic working and heat treatment to produce targets A and B having a crystal structure and a crystal orientation shown in Table 2, respectively. Target shape is about 300m in diameter
m, a flat sputtering target having a thickness of about 6 mm, which was manufactured as follows. (A) Target A: Titanium ingot was hot-worked at 700 ° C., then hot-worked at 450 ° C. with a working ratio of 0.6, and a uniform heat treatment was applied to the entire target at 600 ° C. for 1 hour. . (B) Target B: Titanium ingot was hot worked at 700 ° C., then hot worked at 275 ° C. with a working ratio of 2.0, and the entire target was subjected to uniform heat treatment at 630 ° C. for 1 hour. .

Attached to a magnetron type sputtering apparatus,
Use collimation with an aspect ratio of 6 "
A film was formed on a wafer substrate. Table 3 shows the film formation rate ratio for each target when collimation is not used. As shown in Table 3, the target A having a low crystal orientation content ratio A has a higher film formation rate ratio than the target B having a high crystal orientation content ratio A.

[0026]

[Table 2]

[0027]

[Table 3]

Example 2 and Comparative Example 1 High-purity titanium ingots were subjected to plastic working and heat treatment to produce targets A, B and C having a crystal structure and a crystal orientation shown in Table 4, respectively. The target was a flat sputtering target having a diameter of about 300 mm and a thickness of about 6 mm. Target A, B
And C were manufactured as follows. (A) Target A: Titanium ingot was hot-worked at 700 ° C., then hot-worked at 400 ° C. with a working ratio of 1.1, and a uniform heat treatment was applied to the entire target at 600 ° C. for 1 hour. . (B) Target B: Titanium ingot was hot-worked at 700 ° C., then hot-worked at 400 ° C. with a working ratio of 1.1, and a uniform heat treatment was applied to the entire target at 700 ° C. for 2 hours. . (C) Target C: Titanium ingot is hot-worked at 700 ° C., then hot-worked at room temperature with a forging ratio of 1.8, and uniform heat treatment is performed at 700 ° C. for 2 hours over the entire target. gave.

A film was formed on a 6 ″ wafer substrate by being attached to a magnetron type sputtering apparatus. Table 5 shows the average number of particles per wafer when each target was subjected to wafer processing until the end life of the target. The number of particles on the wafer was measured using a particle counter to measure the number of particles having a thickness of 0.3 μm or more after forming a 0.1 μm TiN film. The target A having a fine particle diameter shows the lowest average particle number,
The average number of particles increased in the order of target B having a low crystal orientation content ratio A and a large crystal grain size, and target C having a high crystal orientation content ratio A and a large crystal grain size.

[0030]

[Table 4]

[0031]

[Table 5]

[0032]

【The invention's effect】

(1) Even when collimation sputtering, between targets, and when the same target is used, there is little variation in the deposition rate and its fluctuation, and stable and excellent deposition rate properties are exhibited.
As a result, the bottom coverage ratio and the use yield of the Ti target during film formation are improved. (2) During sputtering of a Ti target, variation in particle generation and its fluctuation are small even between targets and when the same target is used, and stable and excellent low particle properties are exhibited. Thereby, the defect rate of a circuit such as an LSI formed on the wafer is improved. (3) Variations and variations in film thickness distribution between targets and when the same target is used are stable, and excellent film thickness distribution uniformity is stably exhibited. Thereby, the defect rate of a circuit such as an LSI formed on the wafer is improved.

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-5-214520 (JP, A) JP-A-6-10107 (JP, A) JP-A-7-90560 (JP, A) (58) Field (Int. Cl. ⁷ , DB name) C23C 14/00-14/58

Claims (7)

(57) [Claims] 1. A crystal orientation content ratio A at each portion of a target measured by an X-ray diffraction method on a sputtering surface of a target and calculated based on the following equation 1 is 80% or less. High purity titanium sputtering target. (Equation 1) 2. The crystal orientation content ratio A at each site is 50
% Or less, the high-purity titanium sputtering target according to claim 1. 3. The crystal orientation content ratio B at each portion measured by the X-ray diffraction method on the sputtering surface of the target and calculated based on the following equation 2 is 20% or less. 1 or 2 high-purity titanium sputtering target. (Equation 2) 4. The high-purity titanium sputtering target according to claim 1, wherein the target crystal structure is a recrystallized structure. 5. The high-purity titanium sputtering target according to claim 1, wherein an average crystal grain size at each portion of the target is 500 μm or less. 6. The high-purity titanium sputtering target according to any one of claims 1 to 5, wherein the variation of the average crystal grain size of each part with respect to the average crystal grain size of the entire target is within ± 20%. . 7. The high-purity titanium sputtering target according to claim 1, wherein an average crystal grain size at each portion of the target is 100 μm or less.