JP2948073B2 - 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 non-conventional crystal such as an average crystal grain size and / or crystal orientation corresponding to future semiconductor devices. The present invention relates to a sputtering target made of high-purity titanium having characteristics.

[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 the sputtering target, A1 and A1 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.

In recent years, as the wafer size has increased from 6 inches to 8 inches and the width of circuit wiring has been reduced to 0.5 μm or less, the uniformity of the thin film formed on the wafer by sputtering has been reduced. From the standard that the standard deviation (σ) of the variation in the thickness distribution is 5% or less, the triple value (3σ) of the standard deviation is 5% or less, which is a standard required for securing the characteristics of the formed fine wiring. Is getting tougher. Against this background, sputter apparatuses, sputtering conditions, targets, and the like have been studied for the purpose of improving the uniformity of the film thickness. Even when the target is used, the variation in the film thickness distribution and its fluctuation are large, and the above-mentioned standard (3σ <5) regarding the film thickness distribution is used.
%) Is not satisfied.

[0005]

The above-mentioned problem of the standard concerning the film thickness distribution has been conventionally improved and examined mainly from the viewpoint of the sputtering apparatus, sputtering conditions and the like. The fact is that quality was not considered in depth. 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, in J. Vac. Sci. Tech
nol. A Vo15, No4, Jul / Aug196
7, pp. 1755-1768.
A paper by Wickersham Jr. "Cryst
allographic target effect
s in magnetron splitterin
“g” describes the influence of the crystal orientation on the film thickness uniformity of the sputtering thin film. Much research has been done on aluminum targets instead of titanium. Japanese Patent Application Laid-Open No. 63-313975 discloses that, in view of the fact that the thickness of an aluminum thin film formed on a wafer by sputtering has a distribution in which a central portion is thicker and a peripheral portion is thinner, the crystal orientation of the aluminum target central portion is reduced. An aluminum sputtering target is described in which the ratio {220} / {200} is greater than that of the outer periphery. JP-A-2-15167 describes that
An aluminum sputtering target in which 50% or more of the area of the target surface is composed of a (111) crystal plane is described. JP-A-3-2369 discloses that as the aluminum target is consumed by magnetron sputtering, a ring-shaped groove is formed on the surface along with the rotation of the magnet, and the emission direction of atoms changes, resulting in a poor film thickness distribution. In order to solve the problem, the crystal orientation intensity ratio ｛10
It has been suggested that 0 / {110} be reduced as it enters the interior from the target surface. JP-A-3-1070
No. 9 describes a target characterized in that the crystal orientation content ratio {220} / {200} of the sputter surface of the aluminum target is 0.5 or more. Furthermore, Japanese Patent Application Laid-Open No. Hei 4-234170 describes an aluminum target having a grain size of 2 mm or less and a <110> fiber structure in which the fiber axis has an X-ray diffraction intensity of 20 times or more of randomness. I have.

SUMMARY OF THE INVENTION An object of the present invention is to provide a Ti target which has not been considered for differences in structure and crystal structure and non-uniformity so far, three times the standard deviation (3 times).
It is an object of the present invention to develop a Ti target capable of reducing or solving the problem of the standard relating to the film thickness distribution in which σ) is 5% or less.

[0008]

In order to solve this problem, the present inventor studied the effects of the crystal grain size and crystal orientation on the film thickness distribution which were not considered in the conventional Ti target. (A) the average crystal grain size at each part of the target is 500 μm or less, preferably 100 μm or less;
Ri, and that the basic variation of the average particle size of each part with respect to the average crystal grain size of the entire target obtained by averaging the average crystal grain size of each part is within 20% ±, even sputter surface (b) Target Measured by the X-ray diffraction method at

(Equation 2) Crystal orientation content ratio A of each portion was calculated by the Turkey be adjusted such that the variation relative to the average crystal orientation content ratios of the whole target obtained by averaging these crystal orientation content ratio is within 20% ± by It has been found that the problem of uniformity in the film thickness distribution, which could not be achieved with the quality of the conventional Ti target, can be reduced or solved.

Based on this finding, the present invention provides: (1) an average crystal grain size at each part of a target of 500 μm;
m Ri der below, and the average crystal grain size of the entire target
Variation of average grain size of each part to within ± 20%
High purity titanium sputtering target, characterized in that it, (2) X Senkai in sputtering surface of each part of the target
The crystallographic method measured by the orthogonal method and calculated based on the following formula
Crystal with the same content ratio A as the average of the entire target
The variation is within ± 20% of the orientation content ratio.
(1) high-purity titanium sputtering
(3) The average crystal grain size at each part of the ring target and (3) the target is 100 μm.
m or less, any of (1) and (2)
One of which is intended to provide a high-purity titanium sputtering target.

[0010]

With respect to the film thickness uniformity, the average crystal grain size at each portion of the target is set to 500 μm or less because of the emission characteristics of atoms from each crystal grain in the case of coarse crystal grains whose average crystal grain size exceeds 500 μm. Is remarkable, and the film thickness distribution becomes non-uniform. In particular, it is preferable that the average crystal grain size at each portion of the target is 100 μm or less.

The reason why the variation of the average grain size of each part with respect to the average crystal grain size of the entire target is set to ± 20% or less is as follows.
This is because if the variation exceeds ± 20%, the difference in the sputtering rate at each portion of the target becomes remarkable, and the film thickness distribution becomes non-uniform.

[0012] The crystal orientation content ratio A of each part measured by the X-ray diffraction method on the sputtering surface of the target is set to be within ± 20% of the average crystal orientation content ratio of the entire target. The reason for this is that, when plastic working is performed by forging or rolling in pure titanium in the target manufacturing process, the (002) plane is within ± 35 ° with respect to the target sputtered surface due to an increase in the working ratio. This is because a texture having an inclination is formed.
When evaluating the crystal orientation of a typical texture of titanium having a (002) plane having an inclination of ± 35 ° or less by an X-ray diffraction method, each diffraction peak becomes a crystal plane parallel to the target sputtering plane. Table 1
As shown in the figure, a crystal plane whose plane angle is within 35 ° from the (002) plane, that is, a (103) plane inclined by 30 °, 2
The diffraction peaks of the (014) plane inclined at 4 ° and the (015) plane inclined at 20 ° tend to increase together with the texture, and these crystal planes need to be considered in addition to the (002) plane. is there. The value of the crystal orientation content ratio strongly depends on the plastic working method and the working degree, but there is no strong correlation with the state of the crystal structure, and the crystal structure can be adjusted while maintaining the crystal orientation content ratio. No need to specify. However, the reason that the variation in the crystal orientation content ratio A of each portion relative to the average crystal orientation content ratio of the entire target is within ± 20% is that the crystal orientation content ratio A of each portion relative to the average crystal orientation content ratio of the entire target. This is because when the dispersion of the azimuth content ratio is ± 20% or more, the difference in the sputtering rate at each part becomes remarkable, and the film thickness distribution becomes non-uniform.

Next, a method of measuring the crystal orientation content ratio will be described below. The measurement sample is obtained by chemically removing a work-affected layer on the sample surface by electrolytic polishing or the like, and then measuring the intensity of a diffraction line corresponding to each crystal orientation with an X-ray diffractometer. The intensity value of the obtained diffraction line is calculated by calculating the relative intensity ratio of the diffraction line of each crystal orientation / JCPDS.
The Card is corrected with reference｝, and the crystal orientation content ratio is calculated from the corrected intensity. Table 1 shows the calculation method of the crystal orientation content ratio.

[0014]

[Table 1]

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 plastic working such as rolling and forging and heat treatment. The specific degree of 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, the average crystal grain size at each portion of the target is not more than 500 μm, and the average crystal grain size of each portion is equal to the average crystal grain size of the entire target. In order to achieve the condition of 20% or less, the titanium ingot is hot-worked at a temperature higher than the recrystallization temperature of the raw material to destroy the cast structure to make the grain size uniform and to finally form a uniform and 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.

The variation of the crystal orientation content ratio A of each portion is ± 20 with respect to the average crystal orientation content ratio of the entire target.
In order to achieve the condition of within%,
It is necessary to uniformly perform warm or cold working with a working ratio of 0.3 or more, and then perform a uniform heat treatment on the entire target in the recrystallization temperature range of the material to complete the recrystallization. Here, if the working ratio is less than 0.3, a uniform crystal orientation content ratio corresponding to the recrystallized structure after the heat treatment cannot be realized.

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 determined according to JIS.
-The cutting method described in H0501 was used.

[0020]

EXAMPLES Examples and comparative examples will be described below.

Example 1 and Comparative Example 1 A high-purity titanium ingot was subjected to plastic working and heat treatment to produce targets A, B and C having the crystal structures and crystal orientations shown in Table 2, respectively. The target was a flat sputtering target having a diameter of about 320 mm and a thickness of about 6 mm. The manufacturing method of targets A, B and C was as follows. (A) Target A: High-purity titanium ingot is hot-worked at 750 ° C., and then hot-worked at 400 ° C. with a working ratio of 1.5, and a uniform heat treatment is performed at 630 ° C. for 1 hour over the entire target. gave. (B) Target B: High-purity titanium ingot is hot-worked at 750 ° C., and then hot-worked at 400 ° C. with a working ratio of 1.5, using a heat treatment furnace with a narrow soaking temperature distribution. 600
Heat treatment was performed at 1 ° C. for 1 hour. (C) Target C: A high-purity titanium ingot was hot-worked at 800 ° C., and then a half of the forged material was worked at 400 ° C. at a working ratio of 2.
Warm working was performed at 0 and the other half at a working ratio of 1.1, and a uniform heat treatment was applied to the entire target at 600 ° C. for 1 hour.

The target was mounted on a magnetron type sputtering apparatus to form a film on an 8 ″ wafer substrate. The film thickness distribution was calculated from the sheet resistance measurement results at 121 points on the wafer by a four-terminal method. The standard deviation (σ) of the film thickness distribution of the sputtered film for the target is shown in Table 3. As shown in Table 3, of the targets A and B having a uniform crystal orientation content ratio A, the average crystal grain size was about 120 μm and the entire target was The target A having a uniform crystal grain size has better film thickness uniformity than the target B having a small average crystal grain size of about 80 μm but having different crystal grain sizes at the periphery and center of the target. The targets C having different content ratios A and different crystal grain sizes exhibited large non-uniformity in film thickness.

[0023]

[Table 2]

[0024]

[Table 3]

[0025]

【The invention's effect】 When sputtering Ti target
Between targets and when using the same target
Stable and stable film thickness distribution
It shows excellent film thickness distribution uniformity. As a result, on the wafer
The defective rate of the formed circuit such as an LSI is improved.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-5-214520 (JP, A) JP-A-4-116161 (JP, A) JP-A-5-214521 (JP, A) JP-A-6-214 10107 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) C23C 14/00-14/58

Claims (3)

(57) [Claims] An average crystal grain size at each portion of a target is 500 μm or less, and a variation of an average crystal grain size at each portion with respect to an average crystal grain size of the entire target is ± 2.
A high-purity titanium sputtering target characterized by being within 0%. 2. A crystal orientation content ratio A measured by an X-ray diffraction method on a sputter surface of each part of a target and calculated based on the following equation is the averaged crystal orientation content ratio of the entire target. The variation is ± 20%
2. The high-purity titanium sputtering target according to claim 1, wherein (Equation 1) 3. The target according to claim 1, wherein an average crystal grain size at each portion of the target is 100 μm or less.
The high-purity titanium sputtering target according to any one of the above.