JP2901853B2 - 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 made of high-purity titanium having a crystal orientation different from that of the prior art for future semiconductor devices. Things.

[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.

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. Generally, it is generally known that the crystal orientation of a crystalline material greatly affects the emission characteristics of sputtered atoms from a target. From this, it is considered that also in the Ti target, the difference in crystal structure and the non-uniformity have a great influence on the emission characteristics of sputtered atoms, its directional characteristics, and the like.

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 An object of the present invention is to provide a Ti target in which the difference and the non-uniformity of the crystal structure have not been considered so far, and a value three times the standard deviation (3σ) is 5 in the Ti target.
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 of not more than%.

[0008]

In order to solve this problem, the present inventor studied the influence of the crystal orientation on the film thickness distribution which was not considered in the conventional Ti target. It is measured by the X-ray diffraction method on the sputter surface of the part, and the following equation

(Equation 2) The variation of the crystal orientation content ratio A calculated by the above with respect to the averaged crystal orientation content ratio of the entire target of the same target is ±.
It has been found that setting the content within 20% is effective.

Based on this finding, the present invention is based on the assumption that the above-mentioned crystal orientation content ratio A measured by the X-ray diffraction method on the sputtering surface of each portion of the target is obtained by averaging the same crystal orientation content ratio of the entire target. The variation is ± 2
Provided is a high-purity titanium sputtering target characterized by being within 0%.

[0010]

In order to realize uniformity of the film thickness, the crystal orientation content ratio A of each part measured by the X-ray diffraction method on the sputtering surface of the target varies with respect to the average crystal orientation content ratio of the entire target. Is within ± 20%. 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 as the working ratio increases. This is because a texture having an inclination is formed. When evaluating the crystal orientation of a typical texture of this titanium having a (002) plane having an inclination within ± 35 ° by an X-ray diffraction method,
Since each diffraction peak corresponds to a crystal plane parallel to the target sputtering plane, as shown in Table 1, (0
02) The crystal plane whose plane angle is within 35 ° from the plane, that is, the (103) plane inclined by 30 ° and the crystal plane inclined by 24 ° (01)
This is because the diffraction peaks of the (4) plane and the (015) plane inclined by 20 ° tend to increase together with the texture, and it is necessary to consider these crystal planes in addition to the (002) plane. 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, if the variation in the crystal orientation content ratio A of each portion is more than ± 20% with respect to the average crystal orientation content ratio of the entire target, the difference in the sputtering rate of each portion becomes remarkable, and the unevenness of the film thickness distribution becomes nonuniform. Occurs.

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.

[0012]

[Table 1]

The average crystal grain size at each part of the target is preferably 500 μm, particularly preferably 100 μm or less. In the case of coarse crystal grains whose average crystal grain size exceeds 500 μm, the difference in the emission characteristics of atoms from each crystal grain becomes remarkable, and unevenness in the film thickness distribution is likely to occur. It is also preferable that the variation of the average grain size of each part with respect to the average crystal grain size of the entire target is ± 20% or less. ± 2 variation
If it exceeds 0%, similarly, the difference in the sputtering rate at each portion of the target becomes remarkable, and unevenness of the film thickness distribution is likely to occur.

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.

The variation in the crystal orientation content ratio A of each part 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.

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 measurement of the average crystal grain size at each site was performed by a cutting method described in JIS H0501.

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

[0018]

EXAMPLES Examples and comparative examples will be described below.

Example 1 and Comparative Example 1 High-purity titanium ingots were subjected to plastic working and heat treatment to produce targets A and B having the crystal orientation shown in Table 2, respectively. Target shape is about 320m in diameter
m, a flat sputtering target having a thickness of about 6 mm. The manufacturing method of the targets A and B was as follows. (A) Target A: High-purity titanium ingot is hot-worked at 700 ° C., then hot-worked at 500 ° C. with a working ratio of 2.0, and a uniform heat treatment is performed at 600 ° C. for 1 hour over the entire target. gave. (B) Target B: hot-worked a high-purity titanium ingot at 700 ° C., and then, at 500 ° C., set one side half of the forged material to a working ratio of 2.0 and the other half to a working ratio of 0.9. Processing was performed, and a uniform heat treatment was applied to the entire target at 600 ° C. for 1 hour.

The target was attached to 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, the target A having a uniform crystal orientation content ratio A exhibited excellent film thickness uniformity. Thus, the target B having a different crystal orientation content ratio A showed large non-uniformity in film thickness.

[0021]

[Table 2]

[0022]

[Table 2]

[0023]

According to the present invention, when the Ti target is sputtered, the variation in the film thickness distribution and the variation thereof are small even between the targets and when the same target is used, and the film thickness distribution is stably excellent. Thereby, the defect rate of a circuit such as an LSI formed on the wafer is improved.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C23C 14/34

Claims (1)

(57) [Claims] 1. An average crystal orientation content ratio of the entire target having a crystal orientation content ratio A measured by an X-ray diffraction method on the sputter surface of each portion of the target and calculated based on the following equation 1. A high-purity titanium sputtering target, wherein the variation of the target is within ± 20%. (Equation 1)