JPH032369A - Aluminum target for sputtering - Google Patents

Abstract

PURPOSE:To obtain an Al target for sputtering capable of reducing inferior quality of IC chips, etc., on a wafer due to deficiency in film thickness by constituting the target so that crystal orientation (100) increases with the approach to the inner part from the target surface. CONSTITUTION:A small board-type sputtering target composed of high-purity Al of >=99.955% purity or high-purity Al in which metallic elements, such as Si, Cu, and Ti, are incorporated by <=10wt.% is constituted so that a crystal orientation intensity ratio [the ratio of (100) to (110)] by X-ray is high at the surface and is decreased with the approach to the inner part. This target can be produced by laying Al (alloy) sheets dissimilar to each other in crystal orientation on top of the other and applying rolling or forging to the above. Besides the above effect, uniform film thickness can be obtained even in the case of large-sized wafer by using this target.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an aluminum target for magnetron sputtering used as a wiring material for IC'PLSI and the like.

[Conventional technology]

With the development of the electronics industry, demand for ICs, LSIs, etc. is increasing significantly. The wiring used inside these elements is mainly made into a thin film by sputtering using high-purity aluminum or an alloy thereof as a target.

Unlike vapor deposition methods that involve evaporation of molten metal, it is known that in sputtering methods, the surface and internal crystal structure of the target greatly influences the characteristics of emitting atoms from the target.

For example, Weber, which uses single crystals of silver and copper,
et) experiments (Physical Review (Phys, Re)
v) 102.699 (1956)), it is stated that the density of atoms emitted from the target is high in the <110) direction, which is the closest packed direction of the crystal structure, and a spot-like distribution is obtained on the wafer. ing.

Therefore, targets of high-purity aluminum or its alloys have been manufactured with fine crystals and random crystal orientation in order to avoid the influence of crystal orientation and obtain a uniform thin film on the wafer. (Proceedings of the 25th Symposium of the Japan Society of Light Metals 33 (1984)) [Problems to be solved by the invention] However, even if such a target whose crystal is adjusted so as to obtain a uniform thin film is used, the target cannot be easily removed by sputtering. As the magnet wears out, ring-shaped grooves are formed on the surface along the rotation of the magnet, and the direction of emission of atoms changes, making it unavoidable that the film thickness distribution deteriorates.

For this reason, measures such as using a target with a significantly larger diameter than the wafer diameter, increasing the distance between the wafer and the target even if it reduces productivity, and increasing the sputtering gas pressure to reduce the film quality are necessary. Even with efforts such as double layering of magnets, etc., no satisfactory solution has been achieved.Also, in contrast to the trend of increasing wafer diameter to improve productivity, it is necessary to make the film thickness distribution uniform. has become one of the most difficult problems.

[Means to solve the problem]

In view of these circumstances, the present inventors have conducted intensive studies on the influence of the crystal orientation of high-purity aluminum and its alloys on atomic emission during sputtering, and have found that the [100] plane and the (1101 plane By adjusting the crystal orientation of the target so that the intensity ratio determined by the X-ray diffraction method decreases from the target surface to the inside, uniformity of the film thickness on the wafer can be obtained despite target wear. This discovery led to the completion of the present invention.

That is, the present invention provides a planar sputtering target made of high-purity aluminum or its alloy, in which the crystal orientation intensity ratio [{1001/(ratio of 1101)] due to X-rays on a plane parallel to the target surface is increased from the target surface to the inside. This is a manufacturing method characterized by manufacturing an aluminum target for sputtering, which is characterized by becoming smaller as it goes in, and an aluminum clad plate for the target by stacking plates with different crystal orientations and rolling or forging. The present invention provides an aluminum target for sputtering that allows a thick film to be obtained.

The present invention will be explained in detail below.

What is high-purity aluminum used as target material?J
99.955% or more as specified in IS H2111, and the alloy includes Si, Cu, Ti, Cr, W, and M, which are usually added to sputtering targets.
10% by weight or less of one or more metal elements such as Mg and Mg in high purity aluminum.

In the present invention, a target having a large X-ray crystal orientation intensity ratio [{1001/[1101 ratio]] on the target surface and a small crystal intensity ratio on the back surface is obtained by rolling or forging a flat plate having many of each crystal orientation. It can be easily obtained by crimping (cladding) a plurality of sheets.

Further, a plate having a crystal orientation of [1001 can be obtained by using the preferred recrystallization orientation, and a plate having a crystal orientation of [1101] can be obtained by using the texture of hot rolling or cold rolling. It is simpler if a single crystal is used, or it is possible to change the amount of processing on the front and back surfaces of the target, or it can be obtained even more easily by combining it with heat treatment.

A magnetron sputtering apparatus using a normal flat target is usually designed so that the outer periphery of the silicon wafer is located directly above the area of the target that is most consumed by magnetic force.

As clarified by the above-mentioned Wenner experiment, the <110> direction has the highest distribution density in the direction of emission of atoms by sputtering. Therefore, if there are many +1101 crystal orientations on the surface of the target, the film thickness at the outer periphery of the wafer will become too thick due to the positional relationship between the wafer and the target, so the crystal orientation intensity ratio [{1001/+110
The larger the ratio of 1 is, the more the emitted atoms are dispersed and the film thickness becomes uniform. However, as a ring-shaped groove is formed in the target as the target in the magnet part wears out, the emission distribution of atoms will not only be based on the crystal orientation, but will also be dispersed based on the shape, and the film thickness at the outer periphery of the wafer will gradually decrease. The film becomes thinner and the film thickness distribution on the wafer becomes non-uniform.

However, in the target according to the present invention, as the target is worn out, many crystal orientations [1101 planes] with good atomic emission characteristics directly above appear, which prevents the film thickness from decreasing at the outer periphery of the wafer and improves the film thickness distribution. The results are always uniform and good.

In addition, in order to further express such an effect, it is preferable that the portion where the crystal orientation intensity ratio [{1001/no+ ratio] is 1.0 or more is in the range of 175 to 3/4 of the target total thickness, and even more Preferably it is in the range of 174 to 1/2 of the total thickness.

〔Example〕

EXAMPLES The present invention will be explained below with reference to Examples, but the present invention is not limited thereto.

In addition, the measurement was performed by the following method.

α-rays are used for Cu- as the X-rays, and the X-ray intensity is measured by the method described below. That is, the surface to be measured is cut using a lathe or the like, and the extremely thin deformed region on the surface layer due to the cutting process is removed by chemical dissolution. Next, the intensity of the diffraction lines corresponding to each crystal orientation is measured using an X-ray diffractometer, and the intensity of the obtained diffraction lines is determined according to ASTM 4-0787.
A corrected intensity value is obtained by performing correction based on the relative intensity ratio of each crystal orientation described in .

Further, the film thickness distribution variation was determined by measuring the film thickness at nine points on the wafer and calculating from the maximum value (Xmax) and minimum value (Xmin) using the following formula.

[{Xmax −Xmin) /(Xmax +Xm1
n) ] A single crystal plate with aligned orientation was created.

The joint surfaces of each plate were roughened with a wire brush, and then rolled at a temperature of 350° C. and a rolling reduction of 25% to obtain a clad plate for a target.

A target with a thickness of 5 mm and a diameter of 5 inches was obtained from the clad plate. The bonding position was adjusted to be 1/4 of the total thickness from the surface.

Using this target, a thin film of about 1 μm was formed on a wafer with a diameter of 3 inches using a DC magnetron sputtering device, and the film thickness distribution was measured. In addition, the film thickness distribution was measured by converting it from the measurement of electrical resistance using the four-terminal method.

The output during sputtering was 500 W, the argon gas pressure was 8×10''-3 Torr, and the distance between the target and the wafer was 80 mm.

To measure the film thickness distribution, remove the surface with press batter for 30 minutes, then sputter on the wafer for 3 minutes to measure the film thickness, and then dry-batter for 20 hours and then sputter on the wafer for 2 minutes to measure the film thickness. Measurements were made.

Comparative Example 1 A target with a thickness of 5 mm and a diameter of 5 inches was obtained from a single-crystal plate with crystal orientation [1001] using high-purity aluminum with a purity of 99.999% by a solidification method (Bridgeman method).

Using this target, the film thickness distribution was measured in the same manner as in Example 1.

Comparative Example 2 A target with a thickness of 5 mm and a diameter of 5 inches was obtained from a single crystal plate whose surface orientation was aligned to [110] by a solidification method (Bridgeman method) using high-purity aluminum with a purity of 99.999%. .

Using this target, the film thickness distribution was measured in the same manner as in Example 1.

The obtained film thickness distribution results are shown in the table below.

30 minutes 20 hours Example 19% 8% Comparative example 110% 17% Comparative example 2 7% 15% [Effect of the invention] In the present invention, by increasing the crystal orientation [1101] from the target surface to the inside, the wafer This method not only reduces quality defects caused by insufficient film thickness on IC chips, etc., but also provides a uniform film thickness even on large wafers, so it has great industrial value.

Procedural amendment (spontaneous) Date of May, May, 1999 1, Indication of the case, 1999 Patent Application No. 134016 2) Name of the invention Aluminum target for sputtering 3, Person making the amendment Relationship to the case Patent applicant Address 4-5-33 Kitahama, Chuo-ku, Osaka Name (
209) Sumitomo Chemical Co., Ltd. Representative: Hideo Mori 4, Agent address: 5-5-33 Kitahama 4-chome, Chuo-ku, Osaka, Subject of amendment 6, Contents of amendment (1) Page 4 of the specification, No. 3 Correct "rotation" in the line to "lines of magnetic force".

that's all

Claims (4)

[Claims] (1) In a flat sputtering target made of high-purity aluminum or its alloy, the crystal orientation intensity ratio [{100
An aluminum target for sputtering, characterized in that the ratio of }/{110}] decreases from the surface of the target toward the inside. (2) In the aluminum target for sputtering according to claim 1, the X-ray crystal orientation intensity ratio of the target surface [ratio of {100}/{110}]
is 1.0 or more, and the crystal orientation intensity ratio [ratio of {100}/{110}] on the opposite surface (back surface of the target) is 1.0.
An aluminum target for sputtering, characterized in that the aluminum target is less than 0. (3) In the aluminum target for sputtering according to claim 1, the range in which the X-ray crystal orientation intensity ratio [ratio of {100}/{110}] is 1.0 or more is the thickness from the target surface. An aluminum target for sputtering, characterized in that the thickness is more than 1/5 and not more than 3/4. (4) A manufacturing method for the aluminum target for sputtering according to claim 1, which comprises stacking plates with different crystal orientations and manufacturing an aluminum clad plate for the target by rolling or forging.