JPH06336673A - Sputtering target for forming wiring and its production - Google Patents

Abstract

PURPOSE:To provide an Al alloy target contg. uniformly distributed group IVa or Va metallic elements. CONSTITUTION:This sputtering target for forming a wiring is made of a refined material consisting of 0.2-2.0wt.% one or more kinds of group IVa or Va metallic elements other than Ti, 0.2-40wt.% Ti and the balance essentially Al. The amt. of Ti is >=30wt.% of the total amt. of the group IVa or Va metallic elements. This target is produced by casting a molten alloy having the compsn. into an ingot by bottom pouring and using this ingot as stock.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sputtering target used for forming wiring of a semiconductor integrated circuit such as for a liquid crystal TFT panel and a method for manufacturing the same.

[0002]

2. Description of the Related Art In a semiconductor integrated circuit, a wiring containing aluminum as a main component has been conventionally used. This aluminum wiring has a drawback that atomic transfer (called thermomigration or stress migration) accompanying release of residual strain due to heat treatment when forming a semiconductor and atomic transfer (called electromigration) due to potential difference of the wiring are likely to occur. Yes, measures have been devised to prevent wire breaks and short circuits. For example, JP-A-61-251663 or JP-A-62-24073.
As described in No. 4, by adding a metal element of 4A or 5A group, these elements or compounds are precipitated at the grain boundaries to suppress diffusion.

[0003]

As a method for obtaining the above-mentioned aluminum wiring to which the metal elements of the 4A and 5A groups are added, there is a method of generating by sputtering using a target having a composition almost equal to that of the wiring or a method of using CVD. Applied. Among them, in the method using the target, how to make the composition of the target uniform is an important issue because the composition of the thin film depends on the composition of the target.

When casting a molten alloy in which a 4A or 5A group metal element is added to aluminum to obtain a large target for forming a wiring, the 4A or 5A group metal element and aluminum form an intermetallic compound. However, since this compound settles in the molten alloy, the concentration of the metal elements of the 4A and 5A groups is high in the lower part of the cast product, and conversely, the concentration of the metal elements of the 4A and 5A group is low in the upper part, There is a problem that a uniform composition cannot be obtained because the difference in concentration between the upper part and the lower part becomes large. The above-mentioned additive element is an element that increases the electric resistance of the thin film to be formed, and if these elements do not uniformly exist in the target, a very unfavorable thin film in which the electric resistance is partially different is formed. In particular, as the size of the liquid crystal TFT panel has become larger, the target used for the wiring material has also become larger, and the nonuniformity of the target structure described above has become a serious problem. It is an object of the present invention to provide a target having a uniform composition by casting and having a composition effective for wiring, and a method for manufacturing the target.

[0005]

Among the intermetallic compounds of 4A or 5A metal elements and aluminum, the present inventor has noticed that the intermetallic compound of titanium and aluminum has the smallest specific gravity and the slow sedimentation rate. The amount of titanium is 4A,
It has been found that a target with less uneven distribution of the 4A or 5A group metal element can be obtained by casting by adding 30% by weight or more to the 5A group metal element, and has reached the present invention.

That is, in the present invention, 0.2 to 6.0% by weight of one or more selected from the group 4A or 5A metallic elements except titanium, 0.2 to 6.0% by weight of titanium, Titanium is a sputter target for wiring formation, characterized in that it is an ingot material which is 30% by weight or more based on the total weight of metal elements of 4A or 5A group, and the balance is substantially aluminum. In order to prevent uneven distribution of elements, it is desirable that the target of the present invention is made by ingoting the molten alloy by the push-up casting method and machining it to form a target. That is, the production method of the present invention is a method for producing a sputtering target for forming a wiring, which comprises ingoting a molten alloy by a push-up casting method and machining it to obtain a target.

[0007]

When titanium and a metal element of the 4A and 5A groups other than titanium (hereinafter referred to as metal M) are present in the molten aluminum, a compound having a chemical formula of (Ti _x , M _1-x ) Al ₃ is usually formed. To do. If the content of titanium is increased, the specific gravity of the above compound becomes lighter, the sedimentation rate becomes smaller than that in the case where only the metal M except titanium is added, and uneven distribution of elements can be reduced. Specifically, in the case of adding tantalum, which has the largest specific gravity and is apt to be unevenly distributed among the 4A or 5A group elements that suppress atomic transfer of aluminum, titanium is 30% by weight or more based on the total weight of tantalum and titanium. In this case, even if the variation of the elements in the target is extremely small, it can be substantially eliminated.

Further, in the present invention, 4A or 5 excluding titanium
0.2 or more of one or more selected from the group A elements
.About.6.0% by weight and titanium at 0.2 to 6.0% by weight. This regulation is because when the total amount of titanium and other 4A or 5A group metal elements is less than 0.4%, the effect of suppressing atomic transfer of aluminum is small, and the addition elements are few and uneven distribution of the addition elements does not pose a problem. is there. Further, if the total amount of these elements exceeds 12% by weight, the electric resistance exceeds 15 μΩcm, which is not preferable as a wiring material.

The push-up casting method specified by the manufacturing method of the present invention is specifically a casting method using the apparatus shown in FIG. 4 shown in the examples described later, in which the molten metal is poured from the lower part of the mold to It is cooled by a chiller provided on the side wall. Therefore, it is also called the bottom pouring method. This is a particularly effective means for preventing uneven distribution of elements in the target of the present invention. In the push-up casting method, it is necessary to raise the molten metal surface while solidifying on the chiller surface, and preferably it is necessary to raise it at a rate of 30 mm / sec or less. This is because the segregation of the compound on the chiller surface and the central portion cannot be prevented if the rising speed is too fast.

[0010]

EXAMPLE The molten alloy shown in Table 1 melted at 1400 ° C. was cooled to 900 ° C., and then cast into an ingot having a width of 300 mm, a height of 250 mm and a thickness of 20 mm by the casting apparatus shown in FIG. The apparatus shown in FIG. 4 performs downward pouring and push-up casting from the sprue cup 1 via the runner 2. 3 shown in FIG.
Is a mold chiller, 4 is a molten metal, and 5 is a feeder frame. The rising speed of the molten metal in the mold at this time was 10 mm / sec. The obtained ingot was cut at the center which is ½ between the chiller surface and the opposing chiller surface, and the variations in the titanium and tantalum concentrations of the chiller surface and the central cross section were adjusted to the upper, lower, left and right sides.
The point was measured. The results are shown in Table 1. In addition, the results of measuring the variations in the concentrations of titanium and tantalum from the chiller surface of the samples 1 to 3 to the center of the ingot are shown in FIG.
As shown in FIG.

[0011]

[Table 1]

From Table 1 and FIGS. 1 to 3, it can be seen that in the examples of the present invention in which the amount of titanium added was larger than the amount of tantalum added, titanium and tantalum were not unevenly distributed and a homogeneous ingot was obtained. . An ingot produced in the same manner was rolled, and a plate having a thickness of 8 mm was welded to a backing plate to obtain a sputtering target. The thin film resistance as a sputtering film is additionally shown in Table 1. It can be seen from the value of the thin film resistance that when the addition amount of titanium and tantalum increases, the thin film resistance value increases, so that it is necessary to adjust the addition amount of these to meet the required thin film resistance value.

As comparative examples, 0.50% titanium, 1.50%
A molten metal of tantalum and residual aluminum (wt%) was cast into an ingot having a width of 300 mm, a length of 250 mm and a thickness of 20 mm by the top casting device shown in FIG. The casting apparatus shown in FIG. 5 has a structure in which the apparatus shown in FIG.
In the apparatus of FIG. 5, 7 is an upper chiller and 8 is a lower chiller. FIG. 6 shows the distribution of elemental concentrations of titanium and tantalum from the lower chiller contact portion to the upper chiller contact portion of the obtained ingot. As shown in FIG. 6, it can be seen that the ingot obtained by the top casting apparatus has a remarkable change in element concentration and cannot be expected to obtain a uniform thin film as a target.

In the above examples, tantalum was shown as the 4A, 5A group metal element other than titanium, because tantalum has the highest specific gravity among 4A, 5A and is most likely to segregate. When other 4A and 5A group elements are added, the variation in element concentration is smaller than when tantalum is added.

[0015]

According to the present invention, since the aluminum alloy target in which the 4A and 5A group metal elements are uniformly distributed can be obtained, the variation in the electric resistance of the produced thin film is small, and the atomic transfer of aluminum is less likely to occur. Can be obtained. Since the variation in the electric resistance of the thin film is small, it is possible to prevent the wiring of the semiconductor integrated circuit from being partially heated, so that the reliability of the semiconductor device can be improved. This is an extremely effective technique for improving the reliability of the wiring of a large device such as a liquid crystal TFT panel.

[Brief description of drawings]

FIG. 1 is a diagram showing an example showing a distribution of titanium and tantalum in an ingot which is a target of the present invention.

FIG. 2 is a diagram showing another example showing the distribution of titanium and tantalum in the ingot which is the target of the present invention.

FIG. 3 is a diagram showing a distribution of titanium and tantalum in an ingot which is a target of a comparative example.

FIG. 4 is a diagram showing a configuration of a push-up casting apparatus used in an embodiment of the present invention.

FIG. 5 is a diagram showing a configuration of a top casting device.

FIG. 6 is a diagram showing a distribution of titanium and tantalum in an ingot cast by a top casting apparatus.

[Explanation of symbols]

1 sprue, 2 runner, 3 cast chiller, 4 molten metal, 5
Feeder frame

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Saburo Oikawa 7-1-1 Omika-cho, Hitachi City, Ibaraki Hitachi Ltd. Hitachi Research Laboratory (72) Inventor Nobutake Konishi 7-1 Omika-cho, Hitachi City, Ibaraki Prefecture 1 Hitachi Ltd., Hitachi Research Laboratory

Claims (2)

[Claims] 1. One or more selected from the group 4A or 5A group metal elements excluding titanium is 0.2 to 6.0.
% By weight, 0.2 to 6.0% by weight of titanium, and the titanium is 30% by weight with respect to the total weight of 4A or 5A group elements.
The above is the sputtering target for wiring formation, characterized in that the balance substantially consists of aluminum. 2. One or more selected from the group 4A or group 5A metal elements except titanium is 0.2 to 6.0.
% By weight, 0.2 to 6.0% by weight of titanium, 4A of titanium
Alternatively, it is characterized in that it is 30% by weight or more with respect to the total weight of the elements of Group 5A, and the balance is made of an alloy melt which is substantially made of aluminum, is ingot-cast by a push-up casting method, is manufactured as a raw material, and is used as a target. Manufacturing method of sputtering target for wiring formation.