KR20110082338A - A method of texture control using differential speed rolling for ta sputtering target and sputtering target - Google Patents

Abstract

PURPOSE: A tantalum sputtering target and a manufacturing method thereof are provided to secure uniform layer quality and prevent contamination during sputtering by regulating the rotation speed ratio between top and bottom rolls and heat treatment temperature. CONSTITUTION: A method for manufacturing a tantalum sputtering target is as follows. Tantalum ingot or billet(100) is rolled and heat-treated for recrystallization. The rolling process is differential speed rolling where the rotation speeds of a top roll(210) and a bottom roll(220) are different from each other and reduction rate is 85%~95%. The heat-treatment process is performed at a temperature of 1000°C~1300°C for 10~60 minutes.

Description

Method of manufacturing tantalum sputtering target and tantalum sputtering target produced by the method {A method of texture control using differential speed rolling for Ta sputtering target and sputtering target}

The present invention relates to a method for producing a tantalum sputtering target and a tantalum sputtering target produced by the method.

In general, a metal wiring for driving devices such as transistors, storage batteries, resistors, and diodes in a semiconductor chip includes a 15 nm thick diffusion barrier layer comprising TiN or TaN, which is the same kind of nitride as the adhesive layer, on a 10 nm thick Ti or Ta adhesive layer. It is composed of sandwich structure of Al or Cu, which is the main wiring metal with a minimum thickness of 350nm.

Cu wiring structure is a structure in which trenches with a regular arrangement form a multilayer, and this structure is formed by etching using electron beam lithography on Si and SiO ₂ substrates, on which a barrier material such as Ta-TaN is deposited. Cu is then deposited by electrochemical method to fill the trench. One of the most important problems in the deposition of the Cu thin film is a barrier material.

Among the various types of barriers, Ta and Ta-N thin films are considered to be the most promising diffusion barriers to prevent Cu from diffusing into the substrate Si because of their high melting point and thermodynamic stability which does not react well with Cu at high temperatures. have.

In general, anti-Ta-N diffusion is formed by applying a reactive sputtering method for performing sputtering in a mixed gas of Ar and N _2, using a Ta target. However, when bias sputtering is performed using a commercially available Ta as a target material, when the bias voltage is increased on the substrate side, the plasma becomes unstable during long time film formation, causing a problem that the discharge is stopped. In addition, contamination due to the generation of a large amount of particles after film formation also occurs as a problem. These problems generate a large amount of defective products in the mass production line of the semiconductor device, and greatly reduce the manufacturing yield of the semiconductor device.

The root cause of the problem is known to be due to the commercially available Ta target material, i.e. the specific texture fraction in the texture in Ta, the size of the grains, and the like. Therefore, in order to solve the problem that occurs in the process of forming Ta-N diffusion barrier in the semiconductor manufacturing process, by increasing or decreasing the fraction of a specific texture in the texture of the Ta target material, the size of the texture is uniform and fine grains are controlled. You must have it.

A commercially available Ta target material is manufactured through a recrystallization process of rolling or forging a Ta ingot or billet and then heat treatment. Rolling of Ta ingots or billets, which are generally carried out, has a limit in miniaturizing grain average particle size. In addition, the manufacturing method of the existing Ta target material has a disadvantage that the texture fraction control of the texture is not free.

Accordingly, the present invention is to solve the above-mentioned problems, and to provide a method for manufacturing a tantalum sputtering target that allows the production of a tantalum sputtering target having a uniform average grain size while being able to freely adjust the texture fraction of the Ta target. The purpose is to provide.

It is another object of the present invention to provide a tantalum sputtering target having a grain average size of uniform size as manufactured by the above production method.

In order to achieve the above object, the present invention is a method for manufacturing a tantalum sputtering target comprising the step of rolling and recrystallization heat treatment Ta ingot or Ta billet (billet), the rolling is rotation of the upper roll and the lower roll Provided is a method for producing a tantalum sputtering target, characterized in that it is a two-speed rolling with different speed ratios.

It is preferable to perform the said double-speed rolling by 85%-95% of reduction rates. Further, the speed rolling is preferably performed by setting the ratio of the rotational speed of the upper roll to the lower roll as 1: 2 to 1: 4.

The recrystallization heat treatment is preferably heat treated for 10 minutes to 60 minutes at a temperature of 1000 ℃ to 1300 ℃. In addition, the recrystallization heat treatment is preferably carried out in a vacuum of 1 × 10 ^-4 torr or less.

The average particle size of the grain size of the tantalum sputtering target is preferably 1 ~ 20㎛.

In order to achieve the another object of the present invention, the present invention provides a tantalum sputtering target, characterized in that the average grain size of the grain size of the tantalum sputtering target is 1 ~ 20㎛ fine grain size .

The method for producing a tantalum sputtering target according to the present invention can be such that the average grain size of the grain size has a fine grain size of 1 ~ 20㎛, in particular, the rotational speed ratio and heat treatment temperature of the upper roll and the lower roll during double-speed rolling By controlling the texture fraction of the texture can be controlled. Therefore, the tantalum sputtering target manufactured according to the present invention can be usefully applied to the formation of a diffusion barrier layer in a semiconductor process because the film quality is uniform and no contamination occurs during sputtering.

1 is a view schematically showing a two-speed rolling process according to the present invention.
2 to 4 are orientation image micrographs and texture fraction distributions of Ta sputtering targets prepared in Examples 1, 4 and 5, respectively.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

1 is a view schematically showing a two-speed rolling process according to the present invention.

The method for manufacturing a tantalum sputtering target according to the present invention includes a process of rolling and recrystallizing a Ta ingot or billet 100. At this time, the rolling is a two-speed rolling for differently performing the rotational speed ratio of the upper roll 210 and the lower roll 220.

The Ta ingot or billet 100, which is used as a starting material for producing a Ta sputtering target, is typically obtained by casting Ta raw material after electron beam melting and uses a high purity of 99.99% or more. The Ta ingot or billet 100 may be easily purchased and used in general.

The Ta ingot or billet 100 may be subjected to a cleaning operation generally performed in the art before rolling. Here, the cleaning operation includes mechanical or chemical surface cleaning operations generally performed in the art as well as general cleaning operations for removing contaminants on the surface of the Ta ingot or billet 100.

Rolling of the Ta ingot or billet 100 is carried out by a two-speed rolling to perform a rotational speed ratio of the upper roll 210 and the lower roll 220 differently.

Unlike the conventional constant velocity rolling, the Ta ingot or billet 100 is subjected to shearing deformation, thereby making the average grain size of the grain size fine during the heat treatment recrystallization. In particular, the conventional constant velocity rolling has a limitation in size in miniaturizing the average particle size of grain size. However, the continuous rolling carried out according to the present invention can adjust the average particle diameter of the size of the crystal grains 1 ~ 20㎛. When the average grain size of the grain size is fine, it is known that the film formation speed during sputtering and film quality uniformity is high. Therefore, the film formation speed during film formation is high and film quality uniformity is increased by using Ta sputtering target material according to the present invention. .

The continuous rolling is carried out at a reduction ratio (thickness reduction rate) of 85% to 95%, and the rotational speed ratio of the upper roll 210 to the lower roll 220 is preferably 1: 2 to 1: 4. .

If the reduction ratio is less than 85%, there is a problem that the aggregate structure is not sufficiently developed, if the reduction ratio exceeds 95%, a problem that the thickness of the rolled material is unsuitable to be applied as a target occurs. . Therefore, it is preferable to perform the said reduction rate at 85%-95%.

When the ratio of the rotational speed of the upper roll 210 to the lower roll 220 is less than 1: 2, an aggregate structure similar to the conventional general rolling is formed, and the ratio of the rotational speed of the upper roll 210 to the lower roll 220 is When the ratio exceeds 1: 4, the rolling mill takes a lot of load or a non-uniform deformation occurs in the Ta plate, so the ratio of the rotational speed of the upper roll 210 to the lower roll 220 is 1: 2 to 1: 1. It is preferable to set it as the ratio of 4.

As described above, the double-rolled Ta undergoes a recrystallization heat treatment to refine the grain size. That is, the bi-rolled Ta is subjected to heat treatment to refine the grain size through recrystallization.

The recrystallization heat treatment is preferably heat treated for 10 minutes to 60 minutes at a temperature of 1000 ℃ to 1300 ℃.

In this case, when the temperature during the recrystallization heat treatment is less than 1000 ℃ problem of the recrystallization driving force is insufficient due to a long heat treatment time or recrystallization, and when the temperature during the recrystallization heat treatment exceeds 1300 ℃ grain growth occurs quickly This will occur. Therefore, the temperature during the recrystallization heat treatment is preferably performed at 1000 ° C to 1300 ° C.

In addition, when the recrystallization heat treatment time is less than 10 minutes based on the above temperature, recrystallization does not occur or partial recrystallization occurs. When the recrystallization heat treatment time exceeds 60 minutes, problems due to grain growth are caused. In this case, the recrystallization heat treatment time is preferably performed at a temperature of 1000 ° C to 1300 ° C for 10 minutes to 60 minutes.

The recrystallization heat treatment is preferably carried out in a vacuum state, in particular, the vacuum state is preferably 1 × 10 ^-4 torr or less, more preferably 1 × 10 ^-4 torr to 1 × 10 ^-6 torr . When the vacuum state exceeds 1 × 10 ^-4 torr, a problem occurs that the surface of Ta is oxidized, and a vacuum degree of less than 1 × 10 ^-6 torr not only takes excessive time to reach but also excessively high vacuum treatment cost. There is a problem. Therefore, it is preferable to perform recrystallization heat treatment at a vacuum degree in the above range.

According to the present invention, by appropriately changing the rotational speed ratio of the upper roll to the lower roll and the conditions during the recrystallization heat treatment, it is possible to induce the formation of a specific texture and to freely control the texture.

According to the present invention, it is preferable that the average particle diameter of the grain size of the tantalum sputtering target has a fine grain size of 1 to 20 μm. When the average particle size of the grain size of the sputtering target is less than 1㎛ may cause a large portion of the grain size variation or not partially recrystallized, and when sputtering the average particle diameter of the grain size of the sputtering target exceeds 20㎛ Problems such as uneven deposition may occur.

As described above, the Ta ingot or billet 100 is different from the general constant velocity rolling, and the ratio of the rotational speed ratio of the upper roll 210 and the lower roll 220 and the conditions in the recrystallization heat treatment, that is, the temperature time and the vacuum condition in the recrystallization heat treatment. By changing the, it is possible to control the texture to have various texture fractions, and there is an advantage in that the grain size is finely formed compared to the general constant velocity rolling in the recrystallization heat treatment under the same conditions. Accordingly, the deposition rate and film quality uniformity may be improved during sputtering.

Tantalum sputtering target according to the present invention is produced by the above method, the average grain size of the grain size of the tantalum sputtering target has a fine grain size of 1 ~ 20㎛. The tantalum sputtering target according to the present invention having the average grain size of the grain size described above has a fast film formation rate and high film quality uniformity during sputtering.

The present invention will be described in more detail with reference to the following examples, which are only presented to aid the understanding of the present invention, but the present invention is not limited thereto.

≪ Example 1 >

As shown in Fig. 1, the Ta ingot having a purity of 99.99% is cold-rolled at a rolling reduction ratio of 85% by setting the rotational speed ratio (V ₁ : V ₂ ) of the upper roll 210 to the lower roll 220 of the cold rolling mill as 1: 4. After rolling, the oil on the surface of the sample was removed using acetone and charged into a vacuum heat treatment furnace. The degree of vacuum in the heat treatment furnace was increased to 2 × 10 ^-5 torr using a vacuum pump, heated to 1200 ° C. at a heating rate of 10 ° C./min, maintained at 1200 ° C. for 1 hour, and then cooled in a furnace to obtain a vacuum at a temperature of 200 ° C. or lower. Was broken and the sample was taken out.

<Examples 2 to 5, Comparative Examples 1 and 2>

In the same manner as in Example 1, except that the rotational speed ratio (V1: V2), heat treatment temperature and time of the lower roll 220 to the upper roll 210 during cold rolling were the ratios shown in Table 1 below. Was carried out.

Experimental Example

The Ta sputtering target material obtained in Examples and Comparative Examples measured the average particle diameter and the fraction of the main texture of the grain size in the following manner and the results are shown in Table 1 below.

-Average particle size of grain size-

The average particle diameter of the grain size was measured using ASTM Method E-112.

-Texture fraction-

Textures were measured by Orientation Imaging Micorscopy (OIM) using Scanning Electron Microscopy equipped with an Electron BackScatter Diffraction (EBSD) analyzer.

-Orientation Imaging Micrograph-

In Examples 1, 4 and 5, the images measured by the texture fraction measuring method are shown in FIGS. 2 to 4.

division V ₁ : V ₂ Rolling reduction Heat treatment
Temperature (℃) Heat treatment
Minutes Major group organization and fraction Average grain size (㎛) Example 1 1: 4 85% 1200 60 <111> // ND 59.1% 18.3 Example 2 1: 4 85% 1100 10 <110> // ND 30.7% 6.5 Example 3 1: 3 85% 1000 10 <110> // ND 33.5% 2.5 Example 4 1: 3 85% 1200 10 <100> // ND 16.9% 6.8 Example 5 1: 2 85% 1200 30 <110> // ND 50.6% 7.7 Comparative Example 1 1: 1 85% 1000 60 <110> // ND 35.0% 87.4 Comparative Example 2 1: 1 85% 1200 60 <111> // ND 39.5% 72.0

As shown in Table 1, in the case of Examples 1 to 5 to which the two-speed rolling according to the present invention is applied, the average particle size of the grain size after recrystallization heat treatment is much finer compared to Comparative Examples 1 to 2 to which the conventional general constant-speed rolling is applied. have. In addition, the method of manufacturing a Ta sputtering target according to the present invention can be seen that the texture of the main texture is variously formed by the rotational speed ratio of the upper roll to the lower roll, the reduction ratio and the conditions during the recrystallization heat treatment. 2 to 4 can also be confirmed.

100: billet
210: upper roll
220: lower roll

Claims (9)

In the method of manufacturing a tantalum sputtering target comprising the step of rolling a Ta ingot or Ta billet and recrystallization heat treatment,
The rolling is a method for producing a tantalum sputtering target, characterized in that the two-speed rolling to perform a rotational speed ratio of the upper roll and the lower roll differently.
The tantalum sputtering target production method according to claim 1, wherein the double-speed rolling is performed at a reduction ratio of 85% to 95%.
The method of manufacturing a tantalum sputtering target according to claim 1, wherein the continuous rolling is performed by setting a rotational speed ratio of the upper roll to the lower roll in a range of 1: 2 to 1: 4.
The method for producing a tantalum sputtering target according to any one of claims 1 to 3, wherein the recrystallization heat treatment is performed at a temperature of 1000 ° C to 1300 ° C for 10 minutes to 60 minutes.
The method of manufacturing a tantalum sputtering target according to claim 4, wherein the recrystallization heat treatment is performed in a vacuum state of 1 × 10 ^-4 torr or less.
The method for manufacturing a tantalum sputtering target according to claim 5, wherein the recrystallization heat treatment is performed in a vacuum of 1 × 10 ^-4 torr to 1 × 10 ^-6 torr.
The method of manufacturing a tantalum sputtering target according to claim 1, wherein the crystal grain size of the tantalum sputtering target is set to a fine grain size of 1 to 20 µm.
Tantalum sputtering target produced by the manufacturing method of claim 1.
The tantalum sputtering target according to claim 7, wherein the average crystal grain size of the tantalum sputtering target is 1 to 20 µm fine grain size.

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