JPH0718431A - Formation of thin film by bias sputtering - Google Patents

Abstract

PURPOSE:To improve the step covering property and to reduce the internal stress of a film by increasing a bias intensity in the initial thin film forming stage and decreasing it in the final thin film forming stage in bias sputtering. CONSTITUTION:A high-frequency power is supplied to the target 3 and substrate electrode 4 arranged in a vacuum vessel 1 provided with a vacuum pump 2 respectively from high-frequency power sources 5 and 6 to produce plasma. The target 3 is sputtered by the plasma to form a thin film on the surface of a substrate (not shown in the figure) placed on the substrate electrode 4. In this sputtering, the bias intensity is increased in the initial thin film forming stage to improve the step coverage of the substrate surface, and the bias intensity is decreased in the final flat thin film forming stage to reduce the internal stress of the entire thin film. The bias intensity is controlled by changing the fed power and phase difference stepwise with the phase shifter 7 and programmable controller 8 connected to the power sources 5 and 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film forming method by a bias sputtering method, and more particularly to a thin film forming method by a bias sputtering method capable of forming a thin film having low stress and good step coverage.

[0002]

2. Description of the Related Art Conventionally, a bias sputtering method has been known as a means for improving the coverage of steps on a substrate surface when forming a thin film on the substrate surface by sputtering.
In this method, high-frequency power is supplied to both the target and the substrate electrode to form a thin film on the substrate surface on the substrate electrode. For example, it is used for forming an alumina protective film of a thin film head for writing or reading on a magnetic recording medium.

In the formation of the alumina protective film of the thin film head, since the element has a complicated sectional shape and there are high steps, it is necessary to apply a bias in order to improve the coverage of the steps. The required strength of this bias differs depending on the type of element. If the bias strength is insufficient, the step coverage is poor, cracks occur in the film, and the performance of the head deteriorates. Generally, the higher the step,
Further, it is necessary to increase the bias strength as the shape of the steps becomes inversely tapered. Further, since the magnetic characteristics of the head are affected by the stress of the alumina protective film, it is necessary to reduce the internal stress. The alumina film has a property that the internal stress increases as the bias strength increases. In the conventional method, the film is formed with a constant bias strength. For this reason, if the bias strength is applied to cover the step, it is difficult to lower the internal stress below a certain value.

The alumina protective film is formed to be as thick as several tens of μm, but strong step coverage is not required in all parts during film formation. FIG. 2 shows an example of a cross section of the film when the film is formed with a bias applied, but the cross section of the alumina film 11 on the upper portion A of the step 9 is tapered (for example, J. Vac. Sci. Tecnol., Vol.
13, No. 6, Nov./Dec. 1976). It is considered that the bias strength may be weak to cover this tapered step.

[0005]

As described above, in the conventional thin film forming method by the bias sputtering method, the bias strength is constant, so that the step coverage can be improved and the internal stress of the film can be lowered. There was a problem that I could not do. Therefore, the design of the thin film head was also restricted by the process for forming the alumina protective film.

[0006]

The present invention has been made in view of the above problems, and provides a thin film forming method by bias sputtering which can improve the step coverage and reduce the internal stress of the film. Is intended.

A thin film forming method by bias sputtering of the present invention which achieves the above object is a bias sputtering method in which high frequency power is supplied to both a target and a substrate electrode to form a thin film on the substrate surface on the substrate electrode. It is characterized in that the bias strength is made strong at the initial stage of formation and is weakly controlled at the final stage of thin film formation where the flatness of the substrate surface is obtained.

The bias strength can be controlled so as to be changed stepwise. This change in bias intensity can be performed by controlling one or both of the bias applying power supplied to the substrate electrode and the target applying power supplied to the target. Further, the bias intensity can be changed by controlling the phase difference between the bias applying power and the target applying power.

When the bias input power is increased while the target input power is constant, the bias strength becomes stronger. Even if the target input power is reduced with the bias input power kept constant, the bias strength increases. When both the target input power and the bias input power are constant, the bias intensity becomes strong when the phase difference between them is about 180 degrees, and the bias intensity becomes weak when the phase difference is about 0 degree.

[0010]

According to the thin film forming method by bias sputtering of the present invention, the step coverage can be improved and the internal stress of the entire thin film can be reduced.

[0011]

Embodiments of the present invention will be described below.
FIG. 1 shows the structure of the bias sputtering apparatus used in the embodiment. The vacuum container 1 can be evacuated to a vacuum by a vacuum pump 2. High frequency power is supplied to the target 3 from the high frequency power supply 5 while the sputtering gas is being introduced, and at the same time, high frequency power is supplied to the substrate electrode 4 from the high frequency power supply 6. Is supplied, and electric discharge for film formation can be performed in the vacuum container 1. Further, the high-frequency power source 5 and the high-frequency power source 6 have their oscillation sources completely synchronized, and the phase shifter 7
The phase difference can be changed by. Furthermore, the high frequency power source 5, the high frequency power source 6, and the phase shifter 7
Is connected to the programmable controller 8,
The target input power, the bias input power, and the phase difference can be changed stepwise according to the setting.

Using the bias sputtering apparatus as described above, the bias strength is increased as shown in FIGS. 3 to 6 at the initial stage of thin film formation, and the thin film formation capable of obtaining surface flatness as shown in FIG. 2A. At the final stage, the control is performed weakly to form a thin film on the surface of the substrate placed on the substrate electrode 4.

In FIG. 3, the target input power is constant,
This is a case where the bias applying power supplied from the high-frequency power source 6 to the substrate electrode 4 is reduced stepwise to change the bias intensity stepwise. In this case, the phase difference between the high frequency power supplies 5 and 6 is 0 degree.

FIG. 4 shows a case where the bias input power is constant and the target input power supplied from the high frequency power source 5 to the target 3 is increased stepwise to change the bias intensity stepwise. The phase difference between the high frequency power supplies 5 and 6 is 0 degree.

FIG. 5 shows a case in which the bias strength is changed by gradually increasing the phase difference between the high frequency power supplies 5 and 6 while keeping the target input power and the bias input power constant.

Further, FIG. 6 shows the case where the target applied power, the bias applied power, and the phase difference between the high frequency power supplies 5 and 6 are comprehensively controlled to change the bias intensity stepwise.

As described above, the step coverage on the substrate surface can be improved by increasing the bias strength at the initial stage of thin film formation. On the other hand, the internal stress can be reduced for the entire thin film formed on the substrate surface by weakening the bias strength at the final stage of thin film formation where the step is sufficiently covered and flatness is obtained on the surface.

[0018]

As described above, according to the present invention, there is an effect that the internal stress can be reduced and the step coverage can be improved to form a thin film.

By applying it to the manufacturing process of the thin film head,
This has the effect of alleviating the restrictions on the design of the thin film head.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a bias sputtering apparatus used in an embodiment of the present invention.

FIG. 2 is a diagram illustrating a cross-sectional shape of a substrate surface having a step.

FIG. 3 is a graph of target applied power and bias applied power according to an embodiment of the present invention.

FIG. 4 is a graph of target applied power and bias applied power of the second embodiment of the present invention.

FIG. 5 is a target input power of a third embodiment of the present invention,
It is a graph of bias input power and phase difference.

FIG. 6 is a target input power of a fourth embodiment of the present invention,
It is a graph of bias input power and phase difference.

[Explanation of symbols]

 1 Target 4 Substrate electrode 5, 6 High frequency power supply 7 Phase shifter 8 Programmable controller

Claims (4)

[Claims] 1. A bias sputtering method in which high-frequency power is supplied to both a target and a substrate electrode to form a thin film on the substrate surface on the substrate electrode. In the initial stage of thin film formation, the bias strength is increased to flatten the substrate surface. A thin film formation method by bias sputtering, characterized in that the bias strength is controlled to be weak at the final stage of thin film formation. 2. The method for forming a thin film by bias sputtering according to claim 1, wherein the bias intensity is controlled stepwise. 3. The method for forming a thin film by bias sputtering according to claim 1, wherein the bias strength is changed by changing one or both of a bias applying power supplied to the substrate electrode and a target applying power supplied to the target. 4. The method for forming a thin film by bias sputtering according to claim 3, wherein the bias intensity changes the phase difference between the bias input power supplied to the substrate electrode and the target input power supplied to the target.