JPH02137323A - Method for forming low stress thin film - Google Patents

Abstract

PURPOSE:To deposit a thin film having desired properties and substantially no residual stress by previously depositing the thin film having the same polarity as that of the stress of a thin film to be formed and substantially the same magnitude as that of the stress on the rear face of a substrate. CONSTITUTION:When a low stress thin film is formed on the surface of a substrate (wafer) 11, a first thin film 12 having a predetermined stress is deposited on one side face of the substrate, a second thin film 13 having a stress of the same polarity as that of the film 12 is deposited on the other side face of the substrate, and the film 12 is then removed to reduce the stress of the film 13. Thus, the thin film having large original residual stress can be reduced in its stress without substantially varying the other properties of the thin film without setting specific film forming conditions and annealing after film forming.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forming a low stress thin film on the surface of a substrate (hereinafter referred to as a wafer).

[Conventional technology]

Conventionally, when forming thin films used for various semiconductor devices or X-ray mask substrates, etc., when it is necessary to reduce the stress of the thin film or control the stress to an appropriate level, the film forming method and film forming conditions have been changed. Either by precisely controlling specific conditions to obtain the desired stress, or by annealing the thin film 7 times under specific conditions after film formation to obtain the appropriate stress, or by stacking multiple thin films deposited using different methods. One of the methods was used to ensure that the overall stress was at an appropriate level. For example, a silicon nitride film deposited on a Si substrate by the IECR plasma CvD method generally has compressive stress, and when used as an X-ray mask substrate,
After depositing the silicon nitride film, it was necessary to anneal the Si substrate in a nitrogen atmosphere at several hundred degrees Celsius to change residual stress in the silicon nitride film into tension.

[Problem to be solved by the invention]

However, in the case of the first method described above, other properties of the thin film are sacrificed in order to properly control the stress in the thin film. Further, in the second method, since the annealing is performed at a high temperature, its application to device manufacturing processes is extremely limited, and the original properties of the thin film are changed by the annealing. Furthermore, the third film forming method has drawbacks such as not only complicated steps but also the lack of suitable combinations depending on the type of thin film and the inability to reduce stress.

An object of the present invention is to provide a method for forming a low stress thin film that solves the above problems.

[Means to solve the problem]

In order to achieve the above object, in the method for forming a low stress thin film according to the present invention, a first thin film having a desired stress is deposited on one surface of a substrate, and the first thin film is deposited on the other surface of the substrate. A second thin film having a stress of polarity equal to is deposited, and then the first thin film is removed to reduce the stress in the second thin film.

(Function) According to the present invention, a thin film that inherently has high residual stress can be reduced in stress without changing any other properties of the thin film without setting special film forming conditions or performing post-forming annealing. can.

〔Example〕

Next, as an embodiment of the present invention, a method for forming a low stress diamond film on the surface of a wafer will be explained step by step with reference to the drawings. As shown in FIG. 1(a), a high melting point metal film (for example, W film) 12 is deposited on the back surface of the S1 substrate 11 by RF sputtering. At this time, the gas pressure is approximately 2 Pa.
or 10Pa, RF power about 1V/- L5W
/aH: Control throttle, the W [12 is approximately 2 x 10L.

In order to generate compressive stress of dyn/ai, the Si substrate 1
The surface of W[12] curves into a concave shape depending on the film thickness of W[12] (FIG. 1(b)).

The thickness of the W film 12 is optimized depending on the thickness of the diamond film to be deposited later.

Next, for example, CH4 gas and 11. The Si substrate 11 is heated to about 1000° C. by [ECR plasma CVD method using gas].
While heating the diamond film 13 to this Si substrate]1
(Fig. 1(C)). The diamond film 13 deposited in this way has a typical I x 10iQdyn/
It has a compressive stress of aJ, which cancels out the compressive stress of the W film 12 previously deposited on the back surface of the Si substrate, thereby reducing the warpage of the Si substrate 11.

At this stage, a larger compressive stress is generated in the W film 12 than immediately after the deposition. After that, the Si substrate 11
When the W film 12 deposited on the back surface of the Si substrate 11 is removed by any etching method, such as wet etching, the stress caused by the W film 12 is removed, and the Si substrate 11 returns to its initial, almost flat state (see FIG. 1). (d)).

That is, in this state, the diamond film and Si
The stress on both substrates is almost zero.

In the above embodiments, a diamond film produced by OCR plasma CVD method was used as the thin film to be aimed at reducing stress, and a sputtered metal film was used as the warp correction thin film formed on the back surface of the substrate. The present invention is not limited to the combination of the following, but includes all cases in which a thin film having a stress of the same polarity and approximately the same magnitude as the stress of the target thin film is deposited in advance on the back surface of the substrate.

〔Effect of the invention〕

According to the present invention, a thin film having desired properties and having almost no residual stress can be deposited using the most general film forming conditions of a film forming method commonly used in the past.

[Brief explanation of the drawing]

FIGS. 1(a) to 1(,1) are schematic sectional views showing an embodiment of the present invention in the order of steps.

Claims (1)

[Claims] (1) Depositing a first thin film having a desired stress on one side of the substrate, depositing a second thin film having a stress of the same polarity as the first thin film on the other side of the substrate, and then depositing a second thin film having a stress of the same polarity as the first thin film. A method for forming a low stress thin film, the method comprising removing a first thin film to reduce stress in a second thin film.