JPH0193117A - Manufacture of film - Google Patents

Abstract

PURPOSE:To prevent the peeling off of a film as well as to reduce the deterioration in characteristics of a device caused by film stress by a method wherein a plurality of films having different degrees of stress, formed under the condition wherein the change of stress caused by the variation in condition of formation of films is small, are laminated. CONSTITUTION:A two-layer tungsten film of desired thickness is formed on a silicon substrate of low stress. The first layer tungsten film 7 of 400Angstrom is formed on the silicon substrate 6 at Ar gas pressure of 8mTorr, for example. Subsequently, the second tungsten film 8 of 1200Angstrom is formed on the above- mentioned tungsten film 7 using Ar gas pressure of 30mTorr in this case. As a result, the average stress S of the laminated film becomes S={(-1.2)X(400X10<-8>)+0.4X(1200X10<-8>)}/(400X10<-8>+1200X10<-8>)=0dy n/cm<2>. Accordingly, when the ratio of thickness of the films 7 and 8 is 1:3, the condition of average stress of 0 can be obtained. As a result, the peeling off of films can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of forming a film on a semiconductor substrate.

[Prior art and its problems] In a film forming process as part of a semiconductor device manufacturing process, it is necessary to create a film with controlled stress in order to prevent film peeling and to improve device characteristics.

In recent years, as semiconductor devices such as MO3) transistors have been miniaturized, the thickness of interconnects and gate electrodes have tended to increase in order to prevent increases in interconnect resistance. Therefore, the above-mentioned effect of increasing film stress is becoming more noticeable, and the demand for film stress control is increasing. Conventional sputter, C
In individual single-layer film forming methods such as VD and vapor deposition, it is necessary to find conditions under which a film having a desired film stress can be formed. However, it has been found from experience that controllability of film forming conditions to obtain the desired stress is generally poor, and is particularly poor near zero stress conditions, which are frequently requested. This led to deterioration of device characteristics due to film peeling and stress.

It is an object of the present invention to overcome these drawbacks of conventional film deposition methods and to provide a method for producing films with controlled stress.

[Means for solving problems]

The film manufacturing method of the present invention is characterized by laminating a plurality of films having different stresses, which are formed under conditions in which changes in stress due to changes in film formation conditions are small.

[Effect]

In order to clarify the operation of the film manufacturing method of the present invention, a typical example of a conventional film forming method will first be described. FIG. 2 shows a state in which a first layer film 1, which is one type of film, has been formed on a substrate 5 to a desired thickness.

FIG. 3 is a diagram showing stress characteristics with respect to certain parameters of film forming conditions. The vertical axis is the internal stress S, and the horizontal axis is the film forming condition C.
It shows. For example, when the desired stress is 80, the value of the film forming condition parameter C should be set to C0, but the setting error is expected to be ±ΔC, and C0-ΔC<C< Co +
It should be considered as ΔC. -The stress should therefore be considered as C=Co C=C6 and the error in stress is C=C.

Next, consider the case where films having different stresses are formed on the substrate 5 from the first layer to the first layer M as shown in FIG. In the figure, 1 is the first layer film, 2 is the second layer film, 3 is the third layer film, etc.
, 4 indicate the nl-th film, respectively. Let the stress of the kth Ji film of such a multilayer film be SK% and the film thickness be xK. The sum of the film thickness error Δx0 of the single layer film and the film thickness error of the multilayer film ΣΔx
By selecting CK for which ΔSK (ΔS0 holds true), the error in the average stress of a multilayer film is significantly improved compared to that of a single layer film.

(Example) Hereinafter, as a typical example of the present invention, a method of forming a film of a desired thickness on a silicon substrate with low stress on the average of two tungsten films will be described.

The desired average stress is 0±0.05 X 10” dyn/
cm” and the film thickness is 1600 people.

The film forming conditions are controlled using the argon gas pressure in the vacuum chamber of the apparatus. The RF power is 3 kW, the film forming temperature is room temperature, and the substrate bias is Ov. FIG. 4 shows the dependence of film stress on argon gas pressure when tungsten is deposited using a sputtering device. As shown in FIG. 4, over a wide range of gas pressures from Ar gas pressure of 5 mTorr to 1QmTorr, the stress maintains a substantially constant value of -1.2X 10"dyn/cm", and controllability is good. Also, controllability is similarly good in the range from 18mTorr to 40mTorr,
The stress remains constant at approximately 0.4 x 10"dyn/cm".

First, as shown in FIG. 5(a), a first layer tungsten film 7 is deposited on a silicon substrate 6 under an Ar gas pressure of 8 mTorr.
400 people will be formed. Subsequently, as shown in FIG. 5(b), a second layer tungsten film 8 is formed on the first layer tungsten film 7 by 1200 people at an Ar gas pressure of 30 mTorr.

The average stress S of the laminated film can be calculated using the following formula.

”A= ((-1,2) x (400xlO-')
+0.4x (1200xlO-”) / (40
0x10-'+1200xlO-") = Odyn/c
m2 As described above, by setting the ratio of the thicknesses of the first layer film 7 and the second layer film 8 to 1:3, the condition of zero average stress can be obtained.

Next, in order to evaluate the controllability of the average stress, we will compare the above case with the case where a single layer film is formed with a stress of 0 dyn/Cm" and a film thickness of 1600 people.The controllability of the Ar gas pressure is Since it is about ±2 mTorr, from Figure 4, 6 m
Torr to lQmTorr, and 18mTorr
From r to 4-layer mTorr, the stress maintains a substantially constant value, and the stress variation is so small that it can be ignored. Also 26m
Under Torr conditions, the average stress is 0 dyn/cm",
The stress variation at that time is ±0.25 x 10” d
Therefore, the stress variation of a single layer film is ±0.25 The average stress variation of the film is ±0
．． The stress controllability is significantly improved.

〔Effect of the invention〕

The film manufacturing method of the present invention makes it possible to design the average stress of a multilayer film and set it as designed, thereby preventing film peeling and reducing deterioration of device characteristics caused by film stress. Therefore, an outstanding effect can be achieved in improving the reliability of ultra-highly integrated circuits.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a multilayer film according to the present invention, FIG. 2 is a schematic cross-sectional view of a single-layer film, FIG. 3 is a diagram showing an example of stress for certain parameters of film-forming conditions, and FIG. The figure is a graph showing the dependence of film stress on argon gas pressure when tungsten is deposited using a sputtering device. Figure 5 is a diagram for explaining an example of forming a tungsten film with controlled stress on a silicon substrate. It is. ■...First layer film 2...Second N film 3...Third layer film 4...Nth layer film 5...Substrate 6...・ ・Silicon substrate 7... Tungsten film 1st layer 8... Tungsten film 2nd layer Agent Patent attorney Yoshiyuki Iwasa Figure 2 Compressive tensile l stress × 1010 [dyn/Cm2] 〉 1/'+Σ

Claims (1)

[Claims] (1) A method for manufacturing a film, which comprises stacking a plurality of films having different stresses, which are formed under conditions where changes in stress due to changes in film formation conditions are small.