JPH04324655A - Manufacture of thin film - Google Patents

Abstract

PURPOSE:To form a low stress thin film having a desired stress for a semiconductor element, by calculating film stress of a thin film during film formation, from measurement results of X-ray diffraction, and controlling the film formation condition of a thin film forming equipment by using calculation results, so as to conform the film stress to a desired value. CONSTITUTION:A substrate 14 is arranged in a thin film forming equipment, X-ray diffraction caused by a thin film formed on the substrate 14 is measured, and film stress of the thin film is calculated from the measurement results of the X-ray diffraction. By using the results, the film formation condition of the thin film forming equipment is controlled, so as to obtain film stress equal to a desired value. For example, an X-ray diffraction equipment is installed in a magnetron sputtering equipment, and a tungsten film is formed while X-ray diffraction is measured. As to the X-ray diffraction equipment, X-ray is projected on the substrate 14 surface at an angle phi to the vertical direction from an X-ray source 26, and diffracted ray is measured with an X-ray detector 28. The stress of the tungsten film formed on the substrate 14 is controlled by argon output during sputtering and the output of an RF power supply 22.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a method for manufacturing thin films for semiconductor devices.

0002

[Prior Art] For example, among the thin films used in the manufacturing process of semiconductor devices, tungsten is and heat-resistant metals such as molybdenum, WSi2, MoSi2, TaSi2
, TiSi2 and other silicides, and TiN and ZrN and other nitrides themselves have large internal stresses. This large internal stress not only causes cracks in the film and peeling of the film, but also causes defects in the underlying substrate such as silicon or GaAs, and damages the transistors fabricated on this substrate. and MOSFET
It may cause deterioration of the characteristics.

Therefore, it is necessary to control the internal stress to a low value. For example, the stress of a tungsten thin film can be reduced to a low value by controlling the argon pressure during sputtering, as shown in FIG. 5 of the above-mentioned document. It becomes possible to do this.

However, it is known that the stress strongly depends not only on the pressure of argon but also on the input power during sputtering, and therefore changes greatly due to minute changes in the input power. Therefore, a low stress membrane,
In order to control the stress to a desired value, it is necessary to precisely control the formation conditions during film formation.

On the other hand, stress is currently measured by a method of forming a thin film of a constant thickness and then measuring the warpage of the substrate to calculate the stress, as shown in the above-mentioned document. Therefore, when trying to form a low-stress tungsten thin film by sputtering, for example, the argon pressure and input power are varied in advance to obtain a reference film stress under each condition, and the formation conditions are controlled according to that data. will be carried out.

[0006]

[Problems to be Solved by the Invention] However, according to such a formation method, the stress of the film can only be determined by measurement after formation, and therefore the formation conditions cannot be controlled very precisely. Moreover, if a problem arises, such as a tungsten film being formed on the inner wall of the sputtering device, which substantially changes the formation conditions, the response to the problem will be delayed.

[0007]

[Means for Solving the Problems] In order to solve the problem of controllability when forming a low stress film, the present invention provides a film forming apparatus with
To provide a thin film manufacturing method in which film stress can be precisely controlled by providing a means for measuring film stress simultaneously with the film forming process and a means for automatically controlling forming conditions so that the stress becomes a desired value.

[0008]

[Operation] Using X-ray diffraction as a means of measuring this membrane stress,
The stress of the thin film being formed is obtained from the measured value, and by controlling the film forming parameters based on this, the stress of the thin film can be precisely controlled at all times.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 schematically shows an embodiment of the apparatus of the present invention, in which a tungsten thin film is formed by magnetron sputtering.

In FIG. 1, an anode electrode 1 is rotatably supported in a sealed chamber 10 containing argon.
2, a cathode electrode 16 is placed in the chamber 10 facing the anode electrode 12, and a tungsten target 18 is placed on the surface of the cathode electrode 16 facing the anode electrode. It has been done. A permanent magnet 20 is arranged close to the opposite surface of the cathode electrode 16, and a radio frequency electrode 22 is supplied with high frequency power through a match box 24 to this cathode electrode to target high density plasma using an orthogonal electromagnetic device. 18 to form a tungsten thin film on the substrate 14.

An X-ray diffraction device is attached to the conventional magnetron sputtering device constructed as described above, and a tungsten film is formed while measuring X-ray diffraction. The X-ray diffraction device is formed by an X-ray source 26 and an X-ray detector 28. X-rays from an X-ray source 26 are directed at the surface of the substrate 14 at an angle φ with respect to the normal, and the diffraction lines are measured by an X-ray detector 28 . The stress of the tungsten film formed on the substrate 14 can be controlled by the argon pressure during sputtering and the output of the RF power source 22, as shown in FIG. It can be controlled by the output of the RF power source 22. When the output of the RF power source 22 is kept constant and the argon pressure is changed, the stress of the tungsten film that is formed is reduced to compressive stress (
The stress can be changed significantly from - sign) to tensile stress (+ sign).

On the other hand, as shown in FIG. 3, the film formation rate does not depend much on the argon pressure, is almost constant in the pressure range of 10 to 40 mTorr, and is a function only of the RF output.

On the other hand, the stress of the film is calculated from the shift amount of the diffraction peak of X-ray diffraction. Here, we focus on diffraction from one diffraction surface, and measure the deviation of the diffraction peak from the value when stress is 0 as a function of the incident angle of X-rays, using the well-known relationship.

[0014]

[Math 1]

A method of calculating the stress σ from the following equation is used. Here, aφ is the measured lattice spacing at medium incidence angle, a
0 and an are the lattice spacing when the stress σ is 0, the lattice spacing in the direction perpendicular to the surface, and Ef and Vf are the Young's modulus and Porin ratio of tungsten, respectively.

[0016] In film formation, after forming a certain film thickness, the stress is measured as described above, the film forming conditions are adjusted, and the film is formed again. By repeating this process, a tungsten film having the desired average stress is formed. It becomes possible to do so.

Now, the tungsten film whose average stress is 0 is 1
Consider the case where the film is formed with a thickness of μm. According to data measured in advance, σ=0 at 21 mtorr at 2kW. It is assumed that a 0.1 μm film is first formed under these conditions, and then its σ is measured to obtain the value of σ1. This is a change in stress due to a shift in the relationship between stress and argon pressure due to some change in conditions. Therefore, from now on σ=
The argon pressure PAr that becomes 0 cannot be predicted. Therefore, we predicted P2 Ar (<21 mtorr) from the monotonically increasing dependence, and measured the stress after forming a 0.1 μm thick film under this condition.

[0018]

[Math 2]

Stress (value obtained by X-ray diffraction), σi
and ti are the stress and film thickness formed in each step. From this value, σi=σi(PAri) can be calculated. By repeating this step several times, the current relationship σ = σ (PAr) can be obtained, and from this relationship, the conditions for bar σ = 0 are predicted, and finally bar σ =
0. A tungsten film with a thickness of 1 μm can be obtained. To repeat this step automatically, the automatic control system automatically controls the argon pressure and RF power, and also automatically measures the X-ray diffraction, calculates the stress, and predicts the stress. equipment is required. In Figure 1 this is the X-ray source 26,
It is composed of a line detector 28 and a parameter calculation/control device 30.

Furthermore, by using a powerful synchroton radiation source as the X-ray source, the time for X-ray diffraction measurement can be extremely shortened, and control can be performed by substantially simultaneous measurement with film formation.

Although only the case where the tungsten film is formed by the sputtering method has been described here, the present invention is also applicable to the case where the tungsten film is formed by the vacuum evaporation method, the CVD method, or the like.

[0022]

As explained above, according to the present invention, the thin film forming apparatus is equipped with a means for measuring film stress by X-ray diffraction, and the film forming conditions can be precisely controlled during thin film formation. It becomes possible to form a thin film with a desired stress.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an apparatus for carrying out the method of the invention.

FIG. 2 is a graph showing the relationship between stress and inert gas pressure.

FIG. 3 is a graph showing the relationship between high frequency power and film deposition rate.

[Explanation of symbols]

10 Chamber 12 Anode electrode 14 Semiconductor substrate 16 Cathode electrode 18 Target 20 Permanent magnet 22 High frequency power supply 24 Matching box 26 X-ray source 28 X-ray detector

Claims (2)

[Claims] 1. A substrate is placed in a thin film forming apparatus, X-ray diffraction due to the thin film formed on the substrate is measured, and the film stress of the thin film is calculated from the measurement results of the X-ray diffraction. 1. A method for producing a thin film, which comprises controlling the forming conditions of a thin film forming apparatus using a method such that the film stress reaches a desired value. 2. The method according to claim 1, wherein the thin film is formed by magnetron sputtering, and the forming conditions are inert gas pressure and/or high frequency power.