JPH04180569A - Control method for plasma cvd device - Google Patents

Abstract

PURPOSE:To improve operability without receiving the influence of a hollow cathode by using a pulse DC power source having a voltage-current characteristic of an either positive or negative square wave as a power source and controlling the pulse width, pulse height and pulse frequency of the square wave according to film forming conditions. CONSTITUTION:Reactive gases are supplied from a gas supply opening 15 of a gas supply system 14 into a reaction chamber 12 and a prescribed pressure is maintained in the reaction chamber 12 by a discharge system 16. A voltage is impressed to an electrode 13 from the power source 11 to activate the reactive gases and a film is formed on the surface of a substrate 17 by a chemical reaction. The pulse DC power source having the voltage-current characteristic of the either positive or negative square wave is used for the power source 11 at this time and is so controlled to a controller 18 that the pulse width(a), pulse height V and pulse frequency (f) of the square wave can be changed according to the film forming conditions. The operability of the plasma CVD is improved without receiving the influence of the hollow cathode in this way and the range where the film forming conditions can be changed is expanded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method of controlling a plasma CVD apparatus, using a pulsed DC power source as a power source, and improving operability by changing the width, height, and frequency of the pulse. By improving the film-forming conditions and changing the film-forming conditions, it is possible to apply it to large parts and reduce the effects of hollow cathodes.

[Prior art] Physical vapor deposition (PVD)
or depositi.

Chemical vapor deposition (CVD), which is easier to form a film on surface irregularities and holes, than
Depositino) has come to be used, and its use in industrial fields including semiconductor manufacturing is progressing.

One type of CVD is plasma CVD, which can form films at low temperatures by introducing plasma into the reaction space without using thermal energy to obtain the activated space necessary for chemical reactions. be. - Until now, a direct current power supply (DC power supply) has been used as a discharge power supply for such plasma CVD, and the
As shown in the figure, a DC power source 1 is connected to an electrode 3 in a reaction chamber 2. A gas supply system 4 is connected to this reaction chamber 2, and a reaction gas etc. is supplied to the inside from a gas outlet 5 in the reaction chamber 2. An exhaust system 6 is also connected to the reaction chamber 2 so as to circulate the inside of the reaction chamber 2 at a predetermined level. It is designed to hold pressure.

Then, a substrate 7 to be formed into a film in contact with the electrode 3 in the reaction chamber 2
, a reactive gas containing the material to be formed into a film is activated by plasma generated by discharge from the DC power source 1, and a film is formed by a chemical reaction with the surface of the substrate 7.

[Problem to be solved by the invention] In plasma CVD using such a DC power supply, the seventh
As shown in the figure, the characteristics of the DC power supply 1 are normally kept negative on the electrode side, and a nearly constant voltage of, for example, about 500 μ is applied. Most of the parts are small parts such as razor blades,
The target surface shape was one with no irregularities or holes.

However, research is underway to take advantage of the characteristics of plasma CVD and apply it to large parts. When attempting to achieve this, film formation may become impossible in that area due to the influence of the hollow cathode that occurs in the small holes formed in the large part that is the substrate, or the strength of the base material may decrease due to an increase in the substrate temperature in that area. There is the problem of inviting Ding.

In addition, with plasma CVD, as film formation progresses, a film is formed not only on the substrate but also on the inner wall of the reaction chamber, and abnormal discharge due to dirt inside the reaction chamber may cause damage to the surface of the film that has been formed up to that point. There are problems such as the formation of

For this reason, conventionally, the voltage supply from the DC power supply has been stopped immediately after the occurrence of abnormal discharge, but there has been a problem that the film-forming surface cannot be sufficiently protected.

Furthermore, in conventional plasma CVD, once the reaction gas is determined depending on the material to be deposited, the pressure range within the reaction chamber and the maximum supply voltage of the DC power supply must be determined to prevent abnormal discharge, and the operating range must be determined. The problem is that it is very narrow.

This invention was made in view of the problems of the prior art, and it is possible to perform plasma CVD without being affected by the hollow cathode.
The present invention aims to provide a control method for a plasma CVD apparatus that can improve the operability of the apparatus and expand the range in which film forming conditions can be changed.

[Means for Solving the Problems] In order to solve the problems of the above-mentioned prior art, the method for controlling a plasma CVD apparatus of the present invention uses either positive or negative power as a power source when controlling the film forming conditions of the plasma CVD apparatus. This method is characterized by using a pulsed DC power supply having voltage and current characteristics of a rectangular wave, and controlling the pulse width, pulse height, and pulse frequency of the rectangular wave according to the film forming conditions.

[Function J] According to this plasma CVD apparatus control method, a pulsed DC power source having voltage/current characteristics of either positive or negative rectangular waves is used as the power source, and this pulsed DC power source (hereinafter referred to as pulse D) is used as the power source.
Use C power source. ) The pulse width (duty ratio), pulse height (voltage), and pulse frequency that determine the shape of the rectangular wave are changed according to the film forming conditions, and a constant voltage is always applied using a conventional DC power supply. Compared to the case where the power source is not affected by abnormal discharge, the range in which the supply conditions from the pulsed DC power source can be changed is expanded.

[Example 1] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

Figure 1 shows a plasma CV to which the control method of the present invention is applied.
FIG. 3 is a schematic configuration diagram of an embodiment of the D device.

In this plasma CVD apparatus 1o, a pulsed DC power supply 11 is used as a power supply for plasma discharge.

This pulsed DC power source 11 is connected to an electrode 13 in a reaction chamber 12 . A gas supply system 14 is connected to the reaction chamber 12, and a reaction gas and the like are supplied into the reaction chamber 12 from a gas outlet 15.An exhaust system 16 is also connected to the reaction chamber 12 to guide the inside of the reaction chamber 12 in a predetermined direction. It is designed to hold pressure.

Then, the substrate 17 on which a film is to be formed is placed in contact with the electrode 13 in the reaction chamber 12, and the reaction gas containing the material to be formed into a film is activated by the plasma generated by the h'i current from the pulsed DC power source 11. , the film is formed by a chemical reaction on the surface of the base 17.

The pulsed DC power supply 11 used in such a plasma CVD apparatus 10 is a rectangular wave with negative voltage/current characteristics as shown in FIG. 2(a), or a rectangular wave with negative voltage/current characteristics as shown in FIG. In addition to using a so-called pulse power source with a rectangular wave with positive voltage and current characteristics, as shown in Figures 3 and 4 for the characteristics of a power source with negative voltage and current characteristics, pulse power sources are used. The voltage or pulse current value does not become 0,
It includes a power source whose characteristics change in the same way as a square wave with a certain value. Furthermore, regarding the rising or falling portion of a rectangular wave, a wave that changes completely instantaneously is not limited to a wave that changes over a certain amount of time.

This pulsed DC power supply 11 is provided with a control device 18, and the control device 18 controls the rectangular wave pulse width: a1, pulse height: ■, frequency, etc. as shown in FIG.
It is now possible to change f.

In the actual control by this control device 18, control is performed to change the voltage (which is the pulse height), (the frequency f with the wavelength changed), and (the ratio at which the voltage is applied (duty ratio): a/b). do.

With such a pulsed DC power supply 11, even when applying a pulsed DC voltage V having a negative voltage complete rectangular wave characteristic to the electrode 13 as shown in FIG. 2(a), the plasma CVD apparatus Due to the relationship with the time constant of W10, there may be a residual voltage vl on the electrode 13 side as shown in FIG. 3 as a result of voltage characteristic measurement.

The control range of the pulse DCi[11 by the control device 18 may be changed depending on various conditions such as the material to be deposited, the shape of the substrate 17, and the size and structure of the plasma CVD device 10. 1~50k
Film formation is performed while changing the duty ratio a/b in the range of 0.2 to 0.8 and the residual voltage ratio Vl/V in the range of 0 to 0.9.

In addition, the frequency f, duty ratio a/-b, and residual voltage V can be controlled not only within these control ranges but also within a wider or narrower range.
The ratio Vl/V of 1 may be controlled.

Next, a description will be given of film formation by plasma CVD, which is performed while controlling such a pulsed DC power supply 11 with the control device 18.

(2) Immediately after the start of plasma CVD, the temperature of the base 17 is low and abnormal discharge is likely to occur.

Therefore, the time during which the voltage V is not applied is increased by decreasing the voltage V, which is the pulse height, or by decreasing the duty ratio a/b, which is the ratio at which the voltage is applied.

(2) When the temperature of the substrate 17 rises, abnormal discharge becomes less likely to occur, so the duty ratio a/b is increased in order to increase the voltage V or increase the time during which the voltage V is applied, thereby increasing the growth of the film.

- As the growth of the film on the substrate 17 progresses, the film also forms on the inner wall of the reaction chamber 12 and becomes dirty.
Abnormal discharge is likely to occur, and there is a risk that debris and abnormal discharge may cause scratches on the surface of the deposited film.

Therefore, damage to the membrane can be prevented by reducing the voltage V, lowering the frequency f, or decreasing the duty ratio a/b, which is the ratio at which the voltage is applied, to increase the time during which the voltage V is not applied. do it like this.

■ If there is a small hole in the base 17, most of the cathode becomes a hollow cathode or the plasma density becomes non-uniform, making it impossible to form a homogeneous film, but the pulse frequency f can be changed using the pulsed DC power supply 11. These can be prevented by doing this.

As for the frequency f of this pulsed DC power supply 11, as shown in an example in FIG. The lowest frequency f that is not affected by the hollow cathode can be determined by the size of f.

In addition, if there is a small hole in the base 17, the size of the hole will gradually become smaller as the film formation progresses, so in addition to changing the frequency f of the pulsed DC power source 11, the voltage V and the duty ratio a It is also effective to change /b.

As described above, according to this plasma CVD apparatus control method, the pulse width a1 pulse height V1 pulse frequency f can be controlled by the control device 18 using the pulsed DC power supply 11. Compared to the conventional case, the control range of the power supply is greatly expanded, and it is possible to prevent hollow cathodes and non-uniform plasma density that occur when there are small holes in the base 17, as well as prevent abnormal discharge and improve the film surface. can be made more difficult to damage.

In addition, since abnormal discharges can be prevented by controlling the pulsed DC power supply 11, the operating range for film formation can be greatly expanded. As shown in comparison with the case of power supply, reaction chamber 1
The pressure range and maximum voltage of 2 can be changed over a wide range.

This also makes it possible to adjust the hardness, density, etc. of TiN to be formed.

Table 1 Operating conditions for TiN film formation r'+ (experimental example)
In the above embodiments, the case where the pulsed DC power supply mainly has negative voltage characteristics has been explained, but it is not limited to this, and may have positive voltage characteristics, and the shape of the pulse rectangular wave is also limited to a strictly rectangular shape. Not.

Further, the operating range of the pulsed DC power source is not limited to the embodiment, and may be determined depending on the apparatus, film forming conditions, etc.

Furthermore, it goes without saying that each component may be changed without departing from the gist of the invention.

[Effects of the Invention] As described above in detail with one embodiment, according to the control method for a plasma CVD apparatus of the present invention, a pulsed DC power supply having voltage/current characteristics of either positive or negative rectangular waves is used as a power supply. The pulse width, pulse height, and pulse frequency, which determine the shape of the rectangular wave of this pulsed DC power supply, are changed according to the film forming conditions, so a constant voltage can be constantly applied using a conventional DC power supply. Compared to the conventional case, it is possible to control the small hole in the substrate so that it does not become a hollow cathode and the plasma density does not become non-uniform, and it is also possible to prevent the occurrence of scratches due to abnormal discharge.

In addition, since a pulsed DCQ source is used, the range of power supply conditions that can be selected to prevent abnormal discharge can be greatly expanded.
Improves operability of power supply and film forming conditions.

[Brief explanation of the drawing]

Figure 1 shows a plasma CV to which the control method of the present invention is applied.
It is a schematic block diagram concerning one Example of D apparatus. FIGS. 2(a) and 2(b) are voltage characteristic diagrams of a pulsed DC power supply according to an embodiment of the present invention. FIG. 3 is a voltage characteristic diagram at the electrode when the pulsed DC power supply of the present invention is applied. FIG. 4 is a voltage characteristic diagram of a pulsed DC power supply according to another embodiment of the present invention. FIG. 5 is an explanatory diagram of the effect of pulse frequency to prevent the influence of a hollow cathode according to an embodiment of the present invention. FIG. 6 is a schematic diagram of a conventional plasma CVD apparatus. FIG. 7 is a voltage characteristic diagram of a conventional DC power supply. 10: Plasma CVD device, 11: Pulse DC power supply, 1
2: reaction chamber, 13: electrode, 14: gas supply system, 15: gas outlet, 16: exhaust system, 17: substrate, 18: control device, a: pulse width, b: pulse wavelength, a/b: duplex -Te, A ratio, f・Pulse frequency, vl Cruz height ('・Russ voltage), vl・Residual voltage. Applicant Ishikawajima-Harima Heavy Industries Co., Ltd. Agent Toru Sakamoto (and 1 other person) Figure 3 Figure 5

Claims (1)

[Claims] When controlling the film-forming conditions of a plasma CVD apparatus, a pulsed DC power supply with voltage and current characteristics of either positive or negative rectangular waves is used as the power supply, and the pulse width, pulse height, and pulse width of the rectangular wave are adjusted according to the film-forming conditions. A method for controlling a plasma CVD apparatus, characterized in that the pulse frequency is controlled.