JPS62103371A - Plasma chemical vapor deposition method - Google Patents

Abstract

PURPOSE:To form a laminar film, composite film and alloy film and to obtain a composite effect having optional characteristics by changing supply electric power impulsively, etc. thereby depositing films having different characteristics. CONSTITUTION:A continuous high-frequency signal is supplied from a high-frequency oscillator 14 to an initial stage high-frequency amplifier 9 and the signal programmed in a setting circuit is compared and amplified with the detection signal from a power detector 7 by a differential amplifier 10 in order to convert the above-mentioned signal to the impulsive low-frequency power or the high-frequency changing with time. The differential signal is supplied to the amplifier 9 which drives a high-frequency power amplifier 8 so as to obtain always the set power. The high-frequency is supplied via a matching circuit 2 to electrodes 4, 5 to generate glow discharge. More specifically, the peak power is changed periodically or with time to change the reaction and cracking of the gaseous raw material by plasma, by which the films having the different characteristics are successively deposited and the laminar film, composite film and alloy film are formed.

Description

[Detailed description of the invention] [Field of application of the invention] The present invention relates to a plasma CVD method. .

[Background of the invention]

The plasma CVD method is used in electronics, optical decoration, so-called secret machinery, etc. In addition, alloying, compounding,
There are many expectations for the creation of single-function devices made from new materials by thinning the laminated film, and research is actively progressing at domestic and overseas research institutions. Figure 8 shows a commonly used capacitively coupled plasma CVD method.
It shows the principle of law. Place the substrate 6 on the electrode 5,
A gaseous raw material is introduced into the chamber 3, an electric field is applied between both electrodes, and a constant power is applied as shown in Fig. 1(b) to cause a glow discharge, causing the raw material to decompose or react in the plasma and form a film on the substrate. It is something that is made to form. Therefore, the films that are deposited over time only have the same characteristics, and it is not possible to create a film with a unique effect by combining or depositing layers of films with different characteristics. However, even with this method, it is possible to form a composite thin film by introducing several types of raw material gases into the chamber. However, it is difficult to deposit all layers of films with different compositions.

In addition, as a related matter, Japanese Patent Application Laid-Open No. 50-102
No. 582 is known.

[Purpose of the invention]

An object of the present invention is to provide a plasma CVD method that can form a composite thin film within the same chamber without changing the raw material gas.

[Summary of the invention]

The first invention is a plasma CVD method [F] that can form a composite thin film, and its feature is that the glow discharge power is halved or the power is changed over time. That is, when a certain kind of raw material gas decomposes or reacts in plasma to form money, completely different substances or films with different properties are likely to be formed when the electric power is changed. That is,
By changing the peak power periodically or over time, it is possible to form a composite thin film deposited in a single layer with different materials and properties.The second invention relates to a method for applying the above method. Glow emission 1! It is characterized by being equipped with an application device that can arbitrarily program the power in pulses or over time.

[Embodiments of the invention]

Examples of the present invention will be described in detail below.

Embodiment 1 1 [iiN] is an explanatory configuration diagram showing an example of a plasma CVD apparatus of the present invention. In the figure, two electrodes 4 and 5 facing each other are installed in a chamber 3. A substrate 6 is placed on the electrode 5, and a source gas is introduced from the nozzle of the electrode 4. The variable power supply section includes a high frequency power amplifier 8 for supplying variable power and a first stage high frequency amplifier 9 for driving the high frequency power amplifier 8. The base of the transistor 12 of this amplifier 9 is connected to a high frequency oscillator 14 of 13.56 MHz.
z signal is supplied. Also, this 13.56M
l(z continuous high frequency wave to low frequency pulse form (13,56M
In order to generate high-frequency power (continuing for a period longer than the period of 13.56 MHz) or high-frequency power that changes over time, a signal programmed by a set value circuit 13 consisting of a microcomputer is sent to a power detector 7.
The detected power signal is compared and amplified by the differential amplifier 10 (5), and this deviation signal is supplied to the power control transistor 110 pace of the first stage high frequency amplifier 9 and drives the high frequency power amplifier 8 so that the power is always set. are doing. The fed back high frequency power is supplied to the electrodes 4.degree. 5 through the matching circuit 2, causing a glow discharge. Since the feedback system is implemented in this way, the values set in the program can be faithfully reproduced.

Hereinafter, an example implemented using wooden fl will be described in detail. An example of forming a nitride/recon film used as a protective film or an insulating film is shown. It is known that the film characteristics of silicon nitride when changing the electric power are as shown in FIG. As with any insulating film in general, as the film thickness increases, cracks may occur and it may become impossible to form the desired film thickness.

Raw material gas N2: 400 sccM+ NH,: 1
50secM.

5i) (4: 50SCCM 1 atmospheric pressure crab Q, 2'
forr.

Substrate temperature: 200℃, substrate: At, high frequency power: 150℃
A silicon nitride film was formed under two conditions: W and 350W. As a result, when the power was 150W, the film thickness was 1.1μm, and when the power was 3
At 50 W, cracks occurred at 1.3 μm. Then the third
As shown in the figure, high frequency power total 150W 5 minutes, 350W3
The critical film thickness at which cracks occur when laminated at a cycle of 1 minute was measured. As a result, the film thickness at the crack generation limit was 26 μm, which was twice the thickness of the conventional method. This is because, as is clear from FIG. 2, when the electric power is low, tensile stress is generated in the film, whereas when the electric power is high, compressive stress is generated in the film. Therefore, since tension and compression films are formed alternately, stress is relaxed and the crank generation limit value is improved. Therefore, if this method is used, the yield will be improved and the reliability will be greatly improved.

Example 2 Power: 300W, other conditions are the same as Example 1, about 1μ
After forming a film of 2 μm, a pattern was formed by plasma etching using a mixed gas of CF4:80 and 02:20 using a resist mask at intervals of 2 μm. As a result, a large undercut occurred as shown in FIG. 5(a). This phenomenon is commonly observed in thin film pattern formation, although the size of the undercut varies. However, as shown in Fig. 4, when the power was increased with a gradient of high-frequency power f 2 W 7 min to form a film of about 1 μm and patterned under the same conditions as above, the result was as shown in Fig. 5 (b). It was possible to form a pattern with significantly less undercut compared to the conventional method. This indicates that silicon nitride was deposited at different etching rates as the power changed, and this is also clear from the relationship between power and etching rate shown in FIG. This result is not only useful for improving patterning yield and reliability, but can also be applied to LSIs, etc., which are becoming increasingly dense. In addition, as shown in Part 4), the high-frequency power is pulsed high and low, and the high-frequency power is programmed to lengthen and the low pulses shorten over time. A pattern with less undercuts could be formed in almost the same way. In addition, plasma CVD
Almost the same effect was observed in insulating films such as 8102, which can be formed using

Example 3 Next, the a-8i, which is being studied for application to electrophotography:
)().There are various characteristics required for electrophotography, but among them, high resistance and high photosensitivity are required.Figure 6 shows the raw material gas 5i)(, :20chi, H2:
80% mixed gas 250secM, atmospheric pressure +0.
2 T"' * Radio frequency power, dark conductivity, and photosensitivity were investigated under the conditions of power of 200 to 1200W.As is clear from the figure, the dark resistivity increases as the power increases, but the photosensitivity (here The photosensitivity is the photoelectric density Jp estimated from the light attenuation rate of the surface potential and the incident luminous flux e.
F.

The ratio G '' J p / e F o ) decreases, indicating a contradictory phenomenon.Then, as shown in Fig. 7, the film characteristics were examined by alternately discharging with high frequency power of 200 W and 100 OW. Conductivity 4 x 10-130-13 (
n' and photosensitivity of 0.5, and film characteristics of high resistance and photosensitivity, which cannot be obtained with a single layer film using the conventional method, were obtained.

By varying the power periodically or over time in this way, a composite effect can be obtained by stacking or combining membranes with different membrane characteristics. Also a-8i:
) (It is clear that new effects can be expected if applied not only to insulators but also to metal 9 alloys that can be formed by plasma CVD.

As described above, in Examples 1 to 3, high frequency was used in the capacitive coupling method, but substantially the same effect can be obtained with either high frequency or direct current as the power source. Further, the present invention can also be applied to an electrodeless inductive coupling method.

It is believed that applying pulse control technology to the plasma etching method will be effective in forming fine patterns.

〔Effect of the invention〕

As described above, the present invention has the remarkable effect of depositing films with different characteristics by arbitrarily changing the power in a pulsed manner or over time to form a layered thin film or a composite thin film, thereby producing a complete composite effect.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of an apparatus for carrying out the plasma CVD method of the present invention, Fig. 2 is a silicon nitride film characteristic diagram that differs from the conventional method, Figs. 3, 4 (b), and 7 are Plasma emission 1 using the method shown in Figure 1! FIG. 4(a) is a schematic diagram of the power waveform of FIG. 4(b), and FIG. 5(a) is a schematic diagram of the plasma discharge power waveform of FIG. 4. (b) is a schematic diagram of the conventional method, FIG. 6 is an explanatory diagram of film characteristics when an a-8i:H film is formed by the conventional method, and FIG. 8 (a) is an explanatory diagram of a plasma CVD apparatus of the conventional method. (b) is an explanatory diagram of the plasma discharge power waveform in (a). 7...Power detector, 8...High frequency power amplifier.

Claims (1)

[Claims] 1. In the plasma CVD method, in which a raw material gas is reacted and decomposed by plasma and attached to a substrate to form a film, by changing the supplied power in pulses or arbitrarily over time, the reaction and decomposition by the plasma can be changed, resulting in different characteristics. A plasma chemical vapor deposition method characterized by sequentially depositing films to form layered films, composite films, and alloy films.