JPH06291060A - Thin-film formation method - Google Patents

Abstract

PURPOSE:To improve the control of the composition ratio of a film, the suppression of particles, and film formation speed. CONSTITUTION:A plurality of types of feed gases 24 are pulsationally supplied inside a vacuum container 4 while the phases are shifted between the feed gases 24. Also, a high-frequency power is pulsationally supplied between a high-frequency electrode 6 and a ground electrode 8 from a high-frequency power supply 26a in synchronization with the feed gas 24 to be supplied pulsationally so that the level of the pulsive high-frequency power differs between at least two types of feed gases 24.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses, for example, Si on a surface of a substrate by a plasma CVD method using high frequency discharge.
The present invention relates to a thin film forming method for forming a compound thin film of N _x , SiO ₂ , a-SiGe, a-SiC or the like.

[0002]

2. Description of the Related Art FIG. 4 is a schematic view showing an example of a conventional plasma CVD apparatus. Two electrodes, in this example, a high frequency electrode 6 and a ground electrode 8 which also functions as a holder for holding the substrate 2 are housed in a vacuum container 4 which is evacuated by a vacuum exhaust device 14 so as to face each other. The substrate 2 is heated by the heater 10 in the ground electrode 8, for example.

The high-frequency electrode 6 has a large number of gas ejection holes in this example, and a plurality of kinds of raw material gas 24 are passed through the high-frequency electrode 6 and the gas introduction portion 16 connected thereto in the vacuum container 4. Is supplied. Each source gas 24 is
Each is supplied from the gas source 18 to the gas introduction unit 16 via the valve 20 for connection and disconnection and the mass flow controller 22 for adjusting the flow rate.

High frequency power is supplied from a high frequency power supply 26 between the high frequency electrode 6 and the ground electrode 8 via a matching circuit 28. This high frequency power is conventionally a continuous sine wave, the frequency of which is usually 13.56 MHz.

In such an apparatus, a desired source gas 24 is introduced into the vacuum container 4 to maintain the inside of the vacuum container 4 at, for example, about 0.1 Torr to 15 Torr, and a high frequency power source 26 supplies a high frequency wave between the electrodes 6 and 8. When electric power is supplied, high-frequency discharge is generated between both electrodes 6 and 8 and plasma 30
Occurs. Then, the source gas 24 is excited by the plasma 30 to generate excited active species, a chemical reaction proceeds, and a desired compound thin film on the surface of the substrate 2, for example, an insulating film such as SiN _x or SiO ₂ as described above, a -SiGe, a-
A semiconductor film such as SiC is formed.

[0006]

However, conventionally, a plurality of kinds of raw material gases 24 are simultaneously introduced into the vacuum container 4, and the high frequency power required to bring these raw material gases 24 into a plasma state is as follows. The gas was supplied between the electrodes 6 and 8 in accordance with the source gas 24 that is the most difficult to turn into plasma. Therefore, there has been a problem that the raw material gas 24, which is easily turned into plasma, is recombined in the gas phase to generate particles.

For example, when a silicon nitride (SiN _x ) film is formed as a thin film on the substrate 2, the source gas 24 contains silane (SiH ₄ ) gas, ammonia (NH ₃ ) gas, and / or
Alternatively, nitrogen (N ₂ ) gas is used. Since silane gas is more easily plasmatized than ammonia gas or nitrogen gas, the high frequency power may be small, but relatively high frequency power is required to convert the ammonia gas or nitrogen gas into plasma. Therefore, when a small amount of high-frequency power is supplied, ammonia gas or nitrogen gas is not sufficiently decomposed even if silane gas is sufficiently decomposed, so that a silicon nitride film with excess silicon is formed. On the other hand, when a large amount of high-frequency power is supplied, the gas phase reaction becomes vigorous, the reactive species for forming a film do not reach the substrate 2, and the film formation rate decreases. Also,
Since many particles are generated in the gas phase and adhere to the film, the quality of the film also deteriorates.

Therefore, the main object of the present invention is to provide a thin film forming method capable of controlling the composition ratio of a film, suppressing particles, and improving the film forming rate.

[0009]

In order to achieve the above object, the thin film forming method of the present invention is such that a plurality of kinds of raw material gases are pulsed in the vacuum vessel and the phases are shifted between the respective raw material gases. Pulsed high-frequency power supplied between the electrodes and synchronized with the source gas supplied in a pulsed manner, and the magnitude of the pulsed high-frequency power differs between at least two types of source gases. It is characterized by supplying as.

[0010]

According to the above method, depending on the individual source gas,
Since the magnitude of the high-frequency power for decomposing it by discharge can be changed, the rate of decomposing the source gas can be controlled, and thereby the composition ratio of the film can be controlled.

Moreover, since a high-frequency electric power having a magnitude suitable for each raw material gas can be supplied, it is possible to suppress the gas phase reaction to suppress the generation of particles, and to improve the film forming rate. You can

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a plasma C used for carrying out the present invention.
It is a schematic diagram showing an example of a VD device. The same or corresponding portions as those of the conventional example in FIG. 4 are denoted by the same reference numerals, and the differences from the conventional example will be mainly described below.

In this embodiment, the conventional valve 2 is used.
Instead of 0, a valve 20a that can be opened and closed at high speed is used. By this, a plurality of kinds of raw material gases 24 are supplied into the vacuum container 4 in a pulsed manner, and the phases of the raw material gases 24 are shifted.

Further, instead of the conventional high-frequency power source 26, a high-frequency signal generator 32 capable of intermittently generating an original high-frequency signal in a pulse shape, and a high-frequency power amplifier for power-amplifying the high-frequency signal from the high-frequency signal generator 32. The high frequency power supply 26a composed of 34 and 34 is used. The high-frequency signal that is the source of this is, for example, 13.56 MHz as in the conventional example.
However, the sine wave is not limited to this.

With such a high frequency power supply 26a, high frequency power is pulsed between the high frequency electrode 6 and the ground electrode 8 in synchronism with the source gas 24 supplied in a pulsed manner, and the pulsed high frequency power is generated. The electric power is supplied such that the magnitudes of the electric powers are different between at least two kinds of source gases 24.

According to such a thin film forming method, it is possible to change the magnitude of the high frequency power for discharge decomposition of the raw material gas 24 according to the individual raw material gas 24.
The rate of decomposing 4 can be controlled, and thereby the composition ratio of the thin film formed on the substrate 2 can be controlled.

Moreover, since it is possible to supply a high-frequency power having a magnitude suitable for each raw material gas 24, when the raw material gas 24 such as silane gas, which is easily turned into plasma, is introduced into the vacuum container 4, the high-frequency power is large. When the raw material gas 24 such as ammonia gas or nitrogen gas, which is hard to be turned into plasma, is introduced into the vacuum container 4, the magnitude of the high frequency power can be increased. The occurrence can be significantly suppressed. Therefore, it is possible to form a high-quality thin film with few particles attached on the substrate 2. Further, by suppressing the gas phase reaction, the reactive species for forming a film efficiently reach the substrate 2, so that the film formation rate is also improved.

Next, a more specific example in which a silicon nitride (SiN _x ) film is formed on the substrate 2 using the apparatus shown in FIG. 1 will be described below.

Example 1 Degree of vacuum during film formation: 0.6 Torr Substrate temperature during film formation: 300 ° C. Substrate: 6 inch Si wafer <100> Source gas: Silane gas 10 ccm Ammonia gas 50 ccm High frequency electrode: 200 × 200 mm Squares Source gas supply pattern: Fig. 2 Composition ratio of SiN _x film: Si / N = 0.75

The supply pattern of FIG. 2 will be described below.
Silane gas and ammonia gas each have a pulse width of 1
It was supplied at 0 msec and with a phase shift of 1 sec from each other.
High-frequency power is synchronized with both gases, pulse width 200m
Supplied in seconds. The magnitude of the high frequency power was 20 W when the silane gas was supplied and 100 W when the ammonia gas was supplied.

Compared with the comparative example in which the same source gas as above was continuously supplied and the high frequency power was continuously supplied in 100 W, the amount of particles (particle size 0.3 μm or more) was 100 particles / comparative example. The substrate was 5 in the above embodiment.
The number was reduced to 0 / substrate or less.

The film forming rate was 300 Å / min in the comparative example, but was improved to 400 Å / min in the above-mentioned example.

Further, the composition ratio of the film can be controlled only by the flow rate of the raw material gas in the comparative example, but in the above embodiment, it can be controlled by the high frequency power supplied in synchronization with each raw material gas.
Specifically, Si / N can be controlled in the range of 0.75 to 1.0.

Example 2 Degree of vacuum during film formation: 0.6 Torr Substrate temperature during film formation: 300 ° C. Substrate: 6 inch Si wafer <100> Source gas: Silane gas 10 ccm Ammonia gas 50 ccm Helium gas 30 ccm High frequency electrode: 200 × 200 mm square Source gas supply pattern: FIG. 4 Composition ratio of SiN _x film: Si / N = 0.75

In the second embodiment, in order to maintain the gas pressure in the vacuum container 4 stable and to promote the continuation of the plasma 30, as the source gas 24, helium is used in addition to the film forming gas (reaction gas). This is an example in which the gas is also supplied in pulses.

The supply pattern of FIG. 4 will be described below.
The silane gas, the ammonia gas, and the helium gas were supplied with a pulse width of 10 msec and a phase shift of 2 sec from each other. The high frequency power was supplied with a pulse width of 200 msec in synchronization with each gas. The magnitude of high frequency power is
The silane gas was supplied at 20 W, and the ammonia gas and helium gas were supplied at 100 W.

In the case of the second embodiment, the film forming speed is 450.
Å / min and improved. The other particle generation amount and film composition ratio control were the same as in Example 1 above.

The plasma maintaining gas may be an inert gas other than helium gas such as argon gas.

[0029]

As described above, according to the present invention, it is possible to change the magnitude of the high-frequency power for discharge decomposition of each raw material gas, so that the rate of decomposition of the raw material gas can be controlled. It is possible to control the composition ratio of the film.

Moreover, since a high frequency power having a magnitude suitable for each source gas can be supplied, it is possible to suppress the gas phase reaction to suppress the generation of particles and to improve the film forming rate. You can

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of a plasma CVD apparatus used for implementing the present invention.

FIG. 2 is a diagram showing an example of a supply pattern of raw material gas and high frequency power.

FIG. 3 is a diagram showing another example of the supply patterns of the source gas and the high frequency power.

FIG. 4 is a schematic view showing an example of a conventional plasma CVD apparatus.

[Explanation of symbols]

 2 substrate 4 vacuum container 6 high frequency electrode 8 ground electrode 20a valve 24 source gas 26a high frequency power supply 30 plasma

Claims (1)

[Claims] 1. A thin film forming method for forming a compound thin film on a surface of a substrate by a plasma CVD method in which plasma is generated in a vacuum container by high-frequency discharge between electrodes facing each other, wherein a plurality of kinds of raw materials are contained in the vacuum container. The gases are supplied in pulses, and the phases are shifted between the source gases, and high-frequency power is pulsed between the electrodes in synchronization with the source gases supplied in a pulsed manner The method for forming a thin film, wherein the high frequency power is supplied so as to be different between at least two kinds of source gases.