JPH0776780A - Plasma cvd method and its devide - Google Patents

Abstract

PURPOSE:To improve film forming efficiency and to enable high-speed film formation by successively applying high-frequency voltages varying in amplitude and repeating the voltage application in the CVD method for converting plural film forming gases to plasma by the application of the high-frequency voltages. CONSTITUTION:The plural gases are introduced as the film forming gases into a vacuum vessel and the high-frequency voltages having the amplitude of the varying magnitude meeting the conversion of the respective gases to plasma are successively applied thereto. This operation is repeated. The gases which as liable to be cracked by the low voltage are mainly cracked at the time of applying the voltage of the small amplitude. The gases which are hardly cracked by the low voltage are cracked as well or the gases which are easily cracked by the high voltage are mainly cracked at the time of applying the voltage of the large amplitude. Consequently, the films are efficiently formed by regulating the amplitude of the respective high-frequency voltages to be repetitively applied and the time distribution thereof according to the kinds of the gaseous raw materials and the desires film compsns. The films are formed at a high speed without changing the film compsns. by a voltage increase.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma CVD method for forming a film on a substrate and an apparatus for carrying out the method when manufacturing a device using a semiconductor such as a thin film transistor and various sensors using a semiconductor, a solar cell and the like. .

[0002]

2. Description of the Related Art Various types of plasma CVD apparatus are known. As a typical example thereof, a parallel plate type plasma CVD apparatus shown in FIG. 4 will be described. This apparatus has a vacuum container 1 and an electrode 2 also serving as a substrate holder for setting a film formation substrate S2 therein and this electrode. Is provided with an electrode 3 facing to.

The electrode 2 is usually a ground electrode, and
A heater 21 for heating the substrate S2 placed thereon to a film forming temperature is additionally provided. The heater 21 is separated from the electrode 2 when the substrate S2 is heated by radiant heat. The electrode 3 is a voltage application electrode for applying a high-frequency voltage or a direct-current voltage to the film-forming gas introduced between the electrode 3 and plasma, and in the illustrated example, a high-frequency power source 5 via a matching box 4. Are connected.

In the illustrated example, the electrode 3 has a porous electrode plate 32 in the opening of a gas nozzle 31 which constitutes a part of the electrode.
The electrode plate 32 is provided with a large number of gas supply holes each having a diameter of about 0.5 mm so that the gas supplied from the gas nozzle 31 is entirely discharged from each hole between both electrodes. I am doing it. Such a configuration is suitable for forming a film on a wide area substrate.

An exhaust device 6 is connected to the vacuum container 1 by piping, and a gas supply unit 7 is connected to the gas nozzle 31 by piping. The gas supply unit 7 includes one or more mass flow controllers 711, 712 ...
.. and gas sources 731, 732 ... Supplying a predetermined amount of film forming gas via the on-off valves 721, 722.
·It is included.

According to this parallel plate type plasma CVD apparatus, the substrate S2 to be film-formed is set on the electrode 2 in the vacuum container 1, and the inside of the container 1 is brought to a predetermined vacuum degree by the operation of the exhaust device 6. The film forming gas is introduced from the gas supply unit 7 through the gas supply holes of the nozzle 31 and the electrode plate 32. Further, a high-frequency voltage is applied to the high-frequency electrode 3 from the power source 5, the gas introduced thereby is turned into plasma, and a desired film is formed on the surface of the substrate S2 under this plasma.

[0007]

However, in such conventional plasma CVD, when a plurality of source gases for film formation are simultaneously introduced into a vacuum container and plasma is formed under a high frequency voltage of a certain magnitude, The decomposition rate differs depending on each gas. As a result, the efficiency of film formation is poor, and even if the applied voltage is increased to increase the film formation speed, the decomposition of gas, which is difficult to decompose, limits the film formation and saturates the film formation speed. However, there was a problem that the temperature reached or the composition of the film changed.

Therefore, according to the present invention, when a plurality of gases are used as the film-forming source gas in plasma CVD, the film-forming efficiency can be improved, and by increasing the applied voltage, the film-forming efficiency can be improved according to the voltage increase amount. An object of the present invention is to provide a plasma CVD method and apparatus capable of increasing the film speed and performing high-speed film formation without changing a predetermined film composition.

[0009]

In the plasma CVD method of the present invention for solving the above-mentioned problems, a film-forming gas is introduced into a vacuum container, and the gas is turned into plasma by applying a high-frequency voltage under a predetermined vacuum state, In plasma CVD in which a target film is formed on the surface of a substrate to be filmed under the plasma, a plurality of gases are introduced as film forming gases, and high-frequency voltages having different amplitudes are sequentially applied. The feature is that the application is repeated.

It is desirable that the smallest of the high-frequency voltages having a magnitude suitable for plasma generation of each gas is a magnitude capable of converting at least one gas into plasma and maintaining the plasma. When the high frequency voltage is repeatedly applied, the modulation frequency of the repeating unit is almost 1
It is desirable to be in the range of Hz to 100 KHz,
When the frequency is less than 1 Hz, the frequency of the change in the amplitude of the high frequency voltage is low, so that it is not possible to decompose a plurality of gases in parallel. When the frequency is higher than 100 KHz, the frequency of the change in the amplitude is high, and therefore it depends on each applied voltage. Gas is not fully decomposed.

Further, the amplitude of each high frequency voltage applied repeatedly and their time distribution (Duty) (for example, a high frequency voltage of amplitude a is applied for A time, and then a high frequency voltage of amplitude b is applied for B time. If the high frequency voltage is repeatedly applied in this order, A / A +
For B and amplitude b, the value of B / A + B) may be various values depending on the type of the source gas, the desired film composition, and the like. Generally speaking, the Dty ratio will be selected from, but not limited to, the range of 1-99%.

Further, in the plasma CVD apparatus of the present invention for solving the above-mentioned problems, a gas for film formation is introduced into a vacuum container, and the gas is turned into plasma by applying a high frequency voltage by a voltage applying means under a predetermined vacuum state, In a plasma CVD apparatus for forming a target film on the surface of a substrate to be filmed under the plasma, the voltage applying means sequentially switches the applied voltage to a high frequency voltage having different amplitudes, and repeats the voltage switching. Means, and means for controlling the input timing of each high-frequency voltage switched by the switching means.

[0013]

According to the method and apparatus of the present invention, plasma CVD
In the case of using a plurality of gases as raw material gases, a high-frequency voltage of a magnitude suitable for plasma conversion of each gas is sequentially applied, and by repeating this, when a voltage with a small amplitude is applied, it is easily decomposed at the low voltage. The gas is mainly decomposed, and when a voltage with a large amplitude is applied, a gas that is difficult to decompose at a low voltage is decomposed, or a gas that is easily decomposed at the high voltage is mainly decomposed. As a result, the film formation is efficiently performed by controlling the amplitude of each high-frequency voltage repeatedly applied and the time distribution (Duty) thereof according to the kind of the source gas and the desired film composition.

Further, by increasing the magnitude of the applied voltage, the film forming speed is increased according to the amount of voltage increase, and high speed film forming is performed without changing the predetermined film composition.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. As a typical example thereof, a parallel plate type plasma CVD apparatus shown in FIG. 1 and a film forming method by the apparatus will be described. The plasma CVD apparatus is provided with a high frequency amplifier 8 and a function generator (arbitrary waveform generator) 9 instead of the high frequency power source 5 in the conventional example shown in FIG. 4, and these are connected to a matching box 4. The waveform formed by the arbitrary waveform generator 9 is amplified by the amplifier 8 and supplied to the electrode 3 via the matching box 4. The function generator (arbitrary waveform generator) 9 can be used to turn on and off the high-frequency voltage application, set and control the on-time, off-time, and control the magnitude of the applied power.

The other structure is the same as that of the conventional device shown in FIG. According to this parallel plate type plasma CVD apparatus, the film-forming target substrate S1 is placed on the substrate holder 2 in the vacuum container 1, the inside of the container 1 is brought to a predetermined vacuum degree by the operation of the exhaust device 6, and the gas is supplied. A film forming gas is introduced from the portion 7 through the gas supply holes of the nozzle 31 and the electrode plate 32. Further, the waveform formed by the function generator 9 is amplified and applied to the high-frequency electrode 3 by the amplifier 8, whereby the gas introduced is turned into plasma, and the substrate S is heated under this plasma.
A desired film is formed on one surface.

However, in this embodiment, a high-frequency voltage having a magnitude suitable for converting each source gas into plasma is sequentially switched by the function generator 9 and applied, and this is repeated. As a result, when a voltage with a small amplitude is applied, a gas that is easily decomposed at a low voltage is mainly decomposed, and when a voltage with a large amplitude is applied, a gas that is difficult to be decomposed at a low voltage is decomposed or is easily decomposed at the high voltage. The gas is mainly decomposed. As a result, the function generator 9 controls the size of each high-frequency voltage to be repeatedly applied and the time distribution (Duty) thereof according to the kind of the source gas and the desired composition of the film, thereby forming the film efficiently. be able to.

Further, when the applied voltage is increased, the film forming speed is increased according to the amount of increase in voltage (see FIG. 2), and high speed film forming is performed without changing the predetermined film composition. here,
It is desirable that the smallest one of the high-frequency voltages is of a size capable of converting at least one kind of gas into plasma and maintaining the plasma, and the modulation frequency of the repeating unit of voltage application is within a range of approximately 1 Hz to 100 KHz. Therefore, it is possible to form the film more efficiently.

FIG. 3B shows the voltage application pattern.
The pattern shown in can be illustrated. This is because while the pattern according to the conventional example shown in FIG. 3A is continuously applied with a constant frequency and amplitude, two types of high-frequency voltages with the same frequency but different amplitudes have a duty of 50% (t). /
They are applied alternately in T). Next, a specific example of forming a silicon nitride (SiNx) film by the parallel plate type plasma CVD apparatus shown in FIG. 1 will be described.・ Film forming conditions Raw material gas SiH ₄ : 50 sccm NH ₃ : 200 sccm Film forming temperature 250 ° C. Film forming gas pressure 1.0 Torr Applied voltage 20 V (frequency 13.56 MH)
z) 100 V (frequency 13.56 MHz) Duty 50% Modulation frequency 1 KHz-Film forming speed 1000 Å / min Further, using the conventional apparatus shown in FIG. 4, a high frequency voltage of 100 V and a frequency of 13.56 MHz was used under the same conditions as in the above embodiment. When a voltage was continuously applied to form a SiNx film, the film formation rate was 700 Å / min.

In the film formation according to the example, compared with the film formation according to the comparative example, the film formation rate could be improved without increasing the applied voltage.

[0021]

According to the method and apparatus of the present invention, when a plurality of gases are used as the film-forming raw material gas in plasma CVD, the amplitude of each high-frequency voltage to be applied and their D
By controlling the duty, a film having a desired composition can be efficiently obtained. Further, by increasing the applied voltage, the film formation speed can be increased according to the amount of voltage increase,
High-speed film formation can be performed without changing the predetermined film composition.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a plasma CVD apparatus that is an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a peak voltage of an applied voltage and a film forming rate in the present invention and a conventional example.

FIG. 3A is a diagram showing a voltage application pattern according to a conventional example, and FIG. 3B is a diagram showing an example of a voltage application pattern according to the present invention.

FIG. 4 is a diagram showing a schematic configuration of a plasma CVD apparatus according to a conventional example.

[Explanation of symbols]

 1 Vacuum Container 2 Substrate Holder 3 High Frequency Electrode 31 Gas Nozzle 32 Perforated Electrode Plate 4 Matching Box 5 High Frequency Power Supply 6 Exhaust Device 7 Gas Supply Section 8 High Frequency Amplifier 9 Function Generator (Arbitrary Waveform Generator) S1, S2 Substrate

Claims (4)

[Claims] 1. A film-forming gas is introduced into a vacuum container, and the gas is turned into plasma by applying a high-frequency voltage under a predetermined vacuum condition, and a target film is formed on the surface of a film-forming target under the plasma. In the plasma CVD method described above, a plurality of gases are introduced as film forming gases, high-frequency voltages having different amplitudes are sequentially applied, and the voltage application is repeated. 2. The plasma CVD method according to claim 1, wherein among the high-frequency voltages having different amplitudes, the smallest one has a magnitude capable of converting at least one gas into plasma and maintaining the plasma. . 3. The plasma CVD method according to claim 1, wherein when the high frequency voltages having different amplitudes are sequentially applied and the repetition is repeated, the modulation frequency of the repeating unit is within the range of about 1 Hz to 100 KHz. . 4. A film forming gas is introduced into a vacuum container, and the gas is turned into plasma by applying a high frequency voltage by a voltage applying means under a predetermined vacuum state. In the plasma CVD apparatus for forming a film to be formed, the voltage applying unit sequentially switches the applied voltage to a high frequency voltage having different amplitudes, a voltage switching unit that repeats this, and a high frequency voltage that is switched by the switching unit. A plasma CVD apparatus including a means for controlling a charging timing.