JPS61267315A - Plasma cvd device - Google Patents

Abstract

PURPOSE:To efficiently manufacture the film having excellent characteristics by a method wherein at least reactive gas of one or more kinds is introduced into a glow discharge region through the intermediary of a high density plasma region, and on the other hand, another reactive gas containing at least one or more kinds is introduced into the glow discharge region without having the intermediary of the high density plasma region. CONSTITUTION:Of a plurality of kinds of reactive gas to be introduced, one or more kinds of gas of low efficiency of activation is introduced into a glow discharge region 10 from the first gas introducing pipe 4 through the intermediary of a high density plasma region 8. On the other hand, other kind of reactive gas is directly introduced into the glow discharge region 10 through the second gas introducing pipe 5. As the low activation gas passes through the high density plasma region 8 as above-mentioned, the activation of gas is accelerated, and on the other hand, the gas which does not pass trough the high density plasma region is not excessively decomposed by plasma. As a result, the activation and the decompositional efficiency of a plurality of kinds of reactive gas can be controlled properly, and the film of good quality can be formed at a high speed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a plasma CVD apparatus configured to provide stable film forming characteristics.

(Prior Art) Plasma CVD apparatuses are currently widely used for producing inorganic films such as amorphous silicon films and silicon nitride films, and plasma polymerized films of organic substances.

The apparatus generally includes a vacuum vessel which is a reaction vessel, a vacuum evacuation device, a glow discharge generating means, and a reaction gas introducing means. The film forming process using this apparatus is as follows.

That is, while a reaction gas is introduced into the vacuum container by the reaction gas introduction means, a vacuum is evacuated at the same time to maintain a reduced pressure state, and direct current is applied to the internal electrode installed in the vacuum chamber or the external electrode installed outside the vacuum container. Glow discharge is performed by applying an alternating current or high frequency voltage. This glow discharge activates the reaction gas introduced into the vacuum container,
A film is formed on the surface of the substrate by the generated active species.

The features of this device are: (1) It can form a film at a relatively low temperature. (2) Films with various different properties can be produced simply by switching the type of reaction gas.

(3) A uniform film can be formed over a large area compared to other vacuum film forming methods such as vapor deposition and ion blating. (4) It is possible to produce films with unique functions and physical properties that cannot be obtained with other equipment such as sputtering equipment and ion blating equipment.

When forming a film using a plasma CVD apparatus having the above characteristics, a plurality of types of gases are often simultaneously introduced as reaction gases.

For example, when creating an amorphous silicon film, a gas such as monosilane, disilane, trisilane, silicon tetrafluoride, etc. is used as a silicon source, and a gas such as diborane, phosphine, arsine, etc. is used for doping. Further, for the purpose of controlling the band gap, a hydrocarbon such as methane or a gas such as nitrogen, germane, Sn H4, etc. is used, and furthermore, a gas such as hydrogen, argon, helium, etc. is used for dilution or reaction control.

In addition, when creating a silicon nitride film, a gas such as monosilane, disilane, trisilane, silicon tetrafluoride, etc. is used as a silicon source, and nitrogen gas, ammonia, hydrazine, nitrogen trifluoride, etc. is used as a nitrogen source.
Furthermore, gases such as argon, helium, hydrogen, nitrogen, etc. are used for dilution or reaction control.

In most cases, two or more types of the above gases are used as a mixture depending on the purpose of film formation.

(Problems to be Solved by the Present Invention) In conventional plasma CVD apparatuses, a method is generally adopted in which a mixed gas is introduced into a uniform glow discharge region and activated and reacted. At this time, the degree of activation of the gas by the plasma may vary depending on the type of gas.

Therefore, some gases have poor activation efficiency and are exhausted without much reaction, and some other gases are excessively decomposed by plasma, slowing down the film formation rate. Phenomena such as increased generation of powder occur, making it impossible to form an efficient film and resulting in failure to obtain the desired film characteristics.

SUMMARY OF THE INVENTION An object of the present invention is to provide a plasma CVD apparatus that eliminates the above-mentioned conventional drawbacks and efficiently forms films with good characteristics.

(Means for Solving the Problem) The present invention comprises a vacuum container, evacuation means, and reactive gas introduction means, and forms a film on a substrate surface by decomposing or activating the reactive gas by glow discharge under reduced pressure. In a plasma CVD apparatus, at least a part of a high-density plasma region is provided in a glow discharge region, and a plurality of types of gases are used as the reactive gas, and at least one of the reactive gases is used as the reactive gas. The reactant gas is introduced into the glow discharge region through the high-density plasma region, while at least one other type of reactive gas is introduced into the glow discharge region without passing through the high-density plasma region.

(Embodiment of the present invention) FIG. 1 shows an embodiment in which the present invention is applied to a commonly used parallel plate type plasma CVD apparatus. This will be explained below based on the drawings.

1 is a vacuum container, and the vacuum container 1 includes an oil diffusion pump,
It is evacuated by an exhaust system (not shown) such as a turbo pump, Roots blower pump, or oil rotary pump. A substrate holder 6 having a built-in heater 9 is installed in the vacuum container 1, and a substrate 7 is placed on this substrate holder 6. The substrate holder 6 is heated to about 100'C to 400C by the heater 9.

A voltage applying electrode 3 is installed inside the vacuum container 1 facing the substrate holder 6 . A glow discharge 10 is generated between the voltage application electrode 3 and the substrate holder 6 by applying a direct current, an alternating current, or a high frequency voltage generated from a power source 12 to the voltage application electrode 3 .

In this figure, the device is arranged so that the voltage application electrode 3 is on top and the substrate holder 6 is on the bottom, but the present invention can be applied even if the positional relationship is upside down or both are arranged vertically. The purpose of is achieved.

By providing the four parts 11- on the side of the voltage application electrode 3 facing the substrate holder 6, a high-density plasma region 8 is generated in a part of the glow discharge region]-.

The dimensions of the recess for generating the high-density plasma region 8]-1 satisfy the condition that plasma with higher density than the plasma generated between the voltage application electrode 3 and the substrate holder 6 is generated in the recess 11. It is arbitrary and is not necessarily limited. Conditions for generating this high-density plasma 8 vary depending on the type of gas, the pressure inside the container, and the discharge power.

However, in the experiment, the conditions commonly used in plasma CVD were used, that is, monosilane and nitrogen were used as the reaction gas, the pressure was 6 Pa to 200 Pa, and the discharge power was i.
When discharge was performed in the range of oow to 2kW, the diameter was φ2ITIIl to φ40mm, and the depth was 0.5 to 1 times the diameter.
Good results were obtained at around -0 times.

Further, the shape is not limited to a cylindrical shape, and the high-density plasma region 8 is similarly generated even if the shape is a slit shape or a honeycomb shape. By providing one or more four portions 11 on the voltage application electrode 3, high-density plasma regions 8 are generated corresponding to the number of the four portions 11.

The material of the surface of the recess 11 forming the high-density plasma region 8 may be the same metal as that of the voltage application electrode 3, but in order to avoid contamination of impurities into the produced film, it is preferable to use silicon, quartz, nitride, etc. A material with low impurity release efficiency, such as silicon or alumina, can be used.

Two gas introduction pipes for introducing reaction gases are connected to the vacuum vessel 1. Among these, the first gas introduction tube 4 is formed so as to penetrate through the inside of the voltage application electrode 3 and introduce a reactive gas into the glow discharge region 10 via the high-density plasma region 8 . On the other hand, the second gas introduction pipe 5 connects the voltage application electrode 3
It is formed so that the reactive gas is introduced into the glow discharge region 10 without passing through the high-density plasma region 8 by penetrating the inside thereof.

If the second gas introduction pipe 5 and the recess 11 and the first gas introduction pipe 4 opening into the recess 11 are one or more each, the high-density plasma region 8 is basically generated, and the high-density plasma region 8 Although the purpose of separating the gas introduced through the high-density plasma region 8 from the gas introduced without passing through the high-density plasma region 8 can be achieved, in order to uniformly form a film on the substrate 7, the number of each of them is large. It is preferable.

Further, the diameter of the opening 5a of the second gas introduction pipe 5 that opens into the vacuum vessel 1 needs to be sufficiently small so that high-density plasma is not generated at the opening.

Normally, if the diameter of the opening 5a is less than φ2nn, generation of high-density plasma can be prevented.

Among the plurality of types of reactive gases introduced, one or more types of gas with poor activation efficiency are introduced from the first gas introduction pipe 4 into the glow discharge region 10 via the high-density plasma region 8. On the other hand, on the other hand, another type of reaction gas is directly introduced into the glow discharge area 1o through the second gas introduction pipe 5.
to be introduced.

As mentioned above, since the gas with poor activation efficiency passes through the high-density plasma region 8, the activation of the gas is promoted, while the gas that does not pass through the high-density plasma region is not excessively decomposed by the plasma.

A silicon nitride film was created using a plasma CVD apparatus according to the present invention. That is, nitrogen gas is introduced from the first gas introduction pipe 4, and silane gas is introduced from the second gas introduction pipe 5. When a high frequency power of 13.56 MHz was applied to the voltage application electrode 3, the film formation rate was about 300 layers/min when normal parallel plate electrodes were used, which was more than 1000 layers/min compared to Lunoni. A high film speed was obtained, and a silicon nitride film of good quality could be obtained. At the same time, the generation of powder was also reduced.

This is because nitrogen gas, which is difficult to activate and decompose compared to silane gas, passes through the high-density plasma region 8 to be easily activated and decomposed, so that the decomposition balance with the silane gas that is directly introduced into the glow discharge region 10 is maintained. This is thought to be due to improved performance.

Furthermore, in the case of such a glow discharge, the plasma is concentrated in the high-density plasma region 8, so that even with the same high-frequency power, the plasma density on the surface of the substrate 7 is weaker than that of a normal parallel plate electrode.

Therefore, it is expected that damage to the substrate 7 caused by charged particles will be reduced.

When producing amorphous silicon using the apparatus according to the present invention in the same manner as described above, for example, for N-type amorphous silicon,
A mixed gas of hydrogen and phosphine is introduced from the first gas introduction pipe 4, and silane gas is introduced from the second gas introduction pipe 5.

According to this method, the decomposition of phosphine was accelerated compared to normal parallel plate electrodes, and a film with high doping efficiency could be obtained.

(Effects of the Invention) As is clear from the above explanation, according to the present invention, it is possible to control the activation and decomposition efficiency of multiple types of reaction gases, so that a film with good quality can be formed at high speed. be able to.

[Brief explanation of the drawing]

Figure 1 shows a plasma CVD system showing an embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view of the device. 1-111 vacuum container, 2-111 exhaust port, 3-111 voltage application electrode, 4-111 first gas introduction tube, 5-111 second gas introduction tube, 8-1 11 High density plasma region, 10-
1--Glow discharge area.

Claims (2)

[Claims] (1) Vacuum container, evacuation means, glow discharge generating means,
In a plasma CVD apparatus that is equipped with a reactive gas introducing means and forms a film on a substrate surface by decomposing or activating the reactive gas by glow discharge under reduced pressure, at least one high-density plasma region is provided in the glow discharge region. and using a plurality of types of gas as the reactive gas, at least one of the reactive gases is introduced into the glow discharge region via the high-density plasma region, while at least one or more of the reactive gases is introduced into the glow discharge region via the high-density plasma region A plasma CVD apparatus characterized in that another reactive gas is introduced into the glow discharge region without passing through the high-density plasma region. (2) The above-mentioned patent is characterized in that a recess is provided on the surface facing the substrate holder of the voltage application electrode facing into the vacuum container, thereby forming a high-density plasma region within the recess. Plasma CV according to claim 1
D device.