JPH01257320A - Electron cyclotron resonance plasma chemical vapor deposition apparatus - Google Patents

Abstract

PURPOSE:To form a homogeneous film at high speed by a method wherein a mesh electrode used to accelerate an ion is placed in front of a substrate support stage in a reaction chamber and a screen electrode capable of reducing an influence by the mesh electrode by adjusting a potential is placed inside a plasma generation chamber in order to separate a control operation of a plasma state from a control operation of an ion speed. CONSTITUTION:This is An electron cyclotron resonance plasma CVD apparatus constituted in the following way: a plasma generation chamber 1 where a means to form a magnetic line of force is provided at the outside and into which microwaves are introduced is interlinked with a reaction chamber 2 which houses a support stage 7 of a substrate 10 on which a thin film is to be deposited; a plasma generated in the plasma generation chamber 1 is diffused to the direction of the magnetic line of force. In this apparatus the following are provided: a mesh electrode 11 which is situated on the side of the plasma generation chamber 1 ot the substrate support stage 7 and to which an arbitrary voltage can be applied; a screen electrode 12 which surrounds an inner wall of the plasma generation chamber 1, which is equipped with a slit parallel to a polarization plane of microwaves and to which an arbitrary voltage can be applied. By this setup, it is possible to enhance a film-formation speed without degrading the film quality.

Description

[Detailed description of the invention] [Industrial application field] The present invention ionizes neutral gas with microwave energy,
The present invention also relates to an electron cyclotron resonance plasma chemical vapor deposition apparatus (hereinafter referred to as an ECR plasma CVD apparatus) for depositing a thin film such as a semiconductor on a substrate using an electron cyclotone resonance plasma sustained by applying a static magnetic field and causing electrons to move in a cyclotron. .

[Conventional technology]

In BCR plasma, it is relatively easy to control the electron temperature, which is important for ionizing or dissociating source gas molecules and creating active species that deposit on the substrate, so it is possible to form high-quality thin films at high speed. It is. The ECR plasma CVD apparatus mainly consists of a plasma generation chamber 10, a reaction chamber 2, and an electromagnetic coil 3, as shown in FIG. A waveguide 4 is installed in the plasma generation chamber 1 to introduce microwaves.
is connected, and a window 5 made of mainly synthetic quartz or alumina plate is provided between the plasma generation chamber and the waveguide to maintain a vacuum and allow microwaves to easily pass through. There is. An electromagnetic coil 3 installed around the outer periphery of the plasma generation chamber 1 creates a magnetic field so that electrons resonate with the frequency of the microwave used. For example, when the frequency of the microwave is 2.45 GHz, the magnetic flux density satisfies the ECR condition. is 875G.

A plasma outlet 6 is provided on the wall separating the plasma generation chamber 1 and the reaction chamber 2 so that the generated plasma can diffuse into the reaction chamber 2.
Inside the reaction chamber 2, there is a substrate table 7 at a position opposite to the plasma outlet.A gas introduction pipe 8 and an exhaust port 9 are opened in the reaction chamber 2. The exhaust port 9 can be evacuated to 10-' Torr or less by a vacuum exhaust system.

When using this ECR plasma CVD apparatus to form a thin film of amorphous silicon (a-3ljH) on, for example, a Bacara substrate, the glass substrate 10 is first placed on the substrate stand 7 and sufficiently heated to an appropriate temperature. After that, while continuing to exhaust from the exhaust port 9 with the vacuum evacuation system, silane (SIH#) is introduced from the gas inlet port 8.

By introducing a raw material gas such as hydrogen (Ho), changing the exhaust capacity, and adjusting the gas flow rate, the pressure inside the reaction chamber 2 is controlled from several m Torr to several tens of ff1 Torr. The raw material gas is decomposed by the generation of ECR plasma due to the application of microwave power from the waveguide 4 and the action of the magnetic field from the electromagnet 3, and the ion radical species that form the decomposed film are scattered by the divergent magnetic field and are deposited on the substrate. A semiconductor thin film is formed on the surface.

[Problem to be solved by the invention]

Conventionally, when forming a film using such an ECR plasma apparatus, in order to form a film of good quality, the film formation speed had to be slowed down.

An object of the present invention is to provide an ECR plasma CVD apparatus that can improve the film formation rate without degrading the film quality.

[Means for Solving 11a] In order to solve the above problems, the present invention provides a plasma generation chamber which is equipped with an external magnetic field line forming means to which microwaves are guided;
In an ECR plasma CVD apparatus that is connected to a reaction chamber that accommodates a support for a substrate on which a thin film is to be deposited, and in which plasma generated in the plasma generation chamber is diffused in the direction of magnetic field lines, an arbitrary A mesh electrode that can apply a voltage of

[Effect]

As shown in FIG. 3, the present applicant has already patented the improvement of film quality or adjustment of film formation rate by providing a mesh electrode 11 in front of a substrate 10 whose potential can be freely controlled from the outside. An application has been filed. In this method, the film quality changes depending on the voltage applied to the mesh electrode 8i11. This is due to the following reason. FIG. 4 shows the relationship between the potential applied to the mesh electrode and the current flowing into the mesh electrode. The vertical axis is on a logarithmic scale, and can be roughly divided into three areas. The first is a region where the current changes by changing the potential, the second is the electronic current saturation region where the current is saturated by a high positive potential, and the third is the ionic current saturation region where the current is saturated by a relatively low negative potential. It is. In this way, the changes in the plasma potential vP on the mesh electrode potential center axis can be seen as follows: the mesh electrode potential is O, V +
, V z, V s, it becomes true M51. Point i% $52. −41 line 53° is indicated by two-dot chain line 54. 0
As shown in FIG. 4, the potentials V, V, and V correspond to a region where the current changes, an electron current saturation region, and an ionic current saturation region, respectively. In the case of zero bias, as shown by line 51, the plasma potential V at the plasma generation section, plasma dispersion section, and ion acceleration section has a slope that accelerates positive ions from a constant value, and is almost constant between the mesh electrode and the substrate. Become. ■ When , is applied, a potential gradient is created between the mesh electrode and the substrate to accelerate positive ions, as shown by &1152, and since it does not affect anything else, positive ions are accelerated without changing the plasma state. The film formation rate can be increased. However, if the mesh electrode potential is increased to V in order to form a film at a higher speed, the v2 of the plasma generation part changes as shown in wA53, making it impossible to obtain a film of the same quality. By covering the inner wall of the plasma generation chamber with a shielding electrode having a slit parallel to the plane of polarization of the microwave so that the microwave can pass through, and by making the potential of the shielding electrode variable, the potential of the plasma generation chamber can be adjusted so that the area in contact with the plasma is The wide shielding electrode allows for free control and reduces the influence of the mesh electrode, making it possible to maintain a constant generation rate of various radicals while accelerating positive ion radicals using the mesh electrode. Any l! ! A high quality film can be formed at high speed.

〔Example〕

FIG. 1 is a sectional view of an embodiment of the present invention, and FIG.

The same parts as in Fig. 3 are given the same reference numerals.The difference from the apparatus in Fig. 3 is that a shield electrode 12 is provided close to the inner wall of the plasma generation chamber 1, and an external voltage It is connected to a variable DC power supply 15. The side surface of the shielding electrode 12 is similar to the side wall of the plasma generation chamber, for example, in a cylindrical shape, but at least the surface facing the window 5 is provided with a slit 13 parallel to the polarization plane of the microwave, and the side surface facing the plasma outlet 6 is provided with a slit 13 parallel to the polarization plane of the microwave. In FIG. 6, the waveguide 4 is rectangular and has an opening 14 in the part where
The short side walls parallel to the plane of polarization of the microwave are shown in cross section perpendicular to the plane of the figure, and therefore the slots 13 are also perpendicular to the plane of the figure.

As an example of the operation of this device, the potential of the mesh electrode 11 connected to the external power source 16 and the potential of the shield electrode 12 connected to the external power source 15 are set to be the same O and V,,V.

Figure 6 shows how the plasma potential ■ changes when (2) becomes constant, and the same film can be effectively formed at high speed while the plasma generation state is kept constant. Further, by changing the potentials of the shield electrode 12 and the mesh electrode 11, the film formation rate can be controlled while maintaining different plasma states.

〔Effect of the invention〕

According to the present invention, a mesh electrode for accelerating ions is placed in front of the substrate support in the reaction chamber of ECR plasma CVDvtfi, and a shielding electrode is placed inside the plasma generation chamber to reduce the influence of the mesh electrode by adjusting the potential. This makes it possible to separate the control of the plasma state and the control of the ion velocity, making it possible to form films of the same quality at high speed, and in particular to develop new film properties for solar cells. It can be effectively used for forming semiconductor thin films.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of an embodiment of the present invention, Fig. 2 is a cross-sectional view of a conventional device, Fig. 3 is a cross-sectional view of a device equipped only with mesh electrodes, and Fig. 4 shows the potential of the mesh electrode and the mesh current. FIG. 5 is a diagram showing the relationship between the change in mesh potential and plasma potential distribution in the apparatus shown in FIG. 3, and FIG. 6 is a diagram showing the plasma potential distribution controlled in the apparatus according to the embodiment of the present invention. It is. 1; Plasma generation chamber, 2; Reaction chamber, 3: Electromagnetic coil, 4
Waveguide, 7: Substrate support, 8: Gas introduction pipe, 9: Exhaust pipe, 10: Substrate, lit mesh electrode, Fig. 1, Fig. 2] Figure 3, Fig. 4, Fig. D

Claims (1)

[Claims] (1) A plasma generation chamber that is equipped with an external magnetic field line forming means to which microwaves are guided is connected to a reaction chamber that accommodates a support for a substrate on which a thin film is to be deposited, and the plasma generated in the plasma generation chamber is directed in the direction of the magnetic field lines. In the plasma generation chamber side of the substrate support, a mesh electrode is placed on the side of the plasma generation chamber to which an arbitrary voltage can be applied, and a mesh electrode surrounds the inner wall of the plasma generation chamber.
An electron cyclotron resonance plasma chemical vapor deposition apparatus characterized by having a slit parallel to the polarization plane of microwaves and a shielding electrode to which an arbitrary potential can be applied.