JPH0643632B2 - Deposited film forming apparatus by plasma CVD method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a deposited film on a substrate, especially a functional film, particularly a semiconductor device, a photosensitive device for electrophotography, a line sensor for image input, and an imaging device. , Plasma CV suitable for forming non-single crystalline deposition film such as amorphous or polycrystalline used for photovoltaic devices
Regarding the device by D method.

[Description of Prior Art]

Conventionally, semiconductor devices, photosensitive devices for electrophotography,
As element members used for image input line sensors, imaging devices, photovoltaic elements, etc., amorphous silicon, such as hydrogen or / and halogen (for example, fluorine, chlorine, etc.) compensated amorphous silicon (hereinafter referred to as “a- Si
(H, X) ”. ) Membranes, etc. have been proposed, some of which have been put to practical use. Along with such a-Si (H, X) films, some methods for forming such a-Si (H, X) films and devices for implementing them have also been proposed, such as vacuum vapor deposition and ion plating. Methods, so-called CVD method, plasma CVD method, optical CVD method, and the like. Among them, the plasma CVD method is put to practical use as an optimal method, and is generally widely used.

By the way, in the plasma CVD method, high-frequency or microwave energy is used to excite (deradicalize) a deposited film forming gas in the vicinity of the substrate surface to cause a chemical interaction, and the film is deposited on the substrate surface. Where it is said that it is called, there is a fifth device
The device shown in FIGS. 6 to 6 has been proposed.

That is, FIG. 5 is a schematic cross-sectional view of a conventional deposited film forming apparatus by the plasma CVD method, and FIG. 6 is a schematic cross-sectional view of the apparatus shown in FIG.

In the figure, A indicates the entire apparatus having a reaction chamber B which is hermetically formed by a side wall 11, a bottom wall 11 'and a lid 11a. Reference numeral 13 denotes a cylinder made of a conductive material such as metal, which has a plurality of perforations 13a, 13a, ... On its side wall, and the cylinder is erected at the center in the reaction chamber B with its bottom fixed to the central axis. And its bottom is connected to the exhaust system 14 provided outside. , 12, 12 ... Cylindrical bases mounted on the base holding means, which has a heating means 17 built therein and is mechanically connected to the rotating means 16 at the bottom thereof, are electrically conductive as shown in FIG. Centered around the flexible cylinder 13, they are arranged in an array on the same circumference with a predetermined interval. The bases 12, 12, ... Are electrically grounded 19 together with the side wall 11 so that they are held at the same potential. Reference numeral 15 is a gas introduction system, and the source gas is supplied into the reaction chamber B via a pipe means. Reference numeral 18 denotes a high-frequency power generation source, one end of which is electrically connected to the conductive cylinder 13 and the other end of which is electrically grounded 19. The electrically conductive cylinder 13 and the cylindrical substrates 12, 12, ... Work as the cathode electrode and the latter as the anode electrode during the operation of the device.

In the film forming operation by the conventional deposited film forming apparatus by the plasma CVD method described above, for example, a case of forming an a-Si (H, X) deposited film will be described. The cylindrical substrate 12 is mounted on each substrate holding means. Then, the exhaust system 14 is operated to bring the inside of the reaction chamber B into a vacuum state, and each of the cylindrical substrates 12, 12, ... Is heated to a predetermined temperature by the respective heating means 17, and the gas is introduced through the gas introduction system 15. Silane gas, which is a raw material gas, is introduced into the reaction chamber B, and at the same time, the high frequency power generation source 18 is energized to apply the high frequency power to the conductive cylinder 13, and the rotating mechanisms 16, 16, ... It is performed by rotating the substrates 12, 12, .... By this operation, plasma discharge is generated between the cylinder 13 acting as the cathode electrode and the cylindrical substrate 12, 12, ... Acting as the anode electrode,
This excites and decomposes the silane gas and causes a chemical interaction between them to deposit an a-Si (H, X) 2 film on each surface of the substrate.

Although the conventional deposition film forming apparatus by the plasma CVD method shown in FIGS. 5 to 6 is adopted as a suitable apparatus, there are some problems in operation.

That is, when a high frequency voltage is applied to the cylinder 13, the reaction chamber B
The gas molecules of the source gas (for example, silane gas) introduced into the inside are excited and decomposed into plasma, and become electrons, ion particles, neutral radical particles and the like. These particles fly near the surfaces of the rotating cylindrical substrates 12, 12, ... And form a deposited film. Here, it is the neutral radical particles that mainly contribute to the formation of the deposited film, but many electrons and ion particles are present in the plasma at the same time. The ionic particles collide with the deposited film during or after the formation, and as a result, structural defects such as dangling bonds and voids are created, and the quality of the formed film deteriorates. This has been a serious problem in forming a deposited film of high quality and uniform characteristics.

[Object of the Invention]

The present invention overcomes the problems in the conventional devices as described above, and is a semiconductor device, an electrophotographic photosensitive device, an image input line sensor, an imaging device, a photovoltaic device, various other electronic devices, optical devices, etc. The deposited film as an element member used for plasma CVD
The object of the present invention is to provide a device that can be stably formed by the method.

That is, the main object of the present invention is a plasma CVD method capable of forming a deposited film having good and excellent desired characteristics in a steady and stable manner by eliminating damage to the deposited film due to plasma impact and making it uniform and homogeneous. To provide a deposited film forming apparatus.

Another object of the present invention is plasma CVD capable of easily controlling the film thickness and film quality of a deposited film to be formed and forming a deposited film having a uniform film thickness distribution and a uniform film quality. It is to provide an apparatus for forming a deposited film by the method.

[Constitution and effect of the invention]

The present inventor has found that the conventional plasma CVD shown in FIGS.
As a result of earnest studies to overcome the above-mentioned problems of the deposited film forming apparatus by the method and achieve the above-mentioned object,
When the charged particle collecting electrode is provided in the central portion of the conventional device, it is possible to solve the above-mentioned problems of the conventional device, obtain the knowledge that the above-mentioned object of the present invention can be achieved, and complete the present invention. It arrived.

That is, the apparatus of the present invention, on the substrate installed in the reaction chamber,
In a deposited film forming apparatus by a plasma CVD method for forming a deposited film using high frequency or microwave, an electrode for collecting charged particles is provided at the center of the reaction chamber, and concentric circles are formed around the electrode. It is characterized in that a rotatable base mounting means is provided.

Thus, in the apparatus of the present invention, charged particles undesired for film formation are trapped by the collection electrode, so that there is no opportunity for such charged particles to reach the surface of the substrate, and accordingly, during or after they are formed. Since it does not collide with the deposited film and cause structural defects in the deposited film, and the uniformity of the electric field intensity distribution of the radiated high frequency or microwave in the vicinity of the substrate is promoted. In comparison, the deposition rate can be significantly improved, and a deposited film product that is excellent in terms of quality, thickness, and electrical, optical, and photoconductive characteristics can be stably mass-produced at all times.

The source gas used for forming a deposited film by the apparatus of the present invention is of a type that excites species by high frequency or microwave energy and chemically interacts to form an initial deposited film on the substrate surface. Any one can be used if it exists, but for example, when forming an a-Si (H, X) film, specifically, hydrogen, halogen, or hydrocarbon is added to silicon. It is possible to use those in the gas state such as bonded silanes and halogenated silanes, or those in which gas that can be easily gasified is gasified.
One of these source gases may be used, or 2
You may use together 1 or more types.

In addition, these raw material gases may be diluted with an inert gas such as He or Ar before use. Furthermore, the a-Si (H, X) film can be doped with a P-type impurity element or an n-type impurity element, and the source gas containing these impurity elements as constituents can be used alone or as described above. It can be introduced into the reaction chamber by mixing with the raw material gas or / and the diluting gas.

The substrate may be conductive, semi-conductive, or electrically insulating, and specific examples thereof include metals, ceramics, and glass. The substrate temperature during the film forming operation is not particularly limited, but it is generally in the range of 30 to 450 ° C, and preferably 50 to 350 ° C.

Further, in forming the deposited film, the pressure in the reaction chamber is set to 5 × 10 ⁻⁶ Torr or less, preferably 1 × 10 ⁻⁶ Torr or less before introducing the source gas, and when the source gas is introduced. The pressure in the reaction chamber is 1 × 10 ^-2 to 1 Torr, preferably 5 × 10 ^-1.
It is desirable to set it to 1 Torr.

Incidentally, the deposited film formation by the apparatus of the present invention is usually introduced into the reaction chamber without pretreatment (excitation seeding) of the source gas as described above, where the seeding is excited by high-frequency or microwave energy, Although it is carried out by causing a chemical interaction, when two or more kinds of raw material gases are used, it is also possible to pre-excite one of them and then introduce them into the reaction chamber.

Hereinafter, the apparatus for forming a deposited film by the plasma CVD method of the present invention will be described in more detail with reference to the embodiments shown in FIGS. 1 to 4, but the apparatus is not limited thereto.

1 and 2 are schematic sectional views of a deposited film forming apparatus by the plasma CVD method of the present invention, and FIGS. 3 and 4 are transverse cross sections taken along lines II-II and III-III of these apparatuses, respectively. It is a schematic diagram.

In FIG. 1, A shows the whole deposition film forming apparatus by the plasma CVD method of the present invention which has a reaction chamber B which is hermetically formed by a side wall 1, a bottom wall 1 ′ and a detachable lid part 2. Three
Is a dielectric window, through which high frequency or microwaves propagated from the high frequency or microwave oscillator 32 through the waveguide 31 are radiated into the reaction chamber B. 4 is
As shown in FIG. 3, it is an exhaust gap portion that surrounds the dielectric window 3 in a circular axis, is insulated from the waveguide 31, and is open in the reaction chamber B. The gap portion 4 is an exhaust device. 42 is in communication with a conduit 41 which is connected to 42 via a valve 43. Reference numeral 5 denotes an inlet for introducing the raw material gas into the reaction chamber B, which is connected to a gas supply source 51 via a valve 52. 7
Is an electrode for collecting charged particles made of a conductive material such as aluminum or stainless steel, and its tip is located in the upper space of the dielectric window 3 at its center position, that is, at the center of the reaction chamber B. As described above, it is installed in the space of the reaction chamber B via the insulating portion 71 detachably provided in the central portion of the lid portion 2, and the other end is connected to the DC power source 72 provided outside. It is connected via 73. 61
Is a means for holding the cylindrical substrate 6 containing the heating means 62, and as shown in FIG.
A plurality of charged particle collecting electrodes 7 are arranged around the same, and a plurality of them are coaxially arranged on the same circumference with a predetermined interval (at least 1 mm or more). The substrate holding means 61, 61, ... On which the cylindrical substrate is placed are supported by supporting legs 63, 63 ,.
It is mechanically connected to 4, 64, ... and can rotate in either left or right direction. The supporting legs 63, 63, ... Are electrically grounded 8 together with the side wall 1 so that the same person is kept at the same potential.

In the deposited film forming apparatus A by the plasma CVD method of the present invention shown in FIGS. 1 and 3 of the above description, a high frequency or The microwave is radiated to induce plasma discharge, which excites and decomposes the raw material gas. At that time, charged particles which are not preferable for film formation are attracted to the collecting electrode and are discharged by the exhaust device 42. Neutral radical particles, etc. that are generated by the exhaust action and are discharged from the gap portion 4 while contributing to film formation, for example, when the source gas is SiH ₄ , Si ^* , SiH ^* , SiH ₂ ^* is a cylindrical substrate 6, which is rotating in the direction of the side wall of the reaction chamber B,
The action of 6, ... also progresses together and is uniformly dispersed in the vicinity of the surface of each substrate, so that the reaction with the substrate surface, the mutual reaction, the reaction with the specific component in the introduced raw material gas, etc. Through this, the deposited film is formed by uniformly and uniformly depositing on each substrate surface. Therefore, in the device of the present invention,
The problems of structural defects and contamination of impurities due to collision of electrons and ionic particles found in conventional devices do not occur, and it is excellent in all in terms of quality, thickness, and electrical, optical, and photoconductive properties. The desired deposited film product can always be obtained stably and efficiently.

The apparatus shown in FIGS. 2 and 4 is similar to that shown in FIGS.
This is a modification of the apparatus shown in the figure, and this apparatus is also a preferred embodiment of the deposited film forming apparatus by the plasma CVD method of the present invention.

In the apparatus shown in FIGS. 2 and 4, the exhaust port has an opening 4 in the side wall 1 of the reaction chamber B, and the dielectric window 3 for radiating high frequency or microwave into the reaction chamber B is A high-frequency or microwave waveguide communicating with a high-frequency or microwave oscillator 32 is formed by notching the central portion of the bottom wall of the reaction chamber and hermetically fitting the cut-out portion.
301 is fixed. Then, the charged particle collecting electrode 701
Is closed at the tip as shown in FIG.
A tube having 1 ', 701', ... Is provided, and at the other end of the electrode, a raw material gas supply pipe is provided which is provided with a valve 52 and communicates with a raw material gas supply source 51. The electrode 701 is fixed to the penetrating portion of the lid 2 by hermetically sealing it 702, and the member of the electrode is electrically connected by a DC power source 72 provided outside and a connecting means 73. Has been done.

In the deposited film forming apparatus A by the plasma CVD method of the present invention illustrated in FIGS. 2 and 4 described above, the high frequency or the microwave is radiated into the reaction chamber B through the dielectric window 3. A plasma discharge is triggered. And
The raw material gas released in the direction of the arrow shown in the figure through the holes 701 ', 701', ... Of the charged particle electrode 701 is excited and decomposed by the action of the induced plasma discharge, which is preferable for the film formation at that time. Uncharged particles are attracted along the wall surface of the member of the collection electrode 701, while neutral radical particles that contribute to film formation, such as when the source gas is SiH ₄ , S
i ^* , SiH ^* , SiH ₂ ^*, etc. are the action of the raw material gas stream horizontally discharged toward the side wall of the reaction chamber B through the holes 701 ′, 701 ′, ... 6, 6 and so on, and further the exhaust action by the exhaust device, progresses in the direction of the side wall of the reaction chamber B and is uniformly dispersed in the vicinity of the respective substrate surfaces, so that the reaction with the substrate surfaces and the mutual reaction Through the reaction, the reaction with the specific component in the introduced raw material gas, etc., to uniformly and evenly deposit on the surface of each substrate, and the desired deposition is performed in the same manner as in the apparatus shown in FIGS. 1 and 3. A film is formed.

Hereinafter, a method of operating the deposited film forming apparatus by the plasma CVD method of the present invention to form a deposited film will be described with reference to examples, but the following examples are not limited to the operation of the apparatus. Absent.

Example A photoconductive deposited film was formed on the surface of an Al cylindrical substrate by operating the deposited film forming apparatus according to the present invention shown in FIGS. 1 and 3 according to the present invention.

That is, the substrate holding means arranged with a gap of 5 mm.
The Al thin plate cylindrical substrates 6, 6, ... Are placed on 61, 61, ..., The exhaust device 42 is operated in the reaction chamber B, and the valve 43 is adjusted to set about 10
^-5 Torr vacuum level. Then, the heating means 62 kept the substrate temperature at about 300 ° C. Next, SiH ₄ which is a raw material gas for forming the deposited film was diluted with hydrogen gas and introduced into the reaction chamber A through the inlet 5. When the gas flow rate is stable, the exhaust valve 43 is adjusted to adjust the internal pressure of the reaction chamber B to about 2 × 10 ^-3.
Torr. When the internal pressure becomes constant, rotation of the substrate holding means 61, 61, ... Is started, then a negative DC voltage is applied to the electrode 7, and a microwave of 2.45 GHz is applied to the reaction chamber B.
Radiated in. In this state, hold for 20 minutes to
A deposited film of a-Si (H, X) was formed on the surface. After that, when the substrates were cooled to a predetermined temperature, they were taken out of the system and tested. As a result, a uniform and uniform deposited film was formed on all the substrates, and they all had various characteristics. It was.

[Brief description of drawings]

1 and 2 are schematic sectional views of a deposited film forming apparatus by the plasma CVD method of the present invention, and FIGS. 3 and 4 are transverse cross sections taken along lines II-II and III-III of these apparatuses, respectively. It is a schematic diagram. FIG. 5 is a schematic sectional view of a conventional deposited film forming apparatus by the plasma CVD method, and FIG.
1 is a schematic cross-sectional view taken along line I. 1 to 4, 1 ... Side wall, 1 '... Bottom wall, 2 ... Lid part, 3 ... Dielectric window, 31 ... Waveguide, 32 ... High frequency or microwave oscillator, 4 ... Exhaust gap part, 41 ... Conduit, 42 ... Exhaust device, 43 ... Valve, 5 ... Raw material gas inlet, 51
...... Source gas supply source, 52 …… Valve, 6 …… Cylindrical substrate, 61 …… Substrate holding means, 62 …… Heating means, 63 ……
... Support legs, 64 ... rotational driving means, 7 ... charged particle collection electrode, 71 ... insulating part, 72 ... DC power supply, 73 ... lead wire, A ... entire apparatus, B ... reaction chamber, 301 ... Waveguide, 50 ... Piping joint, 701 ... Charged particle collecting electrode, 7
01 '... perforation, 702 ... insulation part. In FIGS. 1 and 2, 11 ... Side wall, 11 '... Bottom wall, 11a ... Lid, 12 ...
Cylindrical base, 13 ... Metal cylinder, 13a ... Perforation, 14 ...
Exhaust system, 15 ... Gas introduction system, 16 ... Rotation mechanism, 17
...... Heating means, 18 …… High frequency power source, 19 …… Ground.

Claims (1)

[Claims] 1. Plasma CVD for forming a deposited film on a substrate placed in a reaction chamber by using high frequency or microwave.
In the deposited film forming apparatus by the method, an electrode for collecting charged particles is provided at the center of the reaction chamber, and a substrate setting means is provided which is rotatable about the electrode in a coaxial circumference. An apparatus for forming a deposited film by the plasma CVD method, which is characterized by: