JPH0590175A - Device and method for depositing film - Google Patents

Abstract

PURPOSE:To provide the title device and method for depositing high quality film at a high deposition rate causing less adherence of a film to the inner surface of a film formation chamber. CONSTITUTION:The title deposited film formation device wherein a film formation space 106 is evacuated by an exhaust system and reactive gas and microwave energy are introduced into the film formation space 106 to form a deposited film on a substrate 105 by the glow discharge excited by the introduced microwave energy is composed of a double-structure wall of the film formation chamber 101 comprising electrically insulated inner wall 109 and outer wall 110, and a means impressing the inner wall of the film formation chamber 101 with a voltage.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to deposited films, especially functional films, especially semiconductor devices, photosensitive devices for electrophotography,
The present invention relates to a deposited film forming apparatus and a deposited film forming method suitable for forming an amorphous or crystalline deposited film used for an image input line sensor, an imaging device, a photovoltaic element, and the like.

[0002]

2. Description of the Related Art Conventionally, amorphous silicon, for example, has been used as an element member for semiconductor devices, electrophotographic photoconductor device reimage input line sensors, imaging devices, photovoltaic devices, and various other electronic devices and optical devices. Deposition films for semiconductors and the like, which are composed of amorphous materials such as amorphous silicon compensated with hydrogen or / and halogen (for example, fluorine, chlorine, etc.), have been proposed, and some of them have been put to practical use.

It is known that such a deposited film is formed by a plasma CVD method. That is, the source gas is decomposed by direct current, high frequency or microwave glow discharge, and a thin film is formed on a substrate made of glass, quartz, heat resistant synthetic resin film, stainless steel, aluminum, etc. It is known to be formed, and various devices therefor have been proposed.

By the way, in recent years, a plasma CVD method using microwave glow discharge decomposition has attracted attention, and studies for industrial use have been made.

Then, such a known deposited film forming apparatus by the microwave plasma CVD method typically has an apparatus configuration shown in a schematic perspective view of FIG.

In FIG. 6, 201 is a reaction vessel,
It forms a vacuum tight structure that is shaped by the wall 209. Reference numeral 202 denotes a material capable of efficiently transmitting microwave power into the reaction container and maintaining vacuum airtightness, for example,
It is a dielectric window made of quartz glass, alumina ceramics, or the like. Reference numeral 203 denotes a microwave transmission unit, which is mainly composed of a metallic waveguide, and is connected to a microwave power source (not shown) via a matching device isolator.
An exhaust pipe 204 has one end opening into the vacuum container 201 and the other end communicating with an exhaust device (not shown). 205
Is a substrate for forming a deposited film, and 206 is a film forming space. Reference numeral 207 is a base holder. Formation of a deposited film by such a conventional deposited film forming apparatus is performed as follows. That is, the inside of the vacuum container 201 is degassed by a vacuum pump (not shown), and the pressure inside the reaction container is set to 1 × 10 ^−4.
Adjust to less than Torr. Then the substrate holder 207
By energizing a heater built in the substrate, the temperature of the substrate 205 is heated and maintained at a temperature suitable for film deposition. For example, in the case of forming an amorphous silicon deposited film, a source gas such as silane gas (SiH ₄ ) is introduced into the reaction vessel through the source gas supply pipe / bias voltage application rod 208, and an appropriate bias voltage is applied. Is applied. At the same time, a microwave power source (not shown) is energized and a frequency of 500 MHz is applied.
A microwave of z or more, preferably 2.45 GHz is generated, and the microwave is introduced into the reaction vessel 201 through the waveguide 203 and the dielectric window 202. Thus, the gas in the reactor 201 is excited by the energy of microwaves and dissociates, and a deposited film is formed on the surface of the substrate 205.

[0007]

However, in the above-mentioned conventional example, since the wall 209 forming the film forming chamber 201 has a single structure, the base 205 and the inner surface of the wall 209 have the same potential (earth). .. Therefore, the plasma distribution near the substrate 205 and the plasma distribution near the inner surface of the wall 209 of the film forming chamber 201 are similar.

Since the neutral radical particles mainly contribute to the formation of the deposited film formed on the surface of the base 205, the neutral radical particles are sometimes large in amount and the above-mentioned wall. 209 is consumed for the formation of a deposited film on the inner surface of 209, and as a result, the amount flying to the surface of the essential substrate 205 is reduced by that amount, and at the same time, the utilization efficiency of the raw material gas is reduced and the microwave is used. Radiation efficiency is lowered, which not only lowers the deposition rate of the film on the surface of the substrate 205, but also deteriorates the quality of the formed film.

Furthermore, when a deposited film is formed on the inner surface of the wall 209 as described above, the film becomes flakes and peels off when it reaches a certain thickness and scatters into the film forming chamber 201 to form a substrate. It may adhere to the surface of the substrate 205, and as a result, the deposited film formed on the surface of the substrate 205 cannot be a product.

As means for solving these problems, the inner surface of the wall 209 of the film forming chamber 201 and the dielectric window are regularly inspected and replaced, and the process operation is performed by selecting a specific parameter for the apparatus. It has been devised such as installing the means to do. However, none of the contrivances satisfies the requirement of constantly and efficiently producing a deposited film product with stable quality and stably supplying the deposited film product at low cost.

On the other hand, various kinds of devices have been diversified, and element members therefor, that is, those satisfying requirements such as various characteristics as a whole, are suitable for the object of application and use, and in some cases have a large area. Is. It is a social requirement that a stable deposited film product is constantly supplied at a low cost, and there are situations in which there is a strong demand for the development of a technology that meets this requirement.

The present invention provides a deposited film forming apparatus and a deposited film forming method capable of forming a high quality film with a high deposition rate and less adhering the film to the inner surface of the film forming chamber. The purpose is to

[0013]

A deposited film forming apparatus according to the present invention comprises a film forming chamber capable of being airtight in vacuum, an exhaust means for exhausting a film forming space in the film forming chamber, and a reaction in the film forming space. At least a means for introducing a gas, a means for introducing a microwave into the film forming space, and a holding means for holding a substrate for forming a deposited film in the film forming chamber, The film forming space is evacuated by the evacuation means, a reaction gas and microwave energy are introduced into the film forming space, and a glow discharge excited by the introduced microwave energy forms a deposited film on the substrate. In the deposited film forming apparatus, the wall forming the film forming chamber has a double structure of an inner wall and an outer wall electrically insulated from each other, and means for applying a voltage to the inner wall of the film forming chamber is provided. Characterized by having That.

According to the method for forming a deposited film of the present invention, the inside of the film forming space is evacuated, the reaction gas and the microwave energy are introduced into the film forming space, and the glow discharge excited by the introduced microwave energy is applied on the substrate. In the deposited film forming method for forming a deposited film, the film is formed while a potential difference is provided between the inner wall of the film forming chamber and the substrate.

[0015]

The operation of the present invention will be described below with reference to the detailed construction.

The present inventor has conducted extensive studies to overcome the above-mentioned problems in the conventional apparatus, and as a result, in order to obtain a stable and high-quality deposited film at high speed in the microwave plasma CVD apparatus, the film formation is performed. The wall forming the chamber has a double structure of an outer wall and an inner wall, the outer wall and the inner wall are electrically insulated, and a voltage is applied to the inner wall of the film forming chamber so that an electric field is applied between the substrate and the inner wall of the film forming chamber. We have found that it is necessary to apply

This electric field has the following effects.

That is, for example, when a positive potential is applied to the inner wall of the film forming chamber and the substrate is grounded, an electric field is generated between the film forming chamber and the substrate, and the direction of the electric field is entirely in the film forming chamber. It goes from the inner wall toward the substrate. Therefore, since the distribution of plasma is different near the substrate and near the inner wall of the film forming chamber, the distribution of neutral radical particles that mainly contribute to film formation is also different near the substrate and near the inner wall of the film forming chamber. Come on. As a result, it becomes possible to deposit the deposited film on the substrate as selectively as possible by applying an electric field of an appropriate magnitude. Moreover, a high-quality deposited film can be deposited at high speed by increasing the density of the neutral radical particles that mainly contribute to film formation near the substrate.

On the contrary, since the deposition rate of the film deposited on the inner wall of the film forming chamber can be reduced, it is difficult for the film deposited on the inner wall of the film forming chamber to peel off and adhere to the substrate. Become.

Further, the ion species accelerated by the electric field cause bombarding on the substrate, whereby the deposited film is locally annealed, stress in the film is relaxed, and defects are reduced, so that a good-quality deposited film is formed. Obtainable.

The preferable strength of the electric field generated in the present invention varies depending on the type of raw material gas and the like.
15 V / cm or more and 500 V / cm or less are preferable, and 30
V / cm or more and 150 V / cm or less are more preferable. When the electric field strength is within such a range, the film formation rate and the electric characteristics of the film are further improved.

In the present invention, the source gas for the deposited film is, for example, amorphous silicon forming source gas such as silane (SiH ₄ ) or disilane (Si ₂ H ₆ ), germane (GeH).
Other functional deposited film forming raw material gases such as ₄ ) or a mixed gas thereof can be used.

Examples of the diluent gas include hydrogen (H ₂ ), argon (Ar) and helium (He).

Further, as a characteristic improving gas for changing the band cap width of the deposited film, an element containing a nitrogen atom such as nitrogen (N ₂ ) or ammonia (NH ₃ ), oxygen (O ₂ ), nitric oxide (NO ), Elements containing oxygen atoms such as dinitrogen oxide (N ₂ O), methane (CH ₄ ), ethane (C ₂ H ₆ ) ethylene (C ₂ H ₄ ), acetylene (C ₂ H ₂ ), propane (C
Hydrocarbons such as ₃ H ₈ ), fluorinated compounds such as silicon tetrafluoride (SiF ₄ ), disilicon hexafluoride (Si ₂ F ₆ ), germanium tetrafluoride (GeF ₄ ), or a mixed gas thereof. ..

For the purpose of doping, diborane (B
_The present invention is similarly effective even if a dopant gas such as ₇ H ₆ ), boron fluoride (BF ₃ ) or phosphine (PH ₃ ) is simultaneously introduced into the discharge space (film forming space).

The base material is, for example, stainless steel,
Al, Cr, Mo , Au, In, Nb, Te, V, T
Metals such as i, Pt, Pd, and Fe, their alloys or surfaces
Conductive treated polycarbonate and other synthetic resins, glass
Soot, ceramics, paper, etc. are commonly used in the present invention.

The lateral direction of the substrate is preferably 10 mm or more, and most preferably 20 mm or more and 500 mm or less. The length of the substrate is not particularly limited, and it can be applied to continuous film formation using a strip substrate.

The temperature of the substrate during the formation of the deposited film in the present invention is effective at any temperature, but it is particularly preferably 20 ° C. or higher and 500 ° C. or lower, and more preferably 50 ° C. or higher and 450 ° C. or lower because it exhibits better effects.

Examples of the method of introducing microwaves to the reaction furnace in the present invention include a method using a waveguide or a coaxial cable. The introduction into the reaction furnace is performed through one or a plurality of dielectric windows. Alternatively, a method of installing the antenna in the furnace may be used. At this time, as a material for the introduction window of the microwave into the furnace, materials such as alumina, aluminum nitride, silicon nitride, silicon carbide, silicon oxide, beryllium oxide, Teflon, polystyrene, etc. which are less likely to cause microwave loss are usually used. It

[0030]

Embodiments of the present invention will now be described in detail with reference to the drawings, but the scope of the present invention is not limited thereto.

Example 1 FIG. 1 is a schematic perspective view of a deposited film forming apparatus used in Example 1.

In FIG. 1, 101 is a film forming chamber, which has a vacuum airtight structure. Reference numeral 102 denotes a dielectric window formed of a material capable of efficiently transmitting microwave power into the film forming chamber and maintaining vacuum tightness, for example, quartz glass or alumina ceramic. Reference numeral 103 denotes a microwave transmission section, which is mainly composed of a metal waveguide, and a microwave power source (not shown) via a matching device isolator.
It is connected to the. An exhaust pipe 104 has one end opening into the film forming chamber 101 and the other end communicating with an exhaust device (not shown). Reference numeral 105 denotes a substrate for forming a deposited film, and 106
Indicates a film forming space.

Reference numeral 107 designates a base holder having a built-in heater. Reference numeral 108 is a source gas supply pipe, and in this example,
The insulator 112 electrically insulates the inner wall described later.

Reference numeral 109 denotes an inner wall of the film forming chamber, and 110 denotes an outer wall of the film forming chamber. That is, the wall forming the film forming chamber is the inner wall 10
It has a double structure of 9 and the outer wall 110. Inner wall 109
The outer wall 110 and the outer wall 110 are electrically insulated by an insulating layer (not shown). Further, the inner wall 109 is electrically insulated from the base body holder 107 by the insulator 113. In this example, the means for applying a voltage to the inner wall 109 is composed of the power supply 111 and the wiring 114, and one end of the wiring 114 is electrically connected to the inner wall 109. Of course, the wiring 114 is electrically insulated from the outer wall 110.

The deposited film formation by the present deposited film forming apparatus is performed in the same manner as the deposited film forming apparatus shown in the prior art except that a bias voltage is applied to the inner wall 109 and an electric field is applied in the film forming space.

Using the apparatus shown in FIG. 1, an amorphous silicon film was deposited on the base 105 under the conditions shown in Table 1.

The substrate used was SUS304 stainless steel having a 30 cm square and 0.1 mm thick surface mirror-polished. The microwave power source is made by Japan High Frequency (2.45 GHz).
I used the one.

[0038]

[Table 1] In this example, the substrate 105 is grounded, and a voltage is applied to the inner wall 109 of the film forming chamber 101 so that the substrate 105 and the film forming chamber 10 are connected to each other.
An amorphous silicon film was deposited by changing the strength of the electric field while applying an electric field to the inner wall 109 of No. 1.

FIG. 2 shows the relationship between the strength of the electric field and the film formation rate, and FIG. 3 shows the relationship between the strength of the electric field and the conductivity.

However, the horizontal axis in FIG. 2 represents the strength of the electric field in the vicinity of the substrate surface, and the vertical axis represents the film formation rate obtained from the film thickness measured by a stylus type film thickness meter.

The abscissa of FIG. 3 shows the electric field strength near the surface of the substrate, and the ordinate shows the conductivity measured with the ITO transparent conductive film on the surface of the deposited film (the photoconductivity is AM1). 0.5, value at 100 mW irradiation).

From these results, the following findings were obtained.

In the case of a substrate to which a negative electric field is applied, film formation is performed from an electric field of 15 V / cm or more due to the effect of plasma expansion changed by the electric field near the surface of the substrate and the effect of annealing by bombarding the substrate surface with positive ions. An improvement in speed and an improvement in electrical characteristic conductivity were obtained (FIGS. 2 and 3). This effect reached almost the maximum at 30 V / cm, and the electric field was 1
Up to 00 V / cm, a certain effect was obtained. However, when the electric field is 150 V / cm or more, the film formation rate remains constant, but the dark conductivity increases and the photoconductivity starts to decrease. It is considered that this is because the bombardment against the substrate becomes excessive and the effect of deterioration due to structural destruction such as generation of dangling bonds in the film due to bombardment cannot be ignored with respect to the effect of stress relief by annealing.

Further, no peeling of the deposited film deposited on the inner wall of the film forming chamber was observed even after all the experiments were completed.

(Comparative Example 1) An amorphous silicon film was deposited under exactly the same conditions as in Example 1 (Table 1) using the conventional apparatus shown in FIG.

At this time, the substrate 205 and the wall 209 of the film forming chamber 201 are grounded, a voltage is applied to the bias applying rod 208, and an electric field is applied in the film forming space 206 to change the strength of the electric field and the amorphous state. A silicon film was deposited.

FIG. 4 shows the relationship between the strength of the electric field and the film formation rate, and FIG. 5 shows the relationship between the strength of the electric field and the conductivity.

However, the horizontal axis of FIG. 4 represents the strength of the electric field in the vicinity of the substrate surface, and the vertical axis represents the film formation rate obtained from the film thickness measured by a stylus type film thickness meter.

In FIG. 5, the horizontal axis represents the electric field strength near the surface of the substrate, and the vertical axis represents the conductivity measured with the ITO transparent conductive film on the surface of the deposited film (the photoconductivity is AM 1.5, value at 100 mW irradiation).

From these results, as in Example 1, 15
From the electric field of V / cm or more, the film formation rate and the electric characteristics were improved, and this effect reached a maximum at 30 V / cm. However, in comparison with the effect of Example 1, the film forming rate of Example 1 is higher by up to 5%, and the ratio of photoconductivity to dark conductivity is also significantly higher in Example 1. There is.

Further, when the inside of the film forming chamber was observed after all the experiments of this Comparative Example 1 were completed, a slight separation of the deposited film deposited on the inner surface of the wall of the film forming chamber was observed.

As described above, by applying an electric field between the substrate and the inner wall of the film forming chamber, the film forming rate is increased, the electrical characteristics are improved, and the film deposited on the surface of the inner wall of the film forming chamber is deposited. It turns out that the speed can be reduced.

Example 2 and Comparative Example 2 An amorphous silicon germanium film was deposited on a substrate under the conditions shown in Table 2 using the apparatus shown in FIGS. 1 and 6.

As in Example 1 and Comparative Example 1, when the voltage was applied to the inner wall of the film forming chamber, the film forming rate was higher than when the voltage was applied to the bias voltage applying rod which is the conventional example.
The ratio of photoconductivity to dark conductivity also increased.
The relationship between the electric field and the conductivity was the same as in Example 1 and Comparative Example 1. That is, an improvement in film formation rate and electrical characteristics was observed from an electric field of 15 V / cm or more, and this effect was 30 V.
/ Cm, the maximum was reached, and a certain effect was obtained up to an electric field of 100 V / cm. However, the electric field is 150 V / cm
On the contrary, the dark conductivity increased and the photoconductivity started to decrease.

[0055]

[Table 2] (Example 3) For the purpose of stabilizing the discharge, a gas for stabilizing the discharge was introduced into the discharge space at the same time as the raw material gas to form a deposited film.

In this example, argon Ar and silicon tetrafluoride SiF ₄ were used as the gas for stabilizing the discharge. According to the conditions shown in Tables 2 and 3, a voltage was applied to the substrate in the same manner as in Example 1, and as a result, in order to stabilize the discharge,
The same results as in Example 1 were obtained, except that the improvement in electrical characteristics was superior to that in the case of no gas for stabilizing the discharge.

At this time, the ratio of Ar and SiF ₄ is set to 0.
When changed from 1% to 25%, the absolute value of the improvement in electrical characteristics changes depending on the mixing ratio, but the electric field is 15 V.
/ Cm or more and 500 V / cm or less, preferably 30 V / cm
Above 300 V / cm, it was confirmed that the film formation rate and the electrical characteristics were improved.

[0058] In the SiF ₄ is 25% or less, in any case, the present invention particularly, but is effective, SiF ₄ from 2% 1
A large effect was recognized in the range of 5%.

[0059]

According to the present invention, the voltage applying means is provided on the inner wall of the film forming chamber so that an electric field can be applied in the film forming space, whereby the characteristics of the deposited film are improved and the film forming rate is improved. Can be increased.

[Brief description of drawings]

FIG. 1 is a perspective schematic view of a deposited film forming apparatus that best shows the features of the present invention.

FIG. 2 is a graph showing a relationship between an electric field and a film formation rate when the device of the present invention is used.

FIG. 3 is a graph showing the relationship between electric field and conductivity when the device of the present invention is used.

FIG. 4 is a graph showing a relationship between an electric field and a film formation rate when a conventional device is used.

FIG. 5 is a graph showing the relationship between electric field and electric conductivity when a conventional device is used.

FIG. 6 is a schematic perspective view of a conventional deposited film forming apparatus.

[Explanation of symbols]

 101 deposition chamber, 102 dielectric window, 103 waveguide, 104 exhaust pipe, 105 substrate, 106 deposition space (discharge space), 107 substrate holder, 108 source gas supply pipe, 109 inner wall, 110 outer wall, 111 power supply, 112 insulator, 113 insulator, 114 wiring, 201 film forming chamber, 202 dielectric window, 203 waveguide 204 exhaust pipe, 205 substrate, 206 film forming space (discharge space), 207 substrate holder, 208 source gas supply pipe A bias voltage applying rod, 209 wall.

Claims (2)

[Claims] 1. A film forming chamber capable of being airtight in vacuum, an exhaust unit for exhausting a film forming space in the film forming chamber, a unit for introducing a reaction gas into the film forming space, and an inside of the film forming space. At least a means for introducing a microwave and a holding means for holding a substrate for forming a deposited film in the film forming chamber, the inside of the film forming space is exhausted by the exhausting means, A wall forming the film forming chamber in a deposited film forming apparatus for forming a deposited film on the substrate by introducing a reactive gas and microwave energy into the film forming space and glow discharge excited by the introduced microwave energy. Is a double structure of an inner wall and an outer wall electrically insulated from each other, and means for applying a voltage is provided on the inner wall of the film forming chamber. 2. A deposition film is formed on a substrate by evacuating the film forming space, introducing a reaction gas and microwave energy into the film forming space, and performing glow discharge excited by the introduced microwave energy. In the deposited film forming method, the film is formed while a potential difference is provided between the inner wall of the film forming chamber and the substrate.