JPH0639700B2 - Deposited film formation method - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a silicon-containing deposited film, especially a functional film, particularly a semiconductor device, a photosensitive device for electrophotography,
The present invention relates to a method suitable for forming a polycrystalline silicon-containing deposited film used in a line sensor for image input, an imaging device, and the like.

[Conventional technology]

For example, a vacuum vapor deposition method, a plasma CVD method, a CVD method, a reactive sputtering method, an ion plating method, an optical CVD method, or the like has been attempted to form an amorphous silicon film, and in general, a plasma CVD method is used. Is widely used and commercialized.

In addition, the deposited film composed of amorphous silicon has electrical and optical characteristics, fatigue characteristics after repeated use or environmental characteristics of use, and further productivity including uniformity and reproducibility.
In terms of mass productivity, there is room for further improvement in overall characteristics.

In particular, depending on the application of the deposited film, electrical characteristics, large area, uniform film thickness, and uniform film quality must be fully satisfied, and high-speed film formation must achieve reproducible mass production. In forming an amorphous silicon deposited film by the plasma CVD method, a large amount of capital investment is required for a mass production device, and the management items for the mass production are complicated, the management allowable range is narrowed, and the adjustment of the device is also required. Since these are subtle, these are pointed out as problems to be improved in the future.

On the other hand, atmospheric pressure CVD method, LPCVD method and the like are used for forming the polycrystalline deposited film, but high temperature is required,
Therefore, while it is limited to high melting point substrate materials, practical properties cannot be obtained due to difficulty in controlling crystal grain size, compensating for defects existing at grain boundaries, or aligning crystal faces, etc. It has been pointed out that there are problems such as difficulty in obtaining, uniform film thickness or film quality, and poor reproducibility.

In the plasma CVD method, atmospheric pressure CVD method and LP
Although the temperature of the substrate can be lowered as compared with the CVD method, on the other hand, the structure of the reactor is limited to form a stable plasma, and other parameters (introduced gas species, gas flow rate, pressure, high frequency power, exhaust gas) There are many velocities, etc., and each has a great influence on the plasma. Therefore, it is not uncommon for the plasma to be subtly fluctuated by a slight fluctuation of these parameters or a combination thereof, which adversely affects the uniformity of the deposited film and the electrical and optical characteristics. Further, the damage of the deposited film of electrons and ions existing in the plasma to the deposited film is also large, which is one of the factors that deteriorate the film characteristics.

As described above, at present, both amorphous silicon films and polycrystalline silicon films have problems attributable to the formation method thereof, and particularly from the viewpoint of improving the electrical characteristics and stability of the deposited film. In forming a polycrystalline silicon film, it is desired to develop a method for forming a large-area polycrystalline silicon film at low cost while maintaining its practicable characteristics, uniformity, and stability.

The present invention provides a novel method for forming a polycrystalline deposited film which eliminates the above-mentioned drawbacks of the atmospheric pressure CVD method, the LPCVD method and the plasma CVD method, and which does not rely on the conventional forming method.

[Object of the Invention]

An object of the present invention is to improve various characteristics of a polycrystalline film to be formed, film forming rate, reproducibility, and uniform film quality, and is suitable for increasing the area of the film, improving the productivity of the film, and It is an object of the present invention to provide a method for forming a polycrystalline deposited film that can easily achieve mass production.

Means for Solving the Problems The present invention for attaining the above-mentioned object is to provide an active species (A) produced by decomposing a compound containing silicon and halogen in a film forming space for forming a deposited film on a substrate, and the active species (A). A deposition film forming method for forming a deposition film on the substrate by separately introducing (A) and the active species (B) generated by a film-forming chemical substance that chemically interacts with each other and chemically reacting them. In this case, a substrate having a crystallographically oriented surface is used as the substrate, and a gas having an etching action on the deposited film or its active species is supplied to the deposited film growth surface when the deposited film is formed. The film forming method is characterized by preferentially performing crystal growth in a specific plane orientation by applying an etching action to the surface of the deposited film.

In the present invention, an active species (A) generated by decomposing a compound containing silicon and a halogen and the active species (A) instead of generating plasma in a film formation space for forming a polycrystalline deposited film In the presence of an active species (B) generated from a film-forming chemical substance that chemically interacts with the above, a chemical interaction is caused by these substances on a substrate having a crystallographic orientation. At the same time that a polycrystalline deposited film is formed on the substrate, the polycrystalline deposited film is etched by a halogen-containing gas and / or an active species containing a halogen to preferentially have a certain crystal plane orientation corresponding to the orientation on the substrate. It becomes possible to form a polycrystalline deposited film.

Further, according to the present invention, a more stable CVD method can be realized by arbitrarily controlling the atmospheric temperature of the film forming space and the substrate temperature as desired.

One of the differences between the method of the present invention and the conventional CVD method is that the activated species previously activated in a space different from the film formation space (hereinafter referred to as an activation space) are used. As a result, it is possible to dramatically increase the film formation rate as compared with the conventional CVD method, and it is also possible to further lower the substrate temperature during the formation of the deposited film, and the deposition with stable film quality can be achieved. Membranes can be provided industrially in large quantities and at low cost. In the present invention, the active species (A) from the activation space (A) introduced into the film formation space has a life of 0.1 seconds or more, more preferably 1 or more, from the viewpoints of productivity and easiness of handling.
Those that are not less than 10 seconds and optimally not less than 10 seconds are selected and used as desired, and the constituents of this active species (A) constitute the constituents of the deposited film formed in the film formation space. . Also, the chemical substance for film formation is the activation space (B).
Is activated by activation energy,
When being introduced into the film formation space to form a deposited film, at the same time, it chemically interacts with the active species (A) which is introduced from the activation space (A) and includes a constituent element which is a constituent component of the deposited film formed. . As a result, a deposited film is easily formed on the desired substrate.

Further, another feature of the present invention is that at the same time, a constant plane orientation of the crystal is preferentially provided by the etching effect of a gas having an etching activity represented by a halogen or a halogen compound supplied to the film growth surface or its active species. It is possible to form a polycrystalline deposited film, and it is possible to form an excellent polycrystalline deposited film by using a substrate whose surface has an orientation. Although this depends on the film deposition method and deposition conditions, (1,1,0), (1,1,1) and (1,0,0) are particularly dominant in the method of the present invention. By properly selecting the orientation of the substrate surface, the type of etching gas, and the etching conditions, it is possible to realize the conditions for depositing a polycrystal having a stronger orientation, and to achieve a large grain size oriented only to the orientation of the substrate surface. It is possible to form a deposited film.

As the substrate material having the crystal orientation, which is a feature of the present invention, the following conditions are necessary for crystal growth on substrates of different substances. That is, 1. The lattice constant of the crystalline material on the surface of the substrate matches or is very close to the lattice constant of the deposited film.

2. The thermal expansion coefficients of the crystalline material on the substrate surface and the deposited film are the same or very close.

Therefore, CaF ₂ , ZnS, Y is particularly suitable as a material for forming the surface of the substrate in order to obtain a deposited film of crystalline Si.
b, Mn ₃ Ga, NaCoF ₃ , Ni ₃ Sn, Fe
₃ C, NiTex (x <0.7), CoMnO ₃ , NiM
Although nO ₃ , MaZn ₃ , CuCl, AlP, Si and the like can be mentioned, it is possible to obtain a crystalline deposited film by appropriately selecting the deposition conditions even when the above two conditions are deviated. The material is not limited.

In the present invention, as the compound containing silicon and halogen introduced into the activation space (A), for example, a compound obtained by substituting a part or all of hydrogen atoms of a chain or cyclic silane compound with a halogen atom is used. For example,
SiuY ₂ u ₊₂ (u is an integer of 1 or more, Y is F, Cl,
It is at least one element selected from Br and I. ), A chain silicon halide represented by SivY ₂ v
(V is an integer of 3 or more, Y has the above-mentioned meaning), and a chain represented by SiuHxYy (u and Y have the above-mentioned meaning. X + y = 2u or 2u + 2). Examples include a ring-shaped or cyclic compound.

Specifically, for example, SiF ₄ , (SiF ₂ ) ₅ , (SiF ₂ ) ₆ , (SiF ₂ ) ₄ , Si ₂ F ₆ , Si ₃ F ₈ , SiHF ₃ , SiH ₂ F ₂ , SiCl ₄ , ( SiCl ₂ ) ₅ , SiBr ₄ , (SiBr ₂ ) ₅ , Si ₂ Cl ₆ , Si ₂ Br ₆ , SiHCl ₃ , SiH ₃ Cl, SiH ₂ Cl ₂ , SiHBr ₃ , SiHi ₃ , Si ₂ Cl ₃ F _3, etc. Examples include those in a gas state or easily gasified.

In order to generate the active species (A), in addition to the compound containing silicon and halogen, if necessary, other silicon compounds such as silicon simple substance, hydrogen, and halogen compounds (for example, F ₂
Gas, Cl ₂ gas, gasified Br ₂ , I _2, etc.) can be used together.

In the present invention, as a method for generating the active species (A) in the activation space (A), microwave, RF, low frequency, electric energy such as DC, heater heating, infrared rays are taken into consideration in consideration of each condition and device. Activation energy such as heat energy and light energy due to heating is used.

Activated species (A) are generated by applying excitation energy such as heat, light, or electricity to the above-mentioned substances in the activation space (A).

In the activation space (B) used in the method of the present invention,
Hydrogen gas and / or a halogen compound (for example, F ₂ gas, Cl ₂ gas, gasified Br ₂ , I ₂ etc.) is advantageously used as the chemical substance for forming the film to generate the active species (B). . Further, in addition to these chemical substances for film formation, for example, an inert gas such as helium, argon or neon can be used. When a plurality of these film-forming chemical substances are used, they can be mixed in advance and introduced into the activation space (B) in a gas state, or these film-forming chemical substances can be introduced into a gas state. It is also possible to separately supply each from an independent supply source and introduce them into the activation space (B), or to each independent activation space and activate each individually.

In the present invention, the ratio of the amount of the active species (A) and the amount of the active species (B) introduced into the film forming space depends on the film forming conditions,
The type of active species and the like are appropriately determined as desired, but 10: 1 to 1:10 (introduction flow rate ratio) is suitable, and more preferably 8: 2 to 4: 6.

Further, in the method of the present invention, etching is performed at the same time as or almost at the same time as film formation. That is, a gas having an etching activity from the beginning is introduced, or a gas having a latent etching property is decomposed by electric energy, thermal energy, light energy, etc.,
A gas having an etching activity, an active species and the like are generated to etch the deposited film which is being formed on the substrate.
At this time, the etching rate for the polycrystalline deposited film differs depending on the crystal plane, and the gas species, flow rate (ratio), and
By appropriately selecting the substrate temperature and the like, it is possible to selectively form an orientation plane corresponding to the orientation of the substrate surface.

Examples of the gas or active species having an etching action in the present invention include F ₂ , Cl ₂ , halogenated gas such as Br ₂ , I ₂ , CHF ₃ , CF ₄ , C ₂ F ₆ , CC.
l ₄ , CBrF ₃ , CCl ₂ F ₂ , CCl ₃ F, CCl
F ₃ , C ₂ Cl ₂ F ₄ and other halogenated carbons, BC
S, including boron halides such as l ₃ and BF _3.
Halides such as F ₆ , NF ₃ and PF ₅ , radicals such as F ^* and Cl ^* by these gases, CF ₃ ⁺ ,
Ions such as CCl ₃ ⁺ are used. These can be mixed and used, or the etching characteristics can be controlled by adding O ₂ , H ₂ , and other gases to the extent that they do not affect the film.

As a method of introducing these gases or active species into the etching on the film surface, an etching space may be separately provided and the process may be repeated alternately with the film formation, or in a state where the film formation space has etching activity. The object of the present invention may be achieved by introducing it, and effecting an etching action at the same time as the film formation to limit the growth direction of the crystalline film.

The deposited film formed by the method of the present invention can be doped with an impurity element during or after film formation. As an impurity element to be used, an element of Group III A of the periodic table such as B, Al, Ga, I is used as a p-type impurity.
Preferred examples thereof include n, Tl, and the like. Examples of the n-type impurities include elements of Group A of the periodic table, such as P, As, S.
Suitable examples include b and Bi, but especially B and
Ga, P, Sb, etc. are optimal. The amount of impurities to be doped is appropriately determined according to desired electrical / optical characteristics.

As the substance containing such an impurity element as a component (impurity introducing substance), a compound that is in a gas state at room temperature and atmospheric pressure or is a gas at least under activation conditions and can be easily vaporized by an appropriate vaporizer is used. It is preferable to select it. Examples of such compounds include PH ₃ , P ₂ H ₄ and PF.
₃ , PF ₅ , PCl ₃ , AsH ₃ , AsF ₃ , As
_{F 5, AsCl 3, SbH 3} , SbF 5, SiH 3, B
_{F 3, BCl 3, BBr 3} , B 2 H 6, B 4 H 10, B 5
_{H 9, B 5 H 11,} B 6 H 10, B 6 H 12, AlCl 3 and the like. The compound containing an impurity element may be used alone or in combination of two or more.

The compound containing the impurity element as a component may be directly introduced into the film formation space in a gas state, or the activation space (A) or the activation space (B) or the third activation space may be previously introduced. It can be activated in (C) and then introduced into the film formation space.

Next, an example of the deposited film forming method of the present invention for depositing a polycrystalline silicon film will be specifically described with reference to the drawings.

FIG. 1 is a partial cross-sectional view showing a schematic configuration of an example of a deposited film forming apparatus for carrying out the method of the present invention.

In FIG. 1, reference numeral 101 denotes a deposition chamber in which a polycrystalline silicon film is deposited. The inside of the deposition chamber 101 is connected to an exhaust system (not shown) through an exhaust pipe 121, and an exhaust valve 120 is used to move the inside of the deposition chamber 101. It can be maintained at the desired pressure. The pressure in the deposition chamber 101 is usually 10 ⁻⁵ To
rr to 1.0 Torr, preferably 10 ⁻⁴ Torr to 0.1T
adjusted to orr. The substrate support 10 is provided in the deposition chamber 101.
A desired substrate 103 is placed on the substrate 2.

Reference numeral 104 denotes a heater for heating the substrate, which is supplied with power via the conductor wire 105 to generate heat. Although the substrate temperature is not particularly limited, it is preferably 1 in carrying out the method of the present invention.
It is desirable that the temperature is from 00 to 500 ° C, more preferably from 150 to 400 ° C.

Reference numerals 106 to 111 denote gas supply sources, which are provided according to the number of silicon compounds and, if necessary, hydrogen, halogen compounds, inert gases, and compounds containing impurity elements as components. When using a liquid one of the raw material compounds, an appropriate vaporizer is provided. In the figure, the gas supply sources 106 to 111 are denoted by a in the form of a branch pipe, b is denoted by a flow meter, c is denoted by a pressure gauge for measuring the pressure on the high pressure side of each flow meter, d Alternatively, a valve denoted by e is a valve for adjusting each gas flow rate. 112,1
Reference numerals 25 and 126 are gas introduction pipes to the film formation space.

Further, 114 and 123 are activation spaces for generating active species (A) and active species (B), respectively, and 113 and 122 are microwave plasma generators for generating active species.

Reference numerals 116, 117, 118 and 119 represent flows of the active species (A) and the active species (B) or substances produced by their chemical reaction.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

Example 1 A 4 cm × 4 cm CaF ₂ single crystal substrate (however, oriented to (110)) was used as a substrate, and a polycrystalline silicon film was formed on the substrate using the apparatus shown in FIG. That is, the base 1
03 was placed on the support base 102, the inside of the deposition chamber 101 was evacuated by using an exhaust device, and the pressure was reduced to about 10 ⁻⁶ Torr. 45 sccm of H ₂ gas was introduced into the activation chamber (B) 123 from the gas supply cylinder 106 through the gas introduction pipe 125. The H ₂ gas or the like introduced into the activation chamber (B) 123 is activated by the microwave plasma generator 122 into active hydrogen or the like, and the active hydrogen or the like is introduced into the film forming chamber 101 through the introduction pipe 124. .

On the other hand, in the activation chamber (A) 114, SiF ₄ gas 25s
ccm was introduced. The SiF ₄ gas introduced into the activation chamber (A) 114 is activated by the microwave plasma generator 113, and activated species originating from SiF ₄ are introduced into the introduction pipe 1
It is introduced into the film forming chamber 101 through 12. Further F ₂
15 sccm of gas is introduced into the film forming chamber 1 through the gas introducing pipe 126.
01 introduced.

The pressure in the film forming chamber 101 was maintained at 0.02 Torr, and the substrate 103 was previously heated to 350 ° C. by the heater 104. By utilizing the difference in etching speed depending on the halogen-based material, the above-mentioned polycrystalline silicon film was etched at the same time as the deposition, thereby forming a polycrystalline silicon film having a certain strong orientation. At this time, the difference in etching speed depending on the crystal plane is (1,0,0)>(1,1,1)> (1,1,0), and the (1,1,0) plane is the main crystal plane. As a result, a polycrystalline silicon film having is formed. That is, the formed deposited film was evaluated by X-ray diffraction, (1,1,0)
The peak intensities at the crystal angle (2θ) 47.3 degrees reflecting the planes are the crystal angles (2θ) 28.4 degrees and 69.2 degrees reflecting the (1,1,1) plane and the (1,0,0) plane, respectively. The value was 500 to ∞ times. Further, when observed by a transmission electron microscope, the crystal grain size was 1.2 μm.

When the deposited film was analyzed by FT-IR,
A weak peak was observed near 2000 cm ⁻¹ and the hydrogen content was 0.2 atom%.

The above-mentioned film forming conditions and the evaluation results of the deposited film are shown in Table 1 and Table 2, respectively.

(Example 2) The film type and the flow rate were changed as shown in Table 3, and an etching gas was separately introduced from the gas introduction pipe to form a film under the same conditions as in Example 1. The evaluation results are shown in Table 4.

(Example 3) A ZnS single crystal substrate of 4 cm x 3 cm (however, oriented to (110) with respect to the horizontal plane) was used as a substrate (Example 1). A good quality polycrystalline silicon film shown in the table was formed.

Hereinafter, in Examples 4 and 5, a high-quality polycrystalline silicon film was formed by using ZnS polycrystal (110) orientation and ZnS polycrystal (111) orientation as substrates, and the production conditions and various characteristics thereof are respectively described in Section 7, It is summarized in Table 8 and Tables 9 and 10.

(Effect of the Invention) As described above, according to the present invention, a film having a very high orientation and a large dahrain size can be formed. The thin film transistor using the above-mentioned highly oriented film has a high mobility and can sufficiently function for driving a display or a sensor.

[Brief description of drawings]

 FIG. 1 is a sectional view of the deposited film forming apparatus of the present invention. 101 ... Deposition chamber 102 ... Substrate 103 ... Deposition film 104 ... Substrate heating heaters 106-111 ... Gas supply source 114 ... Activation chamber (A) 123 ... Activation chamber (B)

Claims (1)

[Claims] 1. An active species (A) produced by decomposing a compound containing silicon and a halogen in a film forming space for forming a deposited film on a substrate, and the active species (A) and a chemistry. The active species (B) generated from the film-forming chemical substance that interacts with each other separately and chemically react with each other to form a deposited film on the substrate. When a substrate having a crystallographically oriented surface is used as the substrate, a gas having an etching action on the deposited film or its active species is supplied to the deposited film growth surface during formation of the deposited film to A deposited film forming method characterized by preferentially performing crystal growth in a specific plane orientation by applying an etching action to the surface.