JPH0750683B2 - Deposited film formation method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a deposited film containing doped silicon,
In particular, doped amorphous silicon (hereinafter referred to as a-Si) useful as a photoconductive film, a semiconductor film, etc.
Alternatively, it relates to a method suitable for forming a deposited film of polycrystalline silicon.

[Prior art]

Conventionally, for example, N-type and P-type a-Si deposited films are treated with SiH ₄ or
It is known to form by a glow discharge deposition method or a thermal energy deposition method using Si ₂ H ₆ as a raw material. That is, Si
It is well known that H ₄ and Si ₂ H ₆ are excited and decomposed using electric energy and thermal energy to form a deposited film of a-Si on a substrate, and this film is used for various purposes.

However, when these SiH ₄ and Si ₂ H ₆ are used as raw materials, in the glow discharge deposition method, the influence of the discharge energy on the film being deposited under high output is large, and the conditions are stable and reproducible. Difficult to control. This is particularly noticeable when forming a large-area, thick-film deposited film.

Also, in the thermal energy deposition method, since a high temperature is required, the substrate to be used is limited, and the high temperature increases the probability that useful bonded hydrogen atoms in a-Si are released, which is desirable. It becomes difficult to obtain the characteristics.

Thus, when forming a deposited film using SiH ₄ and Si ₂ H ₆ , it is difficult to ensure uniform electrical and optical properties and stability of quality, and the film surface is disturbed during deposition and At present, there are still some problems to be solved, such as easy occurrence of defects.

Therefore, in recent years, in order to eliminate these problems, SiH ₄ and
Light energy deposition method of a-Si using Si ₂ H ₆ as raw material (optical CVD
Law) has been proposed and is attracting attention. According to this light energy deposition method, the aforesaid problem can be remarkably improved due to the advantage that an a-Si deposition film can be formed at a low temperature. However, with the light energy deposition method using SiH ₄ and Si ₂ H ₆ as the raw material under a relatively small excitation energy such as light energy, it is not possible to expect dramatically efficient decomposition, so that the deposition rate I can not expect improvement,
There is a new problem that there is a problem in mass productivity.

The present invention has been made to solve these problems at present.

[Object of the Invention]

An object of the present invention is to provide a method for forming a deposited film containing doped silicon, which can increase the film formation rate while maintaining high quality.

Another object of the present invention is to provide a large area and thick film.
It is an object of the present invention to provide a deposited film forming method capable of producing a deposited film containing high-quality doped silicon while ensuring uniform electrical and optical characteristics and stability of quality.

The object of the present invention is to provide Si ₃ F ₈ , S in a chamber containing a substrate.
At least one chain silicon halide compound selected from i ₅ F ₁₂ , Si ₆ F ₁₄ , and Si ₃ Cl ₈ and an element belonging to Group III or Group V of the periodic table (hereinafter referred to as an impurity element) ) Is formed as a component and a gaseous atmosphere of hydrogen is formed, and the chain silicon halide compound and the hydrogen are excited by utilizing light energy, and the silicon doped with the element on the substrate is removed. It is achieved by a method for forming a deposited film, which comprises forming a deposited film containing.

[Embodiment]

The deposited film containing silicon doped with the impurity element formed by the method of the present invention may be crystalline or amorphous, and the silicon bond in the film may be in any form from oligomeric to polymeric. . Further, hydrogen atoms and halogen atoms in the raw material may be incorporated in the structure.

Hereinafter, embodiments of the present invention will be described mainly in the case of an a-Si deposited film.

The chain silicon halide compound of the above general formula is a linear or branched chain silicon hydride compound (chain silane compound).
A halogen derivative of Si _n H _{2n + 2} , which is a compound that is easy to manufacture and has high stability. In the general formula, X represents a halogen atom selected from fluorine, chlorine, bromine and iodine. The reason for limiting the value of n to 1 to 6 is that the larger n is, the easier the decomposition is, but the more difficult it is to vaporize, the more difficult the synthesis is, and the lower the decomposition efficiency is.

The following compounds may be mentioned as preferred examples of the chain silicon halide compound of the above general formula.

(1) SiF ₄ , (2) Si ₂ F ₆ , (3) Si ₃ F ₈ , (4) Si
₄ F ₁₀ , (5) Si ₅ F ₁₂ , (6) Si ₆ F ₁₄ , (7) SiCl ₄ ,
(8) Si ₂ Cl ₆ , (9) Si ₃ Cl ₈ , (10) SiBr ₄ , (11) Si ₂
Br ₆ , (12) Si ₃ Br ₈ , and (13) SiI ₄ .

The impurity element used in the present invention is, as a p-type impurity, an element of Group III A of the periodic table, for example, B, Al, G
Preferred examples thereof include a, In, Tl, and the like. Examples of the n-type impurities include elements of Group V group A of the periodic table, such as N, P, As, Sb, Bi.
Etc. are mentioned as suitable ones, but B, Ga, P, Sb etc. are most suitable. The amount of impurities to be doped is appropriately determined according to desired electrical and optical characteristics, but in the case of impurities of Group III A of the periodic table, doping is performed in an amount range of 3 × 10 ^{-2 to 4} atomic%. All you need to do is Group V A of the Periodic Table
In the case of the above impurity, doping may be performed within the range of 5 × 10 ^{−3 to 2} atomic%.

As the compound containing such an impurity element as a component, it is preferable to select a compound which is in a gas state at room temperature and atmospheric pressure, or is a gas at least under the conditions for forming a deposited film, and which can be easily vaporized by an appropriate vaporizer. . Examples of such _{compounds, PH 3, P 2 H 4} , PF 3, PF 5, PCl 3, AsH 3, AsF 3, AsF 5, AsC
l ₃ , SbH ₃ , SbF ₅ , SiH ₃ , BF 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 can be mentioned. The compound containing an impurity element may be used alone or in combination of two or more.

In the present invention, the chamber for forming a deposited film containing silicon doped with an impurity element is preferably placed under reduced pressure, but the method of the present invention can be carried out under normal pressure or under pressure.

The excitation energy used in the present invention is limited to light energy, but the chain silicon halide compound of the general formula is easily excited and decomposed by application of relatively low energy such as light energy, It is possible to form a high-quality silicon deposited film, and in this case, the temperature of the substrate can be set to a relatively low temperature. Further, the excitation energy is uniformly or selectively applied to the raw material reaching the vicinity of the substrate, but if light energy is used, the entire substrate is irradiated with an appropriate optical system to form a deposited film. It can be formed, or a deposited film can be partially formed by selectively irradiating only a desired portion with selective control, and a deposited film can be formed by irradiating only a predetermined graphic portion with a resist or the like. It is advantageously used because it can be formed conveniently.

In the present invention, by forming a chain silicon halide compound of the general formula, a compound containing an impurity element as a component, and a gaseous atmosphere of hydrogen in the chamber, hydrogen radicals generated in the process of the excitation / decomposition reaction are generated. Increase reaction efficiency. Moreover, hydrogen is taken into the formed deposited film,
It plays a role in reducing defects in the Si bond structure. Further, the chain-shaped silicon halide compound of the above general formula is
X, SiX ₂ , SiX ₃ , Si ₂ X ₃ , Si ₂ X ₄ , Si ₂ X ₅ , Si ₃ X ₃ , Si ₃ X ₄ ,
Radicals such as Si ₃ X ₅ , Si ₃ X ₆ , Si ₃ X ₇ , etc. are generated, and since hydrogen generates a radical in which Si, X and H are bonded, a reaction process including these radicals is generated. Finally, a good quality film having a small localized level density in which the dangling bond of Si is sufficiently terminated with H or X is obtained.

Further, the chain-like silicon halide compound of the above general formula is 2
Although two or more species may be used in combination, in this case, the characteristics of the film expected by each compound are averaged or synergistically improved.

Hereinafter, a more specific description will be given with reference to the drawings.

The drawing is a schematic view showing an example of an apparatus used for forming an a-Si deposited film used as a photoconductive film, a semiconductor film or the like by the method of the present invention.

In the figure, 1 is a deposition chamber in which a desired substrate 3 is placed on a substrate support base 2 inside. The base body 3 may be any of a conductive, semiconductive, or electrically insulating base.

Reference numeral 4 is a heater for heating the substrate, which is supplied with electric power through the conductor 5 to generate heat. The substrate temperature is not particularly limited, but in carrying out the method of the present invention, it is preferably 50 to 150.
It is desirable that the temperature is ℃, more preferably 100 to 150 ℃.

Reference numerals 6 to 9 are gas supply sources, and in the case of using a liquid one of the chain-shaped silicon halide compound represented by the above general formula and the compound containing an impurity element as a component, an appropriate vaporizer is provided. . The vaporizer includes a type utilizing heating and boiling, a type allowing a carrier gas to pass through the liquid raw material, and the like, and any of them may be used. Further, the hydrogen gas may be used as it is in a molecular form or may be used by radicalizing it in advance.
The number of gas supply sources is not limited to 4, and the number of chain silicon halide compounds of the above-mentioned general formula to be used and compounds containing an impurity element as a component. In the case of using a carrier gas, a diluent gas, a catalyst gas, etc., a compound of the above general formula which is a raw material gas, a compound containing an impurity element as a component and the presence or absence of premixing with hydrogen, and N-type and P-type films on the same substrate It is appropriately selected in consideration of the convenience of forming it above. In the figure, reference numerals of the gas supply sources 6 to 9 have a branch pipe with a, a flow meter with b, and a pressure gauge for measuring the high-pressure side pressure of each flow meter with c. , D or e are valves for adjusting the flow rate of each gas.

The raw material gas, etc. supplied from each gas supply source is supplied by a gas introduction pipe.
The mixture is mixed in the middle of 10, is urged by an exhaust device (not shown), and is introduced into the chamber 1. Reference numeral 11 is a pressure gauge for measuring the pressure of the gas introduced into the chamber 1. A gas exhaust pipe 12 is connected to an exhaust device (not shown) for decompressing the inside of the deposition chamber 1 and forcibly exhausting the introduced gas. 13 is a regulator valve.

As an example of the excitation energy source used in the present invention,
Reference numeral 14 is a light energy generating device, and for example, a mercury lamp, a xenon lamp, a carbon dioxide gas laser, an argon ion laser, an excimer laser or the like is used. The light energy used in the present invention is not limited to ultraviolet energy, and the wavelength range is not limited as long as the source gas can be excited and decomposed and the decomposition product can be deposited. Further, it does not exclude the case where the light energy is absorbed by the raw material gas or the substrate and converted into heat energy, and the heat energy causes excitation / decomposition of the raw material gas to form a deposited film. Light 15 directed from the light energy generator 14 to the entire substrate or a desired portion of the substrate using an appropriate optical system is irradiated to the raw material gas or the like flowing in the direction of the arrow 16 to cause excitation / decomposition to cause the substrate. Three
A deposited film of a-Si is formed on the entire upper surface or a desired portion.

According to the method of the present invention, a deposited film having an arbitrary thickness from a thin film to a thick film can be obtained as desired, and the film area can be arbitrarily selected as desired. The film thickness can be controlled by a usual method such as controlling the pressure, flow rate, concentration, etc. of the source gas, controlling the amount of excitation energy.

FIG. 2 shows a PIN using an a-Si deposited film doped with an impurity element manufactured by carrying out the method of the present invention.
FIG. 3 is a cross-sectional view showing a typical example of a positive diode device.

In the figure, 21 is a substrate, 22 and 27 are thin film electrodes, and 23 is a semiconductor film, which is composed of a P-type a-Si layer 24, an I-type a-Si layer 25, and an N-type a-Si layer 26. To be done. 28 is a conducting wire.

The substrate 21 is semiconductive, preferably electrically insulating. As the semi-electrokinetic substrate, for example, Si,
Examples include semiconductors such as Ge.

As the electrically insulating substrate, a film or sheet of synthetic resin such as polyester, polyethylene, polycarbonate, cellulose acetate, polypropylene, polyvinyl chloride, polyvinylidene chloride, polystyrene and polyamide, glass, ceramic, paper and the like are usually used. The thin film electrodes 22 and 27 are, for example, NiCr, Al, Cr, Mo, Au, Ir, Nb, Ta, V, T
It can be obtained by providing a thin film of i, Pt, Pd, In ₂ O ₃ , SnO ₂ , ITO (In ₂ O ₃ + SnO ₂ ) or the like on a substrate by a process such as vacuum deposition, electron beam deposition, or sputtering. The thickness of the electrode 22 is preferably 30 to 5 × 10 ⁴ Å, more preferably 100 to
It is desirable to be 5 × 10 ³ Å.

If necessary, the film body forming the a-Si semiconductor layer 27 may be an n-type
To obtain 25 or p-type 23, the n-type impurity or the p-type impurity of the impurity elements, or both of the impurity elements are doped in the layer to be formed while controlling the amount of the impurity element at the time of forming the layer. To be done.

Next, the operation for producing the diode shown in FIG. 2 by the method of the present invention using the apparatus shown in FIG. 1 will be described.

The substrate 21 on the surface of which the thin film of the electrode 22 is provided is placed on the support 2 in the deposition chamber 1, and the deposition chamber is evacuated through the gas exhaust pipe 12 by an exhaust device (not shown) to reduce the pressure. The pressure in the deposition chamber under reduced pressure is preferably 5 × 10 ⁻⁵ Torr or less, more preferably 10 ⁻⁶ Torr or less. Valves 6d and 6e of the gas supply source 6 in which the chain-like silicon halide compound of the above general formula in a gas state is stored in order to form the P-type a-Si film 24 on the thin film electrode 22, the gas state Has become P
The valves 7d and 7e of the supply source 7 in which the compound containing the impurity element of the type is stored and the valves 9d and 9e of the supply source 9 in which the hydrogen gas is stored are opened, and these source gases are mixed and deposited. Send it into chamber 1. At this time, the flow rate is adjusted while measuring with the corresponding flow meters 6b, 7b, 9b. The flow rate of the silicon halide gas is preferably 10 to 1000 SCCM, more preferably 20 to 500 SCCM. The flow rate of the P-type impurity gas is determined by (flow rate of silicon halide gas) × (doping concentration).

However, it is very difficult to control the flow rate because the amount of the impurity gas is very small. Therefore, the impurity gas is usually stored and used diluted with H ₂ gas.

The pressure of the mixed gas in the deposition chamber 1 is preferably 10 ^{-2 to} 100T.
It is desirable to maintain orr, more preferably in the range of 10 ^{-2 to 1} Torr.

An optical system (not shown) is incorporated so that the light energy generated by the operation of the light energy generator 14 irradiates the substrate 3 housed in the deposition chamber 1.

Thus, the mixed gas that flows in the vicinity of the surface of the substrate 3, that is, the silicon halide gas, the hydrogen gas, and the impurity gas are given light energy to promote photoexcitation and photodecomposition, and a-Si that is a product substance and a trace amount of P-type impurities. Atoms are deposited on the substrate. Decomposition products other than a-Si and surplus raw material gas not decomposed are discharged through the gas exhaust pipe 12, while
New mixed gas is supplied through the gas introduction pipe 10.

In this way, the P-type a-Si film 24 is formed. The thickness of the P-type a-Si, preferably 100 to 10 ⁴ Å, more preferably in the range of 300~2,000Å is desirable.

Next, the valves 6d, 6e, 7d, 7 connected to the gas supply sources 6, 7, 9
e, 9d, 9e are all closed, and the introduction of gas into the deposition chamber 1 is stopped. By operating an exhaust device (not shown), gases in the deposition chamber, particularly pollutant gases, P-type impurity gases, and other gases other than a-Si source gas are removed, and then the valves 6d, 6e, 9d, 9e are opened again, and the halogen Silicon dioxide gas and hydrogen gas are introduced into the deposition chamber 1. In this case, the preferable flow rate condition and pressure condition are P
This is the same as the case of forming a type a-Si film, and a non-doped, i.e., I-type a-Si film 25 is formed by the same light energy irradiation.

The film thickness of I-type a-Si is 500 to 5 × 10 ⁴ Å, preferably 1000 to
A range of 10,000Å is desirable.

Next, the valves 8d and 8e connected to the gas supply source 8 in which the N-type impurity gas is stored are opened, and the N-type impurity gas is introduced into the deposition chamber 1.

The flow rate of the N-type impurity gas is determined by (flow rate of the silicon halide gas) × (doping concentration) as in the case of determining the flow rate of the P-type impurity gas.

Thus, light energy is imparted to the silicon halide gas, hydrogen gas and N-type impurity gas flowing near the surface of the substrate 3 to promote photoexcitation and photodecomposition, and a-
Si is deposited on the substrate, and a small amount of N
The N-type a-Si film 25 is formed by mixing the type impurity atoms.

The film thickness of the N-type a-Si film 25 is preferably 100 to 10 ⁴ Å, more preferably in the range of 300~2,000Å is desirable.

The thin film electrode 7 on the N-type a-Si film 25 is formed by a method similar to the method of forming the thin film electrode 22. The same applies to film thickness conditions.

Specific examples of the present invention will be shown below.

Example 1 Using the exemplified compounds (1), (2), (3) or (5) as the chain silicon halide compound of the general formula,
Further, as a compound containing an impurity element as a component, PH ₃ or B ₂ H ₆
By using the device shown in FIG. 1 as an impurity.
Alternatively, an a-Si deposited film doped with B (P type) was formed.

First, conductive film substrate (# 7059, Corning)
Was placed on the support base 2, the inside of the deposition chamber 1 was evacuated using an exhaust device, and the pressure was reduced to 10 ⁻⁶ Torr. At the substrate temperature shown in Table 1, a gas obtained by mixing the silicon halide compound in a gaseous state with PH ₃ gas or B ₂ H ₆ gas at a ratio of 1: 5 × 10 ⁻³ was used to produce 110 SCCM and hydrogen. A gas was introduced into the deposition chamber at a flow rate of 40 SCCM, and the substrate was vertically irradiated with a high pressure mercury lamp at a light intensity of 200 mW / cm ² while maintaining the atmospheric pressure in the chamber at 0.1 Torr to form a doped a-Si film. The film formation rate was 35Å / sec.

For comparison, a similarly doped a-Si film was formed using Si ₂ H ₆ . The film formation rate was 15Å / sec.

Then, the obtained a-Si film sample was placed in a vapor deposition tank and the vacuum degree was changed.
Comb type Al gap electrode with 10 ^-5 Torr (length 250μ, width 5m
After forming m), the dark current was measured at an applied voltage of 10 V, the dark conductivity σd was obtained, and the a-Si film was evaluated. The results are shown in Table 1.

As shown in Table 1, the a-Si film according to the present invention exhibits sufficient doping efficiency even at a low substrate temperature and a high σd, as compared with the case of using conventional Si ₂ H ₆ .

Example 2 A polyimide substrate was used as the substrate, and the exemplified compounds (6), (7),
An a-Si film was formed in the same manner as in Example 1 except that (9) was used, and σd was obtained. The results are shown in Table 2.

Example 3 Using the exemplified compounds (1), (2), (3), and (5) as the chain-shaped silicon halide compound of the above general formula, the PIN shown in FIG. Type diode was produced.

First, a glass plate 21 having a 1000 Å ITO film 22 deposited thereon was placed on a support, and a P-type a-Si film 24 (400 Å film thickness) doped with B was formed in the same manner as in Example 1. The light source and the light intensity were 100 mW / cm ² of a low pressure mercury lamp.

Then, the introduction of B ₂ H ₆ gas was stopped and the pressure in the deposition chamber was adjusted to 0.5 Torr.
Except that the I-type a-Si film is the same as that of the P-type a-Si film.
-Si film 25 (film thickness 5000Å) was formed.

Then N doped with P in the same manner as in Example 1
A type a-Si film 26 (film thickness 400 Å) was formed. The light irradiation conditions were the same as those for the P type. Further, an Al electrode 27 having a film thickness of 1000Å was formed on this N-type film by vacuum vapor deposition to obtain a PIN-type diode.

For comparison, a PIN diode was similarly formed using Si ₂ H ₆ .

IV of the diode device (area: 1 cm ² ) thus obtained
The characteristics were measured and the rectification characteristics and the photovoltaic effect were evaluated.
The results are shown in Table 1.

From Table 1, as compared with the case of using conventional Si ₂ H ₆ , excellent rectification characteristics can be obtained by the deposited film according to the present invention even at a low substrate temperature.

Also in terms of light irradiation characteristics, introducing light from the substrate side,
Light irradiation intensity AMI (about 100 mW / cm ² ) with conversion efficiency of 8% or more,
An open circuit voltage of 0.9 V and a short circuit current of 10 mA / cm ² were obtained.

Example 4 A transparent conductive film (polyester base) was used as the substrate, and the exemplified compounds (6), (7) and (9) were used as the chain silicon halide compound of the general formula, and the light source and the light intensity were set to a high pressure mercury lamp. A PIN diode was manufactured in the same manner as in Example 3 except that the rectification ratio and the η value were calculated, except that the value was 200 mW / cm ² . The results are shown in Table 2.

[Advantages of the Invention] According to the present invention, a high quality silicon deposited film can be formed at a low substrate temperature and at a high film forming rate. In addition, even if the film to be formed has a large area and a thick film, uniform electrical and optical characteristics can be obtained, and the stability of quality can be ensured, which is an unprecedented special effect.
In addition, there is no need to heat the substrate at high temperature, which saves energy. It is possible to form a film even on a substrate with poor heat resistance. It is possible to shorten the process by low temperature treatment. The advantages are that it is inexpensive, has excellent stability, and there is little danger of handling.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration diagram showing an example of a light energy irradiation type deposited film forming apparatus used in the present invention. FIG. 2 is a sectional view showing the structure of a PIN diode manufactured by the method of the present invention. 1 ... Deposition chamber, 2 ... Substrate support, 3 ... Substrate, 4 ...
Heater, 6-9 ... Gas supply source, 10 ... Gas inlet pipe,
12 …… Gas exhaust pipe, 14 …… Light energy generator, 21…
… Substrate, 22,27 …… Electrode, 24 …… P-type a-Si film, 25 ……
I-type a-Si film, 26 ... N-type a-Si film, 28 ... Conductive wire.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiro Haruta 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hiroshi Matsuda 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (72) Inventor Takashi Nakagiri 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) Reference JP-A-57-27015 (JP, A) JP-A-57-117233 (JP) , A) JP-A-58-163951 (JP, A) JP-A-58-158914 (JP, A)

Claims (1)

[Claims] 1. A chamber containing a substrate is provided with Si ₃ F ₈ , Si ₅ F ₁₂ , S.
gaseous form of at least one chain silicon halide compound selected from i ₆ F ₁₄ and Si ₃ Cl ₈ and a compound containing an element belonging to Group III or Group V of the Periodic Table and hydrogen An atmosphere is formed, and the chain silicon halide compound and the hydrogen are excited by utilizing light energy to form a deposited film containing silicon doped with the element on the substrate. Deposited film forming method.