JPS61295220A - Production of silicon - Google Patents

Abstract

PURPOSE:To produce an Si film which is uniform and dense inexpensively and easily with an electroless method by adding a reducing agent in a nonqueous solvent contg. an Si compd. CONSTITUTION:An Si film which is uniform and dense is formed on a base plate with an electroless method by adding a reducing agent in a nonaqueous solvent contg. an Si compd. incorporated in a reaction vessel. Still more as the nonqueous solvent, ethyl alcohol and ethylene glycol, etc., are used and as the Si compd., trichlorosilane and tetraethoxysilane, etc., are used and the concn. is nearly regulated to 0.2mol soln. - a saturated soln. Also as the reduc ing agent, alkali metal and alkali earth metal are used and the concn. is regulat ed to about 1-10 times quantities of the theoretical quantity necessary to deposit Si.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a method for producing silicon films, particularly silicon used for solar cells, electrophotographic photoreceptors, thin film transistors, various sensors, and the like.

(b) Conventional technology The methods for manufacturing silicon films used in these applications are as follows:
Conventionally, the following methods are known.

The first method is to generate silicon by plasma CVD using at least one selected from the group consisting of monosilane, disilane, and higher-order silane (S inH2n+z) as a silicon source, and argon, hydrogen, etc. It is.

The second method uses propylene carbonate, tetrahydro7rane,
This method involves dissolving helodenated silicon or halogenated silane in a polar organic solvent such as trimethyl-7-olumamide, adding an electrolyte if necessary, and electrolyzing this to electrodeposit elemental silicon onto the conductive cathode body. Yes (Unexamined Japanese Patent Publication No. 1973
-62135 publication).

A third method is to add a compound selected from the group consisting of silane, halogenated silane, halogenated silicon, or a mixture thereof in a non-aqueous neutral solvent or a mixed solvent of a non-aqueous neutral solvent and an aromatic solvent. At least one type of non-aqueous electrolytic composition is dissolved, a soluble electrolyte as a conductivity imparting agent is further added thereto, and this non-aqueous electrolytic composition solution is electrolyzed to electrodeposit a thin film containing silicon on the cathode body. be. (Unexamined Japanese Patent Publication No. 55-555
Publication No. 17).

(e) Problems to be Solved by the Invention However, in the first method, the amorphous silicon film IT display device is complicated and the initial cost is high, and the running cost for operating the device is also high. It has not been easy to mass produce Mole 77 silicon films.

In addition, the second and third methods above both produce an amorphous silicon film by electrolytic plating,
Although the equipment cost and running cost are low, and it is possible to easily obtain a large-area amorphous silicon thin film, on the other hand, as the current concentrates on the periphery of the substrate rather than the center,
There are disadvantages such as silicon growth in the central part of the base substrate is slow and slow compared to the peripheral part of the base substrate, the film thickness is uneven, it is impossible to form a dense film, and stable electrical characteristics cannot be obtained. there were.

(d) Means for Solving the Problems The present inventor has devised a method for efficiently depositing silicon in a non-aqueous solvent by an electroless method, contrary to the conventional theory that silicon cannot be deposited by an electroless method. As a result of many years of intensive research into methods of precipitation, we surprisingly discovered that amorphous silicon can be precipitated by placing an appropriate silicon compound in a non-aqueous solvent and using a strong reducing agent. This has led to the completion of the present invention.

That is, the present invention provides a non-aqueous solvent containing a silicon compound,
This method is characterized in that silicon is produced by an electroless method by adding a reducing agent.

The silicon compounds used in the present invention include silicon tetrachloride (SiC4'-), silicon tetrabromide (SiBr<), silicon tetrabromide (Sir), SiCIBr, S
i C12B r2, 5iCt'+Br, 5i
CIIs, S iC12I 2, S i C13I, 5
iBr=I, S 1Br212 and S 1BrI
3. Hexachlorodisilane (Si2c 1g), octachlorotrisilane (SimicoC1), decachlorotetrasilane (Si<CL.), dodecachloropentasilane (SisC4'+2), Tetofudekaku o o He14
5inXzn+z(n
is an integer of 1 or more, silicon halides such as Xl, tF, CI, Br or I), trichlorosilane (H8
iC1z), dichlorosilane (H28iCi2), monochlorosilane (H3S iC1),) dibromosilane (
HS iB ri), dibromosilane (H23iB r
2), Monobromosilane (Hx SiBr),)
riaiodosilane (H8iI=), noiodosilane (
H2SiI2) and monoiodosilane (H=SiI)
halogenated silanes such as silanes, and orthosilicate esters 1"%, each of which can be used alone,
Alternatively, two or more can also be used together.

The non-aqueous solvent is not particularly limited as long as it dissolves the silicon compound, and specific examples include ethyl alcohol, ethylene glycol, ether, propylene glycol, propylene carbonate, and ethylene di7. amine, dimethylsulf7oxidehydrazine, dimethylsulfoamide, oleumamidetrahydrofuran, tetramethylenesulfone, ethylene carbonate), N,N-nomethylacetamide, etc., and these may be used alone or in combination. More than one species can also be used together.

The reducing agent used in the present invention is not particularly limited as long as it has a strong reducing ability, and specifically includes alkali metals such as lithium, sodium, potassium, and cesium, berylum, magnesium, etc. , alkaline earth metals such as calcium, strontium, and barium, and their hydrides, lithium aluminum hydride, sodium borohydride (borohydride), hypophosphorous acid and its salts, etc. Among these, the non-aqueous solvents mentioned above Particularly preferred are substances that are well soluble in .

In carrying out the present invention, the concentration of the silicon compound in the nonaqueous solvent is not particularly limited and can be appropriately selected within a wide range, but generally any concentration from a 0.2 molar solution to a saturated solution is used. Although the amount of the reducing agent added is not particularly limited (crystals of the reducing agent may be present in the solution), it is necessary to precipitate silicon from the silicon compound used. NaJ!
1! *It is preferable to add 1 to 10 times the amount of t, and the reaction temperature can be arbitrarily selected from room temperature to the boiling point of the reaction composition liquid consisting of the above mixture. This reaction is
It may be carried out batchwise until a certain amount of the silicon compound is used up, or it may be carried out continuously so that the concentrations of the silicon compound and reducing agent are maintained constant.

The reaction tank used in the present invention is under an inert gas atmosphere such as nitrogen, helium, or argon in order to prevent the reaction between the silicon compound and moisture and the volatilization of the silicon compound.
A closed type is used.

In a preferred embodiment of the present invention, silicon is produced on a substrate, and a thin film (plating) of silicon is produced on the substrate, whereby 7 mol 77
can produce silicon films.

The above substrate may be a plate or foil of metal such as nickel, copper, molybdenum, stainless steel, titanium, or gold, and the surface may be made of nickel, copper, palladium, palladium (1 substance, etc.) and/or tin oxide, inzoum oxide, or a mixture thereof. A glass plate, a graphite plate, or a plastic film or plate coated with a transparent conductive oxide film is used.

The above reaction (plating) is started after the surface of the above substrate is treated in advance with a catalyst such as palladium and/or a palladium compound, the treated substrate is immersed in the above reaction composition solution, and the temperature is adjusted. However, in the reaction composition solution described above, the substrate is used as a cathode and an insoluble anode such as a platinum plate is used as a counter electrode, and the substrate is activated by applying electricity for a short time (1 to 5 seconds) using a DC power source. It is economical to allow the reduction reaction to proceed smoothly (hereinafter referred to as electrolytic activation method).

In the case of the electrolytic activation method, it is preferable to have an electrolyte present in the reaction system in order to improve conductivity.

As an electrolyte, perchlorate such as lithium, sodium or potassium, tetrabutylammonium perchlorate,
Tetrabutylammonium bromide or the like may be used alone or in combination.

The amount of the electrolyte added varies depending on the type of electrolyte and solvent used, but it is preferably set so that the electrical resistance of the reaction system is minimized. .5 to 10% by weight is preferable.

In addition, the conditions during electrolysis are usually 0.1-3mA/ca+",
Electrolysis is preferably carried out at 0.2 to 0.5 mA/cm'', and the electrolysis temperature can be arbitrarily selected from the above-mentioned range.

The electrolytic cell is not particularly limited as long as it is stable with respect to the above reaction solution and has a sealed structure filled with an inert gas such as nitrogen or argon. For example, it may be box-shaped or beaker. A type electrolytic cell may also be used.

(e) Effect In the present invention, silicon is produced by reducing a silicon compound with a reducing agent, and the characteristics of silicon can be changed or the reaction rate can be changed depending on the silicon compound and reducing agent used, as well as the reaction temperature. Very easy to adjust.

In particular, in the embodiment of the present invention, when forming a silicon film on a substrate, silicon is produced by reducing a silicon compound with a reducing agent, and is not performed by an electrolytic reduction method. It is possible to form a uniform and IIk dense silicon film without variations in the silicon film in the peripheral area.

(f) *Examples The present invention will be explained in more detail by examples below.
The present invention is not limited to this.

Example 1 A Teflon-lined stainless steel sealed reaction tank with a lid having a capacity of 31,130 ml was equipped with a platinum-plated titanium net as an anode and a thick titanium net as a cathode. ! -0.11 titanium plates (3 cm x 3 am) are attached at intervals of about 0.5 cm, and a thermometer and a reflux condenser are also attached.

Into the reaction tank, 100 tall of propylene carbonate, which had been dried with molecular sieves and purified in advance by vacuum distillation, was added.
2.7 g of trichlorosilane, 5 ammonium hypophosphite
．． 4g and tetra-n-butylammonium chloride 2.0
Add each g. Next, cover the lid and heat it from the outside.78
A constant current condition (cathode current density 0.5+aA) was applied between the above two electrodes at ~80°C while stirring with a magnetic cooler.
/ 0 m2), and electricity was applied for 1 second to start the reaction. After that, the power was turned off and the titanium plate was taken out after being kept at 78 to 80°C for 120 minutes, and a dark brown silicon film was obtained on the titanium plate.

The above reaction was carried out in a nitrogen atmosphere using a commercially available glove box in an environment where the intrusion of moisture was prevented as much as possible.

When the above silicon film was examined by X-ray fluorescence analysis and mass spectrometry, it was found that the main component was silicon, with traces of chlorine.
It was found that the film contained phosphorus and had a uniform thickness of 3 μm over the entire surface of the titanium plate.

Furthermore, as a result of X-ray diffraction, this silicon film was found to be amorphous, and thermal analysis revealed that it contained about 20 atomic percent hydrogen.

Example 2 A silicon film having a thickness of approximately 2 μm was obtained in the same manner as in Example 1 using the following reaction composition and substrate.

Ammonium hexafluorosilicate 3.6g Ammonium hypophosphite 5.4g Tetrabutylammonium perchlorate 3.4g 7 Orumamide
50 Ugly! Isopropyl alcohol
50m1 substrate Molybdenum plate (thickness 0, 1 mm) Reaction start (electrolytic activation method) (Cathode current density 0.5 mA / am 2.5 seconds) Plating temperature 78-80℃ Plating time
When this silicon film was analyzed for 60 minutes in the same manner as in Example 1, it was found that the silicon film was an amorphous silicon film containing traces of fluorine and phosphorus, and further containing about 10 atomic percent hydrogen. Admitted.

Example 3 A silicon film having a thickness of about 1 μm was obtained in the same manner as in Example 1 using the following reaction composition and reaction conditions.

Tetraethoxysilane 4.2g Ammonium hypophosphite 5.4g Acetic acid
5oIl11 Ethyl alcohol 50I111 Substrate (palladium treated (Note 1)) Copper foil (thickness 0.035+a+a
) Reaction temperature: 78 to 80'C Reaction time: 40 minutes When similar analysis was performed on this silicon film, the silicon film had the following properties.
It was found that the film was an amorphous silicon film containing traces of palladium and phosphorus, and also about 20 atomic percent hydrogen.

(Note 1) Palladium-treated palladium chloride (P dC12.2 H20) 2 g
and 100mj of ethyl alcohol! Copper M (
The substrate was immersed for 1 minute and then dried with hot air.

Example 4 A silicon film with a thickness of about 3 μl was obtained in the same manner as in Example 1 using the following reaction composition and reaction conditions.

Silicon tetrachloride 3.4g Sodium hypophosphite 2.7Fl Tetra-n-butylammonium chloride 2.8g Tetrahydro7um 100mZ substrate
Platinum M (thickness 0.05mm) reaction temperature
Reaction started at 78-80°C (electrolytic activation method) (Fii electrode current density 0.2 mA/c theory 2.3 seconds) Reaction time 40 minutes This silicon film! When the same analysis as in Example 1 was performed, it was found that the silicon film was an amorphous silicon film containing traces of chlorine, sodium, and phosphorus, and about 15 atomic percent of hydrogen.

Example 5 A silicon film having a thickness of about 1 μm was obtained in the same manner as in Example 1 using the following reaction composition and reaction conditions.

Tetraethoxysilane 4.2g Lithium metal o, sg Tetra-chloride
n-butylammonium 2,0°0-hebutane
50ml ethyl alcohol
50m1 substrate titanium plate (thickness 0.111-) reaction temperature
Reaction started at 50-60°C (electrolytic activation method) (Cathode current density 0.2mA/cs+'', 3 seconds) Reaction time 60 minutes When this silicon film was analyzed in the same manner as in Example 1, traces of glue and approx. It was confirmed that the film was a silicon amorphous film containing 10 atomic % of hydrogen.

Example 6 A silicon film having a thickness of approximately 1 μm was obtained in the same manner as in Example 1 using the following reaction composition and reaction conditions.

Tetraethoxysilane 4.2g Magnesium 1.2g Tetra-bromide
n-butylammonium 3.2g propylene carbonate
50ml ethyl alcohol substrate Titanium plate (thickness 0.1mm)
Reaction temperature: 50-60°C Reaction start (electrolytic activation method) (Cathode current density: 0.2 A/c for 2 to 3 seconds) Reaction time: 110 minutes on this silicon film! & When the same analysis as in Example 1 was conducted, approximately 1
It was confirmed that the film was a silicon amorphous film containing 0 atomic % of hydrogen.

Example 7 A silicon film having a thickness of about 0.5 μm was obtained in the same manner as in Example 1 using the reaction composition and reaction conditions described below.

Silicon tetrachloride 3.4 g Sodium hydride 2.4 g Propylene carbonate 100 wheels (palladium treated (see note 1 above)) Copper foil (thickness 0.035
-1) Reaction temperature: 80-90°C Reaction time: 20 minutes When this silicon film was analyzed in the same manner as in Example 1, it was found to be an amorphous silicon film containing traces of sodium and chlorine and about 10 atomic percent hydrogen. was recognized.

Example 8 A silicon film with a thickness of about 1 μm was obtained in the same manner as in Example 1 using the following reaction composition and reaction conditions.

Tetraethoxysilane 4.2g Lithium aluminum hydride 3.8g Tetrahydro 7 run 100 Ugly substrate Approx. 0.05
A lath plate with a thickness of 0.5I coated with a μ- indium oxide film, further treated with palladium (see Note 1 above).

When this silicon film was analyzed in the same manner as in Example 1 at a reaction temperature of 65° C. and a reaction time of 100 minutes, it was found that it was an amorphous silicon film containing about 15 at. % of hydrogen.

As shown in the above examples, silicon amorphous films having different thicknesses and hydrogen doping ratios can be produced extremely easily by changing the reaction composition and reaction conditions.

(g) Effects of the invention Since the present invention generates silicon by reducing a silicon compound with a reducing agent, the manufacturing equipment is simple and the equipment cost is low, and the running cost is low compared to the plasma CVD method. It is very inexpensive, and the properties of the silicon film can be changed extremely easily by changing the reaction composition and reaction conditions.

Furthermore, since the present invention generates silicon by reducing a silicon compound with a reducing agent, an electrode is not necessarily required unlike the electrolytic reduction method, and therefore silicon can be deposited in a reaction tank. As a result, post-processing such as recovery and purification of silicon can be easily performed.

Furthermore, in the embodiment of the present invention, when forming a silicon film on a substrate, silicon is produced by reducing a silicon compound with a reducing agent, so a uniform and dense film is formed over the entire surface of the substrate. It has unique effects such as:

Claims (6)

[Claims] (1) A method for producing silicon, which comprises adding a reducing agent to a non-aqueous solvent containing a silicon compound to produce silicon by an electroless method. (2) The method for manufacturing silicon according to claim 1, characterized in that the silicon is produced on the surface of a substrate. (3) The method for producing silicon according to claim 2, wherein the surface of the substrate is pretreated with palladium and/or a palladium compound. (4) The silicon compound is trichlorosilane, ammonium hexafluorosilicate, tetraethoxysilane,
Claim 1 characterized in that it is at least one member selected from the group consisting of silicon tetrachloride.
3. The method for producing silicon according to any one of items 3 to 3. (5) Claim 1, wherein the reducing agent is at least one selected from the group consisting of alkali metals, alkaline earth metals, their hydrides, lithium aluminum hydride, hypophosphorous acid, and salts thereof. The method for producing silicon according to any one of items 1 to 4. (6) Claims 1 to 5 characterized in that the generation of silicon is started by applying electricity for a short time.
A method for producing silicon according to any one of paragraphs.