JPS5978919A - Formation of amorphous silicon film - Google Patents

Abstract

PURPOSE:To increase the growing speed of an amorphous silicon (a-Si) film without deteriorating the characteristics of the film in the manufacture of an a- Si film by a chemical vapor deposition (CVD) method by adding a specified amount of ammonia (deriv.) to a gaseous starting material. CONSTITUTION:Ammonia (deriv.) represented by formula I and/or hydrazine (deriv.) represented by formula II is used. In the formulae each of R<1>-R<7> is H, alkyl or aryl. A substrate is placed in a decomposition furnace, silane of higher order represented by formula III (where n is >=2) such as disilane or trisilane is introduced into the furnace optionally together with an inert gas such as nitrogen, and the silane is thermally decomposed at about 250-600 deg.C to deposit an a-Si film on the substrate. At this time, said ammonia (deriv.) and/or hydrazine (deriv.) is added to the silane by an amount satisfying relation represented by formula IV [where N is the amount of nitrogen in the ammonia (deriv.) and/or hydrazine (deriv.), and Si is the amount of silicon in the gaseous silane].

Description

[Detailed description of the invention] The present invention is based on the general formula 5inHzn+2 (where n is n≧2
An amorphous silicon film (hereinafter referred to as a
The present invention relates to a method of forming a -8i film (referred to as a -8i film), and more specifically to a method of increasing its formation rate (growth rate) without deteriorating the film properties.

Since the a-Si film has excellent photoelectric properties,
Used in solar cells, photoreceptors, thin film transistors, optical sensors, etc. However, one of the methods for manufacturing the a-8i film is
The so-called chemical vapor deposition method (01+Cmical Vapor Deposition) involves thermally decomposing a gas such as silane and depositing it on a substrate.
OVD (hereinafter abbreviated as OVD) is widely used for forming a-Si films. However, when this is put into practical use, the productivity is insufficient, and attempts have been made to apply higher energy in CvD in order to improve productivity. However, a'
When energy above a certain level is applied in the process of forming an S+ film, the film formation rate is reduced, but the properties of the resulting film often deteriorate significantly.

As a result of intensive study in view of the above points, the inventors found that C.
Ammonia (derivative) in higher silane gas in VD
The present inventors have discovered that the growth rate can be increased by at least 2 times, usually 5 to 6 times, without deteriorating the properties of the film, by adding the following, and have completed the present invention.

That is, according to the invention, the general formula S i n Hzn
+2 (where n represents an integer of n≧2), when thermally decomposing the high-order silane gas and depositing it on the substrate, the formula (I) 1 I73 (in the formula, R1, R2, all represent a hydrogen atom, an alkyl group, or an aryl group) Ammonia (derivative) and/or formula (11) , or an aryl group), with 0.01≦N/Si (gram-
Atom ratio) < 0.2 (Here, N indicates the amount of nitrogen in the ammonia (derivative) and/or hydrazine (derivative) brought into the thermal decomposition system, and Sl indicates the amount of silicon in the higher silane gas.) 1. A method for forming an amorphous 7-recon film, characterized in that the amorphous 7-recon film is made to exist.

is provided.

The present invention will be explained in detail below.

The higher order silane in the present invention has the general formula 5inl-1zr+
+z (where n represents an integer of 11≧2), such as disilane (S12II6), trisilane (S i3 H8), tetrasilane (Si*1
1+o), pentasilane (S 15Hu ), hexasilane (S i6 H14), etc., but disilane, tridilaf, and tetrasilane are preferred from the viewpoint of ease of handling. These may be used alone or in mixtures.

In addition, when using a high-order silane as a mixture, it goes without saying that a small amount of mono-7 run (5iH4) may be contained. However, when only monosilane is used instead of higher-order silane, the film growth rate hardly increases even if ammonia (derivative) or the like is added, and the object of the present invention cannot be achieved.

The present invention uses such high-order silane as a raw material to form an amorphous silicon film on a substrate by a thermal decomposition method known per se. At this time, ammonia (derivative) and/or hydrazine (derivative) are thermally decomposed. Add to reaction system.

The ammonia (derivative) used in the present invention is represented by the formula (1), t1 R,8 and t7. R1, 1t2, n, "Hydrogen; methyl, ethyl, -propyl, n-propyl, 1-butyl 1sec-
Alkyl groups such as butyl, n7” tyl, pentyl; aryl groups such as phenyl, tolyl, xylyl, naphthyl, etc. Examples of ammonia (derivatives) of formula (1) include:
Ammonia, methylamine, dimethylamine, trimethylamine, ethylamine, dimethylethylamine, diethylamine, triethylamine, i-7'-pyramine, n-7'-pyramine, aniline, N-methylaniline, N,N-dimethylaniline, toluidine, xylidine , benzylamine, diphenylamine, naphthylamine, etc.

In addition, hydrazine (derivative) is represented by the formula (II), and R4, n, f', R6, and R7 in 1, . / \□. are hydrogen; methyl, ethyl, i-propyl, n Alkyl groups such as -7'lopyl, i-7'thyl, 5ec-butyl, n-butyl, and pentyl; aryl groups such as phenyl, tolyl, xylyl, and naphthyl.

Examples of hydrazine derivatives of formula (n) include hydrazine, methylhydrazine, ethylhydrazine, i-propylhydrazine, phenylhydrazine, benzylhydrazine, naphthylhydrazine, N,N'-dimethylhydrazine, N,N'-diethylhydrazine, N-methyl-N
'-phenylhydrazine, N,N'-diphenylhydrazine, and the like.

Among these, ammonia is most preferred in terms of ease of handling and its effects.

In addition, ethylenediamine, ethanolamine,
Jetanolamine, triethanolamine, Feni 1
Nitrogen compounds such as diamine, nitroaniline, etc. can also be used.

The amount of nitrogen N (Daramoor atom) in ammonia (derivative) and/or hydrazine (derivative) added to the thermal decomposition system and the amount of silicon Si (gram-atom) in the raw material higher order silane gas are 0.01≦N / Si (0 , 2. It is necessary to satisfy the following relationship.N/S i
is less than 0.01, the growth rate of the film will not be sufficiently high. Moreover, when N/S i is 0.2 or more,
The growth rate of the film is on the same level as that of a blank without addition of ammonia or the like, or in some cases is even lower.

In the present invention, the pyrolysis pressure may be any pressure including reduced pressure, normal pressure, and atmospheric pressure.

Note that it is advantageous that the film growth rate is originally high if thermal decomposition is performed at a pressure higher than atmospheric pressure, but in that case, 2 K
The object of the present invention can be sufficiently achieved within the range of g/cnl G or less. Of course, there is nothing wrong with operating under pressure greater than this.

Further, the thermal decomposition temperature in the present invention requires a substrate of 250 C, and hydrogen is difficult to be injected into the a-8i film, making it impossible to obtain sufficient characteristics. In order to obtain sufficient properties, post-treatment to incorporate hydrogen is necessary. However, if the temperature is less than 250C, the decomposition rate of higher-order silane is slow, and the growth rate of the a-Si film becomes unsuitable for practical use.

As an apparatus for carrying out the present invention, for example, the apparatus shown in FIG. 1 can be used.

It is a glass tube. This may be a rectangular shape (duct) instead of a pipe. The reaction tube has a heater 2 such as a halogen lamp around the outside.
0. The part inside the tube corresponding to the heater is a decomposition zone, and a silicon susceptor 30 (supporting stand) and a substrate 40 made of quartz glass, silicon, S/F, SUS, etc. are set on the susceptor. The temperature in the decomposition zone is measured by a thermocouple 45.

One end of the reaction tube is a source gas supply section 5o, which is connected to a piping section for gases 80 such as silane gas 60, carrier gas 7o, and ammonia (derivative). 61.71.8
1 is a valve, and 63, 73, 83 are gas flow meters. Further, the other end of the reaction tube is an outlet section 90 for exhaust gas.

Naturally, the heater 20 is not a lamp heating type,
A resistance heating type that heats the entire reaction tube may also be used.

In addition, ammonia (derivatives) etc. are ammonia,
In the case of gaseous substances such as methylamine or substances that can be easily gasified, they can be supplied as a gas alone through piping in the same way as 7 run gas, but liquid substances with a slightly higher boiling point such as hydrazine and aniline can be supplied with N2. , N
Bubbling carrier gas such as e (not shown)
It is preferable to carry out a dissipation operation and to entrain the carrier gas and supply it to the pyrolysis system.

Next, to explain the decomposition operation, the temperature of the decomposition furnace is raised to above the decomposition temperature, nitrogen gas is flowed to perform the baking operation, and then the temperature is lowered to the decomposition temperature and the temperature is stabilized at 250 to 500C. After that, the high order/run 100%, or the one diluted with an inert gas such as nitrogen, helium, argon, hydrogen, etc. to about 0.1 to 20%, and ammonia (derivative), etc., are used as they are, or the above The high-order silane gas is supplied together with an inert carrier gas to a decomposition furnace set at a decomposition temperature of 250 to 600 C, and the high-order silane gas is thermally decomposed to deposit an a-8i film on the substrate.

The present invention will be specifically explained below using Examples.

The a-Si films obtained in the following examples were analyzed and evaluated as follows.

(1) Dark: Prior to photoconductivity measurement, a gate electrode was attached to the a-Si film to be measured by vacuum deposition to obtain ohmic characteristics. The voltage-current characteristics were measured using a diffraction grating spectrometer manufactured by JASCO ■0'J)
-50.

Dark conductivity is when light is blocked, photo conductivity is 2e■, 3
This is a case where the sample is irradiated with light of 1014 photons perpendicularly.

(2) Hydrogen content and infrared absorption It was determined based on the integrated intensity of the infrared absorption coefficient. The infrared spectrometer used was JASCO Model H-202.

At the same time, from the infrared absorption spectrum, 5i-H and Si-N
The infrared absorption of the stretching vibration of 2 was determined.

(3) Heat resistance The a-Si film was exposed to N2,1 using the equipment shown in Figure 1.
Thermal annealing is carried out for 1 B@ while flowing a carrier gas such as No. 12, and the hydrogen desorption rate is displayed at a temperature exceeding 10 times the original hydrogen content.

(4) Film Thickness Depending on the film thickness, the thickness was determined using a combination of gravimetric method, method using surface roughness meter, and method determined from interference using transmittance. The film growth rate (X/#n) is calculated from this film thickness and thermal decomposition time.

(5) Activation energy of conductivity Dark conductivity was measured in a heated range from room temperature to 20 Or, and was determined according to the Arrhenius formula.

(6) Optical bandgap Measured using a Japan Spectroscopy 0T-50 diffraction grating spectrometer. The absorption coefficient was determined from the transmittance, and the point where the linear part of the absorption coefficient curve was extended and intersected with the photon energy was defined as the optical band gap.

Example 1 The apparatus shown in FIG. 1 was used as an experimental apparatus (reaction tube: 40 mmσ x 600 mt).

Raw material gas 5 containing 5% 5iJI6 diluted with N2 gas
00 cc/” Gas containing 10% ammonia diluted with K 142 10 cC/min (N/5i=0
．． 02) and using N2 gas as a carrier gas (
Flow rate 1ooocc/=), pressure 1.0Kg/crd −
The mixture was poured into a decomposition furnace at 400 t:' for 30 minutes. The results are shown in Table 1.

Examples 2 to 7 Experiments similar to those in Example 1 were conducted under the conditions shown in Table 1. The results are summarized in Table 1.

Comparative Examples 1 to 6 Experiments similar to those in Example 1 were conducted under the conditions shown in Table 2. The results are summarized in Table 2.

Claims (1)

[Claims] 1 General formula S group H2n + 2 (here, 11 is 11≧2
In order to thermally decompose the high-order 7-lane gas produced by the formula (1) (indicating an integer of ammonia (derivative) and/or / ＼□7 5 (in the formula, 几4, R5, 几6, 几7 represent a hydrogen atom, an alkyl group, or an aryl group) 0.01≦N/Si (gram-
atom ratio) (0,2 (where N is ammonia (derivative) and/or hydrazine (
1. A method for forming an amorphous silicon film, characterized in that Si indicates the amount of nitrogen in the derivative), and Si indicates the amount of silicon in the higher-order silane gas.