JPS59224119A - Preparation of coating - Google Patents

Abstract

PURPOSE:To improve an ionization rate by packing a trivalent or pentavalent impurity into a bomb at a specific rate to silane. CONSTITUTION:When silane, which is associated or is under the state of association, is formed in a bomb, a trivalent or pentavalent impurity, such as diborane, phosphine or arsine is mixed simultaneously into the bomb by 100PPM-10mol% to silane. The bomb is brought so as to satisfy the relationship of NXP>=300 when the concentration of a silicide such as silane is N% and pressure in the bomb Pkg/cm<2>. The impurity is distributed homogeneously into clusters, and the centers of acceptors or doners can be completed at an ionization rate of 98- 100%.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves filling a single or heptavalent impurity element and silane into the same cylinder, and then injecting polysilane (Six
Hy x≧2. y≧4), or a high-pressure container (
regarding cylinders).

In the present invention, when a cylinder is filled with silane, particularly monosilane, in a polysilanization reaction or an associative silanization reaction, an inert gas such as helium is used as a diluent gas for the silane or the silane, and the cylinder internal pressure (P (Kg/c+a )
) and the silane concentration (N (%)). The purpose is to promote multiple or associated states of polysilanes or associated silanes.

The object of the present invention is to chemically activate, decompose, or react using such a high-pressure container, and then form a film of silicon or a silicon compound (mixture) on the material to be formed.

The present invention provides such a coating with a structure in which massive clusters are superimposed, and the clusters may be amorphous or semi-amorphous depending on the case.
i amorphous quas this semi-amorphous
i-amorphous, Sem1-crysta
The purpose of this study is to fabricate a coating of crystals (which may also be referred to as Quasi-crystal or Quasi-crystal).

Conventionally, silane was monosilane (Sill+ boiling point 2℃
It was believed that polysilane (SixHy x≧2.y≧4), which has a melting point of -185"C) and has multiple bonds of silicon hydride (SixHy x≧2.y≧4), is unstable and does not actually exist.

Furthermore, since monosilane is a gas and its molecules are spaced apart from each other, it was considered most appropriate to write it as 5il14.

However, Kien disciples do not generally understand that silane is a silane, but in certain special conditions, that is, under high pressure, it tends to turn into polysilane or associated silane, and at room temperature or near room temperature (generally below 100 degrees Celsius), it tends to turn into polysilane or associated silane. It was found that 100 blades of silicon polymerize or associate with each other. In addition, it has been found that these polymerized or associated molecules are even more preferable in coatings prepared by laminating massive clusters as in the present invention.

In particular, the coating should be kept at temperatures below 700°C, which is the crystallization temperature of silicon, especially at 5°C.
When forming an amorphous semiconductor (hereinafter referred to as S) or a semi-amorphous semiconductor (hereinafter referred to as SAS) at a temperature of 00°C or lower, the film is formed into a structure in which massive clusters are overlapped (stacked). I was able to do that. In particular, unlike polycrystalline semiconductors with clear boundaries, which are formed at temperatures above the crystallization temperature, these massive clusters do not necessarily have clear grain boundaries, and interface states are concentrated at these grain boundaries. 6 Furthermore, when silane and diborane or phosphin diluted with hydrogen, etc. are mixed in a doping system, which has been done in the past, the silane is already in an associated state.
Boron or phosphorus is bound (combined) only to the outside of the cluster
This is not possible, and boron or phosphorus is distributed non-uniformly in the microscopic area. That is, in the formed film, many impurities are concentrated around the clusters and are substantially unevenly distributed locally in the silicon film. For this reason, the so-called ionization rate Np - acceptor concentration / added boron concentration, in which they act as acceptors or donors, is 3 to 30.
% is low.

However, on the other hand, when diborane or phosphin is added to the cylinder at the same time as silane as in the present invention, the ionization rate Nn of phosphorus acts at 98 to 100%, and the ionization rate of boron also increases by an order of magnitude to 95 to 99%. It became possible to improve the ionization rate.

In the present invention, when silane is formed in an associated or associated state in a cylinder, an m-valent or V-valent impurity such as diborane, phosphine, or arsine is simultaneously added to the cylinder at a concentration of 1100 PP per silane (1100 PP per volume of silane).
00/10'' times the volume) to IO mol% (10% volume relative to the volume of silane).Then, the impurity is homogeneously distributed inside the cluster and the acceptor or donor center has an ionization rate of 98 to 100%. This is extremely effective considering that when a cylinder of M-valent or ■-valent impurity and a cylinder of silane are mixed immediately before introduction into the reaction system, the ionization rate is 3 to 30%. The effect was excellent.

The present invention will be described in detail below with reference to the drawings.

Example 1 A conductive substrate or an insulating substrate was used as a substrate having a surface to be formed.

In FIG. 1, the substrates (15) had a thickness of 200 to 1000 μm and a maximum size of 10 cm, and were arranged on a quartz board (14). It was formed parallel to the gas flow.

This reaction tube uses induction energy with a frequency of 0.1 MH2 to 10 GHz, and is typically 50ONI.
Iz.

13.56M'6.2.45GH2. Figure 1 is 1
A high frequency of 3.56 MIIz was used. Inductive energy is supplied by a capacitive coupling method, and a pair of electrodes <2>, (3
) so that the entire reaction tube (1) was uniformly discharged. Furthermore, this discharge is performed by providing an activation chamber (1) for a reactive gas at a position away from the surface to be formed, and polymerized or associated silicide gas such as polysilane or associated silane is activated by electromagnetic energy (induction energy) in the activation chamber (1). ) to chemically activate, decompose, or react, and further proceed with this process while in flight, and form a film by laminating massive clusters randomly on the substrate (15). The reactive gas is silane in a polymerized or associated state (Sixty x≧2
When y≧4, m5tl+4) is added from (7), and 1100PP to 10 mol% of a valent impurity gas such as diborane (B, )l) is mixed into the silicide gas at the same time. A bong diluted from 0 to 97% was connected to (8). Regarding the V value, phosphorus, arsenic, and antimony were similarly added to the silicide gas using phosphin (pH, ), arsine (8sH3>, and stibine (Sbtls)) and then added to the silicide gas using a tie between 0 and 9.
It was diluted 7% and connected to (9).

Further, as a fluoride gas, for example, SiF4 (silicon fluoride) was added into the cylinder to form a fluoride gas of silicon in the cylinder.

The reaction tube was made sufficiently thick to reduce the influence of the tube wall, and its outer periphery was cooled with water to prevent nucleation from forming on the wall.

This is very different from the reduced pressure vapor phase method, which makes the temperature of the wall surface exactly the same as the temperature of the substrate, and actively tries to make the polycrystalline silicon formed on the wall surface adhere to the substrate surface.

The substrate (15) is heated by resistance heating (6) and the reacted gaseous and elemental products are passed through a needle valve (10);
Stop valve (11), vacuum rotary pump (12)
) and then exhausted (13).

The reactive gas used is primarily a silicide gas, in which the silane is reacted with an inert gas such as helium in a bomb.
Diluted to 0-3%. Of course, 100% silane may also be used.

The reaction system (furnace (5) or activation chamber (1)) is 10-yo~
A pressure of 10 torr, particularly 0.005 to 5 torr, was adjusted by introducing and evacuating reactive gas. generally 50
1 to 20 torr at 0KHz and 0.1 to 3 torr at 13.56MHz.

For 2.45 GII2, 0.005 to 0.1 torr was optimal.

In the present invention, the pressure inside the cylinder will be described later in FIG. 3, but when the concentration of silane is 10 to 50%,
g/an! (10%) to 7 Kg/-(50%) or more, particularly preferably 50 to LO Kg/c♂ or more.

Then, the monosilane molecules were decomposed in the cylinder and subjected to a polymerization reaction with each other to obtain a polymer, or the monosilane molecules were made to associate with each other through hydrogen bonds (hydrogen bonds) to form an associated silane.

This polymerized or associated silane aggregates during activation in the reaction system, even though it is in the gas phase, forming so-called semi-crystalline massive clusters that promote more stable crystallization. It was extremely effective. For this reason, in order to encourage multiple or associative conditions within the cylinder,
Hydrogen is unsuitable as a carrier gas because it tends to rehydrogenate dangling bonds generated by decomposition of silicon, and an inert gas, particularly helium (lie), is extremely preferred. Ile has an ionization voltage of 24.57 eV, which is higher than the 10 to 15 eV of other commonly used diluent gases, and a thermal conductivity coefficient of 0.123 Kcal/mug 'C, which is about three times that of other gases. This was advantageous for improving the uniformity of the formed layer coating.

The reactive gas and the substrate were heated in a heating furnace (8) from room temperature to 700°C. As is clear from the drawings, the reactive gas was placed on the supply source side (the cylinder side) away from the substrate by the induction energy, and all the reactive gases were excited or activated and decomposed by the induction energy. The activated product was also heated from room temperature to 200'C if necessary. In this manner, the activated or decomposed reactive gases coagulated and associated with each other. In terms of physical properties, they coagulate with each other to form a plurality of clusters in which silicon is active in the reactive gas.

Furthermore, since the activated clusters were formed into a film on the substrate, some of the hydrogen was separated, and it was possible to form flat or hemispherical clusters overlapping each other on the substrate. For this reason, these flat or hemispherical clusters seek a stable state within the energetically possible range during flight, so the distance between electrons varies widely, and the coordination of the atoms is not stable. It turns out that it has a direction (angle). As a result, the electron microscopic diffraction photograph of the film thus formed was a mixture of a halo indicating an amorphous structure and a spot or linear ring-shaped semi-regular image indicating a crystallized structure.

Figure 2 (A >, < B ) summarizes the process of forming silicon clusters on a substrate from silane in the above reaction process, (B) shows the reaction process of polysilane, and (A)
shows the reaction process of associated silanes.

That is, in state ①, m silanes such as monosilane (
m (Sjll, p) ) is activated (m
(Sillf) ), m (Sillzs:)
＞, further decomposition or reaction occurs in state ■, resulting in an active cluster (clump) 54mH4z+ or S i
nIltw%1. Here m.

n, m, and n represent arbitrary constants, Si indicates that the St bond is in an active state, and Sili'' indicates that the S J-II bond has energy and is activated. The S
Hydrogen mainly gathers around the i-cluster (16) to form a shell (17) state. Further, in step (3), clusters (20) are formed into a flat or hemispherical film on the substrate (15).

For this reason, the outline around this cluster was not necessarily clear, like that of a superheavy polycrystal, and was rather blurry under electron microscope observation.Furthermore, the size and shape of the cluster also depended on the pressure of the cylinder (reactivity). initial state of gas),
It is greatly affected by the frequency of induction energy, flight time due to power, pressure, and substrate temperature.

However, when examined under a transmission electron microscope (TEM), the mass had a diameter of 100 to 10 microns, was generally circular, and had no sharp edges. Since such clusters (20) are stacked one after another on the substrate, they also overlap each other.

For this reason, state (2), which is the process of film formation, rather disturbs the crystallographic regularity, and even though the initial state of the reactive gas and the association (agglomeration) during activation and flight are in the gaseous state. Regardless, the present invention is characterized by promoting crystal-like regularity, particularly regularity in the coordination direction.

Furthermore, each cluster formed into a film has a thickness of 5~
It has 500 people and its effective diameter is 1()0 people to 10.0
μ in the experimental results.

In addition, the higher the cylinder pressure of silane or a gas made by diluting silane with an inert gas in the helium, for example, when the concentration of silane is 3%, 10%, 50%, or 100%, the cluster becomes more As shown in Figure 3 curve (22), 100 atm (atmospheric pressure or Kg/cJ), 30 atm, 6 atm, and 2 atm, respectively from the so-called general curve (21) of 30 atm, 10 atm, 2 atm, and 1 atm. By applying high pressure, it was possible to easily form clusters and make them larger. Furthermore, this pressure is increased to 150 atm and 5 atm, respectively, as shown in curve (23) in Figure 3.
When the pressure was set to 0 atm, 10 atm, 5 atm or more, the clusters formed could be increased 2 to 5 times to 3000 to 10 microns.

When the carrier gas is hydrogen, it is difficult to form clusters, and even with a weak electrical energy of 10 to 20 degrees of induction energy, the result is a damaged amorphous structure with many recombination centers due to the sputtering effect.

Furthermore, it has been found that if the temperature is lower than the conventional 200-550°C, the crystallinity within the cluster becomes amorphous, and the thermal energy during flight is also important.

In the present invention, as impurities of P or N type conductivity, diporan and phosphin are added simultaneously to the same cylinder as silane at a predetermined concentration. In this way, when creating a multiple or associated state in the cylinder, boron or phosphorus could be added homogeneously to the inside (bulk) of the mass.

Although this method of the present invention has the disadvantage that the conductivity of P or N type in the formed semiconductor film cannot be freely controlled, it is preferable to fill the same cylinder when the conductivity is always the same as in a mass production line. It has the characteristic of being easy to operate.

For this reason, P-type, I-type, and N-type semiconductor films are stacked to form a P
When trying to make an N junction, PI junction, or N1 junction, in the conventional method, even if 1 to 5 mol% of B or P is added, 10
” ~10' (2cm (electrical conductivity 10'4 ~ 10
Although it has a specific resistance of ``2 (Ωcm)'), in the present invention, even at 0.1 to 1 mol%, it has a specific resistance of 10 to 0.1 Ωc.
m (electrical conductivity 0.1 to 10 (Ωcm)″).

In particular, the fact that the same electrical conductivity can be obtained by reducing the amount of impurities added means that unnecessary impurities, that is, carriers, exhibit impurity scattering, lowering their mobility, and
Furthermore, it is possible to reduce the degree to which impurity recombination centers form and become carrier killers, making it extremely preferable as a semiconductor material.

Furthermore, in the present invention, a gas phase reaction is caused by mixing silane to which diporane, phosphine, or arsine is added, and ammonia, which is a nitride gas, oxygen, which is an oxide gas, or methane, which is a carbide gas.
(0 < x < 4), 5tO2-, (Q < x < 2
), 5ICx (0 < x < 1) and its energy band width is 1.2~l, not 7eV, and further 1.6~3. It is effective to make P- or N-type semiconductors or semi-insulators with OeV increased proportionally to its N, O or C addition.

It goes without saying that the present invention is effective not only for semi-amorphous films but also for amorphous semiconductor films or semi-insulator films.

Note that when the pressure inside the cylinder was maintained for a long period of 1 to 6 months, the state of polymerization or association gradually progressed over time, and the size of the lump-like clasphs formed increased by 3 to 10 times. In addition, the pressure in the present invention refers to the pressure when the cylinder is filled or the maximum pressure of the cylinder, and if the reactive gas in the cylinder is used after filling, the pressure will decrease.
Needless to say, in this case, a gas such as a silicide is obtained from the cylinder, in which impurities which are polymerized or associated impurities, which are reaction products produced by a reaction in the cylinder in the past, are sufficiently mixed.

[Brief explanation of the drawing]

FIG. 1 shows a schematic diagram of a reaction apparatus for producing a semiconductor film used in the present invention. FIG. 2 shows the reaction process of the present invention. FIG. 3 shows the relationship between the internal pressure of the cylinder and the concentration of silicide gas according to the present invention.

Claims (1)

[Claims] 1. Hydrogenated silane consisting of monosilane or polysilane, silicide gas consisting of silicon fluoride, or silicide gas diluted with helium, diborane or heptavalent impurity element compound gas Phosphin or arsine, which is a compound gas of an impurity element, is added to a concentration of 10 mol% or less, and the silicide concentration (N (
A high-pressure container filled with a reactive gas, characterized in that the cylinder internal pressure (P (Kg/Crab)) satisfies the relationship of NXP≧300%Kg/ctJ, provided that N5100%.