JPS58145697A - Epitaxial silicon producer - Google Patents

Abstract

PURPOSE:On the vapor-phase deposition of epitaxial silicon, a high-temperature zone and a low-temperature zone are provided along the direction of the feed gas stream in the reaction furnace and high-purity Si is placed in the former, while the base plate is in the latter, to facilitate the formation of high-purity epitaxial silicon. CONSTITUTION:A susceptor 5 of graphite coated with SiC is placed in the quartz reaction furnace 1 so that it makes an angle theta to the stream of the raw material gas in a range from 0 deg. to 10 deg.. The inside of the reaction furnace 1 is divided into the low-temperature zone Z1 and the high-temperature zone Z2 and high- frequency heating coils 6, 6' are adjusted so that the temperature in Z1 is 50- 100 deg.C lower than that in Z2. Further, the base plates 7 for epitaxial silicon are placed in Z1 zone, while high-purity silicon 8 is in Z2 zone. A mixed gas of SiCl4, H2, and HCl is fed from the system 2 through valve 4 and they flow contacting with the high-purity silicon 8 to reach the base plate 7 as high-purity SiCl4 and SiCl2 and deposit on the surface as a thin layer of high-purity epitaxial silicon.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an epitaxial silicon manufacturing apparatus using silicon halide as a raw material gas.

In general, epitaxial silicon is formed on a silicon substrate by chemical vapor deposition to a thickness of several microns to several tens of microns, and is used for semiconductor devices such as XCJ, LSI,
It is mainly used as a substrate material for individual semiconductor devices. In particular, epitaxial silicon is indispensable for SOR elements and electrostatic induction transistor elements with high breakdown voltage and large power capacity, and it is desired that its purity be as high as possible.

Raw material gases commonly used to form epitaxial silicon can be roughly divided into two types: silicon hydride and silicon halide.

The former is mostly monosilane (SiH4), which is often used because it is gaseous at room temperature and is easy to purify. However, it also has the disadvantage that it is difficult to obtain high-quality epitaxial silicon because vapor phase decomposition occurs at low temperatures and the precipitated silicon falls onto the epitaxial growth surface. On the other hand, the latter includes silicon tetrachloride (Si(4)), dichlorosilane (Si CJ4), trichlorosilane (1HOA), silicon tetrabromide (5
Since these raw material gases have high decomposition temperatures, they are less likely to be decomposed in the gas phase like monosilane, and epitaxial silicon of good crystallographic quality can be obtained. However, the purification of the raw material gas has now reached its technical limit, so in terms of purity, it is slightly inferior to epitaxial silicon using monosilane as the raw material gas.

By the way, most of the conventional epitaxial silicon manufacturing equipment using silicon nitride as a raw material gas are designed for the purpose of manufacturing low impurity concentration epitaxial silicon for ICs and individual semiconductor devices with small capacitance. Therefore, it is not suitable for manufacturing high-purity epitaxial silicon. The reason for this is that there is a problem with the manufacturing equipment itself.

That is, for example, when silicon tetrachloride is used, during the growth of epitaxial silicon, silicon tetrachloride reacts with impurities in the forming material (graphite is usually used) of the susceptor that holds the silicon substrate. However, there is a problem in that impurities are ejected into the gas phase, and the impurities are incorporated into the epitaxial silicon, reducing its purity. Another reason is the problem of raw material gas. That is, since silicon chloride contains a strongly corrosive chlorogen element, contamination of containers, piping, equipment, etc. due to corrosion is unavoidable.

Therefore, as long as conventional equipment is used, there is a limit to the purity of epitaxial silicon. If the purity of epitaxial silicon is expressed by its resistivity, the higher the resistivity, the higher the purity, but when using conventional equipment, the purity is 100Ω.
(The limit is m ~ 500 Ω. However, in recent devices and static induction transistors, the resistivity is 1
Since a resistance of 000 Ωrm or more is required, it is difficult for conventional devices to meet this requirement.

The present invention was made to meet such requirements,
In the epitaxial reactor, a high temperature region 50 to 100° C. higher than the low temperature region is formed on the upstream side in the flow direction of the raw material gas, and a low temperature region with an epitaxial growth temperature is formed on the downstream side, and high purity silicon is placed in the high temperature region. An epitaxial silicon substrate is placed in the low-temperature region, and the raw material gas is purified and epitaxially grown in the same reactor, so that high-purity epitaxial silicon can be easily manufactured. The object of the present invention is to provide an epitaxial silicon manufacturing apparatus using as a raw material gas.

Hereinafter, the present invention will be described in detail based on Examples. When epitaxial manufacturing equipment is classified based on its structure, there are three types: a horizontal furnace, a desk-shaped furnace, and a barrel-shaped furnace, and the manufacturing equipment according to the present invention can be structurally applied to any of these types.

FIG. 1 shows an embodiment of a horizontal epitaxial silicon manufacturing apparatus in which the present invention is applied to a horizontal furnace. In FIG. 1, reference numeral 1 denotes a reactor for epitaxial growth, which is made of a material such as quartz.The inlet is connected to a raw material gas supply system 2 via a nozzle 4, and the outlet is connected to an exhaust pump 3. It is connected to the. 'The cross-sectional shape of the reactor 1 may be either circular or rectangular.

Furthermore, by using a double tube, the tube wall can be cooled with water or gas. 5. is a susceptor that holds a silicon substrate, and is made of silicon carbide (SiO) to prevent contamination.
The reactor is made of a rectangular graphite plate coated with a graphite plate, and is installed in the reactor at an angle of inclination θ in the range of 0 to 16° with respect to the gas flow. The susceptor 5 is the reactor 1
Two work coils 6 for high frequency heating arranged around the outer circumference of the
．． 6', it is heated to a predetermined temperature. At this time, the work coil 6.6' is connected to the work coil 6.6' so that the first half region z2 on the windward side of the gas flow on the susceptor 5 is heated at a predetermined temperature 50 to 100° C. higher than the second half region z1 on the leeward side. Adjust the power of each high frequency heating oscillator. If the same oscillator is used for heating, the area 2° and the area 2! In this case, the number of turns of the work coil 6, 6' is adjusted in advance so that the above temperature difference occurs. 7 is an epitaxial silicon substrate, and 8 is high-purity silicon for source gas purification, and as shown in FIG. 1, these are arranged above the low temperature region Z and high temperature region of the susceptor 5, respectively. That is, the high-purity silicon 8 for source gas purification is placed upwind of the silicon substrate 7 with respect to the gas flow, and at a temperature of 50 to 100°C higher than the epitaxial growth temperature (1200°C).
It is placed in the high temperature region z2 on the susceptor 5, which becomes higher.

In this example, the raw material gas is a mixed gas of hydrogen, silicon tetrachloride (5iO- & )% hydrogen chloride (Hal), and is supplied from the raw material gas supply system 2.Silicon tetrachloride For the gas, hydrogen gas is introduced from a hydrogen cylinder 10 through a flow meter 12 into liquid silicon tetrachloride stored in a vaporizer 9 to cause bubbling, and silicon tetrachloride is combined with hydrogen. This vaporization state can be changed by adjusting the flow meter 12. The silicon tetrachloride gas thus obtained is passed from the hydrogen cylinder 10 to the pulp and through the flow meter 12'. The hydrogen chloride is diluted with hydrogen gas supplied by the reactor 1 and supplied to the reactor 1. Hydrogen chloride is also supplied to the reactor 1 from the cylinder 11 via the pulp and the flow meter 12'.

Next, a reaction mechanism for obtaining high-purity epitaxial silicon in the reactor 1 of the epitaxial silicon manufacturing apparatus configured as described above will be explained. Silicon tetrachloride (SiOA) gas diluted with hydrogen gas enters the reactor 1 and a high temperature region 2 where high purity silicon 8 on a susceptor 5 is placed! When reaching , here, SiO
&+H,--→5iOJ! , + 2Hoffl −
−−−−−filSi + 4HOg−−→SiO,
& + Hz −1−−−−−−(21Si +
SiOA-1 → 28104 -------------
An f31 reaction occurs. Here, in reaction (1), a portion of silicon tetrachloride (EIiO,A) decomposes,
Silicon dichloride (810^) and hydrogen chloride (Hcp3)
This is a reaction that occurs, and this reaction does not occur often at high temperatures. On the other hand, the reaction (21, fi+) is a reaction that is less likely to occur at higher temperatures. Therefore, the high purity silicon 8 placed on the susceptor 5 in the high temperature region z2 reacts with silicon tetrachloride and hydrogen chloride, and Therefore, the composition of the raw material gas that passed through the high temperature region z2 is as follows: unreacted silicon tetrachloride (SiOA), silicon dichloride (810), hydrogen (Hz), and chloride. Hydrogen (HOi
).

When these chemical species reach the low temperature region z1, SiO & 1He -111-→Si +2HOJ3-
-----1111(4)2SiC! For Si
＋Sio＆－－－－－－－－(51SiCIA+
2H4Si +4H(j−e−−−−−−−−−(6)
A chemical vapor deposition reaction occurs in the low temperature region 2. It is formed as epitaxial silicon on a substrate silicon 7 placed on a susceptor 5. That is, high temperature region and low temperature region 2. A chemical transport reaction of silicon occurs between silicon dichloride (5iO-&) as a medium. therefore,
High temperature area 2! If a silicon with higher purity than silicon tetrachloride in the raw material gas is used as the high purity silicon above, the epitaxial silicon deposited on the epitaxial silicon substrate placed on the low temperature region 2° susceptor 5 will be as described in (4) above.
Since it also contains the epitaxial silicon obtained by formula (5), the impurity content is lower and the purity is higher than that of epitaxial silicon obtained by directly decomposing silicon tetrachloride only by the reaction of formula (6). It becomes purity. In other words, one side in the reactor 1, ie the high temperature area 2. Then, the raw material gas is purified, and on the other hand, ff1l, low temperature region 2. Now, the manufacturing apparatus of the above embodiment performs both operations of forming epitaxial silicon from purified reta gas.

FIG. 2 shows an embodiment in which the present invention is applied to a desk-shaped furnace. The reactor 13 is made of Versier-shaped quartz or stainless steel, and is configured to be cooled with water or the like. In this embodiment, the susceptor 14 is formed of a graphite disk coated with silicon carbide (EliO), and is configured to be able to rotate by externally driving a shaft provided at its center. There is. Near the bottom surface of the disc susceptor 14 are two high-frequency heating work coils 17 for heating the susceptor 14.
17' are arranged concentrically, and each work coil 1
7. Adjust the high frequency power to 17' and
4, two concentric regions Zs and k are formed on the region 4, and the temperature of the region 4 is the predetermined temperature of the region zz (epitaxial growth temperature 120
The temperature is 50 to 100°C higher than 0°C.

The epitaxial silicon substrate 18 and the high-purity silicon 19 for purifying source gas are placed on the susceptor 14 in the low temperature region zs and the high temperature region 4, respectively, as shown in FIG. Raw material gas is introduced from the gas supply line 16 through a valve into the reactor 13 through a nozzle 20 provided on the central axis of the disk susceptor 14, and the generated gas is exhausted from the gas outlet 15 using an exhaust pump. Ru. The reaction mechanism for obtaining high-purity epitaxial silicon in this example is exactly the same as that in the example shown in FIG.

As described above in detail based on the embodiments, in the present invention, in the reactor, the flow of the raw material gas is
A high-temperature region is formed on the upstream side and a low-temperature region is formed on the downstream side, and high-purity silicon for raw material gas purification is placed in the high-temperature region, and an epitaxial silicon substrate is placed in the low-temperature region to configure an epitaxial silicon manufacturing device. By using this manufacturing apparatus, high purity epitaxial silicon as shown in Table 1 could be obtained.

Note 1. Base gas of raw material gas: Hydrogen 2. Resistivity of silicon for purification: 2000 Ωm As can be seen from the above results, no matter which source gas (silicon halide gas) is used.

Compared to the one in which the raw material gas is directly converted into epitaxial silicon, the one using the apparatus according to the present invention has
It is possible to almost double the resistivity.

[Brief explanation of drawings]

1 and 2 are cross-sectional views of embodiments of an epitaxial silicon manufacturing apparatus according to the present invention, respectively. In the figure, 1 and 13 are reactors, 2 is a raw material gas supply system, 5 and 14 are susceptors, 6.6' and 17.
17' is a work coil for high frequency heating, 7 and 18 are epitaxial silicon substrates, 8 and 19 are high purity silicon, 9 is a silicon tetrachloride vaporizer, 10 is a hydrogen cylinder, 11 is a hydrogen chloride cylinder, z and z8 are low temperature Regions, tae, and 4 indicate high temperature regions.

Claims (1)

[Claims] In the epitaxial reactor, a high temperature region 50 to 100 ° C higher than the low temperature region is formed on the upstream side in the flow direction of the raw material gas, and a low temperature region with an epitaxial growth temperature is formed on the downstream side, and high purity silicon is placed in the high temperature region. An epitaxial silicon manufacturing apparatus characterized in that an epitaxial silicon substrate is disposed in the low temperature region.