JPH0450193A - Apparatus for vapor growth - Google Patents

Abstract

PURPOSE:To prevent the surface of a substrate from being damaged even if the substrate is held upside down and enable growth of a crystal film having high homogeneity by providing a substrate holder with holding members, composed of nonheating elements, contacting a crystal growth surface of the substrate for growth and holding the substrate in a heating element susceptor. CONSTITUTION:A substrate holder is constructed from a heating element susceptor 11 for carrying a wafer which is a substrate for growth, a wafer presser 12 and pins 13, composed of nonheating elements, contacting a crystal growth surface of the wafer and holding the wafer in a heating element susceptor 11. The wafer is then placed in the center of the wafer presser 12 and supported with the pins 13. In this state, the wafer presser 12 is placed in a susceptor pedestal 11 and fixed with bolts. Thereby, the wafer can be held even downward. A reaction gas is then made to flow and a crystal is grown on the wafer by a vapor growth method.

Description

[Detailed Description of the Invention] [Summary] To prevent the growth surface from becoming thermally non-uniform and being damaged due to heat generated by the nails of a susceptor when a substrate is held upside down in a vapor phase growth apparatus. For this purpose, the claws that come into contact with and hold the growth surface of the substrate are made of a non-heat generating element.

[Industrial application field]

The present invention relates to a vapor phase growth apparatus.

[Conventional technology]

In the conventional vapor phase growth apparatus, it was sufficient to place the substrate 22 on the carbon susceptor 23. Carbon susceptor 23
A substrate 22 was placed thereon, and a reaction gas 24 was flowed into the reaction chamber 21 to grow semiconductor crystals on the substrate 22. However, due to the natural convection of the source gas, it is difficult to obtain a uniformly grown film, and when a source gas that actively reacts in the gas phase is used, a large amount of deposits 26 on the ceiling surface of the reaction tube increases. This also has the problem of disturbing the flow of the source gas and making it difficult to obtain a uniform film, especially in the case of compound semiconductor growth (FIG. 7). On the other hand, a growth method is known in which the substrate faces downward to reduce convection effects and adhesion to the ceiling surface.

[Problem to be solved by the invention]

However, in the above method, how to hold the substrate is an issue. In other words, the carbon claws support the substrate against the carbon susceptor, but as the area around the carbon mold on the surface of the substrate is heated and the temperature rises, the quality of the film deteriorates at the edges of the substrate, resulting in It has been discovered that this extends to near the center of the board.

Therefore, an object of the present invention is to provide a vapor phase growth apparatus that can hold a substrate without damaging the substrate surface and grow a highly uniform crystal film even when the substrate is held upside down. With the goal.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a heating element susceptor on which a growth substrate is placed, and a non-heating element that contacts the crystal growth surface of the growth substrate and holds the growth substrate on the heating element susceptor. Provided is a vapor phase growth apparatus characterized in that it has a substrate holder consisting of a holding member, holds a substrate to be grown on the substrate holder, and causes crystal growth on the substrate to be grown by flowing a reaction gas.

Heating elements and non-heating elements refer to those that generate heat during vapor phase growth and those that do not. In the case of high-frequency heating, carbon is a typical heating element, and non-heating elements include boron nitride, alumina, etc. be.

[For production]

In the device of the present invention, the claw portion (holding member) of the substrate holder that supports the substrate is made of a non-heat generating element, so the substrate surface is free from thermal non-uniformity due to the claw portion (holding member). , so the growing crystal is not damaged. By holding the board facing down using this board holder,
Vapor phase growth is performed without disturbance of the source gas flow due to the effect of thermal convection or the effect of deposits on the ceiling surface of the reaction tube, making it possible to achieve more uniform crystal growth.

〔Example〕

Figure 1 shows an example vapor phase growth apparatus (atmospheric pressure horizontal MOMCVD).
equipment). In the figure, 1 is a reaction tube, 2 is a high frequency Koinobe 3 is a substrate holder, and 4 is a substrate. The substrate 4 is held by the substrate holder 3 and placed in the reaction tube 1 facing downward. 5 is an inlet for pure hydrogen gas, 6.7 and 8 are source gas bubblers, 9.10 is a dopant gas cylinder, 11 is a pressure reducing valve, and 12 is a block valve from which the mixed source gas is sent into the reaction tube 1. It will be done. 13 is a filter, 14 is an adsorbent, 15 is a detector, and 16 is connected to an exhaust system.

Figure 2 shows details of the substrate holder. Susceptor pedestal 11
is made of carbon and has a pedestal into which the wafer holder 12 just fits. The wafer holder 12 is made of PBN (Pyrolyt).
A wafer is placed in the center, supported by a bin 13, and when the wafer holder 12 is placed in the susceptor pedestal 11 with the wafer placed in it, it can hold the wafer even downward. can. The wafer holder 12 can be inserted into the susceptor pedestal 11 by inserting the wafer holder and then fixed with bolts. In this example, the hole is 3 inches.

The pin 13 is connected to the wafer holder 12 to hold the wafer.
The protruding part 1 protrudes slightly inward from the main body by 1 mm.
4 has a thickness of 1.5 mm, but the front and rear ends are finished with smooth curves to avoid disturbing the gas flow as much as possible.

In this device, a 3-inch diameter GaAs substrate was used,
A1. A ■-■ group semiconductor of Ga+-xAs (x=0.28) was grown. As a source gas, trimethylaluminum (TMAI), )limethylgallium (TMG)
a) Tertiary butylarsine (tBAs) was used.

Tertiary butylarsine (tBAs) is used as an arsenic raw material.
) was used with the aim of selecting a material from which it is difficult to obtain uniform crystals, in order to clarify the effects of the present invention. In addition, this tertiary butylarsine (tBA
s) is a gas that is superior in terms of safety compared to arsine, which is commonly used as an arsenic raw material.

The growth conditions were as follows.

Gas flow rate: TMAI 1.26xlO-5mol/minT
MGa 4.04 xlo-5mol 7m1n
tBAs 3.17X10-3mol/m1n(
V/III ratio = 60) Si2H68,18XIQ-8 mol/min Substrate temperature: 650°C Growth film thickness: 9 Qnm The film thickness and dopant concentration distribution of the thus grown A1°, 28Ga0.72AS were measured. The results are shown in FIGS. 3 and 4. Very good results were obtained, with the film thickness distribution being within 0.9% and the Si doping concentration distribution being within 1.2%.

Next, an example will be given showing the effect of holding the substrate upside down. The same apparatus as in Figure 1 is used, but the wafer holding pins are made of carbon and the arsenic raw materials are of two types: tert-butylarsine and arsine. FIG. 5 shows the results of an example in which two types of tertiary butylarsine and arsine were used. In the conventional method, the growth rate has a large distribution (10%, 40%) along the flow of the source gas for both arsine and tert-butylarsine.
On the other hand, in the upside-down holding method, the growth rate had a small distribution (within 5 to 6%) along the flow of the source gas for both arsine and tert-butylarsine.

In the case of a carbon holder using the upside-down holding method, when the substrate holder was rotated, the film thickness distribution decreased to 3 to 4%.

Furthermore, the film thickness distribution was compared between the case where the pins of the substrate holder and wafer press were made of carbon and the case where the pins were made of carbon. The film thickness distribution at this time is shown in FIG. As seen in the figure, in the case of carbon, the film thickness changes greatly at the edge of the wafer, and it is recognized that the yield is reduced. On the other hand, in the example, the film thickness is uniform even at the edges of the wafer.

Note that if the surface shape of the wafer holding pin of the substrate holder is not a smooth curved surface, the flow of the source gas may be disturbed by the pin, resulting in some unevenness and deterioration of the film quality. was recognized.

In the above example, the growth of a group Ⅰ mixed crystal ternary semiconductor was described, but the growth of a group Ⅰ mixed crystal semiconductor is similar to that of a quaternary semiconductor or higher, and the type of reactor is horizontal. In addition to normal pressure MOCVD furnaces, vertical furnaces, reduced pressure furnaces,
It is obvious that this method can also be applied to chloride CVD furnaces.

〔Effect of the invention〕

According to the present invention, even if the growth substrate is held upside down, damage to the substrate surface by the member holding the substrate is prevented. Therefore, when using a material that cannot be formed into a uniform film in a normal MOCVD furnace due to natural convection or adhesion to the reaction tube, the substrate is held upside down to ensure uniform film quality. Since the uniformity of the film does not deteriorate due to the holding portion, the desired effect can be obtained. Therefore, a crystal film of high quality and high uniformity can be grown, which has the effect of improving the performance of a semiconductor device using this semiconductor crystal and simplifying the manufacturing process.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of the vapor phase growth apparatus of the example, Fig. 2 is a cross-sectional view of the substrate holder, and Fig. 3 is the Alo grown in the example.
Figure 4 shows the distribution of membrane pressure of 28ca0.72AS, Alo, 2sGao, ? 2AS
FIG. 5 is a diagram showing the film forming rate during crystal growth by holding the substrate upside down and in the conventional method. FIG. 6 is a diagram showing the dopant concentration distribution diagram for Alo, 2eGao, and
Figures 7a and 7b, which show the distribution of the film thickness of t2As, are schematic diagrams showing the state of gas flow in the conventional method and the vapor phase growth method of the present invention. 1... Reaction tube, 3... Substrate holder 11... Susceptor pedestal, 13... Pin. 2...High frequency coil, 4...Substrate, 12...Wafer holder, substrate holder Diagram Distance (mm) Diagram Position in gas flow Diagram Position within substrate plane Diagram

Claims (1)

[Claims] 1. It has a substrate holder consisting of a heating element susceptor on which the growth substrate is placed and a non-heating element holding member that comes into contact with the crystal growth surface of the growth substrate and holds the growth substrate on the heating element susceptor. A vapor phase growth apparatus characterized in that a substrate to be grown is held by the substrate holder, and a crystal is grown on the substrate by flowing a reaction gas.