JPH0244800B2 - TANKETSUSHOSEICHOSOCHI - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a single crystal growth apparatus with improved temperature measurement and film thickness control in vapor phase epitaxial growth.

(b) Background of the Technology Semiconductor devices using compound semiconductor crystals such as gallium arsenide (GaAs) and aluminum gallium arsenide (AlxGa ₁ -xAs) are well known.

Semiconductor devices such as microwave diodes and transistors are produced by epitaxially growing crystals of the same type containing donor impurities or acceptor impurities on a single crystal wafer made of the above-mentioned compound semiconductor, or by growing these impurities. A variety of semiconductor devices are made by directly diffusing semiconductors to create semiconductor regions with different conductivity types (electron conduction type or hole conductivity type) and conductivity. In addition, GaAs is grown on AlxGa ₁ −xAs as a buffer layer (hetero buffer),
It has also been used to form transistors.

Now, devices such as diodes and transistors that utilize junctions of semiconductor layers with different types of conductive carriers need to have high rectification ratios and uniform characteristics, and to achieve this, the thickness of the epitaxial layer must be precisely controlled. It is necessary for the impurity concentration gradient to be steep. Furthermore, in order to form a good hetero buffer structure, it is necessary to realize a steep composition gradient.

The present invention relates to the configuration of an apparatus for vapor phase epitaxial growth of a semiconductor layer that satisfies these conditions.

(c) Prior art and problems In order to grow an epitaxial layer with a steep impurity concentration gradient and composition gradient on a semiconductor single crystal wafer (hereinafter referred to as wafer), the reaction gas in the reaction vessel must be exchanged quickly. is necessary, and until now one of the following methods has been used.

(1) Increase the flow rate of the reaction gas.

(2) Introduce the reaction gas close to the wafer using a thin tube.

(3) Use a liner tube.

Among these methods, method (1) allows for rapid gas exchange within the reaction vessel, but as a result of changes in the decomposition temperature of the wafer and source gas, the gas flow, etc., the uniformity of epitaxial growth may be affected. There is a drawback that it can be damaged.

In addition, method (2) cannot be used when the temperature during the growth process is controlled using an infrared thermometer instead of a thermocouple, or when the thickness of the growth layer is measured using interference light because the field of view is obstructed. There are drawbacks.

However, method (3) using a liner tube is extremely effective in narrowing the effective volume inside the reaction vessel and preventing contamination of the side wall of the reaction vessel.

Next, to measure the film thickness during epitaxial growth, a jig with a transparent quartz viewing window is installed at the top of the vertical reaction tube, and monochromatic light from a tungsten lamp, xenon lamp, or laser is projected from this jig. This interference was used to measure film thickness.

However, the upper part of the vertical reaction tube is also an introduction path for the reaction gas, and in order to obtain a steep composition gradient and impurity concentration gradient when performing epitaxial growth of different types, it is not allowed to increase the volume of the upper part of the reaction tube.

Therefore, it is difficult to separate the incident light and reflected light for film thickness measurement from the top of the reaction tube because the gas introduction path is made narrow, and the observation device must be placed on top of the growth device or a reflecting mirror must be used. It was necessary to form a light guide, which required complicated operations.

Note that since the reaction vessel is made of transparent quartz, it is possible to measure the film thickness from the side of the vessel, but observation is impossible because the reactants are separated and deposited on the inner wall of the vessel during epitaxial growth.

(d) Purpose of the Invention The purpose of the present invention is to provide a method that enables external measurement of film thickness, temperature, etc. during vapor phase epitaxial growth of compound semiconductors, and also enables the growth of semiconductor layers with steep compositional and concentration gradients. The purpose is to provide the configuration of the device.

(e) Structure of the Invention The object of the present invention is to provide a liner tube in the center of a reaction tube made of transparent quartz, and to provide a quartz block supported by the liner tube in the upper part of the liner tube, so that a reaction introduced from the upper part of the reaction tube can be carried into the block. A semiconductor crystal in which multiple flow holes are provided so that the gas once hits the reaction tube wall and then reflects and flows into the wafer, and these flow holes are used as reaction gas flow holes and observation holes for measuring film thickness and temperature. This can be achieved using a growth device.

(f) Embodiments of the Invention The present invention takes advantage of the fact that thermal decomposition products do not precipitate in the gas blow-off hole and that the reaction tube of the semiconductor crystal growth apparatus is made of transparent quartz, and the reaction gas inflow hole is connected to the reaction tube. It is bent to the wall and used as an observation window to measure film thickness, temperature, etc.

The present invention will be explained below with reference to the drawings, using GaAs as a compound semiconductor.

FIG. 1 is a front view of a semiconductor crystal growth apparatus embodying the present invention, and FIGS. 2 and 3 are a cross-sectional view A and a plan view B of a quartz block according to the present invention.

In Fig. 1, this device consists of a reaction tube 1 made of transparent quartz and a high-frequency induction coil 2 for performing thermal decomposition.
Raw material gases such as arsine (AsH ₃ ), trimethylgallium [Ga(CH ₃ ) ₃ ], trimethylaluminum [Al(CH ₃ ) ₃ ], and hydrogen sulfide (H ₂ S) are supplied to the upper part of the reaction tube 1. There are an inlet 3 and an inlet 4 for supplying a carrier gas such as hydrogen (H ₂ ).

Further, in the center of the reaction tube 1, surrounded by a liner tube 5, a GaAs wafer 6 is placed on a carbon susceptor 7, and the lower part of the carbon susceptor 7 is connected to a holding rod 8, which is connected to a motor during crystal growth. It is configured to rotate at a low speed.

Here, in vapor phase epitaxial growth, the reactant gas and carrier gas, which are adjusted to a specified flow rate, flow from above through the upper inlets 3 and 4 and are discharged from the outlet 9, while the high frequency induction coil 2 is energized to grow carbon. By heating the susceptor 7, a chemical reaction is caused on the wafer to perform epitaxial growth.

Here, the liner tube 5 is provided to reduce the effective volume inside the reaction tube 1 to facilitate the replacement of the reaction gas, and to prevent contamination of the reaction tube 1 by decomposition products by precipitation. It is also used in crystal growth equipment.

The present invention is characterized in that the liner tube 5 is used as a support and a quartz block 10 having a gas inflow hole and an observation hole is provided thereon. That is, the quartz block 10 has a cylindrical shape, and a gas inlet hole 11 provided at the center branches into a plurality of holes toward the reaction tube, and after reaching the outer circumference of the quartz block 10, it is placed on the susceptor again. The wafer 6 is provided with an inflow hole that is bent toward the wafer 6 that is bent.

The inlet hole 12 provided below the quartz block 10 is used to measure the film thickness and temperature of the wafer 6 through the reaction tube wall 1. The diameter of the inlet hole 12 is 20 mm compared to the diameter of the quartz block 10 of 60 mm in this example. .

Note that FIG. 2 shows a case where two communication holes 12 are provided at symmetrical positions, and FIG. 3 shows a case where four communication holes 12 are provided orthogonally.

Conventionally, when the flow hole 12 was used also as an observation hole, decomposition products would precipitate on the wall of the reaction tube and become unobservable, but since the reaction gas is flowing, no precipitation occurs in this area. You don't have to worry about it blocking your view.

Next, the advantage of this quartz block 10 is that when measuring the thickness of an epitaxial layer, the incident light 13 and the reflected light 14 are completely separated, making it easy to observe. be. Further, when four communication holes 12 are provided as shown in FIG. 3, the thickness of the grown film can be measured using two laser light sources with different wavelengths. Furthermore, it is naturally possible to measure the temperature of the wafer 6 using this communication hole 12.

In this way, the present invention prevents the reaction tube wall from being contaminated with decomposition products by providing the reaction gas inflow hole obliquely toward the wafer from the reaction tube wall, thereby allowing the reaction tube wall to be located at a position that could not be visually observed in the past. Film thickness can be measured by separating incident light and reflected light.

(g) Effects of the Invention By carrying out the present invention, the film thickness can be easily controlled during epitaxial growth, and the characteristics and yield of semiconductor devices can be improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a semiconductor crystal growth apparatus to which the present invention is applied, and FIGS. 2 and 3 show the shape of a quartz block according to the present invention, with A being a cross-sectional view and B being a plan view. In the figure, 1 is a reaction tube, 5 is a liner tube, 6 is a semiconductor single crystal wafer, 7 is a carbon susceptor, 1
0 is a quartz block, 11 is a gas inflow hole, and 12 is a reaction gas distribution hole.

Claims (1)

[Claims] 1. In the center of the reaction tube, there is a substrate to be processed surrounded by a liner tube and placed on a susceptor, and above the substrate to be processed is a block body supported by the liner tube. It is equipped with a plurality of bent reaction gas flow holes that guide the reaction gas supplied from the upper part of the tube toward the reaction tube wall, and then reflect it on the tube wall and guide it to the substrate to be processed. A single crystal growth apparatus characterized by performing vapor phase epitaxial growth by heating a substrate to be processed from the outside while supplying a reactive gas through a hole, and also performing temperature measurement and film thickness control using the communication hole. .