JPS62189727A - Apparatus for thermal decomposition vapor growth of organic metal - Google Patents

Abstract

PURPOSE:To grow a crystal of high quality with good reproducibility by providing a preliminary chamber separated by a gate valve from a reaction tube for reacting to vapor grow a crystal to suppress the influence of oxygen and moisture to the growth. CONSTITUTION:A sufficiently N2-purged preliminary chamber 4 is opened, and a substrate crystal 2 is placed on a substrate base 8 in the chamber 4. Then, the chamber 4 is closed, purified N2 purging and evacuating are repeated sufficiently, and the chamber is evacuating in high vacuum by an evacuating unit 9 while heating the chamber 4 by a preliminary chamber heater 7, and purified N2 purging is executed. Thereafter, a carbon susceptor 3 disposed in a reaction tube 1 is conveyed into the chamber 4, a gate valve 5 is closed to stop conveying, a cover is removed, the crystal 2 is slid on the susceptor 3 and placed. The valve 5 is again opened, and the susceptor 3 for placing the crystal 2 is conveyed by a substrate heating base conveying arm 6 into the tube 1. After the above steps are finished, a growth is started.

Description

Detailed Description of the Invention: Industrial Application Field The present invention is an organometallic pyrolysis method in which a substrate crystal sample is placed on a heating device without exposing a carbon susceptor to outside air to form a high-quality semiconductor crystal growth film. The present invention relates to a vapor phase growth apparatus.

BACKGROUND OF THE INVENTION In recent years, research and development of visible light semiconductor lasers and ultrahigh-speed devices using compound semiconductors has been actively conducted. As an epitaxial growth method for thin films, molecular beam epitaxy (MBE) and vapor phase epitaxy are used instead of the conventional liquid phase growth method because they are easy to form an ultra-thin multilayer structure and have excellent steepness of the Peter interface. (Hydride VPE and MOC)
(VD) is the mainstream. Among these, the MOCVD method is attracting particular attention as an organometallic thermal decomposition method.

Currently, many of the compound semiconductors that are attracting attention for the purpose of application to the above-mentioned devices are mixed crystal systems containing aluminum. However, in organometallic pyrolysis, aluminum has very strong chemical reactivity, which is one of the major problems with this growth method.

For example, if the inside of the reactor is brought into contact with the atmosphere in order to place the substrate crystal in the reactor, the crystallinity such as the surface morphology of the resulting epitaxial crystal will be extremely poor, and reproducibility will be lost. It is thought that the moisture or oxygen adsorbed in the reactor and susceptor during introduction greatly affects the quality of the epitaxially grown film obtained.

In order to solve this problem, a load lock mechanism is used that allows a susceptor on which a substrate crystal is mounted to be placed inside the reactor without exposing the inside of the reactor to the atmosphere.

FIG. 3 shows a schematic diagram of the vicinity of the glue actor in a conventional MOCVD apparatus. 1 is a quartz reaction tube, 2 is a semiconductor substrate crystal, 3 is a substrate heating table, 4 is a preliminary chamber for mounting the semiconductor substrate crystal 2 on the substrate heating table 3, and 5 is a separating chamber between the quartz reaction tube 1 and the preliminary chamber 4. Gate pulp, 6, substrate heating table 3, quartz reaction tube 1
This is a transport arm for placing the device inside.

First, the substrate heating table 3 is pulled out from the preliminary chamber 4i by the transfer arm 6, and the gate pulp 6 is closed to shut off the quartz reaction tube 1 and the preliminary chamber 4. Thereafter, the preliminary chamber 4 is broken and the substrate crystal 2 is placed on the substrate heating table 3. After evacuation of the preliminary chamber 4 and purging of purified N2 are repeated sufficiently, the gate pulp 5 is opened again, and the substrate heating table 3 is placed in the quartz reaction tube 1 by the transfer arm 6. Once the above steps are completed, growth begins.

Problems to be Solved by the Invention However, in this conventional method, the carbon susceptor, which has an extremely strong adsorption capacity for moisture and oxygen, comes into contact with the outside air, so the influence of moisture and oxygen on growth could not be completely eliminated. . A load lock mechanism having a plurality of preliminary chambers has also been used, but it has the disadvantage that the device becomes bulky. Therefore, it has been extremely difficult to obtain a high-quality epitaxially grown film containing aluminum with good reproducibility.

Means for Solving the Problems The technical means of the present invention for solving the above problems is an organometallic pyrolysis vapor phase growth apparatus for vapor phase growth on a semiconductor substrate, in which the above vapor growth reaction is performed. The reaction tube is equipped with a preliminary chamber separated by a gate pulp, and the transfer mechanism allows the substrate heating table to be moved between the reaction tube and the preliminary chamber. It is equipped with a movable transport mechanism, a heating mechanism that can heat the preparatory chamber, and a vacuum mechanism that can make the preparatory chamber or reaction tube a high vacuum.

For production The effect of this technical means is as follows.

Before moving the susceptor to the preliminary chamber, the preliminary chamber is heated and brought to a high vacuum, so that moisture and oxygen in the preliminary chamber are sufficiently removed. After that, place the susceptor in the spare room,
Since the substrate crystal is mounted on the susceptor, adsorption of moisture and oxygen to the susceptor is extremely suppressed.

EXAMPLE Hereinafter, an example of the present invention will be described based on FIGS. 1 and 2. In FIGS. 1 and 2, the same components as those in FIG. 3 are given the same numbers and detailed explanations are omitted. Substrate heating methods include high-frequency heating, infrared heating, and resistance heating, but in this actual gun example, high-frequency heating, which has a fast temperature rise rate, is used.
゛In a reactor having a preliminary chamber 4 separated by a gate pulp 6 shown in Figs. 1 and 2, setting of the substrate crystal 2 is carried out as follows. 4 is opened and the substrate crystal 2 is placed on the substrate stand 8 in the preliminary chamber 4.

Thereafter, the preparatory chamber 4 is closed, and vacuuming with purified N2/'-di is repeated sufficiently. Furthermore, while the preliminary chamber 4 is heated to about 100° C. by the preliminary chamber heating heater 7, it is brought into a high vacuum state using a vacuum device 9 such as a turbo molecular pump. At this time, a cover is placed over the substrate to prevent deposits from forming on the substrate surface.Although this cover may be a mechanical type such as a shutter, in this example, the substrate crystal 2 same as G
It was decided to place the aA s wafers on top of the substrate crystal 2.0 After this, the interior of the preliminary chamber 4 was sufficiently exposed.
After heating and evacuation of the inside, purification with N2/'-di is carried out.

Thereafter, as shown in FIG. 2, the carbon susceptor 3 placed in the reaction tube 1 is transported into the preliminary chamber 4 and the gate pulp 6 is closed. The conveyance is stopped when the carbon susceptor 3 is lined up with the substrate stand 8, and the arm 1 for sliding the substrate crystal is moved.
After removing the cut (-) with o, slide the substrate crystal 2 onto the carbon susceptor 3 and place it. Then, open the gate valve 6 again and move the carbon susceptor 3 on which the substrate crystal 2 is mounted onto the substrate heating table transfer arm 6. is transported into the reaction tube 1. After the above steps are completed, growth is started.

In this embodiment, the heater 7 is embedded in the wall of the preliminary chamber 4, but other methods may also be used to heat the substrate table 8, such as heating the preliminary chamber 4 itself and heating the substrate crystal 2. If you also aim to pre-bake the board, use the board stand 8.
A method may also be used in which a heater is embedded inside the substrate so that the substrate crystal 2 can be heated to a high temperature.

Growth depends on the flow rate of source gas and substrate temperature, but for example, when growing AIo, 3Ga0.7As, TM
G()limethylgallium) = 1occ/i, TMA(
trimethylaluminum) = 10 CC:/mJA
, AsHs=16CC/rruR, H2 gas=21/
An AI GaAs epitaxial thin film was grown on a GaAs substrate at a substrate temperature of 7800C.

I performed 27 runs using this method, and the variation in the composition was extremely small.The variation in the 0 composition is x=o,
7±0.01, crystals with good surface morphology were obtained with good reproducibility.

Effects of the Invention As described above, according to the present invention, the sample can be placed in an airtight condition, which eliminates the influence of oxygen and moisture on growth, which was one of the problems with metal-organic pyrolysis vapor phase apparatuses. This makes it possible to grow high-quality crystals with good reproducibility. Therefore, it is extremely important for the development of compound semiconductors.

[Brief explanation of drawings]

1 and 2 are a side view and a top view of the vicinity of a reaction tube of a vapor phase growth apparatus according to an embodiment of the present invention, and FIG. 3 is a side view of the vicinity of a reaction tube of a conventional vapor phase growth apparatus. 4...Preliminary room, 5...Gate pulp,
6...Arm for transporting substrate heating table, 7...
・Heating heater, 8... Board stand, 9...
・Vacuum equipment.

Claims (1)

[Claims] In an organometallic pyrolysis vapor phase growth apparatus for vapor phase growth of a thin film on a semiconductor substrate, a reaction tube in which the growth reaction is performed is separated from a preliminary chamber by a gate valve, and a substrate is heated between the reaction tube and the preliminary chamber. a transport mechanism for moving a table; a transport mechanism for transporting the substrate mounted on a substrate stand in the preliminary chamber to the substrate heating table; a heating mechanism for heating the preliminary chamber; An organometallic pyrolysis vapor phase growth apparatus comprising a vacuum mechanism for making the reaction tube a high vacuum.