JPS6353917A - Crystal growth apparatus - Google Patents

Abstract

PURPOSE:To form hetero-junctions with sharp boundaries by a method wherein the respective crystal growth chambers of a two-chamber type crystal growth apparatus employing a sliding wafer system are heated by individual heaters and are set at the different temperatures. CONSTITUTION:A quartz reaction tube 1 is divided into 1st reaction chamber 2 and 2nd reaction chamber 3 by a partition. A substrate crystal 5 is housed in a quartz slider 4 and can be transferred back and forth between the 1st reaction chamber 2 and the 2nd reaction chamber 3 by moving the slider 4 right and left. Molybdenum heaters 7 and 8 are housed in a substrate holder 6. An N-type GaAs substrate crystal 5 is housed in the slider 4 and currents are applied to the 1st heater 7 and the second heater 8 to make their temperatures 610 deg.C and 710 deg.C respectively. Then N-type GaInP is applied in the 1st reaction chamber and, after the substrate crystal 5 is transferred to the 2nd reaction chamber, an N-type AlGaInP is applied. After that, GaInP, P-type alGaInP and P-type AlGaInP are applied in the same way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a vapor phase epitaxial apparatus for compound semiconductors, and particularly to a crystal growth apparatus suitable for forming a heterojunction.

[Conventional technology]

A conventional two-chamber crystal growth apparatus is described, for example, by Usui et al., Institute Physics Conference, Series No. 63, Chapter 3, pp. 137-142, 1981 (U
Sui et al, Inst, Phys, Co.
nf,.

Set, No. 63, Chapter 3, P137~
142 (1981)), the location where the substrate crystal is placed is constant at, for example, 740°C, and two different types of crystals forming heterogeneous bonds are grown at this temperature. .

In addition, the conventional multi-reaction chamber vapor phase growth apparatus is shown in Fig. 1.
As shown in the figure, the interior of the reaction chamber was divided, reactant gases of desired compositions were flowed into each chamber, and the position of the substrate was moved from one side to the other to form the desired heterojunction. With this structure, it is difficult to completely separate the gas flowing through each reaction chamber, and it is difficult to continuously grow two types of thin film crystals with different optimal growth temperatures because the temperature cannot be changed rapidly. be. Therefore, the formation of heterojunctions with sharp interfaces and good crystallinity is difficult.

[Problem that the invention seeks to solve]

The above-mentioned conventional technology does not take into consideration the fact that the optimal growth temperatures of different crystals are different, so there is a problem that each crystal forming a heterobond is not formed at a truly optimal temperature.

An object of the present invention is to provide an apparatus that can grow crystals forming heterojunctions at optimal temperatures. In other words, in practice, there is no mutual mixing of gases between multiple passage chambers, and only one crystal can be grown in a short time. An object of the present invention is to provide a slide wafer type thin film crystal forming apparatus that can shift from forming a thin film crystal having an optimum growth temperature to forming a different type of thin film crystal having another optimum crystal growth temperature.

Recent advances in semi-quaternary devices using heterojunctions have been remarkable, and new devices such as high electron mobility transistors and multiple quantum well lasers have been proposed and are being put into practical use. In these new devices, heterojunctions, which are obtained by successively growing crystals of different compound semiconductors under lattice matching conditions, play an essentially important role. In this heterojunction, lattice matching must be achieved with high precision on the order of 10-8, and the interfacial transition layer of the heterojunction must be less than one crystal lattice, preferably less than one atomic layer, which is highly sensitive to two-dimensional electrons. It is necessary to realize gas mobility and to realize narrow quantum wells, for example, 50 nm. In addition to molecular beam epitaxial growth, epitaxial growth methods using organic metals are widely used to grow such heterojunction crystals.

However, due to the dead volume that exists in the piping system when switching the reaction gas, adsorption and desorption on the walls of the piping system and reaction tubes.
Phenomena that is not instantaneous due to convection of reaction gas in the reaction tube, and for example, a transition region of crystal composition occurs every 10 to 20 times, or the composition of a certain mixed crystal layer, which should be uniform, is disturbed. can be seen.

Therefore, the performance of the resulting device uses the expected characteristics. In order to overcome these difficulties, it is generally necessary to flow the reactive gas at a high flow rate or to move the substrate crystal at high speed (
For example, the present invention does not use such an extreme crystal growth method,
By moving the substrate crystal between two reaction chambers in which different reactant gases are constantly flowing, it is intended to form a heterojunction with a sharp interface.

[Means for solving problems]

The above object is achieved by heating each chamber with a separate heating device in a two-chamber crystal growth apparatus using the sliding Urchin-hachi method so that different temperatures can be set.

The specific method or method is as follows: ■ A slider carrying a substrate crystal moves between each chamber.

(2) The slider is moved onto the susceptor so that the substrate crystal inside the slider comes into direct contact with the susceptor to obtain a fast thermal response.

■ Set the temperature of the reaction chamber so that the temperature of the substrate crystal is appropriate for each crystal.

■ Using high-frequency heating, temperature differences are created by applying the skin effect of graphite.

■ Install a separate heater for each reaction chamber.

etc., and combinations of these.

A more effective device becomes possible.

[Effect]

By moving the substrate crystal wafer from one chamber to another on a common substrate holder, different types of crystals can be formed one after another depending on the type and concentration of the reaction gas flowing there. The interior is divided into two chambers, each containing a heating device that is driven separately. This allows the temperature of the substrate holder above it to be set separately.

In addition, in a multi-chamber vapor phase growth system that uses high-frequency heating using a slide wafer method, the thickness of the susceptor in each chamber can be made variable, and by using a modular installation method, the degree of freedom in setting the temperature of each chamber can be increased. This makes it possible to set the desired temperature reliably. The basic principle of temperature control is to utilize the skin effect of high-frequency magnetic fields. The electric current induced in a conductor by an alternating magnetic field parallel to the surface of the conductor can generally be expressed as 21 kO·exp-). where ω: angular frequency of alternating magnetic field, to: conductivity, μ
: magnetic permeability, HO: maximum value of magnetic field strength, t: time, X: depth in the material. The electrical conductivity of the pyrolytic graphite used for the susceptor is about 3 mho/m, and the high frequency applied for heating is ~4×10″3 m. Therefore, by changing the thickness of the graphite susceptor around this point, different susceptor temperatures can be obtained for the same high frequency input. Therefore, by changing the thickness of the susceptor depending on the location,
By sliding the substrate crystal to locations with different thicknesses, the substrate crystal wafer is set to different temperatures in a very short time. Since the substrate crystal is not placed on a boat or the like and slides directly on the susceptor, the temperature changes extremely rapidly.

〔Example〕

The present invention will be explained in detail below.

Example 1 This will be explained with reference to FIG. FIG. 1 shows a cross section of a reaction tube, and a quartz reaction tube 1 is divided into a first reaction chamber 2 and a second reaction chamber 3 by a partition wall.

A substrate crystal 5 is housed in a quartz slider 4.

By driving the slider left and right, it is possible to move back and forth between the first reaction chamber and the second reaction chamber. The substrate holder 6 is made of molybdenum or graphite and houses molybdenum heating elements 7 and 8 therein. 5 cm
A 5 an n-type GaAs substrate crystal 5 is attached, and the first heating element 7 and the second heating element 8 are energized to have a temperature of 610", respectively.
First, a gas containing triethyl gallium, trimethyl indium, and phosphine as main reaction gases was flowed into the first reaction chamber to form an n-type G gas for protecting the substrate surface.
Put on aInP.

Next, the substrate crystal is moved to the second reaction chamber and the n-type A n G
Attach aInP. During this time, the amount of current applied to the first heating element is increased to 670°C. The substrate is then returned to the first reaction chamber, where a non-doped GaInP layer is applied, and then returned to the second reaction chamber, where a P-type A Q GaInP layer is applied.

Finally, it is transferred to the first reaction chamber and p-type GaAs is applied.

GaInP/ A Q GaI obtained in this way
When a striped semiconductor laser is made from an nP double heterocrystal, it oscillates continuously at a wavelength of 650° C. at room temperature, and exhibits an extremely low oscillation threshold current density of 1 kA/d. This threshold is 5
The variation within the as X 5 ai wafer surface was within ±15%, indicating that it is possible to improve the performance of a semiconductor laser and uniformly grow a large-area crystal.

Example 2 This will be explained with reference to FIGS. 1 and 2. The quartz reaction tube 11 is separated by a partition wall 12, and gases of different compositions flow into the left and right chambers.
They merge downstream where the bulkhead disappears. A notch is made in the middle of the bulkhead, and a stator 1 made of quartz is placed below it.
7, and a graphite susceptor 15 is fitted into the central recess.

The thickness of this susceptor is different between one reaction chamber and another reaction chamber separated by a partition wall. A quartz spacer 16 is included in the thin susceptor to keep the susceptor horizontal. In this way, by changing the thickness of the left and right susceptors, the high frequency heating effect differs and the temperature can be changed. Flow 3 fl/win of hydrogen gas into each chamber,
A high frequency of 300 kHz is applied using a high frequency heating coil.

If the thicker susceptor has a thickness of 10 mm and the thinner susceptor has a thickness of 3 mm, the respective temperatures can be set to 700°C and 650°C. When the thickness of the thinner side is reduced to 211fi, the temperatures become 700°C and 600°C, respectively. In this way, by preparing susceptors with different thicknesses and preparing corresponding spacers, the temperature of each reaction chamber can be set to different values as desired.

A slider 13 made of quartz is placed on top of the susceptor, and a hole is made in the center of the bottom of the slider 13 to accommodate a substrate 14 for crystal growth. By moving this slider to the right and left, the substrate can be shuttled between reaction chambers where different reaction gases flow and are set at different temperatures. Therefore, different materials can be formed one after another at their optimum forming temperature, and since the transfer time is short and the substrate is in direct contact with the susceptor, the temperature of the substrate can be changed quickly in an extremely short period of time. Normally, when changing the temperature of the susceptor by changing the applied high-frequency power, it takes several minutes for the temperature to settle to a stable value, but with the method described here, the temperature is set in advance to the desired value. Since the substrate crystal simply slides and moves, the temperature change is completed in 2 to 3 seconds.

Example 3 Using the apparatus described in Example 2, the temperature of the susceptor was increased to 72°C.
The temperature is set at 0° C. and 670° C., and trimethylaluminum, trimethylgallium, and arsine are flowed on the high temperature side with hydrogen as a carrier gas, and trimethylgallium, arsine, and hydrogen are flowed on the low temperature side. By repeatedly moving the gallium arsenide substrate crystal between the two chambers, a multilayer structure consisting of aluminum gallium arsenide/gallium arsenide could be formed. As a result of cross-sectional observation using a transmission electron microscope, the transition region of the two types of crystal layers described above was one atomic layer or less.

Example 4 Using the apparatus described in Example 2, the temperatures of the susceptors were set to 710° C. and 660° C., respectively. Triethylaluminum 11. on the high temperature side. triethyl gallium,
Flowing trimethylindium and phosphine,
Triethylgallium, trimethylindium and phosphine are flowed on the low temperature side. (100) A superlattice structure in which aluminum gallium indium phosphide mixed crystal and gallium indium phosphide mixed crystal whose lattice constant matches that of the substrate crystal are stacked by 3 nm each by reciprocating the gallium arsenide substrate crystal between these two reaction chambers. was able to be created.

The optimum growth temperature for these two mixed crystals is approximately 50° as mentioned above.
Since the C crystals are separated from each other, adjusting the growth temperature of one crystal will significantly deteriorate the surface condition of the other crystal. In addition, if the growth temperature is set to the optimum value for each layer, the interface will not be sharp and it will be difficult to create a good superlattice structure. Needless to say, it can be widely used regardless of the type of crystal, such as a compound semiconductor, a ■■ group compound semiconductor, or a IVVI group compound semiconductor.

〔Effect of the invention〕

According to the present invention, the heterojunction interface can be made sharp without forming a transition layer, and each crystal forming the heterojunction can be grown at an optimal temperature, and these temperatures can be freely set. It is.

Further, according to the present invention, a dissimilar joining interface can be formed steeply,
Since each crystal forming a heterojunction can be grown at its optimum formation temperature, it is possible to grow a heterojunction crystal with a larger area and uniform characteristics.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a sliding wafer chamber crystal growth apparatus of the present invention, FIG. 2 is a cross-sectional view of the crystal growth apparatus of the present invention, and FIG. 3 is a side view thereof. DESCRIPTION OF SYMBOLS 1... Quartz reaction tube, 2... First reaction chamber, 3... Second reaction chamber, 4... Quartz slider, 5... Substrate crystal,
6... Substrate holder (graphite), 7... First heating element, 8... Second heating element, 11... Quartz two-chamber reaction tube, 12... Quartz partition wall, 13... Quartz slider, 14
...base@, crystal. 15...Graphite susceptor, 16...Quartz spacer, 17...Quartz stator. 10,000/Tomoeha 2nd Ward

Claims (1)

[Claims] 1. In a sliding wafer multi-chamber crystal growth apparatus that has susceptors in two or more reaction chambers and in which the substrate crystal moves between the susceptors, the temperature of the susceptor in each chamber is heated by a separate heating device, and the following A crystal growth apparatus characterized by setting the temperature of a substrate crystal at a different temperature in each chamber. 2. The crystal growth apparatus according to claim 1, wherein the substrate crystal is moved between two reaction chambers through which different reaction gases flow. 3. The crystal growth apparatus according to claim 1 or 2, wherein the substrate crystal is configured to slide and move on the surface of the susceptor. 4. The crystal growth apparatus according to any one of claims 1 to 3, wherein the substrate crystal is configured to move between the susceptor parts set at different temperatures. 5. The crystal growth apparatus according to any one of claims 1 to 4, wherein the thickness of the susceptor is partially changed to produce the portions having different temperatures. 6. Claim 5, which allows a set of susceptors having different thicknesses to be used interchangeably.
Crystal growth apparatus described in Section 1. 7. The crystal growth apparatus according to any one of claims 1 to 5, wherein the susceptors contained in each of the reaction chambers are heated by separate heating bodies and can be set to different temperatures.