JPH04187587A - Device of growing crystal of compound semiconductor - Google Patents

Abstract

PURPOSE:To obtain high-purity compound semiconductor crystal in growth of compound semiconductor crystal by a pulling method by providing an airtight container to store a crucible with a pressure buffer path to communicates the inside and outside of the container and laying a pressure buffer container at n inlet and an outlet of the pressure buffer path. CONSTITUTION:In a device of growing compound semiconductor crystal wherein a crucible 1 charged with a compound semiconductor melt 5 of CaAs is wholly covered with a container 2 having high air tightness, the interior of the airtight container 2 is in an atmosphere containing a gas of an element having higher vapor pressure among elements constituting the melt 5 and the airtight container 2 is provided with a pressure buffer path 10 having throttled channel communicated with outside of the container 2, the following constitution is added. Namely, at least one of an inlet and an outlet of the pressure buffer path 10 is provided with a pressure buffer container 12 having the same or larger volume than space charged with the gas in the airtight container 2.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a compound semiconductor crystal growth apparatus for growing compound semiconductor crystals such as GaAs crystals using an airtight container, and particularly relates to a compound semiconductor crystal growth apparatus for growing compound semiconductor crystals such as GaAs crystals using an airtight container. Use an airtight container that prevents impurities from entering.

[Prior Art] Compound semiconductor crystals, such as GaAs crystals, have light emitting properties,
It has excellent features not found in other materials, such as magnetoelectric conversion properties and high-speed electrons, making it a material with extremely high industrial value. Many methods have been proposed for crystal growth, and some are used in industrial production. Among these, a widely used method is to float an inert liquid such as B2O3 on a GaAs melt, and while preventing the dissociation of AS from the melt, it rotates around a seed crystal brought into contact with the melt as a nucleus. This is a liquid-contained lifting method (LEC method) in which the material is pulled up while lifting. This method has the feature that single crystals can be obtained relatively easily, and is a method with high industrial productivity.
It has been put to practical use in applications such as s-crystals.

By the way, the inactive iα form of B2O3 is G a A S
When floating in the R liquid, the temperature gradient in this area becomes large and the crystal undergoes thermal distortion. G a A S crystals are inherently brittle and susceptible to thermal strain, so thermal strain that the crystal undergoes during manufacturing can cause crystal defects called dislocations, or in extreme cases, cracks can form in the crystal. There is. In order to improve these problems, it is effective to make the temperature distribution uniform throughout the crystal and to reduce thermal distortion. However, in this case, since the temperature of the entire crystal increases, As is dissociated from the crystal surface during pulling, causing precipitation of Ga on the crystal surface and becoming a source of new dislocations.

Therefore, in order to solve these problems, we improved the LEC method, covered the crucible with an airtight container made of quartz container, etc., and filled the gap between the drawing shaft and the airtight container with a B2O3 liquid sealant. (Japanese Patent Publication No. 1397/1982) has been proposed in which dissociation of As from the surface of the GaAs melt is prevented by closing the container and creating an AS atmosphere inside the airtight container.

This method is called the double melt seal pulling method, and is an optimal method for growing GaAs crystals in an environment with small thermal distortion.

Another method for reducing thermal distortion is called the vertical Bridgman method. G a in a vertically long crucible
Add A s ingredients and G a A s ii! l! A liquid is made, a seed crystal is placed in the crucible, and the melt is solidified from the bottom to form GaA.
This is to produce s crystal. In this method, since it is necessary to prevent the dissociation of As from the melt, the entire crucible is covered with an airtight container, and the As placed inside is heated to gasify to create an AS atmosphere (W, A, Gault et al.
J, Crystal Gro abbreviation h 74. P491 (1
986)). Compared to the LEC method, it is easier to soak the entire crucible, and crystals with fewer dislocations can be obtained.

All of the methods described above can produce crystals with small thermal strain. However, since the growth is basically in an airtight container, it is necessary to balance the pressure inside and outside the container, and if the pressure cannot be balanced properly, there is a risk that the container will explode. Therefore, we created pores for pressure balance (Unexamined Japanese Patent Publication No. 1999-1-
37497), and this was further developed by providing a buffer passage to prevent the volatile component AS from diffusing outside the container (Japanese Patent Application No. 01-272542), which serves as a diffusion barrier for AS. A number of innovations have been made.

This makes it possible to prevent the dissociation of As from the GaAS melt even if the container is not completely airtight, making it possible to grow high-quality crystals with low thermal strain using a simple and highly operable device.

[Problems to be Solved by the Invention] However, even with these methods that have small thermal strain and can prevent dissociation of As, gas from outside the container flows in due to pressure fluctuations inside and outside the container. Therefore, even if impurity contamination is prevented at the stage of accommodating the melt raw material, gas containing impurities (for example, Si, etc.) from outside the container may flow in during growth, and the grown crystal may be contaminated. Compound semiconductors such as GaAs require high purity, and even when impurities are added, limited elements are added at limited concentrations, so impurity contamination caused by chance as mentioned above is the least likely. This is an undesirable phenomenon and a big problem.

An object of the present invention is to provide the above-mentioned method by interposing a buffer space to prevent the inflow of impurity gas from the outside when growing a compound semiconductor crystal in a growth apparatus having pores and pressure buffer passages in an airtight container. An object of the present invention is to provide a compound semiconductor crystal growth apparatus that can grow highly pure compound semiconductor crystals by eliminating the drawbacks of the prior art.

[Means for Solving the Problems] The present invention provides that the crucible containing the compound semiconductor aa is entirely covered with a highly airtight container, and that the vapor pressure of the compound elements constituting the melt is controlled inside the airtight container. It is used for compound semiconductor crystal growth equipment, which has an atmosphere containing a higher elemental gas and has a pressure buffer path in an airtight container with a flow path communicating between the inside and outside of the container.

In addition to the spatially narrowed pressure buffer path, a spatially widened pressure buffer space is provided.

This pressure buffer space can be any of the 8 inlets of the pressure buffer path,
Alternatively, both may be configured with a pressure buffer container having a volume that is approximately equal to or larger than the volume of the space filled with gas within the airtight container.

The pressure M street includes pores and pressure buffer passages, and the pressure buffer passages further include capillaries and labyrinth structures.

A pressure buffer container consists of a container with suitable gas inlet/output holes to release gas from the pressure buffer path or to introduce gas into the container, and this is attached to the pressure buffer path provided in the airtight container. . The mounting position may be inside the airtight container or outside the airtight container, and it may be installed at the gas inlet/outlet portion of the pore or buffer passage. It is preferable that the volume of the pressure buffer container is as large as possible. If the volume is roughly equivalent to the volume of the space filled with gas in an airtight container, it will be possible to effectively alleviate the contamination phenomenon caused by the inflow and outflow of gas.

The material for the container constituting the buffer space is preferably a high-purity material that is stable at high temperatures and does not become a new source of impurity contamination to the desired semiconductor crystal. BN (pBN
), quartz, alumina, boron nitride, silicon nitride, silicon carbide, etc. are preferable.

[Effects] If a pressure buffer vessel with a volume that is approximately equal to or larger than the volume of the space filled with gas inside the airtight container is provided in the pressure buffer path, pressure fluctuations inside and outside the airtight container will occur, causing damage to the outside of the airtight container. Even if some gas tries to flow in, the pressure relaxation force of the gas is high due to the spatial expansion, and the fluidity of the gas is kept low, so the flow of the external gas stops inside the pressure buffer vessel and does not flow into the melt. You can avoid touching it.

Therefore, if impurity contamination is prevented at the stage of storing the melt raw material, gas containing impurities from outside the container will not flow into the container during growth, and the grown crystal will not be contaminated.

[Example] Hereinafter, an example of the present invention applied to the growth of a Ga AS single crystal will be described with reference to the drawings.

Example 1 A melt seal pulling device as shown in FIG. 1 was used. A
In order to create a gas atmosphere, the crucible 1 is surrounded by an airtight container 2, and this airtight container 2 is covered by a high pressure container 7 roughly filled with inert dregs.

The airtight container 2 is made of pBN, and a crucible 1 also made of pBN is placed at the bottom thereof, and a rotating shaft 9 for rotating the airtight container 2 is attached to the bottom of the crucible 1 . The upper part of the airtight container 2 is open for inserting the pulling shaft 3 and the like into the airtight container 2. B203M1 body sealant 4 is poured into this opening into which the pulling shaft 3 is inserted, so that the opening is closed. By sealing the airtight container 2 in this way, an As atmosphere is created inside the airtight container 2, and the GaAs1i! l! It is configured to prevent As dissociation from the surface of a5. Further, a heater 8 is provided on the outer periphery of the airtight container 2 to provide a growth temperature for growing the GaAs crystal 6.

The diameter between the upper and lower parts of the airtight container 2 is reduced, and this reduced diameter portion is used to prevent the As gas inside the airtight container 2 from leaking to the extent possible while balancing the pressure inside and outside the airtight container 2. A labyrinth structure 10 is provided.

B to open the lifting shaft 3 and the airtight container 20 to make the airtight container 2 airtight.
4゛ of 2O3 liquid sealant was added to form a melt seal. A labyrinth structure 10 was provided in the airtight container 2 as a buffer path to prevent diffusion of As. This labyrinth structure 10 balances the pressure inside and outside the air-tight container 2, and
Prevent leakage of As scum inside to the extent possible. The second labyrinth structure 10 is composed of a cap-shaped opening provided in the airtight container 2 and a cap that closes the cap-shaped opening, thereby forming a meandering passage.

In addition, as a buffer space, a pressure buffer container 12 made of pBN having a volume almost equal to the volume of the airtight container 2 is used as a buffer space in the labyrinth structure 1.
Continuously provided outside of 0. This pressure buffer container 12 has a hole 13 for gas inflow and outflow, and the cross section of the hole 13 is made as small as possible compared to the cross section of the container.

In this way, the airtight container 2 made of pBN is arranged inside the pressure vessel 7, and the crucible 1 also made of pBN housed therein is heated with G.
An aAs melt 5 was contained therein, and a GaAs seed crystal 1 was brought into contact with the melt from above and pulled up while rotating, thereby growing a GaAs crystal. Specifically, Ga6800g
, 110mm diameter crystal from As7450g, length 260
mm was grown. <1 at pulling speed 10mm/h
A crystal with a 00> orientation was produced. The obtained crystal is 107
It exhibits a high resistance on the order of ''Ω・cm, and the impurity concentration is 5 x 1
It was below the detection limit of 0.014cm-3 or less.

Quality reproducibility was good.

Example 2 As shown in FIG. 2, a vertical Bridgman apparatus was used.

In the case of the vertical Bridgman apparatus, in order to create an AS scum atmosphere, I) cover the entire BN crucible 21 with a pBN airtight container 22, and in order to prevent As from dissociating from the GaAS melt 25, The As placed in the chamber 22 is heated and gasified to create an As atmosphere. A heater 28 is disposed around the outer periphery of the 5° airtight container 22, which is constructed to further cover this airtight container 22 with a pressure container 27. It's heating up.

A GaAs seed crystal 31 is placed at the bottom of a vertically long crucible 21 housed in an airtight container 22 . A GaAs melt 25 is poured onto the GaAs seed crystal 31, and the melt is solidified from the bottom to obtain a GaAs crystal 26.

A labyrinth structure 30 for pressure balance is provided at the top of the airtight container 22 as described above, and pBN is attached to the outside 1;
A pressure buffer container 32 was provided which constitutes a buffer space made of plastic.
In this way, the airtight container 22 made of pBN containing the crucible 21 made of pBN is placed in the pressure vessel 27, and the lower part of the crucible G
A As seed crystal 31 is placed under the contained GaAsa liquid 25 (25)) and assimilated. Specifically, Crucible 2
After putting 6,800 g of Ga and 7,450 g of As into a chamber of
Approximately 14,250 g of 0 mm crystals were obtained. Specific resistance is 107Ω
・High resistance on the cm level, impurity concentration 5X1014cm-
It was 3 or less. Good high purity crystals were obtained.

Comparative Example 1 Pressure buffer vessel 22 was installed in the vertical Bridgman apparatus shown in FIG.
was removed to prepare a crystal. Other conditions are the same as in Example 2. The results are compared and shown in the table below.

Table Comparative Crystal Examples 1 and 2 yielded highly pure crystals, whereas Comparative Example showed Si contamination. This is considered to be because contaminated gas generated from members outside the airtight container entered the airtight container through back diffusion during growth.

As described above, according to this embodiment, the pressure buffer container is provided in addition to the pressure buffer path, and the pressure balance inside and outside the airtight container is maintained, while further improving the cushioning property of the dregs.
Minimize the leakage of elemental gases in the airtight container and prevent gas containing impurities from outside the airtight container into the airtight container.
f) Since the inflow of 'S is prevented, the desired elemental gas atmosphere can be stably maintained with good reproducibility. death·
Therefore, it is easier to control the composition of the grown crystal, there is no chance of contamination with impurities as in the past, and compound semiconductor crystals can be grown stably and safely in an environment with little thermal distortion. be able to. This can fully meet the ever-increasing demand for higher purity in the semiconductor field.

In addition, high-quality crystals can be stably grown with a simple configuration of adding a pressure buffer container to an already proposed device, which is highly economical.

In the first and second embodiments, the pressure buffer container was provided outside the passage of the labyrinth structure, but it may be provided inside the passage, that is, in the middle, as described above.

And instead of configuring the inside of the pressure buffer container as a single space,
The space may be divided into a plurality of spaces and communicated with each other.

Further, the present invention is applicable to compound semiconductors other than GaAs used in the above embodiments, such as InAs, InP, and G
Of course, it can also be applied to aP and the like.

[Effects of the Invention] According to the present invention, by providing a buffer space, it is possible to effectively prevent contamination of impurities from the outside, so that it is possible to obtain a crystal of high purity, and also to obtain a compound semiconductor crystal of stable quality. can be obtained with good reproducibility.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a configuration diagram of a lifting device according to a first embodiment of the present invention;
FIG. 2 is a block diagram of a vertical Bridgman device according to a second embodiment. 2.22...Airtight container (made of pBN), 5.25...
G a As melt, 6.26...G a As
Crystal, 7.27... Pressure vessel, 8.28... Heater, 10.30... Labyrinth structure (made of pBN), 1
1.31...GaAs seed crystal, 12.32...Pressure buffer vessel (pB pulling device according to the first embodiment, Fig. 1, vertical type according to the second embodiment), ``Rifno'' 7 device,
Figure 2

Claims (1)

[Scope of Claims] The entire crucible containing a compound semiconductor melt is covered with a highly airtight container, and the inside of this airtight container contains an elemental gas having a higher vapor pressure among the compound elements constituting the melt. In a compound semiconductor crystal growth apparatus, the atmosphere is provided in the airtight container and a pressure buffer path with a narrowed flow path communicating between the inside and outside of the container is provided, at least one of the entrance and exit of the pressure buffer path is filled with gas in the airtight container. 1. A compound semiconductor crystal growth apparatus comprising a pressure buffer container having a volume substantially equal to or larger than the volume of the space.