JPS61163187A - Process and device for preparing compound semiconductor single crystal - Google Patents

Abstract

PURPOSE:To prepare a single crystal having long size and fixed concentration of impurity by supplying additional feed material to a space between a partition wall provided in a crucible and an inside wall of the crucible and pulling a single crystal from the melt of the feed contg. the impurity in the course of feeding of the additional material. CONSTITUTION:An escaping partition wall 11 made of Si3N4, etc. is floated preventing diffusion or mixing of melt or fixed keeping the center from causing no shift while providing holes on the partition wall 11 simultaneously, for additional feed material (undoped polycrystalline particles or undoped single crystal particles) in the inside of a quartz crucible 6 in a susceptor 5 provided with a feed heater 4 to the outside periphery, contained in a high pressure vessel 1. Melt of the feed 7 and a sealing material 10 are charged to the crucible 6, and a pulling single crystal 8 is pulled at a certain weight ds/dt weight of pulled single crystal per unit time) using an upper shaft 2 for pulling crystal, and a seed crystal 9. On one hand, an additional feed 15 having 0.5-5mm particle size in a sink 13 for the additional feed is supplied as feed material 16 to the melt 7 with (1-k)ds/dt feed rate (k is a segregation coefft.) through a feed pipe 12, and a feed shutter 14, and a weight sensor 20, etc.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a gastric acid method and apparatus for m-v group compound semiconductor single crystals such as GaAs, Gap, and nP. ．． B, Zn.

The present invention provides a method and an apparatus for keeping the impurity concentration in a raw material melt constant in order to keep the concentration of impurities such as El'b and El'b constant.

[Conventional technology]

Conventionally known methods for growing compound semiconductors are broadly classified into the liquid-filled Czochralski method (IImc method) and the horizontal Bridgman method (HB method).

TJ]! In the IC method, a seed crystal is attached to a raw material melt covered with a liquid capsule (B*Os, etc.), and the crystal is grown by pulling up the crucible containing the seed crystal and raw material melt while rotating. This is the way to do it.

On the other hand, in the HB method, a raw material polycrystal is set in a quartz boat inside a quartz sealed tube, a partial pressure of group V elements that is in equilibrium with the raw material melt is applied, and the seed crystal set at one end of the quartz is gradually drawn into the heated melt. This is a method to solidify and create a single crystal.

Compound semiconductors are made by adding various impurities (doping).
By controlling the electrical properties such as n-type and p-type and crystallinity such as defect density, K is used for applications suitable for various devices.

For example, in the case of GaAs, the impurity is n-type
1, S, P-type such as Sn...neutral impurities such as Zn, B, Mul, N, P, 8b, etc.

For various devices, the more constant the impurity concentration, the more stable the characteristics and the better the yield.

[Problem that the invention seeks to solve]

However, as explained below, there are major problems with the addition of the above-mentioned impurities in the conventional method.

For example, from GaAs melt with added impurities, GaAs
When an As single crystal is pulled, the rate at which each impurity is taken into the crystal from the melt is constant. This is called the segregation coefficient.

Impurity concentration in melt OL p p O8 in crystal Initial tri in melt.

Then, k -Os/CT- The crystal weight relative to the initial melt weight is called the solidification rate (2),
The impurity concentration when the solidification rate is gK (Q is as shown in the following equation).

0-kQo(1-g)k-' Here, k varies greatly depending on each impurity.

k (When 1: From the front of the crystal to the back'
back [0 increases. Most impurities fit into this category. For example, 8i, B, Zn.

In, Bb, etc.

When k, -1: C is constant from the front to the back of the crystal. However, this type of impurity is unknown.

When k>1: From the front of the crystal to the back, C
decreases. A very small number of impurities, such as A1, meet this requirement.

The above relationship is shown in FIG.

For most impurities, k<1, but in this case, as the impurity concentration CT- in the melt increases, the impurity concentration Oθ in the crystal also increases, and its electrical solubility and crystallinity increase. There was a problem in that the crystal (lattice constant, etc.) changed and could only be used as a product up to the middle of the crystal.

SUMMARY OF THE INVENTION Therefore, the present invention aims to solve the above-mentioned problem, that is, the increase in impurity concentration in the crystal, and to provide a method and apparatus for manufacturing a compound semiconductor single crystal in which the concentration is kept constant.

[Means for solving problems]

In order to keep the impurity concentration in the crystal constant, the present invention adds non-additive (undoped) raw material polycrystal grains or undoped single crystal grains to the melt in order to keep the impurity concentration in the melt constant. It is characterized by the additional method and the apparatus.

That is, the present invention is a compound semiconductor single crystal pulling method for pulling a single crystal from a raw material melt containing impurities. A method for producing a compound semiconductor single crystal, which is characterized by replenishing the material and thereby obtaining a single crystal with a constant impurity concentration, and pulling the single crystal from a raw material melt containing impurities in a crucible provided in a hot zone. An apparatus for manufacturing a compound semiconductor single crystal using a crucible, comprising a partition wall provided in a crucible and a means for supplying undoped polycrystalline grains or undoped single crystal grains between the partition wall and the inner wall of the crucible. This is an apparatus for producing a compound semiconductor single crystal, thereby making it possible to obtain a long-axis single crystal with a constant impurity concentration even if the hot zone portion including the crucible is small.

The present invention will be described in detail below based on the drawings.

FIG. 1 is a schematic diagram showing one embodiment of the present invention, 1
is a high-pressure container, 2 is an upper shaft for pulling the crystal, 3 is a lower shaft for rotating and lifting the crucible, 4 is a heater for heating the raw material, 5 is a susceptor, 6Fi crucible (quartz, PBN, AZN, etc.), 7 is the raw material Melt, 8 is a pulled single crystal, 9 is a seed crystal, 10 is a sealant (BmOm, etc.), 11 is an additional raw material escape partition (made of SiN, BN, O, etc.), 12 is an additional raw material drop pipe (made of quartz, BN, etc.), 13 is for additional raw material retainer (
quartz, BN1 stainless steel, etc.), 14 is a shutter for dropping additional raw materials, 15 is additional raw material (particle size of 5 or less is good),
Reference numeral 16 indicates an additional raw material dropped into the raw material melt, 17 indicates a high pressure gas (N1 gas or inert gas), and 20 indicates a weight sensor.

FIG. 2 is an enlarged view of the vicinity of the crucible 6 in FIG. 1, and the meanings of the reference numbers are the same as in FIG. 1.

The features of the present invention include, in order to keep the impurity concentration of the raw material melt 7 constant, an additional raw material retainer 13, an additional raw material dropping shutter 14, an additional raw material 15, an additional raw material dropping pipe 12,
The additional raw material avoidance is to obtain the crystal by a single crystal pulling device in which the partition wall 11 is installed, and the additional raw material 15 is transferred to the dropping vibe 1.
2, crystals are grown while being added to the raw material melt 7. The partition walls 11 are used to prevent the additional raw material 16 from coming close to the crystal growth interface, thereby stabilizing the growth of the impurity-doped single crystal.

The principle and operation of the present invention will be explained below.

If the single crystal is pulled up by d8, it is only necessary to add the raw material by (1-k)as.

First, the seed crystal 9 is immersed in the raw material melt 7 containing impurities whose segregation coefficient is k, and while rotating the upper shaft 2 and lower shaft 3, the upper shaft 2 is raised, and the single crystal 8 is pulled up. go. At this time, the sealing agent 10 detects the growth weight dB/dt of the crystal per hour by transmitting the signal from the weight sensor 20 set above the upper axis.
The buoyancy due to (BmOm) is corrected and detected, and then additional raw material - (undoped polycrystalline grain) 15 (1-k) c1
g/at amount is replenished into the melt from above the sealant 10. Ba
1m has a large viscosity coefficient, so the additional raw material 16
sinks at low speed in IIItOs and floats in the melt.

In m-v group compound semiconductors such as GaAs and nP, the specific gravity of the melt is greater than the specific gravity of the crystal.

In the GaAs density i melt, Pl--5,71fl
e In the solid state, Ps-5, L6 ~ 5.31 (4- Therefore, when the floating additional raw material 16 approaches the vicinity of the crystal, the growth becomes unstable), and a single crystal cannot be formed, so the partition wall 11 is provided,
Prevent the floating additional raw material 16 from coming near the crystal. Furthermore, the partition walls 11 are floated in the melt so that the additional melted raw material and the melt near the crystals are sufficiently diffused and mixed, or
A hole is provided in the partition wall 11. Also, a collar is attached or fixed to the bottom of the crucible so that the center of the partition wall 11 does not shift.

The temperature distribution on the surface of the melt in the radial direction of the crucible is such that the temperature increases toward the periphery of the crucible, and is 3 to 15° C. higher at the periphery of the crucible than at the center of the crucible. Therefore,
Although the additional raw material 16 continues to grow as a crystal at the center of the crucible, it is sufficiently dissolved in the melt. If the particles of the additional raw material 16 are too large, it will be difficult to dissolve, and if the particles are too small (fine powder), it will be difficult to sink in the highly viscous BIO3, so an additional raw material with a fin diameter of 115 to 5 is optimal.

When the single crystal is pulled up at dsi/at in this manner and the additional raw material (f - k) da/6 is supplied, a single crystal with a constant concentration of impurities can be obtained as k.

An example of an embodiment of the structure of the partition wall 11 for avoiding additional raw materials is shown in FIG. 3 (a).
) and (1)j to FIG. 5(a) and φ). In each figure, (a) is an explanatory view of a part in the vertical direction, and (a) is a cross-sectional view in the horizontal direction.

Fig. 5 (al and 2) shows a cylindrical shape with a K collar 18 attached so as not to be eccentric with respect to the crucible 6, and this boxwood 1.
Additional raw material enters between the crucible 6 and the partition wall 11 according to 8.

In this form, the partition wall 11 needs to float in the raw material melt 7 so that the melt near the crystal and the melt containing the additional raw material mix well.The material is silicon nitride (81sN+).
Alternatively, use boron nitride (Bli), carbon (C), or KBN-coated materials, and devise measures such as attaching a weight to the top in order to control the amount that sinks into the raw material melt.

4(a) and ('b) show that a frame 1 is attached to the bottom of the partition wall 11.
9 is attached. Boxwood 1 if fixed to the bottom of the crucible
8 is not necessary.

FIGS. 5(a) and 5('b) show a method of fixing the cylindrical partition wall 11 to the bottom of the crucible. A hole 20 is provided at the bottom of the partition wall 11 so that the raw material melt can mix.

As is clear from the above description, the present invention adds one raw material to the process, so the hot zone including the crucible can be downsized, and a long-diameter undoped single crystal ingot can be manufactured with this compact device. Because the hot zone is small,
The temperature near the crystal solid-liquid interface is well controlled (because the time constant is small and responsiveness is good), and a long film can be obtained with one charge, so there is little loss in charging time and productivity is improved.

(Example) Using an apparatus as shown in FIG.
A single crystal was pulled.

Undoped Gamu 8 polycrystalline 4000F crucible (F
Made by BI) 6 inch diameter Room
60 C1f bulkhead (FBI on carbon
Coat, place a heavy layer of Mo gold on top) Pull up the S1 dope Game crystal with an outer diameter of 5 inches and a thickness of 3cm and 2 inches (about 501φ).

Pulling speed 8 dew/H Upper shaft rotation speed 7 rpm 1 Lower shaft rotation speed 15 r
Based on the segregation coefficient of pm81, Q, 14 Ga 8 melt 1c! 1? Add i to [L1428F.

The initial concentration of GaAa crystals is 5 ppm by weight.

2000 yen for additional raw materials (GaAa grains)? (5vm diameter) was prepared and replenished at a rate of 1171F per minute. The S1-doped single crystal was pulled up by about 2kll. The 81fi degree in the crystal was uniform from the front of the crystal to the pack, and was 5 ppm by weight.

FIG. 6 shows a comparison of the daily concentration distribution in a GaAs single crystal in the case of the present invention (solid line A) and the case of the conventional method (dotted line).

〔Effect of the invention〕

By replenishing the raw material melt with the raw material (undoped polycrystal), the impurity concentration in the raw material melt can be kept constant;
The impurity concentration of the pulled single crystal becomes constant. There is no adverse effect on the partition walls in the crucible and the supply of raw materials (undoped polycrystalline grains), and stable growth of one crystal can be achieved at the same time. In addition, the melt near the center of the crucible and the melt containing the raw material (undoped polycrystal) pass under the partition wall and mix well, forming a uniform melt.

The present invention relates to fii, B, Zn, In, Eib, etc.
This method can be applied to pulling a single crystal containing as many as 1,000 impurities, such as GaAg (in GaAg).

Further, the apparatus of the present invention can stably manufacture small-sized, long-diameter undoped single crystal ingots, and has good productivity.

Brief Explanation of the East Surface Figure 1 is a diagram illustrating one embodiment of the present invention, Figure 2 is an enlarged view of the vicinity of the crucible 5 in Figure 1, Figure 3 (a) and width), 4 (- and (1)) and FIG. 5 (a) and the peaks are diagrams showing examples of the structure of the partition wall 11, and FIG.
FIG. 7 is a diagram schematically showing the relationship between impurity concentration, k value, and solidification rate in each part of a GaAa single crystal.

Claims (3)

[Claims] (1) In a compound semiconductor single crystal pulling method for pulling a single crystal from a raw material melt containing impurities, undoped polycrystal grains or undoped single crystal grains are supplied between a partition wall provided in a crucible and an inner wall of the crucible, A method for producing a compound semiconductor single crystal, characterized in that a single crystal with a constant impurity concentration is thereby obtained. (2) Replenishment of undoped polycrystalline grains or undoped single crystal grains is based on the pulled single crystal weight d per unit time.
s/dt, the method for manufacturing a compound semiconductor single crystal according to claim (1), wherein (1-k) ds/dt per unit time. (3) A device for producing a compound semiconductor single crystal by pulling a single crystal from a raw material melt containing impurities in a crucible provided in a hot zone, comprising a partition wall provided in the crucible and a connection between the partition wall and the A means for supplying undoped polycrystalline grains or undoped single crystal grains between the inner wall of the crucible, thereby obtaining a long-axis single crystal with a constant impurity concentration even if the hot zone portion including the crucible is small. Compound semiconductor single crystal manufacturing equipment.