JPH01108200A - Production of sic ingot - Google Patents

Abstract

PURPOSE:To obtain SiC ingot in which impurities are doped in an amount of <=10<19>/cm<2> without causing polycrystallization, by sublimating a SiC raw material having different impurities concentration in specific order and growing a single crystal. CONSTITUTION:A SiC single crystal 9 is grown on a SiC seed crystal 6 by sublimating a SiC raw material 8 in which <10<19> impurities are doped and successively a SiC raw material in which >=10<19>/cm<2> impurities are doped is sublimated to further grow SiC single crystal 11 on the surface of SiC single crystal 9 and 10 (10 is a mixed crystal consisting of mixture of SiC single crystals having <10<19> and >=10<19> impurities concentration).

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a method for producing a TFSIC (silicon carbide) ingot.

(b) Conventional technology SiC single crystal is physically and chemically stable and is a material that can withstand high temperatures and radiation, so it is expected to be used as an environmentally resistant material for cow humiliation.

Among them, 6H type SiC single crystal has a temperature of about 3°Oe at room temperature.
It has a forbidden band width of V and is used as a material for blue light emitting diodes.

In the case of growing SiC single crystal ingots, sublimation is mainly used. In addition, as a method for growing a p-type SiC single crystal by this elevation and removal, AL is added as an impurity in advance.

(1) SiC* material doped with 5 min)
SiC single f9 is heated and sublimated under a low pressure of 10 Torr.
The problem that the invention seeks to solve is that in the above method, for example, when growth is performed using only a SiC raw material doped with At as an impurity of 1019/d or more, the grown SiC ingot becomes a polycrystalline ingot. It turns into

For this reason, it has been difficult to produce a SiC single crystal doped with 1017j or more of At.

Although the cause of prayer is not pure, At is 1of as a raw material.
When using SiC doped with 7j or more, a plurality of crystals are formed on the surface of the SiC seed crystal at the initial stage of growth, and Atp
It is thought that this is because the supply of children is too large, so that a boundary region where only AL exists is generated between the island-like crystals centered around the growth ridge. On the other hand, the amount of At doped is 10
When Mitsuru Koeki's SiC is used as a raw material, the above-mentioned polycrystallization does not occur. Incidentally, such a phenomenon is the same even when B%G Hatake or the like is used as an impurity.

B) Means for Solving the Problems The present invention has been made with an eye on the matter, and its unique feature is that impurities of less than 1054 are allowed to grow.

(E) Effect According to the proposed method, SiC doped with an impurity of 1019/d or more is regularly arranged on the surface due to the active energy of the SiC single crystal surface.

(f) Example FIG. 1 is a sectional view for explaining an example of the present invention, (1) shows a crucible made of high-purity graphite with an inner diameter of 53 mm, (2) I/i A gas concentration means arranged on the crucible, (3) a communication hole in which 5P was thrown into the IIi move,
The inner diameter of the communication hole gradually decreases upward from the crucible (1) side. 14) is a lid disposed on the gas concentration means iZJ, and (5) is a substrate holding part, which is formed on the inner surface of the lid 14) facing the communication hole (3). . (6) is a nine-SiC seed crystal formed, for example, by the Acheson method, and the nuclide crystal is fixed on the surface of the holding part (5). Ia) is a first raw material made of SiC doped with 101 At or more, and the raw material is stored in a crucible (1) that is 0.5 mouths apart from the side wall of the crucible (1). There is. (8) is a second raw material made of SiC with an AA doping amount of less than 1o 19A , and this raw material is the side wall of the crucible 11) and the %1 raw material 17
) and is also deposited on the first raw material 17). The thickness of the second raw material (8) deposited on the first raw material (7) to be prayed is about 15 mm.

In a sudden situation, the seed crystal temperature is 220P to 2400℃.
, raw material temperature 2300~2500℃, temperature gradient between seed crystal and thread material 5~20℃/α, gas pressure in the reaction system 1~
The raw materials are JA-fermented under conditions of 10 Torr. The seed crystal and the like are heated by a high-frequency heating coil (not shown) wound around the heating element 1).

When sublimating raw materials under the desired conditions, the first raw material P)1
7> is coated with the qPJ2 raw material (8), and the second
Since the raw material (8) is closer to the 1M thermal coil that is the heating source, only the second raw material (8) sublimes first, and the At doping concentration is 1017- on the surface of the seed crystal +6) shown in Figure 2.
The first SiC single crystal 19) is grown. After that one,
Of the second fA material (8) above! + 1st raw material (7
) When the surface is exposed, the first M material (7) also begins to deteriorate, so the SiC single crystal (low concentration crystal) with an At doping concentration of less than 100 nm on the surface of the first SiC$ crystal (9) and the A
At the time of collection, the amount of sublimation of the second raw material (8) is large at first, so a mixed crystal αG with a high proportion of low-concentration crystals grows, but during ty, the sublimation of the second raw material (8) While the amount of the first raw material 171 increases, the amount of the first raw material 171 gradually increases until all of the second raw material (8) sublimates, and only the first raw material (71) sublimates. Therefore,
The mixed crystal t101 is grown in the growth direction (
In FIG. 2, the ratio of highly concentrated crystals becomes excessively high toward the bottom (in the downward direction). If you continue to be the ward chief, ¥J1 raw materials fjf17
1 will sublimate, so the 25th iC single crystal α with At doping 11 degrees of
1) will grow. Therefore, by continuing the growth of a certain second SiC quasicrystal l11) for a long time, AA becomes 1
A SiC ingot doped with 019/1 or higher can be produced. - In this way, the A4 doping concentration is 1019/1 in the 1st S
Although it is not clear why some SiC crystals do not become polycrystalline when a SiC crystal with an At doping concentration of 1019/1 or more is formed on the C single crystal (9), the above 5iCFi
Since the surface of the first SiC single crystal (9) on which the crystal is grown is active, the activation energy increases the A of 10'7j or more.
It is presumed that this is because the L-doped SiC is regularly arranged.

In this example, the second yA material 18) was placed in the crucible (1) so as to temporarily accumulate around the first raw material (7), but the first raw material + 7) was simply placed at the bottom of the crucible (1). However, even if 'P;2 raw material (8) is placed on top of it, ht? - It is possible to grow a SiC single crystal with a concentration of 101 or more. In addition, the principal's side uses At as an impurity, and the friend uses B as an impurity.

Similar results can be obtained using G*, Sc, etc.

(g) Effects of the Invention According to the present invention, a SiC ingot doped with impurities of 1019/d or more can be produced without causing polymorphism.

[Brief explanation of the drawing]

FIG. 1 is a sectional view for explaining one embodiment of the present invention.
FIG. 2 is an Ffr plane view for explaining the growth rate of SiC crystal in Example 2. t6)-S i C seed crystal, Ia)...first raw material (
SiC* material doped with impurities with 10'9/cd payment), 181...Kyo 2 raw material <1o+7# SiC raw material doped with impurities of ice bottle)

Claims (1)

[Claims] (1) After growing a SiC single crystal on a SiC seed crystal by sublimating a SiC raw material doped with impurities of less than 10^1^9/cm^3,
A method for producing an SiC ingot, which comprises sublimating a SiC raw material doped with impurities of cm^3 or more to further grow a SiC single crystal on the surface of the SiC single crystal.