JPH0684278B2 - Method for manufacturing compound semiconductor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a compound semiconductor in which a III-V group compound semiconductor such as GaAs and InP is grown by a liquid-encapsulated Czochralski method.

[Conventional technology]

Conventionally, in the manufacturing process of compound semiconductors by the liquid-encapsulated Czochralski method (hereinafter referred to as LEC method), indium (In) or the like is used when growing a semi-insulating GaAs crystal for the purpose of suppressing the generation and propagation of dislocations. However, when growing the semi-insulating InP crystal, gallium (Ga) or the like is added to the melt.

[Problems to be solved by the invention]

This crystal low dislocation technology utilizes the effect of suppressing the generation and propagation of dislocations during crystal growth when impurities are added to the melt. Axial temperature gradient from conventional 100 ℃ / cm or more to several tens
It is known that the effect of adding impurities can be further enhanced and the amount of the impurities added can be reduced by using the method in which the temperature is adjusted to ℃ / cm (10 to 50 ℃ / cm).

However, when the crystal growth is performed with the temperature gradient reduced in this way, the smaller the temperature gradient, the more abnormal growth called compositional supercooling occurs from the time when the solidification rate g is small, and the crystal is grown. The problem is that not all of the crystals can be used.

In view of the above circumstances, an object of the present invention is to provide a method for producing a compound semiconductor by the liquid-encapsulated Czochralski method without causing abnormal growth based on compositional supercooling in a crystal pulling step with a low temperature gradient. is there.

[Means for solving problems]

The method for producing a compound semiconductor of the present invention is a method for producing a compound semiconductor by a liquid-encapsulated Czochralski method (LEC method) in which impurities are added to a melt, and a temperature gradient ΔT ( g), where ΔT (g = 0) is the melt temperature gradient at the start of crystallization, and ΔT (g) is the segregation coefficient k.
= [Delta] T (g = 0) * (1-g) ^<k-1 > is held and crystal growth is performed.

〔Example〕

 Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing the relationship between the temperature gradient V _T in the melt and the solidification rate g in the present invention, showing how the temperature gradient V _T is increased in proportion to the increase in the solidification rate g. Is.

As is already well known, in the crystal pulling of the compound semiconductor by the LEC method, the conditions that cause compositional supercooling are When the inequality sign of is established. However, each symbol in relational expression (1) is Represents various quantities of.

Here, m on the right side of the inequality is an amount that depends on the impurity concentration, and D is an amount that depends on the rotation conditions of the crystal and the crucible. Since the dependences are small, respectively, during crystal growth,
The right side can be regarded as a constant value.

Therefore, if the temperature gradient ΔT in the melt is also changed at the same time in accordance with the amount of change in the impurity concentration C in the melt that changes with the progress of crystal growth, ΔT / C on the left side always takes a constant value. This means that crystal growth can be performed without causing compositional supercooling.

Therefore, the general formula expressing the impurity concentration C (g) when the solidification rate is g is C (g) = C ₀ k × (1-g) ^k−1 (2) (where C ₀ : initial impurity (Concentration), the temperature gradient ΔT in the melt is constantly changed in proportion to (1-g) ^k−1 during the crystal growth, thereby making it possible to avoid abnormal growth due to compositional supercooling. . That is, when the initial temperature gradient is V _T (g = 0), the temperature gradient V _T (g) at the solidification rate g can always follow the change of the impurity concentration C (g) as shown in FIG. So V _T (g = 0) ×
If the relationship of (1-g) ^k-1 is maintained, abnormal growth can be avoided.

Therefore, taking as an example the case where In (indium) is added to a solution to grow a GaAs crystal, indium (In) is added to the melt at a concentration of 1 × 10 ²⁰ cm ⁻³ or more. Assuming that the temperature gradient in the crystal pull-up axial direction when a dislocation-free 2-inch GaAs crystal was obtained was about 20 ° C / cm, the crucible heating device should have a multi-stage heater structure to change the power distribution, or If the temperature gradient ΔT is made to follow the change in the solidification rate g by means of changing the relative position with respect to the crucible, a GaAs crystal can be grown over a long length without causing compositional supercooling.

FIG. 2 is an actual measurement diagram in which the relationship between the relative position of the crucible and the heater of the crucible heating means and the temperature gradient ΔT in the melt in the present invention is obtained, and the desired temperature can be obtained simply by sequentially changing the relative position of the crucible and the heater. It has become clear that it can cause a gradient change. This relative position control can be performed very easily and precisely by using a computer control method.

〔The invention's effect〕

As described above, according to the present invention, impurities are added.
Since the temperature gradient in the melt in the LEC crystal growth method can be changed in proportion to the increase in the solidification rate, it has the effect of stably producing a compound semiconductor crystal over a long period without causing cell growth due to compositional supercooling. .

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the temperature gradient V _T in the melt and the solidification rate g in the present invention, and FIG. 2 is the relative position of the crucible to the heater of the crucible heating means in the present invention and the temperature gradient Δ in the solution. It is the measurement figure which calculated | required the relationship with _T. Delta _{T ......} temperature in solution gradient (℃ / cm), g ...... solidification ratio (%), k ...... segregation coefficient, ΔT (g = 0) melt temperature gradient during ...... crystal growth start, [Delta] T ( g) ... Melt temperature gradient when the solidification rate is g.

Claims (1)

[Claims] 1. A method for producing a compound semiconductor by a liquid-encapsulated Czochralski method (LEC method) in which impurities are added to a melt, wherein a temperature gradient ΔT in the melt at a solidification rate g.
(G) is the melt temperature gradient at the start of crystallization expressed by ΔT (g =
0), where the segregation coefficient is k, ΔT (g) = ΔT (g =
0) x (1-g) ^k-1 is maintained, and a crystal growth is performed, The manufacturing method of the compound semiconductor characterized by the above-mentioned.