JPH06128084A - Production of single crystal - Google Patents

Abstract

PURPOSE:To enable the production of a bulk mixed crystal, capable of suppressing and preventing the raw material melt composition and temperature from changing and having a large crystal length in a straight body part in a liquid-encapsulated Czochralski process to which a salute feeding method is applied. CONSTITUTION:This single crystal of a ternary compound semiconductor mixed crystal is grown according to a liquid-encapsulated Czochralski process to which a solute feeding method is applied. In the process, a ternary melt equilibrated with a mixed crystal at the target mixed crystal ratio in a pseudobinary phase diagram is used as a raw material melt and the temperature of the growth interface during the growth is regulated to an equilibrium temperature. A polycrystalline mixed crystal having a composition equal to the target mixed crystal ratio (X) is used as a solute. The resultant solute in an amount equal to the weight increase of the single crystal during the growth is dissolved in the raw material melt.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a single crystal of a ternary compound semiconductor mixed crystal. In particular, the composition of the mixed crystal has a pseudo-binary composition represented by the rational formula (AB) _1-X (CB) _X , and one of the components has a higher segregation tendency than the other components (I
The present invention relates to a method for producing a single crystal having a uniform composition of a ternary compound semiconductor mixed crystal such as nGa) Sb, (InGa) P, (InGa) As, or In (AsP).

[0002]

2. Description of the Related Art Unlike ternary compound semiconductors, ternary compound semiconductor mixed crystals have characteristic values (physical property values) of substances determined by the electronic state represented by a forbidden band width by selecting a mixed crystal composition. There is a degree of freedom in crystallographic structure parameters such as lattice constants and lattice constants, and their usefulness is drawing attention. For industrial use, a method for producing a single crystal with high reproducibility and high mass productivity is required. Already, liquid sealed Czochralski
Applying (LEC) method, quasi-binary composition (AB)
By using the raw material melt represented by _1-Y (CB) _Y , the composition of the mixed crystal is a ternary compound having a pseudo binary system represented by the rational formula (AB) _1-X (CB) _X. The possibility of growing a bulk single crystal of a mixed compound semiconductor mixed crystal has been proposed.

For example, Bonner et al. Of Bellcore, Inc. of the United States Proc the result of pulling and growing a bulk crystal of an (InGa) As mixed crystal by a LEC method using a seed crystal of GaAs or an (InGa) As mixed crystal having approximately the same lattice constant.
edings of the 6th Conf
ence on Semi-insulating III
-V Materials, Toronto 199
0 p. Published in 199-204. However, according to the published results, as the growth of the crystal proceeds, the component Ga having a large segregation coefficient in the raw material melt is preferentially taken into the crystal, and the concentration of Ga in the raw material melt sharply decreases. There is. Among the components in the raw material melt, as the concentration of Ga having a large segregation coefficient decreases, it is correspondingly grown (InGa) A.
The mixed crystal composition of the s mixed crystal gradually changed, and the composition of the obtained bulk crystal was not uniform.

Further, in order to grow a bulk single crystal of a ternary compound semiconductor mixed crystal having a uniform composition by applying the LEC method,
The invention of a method of replenishing a component having a large segregation coefficient to suppress the change of the component in the raw material melt is disclosed in, for example, JP-A-60-6579.
No. 9 or JP-A No. 62-3097. In the conventional method represented by the above two inventions, a solute control supply method of dissolving a compound semiconductor in a raw material melt is applied to a method of supplementing a component having a large segregation coefficient. As a report example in which a bulk single crystal of a III-V group ternary compound semiconductor mixed crystal was grown by the LEC method using the same solute controlled supply method, Ga was used as a supplementary source of the component element Ga having a large segregation coefficient.
An example of growing an (InGa) Sb mixed crystal by supplying Sb as a solute is shown in Research Report of Institute of Electronics Engineering, Shizuoka University, vol. Two
0 p. 193-197 (1985), and an example of growing (InGa) As mixed crystal by supplying GaAs as a solute as a replenishment source of a component element Ga having a large segregation coefficient, J.
individual of Crystal Growth
vol. 113 p. 485-490 (1991), respectively. In addition, the invention described above (JP-A-60-657)
No. 99), a means of using a multi-component compound semiconductor mixed crystal containing a component having a large segregation coefficient as a solute for supplying a component having a large segregation coefficient is proposed, but the composition range of the mixed crystal used as a solute is specified. However, as an example, a compound semiconductor GaAs is used as a solute.

As described above, in the conventional solute control supply method, as the solute to be fed into the raw material melt, the component having a large segregation coefficient in the pseudo binary system composition is mainly replenished by the binary compound. . Even in the case of the solute controlled supply method mainly using a binary compound as a solute, it is possible to prevent a sharp decrease in the concentration in the raw material melt due to the incorporation of a component having a large segregation coefficient in the raw material melt into the crystal. The effect is recognized to some extent.

[0006]

However, in the conventional solute control feeding method, as a solute to be fed into the raw material melt, a component having a large segregation coefficient in the pseudo binary system composition is mainly supplemented by the binary compound. Therefore, the remaining amount of melt gradually decreases due to the growth of crystals. When the melt remaining amount decreased, the composition of the raw material melt could not be kept constant because of variation in the control of the amount of solute supplied into the raw material melt. Therefore, the mixed crystal composition of the grown crystal changes in the growing direction, and the obtained single crystal does not have a uniform composition. Therefore, there is a problem that a large number of industrially usable substrates for epitaxial growth cannot be manufactured from the obtained single crystal.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for producing a single crystal of a ternary compound semiconductor mixed crystal having an extremely uniform mixed crystal composition.

[0008]

According to the present invention, in growing a single crystal of a ternary compound semiconductor mixed crystal having a predetermined target mixed crystal ratio X by a liquid-encapsulated Czochralski method, the ternary compound semiconductor is used. In the pseudo-binary phase diagram that describes the solid-liquid phase equilibrium of a mixed crystal, the temperature on the solid line where the pseudo-binary composition is the target mixed crystal ratio X is the temperature T, and Temperature T
And a ternary melt of composition Y is used as a raw material melt, and the temperature at the interface between the raw material melt and the liquid sealant during growth is the temperature T And a polycrystal of a ternary compound semiconductor mixed crystal equal to the target mixed crystal ratio X is used as a solute, and the polycrystal solute having a weight equal to the weight increase amount of the growing single crystal is dissolved in the raw material melt. Is a method for producing a single crystal.

[0009]

When a crystal is grown from a ternary melt, the pseudo-binary phase diagram schematically shown in FIG. 2 describes the solid-liquid phase equilibrium of the ternary compound semiconductor mixed crystal. A certain temperature T
When the quasi-binary composition on the liquidus line in is represented as Y, a ternary melt having the above composition Y is used as a raw material melt, and precipitation occurs only when the temperature for crystal growth is the temperature T It can be seen that the crystal composition is X, which is a pseudo-binary composition that represents a solidus line that equilibrates at the temperature T. Therefore, in order to make the composition of the precipitated crystal constant, it is necessary to make the composition of the raw material melt and the crystal growth temperature constant.

In the present invention, since the polycrystal solute having a weight equal to the weight increase amount of the single crystal during the growth is dissolved and supplied, the amount of the raw material melt does not change during the growth. Further, since the polycrystal solute having the mixed crystal ratio X equal to the target mixed crystal ratio X of the single crystal being grown is supplied, in principle, in the pseudo binary system phase diagram schematically shown in FIG. During the growth, the melt composition does not change from the initial composition represented by the pseudo-binary composition Y on the phase line. At the same time, by using a polycrystal having the same composition as the ternary compound semiconductor mixed crystal being grown as the solute to be supplied, to compensate for the decrease accompanying the crystal growth of the component having a large segregation coefficient in the raw material melt, Even if the composition of the single crystal is slightly changed by accident during the growth, the composition of the raw material melt hardly changes.

In the present invention, since the composition and amount of the raw material melt can be kept constant during the growth, the temperature at the interface between the raw material melt and the grown crystal is the optimum temperature for growing the single crystal (3 in FIG. 2) at the start of the growth. When the melting point T) of the original compound semiconductor mixed crystal is adjusted, the surface temperature of the raw material melt can be easily maintained at the initial temperature during the subsequent growth. Also, during the growth, since the raw material melt is kept at the same amount as at the start of the growth, a sudden thermal disturbance due to an external factor (eg, fluctuation of thermal convection of high-pressure gas in the growth furnace) occurs. Moreover, thermal disturbance can be absorbed by the large heat capacity of the entire raw material melt. Therefore, it is possible to prevent a problematic temperature change at the solid-liquid interface between the grown crystal and the melt.

With the above operation, the composition and temperature of the raw material melt can be kept constant during the growth, so that the composition of the grown single crystal determined by the composition and temperature of the raw material melt can be controlled to the target composition, and the conventional manufacturing method can be used. It is possible to prevent the change in composition in the growing direction of the grown single crystal, which was the problem of (1). Furthermore, even when the composition of the single crystal is slightly changed during the growth due to thermal disturbance or accidental change in the composition and temperature of the raw material melt can be made extremely small, and local changes near the solid-liquid interface can be achieved. Composition supercooling can also be prevented, and generation of polycrystals due to composition supercooling can also be prevented. As a result, a single crystal of a ternary compound semiconductor mixed crystal having an extremely uniform mixed crystal composition can be produced.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a conceptual diagram showing a method for producing a single crystal of a ternary compound semiconductor mixed crystal according to the present invention. The outline of the manufacturing apparatus used in the examples is similar to that of the liquid-sealed Czochralski apparatus conventionally used for manufacturing a single crystal of a binary compound semiconductor. Crucible 2 for holding raw material melt
Is supported on a lot shaft mechanism for rotating and moving the crucible 2 up and down.
A weight sensor for measuring the weight of the crucible and monitoring the weight of the raw material melt 7 is attached. A weight sensor for monitoring the weight of the grown single crystal 5 is attached to the rotary pulling shaft for fixing and holding the seed crystal 4 for pulling the single crystal 5 by rotation. This single crystal weight sensor
Is mainly used for automatic control of the diameter of the grown crystal. The temperature of the raw material melt 7 can be monitored by a temperature sensor installed at the bottom of the crucible 2 and automatically controlled to a predetermined temperature.

The polycrystalline solute 6 is held and fixed from above the crucible 2 using a mechanism similar to a rotary pulling shaft. A weight sensor similar to the single crystal weight sensor described above is attached to the holding mechanism for the polycrystalline solute 6, and the weight of the melted polycrystalline solute 6 can be monitored.
The polycrystalline solute 6 and the tip of the holding and fixing shaft are housed in a shield 8 in order to prevent them from being cooled by the ambient atmosphere gas, and an upper end of which is provided with an auxiliary coil heater for heat retention. . By this heat retention method, the polycrystalline solute 6 is kept at substantially the same temperature as the raw material melt 7, so that it can be easily dissolved and the composition of the raw material melt 7 can be prevented from changing during crystal growth. .

Using the above single crystal manufacturing apparatus, (InG
a) A method of growing an As mixed crystal is described below. As an example, an example of a ternary compound semiconductor mixed crystal having a mixed crystal composition of (In _0.1 Ga _0.9 ) As will be described. Shown as a concept diagram in FIG. 3, the solid phase of the mixed crystal - the pseudo-binary system phase diagram describing the equilibrium between the liquid phase, in the solidus on 11 (In _0.1 G
(In _0.45 Ga _0.55 ) A represented by the pseudo binary liquid phase composition Y on the liquidus line 12 equilibrating with the composition X of a _0.9 ) As.
Binary compounds InAs and GaAs so as to have a composition of s
Is weighed. The weighed InAs and GaAs and the liquid sealant 3 (B ₂ O ₃ ) are put into the crucible 2 and used as a starting material. The starting material is a ternary melt having a composition of (In _0.45 Ga _0.55 ) As, which is once heated to a temperature higher than the temperature T in this pseudo binary system phase diagram shown in FIG. To obtain a uniform raw material melt 7.

The polycrystalline solute 6 has a target mixed crystal composition (In
A ternary melt having the same composition as _0.1 Ga _0.9 ) As is rapidly cooled and solidified and formed into a circular rod shape. During the step of melting the raw material melt 7, the polycrystalline solute 6 is evacuated above the crucible 2 to a position where it is not heated by the heating heater-1 like the seed crystal 4. The temperature of the raw material melt 7 is gradually lowered to adjust the interface temperature between the raw material melt 7 and the liquid sealant 3 (the surface temperature of the raw material melt) to the growth start temperature T. In this embodiment, the growth start temperature T is 1130 ° C. Immediately before the start of growth, the polycrystal 6 is brought into contact with the raw material melt 7. At this time, since the raw material melt 7 is already saturated due to the adjustment of the interface temperature described above, the weight of the polycrystalline solute 6 does not increase or decrease even if the polycrystalline 6 and the raw material melt 7 are brought into contact with each other. As a seed crystal 4, a GaAs seed crystal (4 mm square) having a growth orientation <100> is used to start seeding and growth.

The condition for growing the single crystal is that the number of rotations of the crucible 2 is 2
5 rpm (clockwise), rotation speed of seed crystal 4 (rotary pulling shaft) 10 rpm (counterclockwise), pulling speed 1.2 mm
/ H. During the growth, the weights of the single crystal 5 and the raw material melt 7 are monitored, the polycrystalline solute 6 having the same weight as the grown crystal weight is dissolved, and the height (position) of the crystal growth interface of the raw material melt 7 is kept constant. And the interface temperature is controlled to be constant. The raw material melt 7 is forcibly convected by the rotation of the crucible and the grown crystal, and the component of the polycrystalline solute 6 which is dissolved near the outer periphery of the crucible is rapidly supplied near the crystal growth interface. In this embodiment, in the straight body part of the single crystal 5, a normal crystal weight method is used, and the pulling rate is 1.2 mm /
The crystal diameter is automatically controlled by slightly changing the value of h.

By the above method, a single crystal of a ternary compound semiconductor mixed crystal (target mixed crystal composition (In _0.1 Ga _0.9 ) As) having a diameter of 25 mm and a crystal length of the straight body portion of 20.5 mm was grown,
EPM variation in mixed crystal composition in the growth and radial directions
A (Electron Probe Micro-An
It was evaluated by the alysis method. The mixed crystal composition in the crystal growth direction is within a range of 0.9 ± 0.03, except for a very small part which is in contact with the seed crystal 4 (GaAs) immediately after seeding. The variation in Ga composition in the radial direction in the straight body portion is also within the measurement accuracy of the EPMA method. Further, as a result of confirming reproducibility of the mixed crystal composition by growing a single crystal having a size of several degrees, a variation of the Ga composition in the above crystal growth direction with respect to the target mixed crystal composition of 0.9 A reproducibility as high as 0.03 was obtained.

As a comparative example, except for the composition of polycrystalline solute,
A mixed crystal single crystal having a target mixed crystal composition (In _0.1 Ga _0.9 ) As was grown using the ternary starting material having the same composition (In _0.45 Ga _0.55 ) As, the growth apparatus and the growth conditions as in the above-mentioned examples. . In this comparative example, the target mixed crystal composition (In
A polycrystal having a composition different from _0.1 Ga _0.9 ) As, a ternary mixed crystal having a mixed crystal composition (In _0.05 Ga _0.95 ) As, or GaAs is used as a polycrystal solute. According to the conventional method, the Ga composition of the raw material melt 7 was estimated from the weight of the grown crystal, and an attempt was made to control the dissolved amount of the polycrystalline solute so as to compensate for the decrease in the Ga composition of the raw material melt 7. However, in any of the examples in which polycrystalline or GaAs having a composition different from the target mixed crystal composition (In _0.1 Ga _0.9 ) As is used as the polycrystalline solute, the grown crystal grows due to the variation in the control of the amount of dissolution of the polycrystalline solute. The compositional change in the growth direction was large, and the variation as the Ga composition reached about ± 0.07. Further, as the crystal growth progresses, dislocations are generated due to a change in the composition of the grown crystal, or polycrystals are generated when the dislocation density is high. Further, the amount of polycrystalline solute dissolved was insufficient, the composition of the raw material melt 7 was not saturated at the growth temperature, and separation of the crystal and the melt (melt breakage) often occurred. When the above polycrystal is generated, the composition change in the growth direction of the grown crystal is particularly remarkable immediately before the occurrence of the polycrystal, and the cause of the abnormal occurrence of crystal defects due to the lattice mismatch accompanying the change in the composition of the grown crystal is This is probably because the composition of the raw material melt changed significantly.

The method for growing the crystal of the (InGa) As mixed crystal has been described above, but (InGa) Sb,
In the production of a single crystal of a ternary compound semiconductor mixed crystal having a pseudo binary system composition such as (InGa) P or In (AsP), one of which has a stronger segregation tendency than the other, Based on the pseudo-binary phase diagram that describes the solid-liquid phase equilibrium of the above ternary compound semiconductor mixed crystal, by selecting an appropriate growth temperature and composition of the raw material melt, It is possible to apply the above method to the growth of a single crystal of a bulk mixed crystal.

[0021]

As described above, according to the present invention, as the single crystal of the ternary compound semiconductor mixed crystal grows, the composition variation of the component having a large segregation coefficient in the raw material melt and the temperature of the raw material melt tend to occur. Since fluctuation can be easily prevented,
The mixed crystal composition of the grown crystal can be kept constant.
Further, since there is no change in the mixed crystal composition of the grown crystal, it is possible to produce a long bulk mixed crystal having a uniform composition in the growing direction without causing polycrystal formation or melt breakage during the growth. . The in-plane mixed crystal composition distribution and the corresponding lattice constant distribution of the substrate prepared from the bulk mixed crystal single crystal having a uniform composition in the growing direction are extremely small. By using the substrate having a uniform lattice constant distribution obtained by the present invention, it is possible to obtain the lattice matching between the epitaxially grown film and the substrate over the entire surface of the substrate, and thus it was not possible to fabricate with a conventional binary compound semiconductor substrate. Therefore, it becomes possible to fabricate a semiconductor device having characteristics that are not available in the past.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a principle of a method for producing a single crystal according to the present invention and a production apparatus used therefor.

FIG. 2 is a conceptual diagram of a pseudo-binary phase diagram that describes the solid-liquid equilibrium of a ternary compound semiconductor mixed crystal.

FIG. 3 is a schematic diagram of a pseudo-binary phase diagram that describes the solid-liquid equilibrium of (InGa) As mixed crystals.

[Explanation of symbols]

In the figure, each reference numeral is 1 ... Heating heater, 2 ... Crucible, 3 ... Liquid sealant (B ₂ O ₃ ), 4
... seed crystal, 5 ... grown single crystal (mixed crystal ratio X), 6 ... polycrystalline solute (ternary compound semiconductor mixed crystal equal to mixed crystal ratio X),
7 ... Raw material melt (ternary melt of pseudo-binary composition Y), 8
... Polycrystalline solute heat insulation shield, 9 ... Heat insulation auxiliary coil heater.

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[Procedure amendment]

[Submission date] December 28, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction content]

In the present invention, since the composition and amount of the raw material melt can be kept constant during the growth, the temperature at the interface between the raw material melt and the grown crystal is the optimum temperature for growing the single crystal (3 in FIG. 2) at the start of the growth. By adjusting to the melting point T) of the original compound semiconductor mixed crystal, the surface temperature of the raw material melt can be easily maintained at the initial temperature during the subsequent growth. Also, during the growth, since the raw material melt is kept at the same amount as at the start of the growth, a sudden thermal disturbance due to an external factor (eg, fluctuation of thermal convection of high-pressure gas in the growth furnace) occurs. Moreover, thermal disturbance can be absorbed by the large heat capacity of the entire raw material melt. Therefore, it is possible to prevent a problematic temperature change at the solid-liquid interface between the grown crystal and the melt.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

[Correction content]

Using the above single crystal manufacturing apparatus, (InG
a) A method of growing an As mixed crystal is described below. As an example, an example of a ternary compound semiconductor mixed crystal having a mixed crystal composition of (In _0.1 Ga _0.9 ) As will be described. In the pseudo-binary phase diagram for describing the equilibrium between the solid phase and the liquid phase of the mixed crystal shown in the conceptual diagram of FIG.
_Liquidus line 12 equilibrating to composition X of _0.1 Ga _0.9 ) As
The above is represented by the pseudo binary liquid phase composition Y (In
_The binary compounds InAs and GaAs are weighed so that the composition becomes _0.58 Ga _0.42 ) As. InAs and GaAs weighed in crucible 2 and liquid sealant 3 (B ₂ O ₃ )
As the starting material. The starting material is (In _0.58 G
In the quasi-binary phase diagram shown in FIG. 3, which is a ternary melt having a composition of a _0.42 ) As, the material is once heated to a temperature higher than the temperature T, which is 1130 ° C. or higher in this embodiment, to uniformly melt Use liquid 7.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction content]

As a comparative example, except for the composition of polycrystalline solute,
Same composition as the above example (In _0.58 Ga _0.42 )
A mixed crystal single crystal having a target mixed crystal composition (In _0.1 Ga _0.9 ) As was grown using an As ternary starting material, a growth apparatus, and growth conditions. In this comparative example, a polycrystal having a composition different from the target mixed crystal composition (In _0.1 Ga _0.9 ) As, for example, a mixed crystal composition (In _0.05 G
a _0.95 ) As ternary mixed crystal or GaAs is used as a polycrystalline solute. According to the conventional method, the Ga composition of the raw material melt 7 is estimated from the weight of the grown crystal to obtain the raw material melt 7
Attempts were made to control the amount of dissolution of the polycrystalline solute so as to compensate for the decrease in Ga composition. However, the target mixed crystal composition (In _0.1 G
a _0.9 ) As and polycrystal or GaAs
In any of the examples using as a polycrystal solute, the composition change in the growth direction of the grown crystal is large due to the dispersion of the control of the dissolution amount of the polycrystal solute, and the dispersion as the Ga composition is about ± 0.07. Had reached. Further, as the crystal growth progresses, dislocations are generated due to a change in the composition of the grown crystal, or polycrystals are generated when the dislocation density is high. Further, the amount of polycrystalline solute dissolved was insufficient, the composition of the raw material melt 7 was not saturated at the growth temperature, and separation of the crystal and the melt (melt breakage) often occurred. When the above polycrystal is generated, the composition change in the growth direction of the grown crystal is particularly remarkable immediately before the occurrence of the polycrystal, and the cause of the abnormal occurrence of crystal defects due to the lattice mismatch accompanying the change in the composition of the grown crystal is This is probably because the composition of the raw material melt changed significantly.

Claims (1)

[Claims] 1. When growing a single crystal having a predetermined target mixed crystal ratio X of a ternary compound semiconductor mixed crystal by a liquid-encapsulated Czochralski method, a solid phase of the ternary compound semiconductor mixed crystal is used.
In a quasi-binary phase diagram that describes the equilibrium between liquid phases, the temperature on the solidus line where the quasi-binary composition is the target mixed crystal ratio X is defined as temperature T, and on the liquidus line at the temperature T And the ternary melt of composition Y is the raw material melt, and the temperature at the interface between the raw material melt and the liquid sealant during growth is the above temperature T. A polycrystal of a ternary compound semiconductor mixed crystal equal to the target mixed crystal ratio X is used as a solute, and the polycrystal solute having a weight equal to the weight increase amount of the growing single crystal is dissolved in the raw material melt. And a method for producing a single crystal.