JP2004010467A - Method for growing compound semiconductor single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for growing a compound semiconductor single crystal by regulating a solid-liquid boundary shape in such a manner that the compound semiconductor single crystal can be obtained with good reproducibility by an LEC (Liquid Encapsulated Czochralski) method. <P>SOLUTION: The compound semiconductor single crystal is grown by maintaining the degree A/B of the size A of the convexity of the solid-liquid boundary 5 to the thickness B of the melt 3 at the axial section in a growth direction in such a manner that the degree ranges from ≥0.2 to <0.9, more preferably ranges from ≥0.2 to ≤0.8 in the growth of a fixed diameter section 1b excluding the increased diameter section in the initial period of the growth and the decreased diameter section in the end period of the growth. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for growing a compound semiconductor single crystal.
[0002]
[Prior art]
III-V compound semiconductors have come to be widely used in high-speed integrated circuits, opto-electronic integrated circuits and other electronic devices due to the high quality of single crystals. In particular, gallium arsenide (GaAs) has a feature that electron mobility is faster than that of silicon and that a wafer having a specific resistance of 10 ⁷ Ω · cm or more can be easily manufactured. At present, the GaAs single crystal is mainly manufactured by a liquid sealing and pulling method (LEC method: Liquid Encapsulated Czochralski method).
[0003]
FIG. 2 schematically shows a crystal pulling apparatus using the LEC method, which is widely used as a GaAs single crystal manufacturing apparatus.
[0004]
In the drawing, reference numeral 21 denotes a pressure vessel of a high temperature furnace for crystal growth. A lower shaft 22 is inserted into the pressure vessel 21 from below, and a susceptor 24 is supported at a tip of the lower shaft 22 via a pedestal 23. I have. The PBN crucible 2 is arranged in the susceptor 24. The heater 6 is provided around the susceptor 24, so that the PBN crucible 2 can be heated from the surroundings through the susceptor 24. The lower shaft 22 is connected to a rotation mechanism (not shown), and is rotated at a constant rotation speed. An upper shaft 29 is inserted coaxially with the lower shaft 22 from above the pressure vessel 21, and a seed crystal 31 having a desired orientation is attached to a seed crystal holder 30 provided at a lower end thereof. The upper shaft 29 is rotated by a rotating / elevating mechanism (not shown) in a direction opposite to that of the PBN crucible 2 and is moved up and down. A weight sensor 32 is provided in the middle of the upper shaft 29 so that the weight of the crystal during the growth process can be detected.
[0005]
At the time of crystal growth, first, 14,000 g of the GaAs polycrystalline raw material 26 and 4,000 g of the B ₂ O ₃ liquid sealant 27 are put into the crucible 2 made of PBN, and the inside of the pressure-resistant container 21 is evacuated. Thereafter, the pressure is increased to about 40 atm with an inert gas such as nitrogen or argon, and the main heater 6 is energized to raise the temperature inside the PBN crucible 2. At around 500 ° C., the liquid sealant (B ₂ O ₃ ) 27 softens and melts, and covers the GaAs polycrystalline raw material 26. Subsequently, the temperature is raised to make the temperature inside the PBN crucible 2 1,238 ° C. or higher, and the polycrystalline raw material 26 is melted. Next, after the pressure inside the pressure vessel 21 is reduced to 5 to 20 atm, the seed crystal 31 is lowered, and its tip is immersed in a raw material melt to perform seeding. Thereafter, while lowering the temperature of the heater 6, the upper shaft 29 is pulled up at a speed of 9 to 12 mm / hr, and while detecting the crystal weight by the weight sensor 32, the output of the heater 6 is controlled to grow a GaAs single crystal. Let it.
[0006]
[Problems to be solved by the invention]
However, the technique for growing a compound semiconductor single crystal is extremely difficult, and the technique is more minutely affected by the arrangement, shape, material, and the like of a heater as a heating means and a member such as a heat shield tube (called a hot zone; hereinafter, referred to as HZ). Therefore, it is difficult to obtain growth conditions for a compound semiconductor single crystal with good reproducibility.
[0007]
Factors for obtaining the growth conditions of the compound semiconductor single crystal with good reproducibility have been considered to be related to the HZ, such as the arrangement, shape and material of the HZ. However, with the stabilization of the conditions such as the arrangement, shape, and material of HZ, the factor is not limited to HZ alone, but how the solid-liquid interface shape is fundamentally controlled depends on the single crystal. It has become clear that this is a major factor in gaining.
[0008]
In the LEC method, control of the shape of the solid-liquid interface is an important factor in obtaining a single crystal. However, there is no document that discloses a technique for defining the solid-liquid interface shape so far.
[0009]
Accordingly, an object of the present invention is to solve the above-mentioned problems, to solve the problems of the above-described technology in the LEC method, and to define a solid-liquid interface shape so that a compound semiconductor single crystal can be obtained with good reproducibility. An object of the present invention is to provide a method for growing a single crystal.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is configured as follows.
[0011]
According to the first aspect of the present invention, a raw material melt and a liquid sealant are stored in a heated crucible housed in a pressure-resistant container filled with an inert gas, and the seed crystal is brought into contact with the raw material melt while being brought into contact with the raw material melt. In a method for producing a compound semiconductor single crystal by the LEC method in which a single crystal is grown by relatively moving a crucible, the compound semiconductor is maintained such that the solid-liquid interface shape is always convex toward the melt during the entire growth process. It is characterized by growing a single crystal.
[0012]
According to a second aspect of the present invention, in the growth method according to the first aspect, the degree A / B of the size A of the protrusion A of the solid-liquid interface with respect to the thickness B of the melt in the axial section (longitudinal section) in the growth direction is determined. In the constant diameter portion excluding the initial diameter-increased portion and the diameter-reduced portion at the end of growth, it is maintained in the range of 0.2 or more and less than 0.9, preferably 0.2 or more and 0.8 or less. And growing a compound semiconductor single crystal.
[0013]
According to a third aspect of the present invention, in the growth method according to the first aspect, the degree A / B of the size A of the protrusion A of the solid-liquid interface with respect to the thickness B of the melt in the axial cross section in the growth direction is the diameter increase in the initial stage of growth. In the constant-diameter portion excluding the part and the diameter-reduced part at the end of growth, the arrangement of the hot zone is 0.2 or more and less than 0.9, preferably 0.2 or more and 0.8 or less. The method is characterized in that the compound semiconductor single crystal is grown by adjusting the shape, the material, and the like.
[0014]
According to a fourth aspect of the present invention, in the growth method according to any one of the first to third aspects, a large-diameter crystal having a diameter of 100 mm or more is grown.
[0015]
<The gist of the invention>
When the solid-liquid interface is concave toward the melt, lineage and subgrain boundaries are likely to accumulate, regardless of the overall growth process or a certain period of growth, and the reproducibility of obtaining a single crystal is low. Will also be lower.
[0016]
The present invention has made it possible to obtain a compound semiconductor single crystal with good reproducibility and high yield by making the solid-liquid interface shape always convex toward the melt over the entire growth process in the LEC method. It is.
[0017]
In addition, the present inventors have made intensive research efforts on the degree of protrusion of the solid-liquid interface toward the melt, and have derived the following relationship.
[0018]
That is, in the constant diameter portion excluding the diameter-increased portion at the beginning of growth and the diameter-reduced portion at the end of growth, the degree of protrusion of the solid-liquid interface toward the melt, that is, the solidity relative to the melt thickness B of the axial section in the growth direction. When the degree A / B of the size A of the convexity of the liquid interface is less than 0.2, the solid-liquid interface is likely to be concave toward the melt side due to a minute fluctuation of the growth environment such as a temperature fluctuation, and the lineage and the sub-grain The world is easy to spawn and is not good.
[0019]
In the constant diameter portion excluding the diameter-increased portion at the beginning of growth and the diameter-reduced portion at the end of growth, the degree of protrusion of the solid-liquid interface toward the melt, that is, the solidity relative to the melt thickness B of the axial section in the growth direction. When the degree A / B of the size A of the convexity of the liquid interface exceeds 0.8, the degree of convexity of the solid-liquid interface toward the melt becomes large due to minute fluctuations in the growth environment such as temperature fluctuations. It is easy to cause the crystal after solidification to come into contact with the crucible containing the melt, which makes crystal growth difficult. This tendency becomes particularly remarkable when the degree A / B of the protrusion of the solid-liquid interface toward the melt exceeds 0.9.
[0020]
Therefore, in the constant diameter portion excluding the diameter-increased portion at the beginning of growth and the diameter-reduced portion at the end of growth, the degree A / B of convexity of the solid-liquid interface toward the melt is in the range of 0.2 or more and less than 0.9, Preferably, the solid-liquid interface shape is defined so as to be in the range of 0.2 to 0.8, and if this is maintained by changing the arrangement, shape, material, etc. of the hot zone, the Can grow a compound semiconductor single crystal having a large diameter of 100 mm or more with good reproducibility.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described based on the illustrated embodiments.
[0022]
FIG. 1 shows a growth process of a compound semiconductor single crystal by the LEC method in an axial section (longitudinal section) in the growth direction. The basic structure of the growth apparatus is the same as that in FIG.
[0023]
As shown in FIG. 1, a compound semiconductor melt 3 and a liquid sealant 4 are housed in a crucible 2 housed in a pressure-resistant container 21 (see FIG. 2) filled with an inert gas and heated by a heater 6. Then, the compound semiconductor single crystal 1 is grown.
[0024]
Here, a boundary between the compound semiconductor melt 3 and the compound semiconductor single crystal 1 becomes a solid-liquid interface 5. The degree of protrusion of the solid-liquid interface 5 toward the melt is indicated by the ratio A / B of the thickness B of the melt 3 in the axial section in the growth direction and the size A of the protrusion of the solid-liquid interface 5. The degree A / B of the convexity of the solid-liquid interface toward the melt is determined by the ratio A / B in the growth of the constant diameter portion 1b excluding the diameter increasing portion 1a at the initial stage of growth of the compound semiconductor single crystal 1 and the diameter decreasing portion at the end of growth. The solid-liquid interface shape is defined so that the value is in the range of 0.2 or more and less than 0.9, preferably in the range of 0.2 to 0.8. Then, the solid-liquid interface shape is maintained during the growth of the constant diameter portion 1b, and the compound semiconductor single crystal 1 is grown. The degree A / B of the convexity of the solid-liquid interface 5 toward the melt is adjusted by changing the arrangement, shape, and the like of the hot zone HZ, which is a member such as a heat shield cylinder.
[0025]
Thus, the compound semiconductor single crystal 1 having a large diameter of 100 mm or more can be grown with high reproducibility and high yield.
[0026]
<Example>
In order to confirm the effects of the present invention, as an example, a single crystal of gallium arsenide, which is a kind of compound semiconductor, was grown.
[0027]
That is, in the single crystal growth of gallium arsenide (GaAs) having a crystal diameter of 100 mm and a crystal length of 400 mm, the degree A / B of the convexity of the solid-liquid interface 5 toward the melt (the thickness of the melt in the axial section in the growth direction) B) is in the range of 0.2 or more and less than 0.9 in the growth of the constant diameter portion 1b excluding the diameter-increased portion at the beginning of growth and the diameter-reduced portion at the end of growth. The single crystal growth was performed 50 times by adjusting the arrangement and shape of HZ such that As a result, a single crystal (All Single) was obtained with a probability of 95% or more from the seeding of the crystal to the final part of the crystal growth.
[0028]
<Comparative Example 1>
In the same manner as in the embodiment, in the single crystal growth of gallium arsenide having a crystal diameter of 100 mm and a crystal length of 400 mm, the degree of protrusion of the solid-liquid interface toward the melt, that is, the solidity relative to the melt thickness B of the axial section in the growth direction. The degree A / B of the convexity A of the liquid interface is less than 0.2 in the constant diameter portion 1b excluding the diameter increasing portion at the beginning of growth and the diameter decreasing portion at the end of growth (in this case, the solid-liquid interface). The single crystal growth was performed 50 times by adjusting the arrangement and shape of HZ so that 5 was concave toward the melt side. As a result, from the seeding of the crystal to the final part of the crystal growth, there was a 50% probability of a single crystal (All Single) in the entire region.
[0029]
<Comparative Example 2>
Similarly, the degree A / B of the protrusion of the solid-liquid interface toward the melt, that is, the degree A / B of the protrusion A of the solid-liquid interface with respect to the thickness B of the melt in the axial section in the growth direction, is increased. The single crystal growth was performed 50 times by adjusting the arrangement and shape of the HZ so that the value exceeded 0.8 in the diameter portion and the constant diameter portion 1b excluding the diameter reduction portion at the end of growth. As a result, the solidified crystal was brought into contact with the crucible, and crystal growth was difficult 10 times. The probability of a single crystal (All Single) in the entire region from seeding of the crystal to the final part of the crystal growth was 60%.
[0030]
As can be seen comprehensively from the above results, the solid-liquid interface shape is always convex on the melt side in the entire growth process, and the degree of convexity of the solid-liquid interface on the melt side, that is, the growth direction. The degree A / B of the size A of the protrusion A of the solid-liquid interface with respect to the thickness B of the melt in the axial section is 0.2 in the constant diameter portion 1b excluding the diameter increasing portion at the beginning of growth and the diameter decreasing portion at the end of growth. As described above, by controlling so as to fall within the range of 0.8 or less, a compound semiconductor single crystal can be obtained with higher reproducibility and higher yield. Further, even if the degree A / B of the protrusion of the solid-liquid interface toward the melt is controlled to be in the range of 0.2 or more and less than 0.9, the degree A / B is not less than 0.8 and less than 0.9. Although the effect is reduced in the range, the compound semiconductor single crystal can be obtained with good reproducibility and high yield.
[0031]
In the above embodiment, a method for growing a gallium arsenide (GaAs) single crystal has been described. However, the present invention is also applicable to a method for growing a compound semiconductor single crystal such as InP, GaP, InAs or the like, which performs crystal growth by an LEC method. Thus, similarly, a compound semiconductor single crystal can be obtained with good reproducibility and high yield.
[0032]
The compound semiconductor single crystal obtained by the method according to the present invention not only has a higher probability of obtaining an entire single crystal (All Single) than the conventional method in which the shape of the solid-liquid interface is not defined, but also obtains the compound semiconductor single crystal by the conventional method. There is a tendency that the number of dislocation accumulation portions is smaller than that of the obtained compound semiconductor single crystal. This indicates that in the case of the conventional method, even in the case of an all single crystal (All Single), dislocations accumulate even if they do not develop into lineage and sub-grain boundaries.
[0033]
When a compound semiconductor wafer obtained by the present invention is used to form an element, it is possible to prevent a decrease in element yield due to dislocation, and there is a great economic effect in industrial production.
[0034]
【The invention's effect】
As described above, according to the present invention, the compound semiconductor single crystal is grown while maintaining the shape of the solid-liquid interface always convex on the melt side during the entire growth process. A compound semiconductor single crystal can be obtained at a high rate.
[0035]
Further, the degree A / B of the convexity of the solid-liquid interface to the melt side, that is, the degree A / B of the convexity A of the solid-liquid interface with respect to the thickness B of the melt in the axial section in the growth direction is determined by the diameter increase in the initial stage of growth. Part and the constant diameter part excluding the reduced diameter part at the end of growth are maintained in the range of 0.2 or more and less than 0.9, preferably in the range of 0.2 or more and 0.8 or less. A compound semiconductor single crystal can be obtained with good yield and high yield.
[Brief description of the drawings]
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view for explaining a method of growing a compound semiconductor single crystal of the present invention, and is an axial cross-section (longitudinal cross-section) in a growth direction showing a crystal, a crucible, a melt, and a liquid sealant in a crystal growth process. is there.
FIG. 2 is a view showing a basic configuration of a conventional compound semiconductor single crystal manufacturing apparatus.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 compound semiconductor single crystal 1 a diameter increasing part 1 b constant diameter part 2 crucible 3 compound semiconductor melt 4 liquid sealant 5 solid-liquid interface 6 heater A convex size of solid-liquid interface B melt thickness

Claims (4)

The raw material melt and liquid sealant are stored in a heated crucible that is housed in a pressure-resistant container filled with an inert gas, and the seed crystal and the crucible are relatively moved while the seed crystal is in contact with the raw material melt. In the method for producing a compound semiconductor single crystal by the LEC method of growing a single crystal by
A method for growing a compound semiconductor single crystal, comprising growing a compound semiconductor single crystal while maintaining the shape of the solid-liquid interface always convex toward the melt during the entire growth process. The growth method according to claim 1,
The degree A / B of the size A of the protrusion A of the solid-liquid interface with respect to the thickness B of the melt in the axial section in the growth direction is set to 0 in the constant diameter portion excluding the diameter increasing portion at the beginning of growth and the diameter decreasing portion at the end of growth. A method for growing a compound semiconductor single crystal, wherein the compound semiconductor single crystal is grown while being maintained in a range of 2 or more and less than 0.9, preferably 0.2 or more and 0.8 or less. . The growth method according to claim 1,
The degree A / B of the size A of the protrusion A of the solid-liquid interface with respect to the thickness B of the melt in the axial cross section in the growth direction is 0 in the constant diameter portion excluding the diameter increasing portion at the beginning of growth and the diameter decreasing portion at the end of growth. The compound semiconductor single crystal is adjusted by changing the arrangement, shape, material and the like of the hot zone so as to be in the range of 2 or more and less than 0.9, preferably in the range of 0.2 or more and 0.8 or less. And growing the compound semiconductor single crystal. The growth method according to any one of claims 1 to 3,
A method for growing a compound semiconductor single crystal, comprising growing a large-diameter crystal having a diameter of 100 mm or more.

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