JPH06345581A - Production of multielement compound mixed single crystal - Google Patents

Abstract

PURPOSE:To grow and produce a multielement compd. mixed single crystal of uniform composition by VGF with a high reproducibility. CONSTITUTION:A multielement material is placed in a crucible 2, heated by heaters 3a, 3b and 3c and melted, a solute material 5 is supplied from the upper surface of the molten material 8, the outputs of the heaters 3a, 3b and 3c are adjusted so that the the temp. of the molten material 8 is gradually lowered toward the lower part from the upper part, and hence the molten material 8 is gradually solidified toward the upper part from the lower part to grow a multielement compd. mixed single crystal 9. The weight decrease of the solute material 5 per unit time is detected, the outputs of the heaters 3a, 3b and 3c are controlled in accordance with the decrease, and the growth rate of the crystal 9 is adjusted. Consequently, the crystal is grown from the molten matrial of constant composition, and a uniform mixed single crystal of desired composition is produced with a high reproducibility.

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 multi-component compound mixed crystal single crystal composed of at least three kinds of constituent elements, and in particular, a substance having a chemical composition obtained by mixing at least two kinds of compounds, For example, (In, Ga) S
b, (In, Ga) P, (In, Ga) As or I
A ternary compound semiconductor which is a solid solution of a binary compound semiconductor such as n (As, P), or Li ₂ O. (B ₂ O ₃ ) ₃ , Li
A mixed crystal single crystal such as an ionic crystal having a chemical composition in which at least two kinds of anhydrous oxides are mixed in different ratios such as ₂ O · (B ₂ O ₃ ) ₄ is dissolved in a raw material melt. Vertical temperature gradient solidification method (hereinafter referred to as "VGF method") while supplying raw materials
Is abbreviated. ).

[0002]

2. Description of the Related Art A multi-component compound mixed crystal is composed of at least three kinds of elements, for example, (In, Ga) Sb, (I
n, Ga) P, (In, Ga) As or In (A
s, P), a ternary compound semiconductor that is a solid solution of a binary compound semiconductor, such as Li ₂ O. (B ₂ O ₃ ) ₃ or Li ₂ O.
A chemical composition obtained by mixing at least two kinds of compounds such as an ionic crystal having a chemical composition in which at least two kinds of anhydrous oxides are mixed in different ratios such as (B ₂ O ₃ ) _{4 and} the like. Is a crystal of a substance that has a difference in properties, such as a band gap and other properties (physical properties), and a lattice constant, by changing the mixed crystal composition (chemical composition) of the compound, unlike binary compounds composed of only two types of constituent elements. Since it is possible to change the biological structure, the usefulness of a substrate for epitaxial growth has attracted attention. As a method for producing such a multi-component compound mixed crystal, a seed crystal is brought into contact with the upper surface of a raw material melt obtained by melting a raw material having a predetermined chemical composition and a liquid sealant in a crucible, and the seed crystal is rotated. A liquid-encapsulated Czochralski method (hereinafter abbreviated as “LEC method”) is known in which a single crystal is grown by gradually pulling it up.

Conventionally, when a single crystal of a multi-component compound mixed crystal is grown by this LEC method, a constituent element (component) having a large segregation coefficient in the raw material melt, that is, a segregation-prone element is preferentially grown. It was difficult to obtain a crystal having a uniform composition, particularly a composition having a uniform composition in the growth direction of the crystal, because the concentration of the constituent elements in the raw material melt gradually decreased as it was taken into the crystal. In order to solve this, by supplying the component having a large segregation coefficient to the raw material melt during crystal growth,
A method for suppressing the change of components in the raw material melt has been proposed (Japanese Patent Laid-Open No. 62-3097), but in this method, a solute raw material which is a supply source of a component having a large segregation coefficient, and which is at least the constituent element Since the lower surface of the crucible is filled, it is difficult to control the dissolution rate of the solute raw material in the raw material melt,
It was difficult to grow a mixed crystal single crystal having a stable and uniform target composition.

Therefore, the applicant has adjusted the output of the heater to provide a temperature gradient in the crystal growth direction in the raw material melt, and in the VGF method of growing crystals from the bottom to the upper surface of the crucible, the raw material melt A method was previously proposed in which the solute raw material was immersed in the upper part of the solution to dissolve and supply the insufficient component (Japanese Patent Application No. 5-46081). According to this method, since the solute raw material is melted from the upper surface of the raw material melt, the above-mentioned LEC
It is relatively easy to control the supply amount of the solute raw material as compared with the method, and the position of the crystal growth interface (that is, the solid-liquid interface between the grown crystal and the raw material melt) and the solute raw material supply position Therefore, the influence of the supply of the solute material on the growth interface can be reduced, and a mixed crystal single crystal having a uniform composition can be stably grown.

[0005]

However, in the invention proposed in Japanese Patent Application No. 5-46081 mentioned above by our research thereafter, the interface (solid-liquid interface) between the raw material melt and the solute raw material is If the temperature, that is, the temperature of the upper surface of the raw material melt is lower than the allowable range, the solute raw material immersed in the upper part of the raw material melt at a predetermined speed is not melted and is pushed into the raw material melt as it is, and the raw material melt It was found that there was a possibility that the lacking component in the inside could not be compensated and that a mixed crystal single crystal having a uniform target composition could not be produced with good reproducibility.

The present invention has been made in order to solve the above problems, and makes it possible to grow reproducibly a uniform multi-component compound mixed crystal single crystal having a target mixed crystal composition by the VGF method. An object of the present invention is to provide a method for producing a multi-component compound mixed crystal single crystal.

[0007]

The present invention comprises at least 3
In the multi-component compound mixed crystal single crystal consisting of the elements of the melt, in the melt growth using a raw material melt having a predetermined chemical composition consisting of the at least three elements constituting the multi-component compound mixed crystal, While supplying a solute raw material made of at least one element of the elements forming the multi-component compound mixed crystal from the upper surface of the raw material melt held in the crucible, the raw material melt gradually increases from the upper portion to the lower portion. The output of the heater is controlled so that the temperature is low, and the raw material melt is gradually solidified from the lower part to the upper part to perform single crystal growth of the multi-component compound mixed crystal, and the single crystal is grown during the growth of the single crystal. It is proposed to detect the weight reduction amount of the solute raw material per unit time and control the output of the heater according to the weight reduction amount to adjust the growth rate of the single crystal.

Specifically, for example, like a device shown in FIG. 1 as an example, a crucible 2 can be installed in a high-pressure vessel 1, and heaters 3a, 3 are provided so as to surround the crucible 2.
b, 3c are provided, and the heaters 3a, 3b,
3c is a lot in which a solute raw material 5 is rotatably and vertically movable around its central axis as a rotation axis in a vertical temperature gradient solidification apparatus having the same structure as that of the conventional one, whose outputs can be controlled by a control device 4. A shaft 6 is provided, a weight sensor 7 is attached to the upper part of the lot shaft 6, and the sensor 7 and the lot shaft 6 are connected to the control device 4. The crucible 2 is supported by a crucible lot shaft 11 via a susceptor 10 and is rotatable about its central axis as a rotation axis. Further, a plurality of temperature sensors 15 connected to the control device 4 include a crucible 2 and a heater 3.
It is provided between a, 3b and 3c, and this sensor 1
Each output of the heaters 3a, 3b, 3c is controlled based on the information from 5 (only one is illustrated in FIG. 1). Further, the seed crystal 20 is housed in the bottom of the crucible 2.
Further, in order to obtain a raw material melt having a predetermined chemical composition, the crucible 2 has a predetermined content of at least two compounds among compounds composed of at least two elements of the multi-component compound mixed crystal. The mixture (hereinafter referred to as "multi-component mixture raw material") is stored in the ratio. Alternatively, a solid solution obtained by previously melting and solidifying a mixture of the above-mentioned at least two compounds in a predetermined ratio (raw material for multi-component system) in the crucible 2 may be used.

Then, the weight sensor 7 detects the weight reduction amount of the solute raw material 5 per unit time, and the controller 4 compares the weight reduction amount with a predetermined target reduction amount, and the detected weight reduction amount is predetermined. When the amount of the solute raw material 5 is larger than the target decrease amount, the growth rate of the mixed crystal single crystal 9 is faster than the dissolution rate of the solute raw material 5, the solute raw material 5 cannot be completely dissolved, and the raw material melt 8
Judge that it is immersed in. That is, when the detected weight reduction amount is larger than the predetermined target reduction amount, the solute raw material 5 is pushed into the raw material melt 8 without being melted, and the weight of the solute raw material 5 is increased by the buoyancy acting on the solute raw material 5. Is apparently too small.

As described above, when it is determined that the solute raw material 5 is not completely dissolved, the outputs of the heaters 3a, 3b and 3c are controlled so that the crystal growth rate becomes small. That is, to slow down the temperature of the entire raw material melt 8,
The temperature gradient near the solid-liquid interface between the raw material melt 8 and the already grown mixed crystal single crystal 9 is reduced. Here, the predetermined target reduction amount of the weight of the solute raw material 5 is supplied in order to supplement the deficient component in the raw material melt 8 when the crystal having the target composition is grown at the set crystal growth rate. The weight of the solute raw material 5 to be obtained is calculated and calculated based on the weight. That is, it corresponds to the weight to be supplied per unit time. It goes without saying that the lot shaft 6 may be connected to the control device 4 and the lowering speed of the lot shaft 6, that is, the lowering speed of the solute material 5 may be controlled by the control device 4.

[0011]

According to the above means, the weight change of the solute raw material, that is,
Detecting the amount of weight reduction per unit time and comparing the amount of weight reduction with the predetermined target amount of reduction determined in advance based on the crystal growth rate, confirms that the solute raw material is properly dissolved and supplied to the raw material melt. You can guess whether or not. Then, when it is determined that the solute raw material is not melted and is pushed into the raw material melt, the solute raw material in the raw material melt is controlled by controlling the output of the heater so as to reduce the crystal growth rate. The crystal growth is suppressed until the undissolved portion of is melted and the insufficient component in the raw material melt is compensated. Therefore, since the crystal is always melt-grown from the raw material melt having a constant composition,
A mixed crystal single crystal having a uniform target composition can be obtained with good reproducibility.

[0012]

EXAMPLES Hereinafter, the method for producing a multi-component compound mixed crystal single crystal according to the present invention will be described in detail with reference to Examples and Comparative Examples. In the examples and comparative examples, as an example, the production of a ternary compound semiconductor single crystal of (In _0.35 Ga _0.65 ) P was carried out by using the apparatus shown in FIG. 1 in order to prevent volatilization of the raw material melt 8. The atmosphere gas pressure was applied.

Here, the chemical composition of the multi-component mixture raw material placed in the crucible 2 is shown in FIG. 2 (In,
In the pseudo-binary phase diagram of Ga) P, the composition on the solid line S at temperature T (In _0.35 Ga _0.65 ) P and the composition on the liquidus line L equilibrating (In _0.90 Ga _0.10 ) P Yes, it was prepared by mixing a predetermined amount of binary compound semiconductors InP and GaP synthesized in advance. Then, the raw material of the multi-component mixture was put into the crucible 2 together with the liquid sealant 12 to make a starting raw material. This starting material was heated by the heaters 3a, 3b, 3c and melted at a predetermined temperature T _O slightly higher than the temperature T to obtain a melt having a uniform predetermined chemical composition, that is, a raw material melt 8. At this time, the temperature of the interface between the seed crystal 20 and the raw material melt 8 was set to be slightly higher than the temperature T.

As the solute raw material 5, the segregation coefficient of Ga is the largest among the three elements In, Ga and P constituting the raw material melt 8 described above.
In order to supplement the above, a GaP polycrystal, which is a compound made of Ga and formed into a quadrangular prism having a square cross section with a side of 2.2 cm, was used. When melting the above-mentioned starting material, the solute material 5
Was placed in a place where it was difficult to be heated by the heaters 3a, 3b, 3c. Further, the seed crystal 20 has a growth orientation of (1
The GaP single crystal of (00) (diameter 4 mm) was used. And
The rotation speed of the crucible 2 was 0 rpm, and the crystal growth rate was initially set to 1 mm per hour.

Here, the rate of lowering the solute material 5 was determined as follows. That is, the target composition (In
_When the crystal growth rate of _0.35 Ga _0.65 ) P is the above-mentioned crystal growth rate (1 mm / hour), the crystal is formed from the raw material melt 8 in consideration of the growth rate value and the shape (that is, the diameter) of the crucible 2. Calculate the change over time in the amount lost due to growth,
Based on the calculated values shown in FIG. 3, the change over time in the amount of GaP deficient in the raw material melt 8 (in other words, the amount of GaP to be supplied in the raw material melt 8) was calculated. The calculated value is shown as a calculated value (target value) in FIG. 7. Further, the descending speed of the solute raw material 5 was calculated based on the calculated value (target value) shown in FIG. 7 in consideration of the cross-sectional area of the solute raw material 5. FIG. 4 is a graph of the calculated values. Therefore, the solute raw material 5 was lowered by controlling the controller 4 so as to satisfy the curve in FIG.

Under the above conditions, the heaters 3a,
By controlling the outputs of 3b and 3c, the temperature of the interface between the seed crystal 20 and the raw material melt 8 is gradually lowered to the above temperature T, and a predetermined temperature gradient is further applied upward from the bottom of the crucible 2. The mixed crystal single crystal 9 was grown by gradually lowering the temperature while being provided. Specifically, the seed crystal 20 having a diameter of 4 mm arranged at the bottom of the crucible 2 is used to start the crystal growth, and the height is about 28 mm.
When the crystal length including the substantially conical shoulder part of mm and the straight body part following it reaches about 80 mm, the solute raw material 5 supplied by the raw material melt 8 is exhausted, the growth is completed, and the diameter is about 2 inches. Length 50
A mixed crystal single crystal having a straight body part of mm was obtained. At the start of crystal growth, the temperature of the interface between the seed crystal 20 and the raw material melt 8 (growth start store 16) is set to the temperature T, and the solid-liquid interface (that is, The temperature of the upper surface 18 of the raw material melt 8 is set as the temperature when the starting raw material is melted (a predetermined temperature T ₀ slightly higher than the temperature T), and the temperature gradually decreases from the upper part of the raw material melt 8 to the lower part. I did it. Then, at the time of crystal growth, the upper surface 1 of the raw material melt 8
While maintaining the temperature of No. 8 at a predetermined temperature T ₀ slightly higher than the temperature T, the temperature of the growth starting point 16 is gradually lowered from the temperature T to grow a solid-liquid mixture of the mixed crystal single crystal 9 and the raw material melt 8. The interface 17 was brought to the temperature T and the crystal growth was advanced from the lower part of the raw material melt 8 to the upper part. At this time, as the crystal growth progresses, the total amount of the raw material melt 8 decreases, and the distance from the solid-liquid interface 17 between the mixed crystal single crystal 9 and the raw material melt 8 to the upper surface 18 of the raw material melt 8 decreases. Become. As a result, the temperature gradient formed in the raw material melt 8 gradually increases as the crystal growth progresses.

(Example) Solute raw material 5 by weight sensor 7
The crystals were grown while detecting the amount of weight loss of. At this time, as described above, when the crystal growth rate was initially set to 1 mm / hour and the solute raw material 5 was lowered to start crystal growth based on FIG. 4, the weight reduction amount detected by the weight sensor 7 was originally A predetermined target reduction amount (target in FIG. 7) when the solute raw material 5 is properly supplied at the crystal growth rate of 1 mm / hour (that is, when the solute raw material 5 is dissolved in the raw material melt 8 without excess or deficiency) (Shown as a value), the control device 4 adjusted the crystal growth rate from the start to the end of the crystal growth. As a result, the crystal growth rate is one of the above initially set crystal growth rates.
It was adjusted to be slower than mm / hour, and the average is 0.
It became 5 mm / hour. Specifically, the above heaters 3a, 3
By controlling the outputs of b and 3c, the speed of lowering the temperature at the position where the interface between the seed crystal 20 and the raw material melt 8 was formed at the start of crystal growth (growth start point 16) was slowed, The average crystal growth rate was 0.5 mm / hour. When the rate of lowering the temperature of the growth start point 16 becomes slow, the raw material melt 8
The increasing rate of the temperature gradient formed therein becomes slower, and as a result, the rate at which the temperature becomes T moves upward, that is, the rate at which the solid-liquid interface 17 between the mixed crystal single crystal 9 and the raw material melt 8 moves. Was adjusted to 0.5 mm / hour above. Further, the descending speed of the solute raw material 5 is also 0.5% when the adjusted crystal growth speed is 0.5.
With the increase in mm / hour, the growth rate of the crystal was adjusted to an appropriate speed.

FIG. 5 shows a time-dependent change curve of the weight reduction amount (measured value) of the solute raw material 5 in this example. In addition, FIG. 5 also shows an ideal curve (target value) of the weight reduction amount calculated by setting the crystal growth rate to 0.5 mm / hour. From the figure, the two curves are substantially coincident with each other, and the control of the crystal growth rate according to the present invention effectively works, and the crystal growth rate is 0.5 mm.
It can be seen that the solute raw material 5 is dissolved in the raw material melt 8 in an optimum state when adjusted to / hour. It should be noted that the curve of the actual measurement value is located slightly above the ideal curve (target value) based on the calculated value, because the surface tension on the upper surface of the raw material melt 8 causes a slight downward force on the solute raw material 5. It is presumed that it is working.

Further, the composition distribution in the growing direction of the obtained mixed crystal single crystal is determined by EPMA (electron probe microanalysis).
It was evaluated by the method. The result is shown in FIG. In FIG. 6, the horizontal axis indicates the relative position in the growth direction starting from the growth start point 16 of the crystal. Based on the crystal length measured from the growth start point 16, the crystal weight up to that position is calculated, It is shown by using the ratio to the initial weight of the raw material melt 8 (for convenience, referred to as "solidification rate"). That is, the point where the fixed rate is 0 is
It is the position of the growth start point 16, and the direction in which the solidification rate increases indicates the direction in which the growth progresses. In the case of this example and the following comparative examples, the point where the solidification rate is 0.6 shown in FIG. 6 is the position where the crystal growth was completed, and the crystal length measured from the growth starting point 16 was about 80 mm. Corresponds to position. The portion where the solidification rate exceeds 0.6 corresponds to the portion where the raw material melt 8 left after the crystal growth is solidified during cooling. Further, the portion where the solidification rate is about 0.1 or less is the above-mentioned height of about 2 or less.
A shoulder portion having a substantially conical shape of 8 mm, and a portion where the solidification rate exceeds 0.1 is the straight body portion. From the figure, in the crystal obtained in this example, a mixed crystal (In _1- x, Ga) in the growth direction was obtained.
x) The Ga composition x in P is in the range of 0.65 ± 0.03, which is substantially the same as the target composition of 0.65, and the variation is small. Therefore, it is understood that the solute raw material 5 is appropriately dissolved in the raw material melt 8 during the crystal growth, Ga that is insufficient in the raw material melt 8 is sufficiently compensated, and the composition fluctuation of the raw material melt is suppressed.

(Comparative Example) The solute raw material 5 is measured by the weight sensor 7.
Was performed only for the detection of the weight reduction amount of No. 3, and the crystal was grown without performing the crystal growth rate based on the detected weight reduction amount of the solute material 5. Specifically, the crystal growth rate was maintained at 1 mm / hour, which is the initially set crystal growth rate, and the solute material 5 was lowered based on FIG. That is,
The crystal growth rate was not changed and kept constant at 1 mm / hour during the growth, and the descending speed of the solute raw material 5 was controlled by the controller 4 to match the descending speed shown in FIG. The other conditions were the same as in the above-mentioned example.

FIG. 7 shows a time-dependent change curve of the weight reduction amount (measured value) of the solute raw material 5 in the comparative example. The ideal curve (target value) of the weight reduction amount calculated by setting the crystal growth rate to 1.0 mm / hour is also shown in FIG. From the figure, it can be seen that the curve of the actual measurement value is located below the ideal curve of the calculated value, and the solute raw material 5 is pushed into the raw material melt 8 without being dissolved. Further, as a result of evaluating the composition distribution in the growing direction of the obtained mixed crystal single crystal by the EPMA method, as shown in FIG. 6, in the crystal obtained in the comparative example, the Ga composition x is the target composition as the growing progresses. There is 0.
It turned out that it deviated gradually from 65.

In the above embodiment, (In _0.35
The case of producing a Ga _0.65 ) P ternary compound semiconductor single crystal has been described, but (In, Ga) P having different compositions is described.
It is needless to say that it can be used not only for the crystal growth of the above, but also for the crystal growth of other multi-element mixed crystals belonging to the III-V group compound semiconductor, and also belongs to the II-VI group compound semiconductor. Of course, it can also be used for crystal growth of multi-element mixed crystals. In addition to compound semiconductors, Li ₂
It can also be used for crystal growth of oxide single crystals, which are metal salts of anhydrides having various chemical compositions, such as O. (B ₂ O ₃ ) ₃ and Li ₂ O. (B ₂ O ₃ ) _4. Of course.

Furthermore, in the above embodiment, the seed crystal 20 is arranged at the bottom of the crucible 2.
Alternatively, the mixed crystal single crystal 9 may be naturally generated from the bottom of the crucible 2 without providing the above. Further, the single crystal manufacturing apparatus used for carrying out the present invention can be variously provided as long as the weight sensor 7 and the controller 4 can control the outputs of the heaters 3a, 3b, 3c. It goes without saying that the design can be changed.

[0024]

According to the method for producing a multi-component compound mixed crystal single crystal according to the present invention, the weight reduction amount of the solute raw material per unit time is detected, and the output of the heater is controlled according to the weight reduction amount. Therefore, the crystal growth can be suppressed until the undissolved portion of the solute raw material in the raw material melt is dissolved and the insufficient component in the raw material melt is compensated. Therefore, since the crystal can be melt-grown from the raw material melt having a constant composition, a mixed crystal single crystal having a uniform composition can be produced with good reproducibility.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining a manufacturing method according to the present invention.

FIG. 2 is a schematic diagram of a pseudo-binary phase diagram of (In, Ga) P.

FIG. 3 is a characteristic diagram showing a time-dependent change in the amount of decrease in the raw material melt (that is, the weight of the grown crystal) accompanying the crystal growth when the set value of the crystal growth rate is 1 mm / hour.

FIG. 4 is a characteristic diagram showing the descending speed of the solute raw material GaP obtained based on FIG.

FIG. 5 is a characteristic diagram showing a weight change amount of a solute raw material GaP in an example.

FIG. 6 E of each crystal obtained in Examples and Comparative Examples
It is a characteristic view showing the composition distribution of the crystal growth direction evaluated by the PMA method.

FIG. 7 is a characteristic diagram showing a weight change amount of a solute raw material GaP in a comparative example.

[Explanation of symbols]

 2 Crucible 3a, 3b, 3c Heater 5 Solute raw material 8 Raw material melt 9 Multi-component compound mixed crystal Single crystal

Claims (1)

[Claims] 1. A raw material melt having a predetermined chemical composition composed of the at least three elements forming the multi-component compound mixed crystal is prepared from a multi-component compound mixed crystal single crystal composed of at least three elements. In the melt growth by supplying the solute raw material consisting of at least one element of the elements forming the multi-component compound mixed crystal from the upper surface of the raw material melt held in the crucible, The output of the heater is controlled so that the temperature gradually decreases from the upper part to the lower part, and the raw material melt is gradually solidified from the lower part to the upper part to perform single crystal growth of the multi-component compound mixed crystal. Detecting the weight reduction amount of the solute raw material per unit time during the growth of the single crystal, controlling the output of the heater according to the weight reduction amount, and adjusting the growth rate of the single crystal, Multi-dimensional system Method for producing compound mixed crystal single crystal.