JP6400946B2 - Method for producing Si-Ge solid solution single crystal - Google Patents

Description

  The present invention relates to a production method for producing a solid solution having a uniform composition and single crystallinity while preventing cracks.

  Conventionally, a method called “saturated melting zone transfer method” has been proposed as one of the effective methods for producing a solid solution having a uniform composition and single crystallinity (hereinafter simply referred to as “solid solution single crystal”). Yes. This “saturation melting zone transfer method” is a method in which a component having a low melting point is sandwiched between a seed crystal and a raw material having a high melting point, and heated under a relatively low temperature gradient of about 10 ° C./cm to melt between the seed crystal and the raw material. This is a method for producing a single crystal in which a band is formed and the melting zone is sequentially moved to the raw material side by utilizing a temperature gradient to take over the orientation of the seed crystal.

  This method is disclosed in Japanese Patent Laid-Open No. 2003-238287 (Patent Document 1). When the temperature gradient is low and the width of the melting zone is small, the solute concentration is almost saturated throughout the melting zone, making it easy to control the composition of the growth crystal and to grow a crystal with a uniform composition. .

JP 2003-238287 A

  However, the single crystal can be produced by the above conventional method only when the seed crystal has a both-end composition of the solid solution. In that case, the composition of the seed crystal and the grown crystal are different, so that the thermal expansion coefficient differs between the two. There was a problem that cracks were likely to occur in the grown crystal when it was cooled from a growth temperature of 1000 ° C. or higher to room temperature.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for producing a solid solution single crystal suitable for producing a solid solution (mixed crystal) single crystal having a uniform composition without cracks with good reproducibility. And

  In order to achieve the above object, the present invention includes a step of holding a seed crystal in the container so that at least a part of the seed crystal is exposed in the internal space of the container, and a first melting point lower than that of the seed crystal in the internal space. Storing a first raw material and a second raw material having a melting point higher than that of the first raw material, and a second raw material in which the temperatures of the first raw material and the second raw material are higher than the melting point of the first raw material The first raw material is melted by melting the first raw material by heating the container so as to have a temperature gradient in which the temperature rises in one direction away from the seed crystal so as to be lower than the melting point of A portion of the solid solution melt produced by dissolving the second raw material that contacts the seed crystal is crystallized by a temperature gradient, and the crystal is grown in one direction in which the temperature rises. The first raw material is discharged into the solid solution melt with the growth of In this case, the second raw material that has remained undissolved further dissolves in the solid solution melt, so that the crystal growth is performed while maintaining the saturation state of the second raw material in the solid solution melt. A manufacturing method is provided.

  The method of the present invention does not use a method in which a first raw material having a low melting point is sandwiched between a seed crystal having a high melting point and a second raw material, and a solid solution single crystal is grown on the seed crystal. While suppressing the generation of cracks due to the effects of thermal expansion and contraction of crystals, it is possible to continuously generate a solid solution having a uniform composition as in the case of the saturated melting zone transfer method.

  In the method of the present invention, when the first raw material is discharged into the solid solution melt along with the crystal growth, the second raw material remaining undissolved further dissolves in the solid solution melt, so that the solid solution Since the saturation state of the second raw material in the melt is maintained, it is possible to continue growing crystals having a uniform composition as long as the temperature of the crystal growth interface is kept constant. However, when the temperature gradient is sufficiently small, the temperature change at the crystal growth interface is small, and the change in the composition of the grown crystal due to the temperature change at the crystal growth interface is also small. In this case, a solid solution single crystal excellent in uniformity and unity can be obtained without particularly adjusting the temperature. Depending on the required productivity (growth rate), ease of management, and quality, the magnitude of the temperature gradient and the presence or absence of temperature adjustment at the crystal growth interface can be selected as appropriate.

  In the method of the present invention, the seed crystal can be held in the container by holding the seed crystal in a funnel-shaped hole provided in the jig and accommodating the jig in the container. By using such a jig, it is possible to gradually increase the diameter of the crystal and reduce the probability of polycrystallization.

  According to another aspect of the present invention, a first raw material and a second raw material having a melting point higher than that of the first raw material are accommodated in an internal space of a container provided with a plurality of linear grooves on a part of the inner surface thereof. The first raw material and the second raw material have a temperature higher than the melting point of the first raw material and lower than the melting point of the second raw material, and away from the region where the plurality of linear grooves are provided. Of the solid solution melt produced by melting the first raw material by melting the first raw material by melting the second raw material by heating the container so that a temperature gradient in which the temperature rises toward the Crystallizing a portion in contact with a region provided with a plurality of linear grooves by a temperature gradient and growing the crystal in one direction in which the temperature rises. When the raw material is discharged into the solid solution melt, the second raw material remaining undissolved is the solid solution. By further blend in the liquid crystal grown while maintaining the saturated state of the second material in the solid solution melt is configured to be performed, to provide a method of manufacturing a solid solution single crystal.

  As described in Example 3 below, instead of using a seed crystal, a plurality of linear grooves are provided on the surface of a jig that constitutes a part of the container, and a crystal is obtained from the region where the linear grooves are provided. Even when grown, it is possible to produce a solid solution single crystal with high uniformity.

  The method of the present invention preferably further comprises a step of adjusting the temperature of the crystal growth interface moving with crystal growth toward a temperature corresponding to the composition of the solid solution single crystal to be produced. As already mentioned, it is possible to obtain a highly uniform solid solution single crystal without particularly adjusting the temperature when the temperature gradient is small, etc., but after the melt part of the solid solution is formed in the container, As the crystal growth interface moves to the high temperature side, the container is moved to the low temperature side, the heater used to heat the container is moved to the high temperature side, or the temperature distribution in the container is controlled by controlling the heater. It is preferable to adjust the temperature of the crystal growth interface by changing the temperature.

In the method of the present invention, it is possible to use, as one of the first raw material and the second raw material, a solid solution raw material composed of each component of the solid solution single crystal. As shown in Example 3 to be described later, for example, when manufacturing a solid solution single crystal containing Si and Ge as components, the first and second raw materials are made to be Ge and Si which are both end components of Si _1-x Ge _x. Is not essential, and a solid solution material containing both Si and Ge components may be used.

  In the method of the present invention, it is desirable to use a raw material having a specific gravity smaller than that of the first raw material as the second raw material. If the specific gravity of the second raw material is small, the specific gravity of the second raw material remaining undissolved during crystal growth is smaller than the specific gravity of the solid solution melt and floats in the solid solution melt. This is because it can be prevented.

  According to the method for producing a solid solution single crystal of the present invention, a melt part is formed under a relatively low temperature gradient of typically 5 to 50 ° C./cm, and undissolved components remain in the melt part. Since it is arranged in a state where it is formed (floating state when the specific gravity is lighter than the melt part), it is possible to form a saturated melt part having a desired component in the initial stage of crystal growth. Also, as the crystal growth progresses, the melt component tends to change due to segregation during the solidification of the melt, but the component that remains undissolved and is disposed in the melt portion plays a role in adjusting the component. Therefore, the composition control of the solid solution to be grown can be controlled only by the temperature of the growth interface, and crystals with a uniform composition and high uniformity can be produced. In addition, according to the method of the present invention, it is possible to use a seed crystal having a component different from that of a small seed crystal or both ends of the solid solution, making it difficult to be affected by the thermal expansion and contraction of the seed crystal and suppressing the occurrence of cracks. Therefore, a crack-free single crystal can be manufactured with good reproducibility.

Sectional drawing of the crucible used for the manufacturing method of the solid solution single crystal which concerns on Example 1 of this invention. The top view of the crucible used for the manufacturing method of the solid solution single crystal which concerns on Example 1 of this invention. Sectional drawing of the quartz jig | tool used for the manufacturing method of the solid solution single crystal which concerns on Example 1 of this invention. The top view of the quartz jig | tool used for the manufacturing method of the solid solution single crystal which concerns on Example 1 of this invention. Sectional drawing of the sample before a heating used for the manufacturing method of the solid solution single crystal which concerns on Example 1 of this invention (The quartz jig, seed crystal Si, raw material Si, raw material Ge is arrange | positioned in a crucible, and also in a quartz ampule, it is vacuum (Shows the sealed state). Si-Ge binary phase diagram. In Example 1 of this invention, Ge melt | dissolves and it becomes a melt, and sectional drawing which shows the state melt | dissolved until Si became a saturated density | concentration in the melt. Undissolved Si floats on the melt. Sectional drawing which shows the state which the solid solution single crystal started growing on the seed crystal which remained unmelted in Example 1 of this invention. Sectional drawing which shows the state which the solid solution single crystal further grew in Example 1 of this invention. In the Example 1 of this invention, the schematic diagram which shows the concept of the movement of the sample for obtaining heating and a uniform composition. The comparison graph of the number of cracks observed in the 2-inch diameter crystal in Example 1 of this invention and the number of cracks observed in the 2-inch diameter crystal manufactured by the conventional method. The graph which shows radial direction Ge density | concentration distribution of the crystal manufactured in Example 1 of this invention. FIG. 6 is an InAs-GaAs phase diagram in Example 2 of the present invention. Sectional drawing of the vacuum enclosure sample in Example 2 of this invention. The graph which shows the axial direction InAs density | concentration distribution of the crystal manufactured in Example 2 of this invention. The perspective view of the grooved quartz jig | tool instead of the seed crystal used in Example 3 of this invention. Sectional drawing of the vacuum enclosure sample in Example 3 of this invention.

  Hereinafter, the present invention will be described in more detail with reference to examples. The technical scope of the method for producing a solid solution single crystal according to the present invention is not limited to the specific configurations shown in the following examples. For example, the shape of the container used in the method of the present invention is arbitrary, and the values of various size parameters are also arbitrary.

In the method for producing a solid solution single crystal according to the present invention, first, an example of producing a solid solution Si _0.5 Ge _{0.5 in} which silicon Si and germanium Ge are mixed in half will be described.

Prepare a crucible 1 made of boron nitride BN with an inner diameter of 50 mm, a depth of 100 mm, and a thickness of 2 mm, and a quartz jig 2 with an outer diameter of 49.5 mm, a thickness of 10 mm, and a hole 3 with an inner diameter of 3 mm. (The “container” in the present embodiment is constituted by the crucible 1 and the jig 2). 1a shows a cross-sectional view of the boron nitride crucible 1, FIG. 1b shows a plan view, FIG. 2a shows a cross-sectional view of the quartz jig 2, and FIG. 2b shows a plan view thereof. Next, a seed crystal 4 made of Si and having a <100> orientation (outer diameter 2.95 mm, length 20 mm) is inserted into the hole 3 at the center of the quartz jig 2 and placed on the bottom of the crucible 1. Next, a polycrystalline Si raw material (weight about 46 grams) crushed into a shot shape is placed around it, and a polycrystalline Ge raw material (outer diameter 49.5 mm, thickness 20 mm, weight about 5 mm) is formed on it. 204 grams) 6 are sequentially inserted, the crucible 1 is inserted into the quartz ampule 7, evacuated from the opening at one end of the quartz ampule 7, and the end is welded together with the sealing plug 8 to about 1 × 10 ⁻ Vacuum seal at ⁴ Pa vacuum. FIG. 3 is a cross-sectional view showing the sample in this state.

The vacuum sealed sample prepared as described above is placed in a temperature gradient furnace and heated to cause crystal growth. The crystal growth will be described based on the Si—Ge phase diagram shown in FIG. In the graph of FIG. 4, the vertical axis represents the temperature and the horizontal axis represents the (x when the composition expressed in Si _1-x Ge _x) the percentage of Ge in the solid solution or solid solution melt.

From the phase diagram, it can be seen that Si has a melting point of 1414 ° C. and Ge has a melting point of 938 ° C., and the two melt at any ratio to form a solid solution. In addition, it is understood that when a crystal having a composition of Si _0.5 Ge _0.5 is to be manufactured, it is necessary to prepare a melt having a Ge concentration of 83 at% (atomic percent, the ratio of the number of Ge atoms to the total number of atoms in the melt). (Refer to the horizontal axis value at the intersection of the isotherm of about 1100 ° C., the solid phase line, and the liquid phase line in the graph of FIG. 4). When heated so that the temperature on the side of the seed crystal 4 protruding from the quartz jig 2 is about 1100 ° C. under a temperature gradient of 5 to 50 ° C./cm (the temperature rises above the plane of FIG. 3), it melts. When the Ge raw material 6 dissolves part of the seed crystal 4 and part of the Si raw material 5, the melt 9 having a Ge concentration of 83 at%, which is the condition described above, is realized. When a solid solution single crystal is produced with a composition other than Si _0.5 Ge _0.5 , the surface temperature on the side of the seed crystal 4 of the quartz jig 2 is a solid phase at a desired composition (horizontal axis value) in the graph of FIG. The quartz ampule 7 may be heated so as to match the temperature of the line.

In this case, since the Ge raw material 6 has a melting point of 938 ° C., the entire amount is melted, and the Si raw material 5 is dissolved in the Ge melt until a saturated concentration is reached. About 204 grams of Ge is equivalent to about 2.81 moles, and about 46 grams of Si is equivalent to about 1.64 moles, so when melt 9 having a composition of Si _0.17 Ge _0.83 is formed, about 16.6 grams of Si is melted. The remainder of the dissolution remains solid.

The undissolved Si solid 5 ′ floats on the melt 9 because the specific gravity is smaller than that of the melt 9 having a composition of Si _0.17 Ge _0.83 . A cross-sectional view of this state is shown in FIG. In this state, if a temperature gradient is applied, the temperature differs by the temperature gradient above and below the melt, and the saturation concentration of Ge also varies. When a temperature gradient is applied so that the side away from the seed crystal 4 (above the paper surface in FIG. 3) is at a high temperature, as is apparent from the state diagram of FIG. The Ge concentration is low. Such a concentration difference of Ge in the melt causes diffusion in the melt, and Ge is transported from a higher concentration to a lower one. That is, it is transported in a direction away from the side where the seed crystal 4 is installed. Then, on the seed crystal 4 side with a high Ge concentration, the Ge concentration decreases, Si becomes supersaturated, and crystal growth occurs.

FIG. 6 is a cross-sectional view showing a state in which a crystal 10 having a Si _0.5 Ge _0.5 composition has started to grow on the unmelted seed crystal 4. Since a crystal of Si _0.5 Ge _0.5 grows from the Si _0.17 Ge _0.83 melt, Ge is discharged into the melt 9 during crystallization, and the Ge concentration in the melt 9 tends to increase. If the temperature of the liquid 9 is kept at 1100 ° C., the Si solid 5 ′ that remains undissolved and floats on the top of the melt 9 dissolves in the melt 9 and again has a composition of Si _0.17 Ge _{0.83 having a} saturation concentration at 1100 ° C. Since it becomes the melt 9, the crystal having a constant composition of Si _0.5 Ge _0.5 continues to grow through the supersaturation of Si due to Ge diffusion in the melt. Since the Si solid 5 ′ floating in the melt 9 dissolves into the melt 9 as the crystal growth proceeds, the amount thereof decreases. FIG. 7 is a cross-sectional view showing a state in which the crystal growth of Si _0.5 Ge _0.5 has further progressed.

  In addition, since a temperature gradient is generated in the crucible 1 that increases in temperature in one direction away from the seed crystal 4, the temperature of the crystal growth interface also increases as the crystal 10 grows. To always maintain the melt temperature at the growth interface at 1100 ° C, the quartz ampule 7 is moved to the low temperature side by the length of crystal growth, or the heater section is moved to the high temperature side by the length of crystal growth. Alternatively, the temperature distribution of the heater may be changed to adjust the temperature of the crystal growth interface.

  In order to suppress the composition change of the grown crystal due to temperature rise, in Example 1 and Examples 2 and 3 to be described later, the quartz ampule 7 is moved to the low temperature side of the heater in accordance with the method described in Patent Document 1. Grew.

  Specifically, as shown in FIG. 8, the temperature gradient furnace 11 includes an upper heater 12 and a lower heater 13, and a desired temperature gradient can be applied by adjusting the temperature settings of the two heater portions. While the quartz ampule 7 attached to the support rod 14 is heated, the drive mechanism 15 moves the support rod 14 connected to the drive mechanism 15 at a constant speed, thereby bringing the temperature of the crystal growth interface to around 1100 ° C. Crystals were grown while adjusting.

  The temperature gradient furnace 11 has a donut shape. In the hollow portion, the crucible 1 in which the seed crystal 4 to the Ge raw material 6 are arranged as shown in FIG. An enclosed quartz ampule 7 is disposed. The quartz ampule 7 is attached to the distal end of a support rod 14 extending in the axial direction. A drive mechanism 15 using a step motor as a power source is provided on the proximal end side of the support rod 14 and formed on the support rod 14. It is designed to receive power transmission by a rack and pinion that engages with the groove and descends. As a result, the quartz ampule 7 attached to the tip of the support rod 14 can move relative to the temperature gradient furnace 11 at a controlled speed in the axial direction in the donut-shaped space of the temperature gradient furnace 11. The moving speed of the quartz ampule 7 in the temperature gradient furnace space is controlled to a predetermined speed by a control mechanism (not shown). This control mechanism can also set the speed of the quartz ampule 7 with respect to the temperature gradient furnace 11 by inputting the speed, but the speed is controlled according to a program by incorporating a microprocessor so as to be a predetermined speed. You can also The temperature gradient furnace 11 is provided with an upper heater 12 and a lower heater 13 in the axial direction as shown in the figure, and can control the temperature independently of each other (the temperature can be controlled continuously in the axial direction in each heater). Therefore, the temperature gradient furnace 11 as a whole can be heated with an arbitrary axial temperature distribution). In the present embodiment, each heater temperature is controlled by a control circuit (not shown) so that the temperature increases from the lower heater 13 toward the upper heater 12.

  In this embodiment, the quartz ampule 7 is moved to the low temperature side in accordance with the moving speed of the crystal growth interface to the high temperature side, the temperature of the growth interface, that is, the Ge concentration at the growth interface is kept constant, and a crystal with a uniform composition is formed. Grow. The moving speed of the crystal growth interface, that is, the moving speed of the quartz ampule 7 can be determined according to the method described in Patent Document 1.

…（１）
ここで、C_Sは溶質Geの結晶中の濃度（原子数比。例えば50 at%の場合は0.5）、C_LはC_Sと平衡関係にある液相組成の溶質Ge濃度（原子数比）、Dは液相中での溶質と溶媒間の相互拡散係数(m²/s)である。Tはルツボ１内の温度（℃）、Zは温度勾配炉１１の軸方向に向かって（下部ヒータ１３から上部ヒータ１２に向かって）の位置（cm）、Cは液相線において温度に依存して変化するGe濃度（原子数比）である。温度勾配∂Ｔ／∂Ｚ＝G(℃/cm)、液相線の勾配∂Ｔ／∂Ｃ＝m(℃/mol)とおき、Vについて解くと、

…（２）
が得られる。この速度が、拡散律速定常状態結晶成長が成り立っている場合の成長界面の移動速度である。本実施例１においては、図４の状態図からC_L=0.83, C_S=0.5であり、液相線の勾配ｍはC_L=0.83の近傍で約−650℃/molである。Dは測定から約9.5×10^-9m²/sであることが判っているので、温度勾配G=10℃/cmの場合、V=0.15mm/hと計算される。したがって、図８の駆動機構１５等により石英アンプル７をVに合わせて低温側に移動させれば、結晶成長界面の温度を一定に保つことができる。あるいは、Vに合わせて温度勾配炉１１を高温側に動かしたり、上部ヒータ１２，下部ヒータ１３において1100℃となる位置をVに合わせて図８の紙面上方へと動かしたりしてもよい。ここで、石英アンプル７の移動等を開始する時点は、事前に数値解析等によって決定してもよいし、任意の手段により結晶成長が始まったことを実際に観測して決定してもよいし、あるいは同条件で実験を繰り返すことにより経験的に決定してもよい。本実施例においては、種結晶４が設定温度である1100℃に達してから２時間程度後に結晶成長が始まることを数値解析により予測した上で、この予測された時刻から石英アンプル７の移動を開始した。 Specifically, when the melt mass discharged into the melt during crystallization by segregation is equal to the amount transported into the melt ahead of the interface by diffusion (diffusion-controlled steady state crystal growth), Assuming V, the following relationship holds.

... (1)
Here, C _S is the concentration of solute Ge in the crystal (atomic ratio, eg 0.5 at 50 at%), and C _L is the solute Ge concentration (atomic ratio) of the liquid phase composition in equilibrium with C _S. , D is the mutual diffusion coefficient (m ² / s) between the solute and the solvent in the liquid phase. T is the temperature in the crucible 1 (° C.), Z is the position (cm) in the axial direction of the temperature gradient furnace 11 (from the lower heater 13 to the upper heater 12), and C is temperature dependent on the liquidus Thus, the Ge concentration (atomic ratio) changes. Temperature gradient ∂T / ∂Z = G (° C / cm), liquidus gradient ∂T / ∂C = m (° C / mol), and solving for V,

... (2)
Is obtained. This speed is the moving speed of the growth interface when diffusion-controlled steady-state crystal growth is established. In Example 1, C _L = 0.83, C _S = 0.5 from the state diagram of FIG. 4, and the gradient m of the liquidus is about −650 ° C./mol in the vicinity of C _L = 0.83. Since D is known to be about 9.5 × 10 ⁻⁹ m ² / s from the measurement, when the temperature gradient G = 10 ° C./cm, V = 0.15 mm / h is calculated. Therefore, if the quartz ampule 7 is moved to the low temperature side in accordance with V by the drive mechanism 15 in FIG. 8, the temperature of the crystal growth interface can be kept constant. Alternatively, the temperature gradient furnace 11 may be moved to the high temperature side in accordance with V, or the position where the temperature of the upper heater 12 and the lower heater 13 becomes 1100 ° C. may be moved upward in FIG. Here, the point of time when the movement of the quartz ampule 7 is started may be determined by numerical analysis or the like in advance, or may be determined by actually observing that crystal growth has started by any means. Alternatively, it may be determined empirically by repeating the experiment under the same conditions. In this embodiment, the crystal ampoule 7 is moved from the predicted time after predicting that crystal growth will start about two hours after the seed crystal 4 reaches the set temperature of 1100 ° C. Started.

  FIG. 9 shows the number of cracks observed in a plane having a diameter of 50 mm by the conventional method (a) (unlike the configuration of FIG. 3, the jig 2 is not used, but the seed crystal, polycrystalline Ge raw material, polycrystalline Si raw material It is the graph which compared with the method (b) of Example 1 of this invention which accommodated in the crucible 1 in order and heated under the temperature gradient. Each is shown by an average number of cracks, a maximum number of cracks and a minimum number of cracks in 10 crystal growths. As shown in FIG. 9, in the method of the present invention, the number of cracks is greatly reduced compared to the conventional method, and the average is about two in the plane. It can also be seen that a state in which the crack is completely eliminated can be realized.

  FIG. 10 shows the Ge concentration distribution in the vertical direction in the growth direction of the solid solution 50 mm diameter substrate manufactured by the method of Example 1 of the present invention. As can be seen from FIG. 10, the Ge concentration is 50 ± 1 at%, indicating a very uniform distribution.

As described above, it can be seen that when a Si _1-x Ge _x solid solution single crystal is produced using the method of the present invention, a single crystal having excellent composition uniformity can be produced while preventing the occurrence of cracks.

In the first embodiment, the case of producing a solid solution (mixed crystal) Si _0.5 Ge _0.5 of silicon and germanium has been described as an example. However, the method of the present invention is limited to the case of producing a solid solution (mixed crystal) of silicon and germanium. Instead, it can be applied to various solid solutions (mixed crystals). Hereinafter, a case where In _0.1 Ga _0.9 As, which is a mixed crystal of gallium arsenide (GaAs) and indium arsenide (InAs), will be described.

In the same manner as in Example 1, a seed crystal (outer diameter 2.95 mm, length 20 mm) 16 made of GaAs and having a {100} face is inserted into the crucible 1 while being held by a quartz jig 17. A polycrystalline lump GaAs source 18 is inserted around the seed crystal 16. Next, a massive polycrystalline InAs raw material 19 is inserted. FIG. 11 shows a GaAs-InAs phase diagram. It can be seen from the phase diagram that it is necessary to form a melt with an In _0.6 Ga _0.4 As composition in order to obtain a crystal with an In _0.1 Ga _0.9 As composition. In this combination, since the InAs material 19 has a lower melting point than the both materials 18 and 19, InAs melts first, and the GaAs material 18 dissolves in the InAs melt. A state in which about 150 grams of GaAs material 18 and about 200 grams of InAs material 19 were charged was used as a starting sample. This time, a funnel-shaped hole is provided on one side of the quartz jig 17, and the seed crystal 16 is held in this hole. This is to reduce the probability of polycrystallization by gradually increasing the diameter of the In _0.1 Ga _0.9 As crystal grown by taking over the orientation and shape of the seed crystal 16.

FIG. 12 shows a cross-sectional view of the starting sample in a state where the quartz ampule 7 is vacuum-sealed. The quartz ampoule-enclosed sample prepared as described above is placed in the temperature gradient furnace 11 and heated. The melt side surface of the GaAs seed crystal 16 is about 1120 ° C., and the temperature gradient in the vicinity of the seed crystal 16 is about 10 Heating was performed so that the temperature became ℃ / cm (the temperature rose above the paper surface in FIG. 12). Since the melting point of GaAs is 1238 ° C., the GaAs raw material 18 remains solid, but InAs has a melting point of 942 ° C., it melts to form a melt. When the temperature on the melt side of the seed crystal 16 is kept at 1120 ° C., the solid GaAs material 18 gradually dissolves in the InAs melt. In about 3 hours, the GaAs raw material 18 was dissolved in the InAs melt to a saturation concentration of 1120 ° C. to form a melt with an In _0.6 Ga _0.4 As composition, and crystal growth began. Crystal growth occurs in the same process as that described in the first embodiment with reference to FIGS. That is, InAs diffuses to the high temperature side due to the concentration difference caused by the temperature gradient, and the melt in the portion in contact with the seed crystal 16 is crystallized due to supersaturation of GaAs. As in Example 1, InAs is discharged into the solid solution melt during crystallization. However, if the melt temperature at the crystal growth interface is kept at 1120 ° C, the GaAs raw material that remains undissolved and floats above the melt. 18 (because the specific gravity of GaAs is smaller than the specific gravity of In _0.6 Ga _0.4 As, the undissolved GaAs raw material 18 floated in the melt) and the GaAs saturation state is maintained in the melt. A crystal having a constant composition of In _0.1 Ga _0.9 As will continue to grow. Since the crystal grows in the direction away from the seed crystal 16 (high temperature side) in the crucible 1, the crucible 1 is moved at a speed of 0.1 mm / h (the above formula (1), (2), the crystal growth interface temperature was always kept at 1120 ° C. by moving toward the lower heater 13 where the temperature was low. By doing so, it was possible to grow a crystal of In _0.1 Ga _0.9 As composition over a length of 40 mm or more. In this combination of raw materials 18 and 19, the GaAs raw material 18 is lighter, so that the undissolved GaAs raw material 18 floats on the melt and plays a role in adjusting the melt components and, in turn, the components of the grown crystal. Crystal was obtained.

  FIG. 13 shows the composition distribution in the axial direction (from the bottom to the top of FIG. 12) of the crystal grown in Example 2 of the present invention. The crystal diameter was not constant because a jig having a conical depression was used as the seed crystal holding jig 17, but the composition of the grown crystal was very good because the InAs concentration was within the range of 10 ± 1 mol%. It showed uniformity. With regard to cracks, there was also an effect of gradually increasing the crystal diameter, which could be completely zero.

  It is not essential to use seed crystals of both end components that form a mixed crystal. An example is shown in Example 3. In manufacturing a solid solution single crystal of silicon Si and germanium Ge, a grooved quartz jig 20 shown in FIG. 14 was used instead of a seed crystal.

On one surface of the grooving quartz jig 20, a linear groove 21 having a depth of 1 mm and a width of 1 mm is dug over the entire surface with an interval of 3 mm. First, the jig 20 is placed on the bottom of the crucible 1, and then a massive polycrystalline Si raw material 22 (about 20 grams) and a solid solution polycrystalline Si _0.05 Ge _0.95 raw material 23 (about 230 grams) processed into a cylindrical shape. Was inserted and vacuum sealed in a quartz ampule 7 (FIG. 15).

When the quartz ampule 7 was heated so that the temperature of the groove side surface portion of the grooving quartz jig 20 was 1068 ° C., the liquidus temperature of the Si _0.05 Ge _0.95 solid solution raw material 23 was 1008 ° C. A liquid was formed, and the Si raw material 22 was further dissolved until the saturation concentration of Si _0.11 Ge _0.89 was _reached . In this case, since the liquidus temperature 1008 ° C. of the solid solution Si _0.05 Ge _0.95 was lower by 50 ° C. or more than the crystal growth temperature of 1068 ° C., a melt having a desired composition could be formed. From various experiments, it has been found that when a combination of solid solution and Si is used as a starting material, good results can be obtained when the liquidus temperature of the solid solution is lower by 50 ° C. or more than the growth temperature.

After forming the saturated melt as described above, the crucible is adjusted to about 0.15 mm / h (the above-mentioned temperature is maintained while keeping the temperature gradient in the axial direction of the crucible at about 15 ° C./cm (the temperature rises above the paper surface of FIG. 15). It was determined based on the equations (1) and (2)) and moved in the direction of the lower heater 13. Crystallization proceeds continuously in the same process as described with reference to FIGS. That is, Si _0.05 Ge _0.95 diffuses to the high temperature side due to the concentration difference caused by the temperature gradient, and the melt in the portion that comes into contact with the grooved quartz jig 20 due to Si supersaturation has a Si _0.4 Ge _0.6 composition (solid phase in FIG. 4). Crystallize at a composition corresponding to 1068 ° C. in the wire. Similar to Examples 1 and 2, Si _0.05 Ge _0.95 is discharged into the solid solution melt during crystallization. However, if the melt temperature at the crystal growth interface is maintained at 1068 ° C., it will remain undissolved and above the melt. The floating Si raw material 22 (the specific gravity of Si is smaller than the specific gravity of Si _0.11 Ge _0.89 , so the undissolved Si raw material 22 floated in the melt) was dissolved in the melt and the Si saturation state was maintained. Therefore, a crystal having a constant composition of Si _0.4 Ge _0.6 continues to grow on the high temperature side. A single crystal having a composition of Si _0.4 Ge _0.6 was thus obtained. The grooving quartz jig 20 played the role of single crystal nucleation instead of the seed crystal. The manufactured Si _0.4 Ge _0.6 single crystal could be easily separated from the grooved quartz jig 20, and the obtained Si _0.4 Ge _0.6 single crystal had no cracks. The composition was also highly uniform with a Ge concentration of 60 ± 1 at% within the crystal plane cut into rings.

In this embodiment, a combination of solid solution Si _0.05 Ge _0.95 and Si is used as a starting material, but a combination of a solid solution composed of Si and Ge and Ge may be used. In that case, it is desirable that the liquidus temperature of the solid solution to be used is 50 ° C. or more higher than that of Ge. Even when seed crystals are used as in Examples 1 and 2, a solid solution raw material may be used instead of components at both ends.

  As described above, according to the method for producing a solid solution single crystal according to the present invention, a solid solution single crystal having a constant composition and high uniformity can be produced. In addition, according to the method of the present invention, it is possible to use a seed crystal having a component different from that of a small seed crystal or both ends of the solid solution, making it difficult to be affected by the thermal expansion and contraction of the seed crystal and suppressing the occurrence of cracks. Therefore, a single crystal without cracks can be produced with good reproducibility. In addition, the method for producing a solid solution single crystal according to the present invention is not limited to the production of a specific material, and can be widely applied to the production of a general solid solution single crystal. Therefore, the method for producing a solid solution single crystal according to the present invention is particularly suitable for the production of semiconductor solid solution single crystals such as InAs-GaAs, Si-Ge, and PbTe-SnTe that require high quality and compositional uniformity. Is preferred.

1 Crucible 2 Quartz jig 3 Hole 4 Si seed crystal 5 Raw material Si
5 'Undissolved raw material Si
6 Raw material Ge
7 Quartz ampule 8 Plug for vacuum sealing
9 Melt 10 Solid solution single crystal grown on seed crystal
11 Temperature gradient furnace 12 Upper heater 13 Lower heater 14 Support rod 15 Drive mechanism 16 GaAs seed crystal 17 Quartz jig 18 GaAs raw material 19 InAs raw material 20 Grooved quartz jig 21 Linear groove 22 Si raw material 23 Si _0.05 Ge _0.95 raw material

Claims (3)

Holding the seed crystal in the container such that at least a portion of the seed crystal is exposed in the internal space of the container;
Disposing a bulk-like second raw material containing Si on the upper side of the seed crystal;
Disposing a first raw material having a lower melting point than that of the second raw material and containing Ge on the upper side of the second raw material;
The temperature of the first raw material and the second raw material is higher than the melting point of the first raw material and lower than the melting point of the second raw material, and the temperature is in one direction away from the seed crystal. Of the solid solution melt produced by melting the first raw material by melting the first raw material by melting the second raw material by heating the container so that a temperature gradient increases. Crystallizing a portion in contact with the seed crystal by the temperature gradient, and growing the crystal in the one direction in which the temperature rises. When the second raw material remaining undissolved in the solid solution melt is further dissolved in the solid solution melt, crystal growth is maintained while maintaining the saturation state of the second raw material in the solid solution melt. Si-Ge system configured to be performed A method for producing a solid solution single crystal. With the second raw material floating on the solid solution melt, the upper side where the first raw material is arranged before heating the container is the lower side where the seed crystal is arranged before heating the container The manufacturing method according to claim 1, further comprising a step of applying a temperature gradient so that the temperature becomes higher than that.   The manufacturing method according to claim 1, further comprising a step of adjusting a temperature of a crystal growth interface moving with crystal growth toward a temperature corresponding to a composition of the solid solution single crystal to be manufactured.

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