A crucible for growing InP crystal and a method for growing InP crystal

Abstract

The invention discloses a crucible for InP crystal growth and a method for growing InP crystals. The crucible for InP crystal growth comprises a first crucible, a crucible cap and a second crucible; the first crucible is a hollow quartz tube with an opening upwards, which is composed of a first body, a first shoulder and a first seed crystal cavity from top to bottom in sequence; the second crucible is a hollow PBN ceramic crucible with openings at both ends, which is composed of a second body, a second shoulder, a necking cavity and a second seed crystal cavity from top to bottom in sequence; the second crucible is located inside the first crucible, and the second body is located inside the first body, the second shoulder is located inside the first shoulder, and the necking cavity and the second seed crystal cavity are located inside the first seed crystal cavity; the crucible cap is a hemispherical quartz cap, and the outer diameter of the crucible cap is not less than the outer diameter of the second crucible; the crucible cap is opened downwards in the first crucible and is located above the second crucible, and a gap is left between the crucible cap and the second crucible. The invention greatly reduces the dislocation density in the InP crystal and improves the crystallization rate.

Description

Technical Field

[0001] The invention relates to a crucible for growing InP crystal and a method for growing InP crystal, belonging to the technical field of crystal growth. Background Art

[0002] The development of the fifth generation of mobile communication technology (5G) has put forward new requirements for optical communication devices and modules, and has also driven the development of single crystal raw material InP for corresponding optical communication devices and modules.

[0003] At present, high-quality single crystal materials in the InP market are mainly grown using the vertical gradient solidification (VGF) process. Because there is a large thermal shock when the high-temperature melt is welded with the seed crystal, a large number of lattice defects will be generated at the seed crystal position. At the same time, the lattice defects existing inside the seed crystal itself will also proliferate into the crystal as it grows, resulting in a high dislocation density of the single crystal material. A large number of lattice defects can also easily grow twins at the seed crystal, resulting in a low crystallization rate.

[0004] PBN ceramic crucibles and quartz crucibles are required in the VGF growth process. The thermal conductivity of the PBN ceramic crucible along the crucible wall is 0.25 cal / cm·s·℃, while the thermal conductivity perpendicular to the crucible wall is 0.004 cal / cm·s·℃, which is about 1 / 60 of the thermal conductivity of the crucible wall. When the PBN crucible and the quartz crucible are similar in shape and fit tightly, a large amount of heat flow is conducted away through the PBN crucible wall and the quartz crucible, generating a large radial heat flow, which causes the crystal growth interface to present a concave shape toward the melt. The concave growth interface is inconsistent with the ideal planar growth interface, and thermal stress concentration is likely to occur at the edge of the growth interface, resulting in fine twins. The same horizontal plane of the concave growth interface will also cause the impurity concentration of the InP substrate to be distributed in concentric circles due to inconsistent growth time, with poor uniformity. Summary of the invention

[0005] The invention provides a crucible for growing InP crystals and a method for growing InP crystals, improves the structure of a PBN crucible, and uses a matching preparation method therewith, thereby reducing the crystal dislocation density and twin rate caused by thermal shock in the early stage of crystal growth and lattice defects inside a seed crystal, improving the shape of a growth interface, increasing crystal uniformity and crystal formation rate, and reducing the dislocation density.

[0006] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0007] A crucible for growing InP crystals, comprising a first crucible, a crucible cap and a second crucible;

[0008] The first crucible is an integrally formed hollow quartz tube with an opening upward, which is composed of a first body, a first shoulder and a first seed crystal cavity in order from top to bottom;

[0009] The second crucible is a PBN crucible, which is a hollow PBN ceramic crucible consisting of a second body, a second shoulder, a neck cavity, and a second seed crystal cavity from top to bottom, and is open at both ends;

[0010] The second crucible is located inside the first crucible, the second body is located inside the first body, the second shoulder is located inside the first shoulder, the neck cavity and the second seed crystal cavity are located inside the first seed crystal cavity, and the length of the second body is less than the length of the first body;

[0011] The crucible cap is a quartz cap with a hemispherical top and an opening facing downward. The outer diameter of the crucible cap is not less than the outer diameter of the second crucible and slightly smaller than the inner diameter of the first crucible. The crucible cap is located in the first crucible with its opening facing downward, and the crucible cap is located above the second crucible, with a gap between the crucible cap and the second crucible.

[0012] The method for growing InP crystal using the above crucible for InP crystal growth comprises the following steps in sequence:

[0013] 1) Material preparation: After cleaning the first crucible, the second crucible, the crucible cap, the InP polycrystalline material and the seed crystal, the seed crystal (the outer diameter is slightly smaller than the inner diameter of the second seed crystal cavity by 0-0.25 mm, the length is slightly smaller than the length of the second seed crystal cavity by 5-10 mm, and the second seed crystal cavity is sealed with a high-purity boron nitride BN round rod after the seed crystal is placed) is placed in the second seed crystal cavity of the second crucible, and then the InP Put polycrystalline material (96.9-99%), B2O3 (0.5-1.5%), high-purity red phosphorus (6N and above) (0.5-1.5%, calculated based on the red phosphorus vapor pressure of not less than 2.75MPa) and dopant (no dopant is added when preparing non-doped InP, 0-0.1% dopant such as sulfur, iron, zinc is added, calculated based on the doping formula and empirical parameter correction) into the second crucible, and then put them into the first crucible together with the second crucible, so that the neck cavity and the second seed crystal cavity of the second crucible are completely inside the first seed crystal cavity of the first crucible, and then put the crucible cap into the first crucible with the opening downward, and the distance from the upper edge of the second crucible is not zero, after the first crucible is evacuated, the first crucible and the crucible cap are welded and sealed together around the periphery of the crucible cap by using hydrogen-oxygen flame;

[0014] 2) Melt: Load the sealed first crucible into the InP single crystal growth VGF furnace, and start heating after sealing, so that the temperature from point B to point F of the second crucible is above the InP melting point of 1062°C, and the temperature from point A to point B is below 1062°C, so that the raw materials in the shoulder and body of the second crucible are completely melted, and part of the melt flows into the necking cavity, but the seed crystal inside the second seed crystal cavity is not melted, wherein the bottom of the second seed crystal cavity is point A, the top is point B, the top of the necking cavity is point C, the top of the second shoulder is point D, and the top of the second body is point F;

[0015] 3) Melting seeds: Keep the molten raw materials in a homogeneous state at a constant temperature, adjust the temperature so that the temperature at point A is below 1062°C and the temperature at point B is above 1062°C, so that the seed crystal is partially melted and welded with the melt;

[0016] 4) Neck shrinkage: Control the heating power of the heater to quickly cool down the second seed crystal cavity and the neck shrinkage cavity (point A to point C), so that the melt inside the neck shrinkage cavity grows rapidly along the seed crystal direction, reducing the proliferation of lattice defects inside the seed crystal into the crystal, reducing dislocation density, and at the same time, due to the high probability that the twin line of InP growth is still on both sides <100> Crystal direction, through necking, the twins that may grow can grow out of the crystal surface, thereby improving the crystallization rate; the second seed crystal cavity is closely fitted with the first seed crystal cavity, and a concave growth interface is easily formed due to the physical properties of the second crucible. The necking cavity of the second crucible does not contact the first crucible, and the surrounding is in a vacuum state, which improves the thermal conductivity, forms a flat growth interface, and improves the uniformity of the InP crystal;

[0017] 5) Growth: Reduce the cooling rate so that the melt in the second shoulder and the second body (from point C to point F) grows along the crystal direction of the crystal in the necking cavity. After the growth is completed, reduce the temperature and take out the crystal.

[0018] The above method is divided into the first stage of material preparation, the second stage of melting material, the third stage of melting seed, the fourth stage of necking and the fifth stage of growth.

[0019] When taking out the crystal, the first crucible is destroyed, the second crucible is taken out, and then the crystal is separated from the second crucible under the action of ultrasound or the like, the crystal is taken out, and the second crucible can be used repeatedly.

[0020] In order to improve the quality of the crystal, in step 3), the constant temperature duration is 20±2h. More preferably, in step 4), the cooling rate is 30±2℃ / h, and the cooling time is 1.5±0.2h. In step 5), the cooling rate during growth is 2±0.2℃ / h, and the cooling time is 100±2h; after the growth is completed, the temperature is lowered to below 150℃ at 30±2℃ / h, and the grown crystal is taken out.

[0021] In order to improve the quality of the obtained crystal, the purity of the first crucible, the second crucible and the crucible cap are all 5N or above.

[0022] In order to further improve the crystallization rate, the length of the neck cavity on the second crucible is 2 to 10 times, preferably 2 to 4 times, the length of the second seed crystal cavity.

[0023] For ease of operation, the outer diameter of the second crucible is 1 to 3 mm smaller than the inner diameter of the first crucible. That is, the outer diameter of each part of the second crucible is slightly smaller than the inner diameter of each corresponding part of the first crucible by 1 to 3 mm, such as the outer diameter of the second body is slightly smaller than the inner diameter of the first body by 1 to 3 mm, the outer diameter of the second shoulder is slightly smaller than the inner diameter of the first shoulder by 1 to 3 mm, and the outer diameter of the second seed crystal cavity is slightly smaller than the inner diameter of the first seed crystal cavity by 1 to 3 mm.

[0024] In order to improve the stability during use, the included angle and height of the first shoulder and the second shoulder are consistent; the length of the first seed crystal cavity is not less than the sum of the lengths of the necking cavity and the second seed crystal cavity.

[0025] The angle of the shoulder, that is, the size of the shoulder cone angle.

[0026] Preferably, the interval between the crucible cap and the second crucible is 25 to 35 mm.

[0027] The size of the crucible of the present application can be set according to specific production requirements. In order to meet general review requirements, the length of the first body is 300-400mm, and the inner diameter is 80-140mm; the first shoulder angle is 60-120°, and the height is 40-60mm; the inner diameter of the first seed crystal cavity is 6-12mm, and the length is 100-140mm; the outer diameter of the bottom of the crucible cap is 80-120mm, and the height is 80-120mm; the outer diameter of the second body is 80-120mm, and the length is 130-170mm; the second shoulder angle is 60-120°, and the height is 40-60mm; the length of the neck cavity is 70-110mm; the length of the second seed crystal cavity is 20-40mm. As one of the preferred specific embodiments, the length of the first body is 350±5mm, and the inner diameter is 110±5mm; the first shoulder angle is 90±5°, and the height is 50±5mm; the inner diameter of the first seed crystal cavity is 9±1mm, and the length is 120±5mm; the outer diameter of the bottom of the crucible cap is 108±5mm, and the height is 100±5mm; the outer diameter of the second body is 108±5mm, and the length is 150±5mm; the second shoulder angle is 90±5°, and the height is 50±5mm; the length of the neck cavity is 90±5mm; and the length of the second seed crystal cavity is 45±5mm.

[0028] The length direction and height direction of the present application are consistent, and are both consistent with the axial direction of the crucible.

[0029] The technologies not mentioned in the present invention are all referred to the prior art.

[0030] The crucible and growth method for InP crystal growth of the present invention greatly reduce the dislocation density in the InP crystal to less than 10% of the prior art, and increase the crystallization rate by more than 35%. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic structural diagram of a crucible used for InP crystal growth according to the present invention;

[0032] Figure 2 Schematic diagram of the structure of a crucible used for InP crystal growth in a comparative example;

[0033] In the figure, 1 is a first crucible, 11 is a first body, 12 is a first shoulder, 13 is a first seed crystal cavity, 2 is a crucible cap, 3 is a second crucible, 31 is a second body, 32 is a second shoulder, 33 is a necking cavity, and 34 is a second seed crystal cavity. DETAILED DESCRIPTION

[0034] In order to better understand the present invention, the content of the present invention is further explained below in conjunction with the embodiments, but the content of the present invention is not limited to the following embodiments.

[0035] In this application, directional words such as "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc. are based on the orientation or position relationship shown in the drawings or in use, and are only for the convenience of describing the application, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the application.

[0036] Example 1

[0037] like Figure 1 As shown, a crucible for InP crystal growth includes a first crucible 1, a crucible cap 2, and a second crucible 3;

[0038] The first crucible 1 is made of high-purity quartz with a purity of not less than 5N, and is composed of a first body 11, a first shoulder 12, and a first seed crystal cavity 13 from top to bottom; the first body is 350 mm long and has an inner diameter of 110 mm; the first shoulder has an angle of 90° and a height of 50 mm; the inner diameter of the first seed crystal cavity is 9 mm and the length is 120 mm;

[0039] The second crucible 3 is made of high-purity boron nitride ceramic with a purity of not less than 5N, and is composed of a second body 31, a second shoulder 32, a necking cavity 33 and a second seed crystal cavity 34 from top to bottom; the outer diameter of the second body is 108 mm and the length is 150 mm; the second shoulder has an angle of 90° and a height of 50 mm; the length of the necking cavity is 90 mm; the length of the second seed crystal cavity is 45 mm;

[0040] The second crucible 3 is located inside the first crucible 1 , and the second body 31 is located inside the first body 11 , the second shoulder 32 is located inside the first shoulder 12 , and the neck cavity 33 and the second seed crystal cavity 34 are located inside the first seed crystal cavity 13 ;

[0041] The crucible cap 2 is made of high-purity quartz with a purity of not less than 5N. The crucible cap 2 is a quartz cap with a hemispherical top and an opening facing downward. The outer diameter of the bottom of the crucible cap 2 is 108 mm and the height is 100 mm. The crucible cap 2 is located in the first crucible 1 with its opening facing downward, and the crucible cap 2 is located above the second crucible 3, with a gap between the crucible cap and the second crucible.

[0042] The method for growing InP crystals using the crucible comprises the following five stages connected in sequence: a first stage of material preparation, a second stage of melting material, a third stage of melting seed, a fourth stage of necking, and a fifth stage of growth;

[0043] Preparation of materials in the first stage: after cleaning the first crucible 1, the crucible cap 2, the second crucible 3, the InP polycrystalline material and the seed crystal, the seed crystal (the outer diameter is smaller than the inner diameter of the second seed crystal cavity by 0.10 mm, the length is slightly smaller than the length of the second seed crystal cavity by 8 mm, and the second seed crystal cavity is sealed with a round rod made of high-purity boron nitride BN after the seed crystal is placed) is loaded into the second seed crystal cavity 34, and then 4000 g of InP polycrystalline material, 30 g of B2O3, 40 g of high-purity red phosphorus (6N and above), and 0.5 g of dopant Fe are put into the second body 31 and the second shoulder 32, and then put into the first crucible 1 together with the second crucible 3, so that the neck cavity 33 and the second seed crystal cavity 34 are completely inside the first seed crystal cavity 13; then the crucible cap 2 is opened downward and placed into the first crucible 1, and the distance from the upper edge of the second crucible 3 is 30 mm, and the first crucible 1 is evacuated by using a vacuum equipment, and then the first crucible 1 and the crucible cap 2 are welded together by using a hydrogen-oxygen flame;

[0044] The second stage melt: the sealed first crucible 1 is loaded into the InP single crystal growth VGF furnace, and the temperature is raised after sealing, so that the temperature of point B on the second crucible 3 is 1065°C, the temperature of point F is 1070°C, the temperature of point A is 1020°C, and the temperature of point B is 1055°C, so that the raw materials in the second crucible 31 and the second shoulder 32 are completely melted, and part of the melt flows into the neck cavity 33 of the second crucible, as shown in FIG. Figure 1 As shown, the bottom of the second seed crystal cavity is point A, the top is point B, the top of the necking cavity is point C, the top of the second shoulder is point D, and the top of the second body is point F, that is, the second seed crystal cavity 34 is point AB, the necking cavity 33 is point BC, the second shoulder 32 is point CD, and the second body 31 is point DF;

[0045] The third stage is seed melting: keep the temperature constant for 20 hours to make the molten raw materials homogeneous, adjust the temperature so that the temperature of point A reaches 1030℃ and the temperature of point B is above 1065℃, so that the seed crystal is partially melted and welded with the melt;

[0046] The fourth stage of necking: the heating power of the heater is controlled to rapidly cool down the second seed crystal cavity 34 and the necking cavity 33 (point A to point C) of the second crucible, wherein the cooling rate is 30°C / h and the cooling time is 1.5h;

[0047] The fifth stage of growth: reduce the cooling rate and carry out stage crystal growth, wherein the cooling rate is 2°C / h and the cooling time is 100h; after the growth is completed, cool down to below 150°C at 30°C / h and take out the grown crystal.

[0048] After dislocation etching of the InP single crystal prepared in this embodiment, the dislocation density was measured to be 42 / cm 2 , the crystallization rate is 68%.

[0049] Comparative Example

[0050] like Figure 2 As shown, the crucible used for InP crystal growth is different from that in Example 1 in that the second crucible 3 is not provided with a neck cavity.

[0051] The method for growing InP crystals using the crucible includes the following four stages in sequence: a first stage of material preparation, a second stage of material melting, a third stage of seed melting, and a fourth stage of growth;

[0052] The first stage of material preparation: refer to Example 1;

[0053] The second stage melt: the sealed first crucible 1 is placed into the InP single crystal growth VGF furnace, and the temperature is raised after sealing, so that the temperature of point A on the second crucible 3 is 1020°C, the temperature of point C is 1060°C, and the temperature of point F is 1070°C, the raw materials in the second crucible 31 and the second shoulder 32 are completely melted, and part of the melt flows into the second seed crystal cavity 34, as shown in FIG. Figure 2 As shown;

[0054] The third stage is seed melting: keep the temperature constant for 20 hours to make the molten raw materials homogeneous, adjust the temperature so that the temperature of point A reaches 1030℃ and the temperature of point C is above 1065℃, so that the seed crystal is partially melted and welded with the melt;

[0055] Fourth stage growth: refer to Example 1.

[0056] The dislocation density of the InP single crystal prepared in this comparative example was 470 / cm after dislocation etching. 2 , the crystallization rate is 49%.

Claims

1. A method for growing InP crystals, characterized in that: A crucible for growing InP crystals, comprising a first crucible, a crucible cap, and a second crucible; The first crucible is an integrally formed hollow quartz tube with an opening upward, which is composed of a first body, a first shoulder and a first seed crystal cavity in sequence from top to bottom; The second crucible is a hollow PBN ceramic crucible which is composed of a second body, a second shoulder, a neck cavity and a second seed crystal cavity from top to bottom and is open at both ends; The second crucible is located inside the first crucible, the second body is located inside the first body, the second shoulder is located inside the first shoulder, the neck cavity and the second seed crystal cavity are located inside the first seed crystal cavity, and the length of the second body is less than the length of the first body; The crucible cap is a quartz cap with a hemispherical top and an opening facing downward. The outer diameter of the crucible cap is not less than the outer diameter of the second crucible and is smaller than the inner diameter of the first crucible. The crucible cap is located in the first crucible with its opening facing downward, and the crucible cap is located above the second crucible, with a gap between the crucible cap and the second crucible. On the second crucible, the length of the necking cavity is 2 to 10 times the length of the second seed crystal cavity. The method for growing InP crystal using the above crucible for InP crystal growth comprises the following steps in sequence: 1) Material preparation: After the first crucible, the second crucible, the crucible cap, the InP polycrystalline material and the seed crystal are cleaned, the seed crystal is loaded into the second seed crystal cavity of the second crucible, and then the InP polycrystalline material, B2O3, high-purity red phosphorus and dopant are put into the second crucible, and then put into the first crucible together with the second crucible, so that the neck cavity and the second seed crystal cavity of the second crucible are completely inside the first seed crystal cavity of the first crucible, and then the crucible cap is opened downward and put into the first crucible, leaving a gap with the upper edge of the second crucible, and after the first crucible is evacuated, the first crucible and the crucible cap are welded and sealed together around the periphery; 2) Melt: Load the sealed first crucible into the InP single crystal growth VGF furnace, and start heating after sealing, so that the temperature from point B to point F of the second crucible is above the InP melting point of 1062°C, and the temperature from point A to point B is below 1062°C, so that the raw materials in the shoulder and body of the second crucible are completely melted, and part of the melt flows into the necking cavity, but the seed crystal inside the second seed crystal cavity is not melted, wherein the bottom of the second seed crystal cavity is point A, the top is point B, the top of the necking cavity is point C, the top of the second shoulder is point D, and the top of the second body is point F; 3) Melting seeds: Keep the molten raw materials in a homogeneous state at a constant temperature, adjust the temperature so that the temperature at point A is below 1062°C and the temperature at point B is above 1062°C, so that the seed crystal is partially melted and welded with the melt; 4) Neck shrinkage: Control the heating power of the heater to rapidly cool down the second seed crystal cavity and the neck shrinkage cavity, so that the melt inside the neck shrinkage cavity grows rapidly along the seed crystal direction; 5) Growth: Reduce the cooling rate to allow the melt in the second shoulder and the second body to grow along the crystal direction of the crystal in the necking cavity. After the growth is completed, reduce the temperature and take out the crystal.

2. The method for growing InP crystal according to claim 1, characterized in that: The purity of the first crucible, the second crucible and the crucible cap are all 5N or above.

3. The method for growing InP crystal according to claim 1 or 2, characterized in that: The outer diameter of the second crucible is 1 to 3 mm smaller than the inner diameter of the first crucible.

4. The method for growing InP crystal according to claim 1 or 2, characterized in that: The included angle and height of the first shoulder and the second shoulder are consistent; the length of the first seed crystal cavity is not less than the sum of the lengths of the necking cavity and the second seed crystal cavity.

5. The method for growing InP crystal according to claim 1 or 2, characterized in that: The interval between the crucible cap and the second crucible is 25 to 35 mm.

6. The method for growing InP crystal according to claim 1 or 2, characterized in that: The length of the first body is 300-400 mm, and the inner diameter is 80-140 mm; the angle of the first shoulder is 60-120°, and the height is 40-60 mm; the inner diameter of the first seed crystal cavity is 6-12 mm, and the length is 100-140 mm; the outer diameter of the bottom of the crucible cap is 80-120 mm, and the height is 80-120 mm; the outer diameter of the second body is 80-120 mm, and the length is 130-170 mm; the angle of the second shoulder is 60-120°, and the height is 40-60 mm; the length of the neck cavity is 70-110 mm; the length of the second seed crystal cavity is 20-40 mm.

7. The method for growing InP crystal according to claim 1 or 2, characterized in that: In step 3), the constant temperature duration is 20±2h; in step 4), the cooling rate is 30±2℃ / h, and the cooling time is 1.5±0.2h.

8. The method for growing InP crystal according to claim 1 or 2, characterized in that: In step 5), the cooling rate during growth is 2±0.2°C / h, and the cooling time is 100±2h; after the growth is completed, the temperature is lowered to below 150°C at 30±2°C / h, and the grown crystal is taken out.

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