Device and Method for Continuous VGF Crystal Growth through Reverse Injection Synthesis

Abstract

The invention discloses a device and a method for continuous VGF crystal growth through reverse injection synthesis, relating to a device for preparing a semiconductor crystal and growing a single crystal, in particular to a method and a device for continuously growing the crystal in situ by using a VGF method and reverse injection synthesis. The device includes a furnace body, a crucible, a heat preservation system, a heating system, a temperature control system and an gas pressure regulation system, wherein the crucible is arranged in the furnace body, has a synthesis unit at its upper part, and has a crystal growth unit and a seed crystal unit at its lower part, and the synthesis unit is communicated with the crystal growth unit through capillary pores. Red phosphorus and boron oxide are put into the growth unit, indium and boron oxide are put into the synthesis unit, solid seed crystals are put into the seed crystal unit, and temperature and pressure are controlled to accomplish material synthesis and in-situ crystal growth. According to the invention, the capillary pores are used, the temperature and the pressure are controlled, the phosphorus bubbles rise to the indium melt in the material synthesis stage, rendering a full fusion of the two substances, and after the phosphorus gasification, the indium-phosphorus melt drops into the growth unit to finish the in-situ growth of the crystal.

Claims

1. A device for continuous VGF crystal growth through reverse injection synthesis, comprising a furnace body, a crucible, a heat preservation system, a heating system, a temperature control system and an gas pressure regulation system, characterized in that: the crucible, disposed in the furnace body, has a synthesis unit at its upper part, and has a crystal growth unit and a seed crystal unit at its lower part, and the synthesis unit is communicated with the crystal growth unit through capillary pores.

2. The device according to claim 1, characterized in that: the number of the capillary pores is more than one.

3. The device according to claim 1, characterized in that: the relationship between a radius r of the capillary pore and h is as follows: $ρ g h < \frac{2 σ}{r}$ where ρ is the density of the melt, g is the acceleration of gravity, σ is the interfacial tension of the melt, and h is the height of the melt in the synthesis unit in the crucible.

4. The device according to claim 1, characterized in that: the capillary pore has a radius of 0.1 mm to 0.15 mm.

5. The device according to claim 1, characterized in that: a heat insulation layer is provided between the synthesis unit and the crystal growth unit of the crucible.

6. The device according to claim 1, characterized in that: an observation window is provided at the top of the furnace body; the heating system comprises a heating wire arranged on the periphery of the crucible, the temperature control system comprises thermocouples, and the gas pressure regulation system comprises a gas charge and discharge pipe probing into the crucible.

7. A method for continuous VGF crystal growth through reverse injection synthesis implemented on the basis of the device for continuous VGF crystal growth through reverse injection synthesis as claimed in claim 1, characterized in that the method comprises the steps of: A. respectively feeding a solid seed crystal, a volatile element and boron oxide, and required metal and boron oxide for synthesis into the seed crystal unit, the crystal growth unit and the synthesis unit of the crucible in the furnace body; B. vacuumizing the furnace body to 10.sup.−5 Pa, and filling high-purity inert gas to 2.0 MPa; C. heating the crystal growth unit to above the sublimation temperature of the volatile element; D. heating the synthesis unit to 30° C.-100° C. higher than the melting point of the synthesized substance, ensuring that the lower limit value of the pressure of the furnace body is greater than the saturated vapor pressure of the volatile element at the aforementioned temperature, keeping the temperature of the crystal growth unit stable, enabling vapor of the volatile element to enter the synthesis unit through the capillary pores and to synthesize with the metal melt required for synthesis until bubbles of the capillary pores disappear; E. adjusting the temperature above the upper surface of the boron oxide layer of the crystal growth unit to be 10° C.-150° C. higher than the melting point of the synthesized substance, and the temperature below the boron oxide layer to be lower than the melting point of the synthesized substance, until bubbles of the capillary pores disappear; F. adjusting the temperature of the part, close to the capillary pore, of the upper part of the crystal growth unit to be higher than the melting point of the synthesized substance, and the temperature of the rest part to be lower than the sublimation temperature of the volatile element until the melt completely enters the crystal growth unit; and G. adjusting the temperature of the crystal growth unit to be higher than the melting point of the synthesized substance, and controlling the temperature distribution to carry out crystal growth.

8. The method according to claim 7, characterized in that: in step F, inert gas is charged into the furnace body, the pressure is increased by 0.2-2.0 MPa, so the pressure difference between the crystal growth unit and the synthesis unit is further increased.

9. The method according to claim 7, characterized in that: the volatile element is red phosphorus, the metal required for synthesis is indium, and in step D, the upper limit value of the pressure of the furnace body P2 satisfies the following conditions:
P2<P1−ΔP where P1 is the saturated vapor pressure of the red phosphorus, and the relationship between P1 and the temperature T is as follows: $\log_{1 0}^{P_{1}} = - \frac{6 0 7 0}{T} + 8 6 7$ ΔP is the downward additional pressure created by the maximum interfacial tension at the gas pipe as the bubbles enter the indium melt through the capillary pores during synthesis, $Δ P = \frac{2 σ}{r}$ σ is the interfacial tension of the indium melt, r is the radius of the capillary pore, and the interfacial tension of indium is σ=559.7-0.089(T−429).

10. The method according to claim 7, characterized in that: in steps D and E, through the observation window, observation is carried out until the bubbles disappear.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG. 1 is an assembly diagram showing a furnace body of a device for continuous VGF crystal growth through reverse injection synthesis;

[0033] FIG. 2 is a schematic graph showing the temperature in the first stage of synthesis;

[0034] FIG. 3 is a schematic diagram showing the reverse injection synthesis process;

[0035] FIG. 4 is a schematic graph showing the temperature in the second stage of the synthesis;

[0036] FIG. 5 is a schematic diagram showing an indium-phosphorus melt being filled into a crystal growth unit;

[0037] FIG. 6 is a schematic graph showing the temperature in the third stage of the synthesis;

[0038] FIG. 7 is a schematic graph showing the suction temperature of the indium-phosphorus;

[0039] FIG. 8 is a schematic diagram showing completion of filling the indium-phosphorus melt into a crystal growth unit;

[0040] FIG. 9 is a schematic diagram of VGF crystal growth;

[0041] FIG. 10 is a schematic diagram of a crucible for the synthesis and the crystal growth.

[0042] In the drawings, 1: portion I of crystal growth heating zone; 2: portion II of crystal growth heating zone; 3: portion III of crystal growth heating zone; 4: portion IV of crystal growth heating zone; 5: portion I of melt synthesis heating zone; 6: portion II of melt synthesis heating zone; 7: portion III of melt synthesis heating zone; 8-1: thermocouple for melt synthesis a; 8-2: thermocouple for melt synthesis b; 8-3: thermocouple for melt synthesis c; 8-4: thermocouple for melt synthesis d; 8-5: thermocouple for melt synthesis e; 8-6: thermocouple for melt synthesis f; 8-7: thermocouple for melt synthesis g; 9-1: crystal growth unit thermocouple a; 9-2: crystal growth unit thermocouple b; 9-3: crystal growth unit thermocouple c; 9-4: crystal growth unit thermocouple d; 9-5: crystal growth unit thermocouple e; 9-6: crystal growth unit thermocouple f; 9-7: crystal growth unit thermocouple g; 10: synthesis and crystal growth crucible; 10-1: synthesis unit; 10-2: capillary; 10-3: crystal growth unit; 10-4: seed crystal unit; 11: gas charge and discharge pipe; 12: heat preservation layer; 13: boron oxide for solid synthetic covering; 14: high-purity indium; 15: heat insulation layer; 16: boron oxide for solid seed crystal protection; 17: high-purity red phosphorus; 18: seed crystal; 19: observation window; 20: boron oxide for liquid synthetic covering; 21: indium melt; 22: phosphorus bubbles; 23: boron oxide for liquid seed crystal protection; 24: drops of indium-phosphorus melt; 25: solid indium phosphide; 26: indium-phosphorus melt in the crystal growth unit; 27: indium phosphide crystals; 28 heating wire.

DETAILED DESCRIPTION OF THE INVENTION

[0043] The invention will now be further described with reference to the accompanying drawings.

[0044] In the embodiment, the crystal to grow is indium phosphide, namely the volatile element is red phosphorus, the metal required for synthesis is indium, and the synthesized substance is indium phosphide.

[0045] As shown in FIG. 1, a device for continuous VGF crystal growth through reverse injection synthesis includes a furnace body, a crucible 10, a heat preservation system, a heating system, a temperature control system and a gas pressure regulation system, wherein the crucible 10 is arranged in the furnace body; with reference to FIG. 10, the crucible has a synthesis unit 10-1 at its upper part, and has a crystal growth unit 10-3 and a seed crystal unit 10-4 at its lower part, the synthesis unit 10-1 is communicated with the crystal growth unit 10-3 through capillary pores 10-2. At least one capillary pore is provided, and it's preferable to provide more theoretically, and preferably, in this example, 10 capillary pores are provided.

[0046] After high-purity indium is melted, the height value h of the indium melt is related to the radius r of a capillary pore at high temperature:

[00003] $ρ g h < \frac{2 σ}{r},$

where ρ is the density of the indium melt, g is the acceleration of gravity, σ is the interfacial tension of the indium melt, and h is the height of the indium melt.

[0047] In this example, the capillary pore 10-2 has a radius of 0.1 mm to 0.15 mm.

[0048] A heat insulation layer 15 is provided between the synthesis unit 10-1 and the crystal growth unit 10-3 of the crucible.

[0049] An observation window 19 is provided at the top of the furnace body.

[0050] A heat preservation layer 12 constitutes the heat preservation system.

[0051] And the heating system includes a heating wire 28 arranged on the periphery of the crucible 10.

[0052] The temperature control system includes thermocouples 8-1 to 8-7 and 9-1 to 9-7.

[0053] The gas pressure regulation system includes a gas charge and discharge pipe 11 which probes into the crucible 10.

[0054] In order to accurately control the temperature in the crucible, with reference to FIG. 1, the temperature control zone in the crucible is divided into seven portions, respectively: 1: portion I of crystal growth heating zone; 2: portion II of crystal growth heating zone; 3: portion III of crystal growth heating zone; 4: portion IV of crystal growth heating zone; 5: portion I of melt synthesis heating zone; 6: portion II of melt synthesis heating zone; and 7: portion III of melt synthesis heating zone.

[0055] On the basis of the above device, the synthesis of materials and the growth of crystals were accomplished by the following steps.

[0056] A. Feeding: solid seed crystals 18 were filled into the seed crystal unit 10-4 of the crucible 10 in the furnace body, red phosphorus 17 and boron oxide 16 were added into the crystal growth unit 10-3, and indium 14 and boron oxide 13 were added into the synthesis unit 10-1. The boron oxide 16 in the crystal growth unit 10-3 was liquefied to function as protection, and the boron oxide 13 in the synthesis unit 10-1 was liquefied to function as a covering.

[0057] B. The furnace body was vacuumized to 10.sup.−5 Pa, and high-purity inert gas was charged therein to 2.0 MPa.

[0058] C. The crystal growth unit 10-3 was heated to above the sublimation temperature of red phosphorus, in this example, the heating temperature was lower than the sublimation temperature of red phosphorus plus 100° C.

[0059] The heating powers in the portion I of the crystal growth heating zone, the portion II of the crystal growth heating zone, the portion III of the crystal growth heating zone and the portion IV of the crystal growth heating zone were adjusted, and boron oxide for solid seed crystal protection 16 and high-purity red phosphorus 17 in the crystal growth unit 10-3 were heated, so that the temperature in the crystal growth unit 10-3 reached higher than the sublimation temperature of the red phosphorus, as shown in FIG. 2.

[0060] The high-purity red phosphorus 17 started to decompose and volatilize, so that the pressure in the crystal growth unit 10-3 was greater than the pressure in the synthesis unit 10-1 above. At this time, the boron oxide for solid seed crystal protection 16 was melted into boron oxide for liquid seed crystal protection 23 and covered the seed crystal 18.

[0061] D. The synthesis unit 10-1 was heated to 30° C.-100° C. higher than the melting point of indium phosphide, while it was ensured that the lower pressure limit value of the furnace body was greater than the saturated vapor pressure of the volatile element at the temperature, the lower pressure limit corresponding to 30° C. higher than the melting point of indium phosphide was 3.0 MPa, the lower pressure limit corresponding to 100° C. higher than the melting point of indium phosphide was 3.4 MPa, and in this example, the pressure was greater than 4.0 MPa; the temperature of the crystal growth unit 10-3 was kept stable, the red phosphorus vapor entered the synthesis unit 10-1 through the capillary pores 10-2 to react with the indium 14 melt until bubbles of the capillary pores 10-2 disappeared.

[0062] The powers of the portion I of the melt synthesis heating zone 5, the portion II of the melt synthesis heating zone 6 and the portion III of the melt synthesis heating zone 7 were adjusted, and the boron oxide for solid synthesis covering 13 and the high-purity indium 14 in the synthesis unit 10-1 was heated so that the temperature of the synthesis unit 10-1 reached 30° C.-100° C. higher than the melting point of indium phosphide, as shown in FIG. 4, and the boron oxide for solid synthetic covering 13 and the high-purity indium 14 were melted into the boron oxide for liquid synthetic covering 20 and the indium melt 21.

[0063] The pressure lower limit value of the furnace body was ensured to be greater than 2.75 MPa, and meanwhile the temperature in the crystal growth unit 10-3 was ensured to be stable.

[0064] In addition, the upper pressure limit value of the furnace body was regulated according to formulas (1)-(4).

[0065] The reverse injection of red phosphorus had to satisfy the kinetic relationship provided in the following formulas.

[0066] The upward pressure generated by the crystal growth unit, i.e., the saturated vapor pressure (atm) of red phosphorus is a function of temperature:

[00004] $\begin{matrix} \log_{1 0}^{P_{1}} = - \frac{6 0 7 0}{T} + 8.6 7 & (1) \end{matrix}$

where P1 was the saturated vapor pressure of red phosphorus.

[0067] Interfacial tension (mN/m) of the indium melt:

σ=559.7−0.089(T−429) (2)

when the synthesis was carried out, the bubbles entered the indium melt through the capillary pores and the maximum interfacial tension at the gas pipe created a downward additional pressure ΔP:

[00005] $\begin{matrix} Δ P = \frac{2 σ}{r} & (3) \end{matrix}$

[0068] The upper limit value of the pressure of the furnace body P2 was ensured to satisfy the following relation:

P2<P1−JP (4)

The upper pressure limit satisfying the above conditions ensured that the phosphorus bubbles rose to the synthesis unit 10-1 through the capillary pores.

[0069] The phosphorus bubbles 22 volatilized in the crystal growth unit 10-3 were injected into the indium melt 21 in the synthesis unit 10-1 through the capillary pores 10-2 to start the synthesis reaction of indium and gaseous phosphorus, as shown in FIG. 3.

[0070] The change of the liquid level and the bubbling of the phosphorus were observed through the observation window 19 until the required solid red phosphorus volatilized completely and the bubbling disappeared.

E. The temperature above the upper surface of the boron oxide layer in the crystal growth unit 10-3 was adjusted to be 10° C.-150° C. higher than the melting point of the indium phosphide crystal, and the temperature below the boron oxide to be lower than the melting point of the indium phosphide crystal until the bubbles of the capillary pores 10-2 disappeared.

[0071] The heating powers of the portion I of the crystal growth heating zone 1, the portion II of the crystal growth heating zone 2, the portion III of the crystal growth heating zone 3, and the portion IV of the crystal growth heating zone 4 were adjusted, so that the upper part of the crystal growth unit 10-3 had a temperature higher than the melting point of the indium phosphide crystal, and the part, close to the seed crystal unit 10-4, of the crystal growth unit 10-3 had a temperature lower than the melting point of the indium phosphide crystal, where the boron oxide for liquid seed protection 23 was present, as shown in FIG. 6.

[0072] And then, since the temperature inside the crystal growth unit 10-3 rose, the phosphorus gas remaining in the crystal growth unit 10-3 was injected into the synthesis unit 10-1 again, and the unreacted gas re-emerged from the melt in the synthesis unit 10-1 as bubbles. The change of the liquid level and the bubbling of the phosphorus were observed through the observation window 19 until the bubbling disappeared.

[0073] And then, solid phosphorus did not exist in the growth unit 10-3, and bubbles were generated again because the temperature of the crystal growth unit was raised again, the phosphorus gas expanded and thus bubbles were generated again, but the mole fraction of the gas was reduced; after the temperature was lowered again to 500° C.-600° C., the remaining phosphorus gas condensed into a solid, and the pressure of the crystal growth unit 10-3 was lowered, so that the upper melt flowed into the crystal growth unit.

[0074] F. The temperature of a part of the upper part of the crystal growth unit 10-3 close to the capillary pore (10-2) was adjusted to be higher than the melting point of indium phosphide by 1062° C., and the temperature of the rest to be lower than the sublimation temperature of red phosphorus by 590° C.

[0075] The heating powers of the portion I of the crystal growth heating zone 1, the portion II of the crystal growth heating zone 2, the portion III of the crystal growth heating zone 3, and the portion IV of the crystal growth heating zone 4 were adjusted, so that the temperatures of the crystal growth unit 10-3, the crystal growth unit thermocouple 9-5, the crystal growth unit thermocouple 9-6 and the crystal growth unit thermocouple 9-7 were lowered to below 500° C., and the temperature of the crystal growth unit thermocouple 9-4 higher than 1062° C., as shown in FIG. 7.

[0076] The remaining phosphorus gas in the crystal growth unit 10-3 started to be converted into phosphorus solids. And then, the pressure in the crystal growth unit 10-3 was reduced, and the indium-phosphorus melt 24 dropped from the synthesis unit 10-1 into the crystal growth unit 10-3 through the capillary pores 10-2 due to the pressure difference, as shown in FIG. 5.

[0077] The indium-phosphorus melt 24 dropped into the boron oxide for liquid seed crystal protection 23 to rapidly solidify into solid indium phosphide 25, and finally all the melt in the synthesis unit 10-1 dropped into the crystal growth unit 10-3. When the temperatures of the crystal growth unit thermocouple 9-5, the crystal growth unit thermocouple 9-6 and the crystal growth unit thermocouple 9-7 were lower to below 500° C., the furnace body could be filled with inert gas, the pressure was increased by 0.2-2.0 MPa, the pressure difference between the crystal growth unit 10-3 and the synthesis unit 10-1 was further increased to ensure that the indium-phosphorus melt 24 could smoothly drop into the crystal growth unit 10-3.

[0078] In addition, an discharge unit could be further provided on the crystal growth unit 10-3 in the crucible to directly communicate with the exterior of the furnace body, and in this step, by discharging, the internal pressure of the growth unit was reduced, facilitating the indium-phosphorus melt 24 dropping into the crystal growth unit 10-3.

[0079] G. The temperature of the crystal growth unit 10-3 was adjusted to be higher than the melting point of indium phosphide, and the temperature distribution was controlled to carry out crystal growth.

[0080] The heating powers of the portion I of the crystal growth heating zone 1, the portion II of the crystal growth heating zone 2, the portion III of the crystal growth heating zone 3, and the portion IV of the crystal growth heating zone 4 were adjusted, so that the temperature above the seed crystal unit 10-4 was higher than the melting point of indium phosphide, and the solid indium phosphide 25 was melted into the indium-phosphorus melt 26, as shown in FIG. 8.

[0081] A temperature gradient from top to bottom was established, and then the temperature distribution was controlled to carry out VGF crystal growth. As shown in FIG. 9, the reference numeral 27 indicates the generated indium phosphide crystal.

Device and Method for Continuous VGF Crystal Growth through Reverse Injection Synthesis

Inventors

Cpc classification

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C30B27/00

CHEMISTRY; METALLURGY

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C30B11/08

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C30B29/40

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C30B11/007

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C30B11/001

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C30B11/006

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International classification

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C30B11/00

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C30B27/00

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C30B29/40

CHEMISTRY; METALLURGY

Abstract

Claims

Description