KR100416736B1 - Method for fabricating single crystal using vpe growth method - Google Patents

Abstract

PURPOSE: A method for fabricating a single crystal using a VPE(Vapor Phase Epitaxy) growth method is provided to minimize the generation of defects in a growing process by injecting gas into an inner part of a growth ampoule to form the flowing gas atmosphere. CONSTITUTION: A state of vacuum is formed in an inner part of a growth ampoule(202). The predetermined gas is injected into the inner part of the growth ampoule in order to form the predetermined pressure. The flowing gas atmosphere is maintained in the inner part of the growth ampoule. A surface of a seed is etched by performing a heat etching process under the flowing gas atmosphere. The growth ampoule is heated under the flowing gas atmosphere. The temperature of an upper side including a raw material vessel(204) is higher than the temperature of a lower side including the seed crystal by performing the heating process.

Description

Single Crystal Production Method by Vapor Crystal Growth Method

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single crystal production method by vapor phase crystal growth method, and more particularly, to a single crystal production method by vapor phase crystal growth method capable of obtaining ZnSe single crystals having reduced defects by preventing contamination in growth ampoules.

ZnSe single crystal is one of the materials attracting attention as substrate materials for blue light emitting diodes and blue semiconductor lasers. There are three typical methods for growing ZnSe single crystals.

The first method is a method of melting a raw material in an argon atmosphere of 30 atm and a temperature of 1650 to 1680 ° C. and slowly cooling the crucible to grow crystals from seed crystals located at the bottom of the crucible. However, this method has a disadvantage in that a large number of twins are generated during crystal cooling due to a phase transition in which the ZnSe crystal is changed from hexagonal to cubic at 1425 ° C.

The second method is the Recrystallization Traveling Heater Method, which treats ZnSe powder at high temperature and high pressure to produce a solid mass with a porosity of 90% or more, and increases the grain size in the solid phase by treating the solid mass at high temperature and high pressure again. It is a method of producing a single crystal on the principle of.

The third method is the vapor phase crystal growth method, in which ZnSe raw materials are placed in a growth ampoule and heated to a temperature of about 1150 ° C. to generate ZnSe vapor, and seed crystals are installed at a temperature range of about 1050 ° C. in the same growth ampoule. ZnSe vapor is condensed on the seed crystal so that the crystal is grown, and the ZnSe single crystal is grown under 1 atmosphere under an atmosphere of hydrogen, helium or argon at a temperature of about 1150 ° C. This method is divided into Seeded Physical Vapor Transport (SPVT) method and Seeded Chemical Vapor Transport (SCVT) method depending on the type of gas in the growth ampoule.

1 is a cross-sectional view illustrating a single crystal manufacturing apparatus using a closed growth ampoule, and a ZnSe single crystal manufacturing method by a conventional vapor phase crystal growth method using a closed growth ampoule is as follows.

The heating furnace 1 is surrounded by the growth amplifier 2 sealed with the upper end and the lower end, and seed crystals 5 are installed inside the growth amplifier 2. On the upper side of the growth ampoule 2, a raw material container 4 is spaced apart from the seed crystals 5 at regular intervals and filled with polycrystalline ZnSe 3 raw materials.

In such a structure, first, the growth ampoules 2 are filled with one of hydrogen, helium and argon so that the gas atmosphere is maintained such that the pressure inside the growth ampoules 2 is 1 atm. Next, the growth amplifier 2 is heated by the heating furnace 1. At this time, the upper side of the inside of the growth amplifier 2 containing the raw material container 4 is heated to be about 1150 ° C., and the lower side of the inside of the growth amplifier 2 is about 1050 on the upper surface of the seed crystal 5. Heated to ° C. In this case, the polycrystalline ZnSe (3) raw material charged into the raw material container 4 is sublimed into steam. This vapor exits the raw material container 4 and flows up to the seed crystals 5, which are then condensed on the seed crystals 5 and slowly growing ZnSe single crystals on the seed crystals 5. When the growth of the ZnSe single crystal is completed as described above, the heating furnace 1 may be cooled to obtain a ZnSe single crystal from the growth amplifier 2.

However, when the closed growth ampoule 2 having the above structure is used, the closed growth ampoule 2 may be used only once, and thus, the manufacturing cost of the crystal is increased. In addition, the closed growth amplifier 2 is made by connecting the upper side and the lower side. When welding the upper and lower connecting portions 8a of the upper and lower growth amplifiers 2, SiO and carbon, etc. 2) It is introduced into the inside, the gas injection portion (8b) of the growth ampoules (2) to inject gas into the growth ampoules (2) and then weld the gas injection portion (8b) to seal the gas injection portion (8b) In this case, SiO and carbon are introduced into the growth ampoules (2), and SiO and carbon act as contaminants to the polycrystalline ZnSe (3) raw material and the grown ZnSe single crystal. They cause defects in the ZnSe single crystal, and the band gap of the ZnSe single crystal is changed by these unwanted impurities. This result is a disadvantage that makes the application of devices such as semiconductor lasers difficult.

FIG. 2 is a cross-sectional view illustrating a single crystal manufacturing apparatus using an open growth ampoule. Referring to the drawings, a ZnSe single crystal manufacturing method according to a conventional vapor phase crystal growth method using an open growth ampoule is as follows.

The growth amplifier 202, which is sealed at the upper end and opened at the lower end, has a cavity formed therein, and a raw material container 204 in which the polycrystalline ZnSe 203 material is charged is mounted at the upper end of the growth amplifier 202.

Meanwhile, one end of the support 207 is attached to the growth chamber 209, and the bottom surface of the quartz rod 206 is coupled to the lower end of the support 207. A seed crystal 205 is provided on the top surface of the quartz rod 206. Here, the air discharge portion 211 is coupled to the outer surface of the growth chamber 209, and the gas injection portion 212 is coupled to the other outer surface of the growth chamber 209.

Next, the structure consisting of the seed crystal 205, the quartz rod 206, and the support 207 is covered with the growth amplifier 202 in which the raw material container 204 is mounted so that the outer surface of the lower end of the growth amplifier 202 is covered with the top. Is coupled to the upper inner surface of the open growth chamber 209. At this time, the outer surface of the lower end of the growth amplifier 202 and the upper inner surface of the growth chamber 209 are coupled to the O-ring (210) to shield the outside.

In addition, the heating furnace 201 is installed outside the growth amplifier 202 so that the growth amplifier 202 is heated.

Referring to the operation in this structure, the growth amplifier 202 is first heated by the heating furnace 201. At this time, the upper side of the growth amplifier 202 including the raw material container 204 is heated to about 1150 ° C., and the lower side of the growth amplifier 202 is about 1050 on the upper surface of the seed crystal 205. Heat to ℃. The inside of the growth amplifier 202 coupled with the growth chamber 209 by the air discharge unit 211 is approximately Torr is vacuumed and one of hydrogen, helium, and argon is injected into the growth amplifier 202 by the gas injection unit 212 to maintain a gas atmosphere such that the pressure inside the growth amplifier 202 is 1 atm. .

In this case, the polycrystalline ZnSe 203 raw material charged into the raw material container 204 is sublimed into vapor. This vapor exits the raw material container 204 and flies to the seed crystal 205, which is condensed on the seed crystal 205 and gradually grows a ZnSe single crystal on the seed crystal 205. When the growth of the ZnSe single crystal is completed, the heating furnace 201 may be cooled to obtain a ZnSe single crystal from the growth amplifier 202.

However, since the ZnSe single crystal manufacturing method using the vapor phase crystal growth method has a ZnSe single crystal growth period of about 1 to 4 weeks, external air is introduced from the coupling region of the open growth amplifier 202 and the growth chamber 209 to allow the growth amplifier ( The gas purity in 202 is lowered. This also causes defects in the ZnSe single crystal and makes it difficult to apply devices such as semiconductor lasers by changing the band gap of the crystal due to unwanted impurities.

The present invention was created to improve the above problems, by injecting a constant pressure gas into the growth amplifier by the gas injection unit to maintain the gas atmosphere flowing inside the growth amplifier, it is possible to reduce the defects in the ZnSe single crystal It is an object of the present invention to provide a single crystal manufacturing method by vapor phase crystal growth method.

1 is a cross-sectional view showing a single crystal manufacturing apparatus using a closed growth ampoule.

Fig. 2 is a sectional view showing a single crystal manufacturing apparatus in which an open growth amplifier is used.

3 is a schematic diagram illustrating a growth chamber coupled to an open growth amplifier.

Figure 4 is a flow chart showing a single crystal manufacturing method by the vapor phase crystal growth method according to the present invention.

<Description of the symbols for the main parts of the drawings>

201. Heating furnace 202. Growth ampoule

204. Raw material container 205. Seed determination

209. growth chamber

210..O-ring 211.Air exhaust

212.Gas injection 213.Turbo pump

214 diaphragm pump

218..Mass Flow Controller 220..bombe

225..baratron gauge

ZnSe single crystal production method of the present invention to achieve the above object, the gas injection step of making the interior of the growth ampoules in a vacuum state, and a predetermined gas is injected into the growth ampoules at a predetermined pressure; A gas atmosphere maintaining step of maintaining the gas atmosphere flowing in the growth ampoule; A thermal etching step of thermally etching the surface of the seed crystal while maintaining the flowing gas atmosphere; And heating the growth ampoule such that the temperature of the upper part of the seed crystal including the raw material container is higher than the temperature of the lower part of the seed crystal including the seed crystal while maintaining the flowing gas atmosphere. It features.

According to the invention, the gas is preferably any one of hydrogen, helium and argon.

Hereinafter, a ZnSe single crystal manufacturing method according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. 3 is a schematic diagram illustrating a growth chamber coupled to an open growth amplifier.

The structure of the open growth amplifier of FIG. 2 used in the present invention has been described above, and the structure of the growth chamber coupled to the lower end of the open growth amplifier is described below with reference to FIG.

As shown, the growth chamber coupled to the open growth amplifier has a first outer surface 226a in four directions perpendicular to each other among the outer surfaces of the growth chamber 209 in order to discharge the air in the growth amplifier 202 into a vacuum state. ), The first outer valve 215 and the turbo pump 213 on the first outer surface 226a of the second outer surface 226b, the third outer surface 226c, and the fourth outer surface 226d. ), The first gate valve 215 of the air exhaust portion 211, in which the TC gauge (222) and the diaphragm pump (214) for measuring low vacuum degree are sequentially coupled, respectively. Combined.

In addition, the TC gauge 223 of the gas injection unit 212 is coupled to the second outer surface 226b in order to maintain the inside of the growth amplifier 202 as a gas atmosphere. Here, the gas injection unit 212 is coupled to the TC gauge 223 and the second gate valve 216 connected in series, and the second gate valve 216 is connected to the first valve 217a and the second valve 217b. ) And the third valve 217c are connected in parallel to each other, and the first valve 217a, the second valve 217b, and the third valve 217c are respectively connected to the first MFC (Mass Flow Controller) 218a and the third valve. The 2MFCs 218b and the third MFCs 218c are connected in series and coupled, and the fourth and fifth valves 219a and 219b are respectively connected to the first MFC 218a, the second MFC 218b, and the third MFC 218c. And a sixth valve 219c connected in series, and coupled to the fourth valve 219a, the fifth valve 219b, and the sixth valve 219c, respectively, in which a first bombe 220a into which argon gas is charged. ), The second cylinder 220b loaded with helium gas and the third cylinder 220c loaded with hydrogen gas are connected in series to each other.

An ion gauge 224 is coupled to the third outer surface 226c, and a seventh valve 221 and a baratron gauge 225 are sequentially connected to the fourth outer surface 226d.

Hereinafter, a single crystal manufacturing method by the vapor phase crystal growth method according to the present invention will be described with reference to FIG. 4.

First, the diaphragm pump 214 is used to weaken the inside of the growth amplifier 202. Evacuate the air to Torr and vacuum it. At this time, the TC gauge 222 is to monitor the low vacuum level, and the vacuum gauge in the growth amplifier 202 by the diaphragm pump 214 is monitored by the TC gauge 223 to adjust the vacuum degree in the growth amplifier 202 ( 401).

Next, using the turbo pump 213 while operating the diaphragm pump 214 to remove impurities in the growth chamber 209. The air is discharged to Torr to vacuum the inside of the growth amplifier 202. At this time, the third ion gauge 224 is to monitor the high vacuum degree, and the vacuum degree in the growth amplifier 202 by the turbo pump 213 is monitored by the third ion gauge 224 to monitor the vacuum degree in the growth amplifier 202. Adjust (402).

The diaphragm pump 214 and the turbo pump 213 are then turned off (403).

Since the diaphragm pump 214 continues to operate in this state, the desired gas is continuously injected and flowed. The baratron gauge 225 then monitors the pressure in the growth chamber 209 and selects one of the MFC1 219a, MFC2 219b and MFC3 219c and transmits it as an electrical signal to the MFC 219a. , 219b and 219c are operated to inject the gas charged into the cylinders 220a, 220b and 220c into the growth chamber 209 such that the pressure in the growth chamber 209 is maintained at 1 atmosphere. In this way, a gas atmosphere of 7N or higher gas purity is maintained in the growth amplifier 202 without flowing gas by the gas injection unit 212. The first valve 217a to the sixth valve 219c control the flow rate of the gas, and the seventh valve 221 adjusts the flow of the gas measured by the baratron gauge 225. (404).

In this state, the growth amplifier 202 is heated by the heating furnace 201. At this time, the upper side of the growth amplifier 202 including the raw material container 204 is heated to about 1150 ° C., and the lower side of the growth amplifier 202 is about 1050 on the upper surface of the seed crystal 205. Heat to 캜 (405).

In this way, the polycrystalline ZnSe 203 raw material charged into the raw material container 204 is sublimed into vapor. This vapor exits the raw material container 204 and flies to the seed crystal 205, which is condensed on the seed crystal 205 so that the ZnSe single crystal is gradually deposited on the seed crystal 205 at a crystal growth rate of 100 m / hr or less. Is grown. In this case, since the gas atmosphere is maintained in the growth amplifier 202 without gas stagnation by the gas injection unit 212, a gas atmosphere with a purity of 7N or higher is maintained, thereby minimizing defects generated during the growth of the ZnSe single crystal and mixing impurities in the ZnSe single crystal. Therefore, a ZnSe single crystal having a constant band gap can be obtained. In this manner, after 8 days of crystal growth period, ZnSe single crystals are completely grown, and ZnSe single crystals are gradually cooled at a cooling rate of 30 ° C / hr to obtain ZnSe single crystals from the growth amplifier 202 (406).

In addition, since the open growth ampoule 202 having the above structure is used in the manufacturing method of the present invention, the contaminant remains in the growth ampoule 202 by the conventional manufacturing method. The growth amplifier 202 has the advantage that it can be used multiple times.

As described above, the single crystal manufacturing method by the vapor phase crystal growth method according to the present invention is generated during the growth of the ZnSe single crystal and the impurities mixed into the ZnSe single crystal by maintaining the gas atmosphere inside the growth ampoule by injecting gas into the growth ampoule. There is an effect to minimize the defects.

Claims (2)

A gas injection step of making the inside of the growth amplifier into a vacuum state and injecting a predetermined gas into the growth ampoules at a predetermined pressure; A gas atmosphere maintaining step of maintaining the gas atmosphere flowing in the growth ampoule; A thermal etching step of thermally etching the surface of the seed crystal while maintaining the flowing gas atmosphere; And And heating the growth ampoule such that the temperature of the upper part of the seed crystal including the raw material container is higher than the temperature of the lower part of the seed crystal including the seed crystal while maintaining the flowing gas atmosphere. A single crystal production method by vapor phase crystal growth method. The method of claim 1, wherein the gas is one of hydrogen, helium, and argon.