JPH06112130A - Crystal growth device - Google Patents

Abstract

PURPOSE:To grow a thin-film while being controlled at a monoatomic layer level. CONSTITUTION:A crystal growth device is composed of an airtight vessel 6, in which a substrate crystal 13 mounted into a vacuum vessel 2 is housed, a gas exhaust valve from the airtight vessel into the vacuum vessel, a control valve 9 for the quantity of a gas leaked from the airtight vessel, raw material gas introducing pipings 16, 21 into the airtight vessel, a heating apparatus 14 for the substrate crystal installed into the airtight vessel, an exhauster 3 evacuating the inside of the vacuum vessel to a high degree, and a raw material gas supply controller consisting of mass flow controllers 18, 23 supplying the raw material gas at predetermined flow rate and time and valve groups 17, 22. The substrate crystal 13 is irradiated alternately with two kinds or more of raw material gases, the gas exhaust valve set up into the airtight vessel is driven while being synchronized with the changeover of the gases and the crystal can be grown. Electron-ray incident and outgoing windows are further fitted to the airtight vessel in the crystal growth device having the same constitution, and the crystal can be grown by the same operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crystal growth apparatus for thin film crystals used in the manufacture of electronic equipment, and more particularly to a crystal growth apparatus capable of growing a thin film while controlling it at the level of one atomic layer.

[0002]

2. Description of the Related Art Chemical beam epitaxy (CBE) has hitherto been used as a method for growing a thin film crystal using gas as a raw material.
Law), MOMBE method, etc. are known. These methods use a device as shown in FIG. 2 to manufacture a thin film having a thickness of one atomic layer to about 10 μm on a substrate crystal. In FIG. 2, the vacuum container lid 29 and the vacuum container body 30 are shown.
The growth chamber composed of
It is kept in a high vacuum state of about 1E-7 Pascal. The substrate crystal 35 is fixed to the substrate crystal holding plate 32 with the growth surface facing downward, and is heated by the substrate heater 34 from the back surface. The source gas 39 is sprayed onto the substrate crystal through the mass flow controller 38, the valve 37 and the nozzle 36. Similarly, the second
The raw material gas 43 is a mass flow controller 42, a valve 41,
It is adapted to be ejected onto the surface of the substrate through the nozzle 40. Such a source gas line is usually prepared for each type of gas, and it is necessary to use, for example, two systems when growing only GaAs and three systems when doping GaAs with one type of impurity.

Mass flow controllers 38, 42 and valve 3
7 and 41 are connected to a computer and operate according to a program created in advance. For example, when epitaxially growing a GaAs crystal for each atomic layer, as shown in FIG. 3, arsine (AsH ₃ ) and trimethylgallium (TMG), which are raw materials, are used.
a) and are sprayed alternately on the substrate crystal. That is, first, arsine is injected at a flow rate of L ₁ for τ ₁ second, then the inflow of gas is stopped for τ ₂ seconds, and the source gas is removed from the periphery of the substrate. After that, trimethylgallium, which is a Ga source, is injected at a flow rate of L ₂ for τ ₃ seconds to grow a GaAs 1 layer. By repeating this operation, controlled crystal growth can be performed for each atomic layer. Providing the waiting time τ ₂ has the effect of preventing two kinds of gases from mixing with each other, as described in, for example, Japanese Patent Application Laid-Open No. 61-34927, and controls one layer at a time. However, it is a necessary process for growing GaAs.

[0004]

When the gas as shown in FIG. 3 is supplied by using the above conventional apparatus, the entire crystal growth container is filled with the gas, and the raw material gas is steeped on the substrate crystal surface. It becomes difficult to switch to. That is, for example, when a gas is supplied by the procedure shown in FIG. 3 for growing GaAs, the partial pressure of the source gas near the substrate crystal is as shown in FIG. , There will be a delay of a certain time. FIG. 4 schematically shows how the partial pressure in the crystal growth chamber changes after supplying arsine for τ ₄ seconds (τ ₄ = 5 to 10 seconds). That is, τ ₇ seconds (τ ₇ = 20 to 60) even after the supply of arsine is stopped.
Second) and arsine remains in the crystal growth container for a long time, affecting the next supply of trimethylgallium. Further, trimethylgallium itself causes a residual phenomenon similar to that of arsine, resulting in mixing of arsine and trimethylgallium, which makes it difficult to achieve crystal growth controlled at the level of one atomic layer.

Further, in the conventional device, even when a heterojunction is formed in which different types of crystal layers are continuously grown as shown in FIG.
There is a problem that it cannot be made steep at the atomic layer level. Fig. 5 shows GaAs substrate crystal 48, AlGaAs epitaxial layers 49, 5
1. A diagram showing a heterojunction structure composed of a GaAs epitaxial layer 50. Crystal growth was carried out in the order of 49, 50 and 51. In this case, each interface between GaAs and AlGaAs is a hetero interface, but a problem occurs especially at the transition from 49 to 50. That is, A used for the growth of AlGaAs 49
l The raw material remains in the crystal growth chamber and is mixed in during the growth of GaAs 50, so that the hetero interface between 49 and 50 cannot be made sharp at the level of one atomic layer. For this reason,
With the conventional equipment, the growth rate of about 1 μm / hour is usually set to 0.1 μm / hour.
There were restrictions such as extremely small values below the hour.

As described above, the problem with the conventional apparatus is that the raw material gas remains in the growth chamber having a large capacity for a long time.

An object of the present invention is to solve the problems of the prior art and to provide a crystal growth apparatus capable of growing a thin film while controlling it at the level of one atomic layer.

[0008]

The above object is to provide an airtight container for storing substrate crystals installed in a vacuum container, and to discharge gas from the airtight container provided in the airtight container into the vacuum container. A gas exhaust valve, a control valve for finely adjusting the amount of gas leaked from the airtight container, a pipe for introducing a raw material gas into the airtight container, and a substrate crystal stored in the airtight container. A heating device for heating with radiant heat, an exhaust device for exhausting the vacuum container to a high vacuum, a raw material gas supply control device including a mass flow controller and a valve group for supplying a raw material gas at a predetermined flow rate and time. A crystal growth apparatus comprising: a substrate crystal, which is alternately irradiated with two or more kinds of source gases, and a gas exhaust valve provided in the airtight container is driven in synchronization with switching of the source gases. crystal A crystal growth apparatus characterized by comprising a structure capable of performing lengthening, or an airtight container for storing a substrate crystal installed in a vacuum container, and an electron beam provided in the airtight container Entry / exit window, a gas exhaust valve for discharging gas from the airtight container into the vacuum container, a control valve for finely adjusting the amount of gas leaked from the airtight container, and the inside of the airtight container A pipe for introducing the raw material gas, a heating device for heating the substrate crystal stored in the airtight container with radiant heat, an exhaust device for evacuating the vacuum container to a high vacuum, and a predetermined raw material gas A crystal growth apparatus composed of a mass flow controller that supplies at different flow rates and times and a source gas supply control device that includes a valve group, the substrate crystal being alternately irradiated with two or more types of source gas, and the source material described above. In synchronization with the switching of the scan can be accomplished by a crystal growth apparatus characterized by comprising a structure made it possible to carry out the crystal growth by driving a gas discharge valve provided in the airtight container.

[0009]

In the above apparatus of the present invention, the raw material gas is first introduced into a small reaction chamber provided in a vacuum container, a predetermined amount of the raw material is irradiated on the substrate crystal, and then the raw material gas is shut off. The gas exhaust valve provided in the reaction chamber is operated to discharge the excess gas into the vacuum container. By using such a mechanism, the entire vacuum container is not constantly exposed to the raw material gas, and the surface area of the part that is constantly exposed to the raw material gas can be reduced by one digit or more compared to the conventional device. , The raw material gas adsorbed on the inner wall of the outer vacuum vessel can be efficiently discharged while the crystal growth using the next gas is proceeding in the reaction chamber, so that unnecessary raw material gas near the substrate crystal is Residue can be greatly reduced. That is, by using the device of the present invention, the time constants τ ₇ and τ ₈ of gas breakage due to the influence of the residual raw material gas in the conventional device in the temporal change of the raw material partial pressure on the substrate crystal surface shown in FIG. Compared with this, the effect that it can be reduced by one digit or more is obtained.

Further, a small window for electron beam entrance / exit for RHEED, which is often used for observing a crystal growth state, is provided in the reaction chamber, and a mechanism capable of opening / closing control from the outside is provided, so that a vacuum container can be opened from the reaction chamber. It is possible to combine the function of the gas exhaust valve. By opening the small window for electron beam entrance / exit at the same time as shutting off the raw material gas, there is an advantage that gas discharge and preparation for growth state observation can be performed simultaneously.

[0011]

EXAMPLES The crystal growth apparatus of the present invention will be specifically described below with reference to examples.

FIG. 1 is a cross-sectional view showing the structure of an embodiment of the crystal growth apparatus of the present invention, showing that the apparatus mainly comprises a vacuum container lid 1, a vacuum container body 2 and a vacuum pump 3.
The vacuum chamber is provided with a reaction chamber for crystal growth.
The reaction chamber comprises a reaction chamber lid 4 made of molybdenum and a reaction chamber body 6 made of stainless steel, and each is independently supported by a reaction chamber support column 5 and a reaction chamber body support rod 7. The reaction chamber body 6 is fixed to the up-and-down mechanism 8 and has a structure that can be vertically moved from the outside. As shown by 12, the lid 4 and the main body 6 have a rubbing structure, and can maintain airtightness. Further, the reaction chamber main body 6 is provided with a pressure adjusting valve 9. The valve 9 is rotated by a drive rod 10 as shown by an arrow 11 to adjust the opening area from the outside of the vacuum container so that the pressure in the reaction chamber can be controlled.
In the case of the present embodiment, the reaction chamber main body 6 is lowered and the state in which it is rubbed with the lid 4 is opened, whereby the airtightness of the reaction chamber is broken and the source gas in the reaction chamber is discharged into the vacuum container. That is, the up-down mechanisms 7 and 8 and the rubbing 12 form a gas exhaust valve. The GaAs substrate crystal 13 is attached to the center of the lid 4 with the growth surface facing downward, and is heated by the heater 14 arranged on the back surface of the lid 4.

A nozzle 15 for injecting arsine, which is a raw material of As, onto the substrate crystal 13 is fixed in the reaction chamber 6,
The nozzle 15 is connected to an arsine piping system including a flexible pipe 16, a valve 17, and a mass flow controller 18. A heater 19 for thermally decomposing arsine is provided in the arsine piping. Further, a trimethylgallium piping system including a nozzle 20, a flexible pipe 21, a valve 22, and a mass flow controller 23 for supplying trimethylgallium as a Ga raw material is installed almost symmetrically to the arsine piping system. The piping system is heated by the heater 24. Further, an electron gun 25 for observing a crystal growth state is installed in the vacuum container 2, and an electron beam emitted from the electron gun 25.
26 is a screen that is irradiated on the growth surface of the GaAs substrate 13 and the backscattered electron beam 27 diffracted on the surface is installed in the vacuum chamber 2.
The diffraction pattern is shown above.

Next, the operation of the apparatus when forming a thin film will be described. First, after placing the GaAs substrate crystal 13 on the reaction chamber lid 4, the pressure of the vacuum container composed of the lid 1 and the main body 2 is set to 1
Vacuuming is performed by the vacuum pump 3 until a vacuum state of E-6 Pascal or less is reached. At this time, the reaction chamber body 6 is lowered to a position where it does not rub against the lid 4, and the exhaust valve of the reaction chamber is kept open. Vacuum container pressure is 1E-6
When the temperature falls below Pascal, the up-and-down mechanisms 7 and 8 are operated to raise the reaction chamber main body 6 so that the main body 6 and the lid 4 are moved as shown in FIG.
Make sure that they are rubbed together as shown in 12 above. That is, the gas exhaust valve of the reaction chamber is closed. Also,
The pressure of the reaction chamber when flowing the source gas is 1E-2 to 1E-
The pressure adjusting valve 9 is adjusted to a predetermined opening so that the pressure is about 1 pascal. Next, the heater 14 is energized to move the substrate 13 to 60
Heat to 0-700 ° C. During the heating, arsine is introduced into the vacuum container through the mass flow controller 18 and the valve 17 from the time when the substrate crystal temperature monitored by a thermocouple or the like becomes 400 ° C. or higher in order to prevent As escape from the GaAs substrate. Arsine is heated to about 800 ° C. by the heater 19 on the way and is sprayed from the nozzle 15 onto the substrate while thermally decomposing. While flowing arsine, the substrate crystal is heated at 600 to 700 ° C. for about 10 minutes to remove the oxide on the substrate surface. After the crystal surface of the substrate is sufficiently cleaned, the substrate temperature is lowered to 400 to 600 ° C. After the substrate temperature stabilizes at a predetermined temperature, the raw materials are alternately introduced in the procedure shown in FIG. That is, arsine is caused to flow at a flow rate L ₁ for τ ₁ second, and after τ ₂ seconds have elapsed, trimethylgallium is caused to flow at a flow rate L ₂ for τ ₃ seconds. At this time, the reaction chamber main body 6 is lowered downward by using the elevating mechanisms 7 and 8 for τ ₂ seconds in which neither arsine nor trimethylgallium flows, so that arsine or trimethylgallium filled in the reaction chamber is rapidly discharged. That is, the gas exhaust valve of the reaction chamber is opened. The flow rate L ₁ and supply time τ ₁ are As
The substrate surface is determined to have a sufficient amount to cover one atomic layer, and the flow rate L ₂ and the supply time τ ₃ are determined so that the Ga raw material has a sufficient amount to cover the GaAs substrate surface with one atomic layer. By repeating this procedure, a thin film is formed on the surface of the substrate in atomic layer units.

When the gas exhaust valve of the reaction chamber is opened for τ ₂ seconds, a beam path between the electron beam 26 from the electron gun 25 and the reflected electron beam 27 diffracted by the substrate is secured, and the RHEED method is used. It is possible to observe the growth state.

Next, an example of crystal growth conditions using the apparatus of the present invention will be shown. First, the pressure control valve 9 is adjusted to a predetermined opening so that the pressure in the reaction chamber when the raw material gas flows is 5E-2 Pascal. Next, the heater 14 is energized to heat the substrate crystal 13 to 650 ° C. During heating, when the temperature of the substrate crystal monitored by a thermocouple etc. reached 400 ℃ or higher, G
arsine 5cc / min to prevent As leakage from the aAs substrate
Is introduced into the vacuum container through the mass flow controller 18 and the valve 17. Arsine is heated to 810 ° C. by the heater 19 on the way and is sprayed from the nozzle 15 onto the substrate while thermally decomposing. While flowing arsine, the substrate crystal is heated at 600 to 700 ° C for 10 minutes to remove oxides on the substrate surface for cleaning. After that, the substrate temperature is lowered to 450 ° C. Substrate temperature is 450
After stabilizing at 0 ° C. (after about 5 minutes), the raw materials are alternately introduced according to the procedure shown in FIG. That is, arsine is flown for 2 seconds at a flow rate of 2 cc / min, and after a further 2 seconds, trimethylgallium is flowed for 3 seconds at a flow rate of 4 cc / min. At this time, during the middle 2 seconds in which neither arsine nor trimethylgallium is allowed to flow, the reaction chamber 6 is lowered downward by using the elevating mechanisms 7 and 8 so that the arsine or trimethylgallium filled in the reaction chamber is rapidly discharged. . That is, the gas exhaust valve of the reaction chamber is opened. Arsine supply, gas exhaust valve open, gas exhaust valve closed,
By repeating the growth with supplying trimethylgallium, opening the gas exhaust valve, and closing the gas exhaust valve as one cycle, a thin film can be formed on the surface of the substrate at a rate of one atomic layer per cycle.

[0017]

As described above, the crystal growth apparatus having the structure of the present invention solves the problems of the prior art, and grows a thin film while controlling it at the level of one atomic layer. It was possible to provide a crystal growth apparatus capable of performing the above. That is, by using the apparatus having the configuration of the present invention, in high-vacuum crystal growth using a gas raw material, it is possible to reduce the gas residue in the vicinity of the substrate crystal after shutting off the raw material gas, so that crystal growth in atomic layer units can be achieved. It has the effect of making it easier. Further, in the growth of the heterojunction structure, a steep hetero interface can be formed at the level of one atomic layer without lowering the crystal growth rate.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of an embodiment of a crystal growth apparatus of the present invention.

FIG. 2 is a cross-sectional view showing the structure of a conventional chemical beam epitaxy (CBE) device.

FIG. 3 is a diagram showing a gas introduction procedure for growing GaAs in atomic layer units.

FIG. 4 is a diagram showing a time change of a source gas partial pressure in the vicinity of a substrate crystal when a gas is introduced by the procedure shown in FIG. 3 to grow GaAs in a conventional apparatus.

FIG. 5 is a cross-sectional view showing a GaAs / AlGaAs heterojunction structure.

[Explanation of symbols]

1 ... vacuum container lid, 2 ... vacuum container body, 3 ... vacuum pump,
4 ... Reaction chamber lid, 5 ... Reaction chamber lid support column, 6 ... Reaction chamber body,
7 ... Reaction chamber body support rod, 8 ... Reaction chamber body up / down mechanism, 9 ...
Reaction chamber pressure adjusting valve, 10 ... Reaction chamber pressure adjusting valve opening / closing mechanism, 11
… Reaction chamber pressure control valve opening / closing operation, 12… Rubbing part, 13…
Substrate crystal, 14 ... Substrate heating heater, 15 ... Nozzle, 16 ... Gas air supply pipe, 17 ... Valve, 18 ... Mass flow controller, 19 ... Raw gas pyrolysis heater, 20 ... Nozzle, 21 ... Gas air supply pipe , 22 ... Valve, 23 ... Mass flow controller, 24 ... Pipe heat insulation heater, 25 ... Electron gun, 26 ... Electron beam, 27 ... Diffraction electron beam, 28 ... Electron beam observation screen, 29
… Vacuum container lid, 30… Vacuum container body, 31… Vacuum pump, 32
... Substrate crystal holding plate, 33 ... Substrate crystal holding plate support column, 34 ... Substrate heating heater, 35 ... Substrate crystal, 36 ... Nozzle, 37 ... Valve, 38 ... Mass flow controller, 39 ... Raw material gas, 40 ...
Nozzle, 41 ... Valve, 42 ... Mass flow controller, 43
Material gas 44 Electron gun 45 Electron beam 46 Diffraction electron beam 47 Electron beam observation screen 48 GaAs substrate crystal 49 AlGaAs epitaxial layer 50 50 GaAs epitaxial layer 51 AlGaAs epitaxial layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinichiro Takatani 1-280, Higashi Koikeku, Kokubunji, Tokyo Inside Central Research Laboratory, Hitachi, Ltd. (72) Toshimitsu Miyata 1-280, Higashi Koikeku, Kokubunji, Tokyo Hitachi, Ltd. Central Research Laboratory (72) Inventor Kenji Okumura 2-6-40 Chikko Shinmachi, Sakai City, Osaka Daido Acid Co., Ltd. Sakai Plant (72) Inori Noriori Omori 2-640 Tsukiko Shinmachi, Sakai City, Osaka Daido Acid Sato Co., Ltd. Sakai factory

Claims (3)

[Claims] 1. An airtight container for storing a substrate crystal installed in a vacuum container, and a gas exhaust valve provided in the airtight container for exhausting gas from the airtight container into the vacuum container.
A control valve for finely adjusting the leak amount of gas from the airtight container, a pipe for introducing a raw material gas into the airtight container, and a substrate crystal stored in the airtight container for heating with radiant heat Crystal growth composed of a heating device, an exhaust device for evacuating the vacuum container to a high vacuum, and a source gas supply control device including a mass flow controller and a valve group for supplying a source gas at a predetermined flow rate and time. An apparatus for alternately irradiating two or more kinds of source gases on a substrate crystal, and driving a gas exhaust valve provided in the hermetic container in synchronization with the switching of the source gases to perform crystal growth. A crystal growth apparatus having a structure that enables it. 2. An airtight container for storing a substrate crystal set in a vacuum container, an electron beam entrance / exit window provided in the airtight container, and a gas for discharging from the airtight container into the vacuum container. A gas exhaust valve, a control valve for finely adjusting the amount of gas leaked from the airtight container, a pipe for introducing a raw material gas into the airtight container, and a substrate crystal stored in the airtight container. A heating device for heating with radiant heat, an exhaust device for exhausting the vacuum container to a high vacuum, a raw material gas supply control device including a mass flow controller and a valve group for supplying a raw material gas at a predetermined flow rate and time. A crystal growth apparatus comprising: a substrate crystal, which is alternately irradiated with two or more kinds of source gases, and a gas exhaust valve provided in the airtight container is driven in synchronization with switching of the source gases. Crystal growth Crystal growing apparatus characterized by having the structure that enables it. 3. The crystal growth apparatus according to claim 2, wherein the electron beam entrance / exit window is opened / closed in synchronization with the driving of the gas exhaust valve.