JPH02221191A - Device for growing crystal by using gaseous source - Google Patents

Abstract

PURPOSE:To decrease the problems that the residual gases in the device give on a crystal when the gaseous raw material of a certain component is shut off by specifying the constitution of a gas piping and gas supply cell which supply the gaseous raw materials to a crystal growth chamber. CONSTITUTION:The crystal growth chamber 1 is a hermetic vessel in which a substrate holder 3 to support a substrate 2 is housed and which is connected to a 1st evacuating system 4. The gas supply cell 5 is disposed to face the substrate 2 in the growth chamber 1. While the cell 5 is connected to a gas source 7 by a gas introducing path 8 having a 1st valve 6, the cell 5 is connected to a 2nd evacuating system 10 by a gas discharge path 11 having a 2nd valve 9. The gases remaining in the cell 5 side part are discharged from the valve 6 of the cell and the introducing path 8 by opening the valve 9 at the time of closing the valve 6. The discharge of the residual gases is, therefore, speeded up and the gaseous molecules flowing toward the substrate 2 from the cell 5 outlet are decreased and, therefore, the boundary having a sharp distribution is obtd.

Description

[Detailed Description of the Invention] Summary] Regarding a gas source crystal growth apparatus in which the configuration of the gas piping and gas supply cell for supplying raw material gas to the crystal growth chamber has been newly improved, when the raw material gas of a certain component is shut off. The purpose of the present invention is to provide a gas source crystal growth apparatus that can reduce problems caused by residual gas in the crystal growth apparatus to crystal growth, and in a gas source crystal growth apparatus for growing crystals from a gas source in a low pressure atmosphere. In order to grow crystals on a substrate in a low-pressure atmosphere by being connected to a first vacuum evacuation system, there is an airtight crystal growth chamber that accommodates a substrate holder on which the substrate is placed, and a crystal growth chamber that supplies raw material gas for crystal growth to the substrate. a gas supply cell disposed within the crystal growth chamber for supplying to a holder; and a first pulp provided with and connected to the gas supply cell for controllably connecting the gas supply cell to a gas source. a gas inlet passage connected to the gas supply cell, and a gas exhaust passage provided with a second pulp and connected to the gas supply cell for controllably connecting the gas supply cell to a second evacuation system. .

[Industrial Field of Application] The present invention relates to a gas source crystal growth apparatus, and more particularly to a gas source crystal growth apparatus in which the configurations of gas piping and gas supply cells for supplying source gas to a crystal growth chamber are newly improved.

An epitaxial crystal growth method in which a semiconductor film is epitaxially grown along a crystal substrate is a basic technology for semiconductor manufacturing, and one of them is a gas source crystal growth method in which a crystal is grown from a gas source in a low-pressure atmosphere. Gas source molecular beam epitaxy has recently been developed as a promising technology.

In this gas source molecular beam epitaxy, a compound gas is introduced into an ultra-high vacuum crystal growth chamber to form a crystal growth layer. However, it is difficult to accurately control the composition and thickness of the grown layer by controlling the gas flow.

In particular, when forming an interface structure such as a Peter junction structure or a pn junction structure, a steep compositional change is required.

[Prior Art] A gas source molecular beam epitaxy method uses a gas source instead of a solid source such as a metal in the conventional molecular beam epitaxy (MBE) method.

For example, when growing a gallium arsenide (GaAs) layer or an aluminum gallium arsenide (AIGaAS) layer, triethyl gallium (TEG: Ga(C
2H5) 3), triethylaluminum (TEA
; An organometallic gas such as At (C2H5>3) is used, and a hydride gas such as arsine (ASH3) is used as the group V element material.

This gas source molecular beam crystal growth method has advantages over the conventional MBE method, such as being able to reduce surface defects and easily achieving a high growth rate.

Furthermore, the source can be replaced without breaking the clean ultra-high vacuum atmosphere inside the growth container, which is said to have a great advantage in industrial production.

FIGS. 2(A), 2(B), and 2(C) show a conventional crystal growth apparatus for performing the gas source molecular beam crystal growth. In FIG. 2 (A) showing the entire crystal growth apparatus, reference number 5
1 is a crystal growth chamber; 52 is a substrate (a substrate to be grown or a wafer); 53 is a substrate holder for supporting the substrate 52;
4 is a heater for heating the substrate; 55 is a molecular beam source cell; 56 is pulp for controlling on/off the source gas supplied to the molecular beam source cell; 57 is a liquid nitrogen shroud for gas adsorption;
58 is a gate pulp for insulating the crystal growth chamber 51 from the vacuum evacuation system. As shown in the figure, the substrate 52 is held in a substrate holder 53 and heated by a heater 54 to set a predetermined substrate temperature. For example, if the substrate 52 is a GaAS substrate, it is heated to 400 to 700°C. Here, a plurality of molecular beam source cells are arranged facing the wafer 52.

Figures 2 (B) and (C) show cross-sectional views of conventional molecular beam source cells, and (B) is a low-temperature cell for low-temperature decomposition gas;
C) is a high temperature cell for high temperature decomposition gas.

In FIGS. 2(B) and (C), 61 is a gas introduction pipe, 62 is a heater, 63 is a vacuum flange of the crystal growth chamber 51, 64 is a heat shield plate around the heater 62, and 65 is a sintered boron nitride ( P.B.
N) It is a board.

The molecular beam source cell for low-temperature decomposition gas shown in Figure 2 (B) is
Triethylgallium (T
It is used for organometallic gases such as EG) and triethylaluminum (TEA), and the inside of the cell is heated to 50 to 60 degrees Celsius, a temperature that prevents gas molecules from condensing. Gas molecules are emitted from the 5 ports on the 6 PBN plates at the outlet.

The molecular beam source cell for high-temperature decomposition gas shown in FIG. 2(C) is used, for example, for metal hydride gas such as arsine (ASH3), which is a group V raw material gas, and is heated to 800 to 900°C. Arsine is decomposed into As and H2 and As is emitted toward the substrate.

In the high-temperature cell, heaters 62 and PBN plates 6 are closely arranged at the outlet, and the PBN plates 6 and 5 are shifted from each other to cause the scum to collide with the PBN plate 65 heated to a high temperature to release gas. A thermal cracking section 66 for decomposition is provided. Note that the thermal cracking section 66 is not provided in the molecular beam source cell for low-temperature decomposition gas.

These molecular beam source cells are, for example, 1/4 inch in diameter,
It is formed of a quartz tube with a length of about 30 crg, and the distance between the tip of the cell and the wafer 52 is relatively short.

For example, when growing a GaAs layer or an AlGaAs layer using the gas source molecular beam epitaxial growth apparatus as described above, TEG is used as the Ga source, TEA is used as the AI source, and arsine is used as the S source. is emitted from a high-temperature molecular beam source cell (Fig. 2 (C)) heated to approximately 900°C, and
, TEA is emitted from a low temperature molecular beam source cell (FIG. 2(B)) at about 50 to 60°C. Arsine is 400-700
Since it is not decomposed on a GaAs substrate heated to .degree. C., it is thermally decomposed in advance in a molecular beam source cell and emitted as a single As molecule or 482 molecules.

On the other hand, since TEG and TEA can be thermally decomposed at low temperatures,
In the molecular beam source cell, the cell is heated to such an extent (50 to 60° C.) that the source gas does not adhere to the tube wall of the molecular beam source cell, which is not thermally decomposed. The gas source is decomposed and deposited on the heated GaAs substrate.

For example, when growing an AlGaAs/GaAs heterostructure, the gas introduction pulp 56 of the TEA molecular beam source cell
By opening and closing, the A1 composition can be controlled on and off.
Switching between the 1GaAs layer and the GaAs layer is performed.

The semiconductor crystal formed in this way is a double hetero (
DH) Used to manufacture semiconductor devices such as lasers and HEMTs, and semiconductor integrated devices.

[Problem to be Solved by the Invention] As described above, the gas supply path from the gas source to the gas supply cell in the crystal growth chamber is provided with the pulp 56, and when the gas supply is cut off, the pulp 56 is closed. That's what I was doing.

However, even if the pulp 56 is closed, raw material gas remains between the pulp 56 and the cell supply port, and this raw material gas is released from the cell supply port and reaches the substrate 52. Although an attempt is made to grow a crystal layer that does not contain the blocked components on the substrate 52, the blocked components end up entering.

Even if an attempt is made to form a junction with a steep distribution, only a gradually changing distribution will be obtained.

Further, in an integrated circuit device, when a homogeneous grown film is required on a substrate, the homogeneity of the grown film is reduced.

Attempts have been made to prevent residual gas from flowing out by installing a shutter over the supply port of the molecular beam source cell, but there is still residual gas inside the cell, and gas is released through the gap between the shutter and the cell. and reaches the substrate. Even if the amount of gas flowing out per unit time decreases, the time it takes for the gas to run out increases on the contrary. In this way, the shutter is not a perfect countermeasure, especially when using dopants such as SiH4 and Si2H6.
When using a gas such as, this residual dopant gas becomes a problem.

The object of the present invention is that when the raw material gas of a certain component is cut off,
It is an object of the present invention to provide a gas source crystal growth apparatus that can reduce problems caused by residual debris in the crystal growth apparatus on crystal growth.

The purpose of the pond of the present invention is to provide a gas source crystal growth apparatus in which the residual gas in the crystal growth apparatus is automatically exhausted when the raw material gas of a certain component is cut off.

By using these gas source crystal growth apparatuses, interfaces of heterojunctions and p I'l junctions having a steep distribution are formed.

[Means for solving the problem] The above purpose is to connect the gas supply cell to the exhaust system,
This is achieved by a gas source crystal growth apparatus in which a gas outlet with pulp is connected to a gas supply cell.

Further, in order to automatically discharge the residual gas, it is sufficient to provide a control system that synchronously controls the pulp in the gas introduction path and the pulp in the gas discharge path.

A crystal growth chamber 1 shown in FIG. 1 is an airtight container that houses a substrate holder 3 that supports a substrate 2 and is connected to a first evacuation system 4.

A gas supply cell 5 is arranged in the crystal growth chamber 1 so as to face the substrate 2 . This gas supply cell 5 is connected to a gas source 7 by a gas inlet 8 with a first pulp 6, while connected to a second evacuation system 10 by a gas outlet 11 with a second pulp 9. ing. The first evacuation system and the second evacuation system may be the same, and the gas introduction path 8 and the gas exhaust path 11 may be connected to the pulp 6.
Part of the structure between the gas supply cell 9 and the gas supply cell 5 may be common.

A control system 12 may further be provided so that when the first pulp 6 is closed, the second pulp 9 is opened synchronously.

[Effect] Conventionally, waste introduction F! When the first pulp 6 of @8 is closed,
At that time, the gas existing between the first pulp 6 and the outlet of the gas supply cell 5 had no choice but to exit through the outlet of the gas supply cell 5. Since the substrate 2 exists on the path of the gas flow connecting the outlet of the gas supply cell 5 and the first evacuation system 4, it is inevitable that gas molecules will accumulate on the substrate 2. According to the crystal growth apparatus, there is a gas exhaust passage 11 that connects the gas supply cell 5 to the second evacuation system 10, so when this pulp 9 is opened, the gas supply cell or the first pulp of the gas introduction passage 8 is opened. The gas remaining in the portion closer to the cell 5 than the cell 6 can be exhausted to the second vacuum evacuation system. Therefore, the residual gas is discharged quickly. Furthermore, the number of gas molecules directed toward the substrate 2 from the outlet of the gas supply cell 5 can be significantly reduced. In this way, the residual gas reaching the substrate 2 can be reduced quantitatively and temporally, and an interface with a steep distribution can be realized.

Furthermore, the first pulp 6 of the gas introduction path 8 and the waste discharge #1
By providing a control system that synchronously controls the eleven second pulps 9, residual gas can be automatically discharged when the gas supply is cut off.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings.

FIGS. 3(A), 3(B), and 3(C) show a gas source molecular beam crystal growth apparatus according to one embodiment of the present invention, in which (A) shows the entire main part of the crystal growth apparatus, (B), C) shows a low-temperature cell and a high-temperature cell used in the device of (A).

The crystal growth chamber 1 is formed of an airtight container connected to an evacuation system by a gate pulp 18, and includes a substrate holder 3 on which the substrate Z is placed and a heater such as a tantalum wire for heating the substrate 2. 14, and is further provided with a liquid nitrogen-cooled shroud 17 on the inner wall, which adsorbs gas molecules and prevents reflection.

In the illustrated apparatus, gas supply cells 5 constituting four molecular beam sources are provided in a crystal growth chamber 1. This number can be increased or decreased as needed. Each gas supply cell 5 is connected to a gas introduction path 8 provided with a first pulp 6 and a gas discharge path 11 provided with a second pulp 9.

FIGS. 3(B) and 3(C) show two structures of the gas supply cell and piping section of the crystal growth apparatus shown in FIG. 3(A).

A gas exhaust pipe 11 equipped with a second pulp 9 is provided on the side of the gas supply cell 5 from the first pulp 6 of the gas introduction pipe 8, and this gas exhaust pipe 11 is exhausted by a dedicated turbo molecular bong. There is. The gas supply cell 5 is a space whose outlet is defined by a sintered boron nitride (PBN) plate 25 having an opening.
It is heated by a heater 22 such as tantalum wire. Heater 2
A heat shielding plate 24 is disposed on the outside of the housing 2 to prevent heat from being radiated to the outside. 23 is a vacuum flange that becomes the wall of the crystal growth chamber 1. In the high-temperature cell shown in FIG. 3(C), a plurality of PBN plates 2 and metal plates 5 with openings shifted in position are placed near the outlet, and these PBN plates are tightly wound and heated by the heater 22. The gas molecules collide with the PBN plate 2 and the metal plate 5 and head towards the substrate 2. During the collision, the gas molecules receive heat from the PBN plate 25, so the gas molecules decompose at a high temperature.

In the growth of ■-V group compound semiconductors, for example, organometallic gases such as TEG and TEA are used as source gases for group ■ elements, and hydrides such as arsine and phosphine are used as source gases for group V elements. use In general, organometallic gases are easily decomposed, so they are supplied using the low-temperature cell shown in Figure 3 (B), and hydrides are difficult to decompose, so they are heated to a high temperature and decomposed in the high-temperature cell shown in Figure 3 (C), and then the substrate is supplied. supply to.

The second pulp 9 of the gas discharge pipe 11 synchronizes opening and closing with the first pulp 6 of the gas introduction pipe 8, and when the second pulp 9 is open, the first pulp 6 is automatically closed. A synchronous control system may be provided so that when the second pulp 9 is closed, the first pulp 6 is automatically opened.

Using such a gas supply cell, for example, arsine (
85H3),)-ethylgallium (TEG) Ga
When forming an AS/AI GaAs heterojunction,
These gases are introduced into the gas supply cell 5 via the gas introduction pipe 8 and the first pulp 6.

For arsine, use the high temperature cell shown in Figure 3 (C),
A low temperature cell shown in FIG. 3(B) is used for EG and TEA. Molecular beams are supplied from three gas supply cells, and GaAs
When moving on to layer growth, close the pulp 6 of the gas inlet pipe of the TEA gas supply cell, and at the same time close the pulp 9 of the gas exhaust pipe.
Open. The TEA gas remaining in the TEA gas supply cell is exhausted through the gas exhaust pipe 11.

A specific example of growing an AlGaAs layer on a GaAs substrate by introducing arsine, TEG, and TEA using the gas source molecular beam crystal growth apparatus shown in FIGS. 3(A), (B), and (C) will be explained. . The substrate temperature is 600°C. AlGaA
After growing the s-layer to a thickness of about 0.5 μm, the pulp 6 of the gas introduction tube of the molecular beam source cell for TEA is closed and the pulp 9 of the gas exhaust tube is simultaneously opened to finish the growth of the AlGaAs layer and to remove the GaAs layer. Start growing. The GaAs layer grows approximately 0.1 μm. This is how I grew up ^1
The steepness of the interface of the GaAs/GaAs heterostructure can be investigated by the depth profile of the A1 element by sputter Auger (AES).The composition can be similarly controlled using only the opening/closing pulp 6 of the conventional gas introduction tube. Compared to a GaAs heterostructure, the steepness of the depth profile of the A1 element in the crystal produced by the above growth process is about 5, which is about half that of the conventional one. It can be seen that this method is effective in forming a heterocrystalline growth layer.

The above example was explained in the case of closing the molecular beam of group Ⅰ elements, but by using a molecular beam source cell for a dopant gas such as disilane (Si2H6), a crystal with a steep doping profile can be created. Of course you can grow. In the case of disilane, the high temperature cell shown in FIG. 3(C) is used.

FIGS. 4(A) and 4(B) show other embodiments of the present invention. In FIG. 4(A), the gas from gas 'a7 is controlled to a constant flow rate by a mass flow meter 32, and the gas introduced f #I
8. Mass flow meter 32 and crystal growth chamber 1
A first opening/closing pulp 6 is arranged between the inner gas supply cell 5 and the gas supply cell 5 to control on/off of the gas flow. When the first opening/closing pulp 6 is closed, the second opening/closing pulp 9 and the third opening/closing pulp 34 are opened. The second opening/closing pulp 9
The first gas discharge passage 11 is connected to the gas introduction passage between the openable pulp 6 and the gas supply cell 5. 1st
By closing the opening/closing pulp 6 and opening the second opening/closing pulp 9, the residual gas in the gas supply cell 5 can be evacuated through the first gas exhaust path 11.

Further, the third open/close pulp 34 is provided in the second gas exhaust path 36. The second gas exhaust path 36 is connected to the gas introduction path 8 between the first openable pulp 6 and the mass flow meter 32, and the other end is connected to the exhaust system. When the first switching pulp 6 closes, the third switching pulp 34 is opened, bypassing the gas flow from the mass flow meter 32.

These three opening/closing pulps 6.9.34 are controlled by the synchronous control system 38
synchronously controlled by. That is, the gas flow supplied from the mass flow meter 32 is sent to either the gas introduction path 8 or the second gas exhaust path 36, and the gas supply cell 5 in the crystal growth apparatus 1 receives the source gas from the gas introduction path 8. is supplied or exhausted through the first gas exhaust path 11.

Such a pulp group 6.9.34 can be constituted by a four-sided pulp as shown in FIG. 4(B).

In FIG. 4(B), A, B, C, and D represent four boats, and 41, 42, and 43 represent bellows pulp. Boat A is connected to the gas supply cell side, boat B is connected to the gas source side, and boats C and D are connected to the exhaust system. Pulp 41.
When the chamber 42 is closed, no bellows appear on the surface facing the crystal growth chamber 1, which is in an ultra-high vacuum.

Such a four-way pulp may be controlled by electromagnetic force or fluid force such as air.

Figure 5 (A>, (B) shows a four-way pulp driven by an air cylinder valve, where (A) is a top view and (B) is a V
A cross section taken along the line B-VB' is shown.

In FIG. 5(A), A, B, (, D are four boats forming four ports, and air cylinder valves 44, 45.
46 is a drive source that operates the three pulps with air.

In the cross-sectional view of FIG. 5(B), air cylinder valve 44.
45, 46 move their driving sills 47, 48, 49 in response to the air flow shown by the arrows, and these driving sills 47, 48, 49 move the bellows pulp 41.
42. 1 branch A'B' where 43 is operated is boat A
, is the entrance of the channel toward boat B. By synchronously controlling the three air flows, the four-way pulps shown in FIGS. 5(A) and 5(B) can be synchronously controlled.

Although the present invention has been described in accordance with the embodiments above, these embodiments are not intended to have an equivalent and restrictive meaning.

It will be obvious to those skilled in the art that various changes, modifications, combinations, etc. can be made within the scope of the present invention.

"Effects of the Invention" As explained above, according to the present invention, since the gas supply cell can be directly evacuated, the residual gas in the gas supply cell etc. can be quickly discharged, and the composition of the raw material gas supplied onto the substrate can be changed. Can be changed quickly.

When controlling pulp synchronously, the gas that has been shut off can be automatically discharged.

By quickly switching the raw material gas composition, interface structures such as heterojunctions and ρn junctions with steep profiles can be realized.

Figures 5 (A) and (B) show examples of pulp that can be used in the embodiments of the present invention shown in Figures 4 (A) and (B). is a plan view, and (B) is a cross-sectional view.

In the figure,

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the principle of the present invention. FIGS. 2 (A), (B), and (C) show a conventional gas source molecular beam crystal growth apparatus, where (A> is an overall cross-sectional view, and CB>
, (C) is a sectional view of a gas supply cell section for low temperature and high temperature, and FIGS. 3(A), (B), and (C) show a gas source molecular beam crystal growth apparatus according to an embodiment of the present invention. , (A) is a cross-sectional view of the whole, (B) and (C) are cross-sectional views of the gas supply cell parts for low temperature and high temperature, and FIGS. 4 (A) and (B) are other embodiments of the present invention. (A) is a block diagram of the main part, (B)
Pal crystal growth chamber Substrate substrate holder First evacuation system Gas supply cell First pulp gas source Gas introduction path Second pulp Second evacuation system Gas exhaust path Synchronous control system 41.42° 44, 45 A, B, C 47, 48 Heater shroud Gate Pulp heater flange Heat shield plate PBN plate Third pulp Second gas exhaust path 43 Bellows pulp 46 Air cylinder valve D Boat 49 Drive cylinder Crystal growth chamber Substrate substrate holder Heater Molecular beam source Cell pulp Shroud Figure 1 Gate Pulp gas inlet pipe Heater Vacuum flange Heat shield plate PBN plate Thermal cracking section (A> Overall view (B) Low temperature cell (C) High temperature cell B is also a conventional gas source molecular crystal growth apparatus No. 2 Figure 3 (Part 1) Figure 3 (Part 2) (A) Main part (B > Pulp system

Claims (1)

[Claims] (1) In a gas source crystal growth apparatus for growing crystals from a gas source in a low pressure atmosphere, the first vacuum evacuation system (4) is connected to grow crystals on a substrate (2) in a low pressure atmosphere. an airtight crystal growth chamber (1) that accommodates a substrate holder (3) on which a substrate (2) is placed; a gas supply cell (5) disposed within the crystal growth chamber (1); and a first pulp (6) for controllably connecting the gas supply cell (5) to a gas source (7). a gas introduction path (8) connected to the gas supply cell (5) by means of a second pulp (10) for controllably connecting the gas supply cell (5) to a second evacuation system (10); 9) and connected to the gas supply cell (5).
) and a gas source crystal growth apparatus.