JPS6319814A - Vapor growth equipment - Google Patents

Abstract

PURPOSE:To facilitate laminating crystal layers of different compositions easily and stably so as to have sharp boundaries by a method wherein 2nd gas flow controllers and valves controlling gas flows are provided and gases are made to join in gas supply tubes after 1st gas flow controllers. CONSTITUTION:When a 1.1 mum InGaAsP film which is a barrier layer of a superlattice structure is grown, a valve 10 of a gas supplementing tube 9 for TEI is opened, a valve 12 of a gas supplementing tube 11 for TEG is closed, a valve 14 of a gas supplementing tube 13 for PH3 is opened and a valve 16 of a gas supplementing tube 15 for AsH3 is closed. The gas supplementing tubes 9, 11, 13 and 15 are connected to the parts of respective gas supply tubes 17, 18, 19 and 20 after 1st gas flow controllers 1, 3, 5 and 7. When a 1.3 mum InGaAsP film which is a well layer is grown, the valves 10 and 14 are closed and the valves 12 and 16 are opened. The sharpness between the respective layers of the super-lattice structure which is formed by repeating such switching operations of the valves 10, 12, 14 and 16 is not larger than 15 Angstrom .

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a vapor phase growth apparatus capable of stably and easily stacking crystal layers having different compositions at steep interfaces.

Conventional technology When manufacturing semiconductor devices, the epitaxial growth technology for semiconductor crystals that is required involves using gas as a raw material.
There is a vapor phase growth method that uses the thermal decomposition reaction to grow crystals. A feature of this growth method is that it can be mass-produced by growing large areas and growing many wafers at once.

FIG. 3 shows an example of such a vapor phase growth method. This is an organometallic vapor phase epitaxy method (M
etal Organic VaporPhase E
This is an outline of the gas system of the MOVPE apparatus when growing In, -GaxAsyP1-y on a nP substrate by pitaxy (MOVPE method). When forming a device such as a semiconductor laser or a superlattice structure, crystal layers with different compositions are stacked. In the vapor phase growth method, the supply amount of each raw material gas is adjusted.

Through control, the composition can be varied in various ways. For example, the composition
The supply amount of TEG) can be changed by adjusting the flow rate control devices 41 and 42, respectively. On the other hand, for composition y, phosphine (PH3), which is a stock gas for P, and arsine (A
s Hs ) can be varied by adjusting the respective flow control devices 43 and 44. Therefore, when stacking crystals with different compositions, after growing the lower layer, adjust each flow rate control device to set the raw material gas supply amount for growing the upper layer.
Let's start laminating.

Problems to be Solved by the Invention However, when crystals of different compositions are successively stacked, the amount of raw material gas supplied must be adjusted and controlled depending on the composition of the growing crystals. Therefore, after growing the lower crystal layer and before growing the upper crystal layer, time is required to adjust the flow rate control device for the raw material gas. If crystal growth is performed continuously during this period, the composition changes, a transition layer with poor crystallinity is formed, and the steepness of the laminated interface becomes extremely poor. In order to prevent this, the supply of raw material gas to the growth furnace is stopped and the flow rate is adjusted, but this results in a longer growth time as the number of layers increases. Especially when forming a superlattice structure with dozens of layers stacked,
It will take a very long time. Furthermore, since the flow rate is adjusted each time by a flow rate adjustment device, when crystals of the same composition are stacked many times as in a superlattice structure, the composition of each crystal will vary depending on the repeat accuracy of flow rate adjustment.

The present invention has been made in view of the above, and an object of the present invention is to provide a vapor phase growth apparatus that can stably and easily stack crystals having different compositions at steep interfaces.

Means for Solving the Problems The technical means of the present invention for solving the above-mentioned problems are as follows:
The vapor phase growth apparatus includes a first gas flow rate control device,
A gas supply pipe portion subsequent to the first gas flow rate control device, comprising a gas supply pipe that supplies gas to the growth furnace, a second gas flow rate control device, and a valve that controls the flow of the same type of gas as the gas. and at least one gas replenishment pipe connected so that the gases of each other join together and are supplied to the growth furnace.

For production The effect of this technical means is as follows.

controlled to a constant flow rate by a first gas flow rate controller;
By opening the valve and allowing the gas, which is controlled at a certain flow rate by the second gas flow rate control device, to join the gas supplied to the growth furnace, the supply amount of the raw material gas supplied to the growth furnace is adjusted to the first level. It is also possible to change the gas flow rate in the opposite direction to the second gas flow rate regulation from the flow rate determined by the gas source amount control device. Therefore, it is possible to change the supply amount of the raw material gas simply by opening and closing the valve, and therefore crystals having different compositions can be stacked stably and easily at a steep interface.

EXAMPLE Hereinafter, as an example of the present invention, 1.
1μm InGaAsP and 1.3pm InGaA
The case of forming a superlattice structure consisting of sP will be explained with reference to the drawings. This superlattice structure is used as the active layer of a multiple quantum well laser (MQWLD).
The current flow efficiency is improved and the light emitting efficiency is superior to that of an MQW-LD made of ordinary InP and 1.3 pm band InGaAsP. Now, In, Ga, As.

Triethyl indium (TEI) and triethyl gallium (TE
G), arsine (A s H3), phosphine (PH3
) is used. TEI is an organometallic.

Since TEG is a liquid with relatively high vapor pressure, it is supplied in the form of vapor gas by passing carrier gas (hydrogen gas) through it. FIG. 1 shows an outline of the gas system of the M○VPE apparatus which is an embodiment of the present invention used for growth.

Next, 1.1 μm InGaA, which is a barrier layer with a superlattice structure.
The following table shows the amount of raw material gas supplied during crystal growth of sP and 1.3 μm InGaAgP of the well layer. In addition, TEI, T
EG is indicated by the flow rate of hydrogen gas sent to each bubbler container.

Therefore, first, the flow rate of the first gas flow rate control device (1) of the TII is adjusted to 30αc/six, and the flow rate of the second gas flow rate control device 2 is set to 80CC/yH.The first gas flow rate control of the TEG The flow rate of device 3 was 75CC/zgH.

The flow rate of the second gas flow rate control device 4 is B es cc /
Let it be y, in. The flow rate of the first gas flow rate control device 6 of PH3 is set to 10ccAin, the flow rate of the second gas flow rate control device 6 is set to 9.5CC/sin, and A s
The flow rate of the first gas flow rate controller 7 of H3 is set to 0.6 CC.
/ml, and the flow rate of the second gas flow rate controller 8 is 0.9C.
1, which is a barrier layer with a superlattice structure, which is set as C/mix;
When growing 1 μm InGaAsP, open the valve 10 of the TEI gas replenishment pipe 9, close the valve 12 of the TEG gas replenishment pipe 11, open the valve 14 of the PH3 gas replenishment pipe 13, and replenish the A s H3 gas. Close valve 16 of tube 16. Each gas replenishment pipe 9, 11, 13, 15 corresponds to the first gas flow control device 1 of each gas supply pipe 17, 18, 19, 20.
It is connected to the part after ゜3.5.7. As a result, the TEI supply amount is the sum of the adjusted flow rates of the first and second gas flow rate controllers 1 and 2, which is 380 g/win (300 g/win).
+80). Also, the supply amount of TEG is 12. ``Only the regulated flow rate of the first gas flow rate controller (76CC/x
i) There is f. In the same way, the supply amounts of PH3 and AsH3 are calculated as shown in the table: 1.1 μm I nGaAs P
is the raw material supply amount for crystal growth. Next, a well layer of 1.3 μm
When proceeding to the growth of InGaAsP, valves 10 and 14 are closed and valves 12 and 16 are opened. Then, 1.1μmIn
In the same manner as in the case of GaAsP, when the supply amount of each raw material gas is examined, it becomes the raw material supply amount for crystal growth of 1.3 μm InGaAsP.

By repeating the opening and closing of the valves 10, 12, 14, and 16 in this way, 1.1 μm InGaAsP and 1.3 μm InGaAsP
A superlattice structure made of InGaAsP is formed.

The steepness between each layer of the formed superlattice structure was 16 Å or less, which was less than % of the conventional value. In addition, each raw material gas is supplied to the growth furnace 21 through gas supply pipes 17, 18 and 19, 20.
is supplied to The substrate 22 is placed on a susceptor 24 which is heated to a growth temperature by induction heating by a high frequency coil 23. Further, the inside of the growth reactor 21 is pressurized to 100 Torr by a pressure reducing pump 25. Furthermore, although a mass flow controller was used as the gas flow rate control device this time, the present invention is not limited to this, and any device that can arbitrarily set and control the gas flow rate may be used.

As described above, according to the present invention, crystals having different compositions can be stacked by simply opening and closing a valve, without adjusting the flow rate of a gas flow rate control device each time as in the conventional case. Therefore, the time required for adjusting the flow rate became unnecessary and could be saved.

Furthermore, the steepness of the interface between crystal layers was improved. There is no longer any decrease in flow rate setting accuracy due to repeated flow rate adjustments.
It was possible to reduce the compositional variation between crystals of the same composition by about 26 inches. Moreover, the adjustment errors that occurred when adjusting the flow rate are completely eliminated.

Next, FIG. 2 shows a schematic diagram of a gas system of a MOVPE apparatus according to a second embodiment of the present invention. Since most of the components are the same as the MOVPE device shown in FIG. 1, only the different points will be described. The TEI and TEG gas replenishment pipes 9 and 11 connect the first gas flow rate controller 1.3 of the respective gas supply pipe 17.18 and the TE, which is a raw material supply source for crystal growth.
It is connected to the bubbler containers 37 and 38 of I and TEG, and to the gas pipes 31 and 32 for other carrier gases connected to the growth furnace 21. Control valves 33 and 34 are provided which open and close in conjunction to allow gas to flow to either direction. Therefore, the gas in the gas replenishment pipes 9 and 11 is operated by the control valve 33.34, merges with the gas in the gas supply pipe 17.18, flows to the TEI and TEG bubbler containers 37.38, and is fed to the source gas. Increase the supply amount or conversely connect other gas pipes 31.3
2, and is supplied to the growth reactor as hydrogen gas.

By doing this, the growth reactor 21 can be accessed from the TEI or TEG side.
The total amount of gas supplied to the source gas does not change even if the amount of raw material gas supplied changes.

Additionally, PH3 and A s H3 gas replenishment pipes 13.15
As shown in the figure, the valves 36 and 36 are provided as a set of two valves 36 and 36 that open and close each other so that gas flows into the gas replenishment pipe 13. and the other is connected to a carrier gas supply source (hydrogen supply source). By doing this, P Hs , A
s The total flow rate of gas on the H3 side is the raw material gas PH3
, even if the flow rate of AsH3 is changed, it does not change. From the above, the flow rate of the gas in the growth furnace is always constant and the flow direction is always stable, making it possible to stack layers with good interfaces.

At this time, the valves 10, 12, 14, and 16 must always be open.

As described above, in this MOVPE device as well, the supply amount of raw material gas can be changed by operating the two control valves 33, 34 and 35, 36, and the flow rate of the gas flow rate control device can be adjusted. Therefore, crystals having different compositions can be stacked stably and easily. Note that the control valves 33 and 34 are not a set of two valves, but may be provided with a three-way valve, for example, as long as it has a mechanism that allows flow to flow in either direction. Also, in this FIG. 2, one of the gas replenishment pipes 9, 11 is connected to the other gas pipe 31, 32, but
8 TEI, TEG bubbler container 37°38 onwards,
It may be connected between the growth furnace 21 and the growth furnace 2.
The effect is the same even if it is connected directly to 1.

In the above explanation, M○
Although a VPE apparatus was used, a general VPE (Vapor
The present invention is also applicable to a Phase Epitaxy (Phase Epitaxy) device.

Furthermore, although there was only one gas replenishment pipe in the explanation, there are as many gas replenishment pipes as there are crystal layers with different compositions, and if you set the flow rate of each gas flow control device in advance, you can use two gas replenishment pipes. Even in the case of stacking crystal layers having different compositions as described above, the same effects as the present invention can be obtained and the present invention can be applied.

Effects of the Invention As described above, according to the present invention, it is possible to stack crystals with different compositions by simply opening and closing a valve, without having to adjust the gas flow rate using a gas flow rate controller every time each crystal layer grows. Become. Therefore, the time required to adjust the flow rate during growth,
Variations in composition resulting from variations in settings during adjustment,
Deterioration in crystallinity and film quality can be eliminated, and quality and productivity are improved in terms of the crystal growth process.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a gas system of an MOVPE apparatus according to an embodiment of the present invention, and FIG. 2 is a schematic diagram of a MOVPE system according to another second embodiment of the present invention.
Schematic diagram of the gas system of the PE equipment, Figure 3 is the conventional M○VP
It is a schematic diagram of the gas system of E equipment. 1.3, 6.7...first gas flow rate control device,
2, 4, 6, 8----second gas flow rate control device, 9゜11.13, 15... gas replenishment pipe,
10,12゜14.16...Valve, 17.1B,
19.20... Gas supply pipe, 21...
Growth furnace, 31.32... River/other gas pipes, 33.34.
... Control valve, 37.38 ... Raw material supply source for crystal growth.

Claims (4)

[Claims] (1) comprising a first gas flow rate control device, a gas supply pipe that supplies gas to the growth furnace, a second gas flow rate control device, and a valve that controls the flow of the same type of gas as the gas; A gas supply pipe section after the first gas flow rate control device is equipped with at least one gas replenishment pipe connected so that the gases of each other join together and are supplied to the growth furnace. Vapor phase growth equipment. (2) The vapor phase growth apparatus according to claim 1, wherein the gas is a raw material gas for crystal growth, a carrier gas, or a mixed gas thereof. (3) A gas replenishment pipe is connected between the first gas flow rate control device of the gas supply pipe and the raw material supply source for crystal growth, and downstream of the raw material supply source for crystal growth, or to the growth furnace or the growth furnace. 2. The vapor phase growth apparatus according to claim 1, further comprising a control valve that is connected to two locations of the other gas pipe and allows the flow to flow to either one. (4) The vapor phase growth apparatus according to claim 3, wherein the raw material source for crystal growth is an organometallic bubbler container.