JPH10189458A - Film forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film forming apparatus for reducing pressure change in a reaction furnace occurring when a material supply line connected to a vent line is switched to be connected to a main line. SOLUTION: The film forming apparatus comprises a main line 2 connected to a reaction furnace 1 to supply material gas to the furnace 1, a vent line 3 for previously feeding the gas, a plurality of material supply lines connected to the line 2 via a first valve and connected to the line 3 via a second valve, a pressure gage 13 inserted into the furnace 1, and a reaction furnace inner pressure control valve 14 provided at an exhaust line 16 connected to a downstream of the furnace 1 to feed back a detection signal of the gage 1, thereby communicating the line 3 for forming a film of desired composition on a surface of a substrate 12 by controlling supply amounts of respective material gases at a downstream of the furnace 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film forming apparatus, and more particularly to a semiconductor laser LD, a light emitting diode LED,
In a film forming apparatus for forming a compound semiconductor single crystal multilayer film of an optical element such as a field-effect transistor FET and a photodiode, a reaction furnace generated when a raw material supply line connected to a vent line is switched to a main line and connected. The present invention relates to a film forming apparatus for reducing pressure fluctuation of the film.

[0002]

2. Description of the Related Art A conventional example will be described with reference to FIG. In a film forming apparatus for forming a compound semiconductor single crystal multilayer film of an element such as a semiconductor laser LD, a light emitting diode LED, a field effect transistor FET, and a photodiode, a susceptor 11 is housed and fixed in a reaction furnace 1. The susceptor 11 is provided with a substrate 12 on which a substance is to be formed. A pressure gauge 13 is inserted in the reactor 1, and a reactor pressure control valve 14 is inserted in the middle of an exhaust line 16 connected downstream of the reactor 1. The detection signal of the pressure gauge 13 is fed back to the reactor pressure control valve 14. The rotary pump 17 is connected to the discharge line 32 to suck and discharge the exhaust gas sent from the reaction furnace 1 and to suction and discharge the vent gas.

[0003] A main line 2 is connected to the reactor 1. The vent line 3 is a main / vent differential pressure control valve 30.
Is connected to the discharge line 32. The plurality of raw material supply lines 4 are connected to the main line 2 via respective valves 42 and connected to the vent line 3 via respective valves 43. A differential pressure gauge 13 ′ is inserted between the main line 2 and the vent line 3, and the detection signal is fed back to the main / vent differential pressure control valve 30. As the carrier gas flowing through the main line 2 and the vent line 3, hydrogen gas or nitrogen gas is usually used. The raw material supply lines 4 are connected to, for example, TMI, TMG, AsH3, PH3, and other raw material gas supply sources. Although only four source gas supply sources are shown in the figure, each layer of the multilayer film to be formed is actually provided with a number corresponding to the number of types of source gas necessary to form the layer. I have.

Hereinafter, the semiconductor laser LD shown in FIG.
A case where a multilayer film is formed will be described as an example. (1) Before starting film formation, the material is formed
The substrate 12 to be mounted is placed on the susceptor 11. (2) As preparation before the start of film formation, the main line 2
Carrier gas is supplied to both vent lines 3 for 3 to 10
SLM (Standard liter pers)
econd) and distribute all raw material gas
Flow rate of 100 to 300 sccm through the raw material supply line 4
(Standard cubic-centimet
er per second) and the main line 2
Mix and distribute in the rear gas. Here, each layer is formed
Source gas required for, for example, an InP layer as a first layer
Trimethylindium TMI and
And phosphine PH3, a second layer of InGaAsP layer
Trimethylindium TMI and
And triethylgallium TEG, arsine gas AsH _Three,
Phosphine PH3 And a third InGaAsP layer.
The source gases to be formed, trimethylindium TMI and trimethylindium
Ethyl gallium TEG, arsine gas AsH _Three, Foss
Fin PH3 Similarly, a raw material gas for forming the fourth and lower layers
All required flow rates from each raw material supply line.
In the reactor 3 and the
While controlling the pressure to the set pressure, the main line 2
Pressure in vent line 3 to equalize the pressure in vent line 3.
Force is applied to differential pressure gauge 13 'and main / vent differential pressure control valve 3
Adjust with 0.

(Third) The susceptor 11 of the substrate 12 is heated in advance in the reaction furnace 1 to a film forming temperature of several 500 to 700 ° C. by an induction heating device or another heating device. (Fourth) By switching the valves 43 and 42 of the first-layer source line, the source gases trimethylindium TMI and phosphine PH3 for forming the first-layer InP layer which had been circulated through the vent line 3 were supplied. When the substrate 1 is fed into the reactor 1 via the main line 2, the substrate 1
On the surface of No. 2, the source gas is thermally decomposed to form an InP layer.

When the valve is switched, the flow rate in the vent line 3 is reduced, and a temporary pressure difference is generated between the main line 2 and the pressure difference. The pressure difference is measured by the differential pressure gauge 13 'and the main / vent differential pressure control valve 30. The difference disappears. (Fifth) When the first InP layer is formed to a required film thickness, the valve 43 and the valve 42 of the first layer source line are switched to form a source gas for forming the first InP layer. At the same time as the supply to the main line 2 is cut off, the valves 43 and
And the source gases trimethylindium TMI and triethylgallium T, which form the second InGaAsP layer that has been circulated in the vent line 3,
EG, arsine gas AsH ₃ , phosphine PH3 Is fed into the reaction furnace 1 through the main line 2 and the substrate 12
The source gas is thermally decomposed on the surface of the first InP layer formed on the surface of the first layer to form a second InGaAsP layer. In this case as well, the flow rate of the vent line 3 is reduced by switching the valve, and a pressure difference is temporarily generated between the main line 2 and the pressure difference.
The pressure difference is eliminated by the vent-to-vent differential pressure control valve 30. Second
When a layer composed of various kinds of elements In, Ga, As, and P is formed like a layer, the composition of the film is determined by adjusting the ratio of the supply amounts of the source gases of these elements. From the time when the source gas flowing through the vent line 3 is switched to the main line 2 at the start of the film, the source gas must reach the substrate 12 at the set flow rate. In order to allow the source gas to reach the substrate 12 at the set flow rate from the time of the switching, there must be no difference between the pressure in the vent line 3 and the pressure in the main line 2 at the time of the switching. The same operation is performed when the third and subsequent layers are formed.

As described above, by switching the required source supply line from the vent line to the main line, a desired source gas is supplied at a desired flow rate onto the substrate, and a film having a desired composition is formed on the substrate. I do. Further, the film formation is completed by switching the raw material supply line connected to the main line to the vent line.

[0008]

In the above-described film forming apparatus, each raw material supply line 4 connected to the vent line 3 is used.
Is switched to the main line 2 and the pressure in the reactor 1 rises at that moment. This pressure increase is finally properly controlled by feedback-controlling the reactor internal pressure control valve 14 inserted in the exhaust line 16 of the reactor 1 based on a detection signal detected by the pressure gauge 13 inserted in the reactor 1. However, an unstable pressure state temporarily exists until the temperature becomes appropriate, and the supply amount of the source gas on the substrate 12 becomes unstable. A shifted thin film is formed.

The present invention is to provide a film forming apparatus in which the above-mentioned problem is solved by reducing the pressure fluctuation in the reactor caused when the raw material supply line connected to the vent line is switched to the main line and connected. It is.

[0010]

Means for Solving the Problems An internal pressure controlled reactor 1
And a vent line 3 through which the raw material gas is passed in advance, which is connected to the main line 2 via a first valve. It has a plurality of raw material supply lines connected to the vent line 3 via the second valve, has a pressure gauge 13 inserted into the reactor 1, and is interposed in an exhaust line 16 connected downstream of the reactor 1. The apparatus has a reactor internal pressure control valve 14 to which a detection signal of the pressure gauge 13 is fed back. The source gas is thermally decomposed on the surface of the substrate 12, and a film having a desired composition is formed on the substrate 12 by controlling the supply amount of each source gas. In the film forming apparatus formed on the surface, a vent line 3 was connected to the reaction furnace 1 at the downstream side thereof to constitute a film forming apparatus.

Then, a film forming apparatus was constructed in which the vent line 3 was connected to the exhaust line 16 between the downstream of the reactor 1 and the reactor pressure control valve 14. The reactor 1 is provided with a partition wall 18.
The interior of the reactor is divided into two regions, an inner region and an outer region. The two regions communicate with each other downstream of the reactor 1, and the main line 2 is connected to the inner region and the vent line 3 is connected to the outer region. Configured.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram illustrating the entire embodiment. FIG. 2 is a diagram showing a cross section of the reactor. 1 and 2, the same reference numerals as those in FIG. 4 denote common members.

In summary, the film forming apparatus of the present invention forms a partition wall 15 in the reaction furnace 1 of the film forming apparatus illustrated and described with reference to FIG. Susceptor 11 on which a substrate 12 on which a substance is to be formed is placed
The main line 2 is connected to the inner region where the fixing is performed, and the vent line 3 is connected to the outer region. Here, the reactor 1 of the film forming apparatus according to the present invention will be described with reference to FIG. 2. The reactor 1 has a closed area defined by an outer wall 18. Reference numeral 19 denotes an end wall which forms a part of the outer wall 18. In the reactor 1, a partition wall 15 is formed coaxially with an outer wall 18, one end of which is connected to an end wall 19 and the other end is open. Thus, the inside of the reaction furnace 1 is divided into two regions: an inner region formed by the partition wall 15 and an outer region formed by the outer wall 18 and the partition wall 15. In the end wall 19, a main gas inlet hole 23 is formed at the center thereof to communicate with the main line 2, and an annular vent gas inlet hole 33 is formed so as to surround the main gas inlet hole 23. To the vent line 3. The susceptor 11 is a partition wall 15
And a substrate 12 on which a substance is to be formed is provided. When the side of the end wall 19 into which the main gas and the vent gas in the reaction furnace 1 constituted by the outer wall 18 are sent is set as the upstream, the downstream in the reaction furnace 1 communicates with the outside via the exhaust line 16. Although not shown,
The reactor 1 is constructed. The outer wall 18 is provided with a handling port for taking in and taking out the substrate 12 into the furnace.

Here, the substrate 12 on which a substance is to be formed is placed on the susceptor 11 in the reactor 1, and the valve 43 and the valve 42 of the first-layer raw material line are switched to flow through the vent line 3. InP of the first layer
Trimethylindium TMT and phosphine PH3, which are source gases for forming a layer, are sent from the main gas inlet hole 23 through the main line 2 to the internal region formed by the partition wall 15 in the reactor 1, and the source material The gas is thermally decomposed to form an InP layer. On the other hand, in the present invention, the source gas for forming the second and subsequent layers is made to flow in the vent line 3 together with the carrier gas.
Through the annular vent gas inlet 33 into the outer region formed by the outer wall 18 and the partition wall 15 in the reactor 1. The main gas and the vent gas sent into the reactor 1 in this manner flow from the upstream to the downstream in the reactor 1 as shown by the arrows, merge at the downstream, and form the reactor internal pressure through the exhaust line 16. The gas is discharged via the control valve 14 and the rotary pump 17.

In the above-described film forming apparatus, the main gas is sent to the internal region of the reactor 1 via the main line 2, and the vent gas is sent to the external region of the reactor 1 via the vent line 3. 1, circulates from upstream to downstream and merges downstream. That is, since the internal region and the external region communicate with each other in the reactor 1, the internal pressure of the reactor 1, the internal pressure in the main line 2, and the vent line 3
Internal pressures are all equal. Therefore, even if the raw material supply line is switched from the vent line to the main line and connected, or vice versa, the total gas flow rate does not change, and the pressure change in the reactor 1 including its internal region does not change in principle. Does not occur.

The inner region and the outer region are defined by a partition wall 1.
Since the partition is formed by the partition 5, the vent gas does not flow into the vicinity of the substrate 12 on which the film to be deposited is to be provided in the internal region, and the composition of the source gas does not change. FIG. 3 is a diagram for explaining another embodiment. In the above embodiment, the partition wall 15 is formed in the reactor 1 so that
The vent line 3 was connected to an inner area for fixing the susceptor 11 on which the substrate 12 on which the substance was to be formed was placed, and an outer area separated from the inner area. In this embodiment, the vent line 3 is not directly connected to the inside of the reactor 1,
It is connected to an exhaust line 16 connected downstream of the reactor 1.

Also in this embodiment, since the inside of the reactor 1 to which the main line 2 is connected and the vent line 3 communicate with each other through the exhaust line 16, the internal pressure of the reactor 1 and the main line 2 and the vent line 3 are equal.
Therefore, as in the case of the previous embodiment, the total gas flow rate does not change even if the raw material supply line is switched from the vent line to the main line, or the reverse switching is performed, and the raw material supply line remains in the reactor 1. No pressure change occurs in principle, including its internal region.

In the case of this embodiment, there is no need to add special measures to the reactor 1, and a conventional reactor can be used as it is.

[0019]

As described above, according to the present invention, the pressure fluctuation in the reactor when the raw material supply line is switched from the vent line to the main line is reduced, and abnormalities at the start of film formation are reduced. Occurrence of composition is prevented.

[Brief description of the drawings]

FIG. 1 illustrates an embodiment.

FIG. 2 is a diagram illustrating a reaction furnace.

FIG. 3 is a diagram illustrating another embodiment.

FIG. 4 is a diagram illustrating a conventional example.

FIG. 5 illustrates the formation of a multilayer film of a semiconductor laser.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reaction furnace 2 Main line 3 Vent line 4 Raw material supply line 11 Susceptor 12 Substrate 13 Pressure gauge 13 'Differential pressure gauge 14 Reactor internal pressure control valve 15 Partition wall 16 Exhaust line 17 Rotary pump 18 Outer wall 19 End wall 23 Main gas inlet hole Reference Signs List 30 Main / vent differential pressure control valve 32 Discharge line 33 Annular vent gas inlet hole 42 Valve 43 Valve

Claims (3)

[Claims] 1. A main line connected to a reaction furnace to supply a raw material gas into the reaction furnace, a vent line through which the raw material gas flows in advance, and connected to the main line through a first valve. It has a plurality of raw material supply lines connected to and connected to a vent line via a second valve, has a pressure gauge inserted into the reactor, and has a pressure gauge interposed in an exhaust line connected downstream of the reactor. Film forming a film having a desired composition on the surface of the substrate by thermally decomposing the material gas on the surface of the substrate and controlling the supply amount of each material gas. A film forming apparatus, wherein a vent line is connected to a reactor at a downstream side thereof. 2. The film forming apparatus according to claim 1, wherein a vent line is connected to an exhaust line between the downstream side of the reactor and a reactor internal pressure control valve. 3. The film forming apparatus according to claim 1, wherein the inside of the reaction furnace is divided into an inner region and an outer region by a partition wall, and both regions communicate with each other downstream of the reaction furnace. A film forming apparatus, wherein a main line is connected to an inner region and a vent line is connected to an outer region.