JPH0756864B2 - Epitaxy vapor phase growth equipment - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to an improvement of a reduced pressure type epitaxial vapor phase growth apparatus equipped with a load lock mechanism and capable of exchanging wafers in vacuum.

[Prior art]

In the metalorganic pyrolysis method (MOCVD or OMVPE), a source gas is supplied to a heated substrate on a susceptor to cause a gas phase reaction in the vicinity of the substrate and a thin film of the reaction product is formed on the substrate. To do. A thin film is formed on the susceptor in the growth chamber, but when the growth of one substrate is completed, it must be replaced with the next substrate. Substrate replacement must be frequent. It is inefficient to open the growth room each time, and the growth room is easily contaminated and dangerous. Therefore, an apparatus was provided in which a load lock mechanism was provided in the growth chamber so that the substrates could be exchanged in a vacuum (see, for example, JP-A-63 / 1988).
-118834, JP-A-63-299115). A device having a load lock mechanism is efficient because a plurality of substrates can be continuously replaced in a vacuum. Also, it is not necessary to open the growth chamber for substrate exchange. There are various formats. For example, there is one in which a transfer chamber that can be shut off from the growth chamber by a gate valve is provided, a substrate is placed in the transfer chamber, and the substrate is transferred onto a susceptor in the growth chamber by a transfer mechanism. The transfer chamber can be evacuated, and the space is evacuated before the substrate is transferred. Alternatively, in addition to the transfer chamber, a substrate exchange chamber connected to the transfer chamber via a gate valve may be provided. The substrate exchange chamber can accommodate a plurality of wafers in a tray.
The multiple trays are arranged in shelves arranged one above the other and can be raised and lowered as a whole. A plurality of wafer trays are put into the substrate exchange chamber from the atmosphere and a vacuum is drawn. Open the gate valve and lift the tray into the transfer chamber. The transfer mechanism transfers the substrate as a tray to the susceptor in the growth chamber. This is the first operation. In reality, since the growth is performed continuously, after the second wafer, the wafer tray of the grown wafers on the susceptor is taken out by the transfer mechanism and placed on the empty shelf. Thereafter, the wafer tray of unprocessed wafers is transferred onto the susceptor in the growth chamber by the transfer mechanism. The gate valve in the growth chamber is closed, the transfer mechanism is returned, the shelf containing the wafer tray is returned to the substrate exchange chamber, and the gate valve is closed. After this, a thin film is formed in the growth chamber. A vapor phase growth apparatus having three spaces such as a growth chamber, a transfer chamber and a substrate exchange chamber has also been proposed. This is efficient because a plurality of wafers can be successively processed.
After first inserting multiple wafer trays into the substrate exchange chamber,
All substrates are transferred in a vacuum without being exposed to the atmosphere in the substrate exchange chamber and the transfer chamber. As there are three rooms, there are such convenient points.

[Problems to be Solved by the Invention]

Although the three-chamber vapor-phase growth apparatus is efficient, it is a story compared to the conventional one. This still has an efficiency problem. That is, the processing time per substrate is too long. The substrate is in the substrate exchange room at room temperature. Naturally, it is transported at room temperature. All heat-related processes take place in the growth chamber. The growth room is overloaded with time. Therefore, the processing time per substrate becomes too long. This will be described in more detail. Substrates brought to the growth chamber susceptor at room temperature must be heated to the proper growth temperature. The required temperature is 600 ℃ to 850, depending on the thin film to be grown.
It is about ℃. This heating is done by a resistance heater inside the susceptor or a high frequency heating coil outside the growth chamber. The time T ₁ required for this temperature raising process is about 20 to 30 minutes. After that, a thin film is grown on the substrate through raw material processing. This also depends on the thin film material and the desired film thickness, but for example,
It may take time. It can be shorter or longer.
For simplicity, the time required for the growth process T _{2 is set} to 1 hour. When the growth is completed, the electric power of the heater or the high frequency coil in the susceptor is weakened, or the electric power supply is cut off to gradually cool the substrate on the susceptor. The susceptor is often made of carbon but has a much larger heat capacity than the substrate or wafer tray. Therefore, it takes a long time to cool the susceptor.
The time T ₃ required for this cooling process is, for example, about 90 minutes. The time required for each process of temperature rising, growth, and cooling is (T ₁ +
T ₂ + T ₃ ). During this time, the susceptor is occupied by one wafer (substrate) tray. Even if the time for substrate transfer is ignored, the processing time per substrate is (T ₁ + T ₂ + T ₃ ), which is long. In the previous example, this would be about 3 hours. Throughput cannot be further increased unless the processing time per substrate is shortened. There is a strong demand for higher efficiency devices. All three processes of temperature rising, growth and cooling are performed on the susceptor in the growth chamber. This is the reason why the processing time is lengthened. If you think carefully, the temperature rise and cooling do not have to be performed in the growth chamber. These processes should be possible in another space. An object of the present invention is to provide a vapor phase growth apparatus having a load lock mechanism and having a three-chamber structure including a growth chamber, a transfer chamber, and a substrate exchange chamber, and capable of shortening the processing time per sheet. Is.

[Means for Solving the Problems]

A preheating device for heating an unprocessed wafer and a gradual cooling device for gradual cooling of the processed wafer are provided inside the transfer chamber. Then, the unprocessed wafer is preheated and sent to the growth chamber, and the processed wafer that has finished growing is removed from the susceptor while it is still hot and is annealed by the annealer. This is a novel point of the vapor phase growth apparatus of the present invention. That is, the epitaxial vapor phase growth apparatus of the present invention has a processing chamber for introducing raw material processing and a gas chamber for exhausting exhaust gas, which can be evacuated to a vacuum chamber, and can be rotated up and down in the chamber. A susceptor on which a wafer tray for holding wafers should be placed, a heating device for heating the susceptor and the wafer, and a gate valve that is connected to the growth chamber and can be evacuated to convey the wafer tray. A transfer chamber that is a space, a transfer mechanism that transfers a wafer tray that holds wafers between the transfer chamber and the growth chamber, and a transfer valve that is continuously installed in the transfer chamber via a gate valve and can be evacuated to multiple wafer trays. A substrate exchange chamber capable of accommodating a wafer, a cassette provided in the substrate exchange chamber having a plurality of shelves for placing wafer trays, and a substrate exchange chamber. A cassette table for holding the loaded cassette, a cassette moving device for moving the cassette table between the transfer chamber and the substrate exchange chamber, and a wafer tray for holding unprocessed wafers provided inside the transfer chamber for temporary retention. It comprises a preheating device for preheating the wafer and a slow cooling device provided inside the transfer chamber for temporarily retaining the wafer tray for holding the processed wafer and gradually cooling the wafer.

[Action]

A cassette containing a plurality of wafer trays is provided in the substrate exchange chamber. After the substrate exchange chamber and the transfer chamber are once evacuated, they are brought to an appropriate pressure and atmosphere. The atmosphere is
H ₂ , N _2, etc. The growth chamber is also kept at an appropriate pressure atmosphere. Open the gate valve in the substrate exchange chamber and move the cassette to the transfer chamber. One wafer tray is transferred by the transfer mechanism and placed on the preheating device. Here preheated to a suitable temperature T _a. The gate valve in the growth chamber is opened, and the preheated wafer tray is placed on the susceptor in the growth chamber by the transfer mechanism. Return the transport mechanism and close the gate valve. A source gas is flowed toward the wafer in the growth chamber to grow a thin film on the wafer. It is kept at the growth temperature T _b . After the growth, heating is stopped, so the temperature of the wafer drops, but
At a certain temperature _Tc higher than room temperature, the gate valve is opened and the wafer tray is taken out. The wafer tray is removed from the susceptor by the transfer mechanism and placed in the slow cooling device. T _{c with} slow cooling device
To room temperature T ₀ . Thereafter, the wafer tray holding the processed wafer is returned to the cassette. The above is focused on one wafer. In reality, several wafer trays move, so the operation is rather complicated. Preheating and slow cooling are performed outside the growth chamber. What is done in the growth chamber is thin film growth and final heating ( _Ta →
T _b ), initial slow cooling (T _b → T _c ). The time T ₄ required for this is shorter than the above (T ₁ + T ₂ + T ₃ ). T ₄ is
Although it is larger than T _2, but shorter than (T ₁ + T ₂ + T ₃ ), the processing time per wafer is shortened. The processing time per wafer is T ₄ in this configuration, and most of T ₁ and T ₃ are not included in the processing time.

【Example】

FIG. 1 is a schematic sectional view of a vapor phase growth apparatus according to an embodiment of the present invention. A susceptor 3 is rotatably and vertically movable in a vertically long growth chamber 5. A rotating shaft 4 supports the susceptor 3 so as to be rotatable and vertically movable. A resistance heater is provided in the susceptor 3 to heat the susceptor 3, the wafer tray 2, and the wafer 1. The growth chamber can be evacuated. Gas inlet port 20 at the top of growth chamber 5 and gas outlet port 21 at the bottom
There is. The raw material gas enters the growth chamber through the gas inlet 20.
The source gas flows from the top to the bottom in the growth chamber, and a gas phase reaction occurs in the vicinity of the wafer 1. Reaction products are deposited on the surface of the wafer 1. The exhaust gas is discharged from the gas outlet 21. Behind this is a vacuum exhaust device. The raw material gas varies depending on the product, but when a thin film such as GaAs or AlGaAs is formed, it is an organic metal gas containing Ga, Al, etc., or a mixed gas of AsH ₃ , H _2, etc. The ratio of H ₂ which is the carrier gas is the largest. A transfer chamber 7 is provided following the growth chamber 5 via a gate valve 6. A horizontally long space is provided to transfer the wafer tray. The transfer chamber 7 can also be evacuated. A transfer arm 8 is provided for moving the wafer tray between the transfer chamber and the growth chamber. It can move horizontally. It has the same mechanical structure as the conventional transport mechanism. However, according to the present invention, since the wafer tray is transported at a high temperature, the transport mechanism must be made of a material that can withstand the high temperature. A substrate exchange chamber 9 is provided following the transfer chamber 7 via a gate valve 12. The substrate exchange chamber 9 can also be evacuated. A cassette 11 having a shelf for accommodating a plurality of wafer trays is placed on a cassette table 10 in the substrate exchange chamber 9. The cassette can be moved between the substrate exchange chamber 9 and the transfer chamber 7 by the cassette moving device 16. The direction of movement may be vertical or horizontal. In this example, it is supposed to move vertically. This is because the substrate exchange chamber 9 is provided below the transfer chamber 7. If the substrate exchange chamber 9 is provided on the side of the transfer chamber 7, the movement direction becomes horizontal. Next, a characteristic part of the present invention will be described. A preheating device 18 and a slow cooling device 19 are provided in the middle of the transfer chamber 7. The preheating device 18 moves the unprocessed wafer from room temperature T ₀ to a certain temperature T
It is intended to preheated to _a. If GaAs substrate, T
_a is about 400 ° C., which is a temperature at which As does not come off. The preheating device 18 includes a lamp heater 13 and a heating table 14. The lamp heater is, for example, an infrared lamp. When a wafer is placed on the heating table 14 together with the wafer tray, it is preheated by the heat of the heater. The slow cooling device 19 slowly cools the wafer which is still high temperature after the thin film formation. It is cooled by T _c → T ₀ . T _c
Is about 400 ° C for a GaAs substrate. It is gradually cooled to room temperature T ₀ . The slow cooling device 19 includes a cooling table 15 and a lamp heater 13. This lamp heater is for avoiding the rapid cooling of the wafer. The wafer power can be gradually cooled while gradually reducing the power of the heater. Instead of the lamp heater 13, a resistance heating heater or a high frequency heating coil may be used. In this figure, the preheating device 18 and the slow cooling device 19 are arranged close to each other, but they can be provided separately. The heating table 14 and the cooling table 15 are for placing the wafer tray, but these can be raised and lowered. When in the raised position, the transfer arm 8 and the wafer tray can be exchanged. The wafer tray can be transferred from the transfer arm 8 to the heating table 14 or the cooling table 15, or the wafer tray can be transferred from the heating table or cooling table to the transfer arm. When in the lowered position, they do not interfere with the movement of the transport arm 8. The heating table 14 and the cooling table 15 are in the lowered position except when the wafer tray is replaced. With the above configuration, the operation is as follows. In order to distinguish between the wafer trays, the wafer trays (or wafers) are referred to as A, B, C, D, E. The first wafer A has been processed and returned to room temperature (T ₀ ) and returned to the cassette 11. The second wafer B has been subjected to the thin film forming process, but is cooled on the slow cooling table 15 (T _C → T ₀ ). The third wafer C is on the susceptor 3 in the growth chamber 5 during the thin film forming process (T _b ). The fourth wafer D is placed in the heating table 15 during preheating (T ₀ → T _a ). In the cassette 11, the seats for wafers B, C, and D are vacant. Thus, the three wafers B, C, D are in some process at the same time. Thereafter, the transfer arm 8 transfers the wafer B from the cooling table 15 to the cassette 11, the growth chamber is opened and the susceptor is lowered, and the transfer arm 8 transfers the wafer C to the cooling table 15. Before opening the growth chamber, the atmosphere thereof should be matched with that of the transfer chamber 7. Further, the wafer D on the heating table 14 is carried on the susceptor by the carrying arm 8. The growth chamber is closed and a vacuum is drawn to create an appropriate atmosphere, and the wafer D is further heated (T _a → T _b ) to start thin film growth. Further, the wafer E is taken out from the cassette and placed on the heating table 14. Thin film growth is performed in this state. This time is T ₄ . The time required for preheating and gradual cooling is shorter than the time for final heating, thin film growth ( _Ta → _Tb → _Tc ), and initial cooling.
T ₄ is determined by the time required for final heating in the growth chamber, thin film growth, and initial cooling. For example, in the case of a GaAs substrate, T _a = T _c = 400 ° C., T _b = 700
At ˜800 ° C., the initial cooling of T _b → T _c is about 30 minutes. If the final heating (T _a → T _b ) is 10 minutes and the growth time is 1 hour, T ₄ is about 1 hour and 40 minutes. In the conventional method, T ₁ = 20 to 30 minutes, T ₂ = 60 minutes, T ₃ = 90 minutes, and T ₁ + T ₂ + T ₃ = 170 to 180 minutes.
Compared with this, according to the present invention, about 1/2 time is required.

【The invention's effect】

(1) Conventionally, after the film formation is completed, the wafer is cooled to room temperature on the susceptor in the growth chamber before being unloaded. Due to the large heat capacity of the susceptor, a long cooling time was required. However, in the present invention, when the wafer is at a considerably high temperature (T _c ), it is taken out and conveyed at a high temperature as it is on the cooling table. Cooling takes time here. Therefore, the use time of the growth chamber can be reduced to less than half of the conventional one. Therefore, the processing time per wafer is greatly reduced. (2) Since the next wafer is preheated during film formation, the time for heating the wafer in the growth chamber is shortened. (3) Preheating is performed in the transfer chamber, and baking is performed here. The degassed clean wafer tray transports into the growth chamber so it does not get dirty. A higher-purity film can be formed. Conventionally, since the wafer tray is heated inside the growth chamber, there is a possibility that the degassing component may contaminate the inside of the growth chamber.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an epitaxial vapor phase growth apparatus according to an embodiment of the present invention. 1 ... Wafer, 2 ... Wafer tray 3 ... Susceptor, 4 ... Rotating shaft 5 ... Growth chamber, 6 ... Gate valve 7 ... Transfer chamber, 8 ... Transfer arm 9 ... Substrate exchange chamber, 10 ... … Cassette stand 11 …… Cassette, 12 …… Gate valve 13 …… Lamp heater, 14 …… Heating stand 15 …… Cooling stand, 16 …… Cassette moving device 17 …… Shelves, 18 …… Preheating device 19 …… Annealing device, 20 …… Gas inlet 21 …… Gas outlet

Claims (1)

[Claims] 1. A growth chamber having a gas inlet for introducing a source gas and a gas outlet for discharging an exhaust gas, which can be evacuated to a vacuum, and a wafer which is rotatably lifted in the growth chamber and holds a wafer. A susceptor on which the wafer tray should be placed, a heating device for heating the susceptor and the wafer, and a transfer chamber that is a space that is continuously provided to the growth chamber via a gate valve and that can be evacuated to vacuum to transfer the wafer tray,
A transfer mechanism for transferring the wafer tray holding the wafer between the transfer chamber and the growth chamber, and a substrate exchange chamber capable of accommodating a plurality of wafer trays that are continuously provided in the transfer chamber via a gate valve and can be evacuated to a vacuum. A cassette having a plurality of shelves for placing wafer trays provided in the substrate exchange chamber, a cassette table provided in the substrate exchange chamber for holding the cassette, and a cassette table of the transfer chamber and the substrate exchange chamber. Between the cassette moving device, the preheating device provided inside the transfer chamber for temporarily preserving the wafer tray that holds the unprocessed wafers, and the processed wafer provided inside the transfer chamber. An epitaxial vapor phase growth apparatus comprising: a slow cooling device that temporarily holds a held wafer tray and gradually cools a wafer.