JPH05175130A - Plasma cvd apparatus - Google Patents

Abstract

PURPOSE:To provide a plasma CVD apparatus in which a deposit by a process gas can be prevented from adhering to the inner wall of a processing chamber. CONSTITUTION:The upper part of a processing chamber 22 is provided with many inflow ports 26 for nitrogen gas. The nitrogen gas flowing into the processing chamber is discharged from an outlet port 24 to the outside in the same way as a process gas. This nitrogen gas becomes a downflow going along the inner wall 28 of the processing chamber 22 to cover this inner wall thinly. When the process gas supplied from a process-gas supply port 20 into the processing chamber approaches the inner wall, the process gas is hindered from reaching the inner wall by the downflow of the nitrogen gas so as to be caused to flow downward and discharged. Therefore, the flow of this thin nitrogen gas becomes a barrier to the process gas so as to greatly decrease the quantity of the process gas reaching the inner wall 28.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to plasma CVD used for forming a thin film of a predetermined substance on a semiconductor wafer.
It relates to the device.

[0002]

2. Description of the Related Art FIG. 3 shows a schematic sectional view of an example of a conventional plasma CVD apparatus. In this apparatus, a semiconductor wafer 10 whose orientation is adjusted is placed on a stage 12, and an upper electrode 1
A high frequency power source 18 is connected between the lower electrode 4 and the lower electrode 16.
Then, a process gas, which is a raw material of the substance to be deposited, is introduced from the gas supply port 20 into the chamber 22, and a high frequency power is applied thereto by the high frequency power supply 18. By doing so, the gas in the chamber is discharged and chemically activated, and reacts with the wafer 10 to form a desired film on the wafer 10. The process gas introduced into the processing chamber 22 is exhausted to the outside through the exhaust port 24.

By the way, when a thin film is formed by the apparatus as shown in FIG. 3, not only a thin film is formed on the wafer 10, but also the inner wall of the processing chamber 22 is peculiar to the process gas used. The substance becomes a solid and precipitates. This deposit causes dust generation during wafer processing, and when it adheres to the wafer, the characteristics of the finally obtained device are significantly deteriorated.

In the conventional apparatus, as a method for preventing such dust generation, a method of periodically plasma-cleaning the apparatus is adopted. In this method, oxygen is sent into the processing chamber 22 to cause electric discharge, so that the oxygen and the deposits on the inner wall are combined with each other, and this is discharged to the outside to remove the deposits from the processing chamber. Also,
It is also practiced to remove the processing chamber from the apparatus when it is extremely dirty and to soak it in a chemical solution to chemically remove the deposit.

[0005]

However, a deposit is formed on the inner wall of the chamber even during the thin film formation, and the deposit does not generate dust on the devices being processed simultaneously. This may cause deterioration of the characteristics of the device. However, with conventional devices,
Since the work of removing the deposits can be performed only during the period when the thin film forming process is not performed on the wafer,
It is not possible to prevent the influence of the precipitate generated during the thin film formation on the device that is being simultaneously subjected to the CVD treatment.

Further, in the conventional apparatus, in order to minimize the adverse effect of the precipitates generated during the thin film forming process, it is necessary to frequently perform the deposit removal work such as plasma cleaning. For this reason, there is a problem that maintenance of the device requires considerable cost and labor, and is inconvenient to handle.

The present invention has been made in view of the above circumstances, and provides a plasma CVD apparatus capable of preventing deposits from being formed on the inner wall of a processing chamber during the formation of a thin film. The purpose is that.

[0008]

In order to achieve the above-mentioned object, a plasma CVD apparatus according to the present invention is arranged such that the inlet and outlet of the barrier gas are treated so that the barrier gas flows along the inner wall of the treatment chamber. The barrier gas is provided in the chamber, and the barrier gas is caused to flow from the inflow port to the discharge port during a period in which the CVD process is performed in the processing chamber.

[0009]

According to the present invention, the gas flow acts as a barrier by flowing a barrier gas such as an inert gas or nitrogen gas from the inlet to the outlet along the inner wall of the processing chamber. It prevents the process gas from approaching the inner wall of the processing chamber and thus reduces the amount of material deposited on the inner wall of the processing chamber. Also,
Even if a deposit is formed on the inner wall of the processing chamber and is separated, the separated deposit is carried to the outside from the outlet by the gas flow. Therefore, the separated deposits can be prevented from falling onto the wafer.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a plasma C which is an embodiment of the present invention.
It is a schematic sectional drawing of a VD apparatus. In the figure, the same components as those of the plasma CVD apparatus of FIG. 3 are designated by the same reference numerals, and detailed description thereof will be omitted.

The apparatus shown in FIG. 1 is different from that shown in FIG. 3 in that a nitrogen gas inlet 26 is provided in the upper part of the processing chamber 22, and nitrogen gas is introduced from here to the inner wall 28 of the processing chamber 22. That is, the nitrogen gas was made to flow downward along the line. The inflowing gas is discharged to the outside through the same outlet 24 as the process gas. Outlet 2
The pipe of No. 4 is provided with a butterfly check valve, and has a structure in which a gas flowing from the processing chamber 22 to the outside can pass, but a gas flow in the reverse direction cannot pass.

FIG. 2 is a schematic plan view of the inflow port. As shown in FIG. 2, a large number of inflow ports 26 are provided along the circumference of the circular processing chamber 22. The inner wall 28 of the processing chamber 22 is covered with a thin gas flow film of nitrogen gas by causing nitrogen gas to flow downward from the multiple inlets 26 and causing downflow of the nitrogen gas. When the process gas supplied from the process gas supply port 20 into the processing chamber 22 approaches the inner wall 28, it is caused to flow downward by the gas flow of the nitrogen gas. Therefore, this thin nitrogen gas flow acts as a barrier against the process gas, and the amount of the process gas reaching the inner wall 28 is significantly reduced. As a result, precipitates due to the process gas are less likely to be generated on the inner wall.

With the above structure, the amount of the substance deposited on the inner wall 28 of the processing chamber 22 is greatly reduced. Even if a deposit due to the process gas is generated on the surface of the inner wall 28 and peels off from the inner wall 28, the peeled deposit is discharged to the outside by the downflow of nitrogen gas along the inner wall 28. It does not fall on 10. Therefore, in the finally obtained device, the probability of occurrence of characteristic deterioration due to precipitates is significantly reduced.

When the nitrogen gas is introduced into the processing chamber 22 through the inlet 26, the effect as a barrier for preventing the process gas from approaching the inner wall of the processing chamber cannot be enhanced unless the flow velocity and the flow rate of the nitrogen gas are sufficient. Also, it cannot play the role of discharging the deposited substance to the outside. Further, if the flow rate and flow rate of the nitrogen gas are not sufficient, there is a risk that the nitrogen gas mixes with the process gas in the central portion of the processing chamber and the original CVD process cannot be performed. Therefore, when injecting nitrogen gas, it is necessary to select an appropriate speed and flow rate in consideration of the above points.

As described above, in the plasma CVD apparatus of this embodiment, it is possible to effectively prevent deposits resulting from the process gas from forming on the inner wall of the processing chamber. For this reason, the number of periodical plasma cleanings and treatments with a chemical solution, which are required in the conventional apparatus, can be greatly reduced, so that the apparatus can be easily maintained and the cost required for the maintenance can be reduced.

In this embodiment, an example in which nitrogen gas is used as a gas to be introduced into the chamber has been described. However, as is clear from the description of the above embodiment, nitrogen gas serves as a barrier against the process gas. However, other than nitrogen gas can be used as long as it has the same action. However, those that affect the CVD reaction must be avoided. From this point of view, an inert gas such as helium or argon can be used instead of the nitrogen gas. Also, specific CVD
Other gases can be used in the same manner as the barrier gas as long as they have no effect on the reaction.

[0017]

As described above, according to the present invention, a barrier gas is made to flow from the inlet to the outlet along the inner wall of the processing chamber, and this gas flow serves as a barrier, and the process gas becomes the inner wall of the processing chamber. Can be prevented, and even if a deposit is formed on the inner wall of the processing chamber and is peeled off, the deposit is discharged to the outside from the discharge port by the gas flow, and the deposit is removed on the wafer. Can be prevented from falling. As a result, it is possible to prevent the characteristics of the device finally obtained from being deteriorated by the deposit of the process gas. Furthermore,
Since the amount of substances deposited on the inner wall of the processing chamber is significantly reduced, it is not necessary to perform frequent plasma cleaning or chemical treatment unlike the conventional apparatus, and therefore it is easy to maintain and the cost is reduced. A device can be provided.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a plasma CVD apparatus that is an embodiment of the present invention.

FIG. 2 is a schematic plan view of a plurality of gas inlets provided around a processing chamber.

FIG. 3 is a schematic sectional view of an example of a conventional plasma CVD apparatus.

[Explanation of symbols]

 10 Semiconductor Wafer 12 Stage 14 Upper Electrode 16 Lower Electrode 18 High Frequency Power Supply 20 Process Gas Supply Port 22 Processing Chamber 24 Exhaust Port 26 Gas Inlet Port 28 Inner Wall

Claims (2)

[Claims] 1. An inlet and an outlet for the barrier gas are provided in the processing chamber so that the barrier gas flows along the inner wall of the processing chamber, and the inlet is provided during a period in which a CVD process is performed in the processing chamber. A plasma CVD apparatus, wherein the barrier gas is flown from the discharge port to the discharge port. 2. The plasma CVD apparatus according to claim 1, wherein the barrier gas is an inert gas or a nitrogen gas.