JP2013008770A - Deposit cleaning method for film deposition apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for cleaning away a deposit having deposited on a film deposition apparatus for forming a thin film on a semiconductor substrate.SOLUTION: The method for cleaning away a deposit having deposited on a film deposition apparatus comprises: supplying a hydrogen-based cleaning gas containing hydrogen or a hydrogen-argon mixed gas into a deposition chamber with a substrate stage temperature kept at a temperature when the chamber is unheated to a temperature of 400°C, and more preferably at 200 to 400°C; and using pulsed plasma, which is generated by a pulse power supply unit applying an electric power to an electrode placed in the deposition chamber, to act on a wall face part inside the deposition chamber.

Description

  The present invention relates to a deposit cleaning method in a film forming system for forming a thin film such as a silicon film on a semiconductor substrate, and more particularly to a method for cleaning a deposit generated in a solar cell manufacturing process.

Conventionally, in a CVD film forming apparatus, silicon-based deposits that accompany film formation adhere to the inner surface of the chamber and the surface of the susceptor. In order to remove the deposited deposit, a cleaning gas containing a halogen gas such as NF ₃ is used. However, the conventional halogen-based cleaning gas has a large environmental load, and has a problem in that it requires a great cost to process the removed cleaning gas.

  Therefore, in recent years, a technique has been proposed in which the inside of a chamber is cleaned by using hydrogen-argon gas and applying a potential between electrodes arranged in the chamber (Patent Document 1).

Special table 2007-535119 gazette

  Since the cleaning technique using hydrogen-argon uses high frequency induction plasma (ICP), there is a problem that the apparatus becomes large and the running cost is expensive. For this reason, there has been a problem that it is difficult to use in the manufacture of a semiconductor substrate (for example, a solar cell panel) that does not require a high degree of lamination.

Further, the hydrogen - a cleaning technique using argon, hydrogen - while gas costs argon are inexpensive and few hundredths 1 degree of NF _3, in which the cleaning rate was used NF ₃ as a cleaning gas Compared to 1/1000 (several nm / min), and the product of cost and cleaning rate, there is a problem that the combination of high frequency induction plasma and cleaning gas cannot demonstrate sufficient capability as a cleaning method. there were.

  SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide an optimum cleaning method for a semiconductor substrate deposition apparatus that does not require a high degree of lamination.

In order to achieve the above object, the invention described in claim 1 is directed to cleaning deposits attached to a film forming apparatus for forming a thin film on a semiconductor substrate.
A pulse generated by supplying a hydrogen-based cleaning gas into a film forming chamber in which the temperature of the substrate stage is maintained at a non-heated state to 400 ° C., and applying power from a pulse power supply device to an electrode disposed in the film forming chamber. The plasma is applied to the wall surface portion in the film forming chamber to clean the deposits attached to the film forming apparatus.

  The invention according to claim 2 is characterized in that the hydrogen-based cleaning gas used in the method according to claim 1 is a hydrogen-argon mixed gas, and the invention according to claim 3 is a method according to claim 1. The hydrogen-based cleaning gas used in the step is hydrogen gas.

  In the present invention, by applying power from the pulse power supply device to the electrode disposed in the film forming chamber, gas plasma can be applied in a pulsed manner, and deposits adhering to the film forming device are cleaned at a micrometer level. can do.

  High-frequency induction plasma (ICP) requires precise vacuum control because it can only be used in a vacuum atmosphere of 10 Torr or less, but pulsed plasma can be used in a wide range from vacuum to atmospheric pressure, so rough pressure control Therefore, there is an advantage that a constant plasma can be obtained and handling is easy.

  Since pulsed plasma can use a DC power source, the system can be constructed at low cost, and the plasma intensity can be easily changed by selecting the pulse width and duty ratio.

Furthermore, since the present invention has a large cleaning rate and the product of the cost and the cleaning rate is larger than that of NF ₃ , the present invention has a sufficient capability as an alternative technique for a conventional cleaning method using a halogen-based cleaning gas.

  In addition, in the present invention, since the gas species acting as plasma is hydrogen alone, or hydrogen and argon, the environmental load is small and the running cost can be suppressed.

The figure is a schematic configuration diagram of an experimental apparatus used in the cleaning method of the present invention.

  This experimental apparatus includes a vacuum vessel (1), a pair of electrodes (2) arranged in a state of being opposed to each other in the vacuum vessel (1), and a pulsed plasma generation power supply device that supplies power to the electrodes (2) ( 3) and a vacuum pump (4) communicating with the inside of the vacuum vessel (1).

  A commercial power source (not shown) is connected to the pulsed plasma generating power source device (3). In addition, the electrodes (2) are made of circular stainless steel, and the upper electrode (2u) is cooled by a cooling device to prevent destruction by heat, and the lower electrode (2d) is easy to clean. In addition, the heater is heated.

  A ceramic plate (5) as an insulator is placed on the lower electrode (2d), a 10 mm hole is formed in the center of the ceramic plate (5), and a silicon wafer (6) as a treatment material is placed thereon. installed. In addition, in order to prevent creeping discharge on the outside of the silicon wafer (6), Kapton tape was stuck around and fixed.

  The distance (gap) between the pair of electrodes is adjustable between 10 mm and 90 mm, and this time, the experiment was performed with the distance fixed to 30 mm.

  In an experiment using the experimental apparatus having the above-described configuration, a silicon wafer (6) as a processing material is placed on the ceramic plate (5) in the vacuum vessel (1), and the vacuum vessel (1) is sealed. After operating the rotary vacuum pump (4) to evacuate the vacuum vessel (1), hydrogen-argon gas is supplied up to 200 Pa, and hydrogen is used under low pressure using a pulsed plasma generation power supply (3). + Argon plasma was generated, and the p-silicon film was cleaned using the gas ratio and the substrate stage temperature as parameters.

Samples 1 to 7 were subjected to plasma treatment under the conditions shown in Table 1, and the cleaning rate was calculated from the measurement results of a high-frequency glow discharge luminescence surface analyzer (GDS). Using a silicon nitride film (0.3 μm) + p-silicon film (1.0 μm) formed on a silicon wafer as a sample sample, the time from the start of detection of p-silicon to the measurement of nitrogen Is defined as the cleaning time.
The experimental conditions were set as follows.
Electrode gap: 30mm
Atmospheric pressure: 200 Pa
Pulse width / period: 40 μs / 200 μs
Voltage: 1.0 kV
Processing time: 3min

  Table 2 summarizes the GDS measurement results.

For untreated Si, the cleaning time is 26.0 sec, so it can be seen that 26.0 sec is required for the measurement of p-Si with a thickness of 1 μm. For samples No. 1 to No. 7,
Cleaning depth: x (μm) = 1− (cleaning time / 26.0)
Cleaning rate: c (μm / min) = x / 3
Is required.

  Table 3 shows the cleaning rate superimposed on a table using the substrate temperature and the mixed gas ratio as parameters.

  As a result, the best cleaning rate was 0.112 μm / min. The conditions at that time were a hydrogen: argon ratio of 9: 1 and a substrate heating temperature of 300 ° C. A cleaning rate on the order of 100 nanometers could be obtained.

  In each of the above experimental examples, the substrate stage temperature was heated to 200 ° C., 300 ° C., and 400 ° C. However, in actual work, the substrate stage temperature may be set at the immediately preceding substrate stage temperature (non-heated state).

  The present invention is suitable for cleaning a semiconductor substrate film forming apparatus, particularly a solar cell panel film forming apparatus, because it has a low environmental load and a high cleaning rate.

Claims (5)

In cleaning the deposits attached to the film forming device that forms a thin film on a semiconductor substrate,
A pulse generated by supplying a hydrogen-based cleaning gas into a film forming chamber in which the temperature of the substrate stage is maintained at a non-heated state to 400 ° C., and applying power from a pulse power supply device to an electrode disposed in the film forming chamber. A deposit cleaning method in a film forming apparatus in which plasma is applied to a wall surface portion in a film forming chamber to clean the deposits attached to the film forming apparatus.   2. The deposit cleaning method for a film forming apparatus according to claim 1, wherein the hydrogen-based cleaning gas is a mixed gas of hydrogen gas and argon gas.   The deposit cleaning method in the film forming apparatus according to claim 1, wherein the hydrogen-based cleaning gas is hydrogen gas.   The method for cleaning deposits in a film forming apparatus according to any one of claims 1 to 3, wherein the temperature of the substrate stage is maintained at 200 ° C to 400 ° C during cleaning.   The method for cleaning deposits in a film forming apparatus according to claim 1, wherein the semiconductor substrate is a solar cell substrate.

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