JP2012199473A - Thin film deposition apparatus and thin film deposition method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin film deposition apparatus which can stably deposit a microcrystalline silicon thin film of high crystallinity on a substrate.SOLUTION: A thin film deposition apparatus forming a thin film on a substrate, comprises: a deposition container; a silane gas supply part supplying a silane gas that is a material of the thin film to the deposition container; a diluent gas supply part supplying a diluent gas diluting the silane gas to the deposition container; a plasma generation part generating a plasma inside the deposition container; a silicon base material arranged inside the deposition container; and a control part controlling timing that the silane gas supply part supplies the silane gas and timing that the diluent gas supply part supplies the diluent gas.

Description

  The present invention relates to a thin film forming apparatus and a thin film forming method for forming a thin film on a substrate using plasma.

Conventionally, a CVD (Chemical Vapor Deposition) apparatus is used to form a thin film on a substrate. In particular, a process of forming a Si thin film used for a thin film solar cell or TFT (Thin Film Transistor) on a glass substrate by using a CVD apparatus has attracted attention. In the formation of the Si thin film, for example, monosilane (SiH ₄ ) is turned into plasma to form the Si thin film on the glass substrate. In recent years, thin-film solar cell panels have been increased in size, and it is desired to form a microcrystalline Si thin film having high quality characteristics and uniform characteristics on a large glass substrate at low cost.

  For example, in order to reduce the manufacturing cost when forming the microcrystalline Si thin film, it is desired that the temperature of the substrate on which the film is formed be 250 ° C. or lower. However, when a microcrystalline Si thin film is formed at a substrate temperature of 250 ° C. or lower, there is a problem in characteristics of the microcrystalline Si thin film, such that the crystallinity of the thin film is poor and the carrier mobility is low.

On the other hand, a method for forming a high-quality microcrystalline silicon thin film as compared with the prior art is known (Non-Patent Document 1).
In this method, the flow rate of H ₂ gas is 150 sccm and the flow rate of SiH ₄ gas is 0 sccm in the nucleation step, and the flow rate of H ₂ gas is 150 sccm and the flow rate of SiH ₄ gas is 25 sccm in the microcrystalline silicon growth step. Thus, it is described that Si is nucleated on the SiO ₂ substrate.

Japanese Journal of Applied Physics Vol. 43, No. 12, 2004, pp. 7909-7933, Low-Temperature Microcrystalline Silicon Film Deposited by High-Density and Low-Potential Plasma Technique Using Hydrogen Radicals

In the above method, since the Si thin film deposited on the inner wall of the film formation container is sputtered by hydrogen atoms or hydrogen radicals in the nucleation step, Si nuclei are formed without flowing SiH ₄ gas. It is believed that.

  However, this method has a problem that, in the nucleation step, the characteristics of the thin film formed on the substrate change due to the distribution of the Si thin film deposited on the inner wall of the film forming container, and thus it is difficult to form a stable film. is there.

  Accordingly, an object of the present invention is to provide a thin film forming apparatus and a thin film forming method capable of stably forming a highly crystalline microcrystalline silicon thin film on a substrate.

  In order to solve the above problems, a thin film forming apparatus of the present invention is a thin film forming apparatus for forming a thin film on a substrate, and a silane gas that supplies a film forming container and a silane gas that is a raw material of the thin film to the film forming container A supply unit, a dilution gas supply unit for supplying a dilution gas for diluting the silane gas to the film formation container, a plasma generation unit for generating plasma in the film formation container, and an inside of the film formation container. And a control unit that controls a timing at which the silane gas supply unit supplies the silane gas and a timing at which the dilution gas supply unit supplies the dilution gas.

  Moreover, it is preferable that the said film-forming container is equipped with the support part which supports the said silicon base material.

  The thickness of the silicon substrate is preferably 1 mm or more.

  In addition, the controller may supply the silane gas supply unit and the dilution gas supply unit so as to supply the silane gas and the dilution gas to the film formation container after supplying only the dilution gas to the film formation container. It is preferable to control.

  The dilution gas is preferably hydrogen gas.

  In order to solve the above-mentioned problem, a thin film forming method of the present invention is a thin film forming method for forming a thin film on a substrate, wherein a dilution gas is supplied to a film forming container in which a silicon substrate is disposed. 1 film forming process, a second film forming process for supplying silane gas and the dilution gas to the film forming container, and a plasma generating process for generating plasma of the diluting gas inside the film forming container. It is characterized by.

  The thickness of the silicon substrate is preferably 1 mm or more.

  The dilution gas is preferably hydrogen gas.

  The first film formation step further supplies the silane gas to the film formation container, and the flow rate of the silane gas supplied to the film formation container in the first film formation step is the same as that in the second film formation step. The flow rate is preferably less than the flow rate of the silane gas supplied to.

  According to the present invention, a highly crystalline microcrystalline silicon thin film can be stably formed on a substrate.

It is a schematic block diagram which shows an example of the thin film formation apparatus of embodiment. It is a flowchart which shows an example of the thin film formation method of embodiment.

<First Embodiment>
(Configuration of thin film forming apparatus)
First, with reference to FIG. 1, the structure of the thin film formation apparatus of this embodiment is demonstrated. FIG. 1 is a schematic configuration diagram showing an example of a thin film forming apparatus of the present embodiment. The thin film forming apparatus 10 of the present embodiment can supply a film forming gas into a film forming container and generate plasma, and forms a thin film of microcrystalline silicon on the substrate S by a plasma CVD method. In the present embodiment, parallel plate electrodes are used for generating plasma, but the present invention is not limited to this method.
The thin film forming apparatus 10 of the present embodiment includes a film forming container 20, a silicon substrate 24, an exhaust unit 40, a high frequency power source 50, a silane gas supply unit 60, a dilution gas supply unit 62, a control unit 70, Is provided.

The film forming container 20 includes a substrate support part 32, an upper electrode 36, and a lower electrode 38. A lower electrode 38 is provided on the upper surface of the substrate support portion 32. Here, the lower electrode 38 is grounded. The substrate S is supported by lift pins 44 penetrating the substrate support portion 32 from below the film forming container 20. The lift pins 44 can be moved up and down by a lift mechanism 46, and the lift mechanism 44 moves the lift pins 44 downward while the lift pins 44 support the substrate S, whereby the substrate S is placed on the lower electrode 38. Installed.
In addition, a heater 34 is provided inside the substrate support portion 32, and the temperature of the substrate S can be adjusted by the heater 34.

The upper electrode 36 is provided above the substrate S and is connected to the high frequency power supply 50. When the high frequency power supply 50 supplies a high frequency current having a predetermined frequency, plasma is generated between the upper electrode 36 and the lower electrode 38.
The high frequency power supply 50 is connected to the control unit 70. The timing at which the high frequency power supply 50 supplies the high frequency current to the upper electrode 36 is controlled by the control unit 70.

  The film forming container 20 includes a silicon base material 24 above the substrate S. The silicon substrate 24 is supported by a support portion 26 provided in the film forming container 20. The silicon substrate 24 is, for example, single crystal silicon or polycrystalline silicon. Moreover, it is preferable that the thickness of the silicon base material 24 is 1 mm or more, for example.

  In the example shown in FIG. 1, the example in which the silicon base material 24 is provided between the substrate S and the upper electrode 36 has been described. However, for example, the silicon base material 24 may be provided on the side surface of the film formation container 20. Good.

  The exhaust unit 40 exhausts a film forming gas such as a silane gas or a dilution gas supplied into the film forming container 20 through the exhaust pipe 42. The exhaust unit 40 is, for example, a dry pump. The exhaust unit 40 evacuates the film forming container 20 so that the degree of vacuum in the film forming container 20 is maintained at about 0.1 Pa to 100 Pa even when the film forming gas is supplied into the film forming container 20. .

The silane gas supply unit 60 supplies silane gas (SiH ₄ ), which is a raw material of the microcrystalline silicon thin film formed on the substrate S, into the film forming container 20. The silane gas supply unit 60 is connected to the control unit 70, and the timing at which the silane gas supply unit 60 supplies the silane gas and the flow rate of the silane gas are controlled by the control unit 70.

  The dilution gas supply unit 62 supplies the dilution gas into the film forming container 20. The dilution gas is, for example, hydrogen gas. The dilution gas supply unit 62 is connected to the control unit 70, and the timing at which the dilution gas supply unit 62 supplies the dilution gas and the flow rate of the dilution gas are controlled by the control unit 70.

The control unit 70 controls the timing at which the high frequency power supply 50 supplies a high frequency current to the upper electrode 36, the timing at which the silane gas supply unit 60 supplies silane gas, and the timing at which the dilution gas supply unit 62 supplies dilution gas. The control unit 70 controls the flow rate of the silane gas supplied from the silane gas supply unit 60 and the flow rate of the dilution gas supplied from the dilution gas supply unit 62.
The above is the schematic configuration of the thin film forming apparatus 10 of the present embodiment.

(Thin film formation method)
Next, with reference to FIG. 2, the thin film formation method using the thin film formation apparatus 10 of this embodiment is demonstrated. FIG. 2 is a flowchart showing an example of the thin film forming method of the present embodiment.

  First, a first film forming process is performed (step S101). In the first film formation step, the dilution gas supply unit 62 supplies hydrogen gas as a dilution gas into the film formation container 20. For example, the flow rate of hydrogen gas is 200 sccm.

Next, plasma is generated between the upper electrode 36 and the lower electrode 38 by supplying a high-frequency current from the high-frequency power source 50 during the first film forming step (step S102). When the hydrogen gas plasma is generated inside the film forming container 20, the silicon substrate 24 is sputtered, and silicon is supplied to the internal space of the film forming container 20, thereby forming a silicon atmosphere.
Moreover, plasma continues to be generated between the upper electrode 36 and the lower electrode 38 not only in the first film forming process but also in the second film forming process described later.

In the present embodiment, the silane gas supply unit 60 does not supply the silane gas into the film formation container 20 in the first film formation step. However, in the first film formation step, microcrystalline silicon nuclei are formed on the substrate S heated by the heater 34. This is because the Si thin film deposited on the silicon substrate 24 and the inner wall of the film forming container 20 is sputtered by plasma, and the inner space of the film forming container 20 is in a silicon atmosphere.
In the present embodiment, since the silicon base material 24 is provided inside the film forming container 20, the microcrystals formed on the substrate S due to the distribution of the Si thin film deposited on the inner wall surface of the film forming container 20 and the like. It can suppress that the characteristic of a silicon thin film changes.

  Next, the second film forming process is performed in a state where the generation of plasma is maintained (step S103). In the second film forming step, the silane gas supply unit 60 supplies silane gas into the film forming container 20. For example, the flow rate of silane gas is 10 sccm. In the second film formation step, the dilution gas supply unit 62 supplies hydrogen gas into the film formation container 20. For example, the flow rate of hydrogen gas is 10 sccm.

  As described above, since a microcrystalline silicon nucleus is formed on the substrate S in step S102, a highly crystalline microcrystalline silicon film is formed on the silicon nucleus in step S103. .

  As described above, according to the thin film forming method of the present embodiment, since the silicon base material 24 is provided inside the film forming container 20, a highly crystalline microcrystalline silicon thin film can be stably formed on the substrate S. It can be formed into a film.

<Second Embodiment>
In the first embodiment, the example in which the silane gas supply unit 60 does not supply the silane gas into the film formation container 20 in the first film formation process has been described, but the present invention is not limited to this. This embodiment is different from the first embodiment in that the silane gas supply unit 60 also supplies silane gas into the film formation container 20 in the first film formation step. Since the configuration of the thin film forming apparatus 10 is the same as that of the first embodiment, the thin film forming method of this embodiment will be described below.

  First, a first film forming process is performed (step S101). In the first film formation step of the present embodiment, the silane gas supply unit 60 supplies silane gas into the film formation container 20. For example, the flow rate of silane gas is 5 sccm. The dilution gas supply unit 62 supplies hydrogen gas as a dilution gas into the film forming container 20. For example, the flow rate of hydrogen gas is 200 sccm.

  Next, plasma is generated between the upper electrode 36 and the lower electrode 38 by supplying a high-frequency current from the high-frequency power source 50 during the first film forming step (step S102). When the plasma of hydrogen gas is generated inside the film forming container 20, the silicon base material 24 is sputtered, and silicon is supplied to the internal space of the film forming container 20, thereby forming a silicon atmosphere.

Also in the present embodiment, microcrystalline silicon nuclei are formed on the substrate S heated by the heater 34 in the first film forming step. This is because the Si thin film deposited on the silicon substrate 24 and the inner wall of the film forming container 20 is sputtered by plasma, or by the silane gas supplied from the silane gas supply unit 60 in the first film forming step.
However, in order to efficiently form microcrystalline silicon nuclei on the heated substrate S in the first film formation step, it is preferable that the ratio of the flow rate of the silane gas to the total flow rate of the silane gas and the dilution gas is small. For example, in the first film forming step, the flow rate of the silane gas with respect to the total flow rate of the silane gas and the dilution gas is preferably 1% or more and 10% or less.

Next, the second film forming process is performed in a state where the generation of plasma is maintained (step S103). In the second film forming step, the silane gas supply unit 60 supplies silane gas into the film forming container 20. For example, the flow rate of silane gas is 10 sccm. In the second film formation step, the dilution gas supply unit 62 supplies hydrogen gas into the film formation container 20. For example, the flow rate of hydrogen gas is 10 sccm.
In order to form a microcrystalline silicon film with high crystallinity in the second film formation step, it is preferable that the ratio of the flow rate of the silane gas to the total flow rate of the silane gas and the dilution gas is larger than that in the first film formation step. . For example, in the second film formation step, the flow rate of the silane gas with respect to the total flow rate of the silane gas and the dilution gas is preferably 10% or more and 50% or less.

  As described above, also in the thin film forming method of the present embodiment, since the silicon base material 24 is provided inside the film forming container 20, a highly crystalline microcrystalline silicon thin film can be stably formed on the substrate S. Can be membrane.

  Although the thin film forming apparatus and the thin film forming method of the present invention have been described in detail above, the present invention is not limited to the above embodiment. It goes without saying that various improvements and modifications may be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 10 Thin film formation apparatus 20 Film-forming container 24 Silicon base material 26 Support part 32 Substrate support part 34 Heater 36 Upper electrode 38 Lower electrode 40 Exhaust part 42 Exhaust pipe 44 Lift pin 46 Lifting mechanism 50 High frequency power supply 60 Silane gas supply part 62 Dilution gas Supply unit 70 Control unit S Substrate

Claims (9)

A thin film forming apparatus for forming a thin film on a substrate,
A deposition container;
A silane gas supply unit for supplying silane gas, which is a raw material of the thin film, to the film formation container;
A dilution gas supply unit for supplying a dilution gas for diluting the silane gas to the film formation container;
A plasma generating section for generating plasma inside the film formation container;
A silicon substrate disposed inside the film formation container;
A control unit for controlling the timing at which the silane gas supply unit supplies the silane gas, and the timing at which the dilution gas supply unit supplies the dilution gas;
A thin film forming apparatus comprising:   The thin film forming apparatus according to claim 1, wherein the film forming container includes a support portion that supports the silicon substrate.   The thin film forming apparatus according to claim 1 or 2, wherein the silicon substrate has a thickness of 1 mm or more.   The control unit controls the silane gas supply unit and the dilution gas supply unit so as to supply the silane gas and the dilution gas to the film formation container after supplying only the dilution gas to the film formation container. The thin film forming apparatus according to claim 1.   The thin film forming apparatus according to claim 1, wherein the dilution gas is hydrogen gas. A thin film forming method for forming a thin film on a substrate,
A first film forming step of supplying a dilution gas to a film forming container in which a silicon substrate is disposed;
A second film forming step of supplying the silane gas and the dilution gas to the film forming container;
A plasma generating step of generating plasma of the dilution gas inside the film formation container;
A thin film forming method characterized by comprising:   The thin film forming method according to claim 6, wherein the silicon substrate has a thickness of 1 mm or more.   The thin film forming method according to claim 6 or 7, wherein the dilution gas is hydrogen gas. In the first film formation step, the silane gas is further supplied to the film formation container,
The flow rate of the silane gas supplied to the film formation container in the first film formation step is smaller than the flow rate of the silane gas supplied to the film formation container in the second film formation step. Thin film forming method.

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