JP2019112725A - Plasma CVD device - Google Patents

Abstract

To provide a plasma CVD device that can solve the problem in which it is difficult to effectively terminate a dangling bond on the surface of a film and in the film for higher quality of the film, because a hydrogen radical cannot be effectively transported without loss from a generation region to a film growth region in conventional plasma CVD devices using a mixed gas of silane and hydrogen.SOLUTION: A plasma CVD device deposits a film by alternately repeating a first step and a second step. In the first step with intermittent feeding means of a raw material gas, a thin film is deposited on the surface of a substrate by forming plasma of a mixed gas of a raw material gas and hydrogen. In the second step, a dangling bond on the surface of the film and in the film is terminated by forming plasma of hydrogen gas in a time zone different from a time zone of the first step.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a plasma CVD apparatus. In particular, the present invention relates to a plasma CVD apparatus for forming a high quality thin film.

  A plasma CVD apparatus for forming a silicon-based thin film is utilized to form a photoelectric conversion film, an insulating film, a passivation film, a barrier film or the like in a solar cell, a liquid crystal display TFT, an organic EL and various semiconductor devices. Plasma CVD apparatuses are also applied to the production of diamond like carbon (DLC) and carbon-based thin films.

In forming a silicon-based thin film using a plasma CVD apparatus, generally, a method of generating a plasma by adding an appropriate amount of hydrogen gas to a silane-based source gas is used. It is known that formation of high quality films requires termination of bond bonds by hydrogen radicals, which is effective. That is, it is known that it is necessary to repair the film surface during film formation and dangling bonds (unbonds) in the film with hydrogen radicals, which is known to be effective.
However, in the above method, the electron temperature of the plasma of the mixed gas containing SiH ₄ gas and H ₂ gas depends on the dilution rate of H ₂ gas, and if the amount of added hydrogen gas is increased too much, the plasma characteristics become silane type Since the plasma temperature changes to hydrogen, the electron temperature of the plasma increases, and the amount of SiH ₂ radicals generated due to the rough film increases, which causes a problem that a high-quality film can not be formed. Therefore, it is difficult to cope with further improvement of the film quality.

In recent years, research and development aiming at further improvement of the photoelectric conversion efficiency of crystalline silicon solar cells have been actively conducted. In particular, heterojunction back contact solar cells using single crystal silicon have three performance factors that determine the power generation efficiency: cell open circuit voltage Voc (V) and short circuit current density Jsc (mA / cm ^2). ) And the improvement of the fill factor (%), attention is paid to having excellent characteristics. The structure of the heterojunction back contact solar cell is shown, for example, in Patent Document 1.
Patent Document 1 describes the following structure. That is, a crystalline semiconductor including an impurity exhibiting one conductivity type, an intrinsic first amorphous semiconductor film formed on the entire surface including the first region of the one surface of the crystalline semiconductor, and A second amorphous semiconductor film formed by diffusing an impurity having the other conductivity type into the first amorphous semiconductor film on the first region, and the second surface of the crystalline semiconductor An amorphous semiconductor layer containing an impurity showing the one conductivity type, formed on the entire surface of the first amorphous semiconductor film, including the second region; and on the first region A first electrode formed on the amorphous semiconductor layer, a second electrode formed on the amorphous semiconductor layer on the second region, and the other surface of the crystalline semiconductor And an intrinsic amorphous semiconductor film and an antireflective film formed thereon. Force element.

A heterojunction back contact solar cell is characterized in that it has a configuration in which an amorphous semiconductor film of about 1.8 eV is joined to a single crystal Si substrate having an energy band gap of about 1.1 eV, and its amorphous state. Intrinsic semiconductor films (hereinafter referred to as i-type a-Si films), p-type amorphous semiconductor films (hereinafter referred to as p-type a-Si films) and n-type An amorphous semiconductor film (hereinafter referred to as an n-type a-Si film) is used.
In the production of the above solar cell, a high quality amorphous semiconductor film, that is, a film having a low defect density in the film is required (a defect in the film is also called a dangling bond of silicon atoms or a dangling bond). ). In particular, in the application to a solar cell, the film surface and the defects in the film lose the carriers (electrons and holes) generated by the photoelectric effect to reduce the power generation efficiency, so a film with a low defect density is required.
However, in the conventional plasma CVD apparatus, it is difficult to effectively terminate dangling bonds in the film surface and in the film, and there is a problem that it can not cope with the further quality improvement of the film. Further, the defect density of a film formed using a conventional plasma CVD apparatus is 10 ¹⁵ to 10 ¹⁶ pieces / cm ^3, which is several orders of magnitude higher than that of a single crystal Si substrate.

Eliminating the generation of S _i H ₂ radicals is poor film forming factors, the method of forming a high quality silicon-based thin film and a device using the same is described in US Pat. The features are as follows.
First, there are the following features. A plasma deposition method for producing a thin film of a source gas on a substrate by plasma enhanced chemical vapor deposition, wherein hydrogen gas is introduced into a vacuum and a high frequency electric field is applied, and the hydrogen gas is excited into a plasma state. While generating radicals, the source gas is supplied from a system different from the hydrogen gas, and the source gas and the hydrogen radicals are reacted in a space without plasma to form a film on the substrate. Plasma film forming method.
Second, there are the following features. A plasma deposition method for forming a thin film of a source gas on a substrate by plasma enhanced chemical vapor deposition, comprising introducing hydrogen gas into a vacuum and applying a high frequency electric field to generate plasma of the hydrogen gas. And a second plasma generation region for generating a plasma of the mixed gas by introducing a mixed gas of hydrogen gas and a source gas into a vacuum and applying a high frequency electric field to the vacuum, and forming the first plasma. A plasma film forming method comprising: ON / OFF controlling an area and intermittently supplying hydrogen radicals generated in the first plasma control area to the second plasma generation area to form a film.

Patent 4155899 Japanese Patent Application Laid-Open No. 2006-100551

As described above, in the conventional plasma CVD apparatus, it is difficult to effectively terminate dangling bonds in the film surface and in the film, and there is a problem that it is not possible to cope with further film quality improvement.
For example, a plasma CVD method and apparatus using the same having a first feature described in Patent Document 2, hydrogen radicals generated by the hydrogen plasma, the raw material gas silane (S i _{H 4)} were mixed, the following equation The reaction generates _Si H ₃ radicals, which are precursors of film formation, to form a film.
S _i H ₄ + H → S _i H ₃ + H ₂
This method has the advantage that there is no generation of S _i H ₂ radicals of poor film formation factors, the formation of high-quality film when it is difficult, is feared. That is, to form a high-quality film, it is necessary to effectively transport hydrogen radicals having the function of terminating dangling bonds in the film surface and in the film to the film surface, but the plasma having the first feature described above In the CVD method and its apparatus, most of hydrogen radicals are consumed in the above reaction with _Si H ₄ in the gas phase, so the amount of hydrogen radicals reaching the film surface is small, and formation of a high quality film is difficult It is feared that.
For example, a plasma CVD method and apparatus having the second feature described in Patent Document 2 introduce a hydrogen gas into a vacuum and apply a high frequency electric field to generate a plasma of the hydrogen gas. A region and a second plasma generation region for introducing a mixed gas of hydrogen gas and a source gas into vacuum to apply a high frequency electric field to generate plasma of the mixed gas; providing the first plasma generation region The film formation is performed by intermittently supplying hydrogen radicals generated in the first plasma control region to the second plasma generation region, thereby forming the film in the ON control state. and most of the hydrogen radicals is reacted with S _i H ₄ in the gas phase loss, small amount of hydrogen radicals to reach the growing film on the substrate surface, is that difficulties are formed of a high-quality film, fear It is.
As described above, in the conventional plasma CVD apparatus, most of the hydrogen radicals disappear due to the strong reaction between hydrogen radicals and silane molecules, so the hydrogen radicals are effectively transported from the formation region to the film growth region without loss. There is no means. Therefore, it is difficult to terminate dangling bonds in the film surface and the film, and there is a problem that it can not cope with the further quality improvement of the film.
Due to the above-mentioned problems, it is difficult to meet the need to form a film of higher quality compared to the film formed by the current technology. Therefore, the creation of a new plasma CVD apparatus capable of effectively transporting hydrogen radicals to a film growth surface is desired.
An object of the present invention is to provide a plasma CVD apparatus capable of solving the above problems.

According to a first aspect of the present invention for solving the above-mentioned problems, a substrate holding means and an electrode are disposed opposite to each other in a reaction vessel provided with an exhaust means, and Si (silicon) containing gas is disposed in the reaction vessel A source gas comprising at least one selected from an N (nitrogen) -containing gas, a C (carbon) -containing gas, a B (boron) -containing gas and a P (phosphorus) -containing gas, and a hydrogen gas which is a dilution gas; A plasma CVD apparatus for plasmatizing the source gas and the hydrogen gas by supplying a high frequency power to the electrode and forming a thin film on a surface of the substrate placed on the substrate holding means;
The hydrogen gas supply source and the source gas supply source are separated and disposed, and gas injection holes are provided in the electrode;
Piping-connecting the source gas source, an intermittent gas supply means for intermittently supplying the source gas to the gas injection holes, and the gas injection holes in this order;
Piping-connecting the hydrogen gas supply source, the hydrogen gas supply means for continuously supplying the hydrogen gas to the gas injection holes, and the gas injection holes in this order;
A first process of forming a thin film on the surface of a substrate mounted on the substrate holding means by plasmatizing a mixed gas of a source gas supplied from the intermittent gas supply means and a hydrogen gas supplied from the hydrogen gas supply means And a second step of performing hydrogen radical treatment of the thin film with hydrogen radicals generated by plasmatizing the hydrogen gas in a time zone different from the time zone of the first step, alternately in time It is characterized in that it is configured to form a film.

  According to the first aspect of the present invention, when forming the thin film on the substrate by plasmatizing the source gas and the hydrogen gas, the thin film is formed by radicals generated by plasmatizing the mixed gas of the source gas and the hydrogen gas. A second step of performing hydrogen radical treatment on the surface of the thin film and in the film using hydrogen radicals generated by plasmatizing the hydrogen gas in a time zone different from the time zone of the first step and the second process It is possible to form a thin film while alternately repeating the steps of and in time. According to the present invention, since the hydrogen radicals reliably and effectively reach the substrate surface, termination of dangling bonds in the film surface and the film by the hydrogen radicals is reliably and effectively performed. It becomes possible to form a high quality thin film with a low defect density.

  According to a second aspect of the present invention, in the first aspect, the intermittent gas supply means includes a mass flow controller and a vacuum solenoid valve.

  According to the second aspect of the present invention of the present invention, the first aspect can be implemented easily and simply.

A third aspect of the present invention, in the second invention, the solenoid valve for the vacuum, the raw material gas and the time zone T _1, wherein the raw material gas is supplied to the gas ejection hole is not supplied to the gas ejection hole Deyutei (Duty) ratio of the cycle, including the time zone T _2, i.e., the time period the material gas is supplied T _{1 /} (time period in which the time period T _{1 +} the raw gas material gas is supplied is not supplied It is characterized by including a control device capable of arbitrarily setting T ₂ ) in the range of 30% to 90%.

  According to the third aspect of the present invention, the second aspect can be implemented effectively and simply.

  According to a fourth invention of the present invention, in the invention according to any one of the first invention to the third invention, the electrode is formed of a hollow metal tube.

  According to the fourth invention of the present invention, the first to third inventions can be implemented easily and simply.

  According to a fifth invention of the present invention, in the invention according to any one of the first invention to the third invention, the electrode is flat.

  According to the fifth invention of the present invention, the first to third inventions can be implemented easily and simply.

  According to a sixth invention of the present invention, in the invention according to any one of the first invention to the fifth invention, the substrate holding means sets the temperature of the substrate to 150 ° C. to 300 ° C. .

  According to the sixth invention of the present invention, in the first to fifth inventions, since the temperature of the substrate is set to 150 ° C. to 300 ° C., the rate of adsorption of hydrogen radicals to the substrate becomes high. And hydrogen radicals can be effectively processed on the deposited film.

The present invention has the effect of being able to solve the problems of the prior art. In the prior art, it is difficult to effectively terminate dangling bonds in the film surface and in the film because hydrogen radicals generated by plasma can not be effectively transported to the surface of the growth film, but the present invention Then it will be possible. As a result, it is possible to meet the need for forming a high quality film (low defect density) using hydrogen radicals.
Further, the defect density of the film formed by the conventional technique is 10 ¹⁵ to 10 ¹⁶ pieces / cm ³ , but according to the present invention, 10 ¹⁴ to 10 ¹⁵ pieces / one digit or two digits smaller than the conventional value. There is a possibility that the film quality can be improved to the cm ³ grade.
Further, the contribution of the plasma CVD apparatus according to the present invention to the performance improvement of various electronic device products is extremely significant.

FIG. 1 is a schematic perspective view for explaining a plasma CVD apparatus according to a first embodiment of the present invention. FIG. 2 is a schematic perspective view for explaining an electrode provided with gas injection holes which is a component of the plasma CVD apparatus according to the first embodiment of the present invention and a power supply means. FIG. 3 is a schematic cross-sectional view for explaining the plasma CVD apparatus according to the first embodiment of the present invention. FIG. 4 is a schematic gas showing temporal changes in the supply amounts of the source gas and the hydrogen gas for explaining the operation of the intermittent gas supply means which is a component of the plasma CVD apparatus according to the first embodiment of the present invention. FIG. FIG. 5 is a cross-sectional view of a typical deposited film for explaining the process of film growth when forming a silicon-based thin film using the plasma CVD apparatus according to the first embodiment of the present invention. FIG. 6 is a schematic cross-sectional view for explaining a plasma CVD apparatus according to a second embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each of the drawings, the same members are denoted by the same reference numerals, and overlapping descriptions will be omitted.
In addition, this invention is not limited to the following description, In the range which does not deviate from the summary of this invention, it can change suitably. In the drawings shown below, the scale of each member may differ from the actual one for convenience of explanation. In addition, the scale may be different from the actual one among the drawings.

First Embodiment
A plasma CVD apparatus according to the first embodiment of the present invention and a film forming method using the apparatus will be described. First, the configuration of the plasma CVD apparatus will be described with reference to FIGS. 1 to 5.
FIG. 1 is a schematic perspective view for explaining a plasma CVD apparatus according to a first embodiment of the present invention. FIG. 2 is a schematic perspective view for explaining an electrode provided with gas injection holes which is a component of the plasma CVD apparatus according to the first embodiment of the present invention and a power supply means.
FIG. 3 is a schematic cross-sectional view for explaining the plasma CVD apparatus according to the first embodiment of the present invention. FIG. 4 is a schematic gas showing temporal changes in the supply amounts of the source gas and the hydrogen gas for explaining the operation of the intermittent gas supply means which is a component of the plasma CVD apparatus according to the first embodiment of the present invention. FIG. FIG. 5 is a cross-sectional view of a typical deposited film for explaining the process of film growth when forming a silicon-based thin film using the plasma CVD apparatus according to the first embodiment of the present invention.

The code | symbol 1 is a reaction container. The reaction vessel 1 has air tightness and is evacuated by a vacuum pump (not shown) via an exhaust hole 2 and an exhaust pipe 5 described later to achieve a degree of vacuum of 2.66 × 10 ⁻⁴ Pa (2 × 10 ⁻⁶ Torr). It becomes degree. Further, the inner wall of the reaction vessel 1 has no adhesion of impurities, and satisfies the specification applicable to plasma CVD.
The code | symbol 2 is an exhaust port. The exhaust hole 2 is disposed on the back side of the electrode 30, which will be described later, as viewed from the substrate holding means 3a, which will be described later, and cooperates with the exhaust pipe 5, which is described later, a vacuum pump (not shown) and a pressure gauge (not shown) Evacuate so as to keep the pressure at a predetermined value.
Reference numeral 5 is an exhaust pipe. The exhaust pipe 5 cooperates with the exhaust hole 2, the vacuum pump (not shown) and the pressure gauge (not shown) to exhaust the pressure in the reaction vessel 1 so as to maintain the pressure at a predetermined value.
Here, if the total flow rate of the source gas and hydrogen gas described later is about 50 sccm to 2000 sccm, the pressure can be set to an arbitrary pressure in the range of about 10 Pa to 500 Pa (75 mTorr to 3.75 Torr) and maintained at a constant pressure It is.

Reference numeral 23a is a source gas supply source. Raw material gas supply source 23a is silane _{(S i H} 4), disilane _(S i2 _H 6), trisilane _(S i3 _H 8), monomethyl silane _{(CH 3 S i H 3)} , hydrogen _(H 2), nitrogen ( N ₂ ), ammonia (NH ₃ ), phosphine (PH ₃ ), diborane (B ₂ H ₆ ), germane (GeH ₄ ), methane (CH ₃ ) and ethane (C ₂ H ₆ ), etc. It has the corresponding source gas. In addition, when selecting several source gas, the several source gas according to it is prepared. Also, a plurality of raw material gas mass flow controllers 24a are prepared accordingly.
Here, for example, silane _(S i _{H 4)} providing a gas. Raw material gas supply source 23a is a raw material gas of silane (S i _{H 4)} gas, which will be described later via the raw material gas mass flow controller 24a, the first source gas supply pipe 25a and a vacuum device for solenoid valve 10 will be described later second To the source gas supply pipe 25b of
Reference numeral 24a is a mass flow controller for the source gas. Raw material gas mass flow controller 24a, the silane is supplied from the source gas supply source 23a (S i _{H 4)} set to an arbitrary flow rates preselected flow rate of the gas, the electromagnetic valve 10 and the second raw material for vacuum device It supplies to the below-mentioned gas mixing pipe 26 via the gas supply pipe 25b. Here, silane _(S i _{H 4)} in a range of flow rates 5sccm~200sccm gas can be set to any flow rate.

Reference numerals 25a and 25b denote first and second source gas supply pipes. The first and second source gas supply pipes 25a and 25b are connected by a vacuum device solenoid valve 10 described later. The first and second source gas supply pipes 25a and 25b are connected in the order of the first source gas supply pipe 25a, the vacuum device solenoid valve 10, and the second source gas supply pipe 25b, and a mass flow controller for the source gas The source gas supplied from 24 a is supplied to the gas mixing pipe 26 described later. The raw material gas supplied from the raw material gas supply pipe 25b to the gas mixing pipe 26 is intermittently operated by the below-mentioned vacuum device solenoid valve 10 disposed between the first and second raw material gas supply pipes 25a and 25b. Supplied.
When the source gas is intermittently shut off by the vacuum device solenoid valve 10 described later, the second source gas is supplied so that the cutoff of the source gas is good (the source gas does not flow with cod). The volume of the tube 25b should be minimized.

Reference numeral 25c is a hydrogen gas supply pipe. The hydrogen gas supply pipe 25c supplies the hydrogen gas supplied from the mass flow controller 24c for hydrogen gas described later to the gas mixing pipe 26 described later.
Reference numeral 24c is a hydrogen gas mass flow controller. The hydrogen gas mass flow controller 24c sets the flow rate of hydrogen gas supplied from the hydrogen gas supply source 23c described later to an arbitrary flow rate selected in advance, and supplies the hydrogen gas to the hydrogen gas supply pipe 25c. Here, the hydrogen gas mass flow controller 24 c can set an arbitrary flow rate in the range of 10 sccm to 1000 sccm.
Reference numeral 23c is a hydrogen gas supply source. The hydrogen gas supply source 23c supplies hydrogen gas to the hydrogen gas supply pipe 25c via the hydrogen gas mass flow controller 24c. The flow rate of hydrogen gas is constant and supplied continuously.
Reference numeral 26 is a gas mixing pipe. Gas mixing tube 26, the hydrogen gas supplied from the second raw material gas supplied from the source gas supply pipe 25b silane (S i _{H 4)} gas and a hydrogen gas supply pipe 25c is mixed, vacuum apparatus described later The gas is supplied to a gas injection hole 36 disposed in an electrode 30 described later via a joint 27 of the source gas supply pipe. During the time period in which the source gas is shut off by the vacuum device solenoid valve 10, the gas mixing tube 26 is provided with hydrogen gas at the electrode 30, which will be described later, via the joint 27 of the source gas supply tube for vacuum device described later. The gas is supplied to the vented gas injection hole 36.
Reference numeral 27 denotes a joint of a raw material gas supply pipe for a vacuum device. The joint 27 of the raw material gas supply pipe for the vacuum device is a gas injection hole 36 disposed in the electrode 30 so that the mixed gas of the raw material gas and the hydrogen gas supplied from the gas mixing pipe 26 or the hydrogen gas does not leak. Supply to
Reference numeral 29 is a gas junction. The gas merging portion 29 is a joint portion between the second source gas supply pipe and the hydrogen gas supply pipe 25c.

The code | symbol 10 is a solenoid valve for vacuum devices. The vacuum apparatus solenoid valve 10 is disposed between the raw material gas mass flow controller 24 a and the gas mixing pipe 26. The vacuum apparatus solenoid valve 10 supplies the gas mixing pipe 26 via the second source gas supply pipe 25 b while intermittently blocking the source gas supplied from the mass flow controller 24 a for the source gas.
Between the source gas supply source 23a and the gas injection holes 36, a source gas mass flow controller 24a, a first source gas supply pipe 25a, a vacuum device solenoid valve 10, a second source gas supply pipe 25b, and a gas. The mixing pipe 26, the joint 27 of the raw material gas supply pipe for vacuum device, the electrode 30, and the gas injection hole 36 are connected by piping in this order. In addition, the order of the raw material gas mass flow controller 24a and the vacuum device electromagnetic valve 10 is changed, and the raw material gas supply source 23a, the first raw material gas supply pipe 25a, the vacuum device electromagnetic valve 10, the raw material gas mass flow controller 24a, The second raw material gas supply pipe 25b, the gas mixing pipe 26, the joint 27 of the raw material gas supply pipe for a vacuum device, the electrode 30, and the gas injection holes 36 may be connected in this order.
Further, the means for intermittently flowing the source gas is not limited to the vacuum device solenoid valve 10, and other means capable of intermittently supplying the source gas may be used.
Here, means for intermittently supplying the raw material gas from the raw material gas supply source 23a to the gas injection holes 36, which is provided with the raw material gas mass flow controller 24a and the vacuum device electromagnetic valve 10, is an intermittent gas supply means. Called 22.

A time zone in which the vacuum device solenoid valve 10 shuts off the source gas intermittently is controlled by a vacuum device solenoid valve control device 11 described later. The vacuum device electromagnetic valve 10 which is a component of the intermittent gas supply means 22 is controlled to be ON / OFF by a program set in advance in the control device 11 of the vacuum device electromagnetic valve.
For example, as shown in FIG. 4 (a), silane source gas at a flow rate _{Q 1,} and so that the time _{0~t 1, t 2 ~t 3,} t 4 ~t 5, supplied with the time zone _{T 1} It is, and so that the time _{t 1 ~t 2, t 3 ~t} 4, is cut off in a time period _{T 2.} Hydrogen gas, as shown in FIG. 4 (b), is supplied at a flow rate Q ₂ constant. That is, only the raw material gas and hydrogen gas mixed gas is shut off time period T ₁ and the raw material gas supplied to the gas ejection hole 36 of the hydrogen gas comprises a time zone T ₂ which is supplied to the gas ejection hole 36, alternately The source gas is supplied intermittently intermittently.
Here, the value of the time zone T ₂ time zone T ₁ and the raw material gas feed gas is supplied is interrupted, the residence time of the hydrogen gas τ calculated by equation shown below, that is, hydrogen gas reaction It is set longer than the time τ for staying in the container.
τ = pressure of reaction vessel (Pa) × volume of reaction vessel (m ³ ) / amount of gas supplied (Pa · m ³ · s ⁻¹ )
For example, when the volume of the reaction vessel = 0.2 mx 0.2 mx 0.2 m, the hydrogen gas flow rate = 200 sccm, and the pressure = 40 Pa, the residence time τ of hydrogen gas is as follows. That is, ^{τ = 40Pax0.008m 3 /(200sccmx1.69x10 -3 Pa ·} m 3 / s · sccm) = 0.946s.
For example, when the volume of the reaction vessel = 0.2 mx 0.2 mx 0.2 m, the flow rate of silane gas of the source gas = 40 sccm, the flow rate of hydrogen gas = 200 sccm, and the pressure = 40 Pa, the residence time τ of the mixed gas of the source gas and hydrogen gas is It is calculated as That is, τ = 40 Pax 0.008 m ³ / (240 sccm × 1.69 Pa · m ³ /s·sccm)=0.79 s.

Reference numeral 11 is a control device of a vacuum device solenoid valve. The control device 11 of the vacuum device solenoid valve program-controls the open / close time zone of the vacuum device solenoid valve 10. The control device 11 of the electromagnetic valve for vacuum device, the a time period T ₁ for supplying a raw material gas feed gas in the cycle, including the time zone T ₂ is not supplied Deyutei (Duty) ratio, i.e., the raw material gas time zone supplied T _{1 /} a (the time period T to supply the raw material gas _{1 +} the source gas hours T ₂ is not _supplied) can be set arbitrarily in the range of 30% to 90%.
If the duty ratio is about 30% or less, the film forming speed is too slow, and if it is about 90% or more, the amount of hydrogen radicals supplied to the film surface is excessively suppressed. Therefore, it is good to choose in the range of 30%-90%.

The code | symbol 3a is a board | substrate holding means on which the board | substrate 3 is mounted. The substrate holding means 3 a is disposed at the main part inside the reaction vessel 1. The substrate holding means 3a incorporates a cooling means and a heating means so as to adjust the temperature of the substrate 3, and is provided with a substrate temperature control device. The substrate temperature control device can set and maintain the temperature of the substrate 3 at an arbitrary value in the range of 30 ° C. to 300 ° C.
The code | symbol 3 is a board | substrate with which the target thin film is formed. Here, as the substrate 3, for example, glass of size: 15 cm square x thickness 0.63 mm is used.
The substrate 3 is placed on the substrate holding means 3a from a loading chamber (not shown) by a substrate loading device (not shown), and moved to an unloading chamber (not shown) after film formation is completed. Then, it is carried out of an unloading chamber (not shown).

Reference numeral 36 is a gas injection hole. Gas jetting holes 36 is disposed on the electrode 30 will be described later, the silane of the raw material gas supplied from the raw material gas supply source 23a (S i _{H 4)} for jetting the hydrogen gas supplied from the gas and a hydrogen gas supply source 23c . The gas injection holes 36 have a diameter of about 0.2 mm to 1.0 mm, and are arranged at intervals of about 2 mm to 10 mm. Here, the diameter of the holes is 0.6 mm, and the distance between the holes is 5 mm.
Reference numeral 37 indicates the flow of exhaust gas. The exhaust flow 37 conforms to the volume V of the reaction vessel 1, the pressure P, the arrangement of the exhaust holes 2 and the gas injection holes 36, etc., but under the conditions of film formation by plasma CVD, an intermediate flow intermediate between molecular flow and viscous flow. With characteristics. In the film formation using a plasma CVD apparatus, the value of PD (Pa · m) which is the product of the pressure P and the representative length D of the reaction vessel 1 is in the range of 0.02 to 0.68 Pa · m. It is known.

Reference numeral 30 is an electrode. The electrode 30 is comprised of a hollow metal tube. Here, the shape of the electrode 30 is a ladder-like shape that can easily generate plasma. The electrode 30 includes a gas injection hole 36 and is connected to a high frequency power source 60 described later. Here, a ladder type is adopted as the electrode 30, but any electrode may be used as long as the arrangement of the gas injection holes 36 is easy and plasma generation is easy. The cross-sectional shape of the electrode 30 is easy to manufacture in a rectangular shape or a circular shape.
The high frequency power supplied from the high frequency power supply 60 described later is supplied to the electrode 30 from the high frequency power supply point 65 through the impedance matching unit 61, the high frequency current introduction terminal 62, and the vacuum cable 63.
When high frequency power is supplied to the electrode 30, a high frequency electric field is generated around the electrode 30, the silane of the raw material gas ejected from the gas ejection holes 36 (S i _{H 4)} gas mixture of gas and hydrogen gas or hydrogen gas, Is plasmatized.

Silane (S i _{H 4)} a plasma of a mixed gas of gas and hydrogen gas is schematically indicated by reference numeral 31 in FIG. 3. In the plasma 31 of the mixed gas, various radicals which are precursors of film formation exist. Radicals such as SiH ₃ , SiH ₂ , SiH and H diffuse and move from the plasma 31 to the substrate 3 by the diffusion phenomenon as shown by reference numeral 33 in FIG. 3 to form, for example, an a-Si film.
The hydrogen gas plasma is schematically shown by reference numeral 32 in FIG. Hydrogen radicals are present in the hydrogen gas plasma 32. The hydrogen radicals diffuse and move from the plasma 32 toward the substrate 3 by the diffusion phenomenon, as indicated by reference numeral 35 in FIG. 3, and dangling the film deposited on the substrate, for example, the surface of the a-Si film and the film. Terminate the bond.
The hydrogen radicals 35 in the plasma are adsorbed at a high adsorption rate to the deposited film on the substrate surface if the temperature of the substrate is 150 ° C. to 300 ° C. In addition, since there is no silane gas that causes hydrogen radicals 35 to disappear between the plasma 32 and the deposited film on the surface of the substrate 3, the hydrogen radicals 35 efficiently reach the substrate.

Reference numeral 60 is a high frequency power source. The high frequency power source 60 is selected in the frequency band where the low pressure gas can be easily plasmatized, that is, in the range of 10 MHz to 300 MHz. Here, the 13.56 MHz power supply is selected because the price of the device is low.
The code | symbol 61 is an impedance matching device. The impedance matcher 61 matches the output impedance of the high frequency power source 60 with the impedance of the generated plasma. Note that when the impedance is adjusted, the reflected wave from the plasma side of the high frequency power supplied from the high frequency power source 60 to the electrode 30 is reduced. In addition, since high frequency power has the properties of a traveling wave and a reflected wave as an electromagnetic wave, the traveling wave output from the high frequency power supply 60 is maximized and the reflected wave returned is minimized by using the impedance matching unit 61. It is necessary to.
Reference numeral 62 is a high frequency current introduction terminal. The high frequency current introduction terminal 62 is a vacuum apparatus current introduction terminal with a small transmission loss of high frequency power.
The code | symbol 63 is an electric power transmission conductor for high frequencies. For the high frequency power transmission conductor 63, a coaxial cable or a lead is used.
The code | symbol 65 is a high frequency electric power supply point. The high frequency power supply point 65 is a connection point of the electrode 30 and the high frequency power transmission conductor 63, and the output of the high frequency power source 60 is through the impedance matching unit 61, the high frequency current introduction terminal 62 and the vacuum power transmission conductor 63. Supplied.
In addition, although the high frequency electric power supply point 65 is only one place here, when producing | generating the plasma of a large area, it can provide in multiple places and can achieve equalization | homogenization of plasma.

Next, with reference to FIGS. 1 to 5, the film forming method using the plasma CVD apparatus according to a first embodiment of the present invention, a passivation film heterojunction solar cell i-type a-S _i Taking a membrane as an example, it will be described.
Here, take the i-type a-S _i film is a passivation film heterojunction solar cell as an example will be explained the film forming method, a plasma CVD apparatus i-type according to a first embodiment of the present invention Naturally, it is not limited to the formation of the a- _Si film.

When forming a p-type a-Si film of a solar cell, for example, a mixed gas of hydrogen (H ₂ ), diborane (B ₂ H ₆ ) and silane (S _i H ₄ ) may be selected as a source gas.
In the case of forming the n-type a-Si film of the solar cell, for example, hydrogen as a source gas _{(H 2)} and phosphine (PH ₃₎ and silane _(S i _{H 4)} better to choose the mixed gas of the gas .
When forming an amorphous silicon carbide (a-SiC) film, for example, hydrogen (H ₂ ), methane (CH ₄ ), ethane (C ₂ H ₆ ) or ethylene (C ₂ ) is used as a source gas. and H _6), is better to choose a mixed gas of silane _(S i _{H 4).}
When forming an amorphous silicon germanium (a-SiGe) film, for example, it is preferable to select a mixed gas of hydrogen (H ₂ ), germane (GeH ₄ ) and silane (S _i H ₄ ) as a source gas. good.
In the case of forming a _S i CN film as the sealing film of the organic EL device, as a source gas, e.g., hydrogen _{(H 2)} and ammonia (NH ₃₎ and monomethyl silane _{(CH 3} S i _{H 3)} It is good to choose mixed gas.
When forming a diamond like carbon (DLC) film, it is preferable to select, for example, hydrogen (H ₂ ) and methane (CH ₃ ) as source gases.

Here, the substrate 3 is, for example, a glass of size: 150 mm × 150 mm × thickness 0.63 mm.
The substrate transfer door between the load chamber and the reaction vessel 1 is opened in a load chamber (not shown) and the substrate 3 is placed on the substrate holding means 3a by a substrate transfer device (not shown). Then, the substrate transfer door (not shown) is closed.

Next, a vacuum pump (not shown) is operated to evacuate the reaction vessel from the exhaust hole 2, and once the pressure inside the reaction vessel 1 reaches a vacuum level of, for example, 2.67.times.10.sup.- ⁴ Pa (2.times.10.sup.- ^6). Lower to about Torr).
Then, the flow rate of silane _(S i _{H 4)} silane by a mass flow controller 24a of the gas _(S i _{H 4)} gas, about 10Sccm～300sccm, for example, set to 40 sccm.
Next, the flow rate of hydrogen gas is set to about 100 sccm to about 1000 sccm, for example, 200 sccm, by the hydrogen gas mass flow controller 24c.
Next, the conditions of the intermittent gas supply of the raw material gas using the vacuum device solenoid valve 10 are set in the program of the control device 11 of the vacuum device solenoid valve. That is, the Deyutei (Duty) ratio of the cycle, including the time zone T ₁ and the raw material gas hours T ₂ is not supplied to supply the raw material gas is in the range of 30% to 90%, the time zone T to supply the raw material gas Set ₁

Here, the value of the time zone T ₂ time zone T ₁ and the raw material gas feed gas is supplied is interrupted, the residence time of the hydrogen gas τ calculated by equation shown below, that is, hydrogen gas reaction It is set longer than the time τ for staying in the container.
τ = pressure of reaction vessel (Pa) × volume of reaction vessel (m ³ ) / amount of gas supplied (Pa · m ³ · s ⁻¹ )
For example, when the volume of the reaction vessel = 0.2 mx 0.2 mx 0.2 m, the hydrogen gas flow rate = 200 sccm, and the pressure = 40 Pa, the residence time τ of hydrogen gas is as follows. That is, ^{τ = 40Pax0.008m 3 /(200sccmx1.69x10 -3 Pa ·} m 3 / s · sccm) = 0.946s.
For example, when the volume of the reaction vessel = 0.2 mx 0.2 mx 0.2 m, the flow rate of silane gas of the source gas = 40 sccm, the flow rate of hydrogen gas = 200 sccm, and the pressure = 40 Pa, the residence time τ of the mixed gas of the source gas and hydrogen gas is It is calculated as That is, τ = 40 Pax 0.008 m ³ / (240 sccm × 1.69 Pa · m ³ /s·sccm)=0.79 s.
Here, for example, the duty ratio is 50%, T ₁ = 3 seconds, and T ₂ = 3 seconds.
Incidentally, in advance, to grasp the data in which the film characteristics and Deyutei (Duty) ratio及T ₁ Vito T ₂ of interest as a parameter may be set based on the data.

Next, the valve (not shown) of the source gas supply source 23a is opened, and the valve (not shown) of the hydrogen gas supply source 23c is opened. The flow rate of hydrogen gas is constant and supplied continuously.
Next, the intermittent gas supply means 22 is operated.
Then, using a pressure gauge (not shown) and a vacuum pump (not shown), the internal pressure of the reaction vessel 1 is in the range of 1 Pa to 200 Pa (7.5 mTorr to 1.5 Torr), for example, 40 Pa (300 mTorr) as the film forming condition. Set to and maintain.
The adjustment operation of the raw material gas and the hydrogen gas may be automatically performed by a computer control method using a solenoid valve, a digital flow control device or the like (not shown). In addition, the intermittent gas supply means 10 may be automatically operated by a computer control method.
The temperature of the substrate 3 is set and maintained in the range of 150 ° C. to 300 ° C., for example 200 ° C. The temperature of the substrate 3 is set in consideration of the fact that the adsorption rate of hydrogen radicals to the substrate surface becomes approximately 100% at a temperature around 200 ° C. and that hydrogen is desorbed from the film surface when the temperature is high. .

Next, high frequency power is supplied from the high frequency power source 60 to the electrode tube 30 through the impedance matching unit 61, the high frequency current introduction terminal 62, and the high frequency power supply point 65. The high frequency power supplied to the electrode tube 30 is set as small as possible.
In order to form a high quality silicon film, it is preferable to lower the plasma electron temperature by reducing the power. For example, the power density of the supplied power may be set to 50 mW / cm ² or less at a value obtained by dividing the output of the high frequency power source 60 by the surface area of the electrode 30 in order to suppress generation of SiH ₂ radicals.

When high frequency power is supplied to the electrode tube 30, in the time period T ₁ in which the raw material gas is supplied, the plasma 31 of a mixed gas of raw material gas and hydrogen gas as shown in FIG. 3 is generated, mixed gas to the surface of the substrate 3 A film is deposited by radicals 33 generated by plasma. Then, in the time period T ₂ is not supplied raw material gas, the termination of the dangling bonds due to the film surface and the film during the reaction of hydrogen radicals 35 generated in the hydrogen plasma is performed.
As a result, as shown in FIG. 5, an i-type a-Si film composed of deposited films 50, 51, 52, 53 and interfaces 55, 56, 57, 58 that receive dangling bonds is formed. Ru. Since the silicon-based thin film formed here is a film in which dangling bonds are terminated by a hydrogen radical surface reaction in the film forming process, it becomes a high quality i-type a-Si film with a small defect density.
The defect density of the formed film is measured by a constant photocurrent method (CPM), an electron spin resonance method (ESR) or the like. _Si-H 2, Si-H bonds and Si-Si bonds analysis such, evaluation can be carried out infrared absorption spectrometry, secondary ion mass spectrometry, and by the run spectroscopy or the like.

Next, in the above-mentioned film formation, when a predetermined film formation time, for example, one minute has elapsed, the output of the high frequency power supply 60 is dropped to zero. Then, the valve (not shown) of the source gas supply source 23a and the valve (not shown) of the hydrogen gas supply source 23c are closed to stop the supply of the source gas and the hydrogen gas.
Here, the film forming time is an elapsed time from the time of generation of plasma by the electrode tube 30 here. In the case of implementing the film forming time with high accuracy, it is preferable to dispose a shutter mechanism that can be opened and closed in the vicinity of the substrate 3 and use it.
Thereafter, a substrate transfer door (not shown) between the reaction chamber 1 and the unload chamber (not shown) is opened, and the substrate 3 is moved from the substrate holding means 3a to the unload chamber (not shown) by the substrate transfer device (not shown). Then, the substrate transfer door (not shown) is closed.

Since the substrate 3 of the film to be formed has disappeared in the substrate holding means 3a of the reaction chamber 1, the substrate 3 is newly moved from the load chamber (not shown). As described above, the substrate transfer door between the load chamber and the reaction chamber 1 is opened with the substrate 3 prepared in advance in the load chamber (not shown), and the substrate 3 is loaded on the substrate holding means 3a by the substrate transfer device (not shown). Place. Then, the substrate transfer door (not shown) is closed.
Then, the above-described film formation is repeated a predetermined number of times, for example, on 100 substrates.
The substrate moved to the unloading chamber is taken out from the substrate taking out door (not shown) to the outside. Size taken out: A substantially uniform high quality i-type a-Si film is formed on a 150 mm × 150 mm × 0.63 mm thick substrate 3.
The film quality of the obtained i-type a-Si film is measured, for example, by the electron spin resonance method for the defect density in the film. From the results, it can be evaluated that the i-type a-Si film formed on the substrate 3 is a high quality film of 10 ¹⁴ to 10 ¹⁵ pieces / cm ³ grade.

According to the plasma CVD apparatus and the method using the apparatus according to the first embodiment of the present invention, as shown in the above description, it is possible to form a film by plasmatizing the mixed gas of the source gas and the hydrogen gas The film is formed while alternately repeating temporally the step 1 and the second step of performing hydrogen radical treatment on the surface of the thin film with the hydrogen radical in a time zone different from the time zone of the first step. It is possible to In the second step, since only hydrogen gas is present, hydrogen radicals are reliably generated, and the hydrogen radicals reliably reach the substrate surface by the diffusion phenomenon. As a result, termination of dangling bonds in the film surface and in the film by hydrogen radicals is performed, and a high quality silicon-based thin film can be formed.
Further, according to the plasma CVD apparatus and the method using the apparatus according to the first embodiment of the present invention, the temperature of the substrate 3 is set to 150 ° C. to 300 ° C. at which the adsorption rate of hydrogen radicals becomes high. When the hydrogen radicals are diffused to the surface of the silicon-based thin film and adsorbed, the adsorption rate of the hydrogen radicals is increased. As a result, termination of dangling bonds in the film surface and in the film is effectively performed.
According to the plasma CVD apparatus and the method using the apparatus according to the first embodiment of the present invention, it is possible to meet the needs for the formation of a high quality film (low defect density) using hydrogen radicals. Play.
Further, the defect density of the film formed by the conventional technique is 10 ¹⁵ to 10 ¹⁶ pieces / cm ³ , but according to the present invention, 10 ¹⁴ to 10 ¹⁵ pieces / one digit or two digits smaller than the conventional value. There is a possibility that the film quality can be improved to the cm ³ grade.

Second Embodiment
A plasma CVD apparatus and a film forming method using the apparatus according to a second embodiment of the present invention will be described.
First, the configuration of a plasma CVD apparatus according to a second embodiment of the present invention will be described with reference to FIG.
In FIG. 6, the same members as those of the plasma CVD apparatus according to the first embodiment of the present invention are denoted by the same reference numerals, and the redundant description will be omitted. In the drawings shown below, the scale of each member may differ from the actual one for convenience of explanation. Even between the drawings, the scale may be different from the actual one.
FIG. 6 is a schematic cross-sectional view for explaining a plasma CVD apparatus according to a second embodiment of the present invention.

Reference numeral 30a is a flat plate type electrode. The flat type electrode 30 a includes gas injection holes 36 a described later, and is fixed to the reaction vessel 1 via an insulating material 66 described later. The flat plate electrode 30a is supplied with high frequency power from the high frequency power supply 60 through the impedance matching device 61, the high frequency current introduction terminal 62, the vacuum cable 63 and the high frequency power supply point 65, and is a raw material ejected from the gas ejection holes 36a. Plasma the gas and hydrogen gas.
The code | symbol 66 is an insulating material. The insulating material 66 electrically insulates the flat plate type electrode 30 a from the reaction vessel 1. As the insulating material 66, a high purity ceramic material free from the generation of impurities is used.
Reference numeral 36a is a gas injection hole. Gas injection holes 36a is disposed in the electrode 30a, the silane source gas supplied from the material gas supply source 23a (S i _{H 4)} for jetting the hydrogen gas supplied from the gas and a hydrogen gas supply source 23c. The gas injection holes 36a have a diameter of about 0.2 mm to 1.0 mm, and are arranged at an interval of about 2 mm to 10 mm. Here, the diameter of the holes is 0.6 mm, and the distance between the holes is 5 mm.
Reference numeral 26a is a gas mixing box. The gas mixing box 26a supplies the raw material gas and the hydrogen gas supplied from the gas mixing pipe 26 to the gas injection holes 36a.
Reference numerals 2a and 2b denote exhaust holes. The exhaust holes 2a and 2b exhaust the pressure in the reaction vessel 1 so as to maintain the pressure at a predetermined value in cooperation with a vacuum pump (not shown) and a pressure gauge (not shown).

Next, referring to FIG. 6, the film forming method using the plasma CVD apparatus according to the second embodiment of the present invention, the i-type a-S _i film is a passivation film heterojunction solar cell example Take it and explain.
Here, take the i-type a-S _i film is a passivation film heterojunction solar cell as an example will be explained the film forming method, a plasma CVD apparatus i-type according to a second embodiment of the present invention Naturally, it is not limited to the formation of the a- _Si film.

When forming a p-type a-Si film of a solar cell, for example, a mixed gas of hydrogen (H ₂ ), diborane (B ₂ H ₆ ) and silane (S _i H ₄ ) may be selected as a source gas.
In the case of forming the n-type a-Si film of the solar cell, for example, hydrogen as a source gas _{(H 2)} and phosphine (PH ₃₎ and silane _(S i _{H 4)} better to choose the mixed gas of the gas .
When forming an amorphous silicon carbide (a-SiC) film, for example, hydrogen (H ₂ ), methane (CH ₄ ), ethane (C ₂ H ₆ ) or ethylene (C ₂ ) is used as a source gas. and H _6), is better to choose a mixed gas of silane _(S i _{H 4).}
When forming an amorphous silicon germanium (a-SiGe) film, for example, it is preferable to select a mixed gas of hydrogen (H ₂ ), germane (GeH ₄ ) and silane (S _i H ₄ ) as a source gas. good.
In the case of forming a _S i CN film as the sealing film of the organic EL device, as a source gas, e.g., hydrogen _{(H 2)} and ammonia (NH ₃₎ and monomethyl silane _{(CH 3} S i _{H 3)} It is good to choose mixed gas.
When forming a diamond like carbon (DLC) film, it is preferable to select, for example, hydrogen (H ₂ ) and methane (CH ₃ ) as source gases.

Here, the substrate 3 is, for example, a glass of size: 150 mm × 150 mm × thickness 0.63 mm.
The substrate transfer door between the load chamber and the reaction vessel 1 is opened in a load chamber (not shown) and the substrate 3 is placed on the substrate holding means 3a by a substrate transfer device (not shown). Then, the substrate transfer door (not shown) is closed.

Next, a vacuum pump (not shown) is operated to evacuate the reaction vessel from the exhaust holes 2a and 2b, and once the pressure inside the reaction vessel 1 reaches a vacuum level of, for example, 2.67 × 10 ⁻⁴ Pa (2 × 10 6). Lower to ^-6 Torr).
Then, the flow rate of silane _(S i _{H 4)} silane by a mass flow controller 24a of the gas _(S i _{H 4)} gas, about 10Sccm～300sccm, for example, set to 40 sccm.
Next, the flow rate of hydrogen gas is set to about 100 sccm to about 1000 sccm, for example, 200 sccm by the hydrogen gas mass flow controller 24c.
Next, the conditions of the intermittent gas supply of the raw material gas using the vacuum device solenoid valve 10 are set in the program of the control device 11 of the vacuum device solenoid valve. That is, the Deyutei (Duty) ratio of the cycle, including the time zone T ₁ and the raw material gas hours T ₂ is not supplied to supply the raw material gas is in the range of 30% to 90%, the time zone T to supply the raw material gas Set ₁
Setting time zone T ₂ to supply only the time period T ₁ and a hydrogen gas to supply the raw material gas, the time required for the hydrogen gas is substantially exhausted from the inside of the reaction vessel 1, i.e., the residence time of the hydrogen gas τ It is better to set it longer.

The gas supply conditions here are, for example, the volume of the reaction vessel (including the volume of the gas mixing box) = 0.3 mx 0.3 mx 0.2 m, the silane gas flow rate of the source gas = 40 sccm, the hydrogen gas flow rate = 200 sccm, and the pressure = 40 Pa Do.
If only hydrogen gas in the time zone T ₂ is supplied, the residence time τ of the hydrogen gas, is calculated as follows. That is, ^{τ = 40Pax0.018m 3 /(200sccmx1.69x10 -3 Pa ·} m 3 / s · sccm) = 2.1s.
In the time zone T _1, the residence time τ of the mixed gas of raw material gas and hydrogen, is calculated as follows. That is, τ = 40 Pax 0.018 m ³ / (240 sccm × 1.69 Pa · m ³ /s·sccm)=1.8 seconds.
Since the residence time τ of hydrogen is 2.1 seconds, for example, the duty ratio is 50%, and T ₁ = 3 seconds and T ₂ = 3 seconds.
Incidentally, in advance, to grasp the data in which the film characteristics and Deyutei (Duty) ratio and T ₁ and T ₂ of interest as a parameter may be set based on the data.
Next, the valve (not shown) of the source gas supply source 23a is opened, and the valve (not shown) of the hydrogen gas supply source 23c is opened. The flow rate of hydrogen gas is constant and supplied continuously.
Next, the intermittent gas supply means 22 is operated.
Then, the internal pressure of the reaction container 1 is set and maintained at 40 Pa (300 mTorr), which is the film forming condition, using a pressure gauge (not shown) and a vacuum pump (not shown).
The adjustment operation of the raw material gas and the hydrogen gas may be automatically performed by a computer control method using a solenoid valve, a digital flow control device or the like (not shown). In addition, the intermittent gas supply means 10 may be automatically operated by a computer control method.
The temperature of the substrate 3 is set and maintained in the range of 150 ° C. to 300 ° C., for example 200 ° C. The temperature of the substrate 3 is set in consideration of the fact that the adsorption rate of hydrogen radicals to the substrate surface becomes approximately 100% at a temperature around 200 ° C. and that hydrogen is desorbed from the film surface when the temperature is high. .

Next, high frequency power is supplied from the high frequency power source 60 to the electrode 30 a through the impedance matching unit 61, the high frequency current introduction terminal 62, and the high frequency power supply point 65. The high frequency power supplied to the electrode 30a is set as small as possible.
In order to form a high quality silicon film, it is preferable to lower the plasma electron temperature by reducing the power. For example, the power density of the supplied power may be set to 50 mW / cm ² or less, which is a value obtained by dividing the output of the high frequency power supply 60 by the surface area of the electrode 30 a to suppress generation of SiH ₂ radicals.

When high frequency power is supplied to the electrodes 30a, radicals in the time period T ₁ in which the raw material gas is supplied, the generated plasma 31 of a mixed gas of raw material gas and hydrogen gas as shown in FIG. 6, which is generated by the raw material gas plasma A film 33 is deposited on the surface of the substrate 3. Then, in the time period T ₂ is not supplied raw material gas, the termination of the dangling bonds due to the film surface and the film during the reaction of hydrogen radicals 35 generated by hydrogen plasma as shown in FIG. 6 is performed.
As a result, as shown in FIG. 5, an i-type a-Si film composed of deposited films 50, 51, 52, 53 and interfaces 55, 56, 57, 58 that receive dangling bonds is formed. Ru. Since the silicon-based thin film formed here is a film in which dangling bonds are terminated by a hydrogen radical surface reaction in the film forming process, it becomes a high quality a-Si film with a small defect density.
The defect density of the formed film is measured by a constant photocurrent method (CPM), an electron spin resonance method (ESR) or the like. _Si-H 2, Si-H bonds and Si-Si bonds analysis such, evaluation can be carried out infrared absorption spectrometry, secondary ion mass spectrometry, and by the run spectroscopy or the like.

Next, in the above-mentioned film formation, when a predetermined film formation time, for example, one minute has elapsed, the output of the high frequency power supply 60 is dropped to zero. Then, the valve (not shown) of the source gas supply source 23a and the valve (not shown) of the hydrogen gas supply source 23c are closed to stop the supply of the source gas and the hydrogen gas.
Here, the film forming time is an elapsed time from the time of generation of plasma by the electrode 30a. In the case of implementing the film forming time with high accuracy, it is preferable to dispose a shutter mechanism that can be opened and closed in the vicinity of the substrate 3 and use it.
Thereafter, a substrate transfer door (not shown) between the reaction chamber 1 and the unload chamber (not shown) is opened, and the substrate 3 is moved from the substrate holding means 3a to the unload chamber (not shown) by the substrate transfer device (not shown). Then, the substrate transfer door (not shown) is closed.

Since the substrate 3 of the film to be formed has disappeared in the substrate holding means 3a of the reaction chamber 1, the substrate 3 is newly moved from the load chamber (not shown). As described above, the substrate transfer door between the load chamber and the reaction chamber 1 is opened with the substrate 3 prepared in advance in the load chamber (not shown), and the substrate 3 is loaded on the substrate holding means 3a by the substrate transfer device (not shown). Place. Then, the substrate transfer door (not shown) is closed.
Then, the above-described film formation is repeated a predetermined number of times, for example, on 100 substrates.
The substrate moved to the unloading chamber is taken out from the substrate taking out door (not shown) to the outside. Size taken out: A substantially uniform high quality i-type a-Si film is formed on a 150 mm × 150 mm × 0.63 mm thick substrate 3.
The film quality of the obtained i-type a-Si film is measured, for example, by the electron spin resonance method for the defect density in the film. From the results, it can be evaluated that the i-type a-Si film formed on the substrate 3 is a high quality film of 10 ¹⁴ to 10 ¹⁵ pieces / cm ³ grade.

The plasma CVD apparatus and the film forming method using the apparatus according to the second embodiment of the present invention are film forming by plasmatizing a mixed gas of a source gas and a hydrogen gas as described in the above description. The film is formed while alternately repeating temporally the step 1 and the second step of performing hydrogen radical treatment on the surface of the thin film with the hydrogen radical in a time zone different from the time zone of the first step. It is possible to In the second step, since only hydrogen gas plasma is present, hydrogen radicals are reliably generated, and the hydrogen radicals reliably reach the substrate surface by the diffusion phenomenon. As a result, termination of dangling bonds in the film surface and in the film by hydrogen radicals is performed, and a high quality thin film can be formed.
Further, according to the plasma CVD apparatus and the method using the apparatus according to the second embodiment of the present invention, the temperature of the substrate 3 is set to 150 ° C. to 300 ° C. at which the adsorption rate of hydrogen radicals becomes high. When the hydrogen radicals are diffused and adsorbed onto the surface of the thin film, the adsorption rate of the hydrogen radicals is increased. As a result, termination of dangling bonds in the film surface and in the film is effectively performed.
The plasma CVD apparatus according to the second embodiment of the present invention has the effect of being able to meet the needs for the formation of a high quality film (low defect density) using hydrogen radicals.
Further, the defect density of the film formed by the conventional technique is 10 ¹⁵ to 10 ¹⁶ pieces / cm ³ grade, but according to the plasma CVD apparatus according to the second embodiment of the present invention, the conventional value is one digit There is a possibility that the film quality can be improved to 2 orders of 10 ¹⁴ to 10 ¹⁵ pieces / cm ³ .

1 ... reaction vessel,
2, 2a, 2b ... exhaust hole,
5 ・ ・ Exhaust pipe,
3 ... substrate,
3a ... substrate holding means,
10 ... Solenoid valve for vacuum device,
11 ・ ・ ・ Control device for solenoid valve for vacuum device,
23a ... source gas supply source,
24a ... mass flow controller for raw material gas,
23c ... hydrogen gas supply source,
24c ... mass flow controller for hydrogen gas,
25a, 25b: first and second source gas supply pipes,
25c ... hydrogen gas supply pipe,
26 ・ ・ ・ Gas mixing tube,
27 ··· Joint of source gas supply pipe for vacuum device,
29 · · · Gas junction,
30, 30a ... electrode,
31 ... Plasma of mixed gas,
32 ・ ・ ・ Hydrogen gas plasma,
33 ・ ・ ・ Various radicals which are precursors of film formation
35 ・ ・ ・ hydrogen radical,
36, 36a · · · · gas injection holes,
60 ... high frequency power supply,
61: Impedance matching device,
65: High frequency power supply point.

Claims (6)

The substrate holding means and the electrode are disposed opposite to each other in a reaction vessel equipped with an evacuation means, and an Si (silicon) containing gas, an N (nitrogen) containing gas, a C (carbon) containing gas, The source gas and the hydrogen gas are introduced by introducing a source gas comprising at least one selected from a boron-containing gas and a P (phosphorus) -containing gas and a hydrogen gas which is a dilution gas, and supplying high frequency power to the electrodes. In a plasma CVD apparatus for converting into plasma and forming a thin film on the surface of a substrate placed on the substrate holding means,
The hydrogen gas supply source and the source gas supply source are separated and disposed, and gas injection holes are provided in the electrode;
Piping-connecting the source gas source, an intermittent gas supply means for intermittently supplying the source gas to the gas injection holes, and the gas injection holes in this order;
Piping-connecting the hydrogen gas supply source, the hydrogen gas supply means for continuously supplying the hydrogen gas to the gas injection holes, and the gas injection holes in this order;
A first process of forming a thin film on the surface of a substrate mounted on the substrate holding means by plasmatizing a mixed gas of a source gas supplied from the intermittent gas supply means and a hydrogen gas supplied from the hydrogen gas supply means And a second step of performing hydrogen radical treatment of the thin film with hydrogen radicals generated by plasmatizing the hydrogen gas in a time zone different from the time zone of the first step, alternately in time A plasma CVD apparatus configured to form a film. The plasma CVD apparatus according to claim 1, wherein the intermittent gas supply means includes a mass flow controller and a vacuum solenoid valve. The solenoid valve for a vacuum, the raw material gas is in the cycle of the raw material gas hours T ₁ and supplied to the gas ejection hole comprises said gas ejection holes hours T ₂ is not supplied to the Deyutei (Duty) ratio, That is, time period T ₁ / (time period T ₁ in which the source gas is supplied + time period T ₂ in which the source gas is not supplied) in which the source gas is supplied is arbitrarily set in a range of 30% to 90%. The plasma CVD apparatus according to claim 2, further comprising a control device capable of performing the control. The plasma CVD apparatus according to any one of claims 1 to 3, wherein the electrode is formed of a hollow metal tube. The said electrode is flat type, The plasma CVD apparatus of any one of the Claims 1-3 characterized by the above-mentioned. The plasma CVD apparatus according to any one of claims 1 to 5, wherein the substrate holding means sets the temperature of the substrate to 150 ° C to 300 ° C.

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