JP2012142324A - Plasma processing method and processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma processing method and processing device capable of efficiently producing a film-forming seed, and forming a high quality thin film.SOLUTION: A plasma processing device comprises a reaction chamber 1 storing processed body 3 and forming a thin film on the processed body 3; a stage 4 disposed in the reaction chamber 1, and holding the processed body 3; a first gas supplying portion 10 for supplying first gas into the reaction chamber 1; a second gas supplying portion 14 for supplying second gas different from the first gas into the reaction chamber 1; and a high frequency plasma source 7 for generating high frequency discharge in the reaction chamber 1. In the reaction chamber 1, the first gas plasmatized by the high frequency discharge, and the second gas suppressing plasmatization are contacted with each other to cause decomposition reaction, and on the basis of the decomposition reaction, a thin film is formed on the processed body 3 held on the stage 4.

Description

  The present invention relates to a plasma processing method and a processing apparatus for forming a thin film on an object to be processed using plasma, and in particular, a microcrystalline silicon thin film useful for improving conversion efficiency in a solar cell and improving mobility in a thin film transistor, for example. The present invention relates to a plasma processing method and a processing apparatus that are preferably used for film formation.

Conventionally, microcrystalline silicon thin films have been widely used as absorption layers on the long wavelength side in thin film solar cells, channel layers in thin film transistors, and the like. It is known that when a microcrystalline silicon thin film is used as a channel layer in a thin film transistor, high mobility can be obtained as compared with the case where an amorphous silicon thin film is used.
Conventionally, a plasma CVD (Chemical Vapor Deposition) method has been widely used as a method for forming a silicon film as a material of a device such as a thin film solar cell or a thin film transistor. In the plasma CVD method, a mixed gas of a silane-based gas such as silane (SiH ₄ ) gas or disilane (Si ₂ H ₆ ) gas and hydrogen gas for dilution is decomposed by high-frequency discharge, and a silicon film is deposited on the substrate. .

  The plasma CVD method is classified into a capacitive coupling type and an inductive coupling type depending on a difference in plasma generation method. In the capacitively coupled plasma CVD method, a high frequency electric field is generated by applying a high frequency voltage between parallel plate electrodes, and the source gas is turned into plasma. This method requires a gas pressure as high as several hundred Pa with a slow film formation rate. For this reason, there is a possibility that the film quality of the film to be formed is deteriorated due to generation of a polymer by the secondary reaction, contamination by a substance adhering to the chamber wall due to discharge in the reaction chamber, and contamination by an adhering substance to the electrode.

  Therefore, recently, an inductively coupled plasma CVD method has been used instead of the capacitively coupled plasma CVD method. The inductively coupled plasma CVD method generates inductively coupled plasma by applying high frequency power to a high frequency coil. This method has a feature that the film forming speed can be increased because a high plasma density can be obtained.

For example, Patent Document 1 discloses such an inductively coupled plasma CVD method and an inductively coupled plasma CVD apparatus used therefor.
FIG. 5 is a diagram schematically showing the inductively coupled plasma CVD apparatus disclosed in Patent Document 1. As shown in FIG. As shown in FIG. 5, the inductively coupled plasma CVD apparatus includes a reaction chamber 101 and a spiral high-frequency coil 102 disposed outside the upper portion of the reaction chamber 101. A dielectric window 103 made of a quartz material having a silicon film containing no oxygen deposited on the surface is formed on the upper part of the reaction chamber 101. In the reaction chamber 101, a ring-shaped gas supply nozzle 105 for supplying a reaction gas is disposed between the dielectric window 103 and the base material 104 on which a thin film is to be formed.

Next, the operation of the inductively coupled plasma CVD apparatus shown in FIG. 5 will be described.
A reaction gas is supplied from a gas supply nozzle 105 into the reaction chamber 101 held in a vacuum state. Further, when high frequency power is applied to the high frequency coil 102, inductively coupled plasma is generated in the reaction chamber 101. The reaction gas is turned into plasma by the inductively coupled plasma generated in the reaction chamber 101, and a thin film is formed on the base material 104 by the plasmad reaction gas.

By the way, for example, Non-Patent Document 1 reports that, in the plasma CVD method using silane, the SiH ₃ radical, which is a long-lived species, is the main film-forming species. On the other hand, Si radicals, SiH radicals, SiH ₂ radicals, etc., which are decomposition products other than SiH ₃ radicals, are known as short-lived species that cause secondary reactions and tertiary reactions with source gases to produce higher order products. It has been. Eliminating these short-lived species is considered to be one of the factors contributing to the improvement of crystallinity.
Non-Patent Document 2 and Non-Patent Document 3 report that hydrogen radicals affect the formation of a microcrystalline silicon thin film.
Thus, it has been clarified that in order to form a high-quality microcrystalline silicon thin film, it is necessary to remove higher-order products and their precursors and increase SiH ₃ radicals and hydrogen radicals. Yes.

JP-A-10-27762

Akihisa Matsuda, “Dissociation Process of Source Gas in Silane Plasma”, Journal of Plasma and Fusion Research, Society of Plasma and Fusion, August 2000, Vol. 76, No. 8, p.760-765 A. Matsuda, “Growth mechanism of microcrystalline silicon obtained from reactive plasmas”, Thin Solid Films, USA, Elsevier B.V., January 11, 1999, 337, p.1-6 Shunsuke Ogawa, Shuichi Nonomura, “Development Trend of Microcrystalline Thin Film Solar Cells and Transparent Electrode Surface Protective Film”, Surface Technology, Surface Technology Association of Japan, 2008, Vol. 59, No. 3, p.155-160

  Conventionally, in a thin film silicon solar cell, by adopting a tandem structure in which an amorphous silicon layer and a microcrystalline silicon layer are stacked, efficient light absorption is achieved and conversion efficiency is improved. Yes. However, the amorphous silicon layer has a high light absorptance and achieves a light conversion rate of about 6 to 7% with a film thickness of about 0.2 to 0.3 μm, while the microcrystalline silicon layer has a light absorptivity. Although it is low and only a film thickness of about 1.5 to 2 μm is required, only a light conversion efficiency of about 3 to 5% can be obtained at present.

On the other hand, in thin film transistors, microcrystalline silicon may have higher responsiveness than amorphous silicon, and is expected to be applied to large substrates of G5 or higher (fifth generation or later), which is difficult to apply with polycrystalline silicon. ing.
In these applications, it is important to improve the film quality of the microcrystalline silicon thin film such as crystallinity and defect density. By improving the film quality, the solar cell can greatly contribute to the improvement of light conversion efficiency, and the thin film transistor can greatly contribute to the improvement of responsiveness.

In order to form a high-quality microcrystalline silicon thin film, it is said that hydrogen radicals and SiH ₃ radicals are necessary as described above. However, in general, in a space where silane (SiH ₄ ) and hydrogen (H ₂ ) are present simultaneously, dissociation of hydrogen proceeds and the amount of hydrogen radicals generated increases when the plasma energy is increased. At the same time, dissociation of silane proceeds. For this reason, the amount of silyl (SiH ₃ ) radicals that are film-forming species is relatively reduced. Conversely, when the plasma energy is lowered to suppress dissociation of silane, the rate of hydrogen dissociation also decreases, and as a result, the amount of hydrogen radicals generated decreases.
Thus, it is known that simultaneously increasing the amount of hydrogen radicals produced and the amount of SiH ₃ radicals produced is contradictory and difficult to achieve.

In the inductively coupled plasma CVD method, dissociation of silane proceeds by high-density plasma in the vicinity of the antenna, which is peculiar to this. Therefore, can not control their generation of SiH ₃ radicals, Si radicals than the amount of SiH ₃ radicals, SiH radicals, is the amount of SiH ₂ radicals increases. Radicals other than these SiH ₃ radicals undergo a secondary reaction or tertiary reaction with silane to generate dimers, trimers, etc., resulting in a problem that the defect density of the film increases and the film quality deteriorates.
For the above reasons, in the conventional plasma CVD method, it is difficult to increase both the generation amount of SiH ₃ radicals and the generation amount of hydrogen radicals in order to improve the film quality.

  The present invention has been made in order to solve the above-described conventional problems, and can provide a plasma processing method and a processing apparatus capable of efficiently generating a film-forming species and forming a high-quality thin film. The purpose is to provide.

That is, the plasma processing apparatus of the present invention is
A reaction chamber for storing a target object and forming a thin film on the target object;
A stage disposed in the reaction chamber and holding the object to be processed;
A first gas supply unit for supplying a first gas into the reaction chamber;
A second gas supply unit for supplying a second gas different from the first gas into the reaction chamber;
A high-frequency plasma source for generating a high-frequency discharge in the reaction chamber,
In the reaction chamber, the first gas converted into plasma by the high-frequency discharge is brought into contact with the second gas in which plasma generation is suppressed to cause a decomposition reaction. Based on the decomposition reaction, A thin film is formed on the object to be processed held on a stage.

Moreover, the plasma processing method of the present invention comprises:
Supplying a first gas and a second gas different from the first gas into a reaction chamber containing a target object;
In the reaction chamber, the first gas is turned into plasma by high frequency discharge,
The first gas converted to plasma and the second gas suppressed to plasma are brought into contact with each other to cause a decomposition reaction, and a thin film is formed on the object to be processed based on the decomposition reaction. It is characterized by doing.

The second gas is formed, for example, by the dissociated gas directly acting on the object to be processed. If such a gas is directly converted into plasma by high frequency discharge, a high-quality thin film is formed. It becomes difficult to do. For example, when dissociation of silane gas proceeds, desired SiH ₃ radicals cannot be generated successfully, and the amount of Si radicals, SiH radicals, and SiH ₂ radicals generated increases, and as a result, a high-quality microcrystalline silicon thin film is not formed.
According to the present invention, the first gas is turned into plasma by high frequency discharge, while the second gas is turned into plasma by high frequency discharge, and the second gas is suppressed from being turned into plasma. Since the decomposition reaction of the second gas occurs by the contact with the first gas, the dissociation of the second gas due to the high frequency discharge does not proceed at an early stage, and the film-forming species can be efficiently generated and the high quality can be obtained. A thin film can be formed.

Examples of the first gas include hydrogen gas or a gas containing hydrogen gas and one or more of rare gas, phosphine gas, and diborane gas. For example, hydrogen + rare gas, hydrogen + phosphine, hydrogen + phosphine + rare gas, hydrogen + diborane, hydrogen + diborane + rare gas, and the like are shown.
Examples of the second gas include silane-based gases such as silane gas and disilane gas for forming a microcrystalline silicon thin film.

  In the reaction chamber, for example, by providing a partition part for forming a plasma suppression area that suppresses plasma generation by high-frequency discharge, the plasma conversion of the second gas can be suppressed. In this case, the first gas supply unit supplies the first gas outside the plasma suppression area, and the second gas supply unit supplies the second gas into the plasma suppression area. Then, by configuring the first gas outside the plasma suppression area to flow into the plasma suppression area, the first gas that has been converted to plasma and the second plasma that has been suppressed from being converted into plasma within the plasma suppression area. Gas can be contacted. In addition, the said stage can be effectively formed by installing in the plasma suppression area side. As described above, the plasma suppression area is formed by the partition portion in the reaction chamber, so that the plasma formation of the second gas can be effectively suppressed, and the film forming species necessary for forming a high-quality thin film. Can be generated efficiently.

  In addition, the said division part can be comprised by the shielding board which partitions off the inside of a reaction chamber, for example. The shielding plate is preferably provided with a communication portion that communicates the outside of the plasma suppression area and the inside of the plasma suppression area so that the first gas outside the plasma suppression area can flow into the plasma suppression area. A plurality of communication portions can be formed on the shielding plate, and it is desirable to set the interval between the adjacent communication portions so as to be on the order of the mean free path of the first gas. Thus, by setting the space | interval of a communication part, after 1st gas passes through a communication part, it can fully spread on a to-be-processed object, and can be made to contact with 2nd gas efficiently. it can.

  The first gas supply unit is preferably provided so as to supply the first gas closer to the high-frequency plasma source than the object to be processed. By installing the first gas supply unit in this way, the first gas supplied from the first gas supply unit can be converted into a large amount of plasma at an early stage to improve the efficiency of the plasma processing.

  The second gas supply unit is preferably provided so as to supply the second gas in the vicinity of the object to be processed away from the high-frequency plasma source. For example, it is desirable to arrange the second gas outlet provided in the second gas supply unit in the vicinity of the object to be processed. By arranging the second gas supply unit in this way, the plasma conversion of the second gas supplied from the second gas supply unit can be more reliably suppressed. At this time, when the second gas is supplied into the reaction chamber by the second gas supply unit, it is desirable to blow out the second gas at a position where it does not directly contact the plasma source.

The high-frequency plasma source is preferably an inductively coupled type, but may be other types. In addition, the high-frequency plasma source can be arranged in various modes with respect to the reaction chamber.
For example, a plasma generation cylinder made of a dielectric can be provided on the outer periphery of the reaction chamber so as to protrude outward, and a high-frequency plasma source can be disposed on the outer periphery of such a plasma generation cylinder. By arranging the high-frequency plasma source on the outer periphery of the plasma generating cylinder provided so as to protrude outward from the outer periphery of the reaction chamber, high-frequency discharge from the high-frequency plasma source can be generated over the entire area of the reaction chamber. It can be avoided. That is, high frequency discharge can be locally generated in the plasma generating cylinder. Therefore, the plasma conversion of the second gas can be reliably suppressed.

  In addition, a gas supply cylinder made of a dielectric is installed in the reaction chamber as a part of the first gas supply unit, and the first gas is supplied into the reaction chamber through the gas supply cylinder. A high-frequency plasma source may be disposed in the reaction chamber and on the outer periphery of the gas supply cylinder. By arranging a high-frequency plasma source on the outer periphery of the gas supply cylinder in the reaction chamber, high-frequency discharge from the high-frequency plasma source effectively reaches the first gas, and the first gas converted into plasma is supplied to the gas. It can be quickly transferred to a desired position through the cylinder. For this reason, it is desirable that the gas supply cylinder has an opening extending in the direction of the plasma suppression area and facing the plasma suppression area. In addition, the high-frequency plasma can be applied to a limited area in the vicinity of the gas supply cylinder, and it is possible to avoid the influence over the entire region in the reaction chamber. For this reason, it is desirable that the gas supply cylinder has a length that does not reach the plasma suppression area, and the high-frequency plasma source is disposed at a position away from the plasma suppression area. Therefore, the first gas can be reliably converted into plasma by the above configuration, and the plasma conversion of the second gas can be more reliably suppressed.

  Various methods can be used to introduce the first gas outside the plasma suppression area into the plasma suppression area. For example, a method using a pressure difference in the reaction chamber can be used. Specifically, the outside of the plasma suppression area is set to a positive pressure with respect to the inside of the plasma suppression area. By providing such a pressure difference, the first gas outside the plasma suppression area can be easily introduced into the plasma suppression area.

That is, according to the present invention, the first gas converted into plasma by the high-frequency discharge and the second gas suppressed in plasma generation are brought into contact with each other to cause a decomposition reaction of the second gas, and the object to be processed A high-quality thin film can be efficiently formed thereon. For example, when a hydrogen gas is supplied as a first gas into a reaction chamber and a silane gas is supplied as a second gas to form a microcrystalline silicon film on an object to be processed, a high quality microcrystalline silicon thin film is formed. The generation of SiH ₃ radicals necessary for the film formation and the generation of hydrogen radicals necessary for the formation of the crystalline silicon thin film can be performed independently, and a high degree of crystallinity based on the reaction of these radicals. A quality microcrystalline silicon thin film can be formed.

It is explanatory drawing which shows one Embodiment of the plasma processing apparatus of this invention. Similarly, it is the top view and bottom view which show the planar structure of the 2nd gas supply part (shielding plate). Similarly, it is the schematic of the plasma processing apparatus of other embodiment which changed the installation position of the plasma source in the reaction chamber. Similarly, it is the schematic of the plasma processing apparatus of other embodiment which gives a potential difference to a reaction chamber, a 2nd gas supply part, and a stage. It is a figure which shows the conventional inductively coupled plasma CVD apparatus typically.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of the plasma processing apparatus of this embodiment.
This plasma processing apparatus has a reaction chamber 1 capable of maintaining the inside in a vacuum state, and a vacuum exhaust system 2 for connecting the inside of the reaction chamber 1 to a vacuum state is connected to the reaction chamber 1. .
In addition, a stage 4 that holds an object to be processed 3 is disposed on the bottom side of the reaction chamber 1. The object 3 is a substrate such as a semiconductor substrate or a glass substrate, for example.
A bias power source 5 for applying a bias voltage to the stage 4 is connected to the stage 4. Furthermore, a heater (not shown) for heating the workpiece 3 on the stage 4 is embedded in the stage 4.

  A plurality of plasma generation cylinders 6 communicating with the reaction chamber 1 are provided on the outer periphery of the upper side of the reaction chamber 1 so as to protrude outward. The plasma generation cylinder 6 is made of a dielectric. A high-frequency plasma source 7 that generates a high-frequency discharge in the plasma generation cylinder 6 is installed on the outer periphery of each plasma generation cylinder 6. A high frequency power source 9 is connected to one end of the high frequency plasma source 7 via a matching box 8 and the other end is connected to a ground potential.

A plurality of plasma generation cylinders 6 are connected to a first gas supply unit 10 that supplies a first gas into the reaction chamber 1. The first gas supply unit 10 includes a first gas source 19 installed outside the reaction chamber 1, a plurality of first gas supply pipes 12 connected to the first gas source 19, and each of the first gas supply pipes 12. A first gas blowing section 13 connected to the tip and disposed on the top plate in the plasma generating cylinder 6; A first gas outlet 13 a formed downward is provided at the tip of the first gas outlet 13.
The first gas outlet 13 a is located on the inner peripheral side of the high-frequency plasma source 7 and has a gas blowing direction in the high-frequency radiation direction of the high-frequency plasma source 7. That is, the first gas supply unit 10 is provided to supply the first gas in the vicinity of the high-frequency plasma source 7.

  In the case where a microcrystalline silicon thin film is formed on the object 3 to be processed, as the first gas, a gas containing hydrogen gas or one of hydrogen gas and rare gas, phosphine gas, and diborane gas is used. By including phosphine gas in the first gas, a microcrystalline silicon thin film doped with phosphorus is formed. In addition, by containing diborane gas in the first gas, a microcrystalline silicon thin film doped with boron is formed.

Further, a second gas supply unit 14 for supplying a second gas into the reaction chamber 1 is connected to the reaction chamber 1, and a second gas supply unit 14 that is a part of the second gas supply unit 14 is provided in the reaction chamber 1. A gas blowing part 17 is arranged. The second gas supply unit 14 includes a second gas source 15 installed outside the reaction chamber 1, a plurality of second gas supply pipes 16 connected to the second gas source 15, and each second gas supply pipe 16. And a second gas blowing part 17 disposed in the plasma generating cylinder 6.
The second gas supply pipe 16 is made of metal and prevents high frequency from entering the inside. The second gas supply pipe 16 penetrates from the outside of the reaction chamber 1 to the outside of the plasma generating cylinder 6 or between the plasma generating cylinders 6, 6 and into the reaction chamber 1. Is provided. The second gas blowing portion 17 is located below the plasma generating cylinder 6 and is located closer to the object to be processed 3 disposed on the stage 4 than the high-frequency plasma source 7. As a result, the second gas is supplied to the vicinity of the object 3 without directly touching the high frequency discharge and without being affected by the high frequency discharge.

FIGS. 2A and 2B show a planar structure around the second gas blowing portion 17, in which FIG. 2A is a plan view and FIG. 2B is a bottom view.
In the reaction chamber 1, a shielding plate 20 that divides the inside of the chamber 1 up and down is disposed immediately above the stage 4, and the second gas supply pipe 16 is connected to the shielding plate 20, respectively. It is open. The lower side of the opening of the second gas supply pipe 16 is the second gas blowing portion 17. Further, the shielding plate 20 is formed with a communicating portion 21 that penetrates up and down between locations where the second gas supply pipe 16 is connected.
The shielding plate 20 corresponds to a partition portion of the present invention that divides the inside of the reaction chamber 1 up and down, the upper space thereof is assigned to the plasma area 1a outside the plasma suppression area, and the lower space is the plasma suppression area. Assigned to 1b. It is desirable that the shielding plate 20 be made of a material that does not easily allow high frequencies to enter from below to below. Moreover, the communication part 21 should just have sufficient magnitude | size for the 1st gas in the plasma area 1a to flow in into the plasma suppression area 1b, and if it forms too much, intrusion of a high frequency will be permitted. This is not preferable because it causes the second gas in the plasma suppression area 1b to become plasma. Further, the interval between the adjacent communication portions 21 is about the order of the mean free path of the first gas in the plasma area 1a in the vacuum state.

The communication portion 21 can be formed as a tapered hole having a diameter that gradually increases from the upper surface side to the lower surface side of the shielding plate 20. With this shape, the first gas flowing into the plasma suppression area 1b from the plasma area 1a is effectively diffused in the plasma suppression area 1b, and effective contact with the second gas becomes possible. The tapered hole shape prevents the first gas flowing into the plasma suppression area 1b from flowing back into the plasma area 1a.
In addition, by setting the plasma area 1a to a positive pressure with respect to the plasma suppression area 1b, the gas quickly moves from the plasma area 1a to the plasma suppression area 1b through the communication portion 21. The positive pressure can be realized by setting the pressure in the plasma area 1a and the pressure in the plasma suppression area 1b, and can also be realized with gentle exhaust by the vacuum exhaust system 2 connected to the plasma suppression area 1b. Can do.

A plurality of second gas outlets 17 corresponding to the openings of the second gas supply pipe 16 are provided below the shielding plate 20. The second gas blowout part 17 has a plate-like shape in which a second gas blowout opening 17a composed of a plurality of small holes is formed, and is located between the communication parts 21 and 21, It is fixed to the shielding plate 20 with a ventilation space vertically. Therefore, the second gas blowout portion 17 can blow out the second gas downward through the second gas blowout port 17a.
Further, the shielding plate 20 and the second gas blowing part 17 can blow gas from the side of the second gas blowing part 17. That is, the guide protrusion 20a provided below the shielding plate 20 is disposed on the periphery of the second gas blowing portion 17 with a small gap. The guide protrusion 20a is formed with a tapered guide surface whose inner peripheral surface is directed downward and the inner diameter is increased, and in accordance with this, the outer peripheral surface of the second gas blowing portion 17 is directed downward to increase in diameter. A tapered surface is formed so that the tapered guide surface and the tapered surface are opposed to each other. The second gas can be blown out obliquely downward from the gap between the tapered guide surface and the tapered surface.
That is, in the 2nd gas blowing part 17, 2nd gas is blown out from the downward direction and a side.

Next, the operation of the plasma processing apparatus will be described.
First, the workpiece 3 is held on the stage 4. Next, the inside of the reaction chamber 1 is evacuated by the evacuation system 2, and the inside of the reaction chamber 1 is brought into a vacuum state with a predetermined degree of vacuum. After the inside of the reaction chamber 1 reaches a predetermined degree of vacuum, the target object 3 on the stage 4 is heated to about 300 ° C., for example, by a heater embedded in the stage 4. Further, a predetermined bias voltage is applied to the stage 4 by the bias power source 5. By applying a bias voltage to the stage 4, gas is drawn to the stage 4 side, and plasma processing can be performed efficiently. At this time, the evacuation system 2 continues evacuation so that the reaction chamber 1 is maintained in a predetermined pressure state.

Next, in the first gas supply unit 10, the first gas is supplied to the first gas blowing unit 13 through the first gas source 19 and the first gas supply pipe 12. At the same time, the second gas supply unit 14 supplies the second gas to the second gas blowing unit 17 through the second gas source 15 and the second gas supply pipe 16. At this time, both gases are supplied to the plasma suppression area 1b so that the plasma area 1a has a positive pressure, and evacuation by the vacuum exhaust system 2 is performed.
In this embodiment, in order to form a microcrystalline silicon thin film on the object 3 to be processed, hydrogen is used as the first gas, and for example, silane (SiH ₄ ) gas or disilane (Si ₂ H ₆ ) is used as the second gas. ) Use gas. However, as described above, the first gas and the second gas are not limited to the above in the present invention.

A high frequency voltage is applied to the high frequency plasma source 7 by a high frequency power source 9 through a matching box 8. In the plasma generation cylinder 6, the first gas is blown out through the first gas outlet 13 a of the first gas outlet 13. In the plasma generating cylinder 6, inductively coupled plasma is generated by high frequency discharge from the high frequency plasma source 7, and the first gas is turned into plasma at a high density of, for example, an electron density of 10 ¹¹ cm ⁻¹ or more.
The first gas converted into plasma gradually flows into the plasma suppression area from the plasma area 1a having a positive pressure through the communication portion 21.

In the plasma suppression area 1b, the second gas is supplied through the second gas blowing unit 17 as described above. At this time, the second gas is not affected by the high-frequency discharge generated by the high-frequency plasma source 7 and is supplied into the plasma suppression area 1b with the plasma generation suppressed.
In the plasma suppression area 1b, the first gas that has been converted to plasma comes into contact with the second gas that has been suppressed from being converted to plasma, and the second gas undergoes a decomposition reaction. As a result, a thin film is formed on the workpiece 3.
Specifically, when hydrogen gas is used as the first gas and silane (SiH ₄ ) gas is used as the second gas, the plasma conversion of the hydrogen gas while suppressing the plasma conversion of the silane gas by the high-frequency plasma source 7 is performed. The generated hydrogen radical causes a decomposition reaction of silane gas. Thereby, accelerate the decomposition of the silane gas to SiH ₃ radicals as a film forming species, Si radicals, SiH radicals, it is possible to suppress the generation of SiH ₂ radicals. In this way, the amount of SiH ₃ radicals and the amount of hydrogen radicals can be increased simultaneously, and a high-quality microcrystalline silicon thin film can be formed on the object 3 to be processed.
The thin film formed by the plasma processing apparatus of the present invention is of high quality, and when a device such as a solar cell or a thin film transistor is formed using the thin film, good electrical characteristics can be obtained.

  The positional relationship between the high-frequency plasma source 7 and the first gas blowing unit 13 is not limited to the above, and can be changed as appropriate, and the number of each can be changed as appropriate.

(Embodiment 2)
In the above embodiment, the installation position of the high-frequency plasma source 7 is outside the reaction chamber 1, but the installation position of the high-frequency plasma source may be inside the reaction chamber 1.
FIG. 3 shows another embodiment in which the installation position of the high-frequency plasma source 7 is changed into the reaction chamber 1. In addition, about the structure similar to the said Embodiment 1, the same code | symbol is attached | subjected and the description is abbreviate | omitted or simplified.
As shown in FIG. 3, in the plasma area 1 a in the reaction chamber 1, a gas supply cylinder 25 made of a dielectric is suspended from the top plate portion of the reaction chamber 1. A first gas supply pipe 12 that supplies a first gas to the gas supply cylinder 25 is connected to the gas supply cylinder 25, and the first gas supply pipe 12 is connected to a first gas source 19. Yes. Therefore, in this embodiment, the first gas source 10, the first gas supply pipe 12, and the gas supply cylinder 25 constitute the first gas supply unit 10.

  A high-frequency plasma source 26 is arranged on the outer periphery of the gas supply cylinder 25 so as to be located in the reaction chamber 1. One end of the high-frequency plasma source 26 is pulled out from the upper part of the reaction chamber 1 and connected to the high-frequency power source 9 through the matching box 8. The other end of the high-frequency plasma source 26 is drawn out from the upper part of the reaction chamber 1 and connected to the ground potential.

  The first gas supplied to the gas supply cylinder 25 through the first gas source 19 and the first gas supply pipe 12 receives high frequency discharge from the high frequency plasma source 26 while moving in the gas supply cylinder 25 to be converted into plasma. Is done. Further, even after the gas supply cylinder 25 is blown out, the first gas is turned into plasma by the high frequency discharge. The first gas converted into plasma flows from the plasma area 1a into the plasma suppression area 1b in the same manner as in the above embodiment, and comes into contact with the second gas whose plasma generation is suppressed in the plasma suppression area 1b. Provided for processing. Thus, the high frequency plasma source 26 may be installed in the reaction chamber 1.

(Embodiment 3)
In the above description, the bias power source 5 is connected to the stage 4. However, a potential difference is applied between the shielding plate 20 and each member of the stage 4 by further connecting a bias power source to the shielding plate 20. May be.
FIG. 4 shows another embodiment in which a potential difference is applied between each member of the reaction chamber 1, the shielding plate 20, and the stage 4. In addition, about the structure similar to the said Embodiment 1, the same code | symbol is attached | subjected and the description is abbreviate | omitted or simplified.
As shown in FIG. 4, a bias power source 5 is connected to the stage 4 as described above. In addition, a bias power supply 28 for applying a bias voltage to the shielding plate 20 is connected to the shielding plate 20. Furthermore, the reaction chamber 1 is connected to the ground potential. For example, by applying the potential of the stage 4> the shielding plate 20> the potential of the reaction chamber 1, the gas is attracted from the plasma area to the shielding plate 20, and further the gas is attracted to the stage 4 side. Plasma processing can be efficiently performed on the processing body 3.

  As mentioned above, although this invention was demonstrated based on the said embodiment, this invention is not limited to description of the said embodiment, A suitable change is possible unless it deviates from the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Reaction chamber 1a Plasma area 1b Plasma suppression area 3 To-be-processed object 4 Stage 5 Bias power supply 7 High frequency plasma source 10 1st gas supply part 13 1st gas blowing part 13a 1st gas blower outlet 14 2nd gas supply part 17 2nd Gas outlet 17a Second gas outlet 20 Shield plate 21 Communicator 26 High frequency plasma source

Claims (10)

A reaction chamber for storing a target object and forming a thin film on the target object;
A stage disposed in the reaction chamber and holding the object to be processed;
A first gas supply unit for supplying a first gas into the reaction chamber;
A second gas supply unit for supplying a second gas different from the first gas into the reaction chamber;
A high-frequency plasma source for generating a high-frequency discharge in the reaction chamber,
In the reaction chamber, the first gas converted into plasma by the high-frequency discharge is brought into contact with the second gas in which plasma generation is suppressed to cause a decomposition reaction. Based on the decomposition reaction, A plasma processing apparatus configured to form a thin film on the object to be processed held on a stage. A partition part that forms a plasma suppression area that suppresses the plasma generation by the high-frequency discharge in the reaction chamber,
The first gas supply unit supplies the first gas outside the plasma suppression area,
The second gas supply unit supplies the second gas into the plasma suppression area,
The said plasma suppression area is comprised so that the said 1st gas outside this plasma suppression area may flow in, and the said stage is installed in this plasma suppression area side. Plasma processing equipment.   The partition part is constituted by a shielding plate for partitioning the inside of the reaction chamber, and a communication part is formed on the shielding plate to communicate the outside of the plasma suppression area and the inside of the plasma suppression area. The plasma processing apparatus according to claim 2. The first gas supply unit is provided to supply a first gas closer to the high-frequency plasma source than the object to be processed;
The said 2nd gas supply part is provided so that it may leave | separate from the said high frequency plasma source, and may supply 2nd gas to the vicinity of the said to-be-processed object. Plasma processing equipment. A plasma generating cylinder made of a dielectric is provided on the outer periphery of the reaction chamber so as to protrude outward.
The plasma processing apparatus according to claim 1, wherein the high-frequency plasma source is disposed on an outer periphery of the plasma generation cylinder. The first gas supply unit has a gas supply cylinder made of a dielectric material installed in the reaction chamber,
The plasma processing apparatus according to claim 1, wherein the high-frequency plasma source is disposed in the reaction chamber and on an outer periphery of the gas supply cylinder. The first gas includes hydrogen gas or hydrogen gas and one or more of rare gas, phosphine gas and diborane gas,
The plasma processing apparatus according to claim 1, wherein the second gas contains one or both of monosilane gas and disilane gas. Supplying a first gas and a second gas different from the first gas into a reaction chamber containing a target object;
In the reaction chamber, the first gas is turned into plasma by high frequency discharge,
The first gas converted to plasma and the second gas suppressed to plasma are brought into contact with each other to cause a decomposition reaction, and a thin film is formed on the object to be processed based on the decomposition reaction. And a plasma processing method. In the reaction chamber, a plasma suppression area that suppresses the plasma generation by the high-frequency discharge is formed,
Supplying the second gas into the plasma suppression area and supplying the first gas outside the plasma suppression area to turn it into plasma,
The first gas converted into plasma is introduced into the plasma suppression area, and the second gas and the first gas converted into plasma are brought into contact with each other in the plasma suppression area. Item 9. The plasma processing method according to Item 8.   The outside of the plasma suppression area is made positive with respect to the inside of the plasma suppression area, and the first gas outside the plasma suppression area is introduced into the plasma suppression area due to a pressure difference between the inside and outside of the plasma suppression area. The plasma processing method according to claim 9.

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