JP2011179096A - Thin film forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin film forming device formable of a thin film in a short time by enhancing plasma generation density when forming the thin film on a substrate by using plasma. <P>SOLUTION: The thin film forming device for forming the thin film on the substrate comprises: a film deposition container provided with a deposition space for forming the thin film on the substrate in an evacuated state; a starting gas introduction part for introducing a starting gas for thin film into the deposition space in the film deposition container; and a plasma electrode part for generating plasma by using the starting gas for thin film in the deposition space. The plasma electrode part is made of a sheet member in which an electric current flows from one side edge surface to the other side edge surface, wherein a first principal plane of the sheet member faces the deposition space and, on the first principal surface, an electrode plate provided with a plurality of groove-like recessed parts extended along the direction in which the electric current flows is disposed as an electrode for plasma generation. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

Conventionally, a CVD (Chemical Vapor Deposition) apparatus is used to form a thin film on a substrate. In particular, a process of forming an amorphous Si thin film used for a thin film solar cell on a glass substrate by using a CVD apparatus has attracted attention. In the formation of the amorphous Si thin film, for example, monosilane (SiH ₄ ) is turned into plasma to form the amorphous Si thin film on the glass substrate. In recent years, thin-film solar cell panels have become larger, and it is desired to form a uniform amorphous Si thin film on a large panel. For this reason, in a plasma CVD apparatus, it is necessary to form a high-density plasma uniformly.

For example, as an example of a plasma CVD apparatus, a plasma generation method in which a plurality of high-frequency antennas are installed in a plasma generation chamber, and inductively coupled plasma is generated by applying high-frequency power to the plasma generation chamber gas with the high-frequency antenna; A plasma generator is known (Patent Document 1).
In the plasma generation method and the plasma generation apparatus, at least some of the plurality of high-frequency antennas are sequentially arranged adjacent to each other, and the adjacent ones are arranged in parallel with each other facing each other. Install. Further, the plurality of high-frequency antennas are installed adjacent to each other in such a manner that the adjacent antennas are arranged in parallel with each other facing each other. The electron temperature in the inductively coupled plasma is controlled by controlling the phase of the high frequency voltage applied to each of the high frequency antennas.

There is also known a plasma generation device including a vacuum vessel, an opening provided on a wall surface of the vacuum vessel, and a plate-like high-frequency antenna conductor attached so as to cover the opening in an airtight manner (patent) Reference 2).
Since the plasma generation apparatus has a structure in which a high-frequency antenna conductor is attached to the opening of the plasma generation apparatus, it is possible to generate plasma with high uniformity over a wide range.

JP 2007-149639 A WO2009 / 142016A1

  FIG. 5A is a diagram illustrating a simplified configuration of an example of a plasma film forming apparatus using a plate-shaped high-frequency antenna conductor. In the plasma film forming apparatus 100 shown in FIG. 5A, an electrode plate 102 is provided outside the film forming chamber of the film forming container 104 with a partition wall 106 therebetween, and on the surface of the partition wall 106 facing the film forming space. Is provided with a dielectric 108. A glass substrate G for forming a thin film is disposed at a position facing the dielectric 108. The glass substrate G is placed on a susceptor 112 provided on the heater 110.

FIG. 5B is a schematic perspective view of the electrode plate 102 that generates a magnetic field in the film formation space. The electrode plate 102 is a plate-like electrode as shown in FIG. One end face of the electrode plate 102 is connected to a high frequency power supply of several tens of MHz, and the other end face of the electrode plate 102 is grounded. In the electrode plate 102, current flows in the X direction. In the method of generating plasma using the electrode plate 102, the plasma is generated using the generated magnetic field, unlike the above-described apparatus that generates plasma using high voltage generated by a plurality of adjacent high frequency antennas. Is done.
However, the density of the plasma generated by the electrode plate 102 is not sufficient for forming an amorphous Si thin film, and there is a problem that the film forming speed is slow. In addition, the above-described known plasma generation method and plasma generation apparatus that generate inductively coupled plasma by supplying high-frequency power to a plurality of high-frequency antennas have a problem that a sufficient plasma density cannot be generated uniformly. is there.

  Therefore, in order to solve the above problems, the present invention provides a thin film forming apparatus capable of efficiently forming a thin film by improving the plasma density when forming a thin film on a substrate using plasma. With the goal.

One aspect of the present invention is a thin film forming apparatus for forming a thin film on a substrate,
A film formation container having a film formation space for forming a thin film on a substrate in a reduced pressure state;
A raw material gas introduction section for introducing a raw material gas for a thin film into the film formation space of the film formation container;
A plasma electrode unit for generating plasma using the thin film source gas in the film formation space;
The plasma electrode portion is a plate member in which an electric current flows from one end surface to the other end surface, and is arranged so that a first main surface of the plate member faces the film formation space, and the first main surface In addition, an electrode plate provided with a plurality of groove-like recesses extending along the current direction is provided as an electrode for plasma generation.

  In that case, it is preferable that the surface area of the 2nd main surface facing the said 1st main surface of the said electrode plate is smaller than the surface area of the said 1st main surface.

  Moreover, it is preferable that the 2nd main surface facing the said 1st main surface is equipped with the unevenness | corrugation extended along the direction orthogonal to the said electric current direction.

When the electrode plate is referred to as a first electrode plate,
The plasma electrode portion is a plate member in which an electric current flows from one end surface to the other end surface, and is arranged such that a third main surface of the plate member faces the film formation space, and the third main surface A second electrode plate provided with a plurality of groove-shaped recesses extending along the current direction, spaced apart from the first electrode plate,
The second electrode plate is arranged in parallel with the first electrode plate,
In each of the first electrode plate and the second electrode plate, the depth of the recess located at the end on the side where the first electrode plate and the second electrode plate are adjacent to each other is the depth of the other recess. It is preferably deeper than the depth.

  It is preferable that a distance between the deepest portion of the concave portion of the electrode plate and the second main surface is longer than 0.2 mm.

  In the above-described thin film forming apparatus, the generated plasma density can be increased and the thin film can be formed efficiently.

It is the schematic showing the structure of the thin film forming apparatus which is one Embodiment of this invention. It is a perspective view which shows an example of the electrode plate used for the thin film forming apparatus shown in FIG. It is a perspective view which shows the other example of the electrode plate used for the thin film forming apparatus shown in FIG. It is a figure which shows the other example of the electrode plate used for the thin film forming apparatus shown in FIG. (A), (b) is a figure explaining the example of the electrode plate used for the conventional thin film formation apparatus.

Hereinafter, the thin film forming apparatus of the present invention will be described in detail.
FIG. 1 is a schematic diagram showing a configuration of a thin film forming apparatus 10 according to an embodiment of the present invention.

  A thin film forming apparatus 10 shown in FIG. 1 is a CVD apparatus that forms a thin film on a substrate using generated plasma. The thin film forming apparatus 10 is a system that generates plasma by a magnetic field generated by a current flowing through an electrode plate. This method is different from a method in which plasma is generated by a high voltage generated by resonance of an antenna element such as a monopole antenna.

(Thin film forming equipment)
Hereinafter, the thin film forming apparatus 10 will be described using an example of forming an amorphous Si thin film as a thin film.
The thin film forming apparatus 10 includes a power supply unit 12, a film forming container 14, a gas supply unit 16, and a gas exhaust unit 18.

The power supply unit 12 includes a high frequency power supply 22, a high frequency cable 24, a matching box 26, transmission lines 28 and 29, and an electrode plate 30.
The high frequency power supply 22 supplies, for example, high frequency power of several tens of MHz to the electrode plate 30 at 100 to 3000 W. The matching box 26 matches impedance so that power supplied through the high-frequency cable 24 is efficiently supplied to the electrode plate 30. The matching box 26 includes a known matching circuit provided with elements such as a capacitor and an inductor.
The transmission line 28 extending from the matching box 26 is, for example, a copper plate-shaped transmission line having a certain width, and can pass a current of, for example, several amperes to the electrode plate 30.
The transmission line 29 extends from the electrode plate 30 and is grounded.

  The electrode plate 30 is a plate member long in one direction fixed on a partition wall 32 to be described later, and the first main surface of the plate member faces the film formation space in the film formation container 14 with respect to the partition wall 32. Are arranged in parallel. The electrode plate 30 allows current to flow along the longitudinal direction of the plate member between the end face to which the transmission line 28 is connected and the end face to which the transmission line 29 is connected. The electrode plate 30 is provided with a plurality of recesses extending along the direction of current flow on the first main surface. This point will be described later.

  The film formation container 14 has an internal space 38 in the container, and the internal space 38 is divided into an upper space and a lower film formation space 40 by a partition wall 32. The film formation container 14 is formed of a material such as aluminum, for example, and is sealed so that the internal space 38 can be in a reduced pressure state of 1 to 100 Pa. A matching box 26, transmission lines 28 and 29, and an electrode plate 30 are provided in the upper space of the film forming container 14. An electrode plate 30 is fixed to the side of the partition wall 32 facing the upper space. An insulating member 34 is provided around the electrode plate 30 to insulate the surrounding partition wall 32. On the other hand, a dielectric 36 is provided on the side of the partition wall 32 facing the film formation space 40. For the dielectric 36, for example, a quartz plate is used. The reason why the dielectric 36 is provided is to prevent the electrode plate 30 from being corroded by plasma and efficiently propagate power to the plasma.

In the film formation space 40 of the film formation container 14, a heater 42, a susceptor 44, and an elevating mechanism 46 are provided.
The heater 42 heats the glass substrate 20 placed on the susceptor 44 to a predetermined temperature, for example, about 250 ° C.
The susceptor 44 places the glass substrate 20 thereon.
The elevating mechanism 46 moves the susceptor 44 on which the glass substrate 20 is placed together with the heater 42 freely in the film forming space 40. In the film forming process stage, the glass substrate 20 is set at a predetermined position so as to be close to the electrode plate 30.

The gas supply unit 16 includes a gas tank 48 and a mass flow controller 50.
The gas tank 48 stores monosilane gas (SiH ₄ ), which is a raw material gas for a thin film.
The mass flow controller 50 is a part that adjusts the flow rate of the monosilane gas. For example, the flow rate of the monosilane gas can be adjusted according to the results of the film thickness and film quality of the formed film. The monosilane gas is supplied into the film formation space 40 from the side wall of the film formation space 40 of the film formation container 14.

The gas exhaust unit 18 includes an exhaust pipe extending from a side wall in the film formation space 40, a turbo molecular pump 52, and a dry pump 54. The dry pump 54 roughens the inside of the film formation space 40, and the turbo molecular pump 52 maintains the pressure in the film formation space 40 with a high accuracy to 1 × 10 ⁻⁴ Pa or less. The turbo molecular pump 52 and the dry pump 54 are connected by an exhaust pipe.

(Electrode plate)
FIG. 2 is a perspective view of an example of the electrode plate 30 used in the power supply unit 12.
The electrode plate 30 is fixed to the partition wall 32 so that the first main surface 30 a of the electrode plate 30 faces the internal space 40. The first main surface 30a is provided with a plurality of groove-shaped recesses 30c extending along the current direction (X direction in the figure). For example, copper, aluminum, or the like is used for the electrode plate 30.

  In the example illustrated in FIG. 2, four grooves extending in the X direction in which the concave portions are formed on the inclined surfaces that are linearly inclined are provided as the concave portions 30 c. For this reason, in the electrode plate 30, the surface area of the first main surface 30a is larger than the surface area of the second main surface 30b opposite to the first main surface 30a. The high-frequency current flowing through the electrode plate 30 gathers on the surface layers of the first main surface 30a and the second main surface 30b due to surface effects. However, since the first main surface has a larger surface area than the second main surface 30b, the current flowing through the surface layer of the first main surface 30a is larger than that of the second main surface 30b. For this reason, the magnetic field formed in the film-forming space 40 due to the current flowing through the surface layer of the first main surface 30a becomes larger than that of the electrode plate (see FIG. 5B) not provided with the recess 30c. . For this reason, the plasma generated by the magnetic field is densified as compared with the conventional case. Moreover, since the magnetic field is generated using the electrode plate 30, the thin film forming apparatus 10 can generate a uniform magnetic field over a wide range, and as a result, can generate high-density plasma over a wide range.

  The surface layer of the current flowing through the electrode plate 30 is determined depending on the electrical resistivity of the electrode plate 30, the frequency of the current, and the magnetic permeability of the electrode plate 30, but copper or aluminum is used as the material of the electrode plate 30, When the current frequency is set to several tens of MHz, the depth of the surface layer is about 0.1 mm. Therefore, the thickness of the electrode plate 20 is preferably thicker than 0.2 mm in consideration of the current flowing through the surface layers of the first main surface 30a and the second main surface 30b. That is, it is preferable that the distance between the deepest portion of the recess 30c of the electrode plate 30 and the second main surface 30b is longer than 0.2 mm.

The recesses 30c of the electrode plate 30 shown in FIG. 2 are all recesses having the same depth, but the depth of the recesses 30c does not have to be constant and can be distributed. For example, the depth of the recess 30c may be increased at the center in the width direction (direction orthogonal to the X direction) of the electrode plate 30, or on both sides of the width direction (direction orthogonal to the X direction) of the electrode plate 30. The depth of the recess 30c may be increased. The electrode plate 30 may change the height of the convex portion instead of the depth of the concave portion. It is sufficient that at least the surface area of the first main surface 30a is larger than the surface area of the second main surface 30b.
The number of recesses 30c provided on the first main surface 30a is not limited.

In addition, the depth of the concave portion 30c or the height of the convex portion of the electrode plate 30 can be gradually changed along the X direction (longitudinal direction) in FIG. For example, when the plasma density of the upstream portion of the current is lower than that of the downstream portion, the difference in the surface area on the upstream side (the difference between the surface area on the first principal surface side and the surface area on the second principal surface side). And increase the surface area difference on the downstream side.
Further, the intervals between the plurality of recessed portions 30c need not be constant, and the intervals may be changed in the width direction (direction orthogonal to the X direction).

(First modification)
FIG. 3 is a perspective view of an electrode plate 60 different from the electrode plate 30.
The first main surface 60 a of the electrode plate 60 includes a recess similar to the recess 30 c provided on the first main surface 30 a of the electrode plate 30. On the other hand, the second main surface 60b is provided with a plurality of fin-like thin plate members 60c extending in a direction orthogonal to the X direction in which current flows. The reason why the thin plate member 60c is provided on the second main surface 60b side is to increase the resistance by largely changing the cross-sectional area in the direction of current flow on the second main surface 60b side. For this reason, it becomes easy to flow an electric current through the 1st main surface 60a whose resistance is small compared with the 2nd main surface 69b. Therefore, the current flowing through the first main surface 60a can be increased, and the magnetic field formed in the film formation space 40 can be increased by the current flowing through the first main surface 30a as compared with the conventional case.
The thin plate member 60c is also effective in that it dissipates heat generated by current flowing through the electrode plate 60. The second main surface 60b of the electrode plate 60 is not limited to being provided with the thin plate member 60c, but may be provided with unevenness extending along a direction orthogonal to the direction of current flow. The electrode plate 60 is preferably provided with at least irregularities that increase the resistance of the current flowing through the surface layer of the second main surface 60b.

(Second modification)
FIG. 4 is a diagram for explaining an example in which electrode plates 62 and 64 are provided in order to generate a large-area plasma.
The electrode plates 62 and 64 are fixed to the partition wall 32 shown in FIG. At this time, the electrode plates 62 and 64 are arranged in parallel in the direction in which the current flows. Similarly to the recess 30c of the electrode plate 30, the electrode plates 62 and 64 have recesses 62c ₁ and 62c ₂ and recesses 64c ₁ and 64c _{2 on} the first main surfaces 62a and 64a facing the film formation space 40. Are provided along the X direction. The recess 62c ₂ is a recess positioned at the end on the side where the electrode plates 62 and 64 are adjacent, and the recess 64c ₂ is a recess positioned at the end on the side where the electrode plates 62 and 64 are adjacent. The depths of the recesses 62c ₂ and 64c ₂ are deeper than the depths of the recesses 62c ₁ and 64c ₁ . As described above, the depth of the recess located on the side where the electrode plates 62 and 64 are adjacent is increased by increasing the surface area of the first main surfaces 62a and 64a on the side where the electrode plates 62 and 64 are adjacent. This is because the current is increased by increasing the surface area. When two electrode plates 30 shown in FIG. 2 are arranged in parallel, it is difficult for current to flow in a portion where the two electrode plates are adjacent to each other. For this reason, the magnetic field generated by the current in this portion does not increase, and as a result, the plasma density in the portion where the two electrode plates are adjacent is low. Therefore, uniform plasma is difficult to be generated.
However, by using the electrode plates 62 and 64 provided with the deep concave portions 62c ₂ and the concave portions 64c ₂ , it is possible to suppress a decrease in the current in the portion where the two electrode plates are adjacent to each other and to allow the current to flow uniformly. . As a result, a uniform magnetic field can be formed, and uniform and high-density plasma can be generated.

  As described above, in the electrode plate used for generating plasma, current flows from one end face to the other end face. The first main surface of the electrode plate faces the film formation space, and a plurality of recesses extending along the current direction are provided on the first main surface. For this reason, the electric current which flows into a 1st main surface can be increased, and the magnetic field in film-forming space can be made high compared with the past. Therefore, plasma can be generated with high density.

  The thin film forming apparatus of the present invention has been described in detail above. However, the thin film forming apparatus of the present invention is not limited to the above embodiment, and various improvements and modifications may be made without departing from the gist of the present invention. Of course.

DESCRIPTION OF SYMBOLS 10 Thin film forming apparatus 12 Power supply unit 14,104 Film formation container 16 Gas supply part 18 Gas exhaust part 20 Glass substrate 22 High frequency power supply 24 High frequency cable 26 Matching box 28, 29 Transmission line 30, 60, 62, 64, 102 Electrode plate 30a , 60a, 62a, 64a first main surface 30b, 60b second main surface _{30c, 62c 1, 62c 2,} 64c 1, 64c 2 grooves 32,106 septum 34 insulating member 36,108 dielectric 38 the inner space 40 formed Membrane space 42, 110 Heater 44, 112 Susceptor 46 Elevating mechanism 48 Gas tank 50 Mass flow controller 52 Turbo molecular pump 54 Dry pump 60c Thin plate member 100 Plasma film forming apparatus

Claims (5)

A thin film forming apparatus for forming a thin film on a substrate,
A film formation container having a film formation space for forming a thin film on a substrate in a reduced pressure state;
A raw material gas introduction section for introducing a raw material gas for a thin film into the film formation space of the film formation container;
A plasma electrode unit for generating plasma using the thin film source gas in the film formation space;
The plasma electrode portion is a plate member in which an electric current flows from one end surface to the other end surface, and is arranged so that a first main surface of the plate member faces the film formation space, and the first main surface A thin film forming apparatus comprising: an electrode plate provided with a plurality of groove-like recesses extending along a current direction as a plasma generating electrode. The second main surface has a flat shape along the current direction,
2. The thin film forming apparatus according to claim 1, wherein a surface area of a second main surface facing the first main surface of the electrode plate is smaller than a surface area of the first main surface.   2. The thin film forming apparatus according to claim 1, wherein the second main surface facing the first main surface includes unevenness extending along a direction orthogonal to the current direction. When the electrode plate is referred to as a first electrode plate,
The plasma electrode portion is a plate member in which an electric current flows from one end surface to the other end surface, and is arranged such that a third main surface of the plate member faces the film formation space, and the third main surface A second electrode plate provided with a plurality of groove-shaped recesses extending along the current direction, spaced apart from the first electrode plate,
The second electrode plate is arranged in parallel with the first electrode plate,
In each of the first electrode plate and the second electrode plate, the depth of the recess at the end on the side where the first electrode plate and the second electrode plate are adjacent to each other is the depth of the recess at another position. The thin film forming apparatus according to claim 1, wherein the thin film forming apparatus is deeper than a depth. The thin film forming apparatus according to any one of claims 1 to 4, wherein a distance between a deepest place of the concave portion of the electrode plate and the second main surface is longer than 0.2 mm.