JP2011181832A - Thin film forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a thin film in a short time by improving a generation concentration of plasma when forming the thin film on a substrate using the plasma. <P>SOLUTION: A thin film forming device which forms the thin film on the substrate includes a film forming container including a film forming space where the thin film is formed on the substrate in a pressure-reduced state, a material gas introduction portion which introduces a material gas for the thin film into the film forming space in the film forming container, and a plasma electrode portion which generates the plasma in the film forming space using the material gas for the thin film. The plasma electrode portion includes as an electrode for plasma generation a plate member where a current flows from one end surface to the other end surface, the plate member being arranged with a first main surface thereof directed to the film forming space and being provided with an uneven portion, which extends in a direction orthogonal to a current direction, on the second main surface opposed to the first main surface. <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. 6A is a diagram illustrating a simplified configuration of an example of a plasma film forming apparatus using a plate-like 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. 6B 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 The thin film forming apparatus is characterized in that an electrode plate provided with a concavo-convex portion extending along a direction orthogonal to the current direction is provided as a plasma generation electrode on the second main surface facing the surface.

  In that case, it is preferable that the said uneven | corrugated | grooved part is formed of the thin-plate member standingly arranged from the said 2nd main surface 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 concavo-convex portion extending along a direction orthogonal to the current direction is spaced apart from the first electrode plate as a plasma generation electrode. Prepare. At this time, the second electrode plate is disposed so as to be parallel to the first electrode plate, and the first electrode plate and the second electrode plate among the concavo-convex portions of the first electrode plate. It is preferable that the height of the convex portion at the end portion on the side where the electrode plate and the second electrode plate are adjacent to each other is higher than the height at other positions.

  In addition, among the concavo-convex portions of the first electrode plate and the second electrode plate, the height of the convex portion is on the side adjacent to the first electrode plate and the second electrode plate. It is preferable that it becomes low as it leaves | separates from an edge part.

  The uneven portion is preferably provided on the entire second main surface.

  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 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 explaining the magnitude of the electric current which flows through an electrode plate. (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 high frequency power of several tens of MHz to the electrode plate 30 at 100 to 1000 W, for example. 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-like transmission line having a certain width, and can pass a current of 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 that is long in one direction fixed on a partition wall 32 to be described later, and the first main surface of the plate member is arranged in parallel toward the film formation space in the film formation container 14. ing. 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 concavo-convex portions extending along a direction orthogonal to the direction of current flow on the second main surface facing 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 forming container 14 is a case that is made of a material such as aluminum and 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 for electrically insulating the surrounding partition wall 32 is provided around the electrode plate 30. 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 forming space 40, and the turbo molecular pump 52 maintains the pressure in the film forming space 40 at a reduced pressure of 1 × 10 ⁻⁴ Pa or less with high accuracy. 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 the flat surface of the plate member. On the other hand, the second main surface 30b facing the first main surface 30a is formed by a thin plate member 30c erected from the second main surface 30b along a direction orthogonal to the current direction (X direction in the figure). Concave and convex portions are formed to form a fin shape. The thin plate member 30c extends from end to end in a direction orthogonal to the direction of current flow in the electrode plate 30 (X direction in the figure). Further, the thin plate member 30c is erected at a constant interval from end to end along the direction of current flow of the electrode plate 30. The thickness of the thin plate member 30c is, for example, 1 to 10 mm.
For the electrode plate 30 and the thin plate member 30c, for example, copper, aluminum or the like is used.

The reason why the plurality of thin plate members 30c are erected on the second main surface 20b is to increase the current flowing in the surface layer of the first main surface 30a.
Specifically, 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 cross-sectional area of the second main surface 30b varies greatly along the direction of current flow due to the thin plate member 30c, the resistance (impedance) flowing through the surface layer of the second main surface 30b is the first This is larger than the resistance received by the current flowing through the surface layer of the main surface 30a. For this reason, the electric current which flows through the surface layer of the 1st main surface 30a is large compared with the case where the thin plate member 30c is not provided in the 2nd main surface 30b. For this reason, the magnetic field formed in the film formation space 40 due to the large current flowing through the surface layer of the first main surface 30a is larger than that of the electrode plate (see FIG. 6B) where the thin plate member 30c is not provided. growing. 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 a material, and the current frequency is In the case of several tens of MHz, the depth of the surface layer is about 0.1 mm. Therefore, the thickness of the electrode plate 20 (excluding the thin plate member 30c) is preferably greater 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.

  The thin plate members 30c of the electrode plate 30 shown in FIG. 2 are all the same height, but the height of the thin plate portion 30c does not have to be constant, and may be distributed in one thin plate member 30c. it can. For example, the height may be increased at the center in the width direction (direction orthogonal to the X direction) of the electrode plate 30, or the height of the thin plate member 30 c may be increased on both sides in the width direction of the electrode plate 30. Good. Further, the height of the thin plate member 30c can be distributed according to each position along the X direction. The electrode plate 30 may change the depth of the recess instead of the height of the thin plate member 30c. It suffices that at least the cross-sectional area in the direction in which the current flows changes according to the position along the X direction of the second main surface 30b. The number of thin plate members 30c provided on the second main surface 30b is not limited.

  The thin plate member 30c is also effective in dissipating heat generated by the current flowing through the electrode plate 30. The second main surface 30b of the electrode plate 30 is not limited to being provided with the fin-shaped thin plate member 30c, but may be provided with unevenness extending along a direction perpendicular to the direction of current flow. The electrode plate 30 may be provided with at least irregularities that increase the resistance of the current flowing through the surface layer of the second main surface 30b.

(First modification)
FIG. 3 is a perspective view of an electrode plate 60 different from the electrode plate 30.
On the first main surface 60a of the electrode plate 60 facing the film formation space 40, a plurality of groove-shaped recesses 60d extending along the direction of current flow (X direction in the figure) are provided. The second main surface 60b is provided with a thin plate member 60c similar to the thin plate member 30c shown in FIG. Since the thin plate member 60c is provided on the second main surface 60b, it is difficult for current to flow through the surface layer of the second main surface 60b. For this reason, a large current flows through the surface layer of the first main surface 60a.

  In the example illustrated in FIG. 3, a groove extending in the X direction in which a concave portion is formed on a linearly inclined surface is provided as the concave portion 60 d provided on the first main surface 60 a. For this reason, as for the electrode plate 60, the surface area of the 1st main surface 30a is large compared with the case where there is no groove | channel. The high-frequency current flowing through the electrode plate 60 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 60a has a larger surface area than when there is no groove, the current flowing through the surface layer of the first main surface 60a is larger than when there is no groove. For this reason, the current flowing through the surface layer of the first main surface 60a is further increased together with the fact that current does not easily flow through the surface layer of the second main surface 60b. Thereby, the magnetic field formed in the film forming space 40 becomes larger than that of the electrode plate (see FIG. 5B) not provided with the recess 60d. 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 60, a uniform magnetic field is generated over a wide range, and as a result, high-density plasma can be generated over a wide range.

(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 thin plate member 30c of the electrode plate 30, the electrode plates 62 and 64 are thin plate members on the second main surfaces 62b and 64b facing the first main surfaces 62a and 64a facing the film formation space 40. 62c and 64c are erected from the second main surfaces 62b and 64b at regular intervals to form a fin shape.
Further, the height of the thin plate members 62c and 64c of the electrode plate 62 and the electrode plate 64 varies in the direction orthogonal to the X direction. Specifically, the height of the thin plate members 62c and 64c at the end portion on the side where the electrode plate 62 and the electrode plate 64 are adjacent to each other is higher than the height at other positions. More specifically, the height gradually decreases as the electrode plate 62 and the electrode plate 64 move away from the positions of the end portions of the adjacent thin plate members 62c and 64c.

As described above, the height of the thin plate members 62c and 64c is highest at the end on the side where the electrode plate 62 and the electrode plate 64 are adjacent to each other, and gradually decreases as the distance from the position increases. This is because a uniform current flows through the surface layers of the first main surfaces 62a and 64a of 62 and 64.
As shown in FIG. 5, when two electrode plates 30 are arranged in parallel, current may not easily flow at the end portion on the side where the two electrode plates 30 are adjacent to each other. For this reason, the magnetic field produced | generated by the electric current of this part is low, As a result, the plasma density in the part which two electrode plates adjoin may fall. Therefore, in some cases, uniform plasma is not generated.
However, like the thin plate members 62c and 64c, the first main surfaces 62a and 64a are made higher by setting the height of the end portions of the thin plate members 62c and 64c on the side where the electrode plates 62 and 64 are adjacent to each other. The current can easily flow at the end of the electrode plate 62 and the electrode plate 64 adjacent to each other. Thereby, a uniform magnetic field can be formed using the electrode plates 62 and 64, 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. A first main surface of the electrode plate faces the film formation space, and a plurality of concave and convex portions extending along a direction perpendicular to the direction of current flow are provided on the second main surface facing the first main surface. ing. For this reason, the thin film forming apparatus can increase the current flowing through the first main surface, and can increase the magnetic field in the deposition space as compared with the conventional case. As a result, the thin film forming apparatus can generate plasma 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, 62b, 64b Second main surface 30c, 60c, 62c, 64c Thin plate member 60d Groove portion 32, 106 Partition wall 34 Insulating member 36, 108 Dielectric 38 Internal space 40 Deposition space 42, 110 Heater 44, 112 Susceptor 46 Elevating mechanism 48 Gas tank 50 Mass flow controller 52 Turbo molecular pump 54 Dry pump 100 Plasma film formation 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 concavo-convex portion extending along a direction orthogonal to the current direction on a second main surface facing the electrode as a plasma generating electrode.   2. The thin film forming apparatus according to claim 1, wherein the concavo-convex portion is formed by a thin plate member standing from the second main surface 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 concavo-convex portion extending along a direction orthogonal to the current direction is spaced apart from the first electrode plate as a plasma generation electrode. Prepared,
The second electrode plate is arranged in parallel with the first electrode plate,
Of the concavo-convex portions of the first electrode plate and the second electrode plate, the height of the convex portion at the end on the side where the first electrode plate and the second electrode plate are adjacent to each other is The thin film forming apparatus according to claim 1, wherein the thin film forming apparatus is higher than a height at other positions.   Of the concavo-convex portions of the first electrode plate and the second electrode plate, the height of the convex portion is an end portion on the adjacent side of the first electrode plate and the second electrode plate. The thin film formation apparatus of Claim 3 which becomes low as it leaves | separates from. The thin film forming apparatus according to claim 1, wherein the uneven portion is provided on the entire second main surface.