JP4594770B2 - Plasma CVD equipment - Google Patents

Description

  The present invention relates to a plasma CVD apparatus, and more particularly to a plasma CVD apparatus suitable for forming a thin film on a large-area substrate.

  A technique for forming a thin film on the surface of a substrate using a CVD (chemical vapor deposition) apparatus using plasma is known. For example, in the manufacture of a thin film transistor, a plasma CVD apparatus that uniformly forms a thin film (gate insulating film) such as amorphous silicon or crystalline silicon on a substrate is used. In this plasma CVD apparatus, plasma is generated in a decompressed container, and radicals generated by decomposing a source gas in the plasma are deposited on a substrate surface to form a film.

  Conventionally used plasma CVD apparatuses include a capacitive coupling method and an inductive coupling method as excitation methods. The capacitive coupling method is configured, for example, by arranging a plate-like high-frequency electrode and a ground electrode in parallel, and a substrate on the ground electrode side.

  However, according to this configuration, for example, if the frequency of the high frequency is increased in order to improve the film forming speed and film characteristics, the spatial density of the plasma formed between the electrodes becomes non-uniform, and the film quality deteriorates. There is. Further, when a large-area substrate is formed, the electrode area becomes large, so that it is difficult to keep the gap between the electrodes at a uniform distance.

  On the other hand, as an inductive coupling method, for example, a configuration is disclosed in which a U-shaped conductive electrode is arranged in a plane so as to face a substrate, and a central point where the electrode is bent is a high-frequency feeding point ( For example, see Patent Document 1). According to this configuration, it is possible to generate plasma suitable for film formation of a large area by bending a plurality of electrodes and extending them in a planar shape to generate a standing wave.

  However, in such an electrode structure, when the electrode is directly exposed to the conductive plasma, stable electromagnetic waves are not emitted from the electrode, and the discharge becomes non-uniform and the film thickness may not be formed uniformly. .

  Therefore, a plurality of linear antenna elements made of a conductor are alternately arranged opposite to each other in the direction opposite to the feeding direction in parallel and at a predetermined interval, and the surface of each antenna element is covered with a dielectric. A known plasma CVD apparatus is known (see, for example, Patent Document 2).

  According to this configuration, it is possible to supply power to each antenna element independently, and to use a high frequency region (for example, 100 MHz) in which plasma uniformity is difficult in the capacitive coupling method and the inductive coupling method. it can. By using such a high frequency, the plasma potential is lowered, and for example, damage to the substrate by ions can be reduced as compared with the capacitive coupling method. In addition, electromagnetic energy can be efficiently released from each antenna element into the surrounding gas, so that a spatially uniform plasma can be formed. By increasing the length and number of antenna elements, Applicable to film formation.

JP 2000-345351 A JP 2003-86581 A

  By the way, in the structure of patent document 2, since the amplitude of the standing wave of each adjacent antenna element becomes a mutually reverse relationship, the electromagnetic waves radiated | emitted from each antenna element are synthesize | combined and compared widely in a plane direction. Uniform plasma is formed.

  That is, the electromagnetic wave energy radiated from each antenna element changes in proportion to the square of the amplitude of the standing wave along the axial direction of the antenna element, but the high-frequency feed ends of adjacent antenna elements are different. Therefore, the electromagnetic wave energy in the axial direction overlaps and complements each other, and the electromagnetic wave energy distribution in the antenna axial direction can be made relatively uniform.

  However, according to Patent Document 2, since the electromagnetic energy of a sinusoidal standing wave (for example, a quarter wavelength) is synthesized, the spatial density of the plasma formed by the antenna element is in the axial direction of the antenna element. In particular, the spatial density of the plasma tends to be high near the center in the axial direction.

  For this reason, although the film thickness on the substrate depends on other parameters such as the concentration distribution of the source gas, for example, there is a possibility that sufficient uniformity cannot be maintained due to the influence of the spatial density distribution of the plasma.

  An object of the present invention is to suppress non-uniformity in plasma spatial density in the axial direction of an antenna element.

  In order to solve the above problems, the present invention provides a vacuum vessel into which a source gas is introduced, a holder provided in the vacuum vessel to which a flat plate member to be deposited is fixed, and a flat plate surface of the flat plate member. The antenna has a base end that supplies a plurality of antenna elements made of a rod-shaped conductor whose surface is covered with a dielectric, and supplies high-frequency power to one end of each adjacent antenna element at intervals. In the plasma CVD apparatus in which the portions are alternately arranged on different sides, each antenna element is arranged so that the distance from the flat plate surface increases or decreases toward the tip side.

  Thus, for example, by arranging the antenna elements at a predetermined angle with respect to the flat plate surface, the electromagnetic wave energy near the center in the axial direction of the antenna elements caused by the overlap of electromagnetic wave energy radiated from each antenna element is obtained. The intensity can be reduced, and the nonuniformity of the plasma spatial density can be suppressed.

  Moreover, you may make it provide the support part which supports the angle with respect to the flat surface of the flat plate member of each antenna element variably at the base end part of each antenna element. According to this, the angle of the antenna element can be appropriately adjusted according to, for example, the apparatus configuration, external parameters, or the film formation result on the flat plate surface. Thereby, the non-uniform distribution of electromagnetic energy in the axial direction of the antenna element can be suppressed, the spatial density distribution of plasma can be reduced, and the film thickness can be stabilized.

  In this case, the antenna element has the length of the antenna element extending from the base end portion as (2n + 1) / 4 times the wavelength of the high-frequency power supplied to one end of the antenna element (n is zero or a positive integer). It is preferable to do. Thus, by setting the high frequency power so that a high frequency standing wave is generated in each antenna element, unnecessary reflection of electromagnetic waves can be reduced in each antenna element, and the plasma excitation efficiency can be increased.

  According to the present invention, it is possible to suppress the nonuniformity of the plasma spatial density in the axial direction of the antenna element.

  Hereinafter, embodiments of the plasma CVD apparatus according to the present invention will be described with reference to the drawings, but the present invention is not limited thereto.

  FIG. 1 is a plan view showing an example of a plasma CVD apparatus according to an embodiment of the present invention. FIG. 2 is a sectional side view of FIG.

  As shown in the figure, the plasma CVD apparatus of this embodiment has a configuration in which a plurality of linear antenna elements, that is, rod-shaped electrodes 3 (also referred to as electromagnetic coupling electrodes) are arranged in a chamber 1. Below the electrode 3, there is a substrate holder 7 on which a substrate 5 to be deposited is placed. For example, a heating element (not shown) for heating the substrate 5 is provided. The substrate holder 7 is electrically grounded together with the chamber 1.

  A gas supply port 9 for introducing a source gas is provided on the upper side wall of the chamber 1, and a gas exhaust port 11 for exhausting the source gas is provided below the opposite side wall. In this embodiment, TEOS (tetraethoxysilane) and oxygen are used as source gases, but can be set as appropriate according to the purpose of film formation. The gas exhaust port 11 is connected to a vacuum pump (not shown), and has a function of exhausting the chamber 1 and adjusting it to a set pressure.

  A plurality of electrodes 3 are arranged so that the feeding directions are alternately different, and a base end portion serving as a feeding portion of each electrode 3 is, for example, a transmission line 13 such as a coaxial cable, and a high-frequency power source 15 via a matching unit (not shown). It is connected to the. The high-frequency power output from the high-frequency power supply 15 is distributed and supplied to the power feeding portion of each electrode 3. The high frequency power supplied to each electrode 3 is set to 30 to 300 MHz, for example.

  A support portion 17 that supports the electrode is provided at the base end portion of each electrode 3, and a power transmission line 13 that is electrically insulated from the side wall of the chamber 1 and connected to the support portion 17 is connected to the support portion 17. Yes. The support portion 17 is provided with an angle adjustment mechanism that enables adjustment of the angle of the electrode 3 with respect to the flat surface of the substrate 5 in the chamber 1. Further, although not shown, the support portion 17 can freely adjust the angle of the electrode 3 from the outside of the chamber 1. The support portion 17 is disposed at the same height position from the flat plate surface of the substrate 5 and is directed upward with respect to the flat plate surface so that the height (distance) with respect to the flat plate surface of the substrate 5 increases toward the distal end side of the electrode 3. It is set at a predetermined angle.

  The electrode 3 is formed in a rod shape or a pipe shape by a nonmagnetic good electrical conductor such as copper, aluminum or platinum, and its surface is formed by covering with a dielectric such as quartz. The length from the tip of the electrode 3 to the support portion 17 is (2n + 1) / 4 times (n is 0 or a positive integer) with respect to the wavelength λ of the high-frequency power supplied to the electrode 3, and at least the width of the substrate 5 It is set longer than the dimension. And when the angle of the electrode 3 is made horizontal, the tip of one electrode 3 is arranged side by side in parallel so that the tip of the electrode 3 reaches a position near the front of the support portion 17 of the adjacent electrode 3. In addition, the electrode 3 constitutes a pair of electrode units with the adjacent electrode 3 in which the support portion 17 is arranged in the opposite direction, and a plurality of these are arranged in parallel.

  Next, the operation of forming a thin film on the surface of the substrate 5 using the plasma CVD apparatus of this embodiment will be described. First, after the chamber 1 is opened and the substrate 5 is placed on the substrate holder 7, a vacuum pump connected to the gas exhaust port 11 is operated to depressurize the chamber 1 to a vacuum of about 1 mmTorr to 1 Torr, for example. . Here, the substrate 5 is heated to a predetermined temperature by a heating element on the substrate holder 7.

  Next, a mixed gas of TEOS and oxygen is supplied into the chamber 1 from the gas supply port 9 as a source gas. In this state, after the pressure in the chamber 1 is stabilized, high-frequency power is supplied to each electrode 3 to emit high-frequency electromagnetic waves from the electrodes 3, whereby the mixed gas is ionized, and the substrate 5 and the electrode 3 are separated. In the meantime, plasma 19 is generated. The plasma 19 has conductivity. When the plasma is filled in the chamber 1 and the overall conductivity is increased, the emitted electromagnetic wave is reflected by the plasma 19 and is confined around the electrode 3. However, the plasma heating region is limited. Note that the plasma 19 shown in FIG. 2 schematically represents the generation region.

  In this embodiment, the electrode 3 is lifted and arranged at a predetermined angle with respect to the flat surface of the substrate 5 so that the horizontal energy distribution caused by the overlap of electromagnetic wave energy emitted from each electrode 3 is relaxed. ing. Thereby, for example, the spatial density of electromagnetic wave energy that increases in the vicinity of the center in the horizontal direction can be reduced, and unevenness of the spatial density of plasma in the axial direction can be suppressed.

  Further, in the present embodiment, the installation angle of the electrode 3 with respect to the flat surface of the substrate 5 can be freely adjusted by an external operation via the support portion 17. The installation angle can be appropriately adjusted according to the above.

  In the present embodiment, the electrode 3 is lifted from both sides with a predetermined angle with respect to the flat surface of the substrate 5 so that the central portion of the facing electrode 3 is raised in a mountain shape. For example, the central portion may be arranged in a valley shape, that is, the electrode 3 may be arranged so as to be inclined downward at a predetermined angle with respect to the flat surface of the substrate 5.

  Further, in the present embodiment, the adjustment range of the electrode 3 is limited to the angle with respect to the flat surface of the substrate 5, but for example, it may be configured such that the horizontal angle can be adjusted as necessary.

  Further, in the present embodiment, the electrode 3 is limited to a straight rod-shaped electrode, but is not limited to this electrode shape. For example, the electrode 3 is bent in an R shape or a predetermined angle. May be.

  As described above, according to the present embodiment, it is possible to form spatially uniform plasma in the direction of the horizontal plane parallel to the substrate surface, so that the film thickness of the large area substrate can be stabilized. Therefore, the plasma CVD apparatus of this embodiment can be applied to, for example, the manufacture of thin film solar cells that can be used for supplying electrodes, the manufacture of liquid crystal thin films, the manufacture of thin film transistors, the etching of semiconductors, and other industrial uses. .

  Further, instead of the arrangement of the electrodes 3 in the above embodiment, for example, a plurality of the electrodes 3 are vertically suspended at a predetermined interval so that the feeding direction is from the upper side of the chamber 1 to the lower side, that is, the substrate side. May be. According to this, since it is not influenced by the intensity distribution of the electromagnetic wave energy in the axial direction of the electrode 3, it is possible to form a uniform plasma in the horizontal direction and to stabilize the film thickness of the large area substrate. it can.

It is a top view which shows an example of the plasma CVD apparatus of embodiment of this invention. It is a sectional side view of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Chamber 3 Electrode 5 Substrate 7 Substrate holder 9 Gas supply port 11 Gas exhaust port 13 Transmission line 15 High frequency power supply 17 Support part

Claims (3)

A vacuum vessel into which a source gas is introduced; a holder provided in the vacuum vessel to which a flat plate member to be formed is fixed; and an antenna arranged to face the flat plate surface of the flat plate member, A plurality of antenna elements composed of rod-shaped conductors whose surfaces are covered with a dielectric, and base ends that supply high-frequency power to one end of each of the adjacent antenna elements are alternately arranged on different sides. In an arrayed plasma CVD apparatus,
The plasma CVD apparatus, wherein the antenna element is disposed so that a distance from the flat plate surface increases or decreases toward a tip side of the antenna element. A vacuum vessel into which a source gas is introduced; a holder provided in the vacuum vessel to which a flat plate member to be formed is fixed; and an antenna arranged to face the flat plate surface of the flat plate member, A plurality of antenna elements composed of rod-shaped conductors whose surfaces are covered with a dielectric, and base ends that supply high-frequency power to one end of each of the adjacent antenna elements are alternately arranged on different sides. In an arrayed plasma CVD apparatus,
A plasma CVD apparatus, wherein a support portion for variably supporting an angle of each antenna element with respect to a flat plate surface of the flat plate member is provided at the base end portion of each antenna element. In the antenna element, the length of the antenna element extending from the base end is (2n + 1) / 4 times the wavelength of the high-frequency power supplied to one end of the antenna element (n is zero or a positive integer). The plasma CVD apparatus according to claim 1, wherein:

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