KR101447162B1 - Plasma processing apparatus for film deposition and deposition method of micro crystalline silicon layer using the same - Google Patents

Abstract

The present invention discloses a plasma processing apparatus and a method of depositing a microcrystalline silicon thin film using the plasma processing apparatus. A plasma processing apparatus of the present invention includes: a chamber having a reaction space; A substrate table installed inside the chamber; A gas injection means installed on the substrate bench; A gas ring provided on an upper portion of the periphery of the substrate bench and having a plurality of ejection holes for ejecting gas onto the substrate bench; And power supply means for supplying power to the gas injection means and the gas ring.

According to the present invention, since a high density plasma can be generated due to the inductively coupled electric field formed in the horizontal direction between the main electrode and the negative electrode, the deposition rate of the thin film can be greatly improved. In addition, since the negative electrode positioned above the periphery of the substrate rest room can compensate for the plasma density at the substrate stand periphery, it is possible to improve the uniformity of the thin film of the large substrate. Therefore, the deposition rate and thin film uniformity of the microcrystalline silicon (c-Si: H) layer having a low deposition rate can be greatly improved, and the productivity of the large-area thin film solar cell can be greatly improved.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing apparatus for depositing a thin film and a method for depositing a microcrystalline silicon thin film using the same,

The present invention relates to a plasma processing apparatus for thin film deposition, and more particularly, to a plasma processing apparatus capable of increasing the deposition rate of microcrystalline silicon and a thin film deposition method using the plasma processing apparatus.

In response to the exhaustion of fossil resources and environmental pollution, interest in clean energy such as the solar power has increased, and research on solar cells that generate electromotive force using solar light has gained vitality.

The solar cell utilizes the electromotive force generated by the diffusion of the minority carriers excited by the sunlight in the pn junction semiconductor. Examples of the semiconductor material used include monocrystalline silicon, polycrystalline silicon, amorphous silicon, and compound semiconductor.

Thin film solar cells that deposit amorphous silicon or compound semiconductors on inexpensive substrates such as glass and plastic have attracted attention recently because the use of monocrystalline silicon or polycrystalline silicon results in high power generation efficiency, but inexpensive materials and complicated processes. In particular, the thin film solar cell is advantageous in that it can be manufactured in a flexible manner according to the material of the substrate, as well as being very advantageous for large-scale production.

A thin film solar cell using amorphous silicon has a structure in which a first electrode 12, a semiconductor layer 13 of amorphous silicon (a-Si: H), and a second electrode 12 are formed on the transparent substrate 11, Two electrodes 14 are sequentially formed.

The transparent substrate 11 is made of glass or a transparent plastic material.

The first electrode 12 is formed of a transparent conductive oxide (TCO) thin film for transmitting sunlight incident on the transparent substrate 11 side.

The semiconductor layer 13 is formed by sequentially stacking the P-type semiconductor layer 13a from the first electrode 12 side, the intrinsic semiconductor layer 13b for increasing the light absorption rate, and the N-type semiconductor layer 13c sequentially, Thereby forming a bonding surface.

The second electrode 14 may be formed by depositing a TCO thin film or by depositing a metal thin film such as Al, Cu, or Ag, in the same manner as the first electrode 12.

When solar light is irradiated from the transparent substrate 11 side in the thin film solar cell having such a structure, the minority carriers generated in the semiconductor layer 13 are diffused across the PIN junction surface, and the first electrode 12 and the second electrode 14 ) To generate an electromotive force.

However, the thin film solar cell using amorphous silicon has a very low energy conversion efficiency compared with a solar cell using a single crystal or polycrystalline silicon or a solar cell using a compound semiconductor, and when exposed to light for a long time, a characteristic degradation phenomenon (Staebler-Wronski effect) There is a problem that the efficiency is lowered more and more.

To solve this problem, a microcrystalline silicon thin film solar cell using microcrystalline silicon (μc-Si: H or nc-SiH) instead of amorphous silicon is used. Microcrystalline silicon is a boundary material between amorphous and monocrystalline silicon and has a crystal size of several tens to several hundreds of nm depending on the deposition method, and has the advantage that there is no characteristic deterioration phenomenon such as amorphous silicon.

Microcrystalline silicon is also used with amorphous silicon to increase the light absorption rate because it has a different energy band gap than amorphous silicon. That is, a thin film solar cell having a tandem structure or a triple structure in which a PIN layer of an amorphous silicon (P-type intrinsic N-type semiconductor layer) and a PIN layer of microcrystalline silicon are continuously laminated is widely used.

However, in this solar cell, the amorphous silicon layer can be deposited to a thickness of about 400 nm, but in order to increase the light absorptance of the long wavelength band of microcrystalline silicon, the thickness should be about 1 to 5 μm. It is becoming a limiting factor.

On the other hand, it is very important to deposit a uniform thin film on a large-area substrate because the thin film solar cell has the advantage of using a low-cost large-area substrate to reduce the production cost.

However, in a conventional PECVD apparatus for forming an amorphous or microcrystalline silicon layer, a thin film is deposited on the substrate by generating plasma between the electrodes facing each other and the substrate stand, so that the thickness of the thin film tends to vary in the peripheral portion and the central portion of the substrate.

Such a problem is a problem to be solved even when a flat panel display device is manufactured using a large area substrate as well as a solar cell.

It is an object of the present invention to provide a plasma processing apparatus capable of improving a deposition rate of a thin film on a substrate.

Another object of the present invention is to provide a plasma processing apparatus capable of forming a uniform thin film over the entire surface of a large area substrate.

In order to achieve the above object, the present invention provides a reaction chamber comprising: a chamber having a reaction space; A substrate table installed inside the chamber; A gas injection means installed on the substrate bench; A gas ring provided on an upper portion of the periphery of the substrate bench and having a plurality of ejection holes for ejecting gas onto the substrate bench; And a power supply means for supplying power to the gas injection means and the gas ring.

In the plasma processing apparatus, a voltage regulating means is provided between the power supply means, the gas injecting means, and the gas ring, and the voltage regulating means is a transformer.

Further, the power supply means is connected to the primary side of the transformer, the gas injection means is connected to the first terminal of the secondary side of the transformer, and the gas ring is connected to the second terminal having the opposite polarity to the first terminal . ≪ / RTI >

Wherein the power supply means includes a first high frequency power supply and a second high frequency power supply having different frequencies, and the high frequency power of the first high frequency power supply and the second high frequency power supply is supplied to the gas supply means and the gas ring via the transformer And is applied at the same time. In this case, a first matching circuit and a second matching circuit are respectively provided between the first high frequency power source and the second high frequency power source and the transformer, and the first matching circuit and the second matching circuit are affected by other high frequency power sources The filter may include a filter.

In the plasma processing apparatus, the power supply means may include a first high frequency power source connected to the gas injection means, and a second high frequency power source connected to the gas ring.

Further, the gas injection means and the gas supply pipe connected to the gas ring may be provided with independent flow rate adjusting devices.

The gas injection means may include a flat plate electrode that hermetically closes the upper portion of the chamber and is connected to the power supply terminal; And a gas distribution plate coupled to a lower portion of the flat plate electrode and electrically connected to the flat plate electrode.

And the gas injection means and the gas ring are installed so as to be insulated from the chamber.

The gas ring may include a plurality of gas rings separated from each other, and power of the power supply unit may be supplied to each of the gas rings.

The gas ring may be made of Cu, stainless steel (SUS) or anodized aluminum.

The substrate holder may be grounded at two or more points. The internal pressure of the chamber may be 50 mTorr or more and 10 Torr or less.

The present invention also provides a process for producing a polymer electrolyte membrane, comprising: a chamber having a reaction space; A substrate table installed inside the chamber; A gas injection means installed on the substrate bench; A gas ring provided on an upper portion of the periphery of the substrate bench and having a plurality of ejection holes for ejecting gas onto the substrate bench; And a power supply means for supplying power to the gas injection means and the gas ring, the method comprising the steps of: bringing a substrate into the chamber; An enfolding step; Applying power of the high frequency power source to the gas injection means and the gas ring; While by supplying SiH ₄ and H ₂ through the gas injection means or the gas ring holding the chamber at a pressure range of 50mTorr to 10Torr, wherein by an electric field formed between the gas injection means and the gas ring SiH _4, and Generating a plasma comprising active species and ions of H ₂ ; Forming a microcrystalline silicon (μc-Si: H) thin film on the substrate by injecting the active species and ions into the substrate.

According to the present invention, since a high-density plasma can be generated due to the inductively coupled electric field formed in the horizontal direction between the main electrode and the sub-electrode of the plasma processing apparatus, the deposition rate of the thin film can be greatly improved.

In addition, since the negative electrode located on the upper part of the periphery of the substrate rest room serves to compensate the plasma density around the substrate rest area, the uniformity of the thin film of the large area substrate can be improved. Also, due to these advantages, the deposition rate and thin film uniformity of the microcrystalline silicon (μc-Si: H) layer, which has a low deposition rate, can be greatly improved, thereby greatly improving the productivity of the large-area thin film solar cell.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

First Embodiment

2 is a cross-sectional view schematically showing a configuration of a plasma processing apparatus 100 according to a first embodiment of the present invention.

The plasma processing apparatus 100 includes a chamber 110 forming a reaction space, a substrate table 120 installed inside the chamber 110 to house the substrate s, A gas distribution plate 140 disposed at a lower portion of the main electrode 130 and spaced apart from the main electrode 130 and having a plurality of injection holes, And a gas supply pipe 150 passing through the main electrode 130 and supplying the raw material to the upper portion of the gas distribution plate 140.

Particularly, in the plasma processing apparatus 100 according to the embodiment of the present invention, the auxiliary electrode 170 is provided on the upper part of the peripheral portion of the substrate mounting table 120 separately from the main electrode 130, And the negative electrode 170 is connected to one high frequency power source 160.

The present invention is characterized in that the high frequency power source 160 is not directly applied to the main electrode 130 and the negative electrode 170 but is applied with the secondary power via the transformer 164.

For this purpose, the negative electrode 170 is separated from the chamber 110 through an insulating material 180 such as ceramic or Teflon, thereby floating the negative electrode 170.

Concretely, the matching circuit 162 and the transformer 164 are connected in order to the output terminal of the high frequency power source 160, and the first terminal of the secondary side of the transformer 164 is connected to the first feeder line 166 And the second terminal having the opposite polarity to the first terminal is connected to the auxiliary electrode 170 using the second feeder line 168. [

The height at which the auxiliary electrode 170 is provided is preferably between the upper surface of the substrate platform 120 and the lower surface of the gas distribution plate 140.

When the main electrode 130 and the negative electrode 170 are connected to the high frequency power source 160 in this way, a horizontal electric field is formed between the main electrode 130 and the negative electrode 170, The inductively coupled field is formed with respect to the substrate s, so that a much higher density plasma can be generated than in the prior art in which a vertical electric field is formed on the substrate s.

Such a high density plasma can significantly improve the deposition rate of the microcrystalline silicon thin film.

The negative electrode 170 is formed along the periphery of the upper portion of the substrate table 120, and thus has a ring shape. Particularly, in the embodiment of the present invention, a gas ring having a plurality of injection holes 172 for gas injection is used as the negative electrode 170.

In order to generate a uniform plasma in the chamber 110, the sub-electrodes 170 are symmetrically disposed along the peripheral portion of the substrate pedestal 120, and a specific installation pattern can be variously determined.

That is, as shown in FIG. 3A, the auxiliary electrode 170 integrally connected along the periphery of the upper portion of the substrate table 120 may be provided. In this case, it is preferable that the second feeder line 168 is branched midway and symmetrically connected to at least two or more of the sub-electrodes 170.

In addition, as shown in FIG. 3B, a plurality of linear electrodes 170 separated from each other may be provided along the inner wall of the chamber 110. In this case, the second feeder line 168 is branched so that the RF power supply 160 is applied to each of the sub-electrodes 170.

As shown in FIG. 3C, not only the linear shape but also the perpendicularly bent negative electrode 170 may be disposed at the corner of the linear negative electrode 170. Even in this case, the second feeder line 168 must be branched and connected to each of the sub-electrodes 170.

The auxiliary electrode 170 is made of a material such as Cu, stainless steel (SUS), anodized aluminum, or the like.

The raw material may be injected into the chamber 110 through the gas distribution plate 140 under the main electrode 130 or may be supplied through the auxiliary electrode 170.

Since the inside of the negative electrode 170 is empty, the raw material is supplied to the inside of the negative electrode 170, and the raw material is injected through the injection hole 172 formed toward the center of the chamber 110.

The injection hole 172 of the auxiliary electrode 170 may be formed in a horizontal direction, but may be formed in a slightly upward or slightly downward direction as shown in FIGS. 4A and 4B depending on process conditions.

The cross-sectional shape of the negative electrode 170 may be a quadrangular shape as shown, or may be a polygonal or circular shape of another shape.

Generally, a standing wave of high frequency power is generated on the lower surface of the main electrode 130, more precisely on the lower surface of the gas distribution plate 140 electrically connected to the main electrode 130. Such a standing wave has a large amplitude at the center of the gas distribution plate 140, which causes the plasma density at the edge of the substrate to be lowered.

Therefore, if the negative electrode 170 is provided on the peripheral portion of the substrate table 120 as in the present invention, the plasma density can be compensated at the edge of the substrate (s), and the uniformity of the thin film can be improved as a whole.

The RF power source 160 may have a frequency in an RF band (e.g., 13.56 MHz) or a VHF band (e.g., 30 MHz to 300 MHz), and the applied power may vary depending on the size of the chamber 110.

In particular, when a high-frequency power source 160 of a VHF band of 30 to 300 MHz is applied, the density of plasma (or electrons) having an electron temperature of 2 eV or less is improved and a large amount of active species of SiH ₄ or SiH x is produced, (D / R) is increased.

The substrate holder 120 is grounded to return a high frequency electric field formed between the main electrode 130 and the sub electrode 170. The capacitively coupled field formed thereby forms the main electrode Ions and electrons contained in the plasma generated by the electric field between the electrodes 130 and 130 are uniformly distributed to the upper portion of the substrate s to obtain a uniform thin film.

In order to improve the uniformity of the thin film, it is preferable to form one or more multiple grounds on the substrate table 120.

Meanwhile, a flow rate regulating device is provided in a gas supply pipe (not shown) for supplying a raw material into the gas supply pipe 150 or the sub electrode 170 passing through the main electrode 130, You may.

In this way, the uniformity of the thin film can be actively controlled by adjusting the supply amount of the raw material through the gas distribution plate 140 and the negative electrode 170 according to process conditions.

Hereinafter, a process of depositing microcrystalline silicon on the substrate (s) in the plasma processing apparatus 100 having the above-described structure will be described.

First, the substrate (s) is placed on the upper part of the substrate table 120, and a process atmosphere is formed through vacuum pumping.

Subsequently, when the RF power supply 160 is applied, the gas distribution plate 140 (not shown) electrically connected to the main electrode 130 and the sub-electrode 170 connected to the secondary side of the transformer 164, more precisely, And the negative electrode 170 are formed in a horizontal direction.

In this state, when SiH ₄ and H ₂ , which are raw materials, are supplied through the gas distribution plate 140 and / or the auxiliary electrode 170, electrons accelerated by the high frequency electric field collide with the neutral gas, A plasma which is a mixture of electrons is generated.

At this time, as the internal pressure of the chamber 110 is higher, the number of collisions between the electrons and the neutral gas increases and a high density plasma can be obtained. Therefore, the process pressure is preferably maintained at 50 mTorr or more and 10 Torr or less.

The mechanism of formation of active species is as follows.

e ^- + SiH ₄ - > SiH ₃ ^* + H ^*

_{^{2e - + SiH 4 -> SiH}} 2 * + 2H *

_{^{3e - + SiH 4 -> SiH}} * + 3H *

The plasma generation mechanism is as follows.

e ^- + SiH ₄ - & gt ^; SiH ₃ ⁺ + H ^* + e ^-

2e ^- + SiH ₄ - & gt ^; SiH ₂ ^{2 +} + 2H ^* + 2e ^-

_{^{3e - + SiH 4 -> SiH}} 3 + + 3H * + 3e -

The generated active species, ions and electrons are incident on the grounded substrate stand 120 to form microcrystalline silicon on the substrate s.

In this process, a high-density plasma is generated due to the inductively coupled electric field formed between the main electrode 130 and the negative electrode 170, so that the deposition rate of microcrystalline silicon is greatly improved. When the raw material is supplied through the auxiliary electrode 170, the plasma uniformity of the periphery of the substrate pedestal 120 is compensated for, so that a uniform thin film can be formed.

On the other hand, the plasma processing apparatus 100 described above is very useful not only in the case of depositing a thin film but also in dry cleaning of the inside of a chamber. That _{is, NF 3, SF 6, F} 2, the chamber using an etching gas such as Cl _2, because due to the induced-binding electric field formed between the main electrode 130 and the negative electrode 170, it can generate a high density plasma The thin film deposited inside can be efficiently removed.

At this time, the plasma of the etch gas may be directly generated in the chamber and may be cleaned. Alternatively, a remote plasma generated outside the chamber may be sprayed inside the chamber 110 for cleaning.

Second Embodiment

5 shows a plasma processing apparatus 100 according to a second embodiment of the present invention. In the plasma processing apparatus 100, a first high frequency power source 191 having different frequencies and a second high frequency power source And the power supply 192 are simultaneously applied.

The main electrode 130 and the negative electrode 170 are connected to the secondary side of the transformer 196 in order to float the negative electrode 170. The primary side of the transformer 196 is connected to the negative electrode 170, The first high frequency power supply 191 and the second high frequency power supply 192 are connected together.

That is, the primary winding of the transformer 196 includes a winding connected to the first RF power supply 191 and a winding connected to the second RF power supply 192, and the first and second RF power supply 191 and 192 So that the magnetic flux is simultaneously linked to the secondary winding of the transformer 196.

At this time, the first high frequency power source 191 applies a high frequency power of 13.56 MHz or more, for example, and the second high frequency power source 192 can apply a high frequency power of a VHF band of 30 to 300 MHz, for example. At this time, the power of each of the high-frequency power supplies 191 and 192 can be adjusted according to the size of the chamber 110.

A first high frequency power supply 191 and a second high frequency power supply 192 are simultaneously applied to the secondary side of the transformer 196 so that two inductively coupled electric fields .

When electric fields of two frequencies are formed in this manner, the uniformity of the thin film can be further improved by canceling the standing wave pattern by each frequency.

The first and second matching circuits 193 and 194 are connected to the output terminals of the first RF power supply 191 and the second RF power supply 192. In order to prevent the two frequencies from influencing each other, It is preferable to install a filter. Since other structures are the same as those of the first embodiment, the duplicate description will be omitted.

Third Embodiment

6 is a cross-sectional view of a plasma processing apparatus 100 according to a third embodiment of the present invention, in which a separate high-frequency power source is connected to the main electrode 130 and the sub-electrode 170, respectively.

That is, a first high frequency power source 191 is connected to the flat main electrode 130 provided on the grounded substrate platform 120, and a ring shape (not shown) provided on the peripheral portion of the substrate facing platform 120 The second high frequency power source 192 is connected to the negative electrode 170.

For example, it is preferable that the first high frequency power source 191 is a power source of 30 to 300 MHz and the second high frequency power source 192 is a power source of 13.56 MHz, but a power source of the same frequency may also be used.

A first matching circuit 193 is provided between the first RF power supply 191 and the main electrode 130 and a second matching circuit 194 is provided between the second RF power supply 192 and the sub- .

The auxiliary electrode 170 is insulated from the chamber 110 through the insulating material 180 and the hollow tube is used as the auxiliary electrode 170 and the injection hole 172 can be formed in the same manner as in the first and second embodiments.

When the first and second high frequency power supplies 191 and 192 are respectively applied to the main electrode 130 and the negative electrode 170 in the plasma processing apparatus 100 according to the third embodiment of the present invention, An electric field in the vertical direction is formed between the counterbore 120 and an electric field in the horizontal direction is formed between the negative electrode 120 and the substrate counterbore 120.

When the vertical and horizontal electric fields are simultaneously formed in the chamber 110, a high density plasma can be obtained as compared with a case where only an electric field in the vertical direction is formed, and thus the deposition rate of the thin film can be greatly improved.

In addition, since the auxiliary electrode 120 is positioned at the periphery of the substrate table 120, the uniformity of plasma inside the chamber 110 is improved and the uniformity of the thin film can be greatly improved.

Although the plasma processing apparatus of the present invention is designed to improve the deposition rate and thin film uniformity of the microcrystalline silicon thin film, it may be used for depositing other kinds of thin films.

1 is a structural cross-sectional view of a general amorphous silicon thin film solar cell

2 is a cross-sectional view of the plasma processing apparatus according to the first embodiment of the present invention

Figs. 3A to 3B show various arrangements of the sub-electrodes

4A and 4B are diagrams showing various directions of the ejection hole of the sub-electrode

5 is a cross-sectional view of a plasma processing apparatus according to a second embodiment of the present invention

6 is a cross-sectional view of a plasma processing apparatus according to a third embodiment of the present invention

Description of the Related Art [0002]

100: plasma processing apparatus 110: chamber

120: substrate holder 130: main electrode

140; Gas distribution plate 150: gas supply pipe

160: high frequency power source 162: matching circuit

164: Transformer 166, 168: First and second feeder lines

170: negative electrode 172: injection hole

180: Insulation material

Claims (18)

A chamber having a reaction space; A substrate table installed inside the chamber; A main electrode provided on an upper portion of the substrate bench; A sub-electrode provided on an upper portion of a periphery of the substrate rest room and having a plurality of ejection holes for injecting gas onto the substrate rest room; Power supply means for supplying power to the main electrode and the sub-electrode; And a voltage regulating means provided between the power supply means and the main electrode and the sub electrode and being a transformer, Wherein the power supply means includes a first high frequency power source and a second high frequency power source having different frequencies, Wherein the high frequency power of the first high frequency power source and the second high frequency power are simultaneously applied to the main electrode and the sub electrode via the transformer. delete delete The method according to claim 1, The power supply means is connected to the primary side of the transformer, the main electrode is connected to the first terminal of the secondary side of the transformer, and the negative electrode is connected to the second terminal of the opposite polarity to the first terminal A plasma processing apparatus delete The method according to claim 1, A first matching circuit and a second matching circuit are provided between the first high frequency power source and the second high frequency power source and the transformer, respectively, and the first matching circuit and the second matching circuit prevent the influence of other high frequency power sources The plasma processing apparatus comprising: The method according to claim 1, Wherein the power supply means comprises: A first high frequency power source connected to the main electrode; A second high frequency power source connected to the negative electrode; And a plasma processing apparatus The method according to claim 1, Wherein the main electrode includes gas injection means for injecting gas to the upper portion of the substrate stand and an independent flow rate adjusting device is installed in each of the gas injection means and the gas supply pipe connected to the auxiliary electrode. Device The method according to claim 1, The main electrode A flat plate electrode sealing the upper portion of the chamber and connected to the power supply means; A gas distribution plate coupled to a lower portion of the plate electrode and electrically connected to the plate electrode; And a plasma processing apparatus The method according to claim 1, Wherein the main electrode and the sub-electrode are arranged to be insulated from the chamber. The method according to claim 1, Wherein the plurality of sub-electrodes are separated from each other, and power of the power supply unit is supplied to each of the sub-electrodes. The method according to claim 1, Wherein the auxiliary electrode is made of Cu, stainless steel (SUS), or anodized aluminum. The method according to claim 1, Wherein the substrate table is grounded at two or more points. The method according to claim 1, Wherein an inner pressure of the chamber is 50 mTorr or more and 10 Torr or less. 14. A method of depositing a microcrystalline silicon thin film using the plasma processing apparatus according to any one of claims 1, 4, and 6, Placing the substrate into the chamber and placing the substrate on the substrate bench; Applying power of the high frequency power source to the main electrode and the sub electrode; The main electrode and maintaining the said chamber by supplying SiH ₄ and H ₂ through the sub-electrode in a pressure range of 50mTorr to 10Torr, wherein by an electric field formed between the main electrode and the sub electrode SiH ₄ and H ₂ Generating a plasma comprising the active species and ions of the plasma; Forming a microcrystalline silicon (μc-Si: H) thin film on the substrate by causing the active species and ions to enter the substrate coater; A method of depositing a microcrystalline silicon thin film delete delete delete

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