WO2011099205A1 - Film formation device - Google Patents

Abstract

Disclosed is a film formation device which is easier to manufacture than conventional devices and which is capable of uniformly supplying a source gas to the surface of a substrate. The disclosed film formation device for forming thin films is provided with a first electrode (3) with a substrate (4) thereon, and a second electrode (2) which faces the substrate (4) and to which a high-frequency voltage is applied. The second electrode (2) has a shower plate (9) on a surface facing the substrate (4), and has one mesh plate (10) on a surface of the shower plate (9) which faces the substrate (4). The shower plate (9) has multiple holes (9a) through which the source gas is passed, and the mesh plate (10) has a mesh structure for passing the source gas (5) which has passed through the holes (9a) in the shower plate (9). Between the mesh plate (10) and the substrate (4), a space is provided in which plasma is generated.

Description

Deposition equipment

The present invention relates to a film forming apparatus for forming a thin film by plasma CVD.

In recent years, solar cells have been attracting attention as having the potential to contribute greatly to solving both energy and environmental problems. A solar cell is a power device that directly converts light energy into electric power using the photovoltaic effect. This solar cell is manufactured by sequentially stacking a p-type semiconductor film that is a silicon thin film, an i-type semiconductor film, and an n-type semiconductor film.

Plasma CVD (Chemical Vapor Deposition) is mentioned as a method for forming the silicon thin film as described above. In plasma CVD, a silicon thin film is deposited on a substrate by decomposing silane gas (SiH ₄ ) diluted with hydrogen in plasma. By changing the dilution rate of the silane gas, the temperature of the substrate on which the silicon thin film is deposited, etc., a hydrogenated amorphous silicon thin film and a microcrystalline silicon thin film are formed. Further, when phosphine containing phosphorus as an impurity is added to the source gas, an n-type semiconductor film is formed. Alternatively, when diborane containing boron as an impurity is added to the source gas, a p-type semiconductor film is formed. When no impurity is added to the source gas, an i-type semiconductor film is formed.

Specific examples of plasma CVD include capacitively coupled CVD, inductively coupled CVD, microwave CVD, and ECR-CVD (Electron-Cyclotron Resonance Chemical Vapor Deposition). Of these, capacitively coupled CVD is widely used. Since this capacitively coupled CVD excites plasma between a pair of parallel plate electrodes, the structure of the apparatus is simple compared to other methods, the uniformity of the formed film is high, and the large area of the film It has the advantage of being easy to make.

FIG. 3 shows a schematic diagram of a conventional film forming apparatus for forming a thin film by capacitively coupled CVD. The film forming apparatus of FIG. 3 includes a film forming chamber 51 that can be evacuated. In the film forming chamber 51, a first electrode 53 and a second electrode 52 are provided. Both the first electrode 53 and the second electrode 52 have a flat plate shape, and the flat portions of the flat plate shape face each other and are arranged in parallel. A high frequency power source 56 is connected to the second electrode 52, and the first electrode 53 is grounded. The second electrode 52 is provided with a source gas introduction pipe 58 for introducing the source gas 55 into the film forming chamber 51. Further, the second electrode 52 has a hollow structure. A shower plate 59 is provided on the substrate 54 side of the second electrode 52. The shower plate 59, a plurality of holes 59a are provided at intervals L _4. Further, the first electrode 53 is provided with a substrate 54 to be subjected to film formation. A heater 57 for heating the substrate 54 to a predetermined temperature is provided in the first electrode 53. Distance between the shower plate 59 and the substrate 54 is _{L 5.}

In the film forming apparatus shown in FIG. 3, the source gas 55 is supplied to the film forming chamber 51 evacuated through the source gas introducing pipe 58. High frequency power is supplied to the second electrode 52 from a high frequency power source 56. The source gas 55 supplied to the film forming chamber 51 is discharged through the second electrode 52 into the substrate 54 from a plurality of holes 59 a provided in the shower plate 59. The released source gas 55 is decomposed by the plasma generated between the first electrode 53 and the second electrode 52. As a result, a thin film is formed on the substrate 54.

In order to make a large-area solar cell, it is necessary to form a thin film with a uniform distribution over the entire surface of the substrate. It is necessary to supply the source gas 55 uniformly toward the substrate 54 and apply an electric field uniformly so that a discharge is uniformly generated between the substrate 54 and the second electrode 52 in FIG. Along with this, it is necessary to reduce the interval L ₄ holes 59a provided in the shower plate 59. To further enhance the uniformity of the raw material gas 55 emitted toward the substrate 54, the spacing L ₄ of the holes 59a of the shower plate 59 is made smaller than the distance L ₅ between the shower plate 59 and the substrate 54 It is preferable. As a result, the number of holes 59a formed in the shower plate 59 is very large. For example, when holes are formed in a 1 m ² electrode at intervals of 10 mm, the number of holes is 10,000. It takes a long time to process such many holes. In addition, the shape of the hole has been changed to a nozzle shape. In this case, laser processing is used, but further time is required for processing.

As such a film forming apparatus that does not use a shower plate that requires a long time for processing, a device as described in Patent Document 1 can be cited. In the film forming apparatus described in Patent Document 1, the surface of the second electrode facing the first electrode has a mesh structure instead of providing a shower plate.

Further, as a film forming apparatus using both a shower plate and a mesh plate having a mesh structure, there is a device as described in Patent Document 2. In the film forming apparatus described in Patent Document 2, three mesh plates are stacked, and plasma is confined inside the mesh structure of the stacked mesh plates.

JP 2000-31512 A JP 2009-141116 A

In a conventional film forming apparatus using capacitively coupled plasma CVD, when forming a film at a high pressure, it is necessary to reduce the distance between the first electrode and the second electrode. In order to supply the source gas uniformly in such an apparatus, it is necessary to provide many holes in the shower plate. Processing for providing such many holes in the shower plate is not easy.

On the other hand, in the film forming apparatus described in Patent Document 1, the source gas supplied to the second electrode is released toward the substrate only through the mesh provided on the second electrode. Since there is no mechanism other than the mesh for diffusing the source gas, it is difficult to uniformly release the source gas over the entire surface of the substrate when forming a thin film having a large area.

Further, in the film forming apparatus described in Patent Document 2, since the plasma is confined inside the mesh structure of three mesh plates laminated, it becomes a follow cathode plasma, which is different from the parallel plate plasma. In addition, it is difficult to uniformly decompose the source gas released toward the substrate with plasma.

In view of the above problems, an object of the present invention is to provide a film forming apparatus that is easier to manufacture than the prior art and that can uniformly supply a source gas toward a substrate.

In order to achieve the above object, a film forming apparatus for forming a thin film on a substrate by generating a plasma between the first electrode and the second electrode according to the present invention and decomposing the source gas has the substrate disposed. And a second electrode facing the substrate and to which a high frequency voltage is applied. The second electrode has a shower plate on the surface facing the substrate and a mesh plate on the surface of the shower plate facing the substrate. The shower plate has a plurality of holes through which the source gas passes. The mesh plate has a mesh structure for allowing the source gas that has passed through the holes of the shower plate to pass therethrough. A space for generating the plasma is provided between the mesh plate and the substrate.

In order to achieve the above object, a film forming apparatus for forming a thin film on a substrate by generating a plasma between the first electrode and the second electrode according to the present invention and decomposing the source gas has the substrate disposed. And a second electrode facing the substrate and to which a high frequency voltage is applied. The second electrode has a shower plate on the surface facing the substrate, and a ladder plate on the surface of the shower plate facing the substrate. The shower plate has a plurality of holes through which the source gas passes. Further, the ladder plate has a ladder structure for allowing the source gas that has passed through the holes of the shower plate to pass therethrough. A space for generating the plasma is provided between the ladder plate and the substrate.

According to another aspect of the film forming apparatus, the interval between the plurality of holes provided in the shower plate is smaller than or equal to the interval between the substrate on the first electrode and the shower plate.

According to another embodiment of the film forming apparatus, the interval between the shower plate and the mesh plate is larger than the interval between the mesh plate and the substrate.

According to another embodiment of the film forming apparatus, the interval between the shower plate and the ladder plate is larger than the interval between the ladder plate and the substrate.

A film forming apparatus for forming a thin film on a substrate by generating a plasma between the first electrode and the second electrode according to the present invention to decompose the source gas, the first electrode having the substrate disposed thereon, A second electrode facing the substrate and to which a high frequency voltage is applied. The second electrode has a shower plate on the surface facing the substrate and a mesh plate on the surface of the shower plate facing the substrate. The shower plate has a plurality of holes through which the source gas passes. The mesh plate has a mesh structure for allowing the source gas that has passed through the holes of the shower plate to pass therethrough. A space for generating the plasma is provided between the mesh plate and the substrate. According to such a film forming apparatus, since the source gas passes through the shower plate and then passes through the mesh plate and is released to the substrate, the uniformity of the source gas released to the substrate is increased. Furthermore, since this film forming apparatus has a shower plate and a mesh plate, the number of holes in the shower plate can be reduced compared to the conventional case, and as a result, the processing of the shower plate is easier than before. Become.

A film forming apparatus for forming a thin film on a substrate by generating a plasma between the first electrode and the second electrode according to the present invention to decompose the source gas, the first electrode having the substrate disposed thereon, A second electrode facing the substrate and to which a high frequency voltage is applied. The second electrode has a shower plate on the surface facing the substrate, and a ladder plate on the surface of the shower plate facing the substrate. The shower plate has a plurality of holes through which the source gas passes. Further, the ladder plate has a ladder structure for allowing the source gas that has passed through the holes of the shower plate to pass therethrough. A space for generating the plasma is provided between the ladder plate and the substrate. According to such a film forming apparatus, since the source gas passes through the ladder plate after passing through the shower plate and is released to the substrate, the uniformity of the source gas released to the substrate is increased. Furthermore, since this film forming apparatus has a shower plate and a ladder plate, the number of holes in the shower plate can be reduced compared to the conventional case, and as a result, the processing of the shower plate is easier than before. Become.

According to another form of the film forming apparatus, the interval between the plurality of holes provided in the shower plate is smaller than or equal to the interval between the substrate on the first electrode and the shower plate, The source gas can be supplied more uniformly toward the substrate.

According to another form of the film forming apparatus, since the interval between the shower plate and the mesh plate is larger than the interval between the mesh plate and the substrate, the source gas is interposed between the shower plate and the mesh plate. As a result, the source gas can be supplied more uniformly toward the substrate.

According to another form of the film forming apparatus, since the interval between the shower plate and the ladder plate is larger than the interval between the ladder plate and the substrate, the source gas is provided between the shower plate and the ladder plate. As a result, the source gas can be supplied more uniformly toward the substrate.

It is sectional drawing of the film-forming apparatus provided with the shower board and the mesh board. FIG. 2A is a plan view of the mesh plate, and FIG. 2B is a plan view of the ladder plate. It is sectional drawing of the conventional film-forming apparatus.

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

FIG. 1 is a cross-sectional view of a film forming apparatus for forming a thin film by plasma CVD. The film forming apparatus shown in FIG. 1 includes a film forming chamber 1. The film forming chamber 1 can be evacuated to a high vacuum, and the pressure in the chamber can be kept constant. In the film formation chamber 1, the 1st electrode 3 and the 2nd electrode 2 are provided, and both are arrange | positioned in parallel. The second electrode 2 is provided with a source gas introduction pipe 8 for supplying the source gas 5 into the film forming chamber 1. A high frequency power source 6 is connected to the second electrode 2, and the first electrode 3 is grounded. A substrate 4 that is a target for forming a thin film is disposed on the first electrode 3. A heater 7 is provided in the first electrode 3 for heating the first electrode 3 and the substrate 4 to a predetermined temperature.

The second electrode 2 has a hollow structure. A shower plate 9 is provided on the substrate 4 side of the second electrode 2. This shower plate 9 is provided with a plurality of holes 9a, spacing of these holes 9a is L _1. Further, a single mesh plate 10 is provided on the second electrode 2. The mesh plate 10 is provided at a position closer to the substrate 4 than the shower plate 9. The mesh plate 10 is a braided metal wire as shown in FIG. The mesh interval of the mesh plate 10 is sufficiently fine. Distance between the shower plate 9 and the mesh plate 10 is L _2. The distance between the mesh plate 10 and the substrate 4 is _{L 3.} The interval L ₁ between the holes 9 a of the shower plate 9 is preferably smaller than or equal to the interval L ₂ + L ₃ between the shower plate 9 and the substrate 4. Furthermore, the interval L ₂ between the shower plate 9 and the mesh plate 10 is preferably larger than the interval L ₃ between the mesh plate 10 and the substrate 4.

In the film forming apparatus configured as described above, after the film forming chamber 1 is evacuated, the first electrode 3 is heated by the heater 7 to bring the substrate 4 to a predetermined temperature. The source gas 5 is supplied to the second electrode 2 through the source gas introduction pipe 8, passes through the holes 9 a provided in the shower plate 9, and then passes through the mesh holes of the mesh plate 10. Supplied between the substrate 4. At this time, the flow rate of the source gas 5 is set to a predetermined value, and the pressure in the film forming chamber 1 is kept constant. On the other hand, the high frequency power source 6 applies high frequency power to the second electrode 2. Then, plasma is generated between the mesh plate 10 provided on the second electrode 2 and the substrate 4. The source gas 5 supplied between the mesh plate 10 and the substrate 4 is decomposed by this plasma, and a thin film is formed on the substrate 4. At this time, since the mesh interval of the mesh plate 10 is sufficiently fine as described above, the generated plasma does not enter between the shower plate 9 and the mesh plate 10.

According to the film forming apparatus shown in FIG. 1, since the source gas 5 passes through the shower plate 9 and then passes through the mesh plate 10 and is released to the substrate 4, the interval L ₁ between the holes 9a of the shower plate 9 is released. The source gas 5 can be uniformly supplied toward the substrate 4 without reducing the flow rate so much. As a result, the shower plate 9 can be easily processed. Further, the distance L ₁ of the hole 9a of the shower plate 9, by less than or equal to distance L _{2 +} L ₃ of the shower plate 9 and the substrate 4, uniformity of the raw material gas 5 discharged toward the substrate 4 The sex can be increased. Further, in plasma CVD, the distance L ₃ between the mesh plate 10 and the substrate 4 is determined by the film forming conditions such as pressure and power, but the distance L ₂ between the shower plate 9 and the mesh plate 10 is made larger than the distance L _3. Thus, the source gas 5 can be sufficiently diffused between the shower plate 9 and the mesh plate 10. As a result, the uniformity of the source gas 5 released toward the substrate 4 is further increased.

[Example 1]
In this embodiment, a microcrystalline silicon (μc-Si) thin film is formed using the film forming apparatus shown in FIG. The shower plate 9, the hole 9a of diameter 1mm for passing the raw material gas is provided, the distance L ₁ of the holes 9a is 20 mm. Distance _{L 2} between the shower plate 9 and the mesh plate 10 of the second electrode within 2 is 15 mm, the interval _{L 3} between the mesh plate 10 and the substrate 4 is 5 mm. That is, the interval (L ₁ = 20 mm) between the holes 9 a of the shower plate 9 is equal to the interval (L ₂ + L ₃ = 20 mm) between the shower plate 9 and the substrate 4. The mesh plate 10 is formed by braiding metal wires having a diameter of 0.4 mm at intervals of 1.5 mm. The source gas 5 is a mixed gas of silane (SiH ₄ ) and hydrogen. The flow rate of silane is 20 sccm and the flow rate of hydrogen is 2000 sccm. The pressure in the film forming chamber 1 is 12 Torr. The temperature of the substrate 4 is 200 degrees. The frequency of the high frequency power supply 6 is 27 MHz, and the power is 300 W.

A microcrystalline silicon thin film is formed by the film forming apparatus having such a structure. In order to evaluate the formed microcrystalline silicon thin film, the degree of crystallization is compared with respect to the mesh holes of the mesh plate 10 and the silicon film on the substrate facing the intermediate position between the mesh holes. Raman spectroscopy is used to measure crystallization. In the Raman spectrum, the height of the amorphous silicon (a-Si) peak (wave number 480 cm ⁻¹ ) is Ia, and the height of the crystalline Si peak (wave number 520 cm ⁻¹ ) is Ic. The ratio Ic / Ia between the two is used as a parameter representing the crystallization rate.

The value of Ic / Ia at the position on the silicon film facing the hole 9a of the shower plate 9 was 4.3. Further, the value of Ic / Ia at the position on the silicon film facing the intermediate position between the holes of the shower plate 9 was 4.5. Both values were almost equal.

From the observation result of the plasma during the film formation and the observation result of the second electrode 2 after the film formation, it was found that no plasma was generated between the mesh plate 10 and the shower plate 9.

[Example 2]
Also in this embodiment, a microcrystalline silicon thin film is formed using the film forming apparatus shown in FIG. Distance _{L 2} between the shower plate 9 and the mesh plate 10 of the second electrode within 2 is 5mm, the spacing _{L 3} is also 5mm between the mesh plate 10 and the substrate 4. Others are the same as in the first embodiment. That is, the interval between the holes 9a of the shower plate 9 (L ₁ = 20 mm) is larger than the interval between the shower plate 9 and the substrate 4 (L ₂ + L ₃ = 10 mm).

The microcrystalline silicon thin film formed by the film forming apparatus having such a configuration was evaluated in the same manner as in Example 1. Then, the value of Ic / Ia at the position on the silicon film facing the position of the hole 9a of the shower plate 9 was 3.4. Further, the value of Ic / Ia at the position on the silicon film facing the middle position between the holes of the shower plate 9 was 4.8. Compared to Example 1 above, it was found that the value of Ic / Ia differs depending on the position on the silicon film. One reason for this is considered to be that the uniformity of the source gas 5 released toward the substrate 4 is lowered due to the small distance (L ₂ + L ₃ ) between the shower plate 9 and the substrate 4 being 10 mm.

[Reference example]
In this reference example, a microcrystalline silicon thin film is formed using the conventional film forming apparatus shown in FIG. The shower plate 59 is provided with a hole 59a having a diameter of 1 mm. Spacing _{L 4} of the holes 59a is 20 mm. A distance L ₅ between the shower plate 59 and the first electrode 53 in the second electrode 52 is 5 mm. That is, the distance between the holes 59a (L ₄ = 20 mm) is larger than the distance between the shower plate 59 and the first electrode 53 (L ₅ = 5 mm). The source gas 55 is a mixed gas of silane (SiH ₄ ) and hydrogen. The flow rate of silane is 20 sccm and the flow rate of hydrogen is 2000 sccm. The pressure in the film forming chamber 51 is 12 Torr, and the temperature of the substrate 54 is 200 degrees. The frequency of the high frequency power supply 56 is 27 MHz, and the power is 300 W.

The microcrystalline silicon thin film formed by the film forming apparatus having such a configuration was evaluated in the same manner as in Example 1. Then, the value of Ic / Ia at the position on the silicon film facing the hole 59a of the shower plate 59 was amorphous silicon of about 1. Further, the value of Ic / Ia at the position on the silicon film facing the intermediate position between the hole 59a and the hole 59a of the shower plate 59 was 5.4. Both results did not agree. It was also found that the film quality of the formed silicon film was not uniform depending on the location. Further, a pattern corresponding to the hole 59a of the shower plate 59 appeared, and it was visually confirmed that the pattern corresponding to the hole 59a was cloudy. It was also confirmed that this part was amorphous silicon. It was found that the distribution was improved in Example 1 as compared with this reference example.

In another embodiment, a single ladder plate 11 is used instead of the mesh plate 10 shown in FIG. The ladder plate 11 has a configuration in which metal wires are arranged at a certain interval as shown in FIG. Since the ladder plate 11 is easier to process than the mesh plate 10, the film forming apparatus can be easily manufactured. According to such a film forming apparatus, since the source gas 5 passes through the shower plate 9 and then passes through the ladder plate 11 and is released to the substrate 4, the source gas 5 is uniformly supplied toward the substrate 4. can do.

Further, the distance L ₁ of the hole 9a of the shower plate 9, by less than or equal to distance L _{2 +} L ₃ of the shower plate 9 and the substrate 4, uniformity of the raw material gas 5 discharged toward the substrate 4 The sex can be increased. Furthermore, the source gas 5 is diffused between the shower plate 9 and the ladder plate 11 by making the interval L ₂ between the shower plate 9 and the ladder plate 11 larger than the interval L ₃ between the ladder plate 11 and the substrate 4. Can be made. As a result, the uniformity of the source gas 5 released toward the substrate 4 is further increased.

DESCRIPTION OF SYMBOLS 1 Deposition chamber 2 Second electrode 3 First electrode 4 Substrate 5 Raw material gas 6 High frequency power supply 7 Heater 8 Raw material gas introduction tube 9 Shower plate 9a Hole provided in shower plate 9 10 Mesh plate 11 Ladder plate 51 Deposition chamber 52 Second electrode 53 First electrode 54 Substrate 55 Source gas 56 High frequency power source 57 Heater 58 Source gas introduction pipe 59 Shower plate 59a Hole provided in the shower plate 59

Claims (5)

A film forming apparatus for forming a thin film on a substrate by generating a plasma between a first electrode and a second electrode to decompose a source gas,
A first electrode on which a substrate is disposed;
A second electrode that is opposed to the substrate and to which a high-frequency voltage is applied, and the second electrode has a shower plate on a surface facing the substrate, and the second plate has a shower plate on the substrate of the shower plate. The facing plate has a single mesh plate, the shower plate has a plurality of holes through which the source gas passes, and the mesh plate receives the source gas that has passed through the holes in the shower plate. A film forming apparatus having a mesh structure for allowing passage, and a space for generating the plasma is provided between the mesh plate and the substrate. A film forming apparatus for forming a thin film on a substrate by generating a plasma between a first electrode and a second electrode to decompose a source gas,
A first electrode on which a substrate is disposed;
A second electrode that is opposed to the substrate and to which a high-frequency voltage is applied, and the second electrode has a shower plate on a surface facing the substrate, and the second plate has a shower plate on the substrate of the shower plate. The facing plate has a single ladder plate, the shower plate has a plurality of holes through which the source gas passes, and the ladder plate receives the source gas that has passed through the holes in the shower plate. A film forming apparatus having a ladder structure for passing through, wherein a space for generating the plasma is provided between the ladder plate and the substrate. 3. The film forming apparatus according to claim 1, wherein an interval between the plurality of holes provided in the shower plate is smaller than or equal to an interval between the substrate on the first electrode and the shower plate. The film forming apparatus according to claim 1, wherein an interval between the shower plate and the mesh plate is larger than an interval between the mesh plate and the substrate. 3. The film forming apparatus according to claim 2, wherein an interval between the shower plate and the ladder plate is larger than an interval between the ladder plate and the substrate.

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