JP4335389B2 - Manufacturing method of silicon-based thin film photoelectric conversion device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a plasma CVD apparatus and a method for manufacturing a silicon thin film photoelectric conversion apparatus including a step of forming a crystalline silicon thin film photoelectric conversion layer using the plasma CVD apparatus.
[0002]
Note that in this specification, the terms “crystalline” and “microcrystalline” also mean those partially including an amorphous state.
[0003]
[Prior art]
An amorphous silicon solar cell is known as a typical thin film photoelectric conversion device. Since the amorphous photoelectric conversion material used for this solar cell can be formed by a plasma CVD method under a film forming temperature as low as about 200 ° C., an inexpensive material such as glass, stainless steel, or an organic film can be used as a substrate. . As a result, the amorphous photoelectric conversion material is expected as a promising material for producing a low-cost photoelectric conversion device. In addition, since amorphous silicon has a large absorption coefficient in the visible light region, it is 15 mA / cm in a solar cell having a photoelectric conversion layer made of amorphous silicon with a thin film thickness of 500 nm or less.²The above short circuit current is realized.
[0004]
However, amorphous silicon materials have problems such as deterioration of photoelectric conversion characteristics due to the Stebler-Wronsky effect when subjected to light irradiation for a long time, and the effective sensitivity wavelength region is limited to about 800 nm. Yes. Therefore, in the photoelectric conversion device using an amorphous silicon-based material, there is a limit to its reliability and high performance, and the original advantages that the degree of freedom of substrate selection and low-cost processes can be used are sufficient. Is not alive.
[0005]
For these reasons, in recent years, photoelectric conversion devices using thin films containing crystalline silicon such as polycrystalline silicon and microcrystalline silicon have been vigorously developed. These developments are attempts to achieve both low cost and high performance of the photoelectric conversion device by forming a high-quality crystalline silicon thin film on an inexpensive substrate by a low-temperature process. Application to various photoelectric conversion devices such as is expected.
[0006]
As a method for forming a crystalline silicon thin film, for example, it is directly deposited on a substrate by a CVD method or a sputtering method, or an amorphous film is once deposited by a similar process, followed by thermal annealing or laser annealing. There are known methods for achieving this. In any method, in order to use the above-described inexpensive substrate, it is necessary to set the temperature during film formation to 550 ° C. or lower.
[0007]
Among the above-mentioned film forming processes, the technique of directly depositing a crystalline silicon thin film by plasma CVD is the easiest to reduce the process temperature and increase the area of the thin film, and is a relatively simple process with high quality crystals. A thin film is expected to be obtained.
[0008]
By the way, as an apparatus used in the plasma CVD method, a device having the following structure is conventionally known. In the rectangular reaction vessel, exhaust pipes, which are exhaust members, are connected to opposite side walls. The other end of the exhaust pipe is connected to a vacuum pump or the like. A valve for taking in and out the substrate is provided on the opposite side wall of the reaction vessel. The rectangular anode electrode is supported and suspended by a support shaft in the reaction vessel. A heater (not shown) for heating the substrate to be held is incorporated under the anode electrode. The anode electrode is connected to, for example, the ground. The rectangular cathode electrode is disposed in the reaction container so as to face the lower surface of the anode electrode, and a reaction gas is supplied through a gas supply pipe.
[0009]
The cathode electrode has a plurality of non-penetrating gas blowing holes opened on the front surface facing the anode electrode. A gas introduction hole having a diameter smaller than that of the hole is formed in the back surface portion of the gas blowing hole. For example, a high frequency power source is connected to the cathode electrode.
[0010]
In the plasma CVD apparatus having such a configuration, the substrate is held on the anode electrode in the reaction vessel through the valve, and the substrate is heated to a desired temperature by heat generation of a heater (not shown) built in the anode electrode. A reactive gas (for example, a reactive gas containing a silane-based gas and hydrogen) is supplied to a cathode electrode through a gas supply pipe, and blown out to a gas blowing hole through a gas introduction hole arranged on the upper portion thereof. At the same time, an exhaust device such as a vacuum pump is driven to exhaust the gas in the reaction vessel through an exhaust pipe to maintain the inside of the reaction vessel at a predetermined degree of vacuum.
[0011]
For example, high frequency power is applied from the power source to the cathode electrode in a state where the degree of vacuum in the reaction vessel is stable. By applying such high frequency power, weak plasma is generated between the cathode electrode and the substrate, and strong plasma is generated near the opening of the gas blowing hole of the cathode electrode by the holo cathode effect. When such plasma is generated, the reaction gas (silane-based gas) is decomposed therein and silicon is deposited on the substrate surface heated to the desired temperature (for example, 550 ° C. or lower) to form a silicon thin film. Be filmed.
[0012]
In the conventional CVD apparatus described above, since strong discharge is mainly performed inside the cathode electrode, plasma can be generated inside the cathode electrode, and ion damage to the thin film formed on the substrate can be suppressed.
[0013]
[Problems to be solved by the invention]
An object of the present invention is to provide a plasma CVD apparatus capable of generating a more stable plasma and forming a thin film having a uniform film thickness and film quality at a high speed.
[0014]
In the present invention, when a photoelectric conversion unit having a silicon-based photoelectric conversion layer is stacked, a high-quality silicon-based photoelectric conversion layer having a uniform film thickness and film quality is formed at high speed using the plasma CVD apparatus. It aims at providing the manufacturing method of the silicon type thin film photoelectric conversion apparatus which achieved the improvement.
[0015]
[Means for Solving the Problems]
  According to the present inventionA method for manufacturing a silicon-based thin film photoelectric conversion device includes at least one photoelectric conversion unit formed on a substrate. The photoelectric conversion unit includes one conductive semiconductor layer sequentially stacked by plasma CVD, and at least one silicon. A method of manufacturing a silicon-based thin film photoelectric conversion device including a silicon-based thin film photoelectric conversion layer and a reverse conductivity type semiconductor layer,
  A reaction vessel having an exhaust member; an anode electrode disposed in the reaction vessel; a holocathode-type cathode electrode disposed in the reaction vessel opposite to the anode electrode; and a reaction gas in the cathode electrode A gas supply means for supplying and a power source for applying electric power to the cathode electrode, wherein the cathode electrode has a plurality of gas blowing holes on the front surface facing the anode electrode; A gas introduction hole having a diameter smaller than that of the hole formed so as to communicate with these holes in a portion, and the diameter of each gas blowing hole is in the vicinity of the inner peripheral surface of the hole under discharge conditions during film formation Providing a plasma CVD apparatus that is more than twice the distance of the formed plasma sheath and less than or equal to 12 times;
  Holding the substrate on which the one-conductivity-type semiconductor layer is formed on the anode electrode in the reaction vessel of the plasma CVD apparatus;
  Power is supplied from the power source to the cathode electrode, and a reactive gas containing a silane-based gas and hydrogen gas is blown out from a gas blowing hole through the plurality of gas introduction holes, and plasma is mainly generated in the vicinity of the gas blowing hole by a holo cathode effect. Forming a silicon-based thin film photoelectric conversion layer on the one-conductivity-type semiconductor layer of the substrate by generating
Including
  The substrate temperature during film formation is set to 100 to 400 ° C., and the pressure in the reaction vessel is set to 5 Torr or more.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a plasma CVD apparatus according to the present invention will be described in detail with reference to FIGS.
[0018]
1 is a schematic view showing a plasma CVD apparatus according to the present invention, FIG. 2 is a cross-sectional view of the main part of the plasma CVD apparatus of FIG. 1, FIG. 3 is a view taken along the line III-III of FIG. It is an expanded sectional view of the gas blowing plate which has the gas blowing hole of a hollow cathode electrode.
[0019]
The rectangular reaction vessel 1 has exhaust pipes 2 and 2 that are exhaust members connected to opposite side walls. The other ends of the exhaust pipes 2 and 2 are connected to a vacuum pump or the like (not shown). A valve (not shown) for taking in and out the substrate is provided on the opposite side wall of the reaction vessel 1.
[0020]
A rectangular anode electrode 3 is supported and suspended in the reaction vessel 1 by a support shaft 4. A heater (not shown) for heating the substrate to be held is built in the lower part of the anode electrode 3. The anode electrode 3 is connected to the ground, for example.
[0021]
A shield member 6 having a bottomed rectangular frame shape and having a cylindrical body 5 that penetrates through the reaction vessel 1 and communicates with the bottom portion is disposed to face the anode electrode 3. A bottomed rectangular frame-shaped cathode support member 8 in which a gas supply pipe 7 inserted into the cylindrical body 5 communicates with the bottom is disposed in the shield member 6 via an insulating material or air-insulated. ing.
[0022]
As shown in FIGS. 1 to 3, the cathode electrode 9 is supported and fixed on the cathode support member 8 so as to face the anode electrode 23. A power source, for example, a high frequency power source (not shown) is connected to the hollow cathode electrode 9.
[0023]
The cathode electrode 9 has a plurality of cylindrical non-penetrating gas blowing holes 10 in the front surface facing the anode electrode 3. As shown in FIG. 4, each gas blowing hole 10 has a diameter (L) of a distance (L) between the annular plasma sheaths 11 formed in the vicinity of the inner peripheral surface of the hole 10 under discharge conditions during film formation._s) Over 2 times and up to 12 times. Here, the plasma sheath means an essentially unipolar charged particle layer densely packed around the plasma object. A gas introduction hole 12 communicating with these holes 10 and having a diameter smaller than that of the holes 10 is formed in the rear portion of each non-penetrating gas blowing hole 10 at the portion of the kasort electrode 9. The gas dispersion plate 13 is disposed in the bottomed rectangular frame-like cathode support member 8 so as to face the cathode electrode 9 and be separated by a desired distance.
[0024]
The diameter (L) of each gas blowing hole 10 is set to the distance (L) of the plasma sheath 11 under the discharge conditions during film formation._sThe reason why it is more than 2 times and less than 12 times) is as follows. The diameter (L) of the gas blowing hole 10 is set to the distance (L_s) Or less), the diameter becomes within the sheath distance, and it becomes difficult to generate normal plasma in the gas blowing hole, and the plasma is mainly generated between the cathode electrode and the anode electrode. On the other hand, the diameter (L) of the gas blowing hole 10 is equal to the distance (L_s) Exceeds 12 times, the diameter of the gas blowing hole increases, the number of gas blowing holes 10 that can be drilled in the cathode electrode 9 decreases, and the parallel portion between the inside of the holocathode and the substrate held by the anode electrode Since the repetition interval becomes large, the plasma may become strong and weak, and the plasma may become unstable. A more preferable diameter (L) of the gas blowing hole 10 is a distance (L) of the plasma sheath 11._s) 3 to 8 times.
[0025]
Next, the operation of the plasma CVD apparatus having the configuration shown in FIGS.
[0026]
First, the substrate 14 is held on the anode electrode 3 in the reaction vessel 1 through a valve (not shown), and the substrate 13 is heated to a desired temperature by heat generation of a heater (not shown) built in the anode electrode 3. A reactive gas (for example, a reactive gas containing a silane-based gas and hydrogen) is supplied into a cathode support member 8 having a bottomed rectangular frame shape through a gas supply pipe 7, and is passed through a gas dispersion plate 13 disposed in the support member 8. Further, the gas is blown out from the plurality of gas introduction holes 12 and the gas blowing holes 10 of the cathode electrode 9. At the same time, an exhaust device such as a vacuum pump (not shown) is driven to exhaust the gas in the reaction vessel 1 through the exhaust pipes 2 and 2 to keep the reaction vessel 1 at a predetermined degree of vacuum.
[0027]
For example, high frequency power is applied to the cathode electrode 5 from a power source (not shown) while the degree of vacuum in the reaction vessel 1 is stable. By applying such high frequency power, a weak plasma 15 is formed between the cathode electrode 9 and the substrate 14.₁And a strong plasma 15 near the opening of the gas blowing hole 10 of the cathode electrode 9 due to the holocathode effect.₂Occurs. Plasma 15₁, 15₂Is generated, the reaction gas (silane-based gas) is decomposed therein, and silicon is deposited on the surface of the substrate 14 heated to the desired temperature (for example, 550 ° C. or lower) to form a silicon thin film. .
[0028]
At the time of film formation described above, the cathode electrode 9 is disposed at a portion facing the anode electrode 3, and the diameter (L) of the cathode electrode 9 is blown out in accordance with the discharge conditions at the time of film formation as shown in FIG. The distance (L of the annular plasma sheath 11 formed near the inner peripheral surface of the hole 10_s2) and 12 times or less, a strong plasma 15 near the opening of the gas blowing hole 10 of the cathode electrode 9 is formed.₂Can be generated stably. That is, by setting the diameter of the gas blowing hole 10 to an appropriate size (dimension) in relation to the distance of the plasma sheath 11 formed near the inner surface of the hole 10 under the discharge conditions during film formation, The discharge involved in the generation can be stabilized. As a result, a thin film having a uniform film thickness and film quality can be formed on the substrate 14 at a high speed.
[0029]
Further, the anode electrode 3 and the cathode electrode 9 are arranged to face each other, and are discharged under film forming conditions, and the distance (L) of the plasma sheath generated in the plurality of gas blowing holes 10 formed in the cathode electrode 9_s) Is measured, the diameter of the gas blowing hole 10 for performing normal discharge (plasma generation) by the holocathode effect can be designed. As a result, the cathode electrode 9 having the gas blowing hole 10 designed in this way is manufactured and incorporated in a plasma CVD apparatus, so that plasma can be generated by stable discharge, so that it has a uniform film thickness and film quality. A thin film can be deposited on the substrate.
[0030]
As shown in FIG. 1, the plasma CVD apparatus according to the present invention is not limited to the upflow type in which the anode electrode is disposed on the upper side and the cathode electrode is disposed on the lower side, but the anode electrode is disposed on the lower side and the cathode electrode is disposed on the upper side. The same applies to the downflow type. Further, the present invention can be similarly applied to a vertical flow type in which an anode electrode and a cathode electrode are arranged upright.
[0031]
The gas blowing hole is not limited to a cylindrical shape, and may be a triangular prism, a quadrangular prism, or a hexagonal prism.
[0032]
Next, a method for manufacturing a silicon-based thin film photoelectric conversion device according to the present invention will be described with reference to FIG.
[0033]
FIG. 5 is a perspective view schematically showing a silicon-based thin film photoelectric conversion device manufactured according to one embodiment of the present invention.
[0034]
(First step)
First, the back electrode 110 is formed on the substrate 101.
[0035]
As the substrate 101, for example, a metal such as stainless steel, an organic film, an inexpensive glass having a low melting point, or the like can be used.
[0036]
The back electrode 110 includes, for example, a metal thin film 102 including a layer made of at least one metal selected from Ti, Cr, Al, Ag, Au, Cu, and Pt, or an alloy thereof, and ITO, SnO.₂, And at least one oxide selected from ZnO, and the transparent conductive thin film 103 is formed by laminating in this order. However, the back electrode 110 may be formed of only the metal thin film 102 or the transparent conductive thin film 103. These thin films 102 and 103 are formed, for example, by vapor deposition or sputtering.
[0037]
(Second step)
Next, the photoelectric conversion unit 111 is formed by sequentially laminating the one-conductivity-type semiconductor layer 104, the crystalline silicon-based thin-film photoelectric conversion layer 105, and the reverse-conductivity-type semiconductor layer 106 on the back electrode 110 by plasma CVD. The photoelectric conversion unit 111 is not limited to one unit, and a plurality of units may be formed on the back electrode.
[0038]
The one-conductivity-type semiconductor layer 104, the crystalline silicon-based thin film photoelectric conversion layer 105, and the reverse-conductivity-type semiconductor layer 106 will be described in detail below.
[0039]
1) One conductivity type semiconductor layer 104
The one-conductivity-type semiconductor layer 104 is, for example, an n-type silicon layer doped with phosphorus, which is a conductivity-type determining impurity atom, by 0.01 atomic% or more, or a p-type silicon layer doped with 0.01 atomic% or more of boron. Can be used. However, these conditions regarding the one-conductivity type semiconductor layer 104 are not limited, and the impurity atom may be aluminum or the like in a p-type silicon layer, or an alloy material such as silicon carbide or silicon germanium may be used. Good.
[0040]
The one-conductivity-type silicon-based thin film 104 may be polycrystalline, microcrystalline, or amorphous, and its film thickness is preferably 1 to 100 nm, more preferably 2 to 30 nm.
[0041]
2) Crystalline silicon-based thin film photoelectric conversion layer 105
The crystalline silicon-based thin film photoelectric conversion layer 105 is formed, for example, by using the plasma CVD apparatus shown in FIGS. 1 to 4 described above, and a semiconductor layer 104 of one conductivity type is formed in advance on the anode electrode 3 in the reaction vessel 1. The substrate 101 (14) is held, power is supplied from the power source to the cathode electrode 9, the anode electrode 3 is grounded, and a reaction gas containing silane-based gas and hydrogen gas is passed through the gas supply pipe 7 to form a bottomed rectangle. The gas is supplied into the frame-like cathode support member 8, passed through the gas dispersion plate 13 disposed in the support member 8, and further, the plurality of gas introduction holes 12 of the cathode electrode 9 and the plasma sheath 11 as shown in FIG. From the gas blowing hole 10 set to an appropriate size (dimension) in relation to the distance of the plasma, a weak plasma 15 is formed between the cathode electrode 9 and the substrate 14 (101).₁And a strong plasma 15 near the opening of the gas blowing hole 10 of the cathode electrode 9 due to the holocathode effect.₂Is stably generated to form a film at a high speed.
[0042]
In the film forming step, the heating temperature of the silicon deposition portion of the substrate by the heater built in the anode electrode 3 is preferably set to 550 ° C. or less that enables the use of an inexpensive substrate such as glass.
[0043]
In the film forming step, it is preferable to set the pressure in the reaction vessel 1 to a high pressure of 5 Torr or more. By setting such conditions, it is possible to further reduce ion damage to the crystalline silicon thin film formed on the surface of the substrate 14. As a result, in order to increase the deposition rate, the high frequency power is increased (for example, the plasma discharge power density is 100 mW / cm²Even if the gas flow rate is increased, the crystalline silicon-based thin film photoelectric conversion layer can be formed at a high speed by reducing ion damage to the surface of the thin film during film formation. In addition, since the crystal grain boundaries and defects in the grains are easily passivated with hydrogen by increasing the pressure, it is possible to reduce the defect density of the crystalline silicon-based thin film due to them. More preferably, the pressure in the reaction vessel 1 is 5 to 20 Torr.
[0044]
As the silane-based gas, for example, monosilane, disilane, and the like are preferable, but in addition to these, a halogenated silicon gas such as silicon tetrafluoride, silicon tetrachloride, or dichlorosilane may be used. In addition to such a silane-based gas, an inert gas such as a rare gas, preferably helium, neon, argon, or the like may be used.
[0045]
In the film forming step, it is preferable that the flow rate ratio of hydrogen gas to silane-based gas contained in all reaction gases (including silane-based gas and hydrogen gas) introduced into the reaction vessel 1 is 100 times or more. In this way, by increasing the flow ratio of hydrogen gas to silane-based gas contained in the total reaction gas by 100 times or more, crystalline silicon that is easily peeled off at a low quality due to the etching action of activated hydrogen, etc. Therefore, it is possible to prevent the film from being deposited on the region other than the film deposition part.
[0046]
In the film forming step, the plasma discharge power density is 100 mW / cm.²It is preferable to make it above.
[0047]
Using such a plasma CVD apparatus shown in FIGS. 1 to 4, a reaction gas containing a silane-based gas and hydrogen gas is supplied from a gas supply pipe 7 into a cathode support member 8 having a bottomed rectangular frame shape, and the cathode As shown in FIG. 4, through a plurality of gas introduction holes 12 of the electrode 9, the gas is blown into a gas blowing hole 10 set to an appropriate size (dimension) in relation to the distance of the plasma sheath 11. By applying power, as described above, the weak plasma 15 between the cathode electrode 9 and the substrate 14 (101).₁At the same time, strong plasma 15 is generated near the opening of the gas blowing hole 10 of the cathode electrode 9 by the holocathode effect.₂Therefore, a high-quality crystalline silicon-based thin-film photoelectric conversion layer having a uniform film thickness and film quality over the entire surface of the one-conductivity-type semiconductor substrate 14 (101) held by the anode electrode 3 can be obtained. The film can be formed at a high speed.
[0048]
In addition, due to the improvement of the film formation speed described above, the crystalline nucleation density is relatively reduced because the crystal nucleation time is short in the initial stage of film growth, and the crystalline silicon thin film has large grains and strongly oriented crystal grains. Can be formed.
[0049]
Specifically, the crystalline silicon-based thin film photoelectric conversion layer 105 is grown such that many of the crystal grains contained therein extend upward from the one-conductivity-type semiconductor layer (underlayer) 104 in a columnar shape. Many of these crystal grains have a (110) preferential crystal orientation plane parallel to the film surface, and the intensity ratio of the (111) diffraction peak to the (220) diffraction peak determined by X-ray diffraction is 2/5 or less. More preferably, it is 1/10 or less.
[0050]
Furthermore, by setting the temperature of the silicon deposition part (one-conductivity-type semiconductor layer) of the substrate to 100 to 400 ° C. in the film forming step, a polycrystal containing hydrogen of 0.1 atomic% to 20 atomic% It becomes possible to form a crystalline silicon-based thin film photoelectric conversion layer made of silicon or microcrystalline silicon having a volume crystallization fraction of 80% or more.
[0051]
The crystalline silicon thin film photoelectric conversion layer preferably has a thickness of 0.5 to 10 μm.
[0052]
Further, even when the surface shape of the one-conductivity-type layer 104 that is the base layer is substantially flat, the surface after the formation of the photoelectric conversion layer 105 is finely spaced with an order of magnitude smaller than its film thickness. A surface texture structure having irregularities is formed.
[0053]
3) Reverse conductivity type semiconductor layer 106
As the reverse conductivity type semiconductor layer 106, for example, a p-type silicon thin film doped with 0.01 atomic% or more of boron, which is a conductivity determining impurity atom, or an n-type silicon thin film doped with 0.01 atomic% or more of phosphorus. Etc. can be used. However, these conditions for the reverse conductivity type semiconductor layer 106 are not limited. As the impurity atoms, for example, aluminum may be used in p-type silicon, or a film of an alloy material such as silicon carbide or silicon germanium may be used. The reverse conducting electrode silicon thin film 106 may be polycrystalline, microcrystalline, or amorphous, and its film thickness is set in the range of 3 to 100 nm, more preferably in the range of 5 to 50 nm. The
[0054]
(Third step)
Next, a transparent conductive oxide film 107 and a comb-shaped metal electrode 108 are sequentially formed on the photoelectric conversion unit 111 to manufacture a photoelectric conversion device having a structure shown in FIG.
[0055]
The transparent conductive oxide film 107 is made of, for example, ITO or SnO.₂, ZnO, or the like.
[0056]
The comb-shaped metal electrode 108 (grid electrode) is formed by patterning a layer of at least one metal selected from Al, Ag, Au, Cu, Pt, or the like, or an alloy thereof. These metal or alloy layers are formed by sputtering or vapor deposition, for example.
[0057]
In the photoelectric conversion device shown in FIG. 5 manufactured by such a method, the light 109 is incident on the transparent conductive oxide film 107 to be subjected to photoelectric conversion, and for example, the metal thin film 102 and the metal electrode 108 of the back electrode 110. Is output between the terminals.
[0058]
FIG. 5 illustrates only one silicon-based thin film photoelectric conversion device, and the present invention is added to at least one crystalline thin film photoelectric conversion unit including the silicon crystalline photoelectric conversion layer shown in FIG. Also applied to a tandem photoelectric conversion device that includes an amorphous thin film photoelectric conversion unit formed by a known method or at least one other amorphous thin film photoelectric conversion unit including an amorphous photoelectric conversion layer Is possible.
[0059]
Further, the present invention can be applied not only to nips but also to pin-type photoelectric conversion devices.
[0060]
According to the present invention described above, since a silicon-based photoelectric conversion layer that improves throughput can be formed with high quality in a series of manufacturing steps of a silicon-based thin film photoelectric conversion device, the silicon-based thin film photoelectric conversion device Can greatly contribute to higher performance and lower cost.
[0061]
【Example】
Hereinafter, a preferred embodiment according to the present invention will be described in detail in comparison with a reference example.
[0062]
(Reference Example 1)
Similar to the embodiment of FIG. 5 described above, a crystalline silicon thin film solar cell as Reference Example 1 was manufactured.
[0063]
First, an Ag film 102 having a thickness of 300 nm and a ZnO film 103 having a thickness of 100 nm were sequentially formed as a back electrode 110 on a glass substrate 101 having a length of 126 mm, a width of 126 mm, and a thickness of 1.1 mm by a sputtering method. An n-type microcrystalline silicon layer 104 phosphorus-doped with a thickness of 10 nm, a non-doped polycrystalline silicon thin film photoelectric conversion layer 105 with a thickness of 3 μm, and a p-type microcrystalline silicon layer 106 with a thickness of 10 nm and boron-doped on the back electrode 110. Each was formed into a film by plasma CVD method, and the nip photoelectric conversion unit 111 was formed. A transparent conductive ITO film having a thickness of 80 nm was deposited as a front electrode 107 on the photoelectric conversion unit 111 by a sputtering method, and a comb-shaped Ag electrode 108 for current extraction was formed thereon by a vapor deposition method and a patterning technique.
[0064]
The n-type microcrystalline silicon layer 104 was deposited by RF plasma CVD. The flow rates of the reaction gas used at this time were 5.0 sccm for silane, 200 sccm for hydrogen, and 0.05 sccm for phosphine. The pressure in the reaction vessel is 1 Torr, and the RF power density is 30 mW / cm.²Set to.
[0065]
The photoelectric conversion layer 105 was formed by a plasma CVD method under a substrate temperature of 400 ° C. and a pressure in the reaction vessel of 5 Torr. The cathode electrode used at this time was a gas blowing hole having a diameter of 1.5 mm communicating with the gas introduction hole having a diameter of 0.5 mm on the surface facing the anode electrode (in the vicinity of the inner peripheral surface of the hole under the discharge conditions during film formation). (Corresponding to 1.5 times the distance of the plasma sheath to be formed) has a gas blowing plate drilled at intervals of 4.0 mm. The distance between the cathode electrode and the anode electrode holding the substrate was set to 1.5 cm. In the reaction gas blown from the gas blowing hole of the cathode electrode, the flow rate ratio of silane / hydrogen is 1/18, and the discharge power is 80 mW / cm.²Set to.
[0066]
Under such conditions, the deposition rate of the photoelectric conversion layer 105 was 1.15 μm / h.
[0067]
In plasma CVD of the p-type microcrystalline silicon layer 106, the flow rates of the reaction gas were 1.0 sccm for silane, 500 sccm for hydrogen, and 0.01 sccm for diborane. The pressure in the reaction vessel is 1 Torr, and the RF power density is 150 mW / cm.²Set to.
[0068]
In the solar cell of Reference Example 1 obtained in this way, AM1.5 light was 100 mW / cm as the incident light 109 shown in FIG.²The output characteristics when irradiating with the amount of light were examined. As a result, the open circuit voltage is 0.357 V and the short circuit current density is 10.2 mA / cm.²The fill factor was 56.1% and the conversion efficiency was 2.0%. In the solar cell having the photoelectric conversion layer 105 formed as described above, the output characteristics are deteriorated because the diameter of the gas blowing hole formed in the gas blowing plate of the cathode electrode is under the discharge condition at the time of film formation. The distance is less than twice the distance of the plasma sheath formed in the vicinity of the inner peripheral surface of the hole, and plasma is not generated by the holocathode effect in these gas blowing holes, and plasma is mainly generated between the cathode electrode and the anode electrode (substrate). It is to be done.
[0069]
(Reference Example 2)
A gas blowing hole having a diameter of 15 mm that communicates with the gas introduction hole having a diameter of 0.5 mm on the surface facing the anode electrode of the photoelectric conversion layer 105 (a plasma sheath formed near the inner peripheral surface of the hole under the discharge conditions during film formation). A solar cell is manufactured under the same conditions as in Reference Example 1 except that the film is formed using a plasma CVD apparatus having a cathode electrode having a gas blowing plate perforated at an interval of 20 mm (equivalent to 15 times the distance). did.
[0070]
Under such conditions, the film formation rate of the photoelectric conversion layer 105 was 1.3 μm / h.
[0071]
In the solar cell of this reference example 2, AM1.5 light is 100 mW / cm as the incident light 109 shown in FIG.²The output characteristics when irradiating with the amount of light were examined. As a result, the open circuit voltage is 0.401 V and the short circuit current density is 12.3 mA / cm.²The fill factor was 60.1% and the conversion efficiency was 3.1%. In the solar cell having the photoelectric conversion layer 105 formed as described above, the output characteristics are deteriorated because the diameter of the gas blowing hole formed in the gas blowing plate of the cathode electrode is under the discharge condition at the time of film formation. More than 12 times the distance of the plasma sheath formed near the inner peripheral surface of the hole, the diameter of the gas blowing hole is increased, and the number of gas blowing holes that can be drilled in the gas blowing plate is reduced, so that the inside of the holocathode and the anode This is because the repetition interval of the parallel portion with the substrate held by the electrode is increased, the plasma becomes strong and undulated, and the plasma becomes unstable.
[0072]
Example 1
A gas blowing hole having a diameter of 4.0 mm communicating with the gas introduction hole having a diameter of 0.5 mm on the surface facing the anode electrode of the photoelectric conversion layer 105 (plasma formed in the vicinity of the inner peripheral surface of the hole under discharge conditions during film formation) The film was formed using the above-described plasma CVD apparatus having the structure shown in FIGS. 1 to 4 provided with the cathode electrodes having an interval of 5 mm (corresponding to four times the distance of the sheath).
[0073]
Under such conditions, the film formation rate of the photoelectric conversion layer 105 was 2.1 μm / h.
[0074]
In the solar cell of this Example 1, AM1.5 light is 100 mW / cm as the incident light 109 shown in FIG.²The output characteristics when irradiating with the amount of light were examined. As a result, the open circuit voltage is 0.529 V, and the short circuit current density is 23.8 mA / cm.²The curve factor was 72.1% and the conversion efficiency was 9.1%. Therefore, a plasma CVD apparatus provided with a cathode electrode in which the diameter of the gas blowing hole is set to be more than twice the distance of the plasma sheath formed in the vicinity of the inner peripheral surface of the hole under the discharge conditions during film formation and not more than 12 times It can be seen that the solar cell of Example 1 having the photoelectric conversion layer formed using the film can improve the photoelectric conversion characteristics as compared with those of Reference Examples 1 and 2.
[0075]
【The invention's effect】
As described above in detail, according to the present invention, a more stable plasma can be generated and a thin film having a uniform film thickness and film quality can be formed at a high speed, and film formation of a photovoltaic cell photoelectric conversion device, a liquid crystal display device, etc. It is possible to provide a plasma CVD apparatus that can be effectively applied to the above.
[0076]
According to the present invention, when a photoelectric conversion unit having a silicon-based photoelectric conversion layer is stacked, a high-quality silicon-based photoelectric conversion layer having a uniform film thickness and film quality is formed using the plasma CVD apparatus. A method of manufacturing a silicon-based thin film photoelectric conversion device that achieves improved performance can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a plasma CVD apparatus according to the present invention.
2 is a cross-sectional view of the main part of the plasma CVD apparatus in FIG. 1;
3 is a view taken in the direction of arrows III-III in FIG.
4 is an enlarged cross-sectional view of a gas blowing plate having a gas blowing hole of the hollow cathode electrode of FIG.
FIG. 5 is a perspective view schematically showing a silicon-based thin film photoelectric conversion device manufactured according to one embodiment of the present invention.
[Explanation of symbols]
1 ... reaction vessel,
2 ... exhaust pipe,
3 ... anode electrode,
9 ... cathode electrode,
10: Gas blowout hole,
11 ... Plasma sheath,
12 ... Gas introduction hole,
14 ... substrate,
15₁, 15₂…plasma,
102 ... A thin film such as Ag,
103 ... Thin film such as ZnO
104 ... one conductivity type semiconductor layer,
105 ... crystalline silicon photoelectric conversion layer,
106 ... Reverse conductivity type semiconductor layer,
107: Transparent conductive film such as ITO,
110 ... back electrode,
111 ... A crystalline silicon photoelectric conversion unit.

Claims (1)

The photoelectric conversion unit includes at least one photoelectric conversion unit formed on a substrate, the photoelectric conversion unit being sequentially stacked by a plasma CVD method, at least one silicon-based thin film photoelectric conversion layer, and a reverse conductivity type semiconductor. A method for manufacturing a silicon-based thin film photoelectric conversion device including a layer,
A reaction container having an exhaust member; an anode electrode disposed in the reaction container; a holo cathode type cathode electrode disposed in the reaction container opposite to the anode electrode; and a reaction gas for the cathode electrode A gas supply means for supplying power and a power source for applying power to the cathode electrode, wherein the cathode electrode has a plurality of gas blowing holes on the front surface facing the anode electrode, and the back surfaces of these holes; A gas introduction hole having a diameter smaller than that of the hole formed so as to communicate with these holes in a portion, and the diameter of each gas blowing hole is in the vicinity of the inner peripheral surface of the hole under discharge conditions during film formation Providing a plasma CVD apparatus that is more than twice the distance of the formed plasma sheath and less than or equal to 12 times;
Holding the substrate on which the one-conductivity-type semiconductor layer is formed on the anode electrode in the reaction vessel of the plasma CVD apparatus;
Power is supplied from the power source to the cathode electrode, and a reactive gas containing silane-based gas and hydrogen gas is blown out from the gas blowing hole through the plurality of gas introduction holes, and plasma is mainly generated in the vicinity of the gas blowing hole by the holo cathode effect. Forming a silicon-based thin film photoelectric conversion layer on the one-conductivity-type semiconductor layer of the substrate by generating
Including
A method for producing a silicon-based thin film photoelectric conversion device, wherein the substrate temperature during film formation is set to 100 to 400 ° C., and the pressure in the reaction vessel is set to 5 Torr or more.

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