JP2013030664A - Manufacturing method of semiconductor device using plasma CVD apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of preventing a deposition film from mixing in a semiconductor thin film by preventing peeling of the film deposited when performing temporal film forming after cleaning a film forming chamber, related to a method of manufacturing a semiconductor device using a plasma CVD apparatus.SOLUTION: In the method of manufacturing a semiconductor device using a plasma CVD apparatus, a crystalline silicon thin film is used at the time of temporary film forming. It is possible to prevent a deposition film from being taken into a semiconductor thin film by using the crystalline silicon thin film at the time of temporary film forming.

Description

  The present invention relates to the manufacture of a semiconductor device using a plasma CVD apparatus, and more particularly to a film forming method for reducing peeling of a deposited film during temporary film formation after cleaning.

  When film formation is performed using a plasma CVD (Chemical Vapor Deposition) apparatus, a film is deposited on the inner surface of the film formation chamber in addition to the substrate on which the thin film is formed. As deposition on the inner surface of the film forming chamber progresses, the thickened film may peel off and be mixed into the thin film during film formation. The inclusion of the deposited film becomes one of the causes of deterioration of the film quality of the film formed on the substrate.

  Therefore, in a production line including a step of forming a film using a plasma CVD apparatus, cleaning for removing the deposited film on the inner surface of the film forming chamber is periodically performed in order to prevent mixing of the deposited film.

  When cleaning is performed using a plasma etching gas as a cleaning method, a reaction product due to etching may remain in the film forming chamber. Further, when cleaning by physical removal is performed, it is necessary to open the film forming chamber to the atmosphere, so moisture in the atmosphere remains. If etching gas, moisture, or the like remains in the film forming chamber, stable film formation becomes difficult. Therefore, there is a method of performing temporary film formation after cleaning. This is because cleaning of the film forming chamber by plasma discharge and attaching a film to the inner surface of the film forming chamber can suppress the emission of impurities from the inner surface of the film forming chamber.

  In Patent Document 1, as a method for preventing the deposition film from being mixed, the coating material is plasma sprayed on the plasma exposure surface of the reaction chamber to prevent the deposition film from being mixed, and has a desired surface roughness characteristic. A method of forming a coating is disclosed. The formed coating has a surface roughness value (Ra) suitable for achieving improved adhesion. It is disclosed that by improving the adhesion of the deposit on the chamber surface, the tendency of the deposit to peel off or peel off on the chamber surface can be suppressed.

JP 2010-199596 A

  However, when the method described in Patent Document 1 is used, it is necessary to perform plasma spraying inside the film forming chamber, so that a plasma spraying device different from the plasma CVD device is required.

  On the other hand, it has been found that when a temporary film is formed using a film-forming gas after the plasma CVD apparatus is cleaned, the deposited film is peeled off even if the film is not thickened.

The present invention has been made in view of the above problems, and an object of the present invention relates to a method of manufacturing a semiconductor device using a plasma CVD apparatus, and a film deposited when a temporary film is formed after the film forming chamber is cleaned. The purpose of this is to prevent the deposition of the deposited film in the semiconductor thin film.

  A method of manufacturing a semiconductor device using a plasma CVD apparatus according to the present invention includes: a cleaning process for cleaning a film forming chamber inside the plasma CVD apparatus; and a temporary film formation of a crystalline silicon thin film in the film forming chamber after the cleaning process. The provisional film forming process includes a semiconductor thin film forming process for forming a laminated film of semiconductor thin films in the film forming chamber after the temporary film forming process.

  A method for manufacturing a semiconductor device according to the present invention includes a cleaning process for cleaning a film forming chamber inside a plasma CVD apparatus, and a temporary film forming process for performing a temporary film formation of a crystalline silicon thin film in the film forming chamber after the cleaning process. A semiconductor thin film forming step for forming a laminated film of semiconductor thin films in the film forming chamber after the temporary film forming step is provided.

  A semiconductor device according to the present invention is a photoelectric conversion element.

  The semiconductor thin film deposition process according to the present invention includes a process of depositing an amorphous silicon semiconductor thin film.

  The temporary film forming step according to the present invention is characterized in that a film having a film thickness of 250 nm or more and 4 μm or less is formed.

  The semiconductor thin film forming step according to the present invention is a step of forming a photoelectric conversion element having a laminated structure, and the photoelectric conversion element is a stacked photoelectric conversion element composed of a first structure and a second structure. Features.

  The stacked photoelectric conversion element according to the present invention is characterized by having an intermediate layer between the first structure and the second structure.

The intermediate layer according to the present invention is characterized by comprising ZnO.

The method of manufacturing a semiconductor device using the plasma CVD apparatus according to the present invention has an effect of preventing peeling of a film deposited when a temporary film is formed after cleaning, and preventing a deposited film from being mixed into the semiconductor thin film. Play.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram illustrating a configuration of a plasma CVD apparatus according to a first embodiment of the present invention. 1 is a cross-sectional view illustrating a structure of a photoelectric conversion element according to a first embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a first embodiment of the present invention and is a flowchart illustrating a method for forming a semiconductor thin film. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the 1st Embodiment of this invention and compares the conversion efficiency of a photoelectric conversion element. The 2nd Embodiment of this invention is shown, Comprising: It is sectional drawing which shows the structure of a laminated photoelectric conversion element. 2 shows a second embodiment of the present invention, and shows the number of times of film formation and conversion efficiency when a crystalline silicon thin film is used for temporary film formation. FIG. The comparative example in the 2nd Embodiment of this invention is shown, Comprising: When an amorphous silicon thin film is used for temporary film formation, the frequency | count of film forming and conversion efficiency are shown.

  The present inventor further examined the problem that the deposited film formed during the temporary film formation peels, and there is a problem in the adhesion between the film deposited by the temporary film formation and the inner surface of the film formation chamber. I found out. The present invention solves the problem that a deposited film is peeled off when a temporary film is formed after cleaning, and the deposited film is mixed into a semiconductor thin film constituting a photoelectric conversion element.

  In the present application, the inner surface of the film forming chamber includes an inner wall of the film forming chamber and a component surface in the film forming chamber. A semiconductor thin film refers to a film formed using a plasma CVD apparatus, and a photoelectric conversion element refers to an element having a structure in which a semiconductor thin film is sandwiched between electrodes.

  Further, the crystalline silicon thin film includes a so-called microcrystalline silicon thin film, a microcrystalline silicon thin film, or a thin film in which a microcrystalline silicon thin film and an amorphous silicon thin film are mixed. Temporary film formation includes so-called pre-deposition.

(First embodiment)
A method for manufacturing a photoelectric conversion element using the plasma CVD apparatus according to the first embodiment will be described below with reference to the drawings.

  First, the plasma CVD apparatus will be described with reference to FIG. 1, the structure of the photoelectric conversion element will be described with reference to FIG. 2, and the semiconductor thin film forming process constituting the photoelectric conversion element will be described with reference to FIG. explain.

  FIG. 1 is a diagram showing a configuration of a plasma CVD apparatus according to the present invention. The plasma CVD apparatus includes a film forming chamber 1, a gas supply unit such as a gas supply unit 4 and a gas pipe 5, a power supply unit such as an AC power supply 7 and a matching circuit 8, and an exhaust system such as an exhaust pipe 9 and a vacuum pump 10. included. In the film forming chamber 1, an electrode pair composed of a cathode electrode 2 and an anode electrode 3 is disposed.

  The film forming chamber 1 is a space for performing plasma processing, and the degree of vacuum in the film forming chamber is adjusted by being exhausted through an exhaust pipe 9 connected to the film forming chamber 1. Thereby, the inside of the film forming chamber 1 can be maintained at a pressure equal to or lower than the atmospheric pressure.

  The cathode electrode 2 includes a shower plate 21 and a base material 22. In the shower plate 21, a plurality of gas supply holes 6 serving as gas flow paths are formed in a strip-shaped plate. The cathode electrode 2 is connected to an AC power source 7 through a matching circuit 8. The AC power source 7 supplies AC power between the cathode electrode 2 and the anode electrode 3, and is, for example, an RF (Radio Frequency) power source.

  A substrate 11 is placed on the anode electrode 3, and a heater 12 for heating the substrate 11 is provided in the anode electrode. Electric power is supplied to the heater 12 from a heater power supply 13. As a material for the cathode electrode 2 and the anode electrode 3, an aluminum alloy that is difficult to be etched during cleaning was used. Stainless steel or carbon may be used.

The gas is uniformly supplied from a plurality of gas supply holes 6 between the cathode electrode 2 and the anode electrode 3 through the gas pipe 5 from the gas supply device 4. The gas supply device 4 supplies a process gas for film formation when film formation is performed in the film formation chamber 1 and supplies an etching gas when cleaning the film formation chamber 1. Further, in the gas supply device 4, gas flow rate adjustment and gas supply start / stop adjustment are performed. In this embodiment, a silicon-based gas such as silane is used as the process gas, and a fluorine-based gas such as NF ₃ is used as the etching gas.

  A film is formed on the substrate 11 by being discharged at the electrode pair of the cathode electrode 2 and the anode electrode 3 to generate plasma. When film formation is performed, a deposited film is also formed on the inner surface of the film formation chamber.

  Although FIG. 1 shows a plasma CVD apparatus in which the anode and the cathode are parallel to the ground, the anode and the cathode may be perpendicular to the ground. Alternatively, a plurality of sets of anodes and cathodes may be provided in the film forming chamber.

FIG. 2 is a cross-sectional view illustrating a structure of a single photoelectric conversion element according to this embodiment. A semiconductor in which a first electrode 32 is formed on a glass substrate 31, and a p-type amorphous silicon layer 33, an amorphous silicon photoelectric conversion layer 34, and an n-type amorphous silicon layer 35 are sequentially stacked thereon. A thin film is formed. Furthermore, the 2nd electrode 39 is formed on it and it is set as the photoelectric conversion element. As the first electrode 32, SnO ₂ was used as the transparent conductive film, and as the second electrode 39, a laminated film including a metal film made of ZnO and Ag was used.

  Next, the first embodiment will be specifically described using Example A1.

  FIG. 3 shows a flow chart of a process for forming a semiconductor thin film constituting the photoelectric conversion element. The photoelectric conversion element was manufactured by forming the first electrode 32 on the glass substrate 31, then forming a semiconductor thin film using a plasma CVD apparatus, and forming the second electrode 39. The electrode can be formed using a vapor deposition method, a sputtering method, or the like. In the present embodiment, the film is formed using a sputtering method. Below, the semiconductor thin film formation process using a plasma CVD apparatus is explained in full detail.

In the cleaning process S1 (S represents a step, the same applies hereinafter), the film forming chamber was cleaned. In the production line, when film formation is continuously performed using a plasma CVD apparatus, cleaning for removing the deposited film on the inner surface of the film formation chamber is periodically performed. In the present embodiment, cleaning is performed using a plasma etching gas. As an etching gas, a mixed gas of NF ₃ which is a reactive gas for performing reactive etching and a dilution gas for diluting the reactive gas was used. Fluorine radicals, which are etching reaction species, are generated by generating plasma with NF ₃ , which is a fluorine-based gas, introduced into the film forming chamber. By reacting the fluorine radicals with the silicon-based deposited film, the silicon-based deposited film is removed as a gas.

  As a cleaning method, the film forming chamber may be opened to the atmosphere, and the film adhering to the inner surface of the film forming chamber may be physically removed. Components such as electrodes, which are greatly affected by the deposited film, may be chemically removed separately using an acid or alkali chemical solution.

  Then, in temporary film-forming process S2, the dummy substrate was mounted on the cathode electrode of the plasma CVD apparatus, and temporary film-forming was performed using the film-forming gas. The dummy substrate refers to a substrate used in the temporary film forming process, and can be used repeatedly. In the present embodiment, a glass substrate is used as the dummy substrate, but a metal substrate such as stainless steel can also be used.

  Impurities remaining in the film forming chamber in the cleaning step S1 can be cleaned by the plasma discharge during the temporary film formation. By depositing a film on the surface of the component in which the residual gas in the film forming chamber tends to stay, it becomes possible to suppress the release of impurities from the inner surface of the film forming chamber.

As Example A1, a temporary film formation of a crystalline silicon thin film was performed. As the mixed gas, a gas containing silane gas and hydrogen gas was used. The flow rate ratio of hydrogen gas to silane gas was about 100 times, the pressure in the film formation chamber during film formation was 900 Pa, and the power density was 0.15 W / cm ² .

  If the flow ratio of hydrogen gas to silane gas is reduced, the deposition rate of the crystalline silicon thin film can be increased, but the plasma discharge becomes unstable. When the flow rate ratio is increased, the plasma discharge is stabilized, but the film forming speed is decreased. In order to perform temporary film formation while maintaining an appropriate film formation speed under a stable plasma discharge, the flow rate ratio is desirably 30 times to 100 times.

Incidentally, the measured peak intensity ratio _I 520 _{/ I 480} of the peak at 520 nm ^-1 to a peak at 480 nm ^-1 as measured by Raman spectroscopy, was about 5. It was confirmed that the film had a good crystallization rate and a crystalline silicon thin film was formed instead of an amorphous silicon thin film.

  The film thickness to be temporarily formed was set to be about 1 μm. The film thickness is desirably 250 nm to 4 μm. If the film thickness is too thin, the release of impurities from the inner surface of the film forming chamber cannot be suppressed. In addition, if the film thickness to be temporarily formed is too thick, the deposited film on the inner surface of the film forming chamber due to subsequent film formation will quickly increase, and the period until the next cleaning will be shortened. This is because it is not preferable for use in a production line or the like. More desirably, the film thickness is 800 nm to 2 μm. Since the inner surface of the film forming chamber can be almost completely covered and is not thickened more than necessary, it is possible to prevent waste of film forming gas, film forming time and the like. After the temporary film formation, the dummy substrate was unloaded.

  Thereafter, in the semiconductor thin film forming step S3, a semiconductor thin film formed by sequentially stacking the p-type amorphous silicon layer 33, the i-type amorphous silicon layer 34, and the n-type amorphous silicon layer 35 is formed. A single-type photoelectric conversion element of amorphous silicon described with reference to FIG. As the film forming apparatus, the plasma CVD apparatus described with reference to FIG. 1 was used. As the substrate, a glass substrate 31 on which the first electrode 32 was formed was used.

The p-type amorphous silicon layer 33 can be formed, for example, under the following film forming conditions. The pressure in the film forming chamber is desirably 200 Pa or more and 3000 Pa or less, and is set to 500 Pa in the present embodiment.
Power density per unit area of the cathode electrode is preferably set to be 0.01 W / cm ² or more 0.3 W / cm ² or less, in the present embodiment was 0.1 W / cm ^2. As the mixed gas introduced into the film forming chamber, for example, a gas containing silane, hydrogen, and diborane can be used. The flow rate ratio of hydrogen gas to silane gas is preferably about 5 to 30 times, and is 10 times in this embodiment. The thickness of the p-type amorphous layer 33 is desirably 2 nm or more and 50 nm or less, and is 10 nm in the present embodiment.

The i-type amorphous silicon layer 34 can be formed, for example, under the following film forming conditions. The pressure in the film forming chamber, the power density, and the flow rate ratio of the hydrogen gas to the silane gas are the same as those of the p-type amorphous silicon layer 33, and a gas containing silane gas and hydrogen gas is used as the mixed gas introduced into the film forming chamber. did. Further, the thickness of the i-type amorphous silicon layer 34 is preferably 100 nm or more and 500 nm or less, and is 320 nm in this embodiment.
As the i-type amorphous silicon layer 34, an i-type amorphous silicon thin film or a weak p-type or weak n-type silicon thin film containing a small amount of impurities and having a sufficient photoelectric conversion function may be used. A laminate of these thin films may also be used.

  The n-type amorphous silicon layer 35 can be formed, for example, under the following film forming conditions. The pressure in the film forming chamber, the power density, and the flow rate ratio of hydrogen gas to silane gas are the same as those of the p-type amorphous silicon layer 33, and a gas containing silane, hydrogen, and phosphine is used as a mixed gas introduced into the film forming chamber. used. The thickness of the n-type amorphous silicon layer 35 is preferably 2 nm or more and 50 nm or less, and is 20 nm in this embodiment.

  After the semiconductor thin film was formed, the substrate was taken out. When the second electrode layer 39 is formed thereon, a photoelectric conversion element is formed.

  The p-type amorphous silicon layer 33, the i-type amorphous silicon layer 34, and the n-type amorphous silicon layer 35 may be formed of a layer made of an alloy material such as silicon carbide or silicon germanium. Moreover, what laminated | stacked several different thin films may be used.

  The p-type amorphous silicon layer 33, the i-type amorphous silicon layer 34, and the n-type amorphous silicon layer 35 were successively formed in the same film forming chamber. Since it is not necessary to take the substrate in and out of the film forming chamber, the film forming time can be shortened. Furthermore, since a plurality of film forming chambers are not required, there is an advantage that the plasma CVD apparatus can be downsized.

  Next, Comparative Example B1 will be described. The difference between Example A1 and Comparative Example B1 is whether the film formed in the temporary film forming process is a crystalline silicon thin film or an amorphous silicon thin film. Usually, when temporary film formation is performed, a film having a film formation condition close to that of the film formed after the temporary film formation is often formed. In the present embodiment, as shown in FIG. 2, a p-type amorphous silicon layer 33 is first formed. Therefore, a case where an amorphous silicon thin film is temporarily formed was used as a comparative example. In the flow chart of the film forming process of FIG. 3, the cleaning process S1 and the semiconductor thin film forming process S3 are the same as in Example A1.

As Comparative Example B1, an amorphous silicon thin film was temporarily formed in the temporary film forming step S2 of FIG. The flow rate ratio of hydrogen gas to silane gas was about 10 times, the pressure in the film formation chamber during film formation was 500 Pa, and the power density was 0.06 W / cm ² . The film thickness to be temporarily formed was set to be about 1 μm as in Example A1.

  Next, when the semiconductor thin films of Example A1 and Comparative Example B1 formed in the semiconductor thin film forming step S3 were compared using a bright field microscope, it was confirmed that there were portions with different absorptances in the surface. . The places where the absorption ratios were different were smaller in the semiconductor thin film of Example A1 than in Comparative Example B1. It is presumed that the portions having different absorptances were taken into the semiconductor thin film because the deposited film on the inner surface of the film forming chamber was peeled off during the temporary film forming process.

  Therefore, a tape peeling test was performed in order to measure the adhesion between the crystalline silicon thin film temporarily formed in Example A1 and the amorphous silicon thin film temporarily formed in Comparative Example B1. The tape peeling test performed here is a test for examining how much the film is peeled off by sticking a sticky tape on the film surface and peeling it strongly in the direction of 180 ° C. from the film surface. On the cathode, a stainless steel substrate, which is the same material as the wall of the film forming chamber, was placed as a substrate, and a crystalline silicon thin film and an amorphous silicon thin film were formed respectively. The film thickness was set to 300 nm using the same film forming conditions as in the temporary film forming step S2 of Example A1 and Comparative Example B1. After film formation, a tape test was performed. As the tape, Kapton tape (registered trademark of EI DuPont de Nemours and Company) was used. When the tape was visually inspected after the tape test, the amorphous silicon thin film was adhered to the tape. On the other hand, no film was observed in the crystalline silicon thin film, and it was confirmed that the crystalline silicon thin film has higher adhesion.

  Compared with the amorphous silicon thin film, the crystalline silicon thin film took about 1/3 of the time required to form the same film thickness. One of the reasons why the film formation speed is high is that the amorphous silicon thin film is formed by a pulse wave, whereas the crystalline silicon thin film is formed by a continuous wave.

  One of the reasons for the high film forming speed is that an amorphous silicon thin film needs to be formed with a pulse wave, whereas a crystalline silicon thin film can be formed with a continuous wave. Therefore, when the same film thickness is formed, the crystalline silicon thin film can be formed in a shorter film forming time. In addition, when film formation is performed for the same film formation time, the amorphous silicon thin film can be made thicker. In the temporary film forming step S2, by increasing the film thickness attached to the inner surface of the film forming chamber, it is possible to obtain an effect of suppressing the release of impurities from the inner surface of the film forming chamber.

  The semiconductor thin film forming process described with reference to FIG. 3 does not necessarily repeat the cleaning process S1, the temporary film forming process S2, and the semiconductor thin film forming process S3, and the cleaning process S1 and the temporary film forming process. After S2, only the semiconductor thin film forming step S3 may be repeated.

  Further, during the cleaning process S1, the temporary film forming process S2, and the semiconductor thin film forming process S3, a process for stabilizing the film forming chamber such as a nitrogen purge in the film forming chamber or a hydrogen plasma process may be performed. .

  Next, Example A2 and Comparative Example B2 will be described.

  A crystalline photoelectric conversion element in which a film formed in the semiconductor thin film forming step S3 is a p-type crystalline silicon layer, an i-type crystalline silicon layer, and an n-type crystalline silicon layer is manufactured, and the same comparison as above is performed. Went. The film thicknesses were 40 nm, 2 μm, and 40 nm, respectively. As Example A2, the crystalline silicon thin film was provisionally formed in the provisional film formation step S2, and then the crystalline silicon photoelectric conversion element was prepared in the semiconductor thin film formation step S3. Furthermore, after the amorphous silicon thin film was temporarily formed as Comparative Example B2 in the temporary film forming step S2, the crystalline silicon photoelectric conversion element was manufactured in the semiconductor thin film forming step S3. When compared using a bright field microscope, Example A2 had less foreign matter in the film than Comparative Example B2.

FIG. 4 shows the conversion efficiency ratios of Example A1, Example A2, Comparative Example B1, and Comparative Example B2. All produced 5 samples and took the average value of conversion efficiency. The values of Example A1 and Example A2 are shown as ratios when the conversion efficiencies of Comparative Example B1 and Comparative Example B2 are 100, respectively.
Since the value of Example A1 is larger than that of Example B1, the crystalline silicon photoelectric conversion element was formed when the amorphous silicon photoelectric conversion element was formed in the semiconductor thin film formation step S3. It was found that the conversion efficiency was greatly improved compared to the case. This is presumed to be because the amorphous silicon photoelectric conversion element has a thin semiconductor thin film, so that leakage due to foreign matter in the film is likely to occur, and the influence on the conversion efficiency is increased.

  In this embodiment mode, a method for manufacturing a photoelectric conversion element has been described. However, the present invention can be applied to manufacturing various semiconductor devices such as a thin film transistor.

(Second Embodiment)
As a second embodiment, a case where a stacked photoelectric conversion element is formed in a semiconductor thin film forming step will be described below.

FIG. 5 is a cross-sectional view showing the structure of the stacked photoelectric conversion element according to this embodiment. A first electrode 32 is formed on a glass substrate 31, and a p-type amorphous silicon layer 33, an i-type amorphous silicon layer 34, and an n-type amorphous silicon layer 35 are sequentially stacked thereon. A 1-pin structure laminate 41 is formed. Subsequently, a second pin structure laminate 42 in which a p-type crystalline silicon layer 36, an i-type crystalline silicon layer 37, and an n-type crystalline silicon layer 38 are sequentially laminated was formed. Further, a second electrode 39 is formed thereon to form a stacked photoelectric conversion element. As the first electrode 32, SnO ₂ was used as the transparent conductive film, and as the second electrode 39, a laminated film including a metal film made of ZnO and Ag was used.

  Next, a method for forming the first pin structure stacked body 41 of the stacked photoelectric conversion element shown in FIG. 5 will be described in detail. As the film forming apparatus, the plasma CVD apparatus described with reference to FIG. 1 was used.

  The film forming conditions of the p-type amorphous silicon layer 33, the i-type amorphous silicon layer 34, and the n-type amorphous silicon layer 35 are the single-type amorphous silicon photoelectric conversion described in the first embodiment. It is the same as the element. The p-type amorphous silicon layer 33, the i-type amorphous silicon layer 34, and the n-type amorphous silicon layer 35 were continuously formed in the same film forming chamber.

  Next, a method for forming the second pin structure stacked body 42 of the stacked photoelectric conversion element will be described in detail.

The p-type crystalline silicon layer 36 can be formed, for example, under the following film forming conditions. The pressure in the film forming chamber is desirably 240 Pa or more and 3600 Pa or less, and is set to 800 Pa in the present embodiment. Power density per unit area of the cathode electrode is preferably set to be 0.01 W / cm ² or more 0.5 W / cm ² or less, in the present embodiment was 0.15 W / cm ^2. The flow rate ratio of hydrogen gas to silane gas is preferably about 100 to 300 times, and 200 times in this embodiment. The mixed gas introduced into the film forming chamber and the thickness of the p-type crystalline silicon layer 36 are the same as those of the p-type amorphous silicon layer 33.

The i-type crystalline silicon layer 37 can be formed, for example, under the following film forming conditions. The pressure in the film forming chamber is desirably 240 Pa or more and 3600 Pa or less, and is 1600 Pa in the present embodiment. Power density is preferably set to be 0.02 W / cm ² or more 0.5 W / cm ² or less, in the present embodiment was 0.15 W / cm ^2. The flow rate ratio of hydrogen gas to silane gas is preferably about 30 to 100 times, and in this embodiment, 80 times. The thickness of the i-type crystalline silicon layer 37 is preferably 0.5 μm or more and 20 μm or less, and 2 μm in this embodiment. The kind of mixed gas introduced into the film forming chamber is the same as that of the amorphous silicon photoelectric conversion layer 34. As the i-type crystalline silicon layer 37, an i-type crystalline silicon thin film or a silicon thin film having a weak p-type or weak n-type containing a small amount of impurities and sufficiently having a photoelectric conversion function may be used. The thin film may be laminated.

  The n-type crystalline silicon layer 38 can be formed, for example, under the following film forming conditions. The pressure in the deposition chamber, the power density, the flow rate ratio of hydrogen gas to silane gas, and the thickness are the same as those of the n-type amorphous silicon layer 35. A gas containing silane, hydrogen, and phosphine was used as a mixed gas.

  The p-type crystalline silicon layer 36, the crystalline silicon photoelectric conversion layer 37, and the n-type crystalline silicon layer 38 were continuously formed in the same film forming chamber.

  Next, the second embodiment will be specifically described using Example A3 and Comparative Example B3. The difference between Example A3 and Comparative Example B3 is whether the film to be temporarily formed in the temporary film forming step S2 is a crystalline silicon thin film or an amorphous silicon thin film.

  The cleaning step S1 is the same as that described in the first embodiment.

  Then, in temporary film-forming process S2, a dummy substrate was put, Example A3 preliminarily formed the crystalline silicon thin film, and Comparative Example B3 preliminarily formed the amorphous silicon thin film. The respective film forming conditions and film thicknesses are the same as those in Example A1 and Comparative Example B1 in the first embodiment.

  Thereafter, in the semiconductor thin film forming step S3, the semiconductor thin film forming the stacked photoelectric conversion element of FIG. 5 was formed in both Example A3 and Comparative Example B3. A glass substrate on which the first electrode layer 32 was formed was used as the substrate. After the formation of the semiconductor thin film, the second electrode layer 39 was formed to obtain a stacked photoelectric conversion element, and the conversion efficiency was measured. By changing the substrate, the formation of the semiconductor thin film, the formation of the second electrode layer 39, and the measurement of the conversion efficiency were repeated.

  FIG. 6 shows the number of times of forming the semiconductor thin film of Example A3 and the conversion efficiency when the second electrode layer is formed to form a stacked photoelectric conversion element. FIG. 7 shows the semiconductor thin film of Comparative Example B3. The number of times of film formation and the conversion efficiency at that time are shown. The conversion efficiency is shown as a ratio with respect to the reference value with the reference value 100 when the value is almost stable. From FIG. 6 and FIG. 7, in Example A3, the conversion efficiency of the reference value is almost obtained by the fourth film formation, but in Comparative Example B3, it takes 9 times until the conversion efficiency of the reference value is obtained. I understand that. By comparing Example A3 with Comparative Example B3, the conversion efficiency of the reference value can be obtained by performing the temporary film formation of the crystalline silicon thin film instead of the amorphous silicon thin film in the temporary film formation step S2. It can be seen that the number of film formations required to be completed is small.

  In Comparative Example B3, when the semiconductor thin film formed from the first time to the ninth time was observed with an optical microscope, it was found that the film contained many foreign substances. The amorphous silicon thin film has lower adhesion to stainless steel, which is the main component of the film forming chamber, as compared to the crystalline silicon thin film. Therefore, it is considered that the film at the time of temporary film peeling from the constituent member was taken into the semiconductor thin film. Furthermore, analysis of each component of the conversion efficiency of the 3rd to 6th stacked photoelectric conversion elements in which a large number of foreign matters were confirmed showed that the open-circuit voltage (Voc) value was low, and foreign matter in the film caused It is estimated that a minute leak occurs between the first electrode and the second electrode.

  Note that although the case of a stacked photoelectric conversion element has been described in this embodiment mode, a triple photoelectric conversion element including first, second, and third pin structures may be used.

  Further, an intermediate layer may be inserted between each structure of the stacked photoelectric conversion element. Examples of the material for the intermediate layer include SiN, SiC, ZnO, and the like. The change in conversion efficiency due to the fact that the film to be temporarily formed in the provisional film forming step S2 is not a amorphous silicon thin film but a crystalline silicon thin film, greatly improved when the intermediate layer was inserted. In particular, when ZnO was used as the intermediate layer, a greater improvement was obtained. This is because, when there is a foreign object in the semiconductor thin film, the minute leak that occurs when the first electrode and the second electrode are connected also occurs when the first electrode intermediate layer and the second electrode and intermediate layer are connected. Therefore, it is presumed that it is easily affected by foreign matter.

  In this embodiment mode, a method for manufacturing a photoelectric conversion element has been described. However, the present invention can be applied to manufacturing various semiconductor devices such as a thin film transistor.

  Although specific description has been given above, the present invention is not limited to them. The same effect can be obtained for an integrated photoelectric conversion element that is integrated using a laser or the like. Further, embodiments obtained by appropriately combining the technical means disclosed in the above-described embodiments are also included in the technical scope of the present invention.

The method for manufacturing a semiconductor device according to the present invention can be widely applied to the manufacture of a semiconductor device using a plasma CVD apparatus.

DESCRIPTION OF SYMBOLS 1 Film forming room 2 Cathode electrode 21 Shower plate 22 Base material 3 Anode electrode 4 Gas supply device 5 Gas piping 6 Gas supply hole 7 AC power supply 8 Matching circuit 9 Exhaust piping 10 Vacuum pump 11 Substrate 12 Heater 13 Heater power supply 30 Substrate 31 Glass Substrate 32 First electrode 33 p-type amorphous silicon layer 34 i-type amorphous silicon layer 35 n-type amorphous silicon layer 36 p-type crystalline silicon layer 37 i-type crystalline silicon layer 38 n-type crystalline silicon layer 39 2nd electrode 41 1st pin structure laminated body 42 2nd pin structure laminated body

Claims (7)

A cleaning process for cleaning the inside of the film forming chamber of the plasma CVD apparatus;
After the cleaning step, a temporary film forming step of performing a temporary film formation of the crystalline silicon thin film in the film forming chamber;
A method for manufacturing a semiconductor device, comprising: a semiconductor thin film forming step of forming a laminated film of semiconductor thin films in the film forming chamber after the temporary film forming step.   The method of manufacturing a semiconductor device according to claim 1, wherein the semiconductor device is a photoelectric conversion element.   The semiconductor device manufacturing method according to claim 2, wherein the semiconductor thin film forming step includes a step of forming an amorphous silicon semiconductor thin film.   The method of manufacturing a semiconductor device according to claim 2, wherein the temporary film forming step forms a film having a thickness of 250 nm or more and 4 μm or less. The semiconductor thin film forming step is a step of forming a photoelectric conversion element having a laminated structure,
The method for manufacturing a semiconductor device according to claim 2, wherein the photoelectric conversion element is a stacked photoelectric conversion element including a first structure and a second structure.   The method of manufacturing a semiconductor device according to claim 5, wherein the stacked photoelectric conversion element has an intermediate layer between the first structure and the second structure.   The method for manufacturing a semiconductor device according to claim 6, wherein the intermediate layer is made of ZnO.