JP2012219288A - Thin film fabricating apparatus and thin film fabrication method - Google Patents

Abstract

A thin film capable of producing a thin film having good physical properties without generating new impurities, eliminating the influence of a reaction product remaining during a cleaning process without causing damage to the inside of the film forming chamber. To obtain manufacturing equipment.
A film forming chamber, a stage, a raw material gas supplying means for supplying a raw material gas into the film forming chamber, and a deposit adhered to the film forming chamber by forming a film react to react. A cleaning gas supply means for supplying a cleaning gas for generating a product into the film forming chamber 11 and a reaction product removing gas containing an element that generates a gas by reacting with a constituent element of the reaction product in the film forming chamber 11 The reaction product removal gas supply means for supplying the reaction product, the shower head 14 disposed opposite to the stage 12, and light sources 19a to 19c that emit light having energy capable of dissociating the reaction product and the reaction product removal gas. The light sources 19a to 19c are arranged so as to irradiate a region in the film forming chamber 11 to which deposits adhere.
[Selection] Figure 1

Description

  The present invention relates to a thin film manufacturing apparatus and a thin film manufacturing method.

  Currently, thin film manufacturing processes using chemical vapor deposition (CVD) apparatuses are widely applied in the manufacture of electronic devices such as solar cells and LSI (Large Scale Integrated Circuit) elements. This is because the raw material gas, which is the material of the thin film, is introduced into a film-forming chamber in a vacuum state, decomposed by high energy such as plasma to generate active excited atoms, and the chemical reaction of these excited atoms on the substrate surface occurs. It promotes to form a thin film. In such a CVD apparatus, the film is formed not only on the substrate but also on the inner wall of the film forming chamber, the surface of the shower head, and the surface of the substrate stage. Then, as the film forming process is repeated, these adhesion films are deposited, and a part thereof may be peeled off to contaminate the substrate.

For this reason, conventionally, the inside of the film forming chamber is periodically cleaned, and the film adhering to and deposited on the inner wall of the film forming chamber, the shower head, the surface of the substrate stage, and the like is removed. For example, in the case of a CVD apparatus for forming a silicon-based thin film frequently used in the manufacturing process of solar cells and LSI elements, a fluorine-based gas (etching gas) such as NF ₃ is used for the cleaning process. Semiconductors deposited and deposited on the inner wall of the deposition chamber, shower head, substrate stage, etc. by generating plasma while supplying these fluorine-based gases to the deposition chamber and decomposing in the gas phase to form excited fluorine atoms The film is removed by etching.

However, during this cleaning process, fluorides such as SiF _x and AlF, which are reaction products of the silicon-based semiconductor film and the fluorine-based gas, are generated throughout the film-forming chamber. These fluorides are likely to remain in the film forming chamber, and it is difficult to remove them sufficiently by only exhausting with a pump. Actually, when a large amount of fluoride remains in the film forming chamber, it is said that the film forming speed is lowered and the film thickness distribution is deteriorated. In addition, a phenomenon has been reported in which device characteristics deteriorate when residual fluoride is mixed as an impurity in a manufactured semiconductor film.

  Therefore, conventionally, various methods for removing the fluoride remaining in the film forming chamber after the cleaning process have been proposed. For example, a technique for pre-filming after the cleaning process, pre-coating the inner wall surface of the film-forming chamber to confine residual fluoride (for example, refer to Patent Document 1), or a reducing gas such as ammonia in the film-forming chamber after the cleaning process. A method of introducing and generating plasma and gasifying (hydrogen fluoride) residual fluoride to quickly discharge it out of the film forming chamber (see, for example, Patent Document 2), and further after cleaning treatment A method in which at least one of hydrolysis and alcoholysis reaction is performed in the film forming chamber, and the residual fluoride is gasified (hydrogen fluoride) and quickly discharged out of the film forming chamber (for example, Patent Documents) 3) is proposed.

JP 11-340149 A JP-A-7-201738 Japanese Patent Application No. 2004-273136

  However, when adopting a method of performing pre-film formation after the cleaning process as in Patent Document 1, there is a problem that throughput is deteriorated by the time required for pre-film formation and productivity is lowered. . In addition, since the pre-film formation consumes extra source gas, there is a problem that the cost is increased accordingly.

Further, as in Patent Document 2, when reducing gas plasma is generated in the film forming chamber after the cleaning process, ions collide with the inner wall surface of the film forming chamber to cause damage, and an inner wall member (for example, an adhesion prevention plate) Etc.), the maintenance frequency becomes short and the productivity is lowered. Further, as in Patent Document 3, when trying to wake the hydrolysis or alcoholysis in the deposition chamber, for introducing the water (H ₂ O) and alcohol (C _x H _y OH) in the deposition chamber, Oxygen (O) and carbon (C) remain as new impurities, which may adversely affect the film forming process and film properties.

  The present invention has been made in view of the above, and eliminates the influence of the reaction product remaining during the cleaning process without generating any new impurities and without causing damage to the inside of the film forming chamber. It aims at obtaining the thin film manufacturing apparatus and thin film manufacturing method which can manufacture the thin film of a physical property.

  In order to achieve the above object, a thin film manufacturing apparatus according to the present invention includes a film forming chamber, substrate holding means for holding a substrate in the film forming chamber, and a film forming material gas formed on the substrate. A raw material gas supply means for supplying into the chamber, and a cleaning for supplying into the film forming chamber a cleaning gas that reacts with deposits deposited in the film forming chamber by the formation of the film on the substrate to generate a reaction product. A gas supply means, a reaction product removal gas supply means for supplying a reaction product removal gas containing an element that reacts with a constituent element of the reaction product to generate a gas, and a substrate holding means; A gas discharge means which is disposed oppositely and discharges the source gas supplied from the source gas supply means in a shower-like manner toward the substrate holding means; the reaction product and the reaction product removal gas; And a light source emitting light having a releasable energy, said light source, characterized in that the film-forming chamber in the region in which the deposit adheres is arranged to be irradiated.

  According to this invention, the reaction product removal gas supply means for supplying the reaction product removal gas containing the element that reacts with the constituent element of the reaction product generated as a result of the cleaning process to generate gas into the film forming chamber, and the reaction A light source that emits light having energy capable of dissociating the product and the reaction product removal gas, and the light source is disposed so as to irradiate a region in the film forming chamber to which the deposit adheres. The reaction product remaining on the inner wall of the film forming chamber can be decomposed and easily removed as a gas that can be easily exhausted without worrying about damage to the film forming chamber wall or generation of new impurities. As a result, there is an effect that the residual fluoride (impurities) in the film produced thereafter is greatly suppressed, and a thin film having good physical properties can be stably supplied.

1 is a cross-sectional view schematically showing a schematic configuration of a thin film manufacturing apparatus according to Embodiment 1. FIG. FIG. 2 is a flowchart showing an example of a processing procedure in the thin film manufacturing apparatus. FIG. 3 is a diagram showing a mass spectrum when the residual gas in the film forming chamber of the thin film manufacturing apparatus is measured with a mass spectrometer. FIG. 4 is a diagram showing a change in mass spectrum intensity of mass number m / e = 85 when the irradiation time of ultraviolet rays during the fluoride removal process is changed. FIG. 5 is a diagram showing the fluorine content in the semiconductor film manufactured by the thin film manufacturing apparatus. FIG. 6 is a diagram showing voltage-current characteristics (JV characteristics) of a thin-film silicon solar battery cell using an i-type microcrystalline silicon film produced by a thin-film manufacturing apparatus as a power generation layer. FIG. 7 is a cross-sectional view schematically showing an example of the structure of a thin-film silicon solar battery cell. FIG. 8 is a diagram illustrating the values of the short circuit current density (J _sc ), the open circuit voltage (V _oc ), and the _fill factor (FF) obtained from the JV characteristics of FIG. FIG. 9 is a diagram showing the relationship of the required time when forming the photoelectric conversion layer of the thin-film silicon solar cell in one process flow. FIG. 10 is a cross-sectional view schematically showing a schematic configuration of the thin film manufacturing apparatus according to the second embodiment. FIG. 11 is a diagram showing a change in diffuse reflectance when the average surface roughness of the aluminum plate is changed. FIG. 12 is a diagram showing the wavelength dependence of the incident light of the diffuse reflectance of the aluminum plate. FIG. 13 is a diagram showing a change in mass spectrum intensity of mass number m / e = 85 when the irradiation time of ultraviolet rays during the fluoride removal process is changed. FIG. 14 is a diagram showing the relationship of the required time when forming the photoelectric conversion layer of the thin-film silicon solar cell in one process flow.

  Hereinafter, a thin film manufacturing apparatus and a thin film manufacturing method according to embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited to these embodiments.

Embodiment 1 FIG.
1 is a cross-sectional view schematically showing a schematic configuration of a thin film manufacturing apparatus according to Embodiment 1. FIG. The thin film manufacturing apparatus has a film forming chamber 11 made of, for example, aluminum or aluminum alloy. The film forming chamber 11 has, for example, a cylindrical shape. Inside the film forming chamber 11, a stage 12, which is a substrate holding means for horizontally supporting a substrate to be processed, is disposed. The stage 12 is disposed in the vicinity of the central portion in the horizontal direction in the film forming chamber 11, and is supported by the support member 13 inside the film forming chamber 11. Although not shown, the stage 12 incorporates a substrate heating means such as a heater, a holding mechanism for holding the substrate by a method such as vacuum suction, and the like. Further, although not shown, a substrate loading / unloading port is provided on the side wall of the film forming chamber 11 and can be opened and closed by a gate valve (not shown).

  A shower head 14, which is a gas discharge member, is provided above the stage 12 so as to face the substrate holding surface of the stage 12 in the film forming chamber 11. The shower head 14 also functions as an upper electrode and is supported on the side wall of the film forming chamber 11 via an insulating member (not shown). The shower head 14 is provided with a number of discharge holes (not shown) penetrating in the thickness direction, and the gas supplied from the upper part of the film forming chamber 11 is supplied to the space in the film forming chamber 11 in a shower shape. In addition, a high frequency power supply unit 71 that supplies high frequency power to the shower head 14 is connected to the shower head 14 via a feeder line 72. Thus, the stage 12 and the shower head 14 constitute a pair of parallel plate electrodes.

  A gas exhaust port 15 is provided near the bottom of the film forming chamber 11. A vacuum pump 32 as exhaust means is connected to the gas exhaust port 15 via a pipe 31. In addition, a valve 33 is provided on the pipe 31 to switch the degree of exhaust of the gas in the film forming chamber 11 by the vacuum pump 32.

  In the vicinity of the upper part of the film forming chamber 11, a raw material gas supply port 16, a cleaning gas supply port 17, and a reaction product removal gas supply port 18 are provided.

A piping 41 is connected to the raw material gas supply port 16, and a gas valve 42 that switches a raw material gas supply source (not shown) and on / off of the supply of the raw material gas from the raw material gas supply source into the film forming chamber 11 is connected to the piping 41. And are provided. In the case of forming a silicon-based film as the source gas, for example, SiH ₃ gas, H ₂ gas, Ar gas, or the like can be used. In the drawing, one pipe 41 is shown, but a gas valve 42 and a pipe 41 are provided for each source gas supply source.

A piping 51 is connected to the cleaning gas supply port 17, and a gas valve for switching on / off a cleaning gas supply source (not shown) from the cleaning gas supply source into the film forming chamber 11 is connected to the piping 51. 52 are provided. As the cleaning gas, when cleaning a silicon-based film, a gas containing fluorine such as F ₂ , NF ₃ , ClF ₃ , CF ₄ , or a mixed gas containing one or more of these, and N ₂ , Ar, He are used. , Kr, Xe, Ne, or other inert gas or a mixed gas containing one or more of them can be used. In the drawing, one pipe 51 is shown, but a gas valve 52 and a pipe 51 are provided for each cleaning gas supply source.

A piping 61 is connected to the reaction product removal gas supply port 18, and a reaction product removal gas supply source (not shown) and a reaction product from the reaction product removal gas supply source into the film forming chamber 11 are connected to the piping 61. And a gas valve 62 for switching on / off the supply of the object removal gas. When cleaning the silicon-based film with a fluorine-based gas, H ₂ gas can be used as the reaction product removal gas. In this specification, the reaction product means a product that remains in the film forming chamber 11 generated by a reaction between a film deposited and adhered to a component in the film forming chamber 11 and a cleaning gas.

  In the first embodiment, light sources 19 (19a to 19c), which are dissociation means for dissociating the reaction product and the reaction product removal gas, are provided near the upper and lower surfaces of the stage 12 and the upper part of the film forming chamber 11, respectively. The light source 19 is arranged so that the entire region in the film forming chamber 11 where the film may be deposited and adhered, for example, the inner wall of the film forming chamber 11, the stage 12, the surface of the shower head 14, and the like is irradiated. It is desirable.

  In addition, it is desirable that the light source 19 be arranged at a location where film adhesion to the surface of the light source 19 is difficult to occur during film formation. The light source 19a provided on the upper surface of the stage 12 is disposed in a position hidden in the substrate during film formation, that is, in the substrate placement region. This prevents film adhesion to the surface of the light source 19a provided on the upper surface of the stage 12 during film formation. The light source 19 c is provided in the vicinity of the upper part of the film forming chamber 11, specifically, in a space 25 between the upper surface of the film forming chamber 11 where the source gas supply port 16 is provided and the shower head 14. It is considered that radicals hardly fly into the lower surface of the stage 12 or the space 25 between the upper surface of the film forming chamber 11 and the shower head 14 during film formation, and the light sources 19b and 19c provided at these positions. Film adhesion to the surface of the film is also prevented.

  Further, the light source 19 emits light having energy (frequency) that can dissociate the reaction product of the cleaning gas and the coating adhered and deposited in the film forming chamber 11 and the reaction product removal gas. A light source that can be used is used.

When forming a silicon-based film, a fluorine-based gas is used as the cleaning gas as described above. During the cleaning process of the silicon film, Si and F in the fluorine-based gas react to generate SiF _x as a reaction product. Since SiF _x tends to remain in the film forming chamber 11 and is difficult to remove only by evacuation by the vacuum pump 32, in the first embodiment, hydrogen fluoride (HF) is generated from SiF _x and manufactured. SiF _x in the film chamber 11 is removed. This is because HF can be quickly exhausted out of the film forming chamber 11 using the vacuum pump 32 as compared with SiF _x . For this purpose, H ₂ gas is used as the reaction product removal gas.

First, the SiF _x following formula (1) dissociating the Si and F as. Further, in order to make dissociated F into HF, hydrogen molecules (H ₂ ) are also dissociated as shown in the following formula (2).
SiF _x → Si + xF (1)
H ₂ → H + H (2)

Here, since the dissociation energy of SiF _x is 6.2 eV and the dissociation energy of hydrogen molecules is 4.7 eV, light having an energy of 6.2 eV or more is required for photolysis of both SiF _x and H _2. Need to be irradiated. Since 6.2 eV is 200 nm in terms of the wavelength of light, the light emitted from the light source 19 is deep ultraviolet light having a wavelength of 200 nm or less. That is, by irradiating SiF _x and H ₂ with ultraviolet rays having a wavelength of 200 nm or less, it is possible to cause a photodegradation reaction as in the above formulas (1) and (2).

A process for forming a Si film with the thin film manufacturing apparatus having such a structure will be described. FIG. 2 is a flowchart showing an example of a processing procedure in the thin film manufacturing apparatus. First, in the thin film manufacturing apparatus, a cleaning process in the film forming chamber 11 is performed (step S11). Specifically, first, the film forming chamber 11 is evacuated by the vacuum pump 32 so as to have a predetermined degree of vacuum. After that, while introducing a fluorine-based gas such as NF ₃ into the film forming chamber 11 as a cleaning gas, the high-frequency power supply unit 71 supplies a high-frequency power to the shower head 14 serving as the upper electrode while the stage 12 serving as the lower electrode is grounded. Electric power is applied to generate plasma in the space between the shower head 14 and the stage 12 to form excited fluorine atoms. Then, the Si film adhered and deposited on the inner wall of the film forming chamber 11, the surfaces of the shower head 14 and the stage 12 is removed by etching. At this time, fluoride such as SiF _x is generated as a reaction product everywhere in the film forming chamber 11.

  Next, a fluoride removal process is performed (step S12). Specifically, when the cleaning process is completed, the gas valve 52 of the pipe 51 connected to the cleaning gas supply source is closed, and the film forming chamber 11 is sufficiently evacuated by the vacuum pump 32, and then the reaction product removal gas The gas valve 62 of the pipe 61 connected to the supply source is opened to supply hydrogen gas as a reaction product removal gas into the film forming chamber 11. Thereafter, ultraviolet light having a wavelength of 200 nm or less is emitted from the light sources 19 a to 19 c into the film forming chamber 11. The time for emitting ultraviolet rays from the light sources 19a to 19c is preferably 70 seconds or more and 2 minutes or less. This is because, with irradiation for less than 70 seconds, the amount of fluoride remaining in the film-forming chamber 11 cannot be set to an amount that does not deteriorate the characteristics of the film formed by the film-forming process performed thereafter. Because. Moreover, it is because there is no big change in the quantity of the fluoride which remains in the film forming chamber 11 by irradiation longer than 2 minutes.

By irradiating ultraviolet rays while flowing hydrogen gas, the photodecomposition reaction proceeds as shown in the above formulas (1) and (2). That is, fluoride such as SiF _x adhering to the inner wall of the film forming chamber 11 is decomposed (dissociated) into Si and F, and hydrogen gas supplied into the film forming chamber 11 is also decomposed (dissociated) into H. The The decomposed F and H react to generate HF, which is exhausted to the outside of the film forming chamber 11 by the vacuum pump 32. The decomposed Si reacts with H to become silane (SiH ₃ ), and is similarly exhausted to the outside of the film forming chamber 11 by the vacuum pump 32.

  Since the light sources 19a to 19c are arranged so that the entire region where the coating film in the film forming chamber 11 is deposited and adhered is irradiated, the above reaction occurs over almost the entire film forming chamber 11. . For example, the light L1 emitted from the light source 19a installed on the upper surface of the stage 12 is irradiated to the fluoride remaining between the stage 12 and the shower head 14, and the light is decomposed. Further, the light L2 emitted from the light source 19b installed on the lower surface of the stage 12 is irradiated to the residual fluoride that has entered the space under the stage 12, and the light is decomposed. Further, the light L3 emitted from the light source 19c disposed in the space 25 between the upper surface of the film forming chamber 11 and the shower head 14 is irradiated to the residual fluoride that has entered the space 25, and the photolysis is performed. Do. By the above, the residual fluoride in the film forming chamber 11 is removed.

Then, the Si film is formed in the thin film manufacturing apparatus (step S13). Specifically, when the fluoride removal process is completed, the gas valve 62 of the pipe 61 connected to the reaction product removal gas supply source is closed, and the inside of the film forming chamber 11 is sufficiently evacuated using the vacuum pump 32. Later, the gas valve 42 of the pipe 41 connected to the source gas supply source is opened, and source gases such as SiH ₃ gas, H ₂ gas, Ar gas and the like are supplied into the film forming chamber 11. The source gas is dispersed at the outlet of the shower head 14 and is supplied in the shower shape toward the stage 12. Next, when the inside of the film forming chamber 11 reaches a predetermined pressure, high frequency power is applied from the high frequency power supply unit 71 to the shower head 14 that is the upper electrode while the stage 12 that is the lower electrode is grounded. Plasma is generated in the space between 14 and stage 12. As a result, the source gas supplied from the source gas supply source is activated, and a Si film is formed on the substrate. At this time, a film is also deposited on the components in the film forming chamber 11 in contact with the plasma in the same manner as on the substrate. During the deposition of the Si film (semiconductor film), the light sources 19a to 19c are arranged in regions where radicals generated during deposition are difficult to fly, so that film adhesion to the surface is suppressed, and the light source 19a The surface of ˜19c is clouded to prevent the irradiation intensity of ultraviolet rays from being lowered.

  Thereafter, when a Si film having a predetermined thickness is formed on the substrate, the supply of the high frequency power from the high frequency power supply unit 71 is stopped, the gas valve 42 is closed, and the film forming chamber 11 is sufficiently evacuated. Nitrogen gas, inert gas, or the like is supplied into the film forming chamber 11 to obtain a predetermined pressure, and the substrate on the stage 12 is carried out of the film forming chamber 11 from the substrate loading / unloading port. Thus, the process in the thin film manufacturing apparatus is completed. In addition, when forming a film continuously, it returns to step S11 and the above-mentioned process is performed repeatedly.

  Next, a specific example in which the fluoride removal process and the film forming process are performed by irradiating ultraviolet rays after the cleaning process using the thin film manufacturing apparatus according to the first embodiment will be described.

  FIG. 3 is a diagram showing a mass spectrum when the residual gas in the film forming chamber of the thin film manufacturing apparatus is measured with a mass spectrometer. FIG. 3 (a) shows the mass analysis result when only vacuuming is performed after the film forming chamber 11 is cleaned, and FIG. 3 (b) shows the ultraviolet rays from the light source while supplying hydrogen gas after the cleaning process. The mass spectrum at the time of measuring after irradiating for 100 seconds is shown. FIGS. 3A and 3B show the results of measurement after sufficient evacuation. In these figures, the horizontal axis represents the mass number (mass-to-charge ratio, m / e), and the vertical axis represents the spectral intensity (arbitrary unit).

As shown in FIG. 3A, a relatively strong peak at a mass number m / e = 85 was detected from the film forming chamber 11 in which only vacuuming was performed after the cleaning process. This is considered to be a fragment peak corresponding to residual fluoride SiF ₃ . On the other hand, as shown in FIG. 3B, in the spectrum after the residual fluoride removing process of irradiating ultraviolet rays for 100 seconds while supplying hydrogen gas after the cleaning process according to the first embodiment, the mass number m The spectrum of / e = 85 has almost disappeared. Thus, it can be seen that residual fluoride in the film forming chamber 11 can be effectively removed by performing ultraviolet irradiation while supplying hydrogen gas after the cleaning process according to the first embodiment.

FIG. 4 is a diagram showing a change in mass spectrum intensity of mass number m / e = 85 when the irradiation time of ultraviolet rays during the fluoride removal process is changed. In this figure, the horizontal axis indicates the ultraviolet irradiation time (second, sec), and the vertical axis indicates the mass spectrum intensity (arbitrary unit) of mass number m / e = 85 corresponding to SiF ₃ .

  As shown in this figure, the spectral intensity of mass number m / e = 85 monotonously decreases as the time of ultraviolet irradiation treatment becomes longer, and becomes almost zero after irradiation for 70 seconds or more. That is, it can be seen that the residual fluoride produced in the film forming chamber 11 can be removed almost outside the film forming chamber 11 by performing the ultraviolet irradiation treatment for 70 seconds or more. Therefore, it is desirable that the irradiation time of ultraviolet rays using a light source is 70 seconds or more.

  FIG. 5 is a diagram showing the fluorine content in the semiconductor film manufactured by the thin film manufacturing apparatus. In this figure, the horizontal axis indicates the depth (μm) from the surface of the semiconductor film deposited on the substrate, and the vertical axis indicates the fluorine content (atoms / cc) in the semiconductor film. Here, the semiconductor film to be measured is a thin film manufacturing apparatus in which a microcrystalline silicon film is deposited on a substrate. A profile P1 in the figure is a case where a microcrystalline silicon film is formed by the processing flow according to the first embodiment shown in FIG. 2, and a profile P2 is obtained by skipping the pre-film formation process with a conventional thin film manufacturing apparatus. This is a comparative example in which a crystalline silicon film is formed, that is, a case where a microcrystalline silicon film is formed immediately after performing a cleaning process. These profiles P1 and P2 are signal intensities (fluorine content profiles in the film thickness direction) when measured with a secondary ion mass spectrometer (hereinafter referred to as SIMS).

  As shown in profiles P1 and P2, when the film is formed after the fluoride removal process according to the first embodiment, the film is formed without performing the fluoride removal process according to the first embodiment. Thus, the fluorine content in the microcrystalline silicon film is reduced by about one digit.

FIG. 6 is a diagram showing voltage-current characteristics (JV characteristics) of a thin-film silicon solar battery cell using an i-type microcrystalline silicon film produced by a thin-film manufacturing apparatus as a power generation layer. In this figure, the horizontal axis indicates the voltage (Voltage, V) appearing at both ends of the thin film solar cell, and the vertical axis indicates the current density (Current density, A / cm ² ) flowing through the solar cell. Here, the JV characteristics are measured while irradiating simulated sunlight (100 mW / cm ² ).

  FIG. 7 is a cross-sectional view schematically showing an example of the structure of a thin-film silicon solar battery cell. The thin-film silicon solar battery cell 100 has a structure in which a first electrode layer 102, a photoelectric conversion layer 103 including a microcrystalline silicon film, and a second electrode layer 107 are sequentially stacked on a substrate 101. As the substrate 101, a light-transmitting insulating substrate such as glass can be used, and as the first electrode layer 102, a transparent conductive material such as ITO (Indium Tin Oxide) can be used. As the photoelectric conversion layer 103, a microcrystalline silicon film having a pin structure can be used. For example, a p-type microcrystalline silicon film 104, an i-type microcrystalline silicon film 105, and an n-type microcrystalline silicon film 106 are stacked. The structure of the structure made can be used. As the second electrode layer 107, for example, a metal material that reflects light such as Al can be used. This cross-sectional view is schematic, and the relationship between the thickness and width of the layers, the ratio of the thicknesses of the layers, and the like are different from the actual ones. In the thin-film silicon solar battery cell 100 having such a structure, light is incident from the substrate 101 side.

  A curve S1 in FIG. 6 indicates the J-- for the thin-film silicon solar battery cell 100 in which the i-type microcrystalline silicon film 105 is formed according to the processing flow shown in FIG. 2 using the thin-film manufacturing apparatus shown in FIG. V characteristics. Curve S2 is a JV characteristic of the thin film silicon solar battery cell 100 of the comparative example having an i-type microcrystalline silicon film manufactured by skipping the pre-film forming process with a conventional thin film manufacturing apparatus.

FIG. 8 is a diagram illustrating the values of the short circuit current density (J _sc ), the open circuit voltage (V _oc ), and the _fill factor (FF) obtained from the JV characteristics of FIG. As shown in FIGS. 6 and 8, the short-circuit silicon solar cell 100 manufactured by the method according to the first embodiment is shorter in the short-circuit current density than the thin-film silicon solar cell 100 manufactured by the method according to the comparative example. J _sc , the open circuit voltage V _oc and the _fill factor FF are all _superior . This is because the impurity amount in the i-type microcrystalline silicon film 105 constituting the photoelectric conversion layer 103 (fluorine content in the film) is applied to the comparative example by applying the thin film manufacturing apparatus cleaning method according to the first embodiment. This is probably due to the fact that it can be greatly reduced.

  FIG. 9 is a diagram showing the relationship of the required time when forming the photoelectric conversion layer of the thin-film silicon solar cell in one process flow. In this figure, the horizontal axis indicates the required time. Further, the upper part shows a case where the method according to Patent Document 1 is used as the fluoride removing process, and the lower part shows a case where the method according to the first embodiment is used as the fluoride removing process.

  As described above, when the pre-film formation according to Patent Document 1 is performed as the fluoride removal process, the steps of “introduction of raw material gas”, “film formation” and “exhaust of residual gas” are performed. It takes at least 10 minutes. On the other hand, in the fluoride removal process according to the first embodiment, only the ultraviolet irradiation is performed while introducing hydrogen gas into the film forming chamber 11, and the ultraviolet irradiation time needs to be at least 70 seconds. It can be 2 minutes or less. Further, the cleaning time according to Patent Document 1 is set to 20 minutes, the pre-film forming time is set to 5 minutes, the film forming time is set to 40 minutes, the cleaning time according to Embodiment 1 is set to 15 minutes, and the ultraviolet irradiation time is set to 120 seconds. When the film forming time is 40 minutes, the time required for one process using the fluoride removing process according to the first embodiment (hereinafter referred to as the total process time) is 3420 seconds. This can be reduced by about 12% compared to the total process time of 3900 seconds using the compound removal process. In the first embodiment, since the thickness of the film attached to the film forming chamber 11 is reduced by the amount that the pre-film formation is omitted, the cleaning time can be shortened as compared with Patent Document 1.

  In the first embodiment, a light source that emits ultraviolet light having a wavelength of 200 nm or less is provided in the film forming chamber 11, and ultraviolet light is irradiated while supplying hydrogen gas into the film forming chamber 11 after the cleaning process. As a result, the fluoride remaining on the inner wall of the film forming chamber 11 during the cleaning process can be decomposed and quickly removed as hydrogen fluoride that can be easily exhausted by the vacuum pump 32. Further, compared to the prior art (Patent Documents 2 and 3), it is possible to discharge the residual fluoride to the outside of the film forming chamber 11 without worrying about damage to the inner wall of the film forming chamber 11 or generation of new impurities. . As a result, there is an effect that the residual fluoride (impurities) in the film produced thereafter is greatly suppressed, and a thin film having good physical properties can be stably supplied.

  Further, immediately after the process of light emission into the film forming chamber 11, the film forming process of the coating film (semiconductor film) can be started. That is, since it is possible to omit the pre-film forming process compared to the conventional technique (Patent Document 1), the pre-film forming process is performed after the cleaning process in the film forming chamber 11 to remove residual fluoride. As a result, the time required for the process and the amount of the raw material gas used can be reduced, and it is possible to improve throughput (improve productivity) and reduce costs.

Embodiment 2. FIG.
FIG. 10 is a cross-sectional view schematically showing a schematic configuration of the thin film manufacturing apparatus according to the second embodiment. In addition to the configuration of the thin film manufacturing apparatus of FIG. 1 according to the first embodiment, this thin film manufacturing apparatus applies light to the inner wall of the film forming chamber 11, the surface of the shower head 14, and the surfaces of the stage 12 and the support member 13. The diffuse reflection member 21 is provided. As a result, the light emitted from the light source 19 is diffusely reflected by the light diffusion reflection member 21 provided on the inner wall of the film forming chamber 11, the surface of the shower head 14, and the surfaces of the stage 12 and the support member 13, and is high. It is possible to reach every corner of the film forming chamber 11 while maintaining the strength. In addition, the same code | symbol is attached | subjected to the component same as Embodiment 1, and the description is abbreviate | omitted.

  Here, when a lamp that emits ultraviolet rays is used as the light source 19, an ultraviolet diffuse reflection plate can be used as the light diffusion reflection member 21. As the ultraviolet diffuse reflection plate, it is desirable to use an aluminum plate whose surface has a fine uneven shape with an average surface roughness Ra = 0.5 μm.

  FIG. 11 is a diagram showing a change in diffuse reflectance when the average surface roughness of the aluminum plate is changed. In this figure, the horizontal axis represents the average surface roughness Ra (μm) of the surface of the aluminum plate, and the vertical axis represents the diffuse reflectance (%). Here, the diffuse reflectance is measured when ultraviolet light having a wavelength of 350 nm is incident on an aluminum plate whose average surface roughness Ra is changed in the range of 0.3 μm to 2.0 μm. As is clear from FIG. 11, the ultraviolet diffuse reflectance is highest in an aluminum plate having an average surface roughness Ra of 0.5 μm.

  FIG. 12 is a diagram showing the wavelength dependence of the incident light of the diffuse reflectance of the aluminum plate. In this figure, the horizontal axis indicates the wavelength (nm) of ultraviolet light incident on the aluminum plate, and the vertical axis indicates the diffuse reflectance (%). In this figure, curve R1 shows the case of using a roughened aluminum plate with an average surface roughness Ra fixed to 0.5 μm, and curve R2 shows an untreated aluminum plate (conventional device). The average surface roughness Ra of the member in FIG. 5 is about 5 μm). From FIG. 12, in the ultraviolet region with a wavelength of 250 to 400 nm, the surface of the aluminum plate processed to have an average surface roughness Ra of 0.5 μm has a higher diffuse reflectance than when an untreated aluminum plate is used. You can see that Thus, even when ultraviolet rays having a wavelength of 200 nm or less are used, it can be analogized that the irradiated ultraviolet rays can be efficiently reflected by using an aluminum plate having an average surface roughness Ra of about 0.5 μm. Is done.

FIG. 13 is a diagram showing a change in mass spectrum intensity of mass number m / e = 85 when the irradiation time of ultraviolet rays during the fluoride removal process is changed. In this figure, the horizontal axis indicates the ultraviolet irradiation time (second, sec), and the vertical axis indicates the mass spectrum intensity (arbitrary unit) of mass number m / e = 85 corresponding to SiF ₃ . A curve SP1 indicates the mass spectrum intensity in the case of the thin film manufacturing apparatus having a structure that does not use the ultraviolet diffuse reflector according to the first embodiment, and a curve SP2 indicates the average surface roughness Ra = 0.5 μm according to the second embodiment. The mass spectral intensity in the case of the thin film manufacturing apparatus of the structure using an ultraviolet diffusive reflector is shown.

  In the mass spectrum according to the second embodiment shown by the curve SP2, the spectral intensity due to the residual fluoride decreases in a shorter time than the curve SP1 according to the first embodiment. Specifically, in the first embodiment, the mass spectrum intensity is almost zero after the ultraviolet irradiation of about 70 seconds, whereas in the second embodiment, the mass spectrum intensity is almost zero after the ultraviolet irradiation of about 20 seconds. It has reached zero. That is, by using the thin film manufacturing apparatus according to the second embodiment, the fluoride remaining in the film forming chamber 11 is decomposed in about 0.3 times as compared with the first embodiment, and the film is formed more quickly. It can be removed outside the chamber 11.

  FIG. 14 is a diagram showing the relationship of the required time when forming the photoelectric conversion layer of the thin-film silicon solar cell in one process flow. In this figure, the horizontal axis indicates the required time. Moreover, the upper stage shows the case where the method according to Patent Document 1 is used as the fluoride removal process, the middle stage shows the case where the method according to Embodiment 1 is used as the fluoride removal process, and the lower stage shows the case as the fluoride removal process. The case where the method by the form 2 of this is used is shown. In addition, since the figure shown by the upper stage and the middle stage is the same as that of FIG. 9 of Embodiment 1, it abbreviate | omits about the detailed description.

  In the second embodiment, since the fluoride removing process is performed by the thin film manufacturing apparatus provided with the ultraviolet diffuse reflection plate having the unevenness of the average surface roughness Ra = 0.5 μm in the film forming chamber 11, it is emitted from the light source 19. Ultraviolet rays are diffused and reflected with high intensity by the constituent members in the film forming chamber 11, and the diffused ultraviolet rays are further irradiated to other constituent members in the film forming chamber 11. This effectively irradiates the residual fluoride in the film forming chamber 11 with ultraviolet rays as compared with the first embodiment, and promotes the photodecomposition reaction of the residual fluoride. As a result, the total process time according to the second embodiment is further shorter than the total process time according to the first embodiment. For example, when the cleaning time according to the second embodiment is 15 minutes, the ultraviolet irradiation time is 20 seconds, and the film forming time is 40 minutes, the total process time using the fluoride removing process according to the second embodiment is 3320 seconds, which is about 15% shorter than 3900 seconds, which is the total process time using the fluoride removal process according to Patent Document 1.

  In the second embodiment, the light diffusing and reflecting member 21 having irregularities with an average surface roughness Ra of about 0.5 μm is provided in a region where a film may be formed during film formation in the film forming chamber 11. As a result, the light emitted from the light source 19 during the fluoride removal treatment is diffusely reflected while maintaining high intensity on the surface of the constituent member in the film forming chamber 11, and the light reaches every corner in the film forming chamber 11. The reaction product remaining on the surface of the constituent member in the film forming chamber 11 can be efficiently photodecomposed and removed. As a result, the time required for the process and the amount of the source gas used are reduced and the throughput is improved as compared with the case where the remaining reaction products are removed by performing the pre-film formation after the cleaning process in the film-forming chamber 11 ( Productivity) and cost reduction.

  In the above description, the Si film is formed by the thin film manufacturing apparatus, the Si film deposited and adhered in the thin film manufacturing apparatus is cleaned using a fluorine-based gas, and then the fluoride removal process is performed. Although described, the present invention is not limited to this. The present invention is applied if the reaction product remaining in the thin film manufacturing apparatus is dissociated when the film deposited and adhered in the thin film manufacturing apparatus is cleaned, and the gas can be exhausted by the vacuum pump 32. can do.

  As described above, the thin film manufacturing apparatus according to the present invention is useful for manufacturing a semiconductor thin film, and is particularly suitable for a thin film manufacturing apparatus for manufacturing a Si-based thin film.

DESCRIPTION OF SYMBOLS 11 Film forming chamber 12 Stage 13 Support member 14 Shower head 15 Gas exhaust port 16 Raw material gas supply port 17 Cleaning gas supply port 18 Reaction product removal gas supply port 19, 19a-19c Light source 21 Light diffusive reflection member 31, 41, 51 , 61 Piping 32 Vacuum pump 33 Valve 42, 52, 62 Gas valve 71 High frequency power supply unit 72 Feed line 100 Thin-film silicon solar cell 101 Substrate 102 First electrode layer 103 Photoelectric conversion layer 104 p-type microcrystalline silicon film 105 i-type micro Crystalline silicon film 106 n-type microcrystalline silicon film 107 Second electrode layer

Claims (10)

A film forming chamber;
Substrate holding means for holding the substrate in the film forming chamber;
A raw material gas supply means for supplying a raw material gas for a coating film formed on the substrate into the film forming chamber;
Cleaning gas supply means for supplying a cleaning gas into the film forming chamber that reacts with deposits deposited in the film forming chamber by the formation of the film on the substrate to generate a reaction product;
A reaction product removal gas supply means for supplying a reaction product removal gas containing an element that reacts with a constituent element of the reaction product to generate a gas into the film forming chamber;
A gas discharge means that is disposed opposite to the substrate holding means and discharges the source gas supplied from the source gas supply means in a shower shape toward the substrate holding means;
A light source that emits light having energy capable of dissociating the reaction product and the reaction product removal gas;
With
The thin film manufacturing apparatus, wherein the light source is disposed so as to irradiate a region in the film forming chamber to which the deposit adheres.   The light source includes a region on the first surface side that holds the substrate of the substrate holding unit, a second surface side that faces the first surface of the substrate holding unit, and The thin film manufacturing apparatus according to claim 1, wherein the thin film manufacturing apparatus is provided.   3. The thin film manufacturing according to claim 2, wherein the light source is provided in a space in the film forming chamber between the gas discharge unit and a source gas supply port connected to the source gas supply unit. apparatus.   The light diffusing member that scatters the light from the light source is further provided on a constituent member that constitutes a region in the film forming chamber to which the deposit adheres. The thin film manufacturing apparatus described. The source gas is a source gas containing Si,
The cleaning gas is a cleaning gas containing F;
The reaction product removal gas is a reaction product removal gas containing H ₂ ,
The thin film manufacturing apparatus according to any one of claims 1 to 4, wherein the light source is a light source that emits ultraviolet light having a wavelength of 200 nm or less.   5. The thin film manufacturing apparatus according to claim 4, wherein the light diffusing member is an aluminum plate having irregularities with an average surface roughness of 0.5 [mu] m formed on the surface. In a thin film manufacturing method of supplying a source gas into a film forming chamber and forming a film on a substrate disposed in the film forming chamber,
A cleaning step of supplying a cleaning gas into the film forming chamber and reacting a deposit adhered to the film forming chamber by the formation of the film on the substrate and the cleaning gas to generate a reaction product;
A reaction product that radiates light having energy capable of dissociating the reaction product into the film forming chamber to photolyze the reaction product, exhausts the reaction product to the outside of the film forming chamber, and removes the reaction product. A removal step;
A thin film manufacturing method comprising:   In the reaction product removal step, the reaction product and the reaction product are supplied while supplying a reaction product removal gas containing an element that reacts with a constituent element of the reaction product and generates a gas into the film forming chamber. The reaction product and the reaction product removal gas are photodecomposed by radiating light having energy capable of dissociating the removal gas into the film forming chamber, and the element from which the reaction product is dissociated and the reaction product removal gas. The thin film manufacturing method according to claim 7, wherein a gas obtained by a reaction with an element dissociated from is exhausted to the outside of the film forming chamber.   9. The thin film manufacturing method according to claim 7, further comprising a film forming step of carrying the substrate into the film forming chamber and forming the film on the substrate after the reaction product removing step. Method. The source gas is a source gas containing Si,
The cleaning gas is a cleaning gas containing F;
The reaction product removal gas is a reaction product removal gas containing H ₂ ,
The thin film manufacturing method according to any one of claims 7 to 9, wherein in the reaction product removing step, ultraviolet rays having a wavelength of 200 nm or less are emitted.

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