JP3759075B2 - Cat-PECVD method, film formed using the same, thin film device including the film, and film processing system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a PECVD (Plasma Enhanced Chemical Vapor Deposition) method which is a CVD (Chemical Vapor Deposition) method using plasma as a means for decomposing and activating a film forming gas, and a method for decomposing and activating a film forming gas. Cat-CVD (Catalytic Chemical Vapor Deposition: Catalytic CVD), which is a CVD method using a thermal catalyst as the chemical conversion means, and a new, unprecedented The present invention relates to a Cat-PECVD method that is a CVD method, a film formed by using the method, and a thin film device formed by using the film, and in particular, high-speed Si-based thin films in photoelectric conversion devices typified by thin-film Si-based solar cells. The present invention relates to a technology capable of forming a film with a high quality, a uniform film thickness and a uniform film quality over a large area, and further capable of forming a film with very high productivity.
[0002]
[Prior art and its problems]
High-quality and high-speed film-forming technology is indispensable for high-performance and low-cost of various thin-film devices. Especially in thin-film Si-based solar cells that are representative of photoelectric conversion devices, the high-quality and high-speed of Si-based films In addition to film formation, large-area film formation and further high productivity are simultaneously required.
[0003]
The PECVD method and Cat-CVD method are widely known as low-temperature deposition methods for Si-based thin films, and both are actively researched and developed mainly for the formation of hydrogenated amorphous silicon films and crystalline silicon films. Has been made.
[0004]
FIG. 8 shows a PECVD apparatus as Conventional Example 1, and FIG. 9 shows a Cat-CVD apparatus as Conventional Example 2. 8, 500 is a shower head, 501 is a gas inlet, 502 is a gas outlet, 503 is a plasma space, 504 is a plasma generating electrode, 505 is a high-frequency power source, 506 is a base, 507 is a base heater, and 508 is A gas exhaust vacuum pump 509 is an insulating member for electrical insulation. In FIG. 9, 600 is a shower head, 601 is a gas inlet, 602 is a gas outlet, 603 is an active gas space, 604 is a thermal catalyst, 605 is a power source for heating the thermal catalyst, 606 is a base, 607 Is a substrate heater, and 608 is a gas exhaust vacuum pump.
[0005]
Where SiH _Four Gas and H ₂ Taking the case of forming a Si film using a gas as an example, in the PECVD apparatus shown in FIG. 8, the gas introduced from the gas inlet 501 provided in the shower head 500 is plasma from the gas outlet 502. It is guided to the space 503 and excited and activated in the plasma space 503 to generate deposition species, which are deposited on the opposing substrate 506 to form a Si film. Here, the plasma is generated by using a high frequency power source 505.
[0006]
In the Cat-CVD apparatus shown in FIG. 9, the gas introduced from the gas inlet 601 provided in the shower head 600 is guided from the gas jet port 602 to the film forming space and installed in the film forming space. The activated thermal catalyst 604 is activated to form an active gas space 603 to generate a deposition species, which is deposited on the opposing substrate 606 to form a Si film. Here, heating of the thermal catalyst 604 is realized by using a heating power source 605.
[0007]
However, these conventional techniques have the following problems. That is, in the PECVD method, in order to realize high-speed film formation, the plasma power is increased and SiH is increased. _Four Gas or H ₂ Although it is necessary to promote the decomposition of gas, this increase in plasma power is nothing but to increase the electron temperature Te in the plasma (the plasma potential Vp increases in proportion to Te). Increase the ion bombardment on the surface of the film, and SiH ₂ This led to the promotion of higher-order silane production (final promotion of powder production) due to the increase in the production rate of molecules, and it was inevitable to invite elements that go against quality improvement.
[0008]
Here, if the plasma excitation frequency is set to the VHF band or higher instead of increasing the plasma power, the ion bombardment is reduced by the reduction of the plasma potential Vp, and a high-quality film formation of a hydrogenated amorphous silicon film or a crystalline silicon film is achieved. Is effective (see J. Meier et al, Technical digest of 11th PVSEC (1999) p. 221, O. Vetterl et al, Technical digest of 11th PVSEC (1999) p. 233), but crystalline Si The formation of a film requires the generation of sufficient atomic hydrogen. For this purpose, no matter how much the VHF band frequency is used, an increase in plasma power is unavoidably inevitably caused if a high-speed film formation is required. Invitation of the problems described above could not be avoided.
[0009]
Therefore, as a measure for increasing the atomic hydrogen density without increasing the plasma power, increasing the hydrogen dilution rate, that is, the gas flow rate ratio H ₂ / SiH _Four It is possible to increase the _Four Since the partial pressure of the gas is lowered, the high-speed film formation is in a reverse direction as it is, so eventually the plasma power is increased and SiH is increased. _Four It was necessary to promote the decomposition of the above, and it was impossible to avoid the above-mentioned problems.
[0010]
Although it is conceivable to increase the deposition pressure as a measure to reduce ion bombardment even if the plasma power is increased, the increase in deposition pressure on the other hand leads to the promotion of higher order silane formation reaction by increasing the gas molecule density. As a result, it has been difficult to eliminate factors that reduce film quality such as powder production.
[0011]
On the other hand, in the Cat-CVD method, since no plasma is used, the above-described problem of ion bombardment does not exist in principle, the generation of powder is extremely small, and the generation of atomic hydrogen is greatly promoted. In recent years, it has attracted attention (H. Matsumura, Jpn. J. Appl. Phys. 37 (H. Matsumura, Jpn. J. Appl. Phys. 37). 1998) 3175-3187, REI Schropp et al, Technical digest of 11th PVSEC (1999) p. 929-930).
[0012]
However, at present, the problem of the substrate temperature rise due to radiation from the thermal catalyst is inevitable, and it is not always easy to stably form a high-quality film. SiH _Four Generation of atomic Si is inevitable because the gas is directly decomposed by the thermal catalyst. This atomic Si is not preferable for the formation of a high-quality Si film, and the atomic Si is H or H in the gas phase. ₂ SiH and SiH produced by reaction with ₂ Such radicals are also unfavorable for the formation of a high-quality Si film, and it is very difficult to form a high-quality crystalline Si film at high speed.
[0013]
With respect to the above problems, the present inventors have already studied the integration of the PECVD method and the Cat-CVD method. Already, Japanese Patent Application Nos. 2000-130858, 2001-293031, and 2002 No. -67445 discloses a Cat-PECVD method with a built-in thermal catalyst.
[0014]
FIG. 10 shows a typical device structure. In FIG. 10, 700 is a shower head, 701 is a raw material gas introduction port, 702 is a non-Si non-C gas introduction port, 703 is a raw material gas introduction route, 704 is a non-Si non-C gas introduction route, and 705 is heat. Catalyst body, 706 is a heating power source, 707 is a plasma space, 708 is a plasma generating electrode, 709 is a high frequency power source, 710 is a raw material gas outlet, 711 is a non-Si / non-C gas outlet, and 712 is manufactured A substrate for the film, 713 is a heater for heating the substrate, 714 is a vacuum pump for exhausting gas, and 715 is a radiation blocking member.
[0015]
This Cat-PECVD method uses Si-based source gas and H ₂ Gas and H ₂ The gas is heated and activated by the thermal catalyst 705 installed in the gas introduction path, and the Si-based gas is mixed in the plasma space 707 to form a film. Even so, a high-quality crystalline Si film having high crystallinity can be easily obtained. This is because this method uses a thermal catalyst to produce H ₂ Decomposition / activation amount of SiH _Four Can be freely controlled independently of the amount of plasma decomposition and activation, and SiH _Four Is activated only by plasma, so that undesirable radical generation by the thermal catalyst 705 can be avoided, and a radiation blocking member 715 can be installed, so that radiation directly reaching the substrate 712 from the thermal catalyst 705 can be generated. The film formation surface temperature can be prevented from being undesirably increased, and further, the gas heating effect as a secondary effect using the thermal catalyst 705 can suppress the higher order silane formation reaction in the gas phase ( SiH ₂ Since the higher order silane formation reaction due to the molecule insertion reaction is an exothermic reaction, the increase in the gas temperature due to gas heating has the effect of braking the higher order silane formation reaction). Furthermore, a high frequency power source of 27 MHz or higher can be used by using the shower head 700 and using a non-plate electrode (for example, an antenna electrode) as the plasma generation electrode 708 instead of the conventional plate electrode. It had the ability to achieve uniform film thickness and uniform film quality in a large area. In addition, as a more special form in this case, a system in which a non-plate electrode also serves as a shower head has been partially disclosed. With the above, satisfactory uniform film thickness distribution (within ± 15% as a guideline) and homogeneous film quality distribution (for example, within ± 15% as crystallization rate distribution and within ± 10% as efficiency characteristic distribution) at 1m square size It could be obtained under high-speed and high-quality film forming conditions.
[0016]
However, even in the prior arts by the present inventors that exhibit these remarkable effects, there is room for further improvement in the technique of the method in which the non-planar electrode also serves as a shower head. Technology development was desired.
[0017]
In order to solve these problems, the present inventors have developed the antenna electrode type Cat-PECVD method disclosed in Japanese Patent Application No. 2002-155537-155544. This makes it possible to generate a uniform large-area plasma even at a high frequency using the VHF band. Due to the effect of adding a thermal catalyst, for example, high-quality hydrogenated amorphous silicon film or crystalline silicon even under high-speed film forming conditions. Films such as membranes became possible. By arranging a plurality of antenna antenna electrodes arranged in parallel in the film forming chamber, it becomes possible to form a film on a plurality of substrates simultaneously, thereby realizing a highly productive film processing system. I was able to.
[0018]
However, there is still room for improvement in the cooling method of the antenna electrode in making the film thickness distribution and film quality distribution of the thin film uniform. That is, in addition to the problem that the high frequency power itself supplied to the antenna electrode inevitably becomes thermal energy and heats the antenna electrode to hinder the uniformity of plasma generation, the thermal catalyst according to the present invention. In the antenna electrode with a built-in, the thermal radiation from the built-in thermal catalyst further promotes the heating of the antenna electrode, which may also hinder the uniformity of plasma generation, In some cases, the problem of deformation due to heating cannot be ignored.
[0019]
Technical digest of 11th PVSEC (1999) p779 discloses a plasma CVD apparatus in which a thermal catalyst is disposed immediately after a hydrogen gas introduction port. Although the introduction ports of hydrogen gas and silane gas are different, the hydrogen gas and silane gas do not pass through the shower electrode, and it is difficult to obtain a uniform film thickness distribution and film quality distribution in a large area. In addition, since the thermal catalyst is not isolated from the film forming space by the shower electrode, it is impossible to reduce the contact reaction with the silane gas, which is not preferable for high-quality film formation, and gas phase reaction with it. SiH and SiH, which are undesirable in the same high-quality film formation that is a generated molecule ₂ Such radical generation is unavoidable. Moreover, the concept of the radiation blocking structure and the VHF band of the plasma generation frequency is not shown, and it is difficult to improve the quality. Moreover, the antenna electrode which makes the core of this invention mentioned later is not used.
[0020]
Also, Technical digest of 16th EPSEC (2000) p421 discloses a capacitively coupled RF plasma CVD apparatus in which a thermal catalyst is installed in the plasma space, but it does not introduce gas separately. Also, the introduced gas does not pass through the shower electrode. Moreover, since the thermal catalyst is installed in the plasma space, it is impossible to block radiation to the substrate. There is no concept of an antenna electrode.
[0021]
Japanese Patent No. 2692326 discloses a catalytic CVD method in which a radiation blocking member that allows gas to pass between the catalyst body and the substrate is installed, but the gas is used so that the source gas is not activated by the thermal catalyst body. It is not introduced separately and does not activate the source gas by plasma. Of course, there is no concept of antenna electrodes.
[0022]
Japanese Patent Laid-Open No. 10-310867 discloses a thin film forming apparatus provided with a catalyst electrode between a plasma generating electrode and a gas inlet, but it does not separate and introduce a source gas. Also, it does not have a radiation blocking structure. There is no concept of an antenna electrode.
[0023]
In Japanese Patent Application Laid-Open No. 11-54441, a raw material gas is supplied into a container in which a thermal catalyst is placed, the inside of the container is isolated from the substrate, and the gas is supplied to the substrate by a differential pressure from a gas outlet. Although a catalytic CVD apparatus to be supplied is disclosed, the raw material gas is not separately introduced and is not related to the PECVD method. There is no concept of an antenna electrode.
[0024]
Japanese Patent No. 1994526 discloses a method of forming a film by introducing a raw material gas and a heating gas for decomposing the raw material gas, but it does not use a shower head and does not emit radiation. It does not have a blocking structure. There is no concept of an antenna electrode.
[0025]
Japanese Patent No. 1994527 discloses a method of forming a film by pyrolyzing the source gas, but it is not a method of not pyrolyzing the source gas and does not have a radiation blocking structure. Further, plasma is not used, and a shower head is not used. Of course, there is no concept of antenna electrodes.
[0026]
Japanese Patent No. 1927388 discloses a method in which a film-like activation means made of tungsten is provided in a film-forming space to activate a gas containing hydrogen to deposit a film. It is not a method of separating and introducing without performing, and it does not have a radiation blocking structure. There is no concept of an antenna electrode.
[0027]
Japanese Patent No. 2547741 discloses a structure in which one transport pipe is disposed inside the other, and SiH _Four And H ₂ Is disclosed, but it does not use a shower head and does not have a radiation blocking structure. There is no concept of an antenna electrode.
[0028]
In Japanese Patent No. 2927944, hydrogen gas is activated in a space different from the film formation space, and this is mixed with and brought into contact with the source gas to form a plasma region, and the hydrogen gas is activated periodically. Thus, although a method for depositing a film so that the substrate is intermittently and periodically exposed to plasma is disclosed, it does not use a shower head and does not have a radiation blocking structure. There is no concept of an antenna electrode.
[0029]
Japanese Patent Application Laid-Open No. 2000-114256 describes a method in which a catalyst is allowed to act on a raw material gas to decompose it, and plasma treatment is performed to form a film. Further, neither a shower head is used nor a radiation blocking structure. There is no concept of an antenna electrode.
[0030]
Japanese Patent Application Laid-Open No. 2000-319442 discloses a method of forming a film with an apparatus configuration having a surface reaction mechanism portion installed in the vicinity from the plasma generation unit to the substrate surface. It does not separate and introduce without being disassembled, and does not use a shower head. Further, since the thermal catalyst is between the plasma and the substrate, it is impossible to block radiation to the substrate. There is no concept of an antenna electrode.
[0031]
Japanese Patent Laid-Open No. 2000-323421 discloses SiH. _Four And H ₂ And SiH _Four The gas is activated by plasma and irradiates the substrate with ions and radicals. ₂ A method is disclosed in which a gas is activated by a heated catalyst provided in a gas inlet and irradiated onto a substrate. However, the gas does not use a shower head and does not have a radiation blocking structure. There is no concept of an antenna electrode.
[0032]
Japanese Patent Laid-Open No. 9-137274 discloses SiH in the plasma space. _Four And H ₂ And introduced separately, H ₂ Discloses a method of activating with heat or plasma in the introduction process, but it does not use a shower head nor has a radiation blocking structure. There is no concept of an antenna electrode.
[0033]
Japanese Laid-Open Patent Publication No. 4-236781 discloses an antenna electrode type PECVD apparatus excellent in large-area uniform film formation using a ladder-like planar coil (ladder) electrode. It does not heat or activate the gas.
[0034]
Japanese Patent Application Laid-Open No. 2001-295052 discloses an antenna electrode type PECVD that can form a large-area uniform film thickness by supplying AM-modulated VHF high frequency (20 to 600 MHz to microwave) to the inductively coupled electrode. Although an apparatus is disclosed, the gas is not heated and activated using a thermal catalyst.
[0035]
Japanese Patent Laid-Open No. 7-41950 discloses a method of obtaining a high quality film by heating a hardly decomposable gas in advance with a gas heating heater to improve decomposability in plasma. The catalyst body is not used, and therefore, the thermal catalyst body is not installed in the antenna electrode, and it is not activated (decomposed) only by heating the gas. SiH _Four And H ₂ Are introduced separately and H ₂ It is not something that heats and activates only the thermal catalyst.
[0036]
Japanese Patent Laid-Open No. 6-283436 describes a method for realizing high-speed film formation by heating and introducing a reactive gas. However, it does not use a thermal catalyst, and therefore heat is not contained in the antenna electrode. The catalyst body is not installed, and it is not activated (decomposed) only by heating the gas. SiH _Four And H ₂ Are introduced separately and H ₂ It is not something that heats and activates only the thermal catalyst.
[0037]
Japanese Patent Laid-Open No. 5-283344 discloses a ladder-like planar coil electrode wire with a heater that can control the temperature of the wire material independently, and the reaction gas pressure distribution in the reaction vessel is controlled so as to be uniform and homogeneous. Although a method for realizing film formation is described, a thermal catalyst is not used, and therefore, a thermal catalyst is not installed in the antenna electrode, and it is activated (decomposed) only by heating the gas. It does not lead to. Further, the gas is not separated and introduced by the gas type.
[0038]
The present invention has been made based on such a background. The Si-based film or the C-based film is formed at a high speed and with a high quality, and with a uniform film thickness and a uniform film quality over a large area. It is another object of the present invention to provide a Cat-PECVD method capable of realizing high productivity, a film formed using the Cat-PECVD method, and a device manufactured using the film.
[0039]
[Means for Solving the Problems]
The Cat-PECVD method of the present invention does not include Si and C in the molecular formula heated by a source gas containing a gas containing Si and / or C in the molecular formula and a thermal catalyst disposed in the gas introduction path. A plurality of gas jets provided in the antenna electrode through the hollow portion of the antenna electrode having a hollow structure installed in the film forming space in a state where the non-Si non-C gas composed of gas is separated from each other. The gas jetted from the outlet into the film forming space, and the gas mixed into the film forming space is decomposed and activated by the plasma generated by the antenna electrode connected to a high-frequency power source. A Cat-PECVD method in which a film is deposited on a substrate disposed opposite to the antenna electrode, and the antenna electrode is provided with a cooling mechanism for cooling the antenna electrode And it features.
[0040]
In particular, the antenna electrode is rod-shaped or U-shaped, the thermal catalyst is installed in a hollow portion of the antenna electrode, and a plurality of antenna electrodes are arranged in parallel to form an array-shaped antenna electrode Forming a unit, the substrate is disposed on both sides of the arrayed antenna electrode unit, and a substrate heater is disposed on the surface of the substrate opposite to the surface facing the arrayed antenna electrode unit A plurality of the arrayed antenna electrode units exist in one film forming chamber, and each unit is arranged so that the respective array surfaces are parallel to each other. It is an apparatus configuration capable of simultaneous film formation on both sides, the gas to be introduced separately is ejected from different antenna electrodes, Preliminary the material-based gas introduction path and / or the the non-Si non-C-based gas introduction path introducing a gas for doping in the membrane, and wherein, respectively.
[0043]
Further, the present invention is a film processing system in which a plurality of processing chambers including at least one chamber for realizing the Cat-PECVD method are connected.
[0044]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below in detail with reference to the drawings schematically shown. FIG. 1 is a cross-sectional view showing an example of an antenna electrode that is entirely cylindrical and provided with a cooling mechanism in an apparatus for realizing the Cat-PECVD method of the present invention. FIG. 2 is an overall view showing an example of an apparatus for realizing the Cat-PECVD method of the present invention, in which a thermal catalyst is incorporated when the film-forming surface of a flat substrate is oriented in a direction perpendicular to the paper surface. It is sectional drawing in an antenna electrode position. FIG. 3 shows an example in which antenna electrodes are arranged in an array, and is a cross-sectional view when the film-forming surface of the substrate is oriented in a direction parallel to the paper surface (in order to show the presence of the substrate, the arrayed antenna electrodes Only a part of the unit is shown, and details of the end structure of the antenna electrode are omitted: see FIG. 1 and FIG. 2 for details). FIG. 4 is a cross-sectional view of the arrayed antenna electrode as viewed from the central axis direction. FIG. 5 is a cross-sectional view showing a detailed structure of a conventional antenna electrode. FIG. 6 is a perspective view showing a three-dimensional structure of the antenna electrode.
[0045]
In these figures, reference numeral 101 denotes an inlet for a raw material gas containing a gas containing Si and / or C in the molecular formula (source gas supply port), and 102 denotes a non-Si non-C consisting of a gas not containing Si and C in the molecular formula System gas introduction port (non-Si non-C system gas supply port), 103 is a thermal catalyst, 104 is a heating power source for the thermal catalyst 103, 105 is plasma, and 106a is an antenna electrode (thermal contact) with a built-in thermal catalyst. Antenna electrode with built-in medium), 106b is an antenna electrode without a built-in thermal catalyst (antenna electrode without built-in thermal catalyst), 107a and 107b are high-frequency power supplies, 108a and 108c are phase converters, 108b and 108d are power distributors, 109 109a and 109b are substrates for film formation, 110 is a heater for heating the substrate, and 111a is a gas jet provided on the antenna electrode 106a with a built-in thermal catalyst. , 111b is a gas outlet provided in the antenna electrode 106b with no built-in thermal catalyst body, 112 is an insulating member for electrical insulation, 113 is a chamber (film forming chamber) constituting a film forming space, and 114a and 114b are antennas A hollow portion 211 provided inside the electrode is a cooling pipe that is provided in the antenna electrode and realizes a cooling mechanism for cooling the antenna electrode. The cooling pipe 211 is configured so that, for example, as shown in the drawing, pipes are provided on the outer circumference and the inner side of all the antenna electrodes (not shown), and a cooling liquid or gas flows in the pipe. Therefore, as long as the heated antenna electrode is disposed so as not to hinder the generation of the plasma 105 and can be actively cooled, the arrangement location is not limited.
[0046]
As described above, the Cat-PECVD method of the present invention has a molecular formula Si heated to the molecular system heated by the source gas containing the gas containing Si and / or C in the molecular formula and the thermal catalyst 103 disposed in the gas introduction path. And the non-Si non-C gas composed of a gas not containing C are separated from each other, and the hollow portions (114b, 114a) of the antenna electrodes (106b, 106a) having a hollow structure installed in the film forming space are separated. ) Through a plurality of gas outlets provided in the antenna electrode, and the mixed gas injected into the film forming space is connected to a high frequency power source (107a, 107b). Decomposed and activated by plasma generated by the antenna electrode, and a film is deposited on the substrate 109 disposed opposite to the antenna electrode in the film forming space. To.
[0047]
Although illustration is omitted, the chamber 113 is evacuated by a vacuum pump. At this time, as the vacuum pump, it is desirable to use a dry pump such as a turbo molecular pump in order to suppress contamination of impurities from the exhaust system into the film formed on the substrate. At this time, the ultimate vacuum is at least 1 × 10 ^-3 1 x 10 with Pa or less ^-Four If it is set to Pa or less, it is more desirable. The pressure during film formation is in the range of about 10 to 1000 Pa. The temperature of the substrate 109 by the substrate heating heater 110 is set to a temperature condition of 100 to 400 ° C., preferably 150 to 350 ° C.
[0048]
Hereinafter, each part will be described in detail.
= Electrode shape =
First, as the shape of the antenna electrode, a rod shape, a U-shape or the like can be selected. Specifically, the rod-shaped one is the simplest, and is disclosed in, for example, Japanese Patent Application Laid-Open Nos. 1-47475, 1-270382 and 2001-274101. The U shape is disclosed in Japanese Patent Laid-Open No. 4-21781.
[0049]
Here, the reason why the antenna type electrode is used instead of the conventional flat plate type electrode is as follows. In general, the relationship between the frequency f of the high frequency power supply and the wavelength λ is given by λ = v / f in the plasma. Here, v is the propagation speed of the electromagnetic wave in the plasma, which is smaller than the speed c (light speed) of the electromagnetic wave in the vacuum, so that λ is at most c / f or less. On the other hand, if the length L of one side of the square electrode is a typical characteristic length as the size of the plasma generating electrode, if λ >> L, the electromagnetic interference effect does not occur and uniform plasma is generated. It is possible to form a film with a uniform film thickness and a uniform film quality. For example, when f = 13.5 MHz, λ is about 22 m at the maximum, and it can be seen that the interference effect does not become a problem with a plasma generation electrode of 1 m square size.
[0050]
However, when the frequency f of the high frequency power source is increased and λ / 4 becomes a value of about L or less, the interference effect cannot be ignored. For example, when f = 60 MHz, λ / 4 is 1.25 m at the maximum, and an interference effect occurs in a simple flat-plate plasma generating electrode of 1 m square size, and a uniform electromagnetic field distribution, that is, uniform plasma generation. I can't see.
[0051]
For this reason, in large-area film formation of about 1 m square size or more in a region where the frequency of the high-frequency power supply is equal to or higher than the VHF band, an antenna-type electrode is used instead of the flat-plate-type plasma generation electrode, and a phase control technique described later The development of technology for making the plasma generation uniform by introducing is progressing, and this can also be used in the Cat-PECVD method.
[0052]
In addition, the cross-sectional shape parallel to the direction perpendicular to the major axis direction of the antenna electrode may be either circular or rectangular. However, when more uniform film forming characteristics are particularly required, a more uniform plasma generation in a plane is possible. It is preferable to use a square that can realize
= Thermal catalyst installation position =
Next, regarding the installation position of the thermal catalyst 103, the most desirable is the inside of the antenna electrode having a hollow structure as shown in FIGS. 1, 2, 3, 4, and 6. Part). By installing the thermal catalyst inside the antenna electrode, the heated and activated non-Si non-C-based gas enters the plasma space generated outside the antenna without excessively damaging its temperature and activity. Since it is fed, the effect on the film formation can be sufficiently maintained. For example, H to non-Si non-C gas ₂ SiH as the raw material gas _Four When using a low hydrogen dilution rate (low H), which was difficult without using a thermal catalyst ₂ / SiH _Four Ratio) and low-frequency power conditions, it is easy to form a crystalline Si film, and it is also easy to form a hydrogenated amorphous Si film with a low hydrogen concentration in the film, which was difficult without using a thermal catalyst. Effect.
[0053]
As described above, the installation position of the thermal catalyst 103 is most desirable inside the hollow antenna electrode, but the above-described effect can be obtained even when installed in the gas path upstream of the hollow antenna. Therefore, when it is particularly difficult to install the thermal catalyst within the hollow antenna electrode, the thermal catalyst can be installed in the gas path upstream of the hollow antenna. In any case, however, it is still desirable to install the thermal catalyst in the antenna electrode in order to maximize the effects of the present invention.
= Array of antenna electrodes =
Next, the antenna electrodes are arranged. The substrate 109 is a plate material or a film material having a certain area such as a substrate such as a solar cell, and the film formation is performed on the surface. As shown in FIGS. 3 and 4, it is desirable to arrange a plurality of these in parallel to form an array antenna electrode unit. Thereby, film formation can be performed uniformly and in a large area.
= Gas separation introduction method =
Next, as a method for separating and introducing the non-Si non-C gas and the raw material gas, the simplest method is when each gas is ejected from a different antenna electrode as shown in FIG. At this time, the thermal catalyst 103 is installed inside the antenna electrode 106a into which the non-Si non-C gas is introduced. Here, when the distance between the antenna electrodes cannot be sufficiently narrowed and there is a possibility that the mixing of the non-Si non-C gas and the raw material gas in the plasma may be insufficient, one antenna electrode may be included. A plurality of independent hollow spaces may be formed so that the non-Si non-C gas and the raw material gas are simultaneously ejected from one antenna electrode through different hollow spaces (not shown). Also at this time, the thermal catalyst 103 is installed in the non-Si non-C gas introduction path.
[0054]
Here, the reason why the raw material gas and the non-Si non-C gas are introduced separately is that only the non-Si non-C gas is desired to be heated by the thermal catalyst. That is, if the raw material gas and the non-Si non-C gas are mixed and introduced, not only the non-Si non-C gas but also the raw material gas is heated by the thermal catalyst disposed in the introduction path. If the temperature of the thermal catalyst is equal to or higher than the decomposition temperature of the raw material gas, the raw material gas is decomposed and activated to form a film on the gas introduction path, and the raw material gas is produced. This is because it is consumed significantly before reaching the membrane space.
= Gas outlet location =
Next, in the case of the antenna electrode 106a in which the thermal catalyst 103 is installed, the gas jet 111a is heated from the thermal catalyst 103 as shown in FIG. It is desirable to arrange the radiation so that it does not reach the film-forming substrate 109a or 109b directly. Thereby, an undesired increase in the film forming surface temperature due to radiation generated from the thermal catalyst can be avoided, and stable control of the film quality can be realized. In the case of the antenna electrode 106b in which the thermal catalyst is not installed, the gas outlet may be at an arbitrary position.
= Arrangement of array antenna electrode unit =
Next, it is desirable that the arrayed antenna electrode unit is arranged vertically so that the array surface is parallel to the direction of gravity. In this way, it is possible to very effectively prevent the powder from adhering to the base 109 during film formation on both surfaces of the arrayed antenna electrode unit as described later. Further, for example, when a glass substrate or the like is used as the base 109, the glass substrate can be transported in a vertical type, so that there is an advantage that the handling becomes very easy without causing a problem of bending of the glass substrate. Of course, in this case, there is also an advantage that the problem of bending of the arrayed antenna electrode unit itself does not occur.
[0055]
As described above, it is desirable to arrange the arrayed antenna electrode unit vertically so that its array surface is parallel to the direction of gravity. Of course, the arrayed antenna electrode unit is arranged so that its array surface is perpendicular to the direction of gravity. The horizontal arrangement is not particularly limited, and the latter horizontal arrangement may be adopted if the problems of array electrode and substrate bending and powder drop adhesion are almost negligible. Absent.
= Substrate arrangement =
Next, it is desirable that the base 109 is disposed on both sides of the arrayed antenna electrode unit (see FIGS. 2 and 4). By doing so, simultaneous film formation on both sides of the arrayed antenna electrode unit is possible, and the productivity of the apparatus can be doubled.
= Substrate heater arrangement =
Next, as shown in FIG. 2, the substrate heater 110 is desirably disposed on both sides of the arrayed antenna electrode unit with the substrate interposed therebetween. That is, it is desirable that a substrate heater is disposed on the surface of the substrate opposite to the surface facing the arrayed antenna electrode unit. By doing so, the temperature of the substrate surface during film formation can be controlled, and high-quality film formation can be realized more easily.
= Number and arrangement of array antenna electrode units =
Next, it is desirable that a plurality of array antenna electrode units are arranged in parallel in one film forming chamber (FIG. 2 shows an example in which three array antenna electrode units are arranged). By doing so, simultaneous film formation by a plurality of arrayed antenna electrode units becomes possible, and considering the simultaneous double-sided film formation by one arrayed antenna electrode unit, for example, two sets of arrayed antenna electrode units are arranged in parallel. If this is done, simultaneous four-sided film formation will be possible, and if three sets are arranged in parallel, six-sided simultaneous film formation (FIG. 2 shows this case). As described above, if the number of parallel arrangements of the arrayed antenna electrode units is increased, the productivity as a film forming apparatus can be increased to several times or more at once. This is impossible with a conventional parallel plate type PECVD apparatus.
= Power supply method =
Next, as for a method of supplying power to the antenna electrode 106a or 106b, for example, as shown in FIG. 3, high-frequency power from the high-frequency power source 107a or 107b may be distributed by the power distributor 108b or 108d and transmitted. Alternatively, a high frequency power source may be provided for each antenna electrode (not shown). Here, the number of high-frequency power sources and the number of distributions do not necessarily need to match, and it is usually effective to reduce equipment costs if more power distribution is realized with a smaller number of high-frequency power sources. Here, if one high frequency power supply cannot distribute and supply all the necessary high frequency power, a plurality of high frequency power supplies can be prepared and distributed as necessary.
= Phase control =
Next, in order not to generate a non-uniform plasma distribution due to unnecessary interference effects (strengthening and weakening), it is desirable that the phases of the high-frequency power be different between at least adjacent electrodes. This can be realized by using the phase converter 108a or 108c, but the feeding points to the adjacent antenna electrodes of the arrayed antenna electrode unit are positioned in the mutually opposing directions as shown in FIG. 3, for example. The same effect can also be realized by arranging them, and a more uniform large area plasma can be generated by using both in combination.
= High-frequency power supply method =
As another method for facilitating the formation of a uniform film thickness and uniform film quality over a large area, a plurality of high-frequency electric powers having different frequencies are superimposed on the antenna electrodes 106a and 106b, so that different spaces are formed. There is a method of superposing a plurality of plasmas having a specific density distribution. Thereby, since the plasma density distribution can be made more uniform, a uniform film can be formed over a large area on the substrate.
[0056]
As another method, there is a method in which high-frequency power having a different frequency is input to each adjacent antenna electrode. For example, the frequency of the high-frequency power sources 107a and 107b in FIG. In this way, the plasma density distribution can be made more uniform due to electromagnetic interaction between adjacent electrodes, so that a uniform film can be formed over a large area on the substrate.
[0057]
As another method, the high frequency power frequency is fluctuated and modulated in time, the spatial density distribution of the plasma is fluctuated in time, and the time average is taken, resulting in uniform film formation. There is.
[0058]
Furthermore, if high-frequency power is intermittently supplied to the antenna electrodes 106a and 106b, for example, by pulse-modulating the plasma, the generation and growth of powder can be suppressed compared to the case of continuous plasma generation. It may be effective for improvement.
= High frequency power supply frequency =
Next, in the Cat-PECVD method and apparatus of the present invention, the antenna electrodes 106a and 106b for generating plasma are connected to the high frequency power sources 107a and 107b, and the frequency of the high frequency power sources 107a and 107b is 13.56 MHz or higher. However, the effect of the present invention, that is, the effect on the large-area uniform film thickness / homogeneous film-forming is remarkable in the high frequency region of 27 MHz or higher (so-called VHF band or higher).
[0059]
That is, in the conventional flat electrode, as described above, it is possible to realize a large-area film formation with a uniform film thickness of about 1 m square size and a uniform film quality without relatively difficulty up to about 27 MHz. According to the present invention, even in a high frequency region of 27 MHz or higher, a large area uniform film thickness / homogeneous film forming characteristic that is markedly superior to that of the prior art can be obtained.
[0060]
As a high frequency frequency in the VHF band, an arbitrary value can be selected as a continuous amount, and it is desirable to select an optimum frequency according to the electrode size and shape, but usually 40 MHz and 60 MHz are often used industrially. It is sufficient to use frequencies such as 80 MHz and 100 MHz.
[0061]
Here, the higher the frequency of the high-frequency power supplies 107a and 107b, the higher the electron density in the plasma, so that the decomposition activation rate of the raw material gas increases and the film forming speed becomes faster. Moreover, H is used as a non-Si non-C gas. ₂ When a gas is used, the generation rate of atomic hydrogen is increased, so that the crystallization promoting effect can be obtained more remarkably. Therefore, a crystalline Si film can be obtained even under high-speed film forming conditions.
[0062]
Furthermore, in the present invention, since the activation of the non-Si non-C gas can be further promoted using the thermal catalyst, H as the non-Si non-C gas is used. ₂ When a gas is used, the effect of promoting crystallization is further increased in addition to the above-described effect of VHF itself, and a high-quality crystalline Si film can be obtained even under further high-speed film forming conditions. In particular, when forming a hydrogenated amorphous Si film, a film having a lower hydrogen concentration can be formed, and a hydrogenated amorphous Si film having better light stability than that obtained by the conventional PECVD method alone can be obtained.
[0063]
Note that the frequency of the high frequency power supply need not be limited to the VHF band up to about 100 MHz, and can be used up to a higher frequency in the UHF band or microwave region.
= Thermal catalyst =
Next, at least the surface of the thermal catalyst 103 is made of a metal material in order to cause the current to flow through it to be heated and heated by the Joule heat generation to function as a thermal catalyst, but this metal material is more preferable. Is preferably made of a metal material mainly composed of at least one of Ta, W, Re, Os, Ir, Nb, Mo, Ru, and Pt, which are high melting point metal materials. Further, as the thermal catalyst 103, a metal material as described above is usually used in a wire shape, but is not limited to a wire shape, and a plate shape or a mesh shape may also be used. it can. In addition, when the metal material which is a thermal catalyst body material contains an undesirable impurity for film formation, before using the thermal catalyst body 103 for film formation, the temperature is higher than the heating temperature at the time of film formation in advance. Preheating for several minutes or more is effective in reducing impurities.
= Power source for heating the thermal catalyst =
As the heating power source 104 for the thermal catalyst 103, it is usually easy to use a DC power source, but there is no problem even if a low frequency AC power source that does not generate plasma is used. When a DC power source is used, DC power can be intermittently supplied to the thermal catalyst 103 in order to control the degree of heating or decomposition / activation of the non-Si non-C gas, as will be described later.
= Activation of non-Si non-C-based gas =
Next, the non-Si non-C-based gas is heated by the thermal catalyst 103 and guided to the plasma space 105, but a part of the non-Si non-C gas is decomposed and activated by the thermal catalyst 103. Proportional. For example, H ₂ Depending on the pressure of the gas, the generation of atomic hydrogen due to the decomposition reaction becomes prominent when the temperature of the thermal catalyst exceeds about 1000 ° C. As described above, this atomic hydrogen acts very effectively on the crystallization promotion of the Si film. The secondary effect is that the thermal catalyst is used even under temperature conditions where the thermal catalyst temperature is about 1000 ° C. or less, the generation of atomic hydrogen is not so remarkable, and the crystallization promotion effect cannot be expected so much. Since the high-order silane formation reaction is suppressed by the gas heating effect, it is still effective for the formation of a high-quality hydrogenated amorphous silicon film. However, in order to obtain the above effect, it is desirable that the temperature of the thermal catalyst is at least 100 ° C., more preferably 200 ° C. or more. The effect of gas heating can be acquired more notably by setting it as 200 degreeC or more. The maximum temperature of the thermal catalyst body is 2000 ° C. or less, more preferably 1900 ° C. or less. If the temperature exceeds 1900 ° C., problems such as degassing of impurities from the catalyst body and peripheral members and evaporation of the material of the catalyst body itself will start to occur.
= Activation amount adjustment method =
Where H described above ₂ Examples of methods for realizing the method other than controlling the degree of heating or decomposition / activation of the non-Si non-C gas represented by the above-described thermal catalyst temperature include the following.
[0064]
The first method is to control the surface area of the thermal catalyst 103. According to this, it is possible to control the degree of heating, decomposition, or activation of the non-Si non-C based gas while maintaining the temperature of the thermal catalyst 103 at a certain temperature or higher without lowering the temperature. For example, when a linear catalyst is used as the thermal catalyst 103, the surface area of the thermal catalyst 103 can be controlled by selecting the length and diameter of the thermal catalyst 103 and the number installed in one antenna electrode. . In particular, when a plurality of thermal catalyst bodies 103 are installed in one antenna electrode (not shown), the number of thermal catalyst bodies to be heated can be determined as necessary if they can be heated independently. The degree of heating or decomposition / activation of the non-Si non-C gas can be changed stepwise.
[0065]
The second method is a method of heating the thermal catalyst 103 intermittently or periodically. Specifically, the thermal catalyst 103 can be heated periodically by using a mechanism that intermittently supplies power from the heating power source 104 in a pulsed manner or by using a low-frequency AC power source. As a result, the reaction time between the non-Si non-C gas and the thermal catalyst 103 per unit time can be controlled continuously, so that the degree of heating, decomposition or activation of the non-Si non-C gas can be controlled continuously. Can do.
[0066]
In the third method, the diameter of the non-Si non-C gas outlet 111a and the diameter of the raw material gas outlet 111b are separately designed and adjusted, or the total number of non-Si non-C gas outlets 111a and the raw material system are adjusted. The total number of gas outlets 111b is designed and adjusted separately. The reduction in the diameter or the reduction in the total number of the nozzles at the non-Si non-C gas outlet 111a reduces the amount of non-Si non-C gas that has been heated, decomposed, or activated, and is injected into the plasma space 105. The enlargement of the diameter or the increase of the total number of the nozzles at the system gas outlet 111b can increase the amount of the non-Si non-C gas heated or decomposed / activated into the plasma space 105.
[0067]
The fourth method is to add a non-Si non-C based gas introduction path (not shown) in which a thermal catalyst is not disposed in the gas introduction path, and a non-Si non-C based gas flow rate through the thermal catalyst 103; This makes it possible to independently control the non-Si non-C gas flow rate that does not pass through the thermal catalyst. That is, there are a plurality of non-Si non-C gas introduction paths, and at least one non-Si non-C gas is guided to the plasma space without being heated by the thermal catalyst. As a result, the heated or decomposed / activated non-Si non-C based gas and the non-heated non-Si non-C based gas can be mixed at an arbitrary gas flow ratio, so that they are released into the plasma space 105. The density of the non-Si non-C gas heated or decomposed / activated can be continuously changed. Here, the non-Si non-C gas introduction path that is not heated may be merged with the raw material gas introduction path, and the introduction structure becomes simpler when merged in this way.
= Gas path material =
Next, at least a part of the surface of at least one of the inner wall of the gas pipe and the inner wall of the hollow antenna electrode in the non-Si non-C-based gas introduction path is made of a material containing at least one of Ni, Pd, and Pt. It is desirable. These metal elements are for example H ₂ Since there is a catalytic action that promotes dissociation of gas molecules such as the above, it is possible to reduce the probability that the decomposed / activated non-Si non-C-based gas is recombined on the surface of the member and deactivated.
= Gas heating =
Next, it is desirable that a thermal catalyst is also provided in the raw material gas introduction path (not shown) in order to promote the gas heating effect. However, the temperature of the thermal catalyst body is controlled to be equal to or lower than the temperature at which the raw material gas is decomposed so that the raw material gas is not decomposed by the thermal catalyst body. For example, SiH as the source gas _Four When using, the temperature is 500 ° C. or lower, preferably 400 ° C. or lower.
[0068]
In addition, as another method for promoting the gas heating effect, there is a method of installing a heater on the wall surface of the film forming chamber. That is, in the conventional method in which the wall surface of the film forming chamber is not heated in particular, a high-order silane formation reaction (exothermic reaction) tends to occur on the wall surface of the film forming chamber at a low temperature. In contrast to the cause of powder generation, this method actively heats the inner walls of the film formation chamber, which suppresses the high-order silane generation reaction, which is an exothermic reaction, and reduces the amount of powder generated. it can. Here, when the raw material gas contains a gas containing Si in the molecular formula, the temperature of the heater is set to 500 ° C. or lower, desirably 400 ° C. or lower. Thereby, since the thermal CVD reaction (film formation reaction) on the heater surface is sufficiently suppressed, waste of the raw material gas at this portion can be suppressed.
= Doping gas introduction method =
Next, when supplying doping gas, doping gas can be introduce | transduced into a source gas introduction path | route and / or a non-Si non-C type | system | group gas introduction path | route. At this time, the p-type doping gas is B ₂ H ₆ Etc., and the n-type doping gas is PH _Three Etc. can be used.
= Electric circuit =
It is desirable to install a pass capacitor (not shown) as high-frequency blocking means in the circuit of the catalyst body heating power source 104. As a result, entry of high-frequency components from the high-frequency power source can be prevented, and stable film formation can be realized more reliably.
= Substrate shape =
As the base 109, for example, in the case of a device such as a solar battery, a flat plate such as a glass substrate, or a film such as a metal material or a resin material can be used, and a device such as a photosensitive drum can be used. In this case, a non-flat plate such as a cylindrical shape can be used.
= Cooling method of antenna electrode =
Next, the antenna electrode of the present invention has a cooling mechanism for actively cooling the antenna electrode. As the cooling mechanism, for example, a cooling pipe 211 as shown in FIG. 1 may be provided to the antenna electrode. With such a configuration, a part of the high-frequency power input to the antenna electrode for the purpose of generating plasma inevitably becomes thermal energy, thereby reducing the degree to which the antenna electrode is heated. If this cooling mechanism is not provided, the antenna electrode is heated by the thermal energy, resulting in a non-constant temperature distribution on the surface of the antenna electrode, resulting in non-uniform plasma generation density, uniform film thickness formation Film formation becomes difficult. In addition, by doing so, it is possible to suppress the heating and heating of the antenna electrode due to the thermal radiation from the thermal catalyst body, which was a problem inherent to the antenna electrode incorporating the thermal catalyst body, which is a feature of the present invention. Also, it becomes easy to maintain the uniformity of plasma generation, and at the same time, the problem of deformation due to heating of the antenna electrode can be solved.
= Membrane =
According to the Cat-PECVD method of the present invention, it is possible to form a high-speed and high-quality film with high uniformity in film thickness and film quality over a large area. The effects of the present inventors are disclosed in Japanese Patent Application Nos. 2001-293031 and 2002-38686 by the present inventors). Specifically, the effects of the Si-based film or C-based film described below are remarkably exhibited. .
[0069]
In the first example, the gas containing Si in the molecular formula is included in the source gas, but the gas containing C in the molecular formula is not included, and the gas containing H in the non-Si non-C gas is used. ₂ This is a Si-based film formed by the inclusion of. Specifically, for example, the source gas is SiH. _Four H for non-Si non-C gases ₂ Can be used to form a high-quality hydrogenated amorphous silicon film or a high-quality crystalline silicon film at a high speed with high uniformity in film thickness and film quality over a large area for the reasons already described above. .
[0070]
According to the method of the present invention, the hydrogen concentration in the hydrogenated amorphous silicon film can be made 15 atomic% or less. More preferably, it can be 10 atomic% or less, and more preferably 5 atomic% or less. This can greatly reduce the photodegradation problem of the hydrogenated amorphous silicon film, which has been a problem for many years. When used in a battery, high stabilization efficiency can be obtained.
[0071]
Further, according to the method of the present invention, the hydrogen concentration in the crystalline silicon film can be made 10 atomic% or less. More preferably 5 atomic% or less, and even more preferably 3.5 atomic% or less, whereby the deterioration of characteristics over time due to the post-oxidation phenomenon at the crystal grain boundaries described in the examples of solar cell embodiments described later. Can be reduced. That is, when the hydrogen in the film is 5 atomic% or less, the deterioration rate with time is about several percent or less, and when the hydrogen concentration in the film is 3.5 atomic% or less, the deterioration rate with time is almost zero.
[0072]
In the second example, the source gas contains a gas containing Si in the molecular formula and a gas containing C in the molecular formula, and the non-Si non-C gas contains H. ₂ Is a Si—C-based film formed by the inclusion. Specifically, for example, the source gas is SiH. _Four And CH _Four H for non-Si non-C gases ₂ For this reason, a high-quality hydrogenated amorphous silicon carbide film or a high-quality crystalline silicon carbide film must be formed at high speed and with a high uniformity of film thickness and film quality over a large area. Can do.
[0073]
In the third example, the raw material gas contains a gas containing Si in the molecular formula, and the non-Si non-C gas contains H. ₂ A gas containing N in the molecular formula is a Si—N-based film formed by being included in at least one of a source gas and a non-Si non-C gas. Specifically, for example, the source gas is SiH. _Four H for non-Si non-C gases ₂ NH as a gas containing N _Three For this reason, a high-quality hydrogenated amorphous silicon nitride film or a high-quality crystalline silicon nitride film must be formed at a high speed and with a uniform film thickness and film quality over a large area. Can do.
[0074]
A fourth example is a Si—O-based film formed by including a gas containing Si in the molecular formula in the source gas and a gas containing O in the molecular formula in the non-Si non-C gas. . Specifically, for example, the source gas is SiH. _Four And H if necessary ₂ For non-Si non-C based gases ₂ And if necessary, if He or Ar is used, high-quality amorphous silicon oxide film or high-quality crystalline silicon oxide film can be formed at high speed and with high uniformity of film thickness and film quality over a large area for the reasons already mentioned above. Can be formed.
[0075]
In the fifth example, the source gas contains a gas containing Si and a gas containing Ge in the molecular formula, and non-Si non-C gas contains H. ₂ Is a Si—Ge-based film formed by the inclusion of. Specifically, for example, the source gas is SiH. _Four And GeH _Four H for non-Si non-C gases ₂ For this reason, a high-quality hydrogenated amorphous silicon germanium film or a high-quality crystalline silicon germanium film must be formed at high speed and with a high film thickness and film quality uniformity over a large area. Can do.
[0076]
In the sixth example, the source gas contains a gas containing C in the molecular formula, and the non-Si non-C gas contains H. ₂ It is a C-type film | membrane formed by being included. Specifically, for example, the raw material gas is CH _Four And if necessary, a small amount of O ₂ H for non-Si non-C gases ₂ Can be used to form a high-quality amorphous carbon film or a high-quality crystalline carbon film at a high speed and with high uniformity in film thickness and film quality over a large area. Specifically, a diamond film or a diamond-like carbon film can be formed.
= Thin film device =
Next, when the film formed by the Cat-PECVD method of the present invention is used for a thin film device, the following thin film device can be produced with high performance and low cost.
[0077]
A first example of a thin film device is a photoelectric conversion device. If a film by the Cat-PECVD method of the present invention is used for a photoactive layer, high-performance characteristics can be realized at high speed, that is, at low cost. In particular, in a solar cell that is representative of a photoelectric conversion device, a high-efficiency and low-cost thin-film solar cell is manufactured by fully utilizing the high-speed, high-quality, and large-area film-forming characteristics of the Cat-PECVD method of the present invention. be able to. Of course, the same effect can be obtained with a device having a photoelectric conversion function such as a photodiode, an image sensor, or an X-ray panel.
[0078]
The second device example is a photoreceptor device. If the Cat-PECVD film of the present invention is used for the photoreceptor layer, high-performance characteristics can be realized at high speed, that is, at low cost. In particular, when used for a silicon-based film in a photosensitive drum, a relatively thick silicon-based film ranging from several μm to several tens of μm can be formed with high quality in a short time, which is very effective in reducing the manufacturing cost.
[0079]
A third device example is a display device. If a film by the Cat-PECVD method of the present invention is used as a driving film, high-performance characteristics can be realized at high speed, that is, at low cost. In particular, when used for an amorphous silicon film or a polycrystalline silicon film in a TFT which is a representative example of a large area device next to a solar cell, it is very effective in reducing the manufacturing cost for the same reason as described in the solar cell. In addition to the TFT, a similar effect can be obtained even in an apparatus having a display function such as an image sensor or an X-ray panel.
= Device (see FIG. 7) =
The film processing system for realizing the Cat-PECVD method of the present invention is a film processing system comprising a plurality of vacuum chambers having at least one film forming chamber capable of realizing the above manufacturing method.
[0080]
Here, the plurality of vacuum chambers include at least a p-type film forming film forming chamber, an i-type film forming film forming chamber, and an n-type film forming film forming chamber, and at least an i-type film forming film forming chamber. It is desirable that the chamber is a film forming chamber capable of realizing the Cat-PECVD method of the present invention.
[0081]
Further, it is desirable that at least one of the plurality of vacuum chambers is a film forming chamber capable of realizing the Cat-CVD method. This enables high-speed and high-quality film formation of a hydrogenated amorphous silicon film by, for example, the Cat-CVD method. For example, a hydrogenated amorphous silicon film can be used for the photoactive layer of the top cell of a tandem solar cell. For example, the degree of freedom in combination when forming a multilayer film can be increased. It is known that a hydrogenated amorphous silicon film by a Cat-CVD method can have a lower hydrogen concentration than that by a PECVD method, and it is possible to realize a smaller optical bandgap characteristic having a more excellent light absorption characteristic. it can. In addition, there is an advantage that the photodegradation characteristics, which has been a problem for many years for hydrogenated amorphous silicon films, can be kept low.
[0082]
Further, it is desirable that at least one of the plurality of vacuum chambers is a film forming chamber capable of realizing the PECVD method. As a result, for example, it is possible to realize film deposition on a film surface that is vulnerable to the reduction action of atomic hydrogen, such as an oxide transparent conductive film, under conditions that suppress this reduction action as much as possible. be able to.
[0083]
In addition, it is desirable that the plurality of vacuum chambers include at least a front chamber for the purpose of preventing the film forming chamber from being opened to the atmosphere, and further, if the plurality of vacuum chambers include at least a front chamber and a rear chamber, productivity can be improved. More desirable above. In addition, it is desirable for improving productivity to include at least heating chambers in the plurality of vacuum chambers.
[0084]
The plurality of vacuum chambers can be arranged such that the plurality of vacuum chambers are continuously connected in a line, or the plurality of vacuum chambers are arranged in a star shape so as to be connected to at least one core chamber. You can also
[0085]
Here, it is desirable that the film forming chamber be a vertical type in which a substrate such as a glass substrate is processed into a vertical type. By adopting the vertical type, it becomes difficult to be affected by the falling and adhering of foreign matters such as powder, which is a problem with the horizontal deposition down method, and the uneven temperature on the substrate film surface due to the warping of the substrate that is a problem with the horizontal deposition method. Distribution is unlikely to occur. However, as long as these problems are practically not a problem, it is possible to use a horizontal type.
= Thin film Si solar cell =
Hereinafter, a thin film Si solar cell will be described as a device according to the present invention with reference to FIG. In FIG. 11, 11 is a translucent substrate, 12 is a first transparent conductive film, 13 is a semiconductor multilayer film, 13a is a first semiconductor bonding layer, 13b is a second semiconductor bonding layer, and 14 is a second transparent film. The conductive film, 15a is a metal film serving as a first extraction electrode, and 15b is a metal film serving as a second extraction electrode.
[0086]
First, the translucent substrate 11 is prepared. As the translucent substrate 11, a plate material or a film material made of glass, plastic, resin, or the like can be used.
[0087]
Next, the first transparent conductive film 12 is formed. As a material of the transparent conductive film 12, SnO ₂ A known material such as ITO, ZnO can be used, but when forming a subsequent Si film, SiH _Four And H ₂ Therefore, it is desirable to form a ZnO film having excellent reduction resistance at least as the final surface. As a film forming method, a known technique such as a CVD method, a vapor deposition method, an ion plating method, or a sputtering method can be used. The film thickness of the first transparent conductive film 12 is adjusted in the range of about 60 to 500 nm in consideration of the antireflection effect and low resistance.
[0088]
Next, the semiconductor multilayer film 13 is formed. Here, a tandem type in which a semiconductor film is stacked in a pinpin (or nipnip) configuration will be described as an example, but not limited to a tandem type, a single junction in which a semiconductor film is stacked in a pin (or nip) configuration. Of course, the contents described in this embodiment can be applied to a multi-junction element structure in which a semiconductor film is stacked in a pinpinpin (or nipnipnip) configuration, or a multi-junction element structure having more than that.
[0089]
First, a first semiconductor junction layer 13a including a hydrogenated amorphous silicon film as a photoactive layer is formed. Specifically, it is desirable to have a p-type layer (n-type layer) / photoactive layer / n-type layer (p-type layer) structure (not shown), and the photoactive layer is preferably i-type. In addition, the said description represents the film forming order and means a lower layer / upper layer.
[0090]
Here, as the p-type layer (n-type layer), a crystalline silicon film including a hydrogenated amorphous silicon film or a microcrystalline silicon film can be used. The film thickness is adjusted in the range of about 2 to 100 nm depending on the material. 1 × 10 for doping element concentration ¹⁸ ~ 1x10 ^{twenty one} / Cm ^Three To the extent, practically p ⁺ Type (n ⁺ Type). SiH used during film formation _Four , H ₂ And B which is a doping gas ₂ H ₆ (PH _Three ) And other gases in addition to CH _Four If a proper amount of gas containing C (carbon) such as _x C _1-x A film is obtained, which is very effective for forming a window layer with little light absorption loss, and also effective for reducing dark current components for improving the open circuit voltage. In addition to C, the same effect can be obtained by mixing an appropriate amount of a gas containing O (oxygen) or a gas containing N (nitrogen). Here, as a method for forming the silicon film, a conventionally known PECVD method or Cat-CVD method can be used, but of course, the method of the present invention can also be used.
[0091]
Next, a hydrogenated amorphous silicon film is used for the photoactive layer, and the film thickness is adjusted in the range of about 0.1 to 0.5 μm. The conductivity type is basically i-type, but for the purpose of fine-tuning the internal electric field strength distribution, n ^- Type (p ^- (In practice, it is usual that a non-doped film shows a slight n-type characteristic). Here, as a method for forming the hydrogenated amorphous silicon film, a conventionally known PECVD method or Cat-CVD method can be used, but if the method of the present invention is used, a high-quality hydrogenated amorphous silicon film is used. Since the film can be formed at a high speed, a large area and with high productivity, it is particularly effective for the production of a high-efficiency and low-cost thin-film Si solar cell. Further, according to the present invention, the hydrogen concentration in the film can be reduced to 15 atomic% or less, but more preferably, the hydrogen concentration is 10 atomic% or less, more preferably 5 atomic% or less, which is difficult to realize by the conventional PECVD method. Since a film is obtained, the degree of photodegradation, which is a problem that the hydrogenated amorphous silicon film has had for many years, can be reduced.
[0092]
Finally, for the n-type layer (p-type layer), a crystalline silicon film including a hydrogenated amorphous silicon film or a microcrystalline silicon film can be used. The film thickness is adjusted in the range of about 2 to 100 nm depending on the material. 1 × 10 for doping element concentration ¹⁸ -10 ^{twenty one} / Cm ^Three To the extent, essentially n ⁺ Type (p ⁺ Type). SiH used during film formation _Four , H ₂ And PH as a doping gas _Three (B ₂ H ₆ ) And other gases in addition to CH _Four If a proper amount of gas containing C (carbon) such as _x C _1-x A film can be obtained, a film can be formed with little light absorption loss, and it is also effective in reducing dark current components for improving the open circuit voltage. In addition to C, the same effect can be obtained by mixing an appropriate amount of a gas containing O (oxygen) or a gas containing N (nitrogen). Here, as a method for forming the silicon film, a conventionally known PECVD method or Cat-CVD method can be used, but of course, the method of the present invention can also be used.
[0093]
In order to further improve the junction characteristics, a substantially i-type non-layer is formed between the p-type layer (n-type layer) and the photoactive layer or between the photoactive layer and the n-type layer (p-type layer). Single crystal Si layer or non-single crystal Si _x C _1-x Layers may be inserted. The thickness of the insertion layer at this time is about 0.5 to 50 nm.
[0094]
Next, a second semiconductor bonding layer 13b including a crystalline silicon film as a photoactive layer is formed. Specifically, it is desirable that p-type layer (n-type layer) / photoactive layer / n-type layer (p-type layer) (not shown) and the photoactive layer be i-type.
[0095]
Here, as the p-type layer (n-type layer), a crystalline silicon film including a hydrogenated amorphous silicon film or a microcrystalline silicon film can be used. The film thickness is adjusted in the range of about 2 to 100 nm depending on the material. The doping element concentration is 1 × 1E18 to 1E21 / cm ^Three To the extent, practically p ⁺ Type (n ⁺ Type). SiH used during film formation _Four , H ₂ And B which is a doping gas ₂ H ₆ (PH _Three ) And other gases in addition to CH _Four If a proper amount of gas containing C (carbon) such as _x C _1-x A film is obtained, which is very effective for forming a window layer with little light absorption loss, and also effective for reducing dark current components for improving the open circuit voltage. In addition to C, the same effect can be obtained by mixing an appropriate amount of a gas containing O (oxygen) or a gas containing N (nitrogen). Here, as a method for forming the silicon film, a conventionally known PECVD method or Cat-CVD method can be used, but of course, the method of the present invention can also be used.
[0096]
Next, a crystalline silicon film typified by a microcrystalline silicon film is used for the photoactive layer, and the film thickness is adjusted in the range of about 1 to 3 μm. The conductivity type is basically i-type, but for the purpose of fine-tuning the internal electric field strength distribution, n ^- Type (p ^- Type). At this time, as the film structure, the surface shape after film formation is suitable for optical confinement as an aggregate of columnar crystal grains with (110) plane orientation generated as a result of preferential growth of (110) plane among crystal planes. It is desirable to have a natural concavo-convex structure. Here, as a method for forming the crystalline silicon film, a conventionally known PECVD method or Cat-CVD method can be used, but if the method of the present invention is used, a high-quality crystalline silicon film is formed. Since the film can be formed at high speed, large area, and high productivity, it is particularly effective for the production of a high-efficiency and low-cost thin-film Si solar cell. Further, according to the present invention, a crystalline silicon film having a hydrogen concentration in the film of 10 atomic% or less can be obtained, but a film having a low hydrogen concentration of 5 atomic% or less, more preferably 3.5 atomic% or less is more preferable. Obtainable.
[0097]
Here, in the case of a crystalline silicon film, most of the hydrogen exists in the grain boundary portion, and the bonding state and density of the hydrogen with Si depend on the quality of the grain boundary (the carrier rebound at the grain boundary). Is proportional to the reciprocal of the binding speed). That is, SiH in a state in which two H atoms and two other Si atoms are bonded to one Si atom existing in the grain boundary. ₂ The higher the bond density, the more so-called post-oxidation phenomenon (when the film is exposed to the air atmosphere after film formation, ₂ , CO ₂ , H ₂ Oxygen-containing gas components such as O are likely to diffuse, adsorb, and oxidize at the crystal grain boundaries in the film, resulting in a change in the bonding state of the crystal grain boundaries. Deterioration of the film quality over time (that is, deterioration of characteristics over time) is caused, but when the hydrogen concentration in the film decreases, the SiH at the grain boundary accordingly ₂ Since the bond density is also reduced, the deterioration with time due to the post-oxidation phenomenon described above can be reduced. Specifically, if the hydrogen concentration in the film is 5 atomic% or less, the deterioration rate with time can be suppressed to about several percent or less, and if the hydrogen concentration in the film is 3.5 atomic% or less, the deterioration rate with time is almost zero. can do. As a result, a more efficient solar cell can be manufactured.
[0098]
Finally, for the n-type layer (p-type layer), a crystalline silicon film including a hydrogenated amorphous silicon film or a microcrystalline silicon film can be used. The film thickness is adjusted in the range of about 2 to 100 nm depending on the material. 1 × 10 for doping element concentration ¹⁸ -10 ^{twenty one} / Cm ^Three To the extent, essentially n ⁺ Type (p ⁺ Type). SiH used during film formation _Four , H ₂ And PH as a doping gas _Three (B ₂ H ₆ ) And other gases in addition to CH _Four If a proper amount of gas containing C (carbon) such as _x C _1-x A film can be obtained, a film can be formed with little light absorption loss, and it is also effective in reducing dark current components for improving the open circuit voltage. In addition to C, the same effect can be obtained by mixing an appropriate amount of a gas containing O (oxygen) or a gas containing N (nitrogen). Here, as a method for forming the silicon film, a conventionally known PECVD method or Cat-CVD method can be used, but of course, the method of the present invention can also be used.
[0099]
In order to further improve the junction characteristics, a substantially i-type non-single crystal Si is formed between the p-type layer (n-type layer) and the photoactive layer or between the photoactive layer and the n-type layer (p-type layer). Layers may be inserted. The thickness of the insertion layer at this time is about 0.5 to 50 nm.
[0100]
Next, the second transparent conductive film 14 is formed. As a transparent conductive film material, SnO as a metal oxide material ₂ ITO, ZnO, or the like can be used. As a film forming method, a known technique such as a CVD method, a vapor deposition method, an ion plating method, a sputtering method, and a sol-gel method can be used. Note that the second transparent conductive film 14 can be omitted if high efficiency is not particularly required.
[0101]
Finally, the metal film 15a and the metal film 15b to be the extraction electrode 1 and the extraction electrode 2 are formed. As the metal material, it is desirable to use Al, Ag, etc., which are excellent in conductive characteristics and light reflection characteristics. As the film forming method, known techniques such as vapor deposition, sputtering, ion plating, and screen printing can be used. The electrode pattern can be formed into a desired pattern using a masking method, a lift-off method, or the like. At this time, the film thickness is about 0.1 μm or more. When the adhesive strength between the metal film 15a and the second transparent conductive film 14 or between the metal film 15b and the first transparent conductive film 12 is weak, a metal thin film such as Ti having a thickness of 1 to 1 is used. It is preferable to interpose between the two films at about 10 nm.
[0102]
In addition, when introducing an optical confinement structure for the purpose of further improving the conversion efficiency, a structure as described in Japanese Patent Application No. 2002-78196 can be employed. That is, the maximum height Rmax of the unevenness at the interface between the first transparent conductive film and the semiconductor multilayer film is smaller than the maximum height Rmax of the unevenness at the interface between the second transparent conductive film and the metal film. (At this time, it is desirable that the maximum height Rmax of the unevenness at the interface between the first transparent conductive film and the semiconductor multilayer film is 0.08 μm or less, and the second transparent conductive film and the metal The maximum height Rmax of the unevenness at the interface with the film is preferably 0.05 μm or more), and the maximum height Rmax of the unevenness at the interface between the semiconductor multilayer film and the second transparent conductive film is the first height The maximum height Rmax of the unevenness at the interface between the transparent conductive film and the semiconductor multilayer film is larger than the maximum height Rmax of the unevenness at the interface between the second transparent conductive film and the metal film. Or a light-transmitting structure By forming a structure in which the interface between the conductive substrate and the first transparent conductive film has a concavo-convex structure, an effective optical confinement structure can be formed, so that the photocurrent density increases. And higher conversion efficiency can be realized.
[0103]
As described above, according to the present invention, a high-quality Si thin film can be formed at a high speed, a large area, and with high productivity, so that a highly efficient and low-cost thin-film Si solar cell can be manufactured. .
[0104]
【The invention's effect】
According to the Cat-PECVD method of claims 1 to 9, the molecular system heated by a raw material gas containing a gas containing Si and / or C in the molecular formula and a thermal catalyst disposed in the gas introduction path is Si. And a non-Si non-C gas composed of a gas not containing C are provided in the antenna electrode through the hollow portion of the antenna electrode having a hollow structure installed in the film forming space in a state of being separated from each other. The gas mixed into the film-forming space is ejected from the plurality of gas ejection ports, and the gas mixed into the film-forming space is decomposed and activated by the plasma generated by the antenna electrode connected to a high-frequency power source, A Cat-PECVD method in which a film is deposited on a substrate disposed opposite to the antenna electrode in the film forming space, wherein the antenna electrode is a cooler for cooling the antenna electrode Is provided with the, easier to realize uniform plasma generation, it is possible to perform the deposition of a uniform thickness and homogeneous quality of a large area.
[0106]
According to the film processing system of the tenth aspect, it is possible to manufacture a thin film device with high productivity.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating an antenna electrode for realizing a Cat-PECVD method according to the present invention.
FIG. 2 is a cross-sectional view schematically illustrating an example of an apparatus for realizing a Cat-PECVD method according to the present invention.
FIG. 3 is a diagram schematically illustrating an example of antenna electrode arrangement that realizes the Cat-PECVD method according to the present invention, and is a cross-sectional view of a base film forming surface.
FIG. 4 is a diagram schematically illustrating an antenna electrode arrangement example for realizing the Cat-PECVD method according to the present invention, and is a cross-sectional view seen from the central axis direction of the antenna electrode.
FIG. 5 is a diagram schematically illustrating an example of an antenna electrode with a built-in thermal catalyst body that realizes the Cat-PECVD method according to the present invention, and is a longitudinal sectional view when the central axis direction of the antenna electrode is vertical.
FIG. 6 is a perspective view schematically illustrating an example of an antenna electrode with a built-in thermal catalyst body that realizes the Cat-PECVD method according to the present invention.
FIG. 7 is a configuration diagram schematically illustrating a film processing system according to the present invention.
FIG. 8 is a cross-sectional view schematically illustrating an example of a conventional PECVD apparatus.
FIG. 9 is a cross-sectional view schematically illustrating an example of a conventional Cat-CVD apparatus.
FIG. 10 is a cross-sectional view schematically illustrating an example of a Cat-PECVD apparatus.
FIG. 11 is a cross-sectional view schematically showing an example of a thin film device according to the present invention.
[Explanation of symbols]
11: Translucent substrate
12: First transparent conductive film
13: Semiconductor multilayer film
13a: first semiconductor junction layer
13b: second semiconductor junction layer
14: Second translucent conductive film
15a: Extraction electrode 1
15b: Extraction electrode 2
101: Raw material gas supply port
102: Non-Si non-C gas supply port
103: Thermal catalyst body
104: Thermal catalyst heating power source
105: Plasma
106a: antenna electrode with built-in thermal catalyst
106b: antenna electrode with no built-in thermal catalyst
107: High frequency power supply
108a: Phase converter
108b: Power distributor
109: Substrate
110: Substrate heater
111a: Gas outlet provided in the antenna electrode with a built-in thermal catalyst
111b: Gas outlet provided in the antenna electrode with no built-in thermal catalyst
112: Insulating member
113: Chamber
114a: hollow part (non-Si non-C gas path)
114b: Hollow part (raw material gas path)
211: Cooling pipe

Claims (10)

  Non-Si non-C gas comprising a raw material gas containing a gas containing Si and / or C in the molecular formula, and a gas not containing Si and C in the molecular formula heated by a thermal catalyst disposed in the gas introduction path Are separated from each other through a hollow portion of the antenna electrode having a hollow structure installed in the film forming space and from a plurality of gas outlets provided in the antenna electrode. The gas mixed into the film forming space is decomposed and activated by the plasma generated by the antenna electrode connected to a high-frequency power source, and is disposed opposite to the antenna electrode in the film forming space. A Cat-PECVD method in which a film is deposited on a substrate, wherein the antenna electrode is provided with a cooling mechanism for cooling the antenna electrode.   The Cat-PECVD method according to claim 1, wherein the antenna electrode is rod-shaped or U-shaped.   The Cat-PECVD method according to claim 1, wherein the thermal catalyst is installed in a hollow portion of the antenna electrode.   The Cat-PECVD method according to claim 1, wherein a plurality of the antenna electrodes are arranged in parallel to form an arrayed antenna electrode unit.   The Cat-PECVD method according to claim 4, wherein the substrate is disposed on both sides of the arrayed antenna electrode unit.   The Cat-PECVD method according to claim 4, wherein a substrate heater is disposed on a surface of the substrate opposite to a surface facing the arrayed antenna electrode unit.   A plurality of the arrayed antenna electrode units exist in one film forming chamber, and each unit is arranged so that the respective array surfaces are parallel to each other. The Cat-PECVD method according to claim 4, wherein the Cat-PECVD method is capable of being configured.   The Cat-PECVD method according to claim 1, wherein the raw material gas and the non-Si non-C gas are ejected from different antenna electrodes.   2. The Cat-PECVD method according to claim 1, wherein a gas for doping in the film is introduced into the source gas introduction path and / or the non-Si non-C gas introduction path.   A film processing system in which a plurality of processing chambers including at least one chamber for realizing the Cat-PECVD method according to claim 1 are connected.

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