Abstract:
Provided are a liquid phase growth method of silicon crystal comprising a step of injecting a source gas containing at least silicon atoms into a solvent to decompose the source gas and, simultaneously therewith, dissolving the silicon atoms into the solvent, thereby supplying the silicon atoms into the solvent, and a step of dipping or contacting a substrate into or with the solvent, thereby growing a silicon crystal on the substrate; and a method of producing a solar cell utilizing the aforementioned method. Also provided is a liquid phase growth apparatus of a silicon crystal comprising means for holding a solvent in which silicon atoms are dissolved, and means for dipping or contacting a substrate into or with the solvent, the apparatus further comprising means for injecting a source gas containing at least silicon atoms into the solvent. These provide a liquid phase growth method of a silicon crystal and a production method of a solar cell each having high volume productivity and permitting continuous growth.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a liquid phase growth method of a silicon crystal, a method for producing a solar cell, and a liquid phase growth apparatus and, more particularly, to a liquid phase growth method that permits continuous growth and volume production.  
           [0003]    2. Related Background Art  
           [0004]    Liquid phase growth methods have the advantage of the capability of obtaining crystals with high quality close to stoichiometric compositions because of crystal growth from the quasi-equilibrium state and are used in production of LEDs (light-emitting diodes), laser diodes, and so on, as techniques already established in such compound semiconductors as GaAs. Recently, attempt has been made to utilize the liquid phase growth of Si in order to obtain a thick film (for example, Japanese Patent Application Laid-Open No. 58-89874) and application to solar cells is also under research.  
           [0005]    In the conventional liquid phase growth methods, in general, a solution containing a substance for growth as a solute is cooled into a supersaturated state to deposit the excess solute (the substance for growth) on a substrate. On that occasion, it is necessary to preliminarily dissolve the solute into a solvent until saturated, prior to depositing (or growing) the solute on the substrate. Ordinary methods for dissolving the solute into the solvent include one for preliminarily mixing the solute in an amount enough to saturate at a temperature during the dissolution into the solvent and heating the solvent, and one for heating a large amount of a base material of the solute (over a saturation amount) in contact with the solvent and keeping it at the dissolving temperature to saturate. In the former case, a newly weighed amount of the solute is charged into the solvent or the old solvent is replaced by another solvent in which the solute was preliminarily dissolved, after every completion of growth. In the latter case, the base material of the solute is taken into and out of the solvent before or after the growth and the base material will be used up at last to cause some harm in taking it into or out of the solvent or result in an insufficient dissolved amount. Therefore, the old base material needs to be replaced by a new base material. In either case, time loss occurs, because the apparatus is stopped for supplying the raw material when used up or because the growth is suspended. Therefore, the methods according to the conventional techniques had the problem in terms of volume productivity.  
           [0006]    The present invention has been accomplished as a consequence of intensive and extensive research by the inventors in order to solve the problem in the conventional techniques as discussed above and an object of the present invention is, therefore, to provide a liquid phase growth method that is simple and easy and that has high volume productivity.  
         SUMMARY OF THE INVENTION  
         [0007]    Therefore, the present invention provides a liquid phase growth method of a silicon crystal comprising a step of injecting a source gas comprising at least silicon atoms into a solvent to decompose the source gas and, simultaneously therewith, dissolving the silicon atoms into the solvent, thereby supplying the silicon atoms into the solvent, and a step of dipping or contacting a substrate into or with the solvent, thereby growing a silicon crystal on the substrate.  
           [0008]    Further, the present invention provides a method of producing a solar cell comprising at least a step of forming a silicon layer by liquid phase growth; the method comprising a step of injecting a source gas comprising at least silicon atoms into a solvent to decompose the source gas and, simultaneously therewith, dissolving the silicon atoms into the solvent, thereby supplying the silicon atoms into the solvent, and a step of dipping or contacting a substrate into or with the solvent, thereby growing a silicon crystal on the substrate to form said silicon layer.  
           [0009]    Moreover, the present invention provides a liquid phase growth apparatus of a silicon crystal comprising means for holding a solvent in which silicon atoms are dissolved, and means for dipping or contacting a substrate into or with the solvent, the apparatus further comprising means for injecting a source gas comprising at least silicon atoms into the solvent.  
           [0010]    Further, the present invention provides a liquid phase growth apparatus of a silicon crystal comprising a solvent reservoir for holding a solvent in which silicon atoms are dissolved, a source gas inlet pipe having an opening portion in the solvent held in the solvent reservoir, a wafer cassette for holding a substrate, the wafer cassette being arranged to be freely taken into or out of the solvent held in the solvent reservoir, and a heater.  
           [0011]    Moreover, the present invention provides a liquid phase growth apparatus of a silicon crystal comprising a solvent reservoir and a growth vessel each for holding a solvent in which silicon atoms are dissolved, a pipe for circulating the solvent between the solvent reservoir and the growth vessel, a source gas inlet pipe having an opening portion in the solvent held in the solvent reservoir, a wafer cassette for holding a substrate, the wafer cassette being arranged to be freely taken into or out of the solvent held in the growth vessel, and a heater.  
           [0012]    In addition, the present invention provides a liquid phase growth apparatus of a silicon crystal comprising a solvent reservoir for holding a solvent in which silicon atoms are dissolved, a pipe both ends of which are connected to the solvent reservoir and which has an aperture portion except for the both ends, the pipe being provided for circulating the solvent, a source gas inlet pipe having an opening portion in the solvent held in the solvent reservoir, a holding member for holding a substrate so that the substrate is in contact with the solvent at the aperture portion, and a heater. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 is a schematic sectional view showing an example of the liquid phase growth apparatus according to the present invention;  
         [0014]    [0014]FIG. 2 is a schematic sectional view showing an apparatus that permits the dissolution of silicon and liquid phase growth to be carried out simultaneously, as an example of the liquid phase growth apparatus according to the present invention;  
         [0015]    [0015]FIG. 3 is a schematic sectional view showing an apparatus having a mechanical agitating means, as an example of the liquid phase growth apparatus according to the present invention; and  
         [0016]    [0016]FIG. 4 is a schematic sectional view showing an apparatus in which a substrate is in contact with a solvent at an aperture portion, as an example of the liquid phase growth apparatus according to the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0017]    An example of the liquid phase growth apparatus, which is used in the liquid phase growth method of the present invention, is illustrated in FIG. 1. In FIG. 1 reference numeral  101  designates a wafer cassette,  102  substrates (wafers),  103  a solvent reservoir (crucible),  104  a solvent (melt),  105  a reaction product gas,  106  a source gas inlet pipe,  107  a reactor tube, and  108  an electric furnace (heater).  
         [0018]    Further, numeral  109  denotes gas outlet holes provided in the source gas inlet pipe,  110  a gate valve, and  111  an exhaust port.  
         [0019]    The liquid phase growth method and liquid phase growth apparatus of the present invention will be described referring to FIG. 1. As illustrated in FIG. 1, the solvent reservoir (crucible)  103  made of carbon is filled with the solvent comprised of a metal (hereinafter referred to as metal solvent)  104  and the supply pipe  106  for introduction of the source gas is set along the side wall and bottom surface of the crucible  103 . The wafer cassette  101  carrying the wafers  102  is located above the crucible  103  and is moved vertically to dip the wafers  102  in the metal solvent  104  or lift the wafers  102  up out of the metal solvent  104 , thereby performing growth start operation/growth end operation. The wafer cassette  101  is equipped with a rotating mechanism and the wafer cassette  101  is rotated thereby during growth to uniform thicknesses of a grown film in each wafer surface and thicknesses of grown films among the wafers. The crucible  103 , source gas inlet pipe  106 , and wafer cassette  101  are housed in the reactor tube  107  and are heated by the electric furnace  108  located outside the reactor  107 .  
         [0020]    Specific procedures of the liquid phase growth method of the present invention will be described. First, the unsaturated metal solvent, or the metal solvent  104  after an end of growth is heated to a predetermined temperature (a little higher than the growth temperature) and kept thereat before stabilized. Then the source gas, for example SiH 4 , as a supply source of Si is allowed to flow in the source gas inlet pipe  106 , so that the source gas (SiH 4 ) is injected into the metal solvent through the gas outlet holes  109  opening in the surface of the inlet pipe placed at the bottom surface of the crucible, whereupon the source gas (SiH 4 ) comes into contact with the metal solvent. When SiH 4  is used as the source gas, the SiH 4  coming into contact with the metal solvent soon reacts to be decomposed into Si atoms and H 2  molecules. The Si atoms are dissolved into the metal solvent. At this time, the H 2  molecules thus evolved agitate the metal solvent to promote the dissolution of the Si atoms into the solvent. It can also be contemplated that the solvent is positively agitated with an agitating mechanism (not illustrated) provided separately. After the SiH 4  gas is injected into the metal solvent for a certain time, the flow of the SiH 4  gas is stopped and the metal solvent is slowly cooled by controlling the electric furnace  108 . When the temperature of the metal solvent reaches the growth start temperature, the wafer cassette  101  is moved down to dip the wafers  102  into the metal solvent  104 . Preferably, the wafer cassette  101  is rotated at the rate of several rpm during the growth so as to uniform the thicknesses of grown films. After a lapse of a predetermined growth time, the wafer cassette  101  is moved up out of the metal solvent  104 , thereby terminating the growth. Since in the present embodiment the wafers  102  are mounted at a fixed inclination in the wafer cassette  101 , there remains little metal solvent  104  on the wafer surfaces when they are drawn up out of the metal solvent  104 . There are, however, some cases where a small amount of the metal solvent remains at contact portions (support portions) between the wafers  102  and the wafer cassette  101 . In such cases, the wafer cassette is rotated at the rotational speed of several ten or higher rpm, whereby the remaining metal solvent can be thrown off. Subsequently, the wafer cassette is lifted up into a preliminary chamber (not illustrated) separated from the reactor, in which the wafers are exchanged. Then the above steps are repeated, thereby continuously performing liquid phase growth operations.  
         [0021]    The feature of the present invention is that the source material can be continuously supplied into the solvent with the source gas kept in contact with the metal solvent, which eliminates the time loss due to the exchange of the base material as the solute and the like in the conventional methods, thereby enhancing the volume productivity.  
         [0022]    In the present invention, as the material for the solvent reservoir for storing the metal solvent and as the material for the wafer cassette for supporting the wafers, there is preferably used high-purity carbon or high-purity quartz or the like. Similarly, high-purity carbon or high-purity quartz or the like is also used as a preferred material for the source gas inlet pipe used in the present invention, and high-purity quartz is used as a preferred material for the reactor tube. As the source gas used herein, there are preferably included silanes such as SiH 4 , Si 2 H 6 , . . . , Si n H 2n+2  (n:natural number) and silane halides such as SiH 2 Cl 2 , SiHCl 3 , SiCl 4 , SiH 2 F 2 , and Si 2 F 6 .  
         [0023]    Further, it is preferable to add hydrogen (H 2 ) to the source gas, as a carrier gas or for the purpose of obtaining a reducing atmosphere to promote the crystal growth. The ratio of amounts of the source gas and hydrogen is properly determined depending upon the forming method, type of the source gas, and forming conditions, and the ratio is preferably not less than 1:1000 nor more than 100:1 (based on the ratio of flow rates of introduced gases) and more preferably not less than 1:100 nor more than 10:1.  
         [0024]    As the solvent used in the present invention, a solvent comprised of a metal such as, In, Sn, Bi, Ga, Sb, or the like is preferred. Epitaxial growth is effected by contacting the source gas into the solvent to dissolve the Si atoms thereinto and thereafter slowly cooling the solvent or by providing a temperature difference in the solvent while supplying the Si atoms from the source gas into the solvent.  
         [0025]    The temperature and pressure in the liquid phase growth method employed in the present invention differ depending upon the forming method, the type of the source material (gas) used, etc., but the temperature of the solvent is desirably controlled in the range of not less than 600° C. nor more than 1050° C. when silicon is grown using the solvent of Sn or In, for example. The appropriate pressure is generally in the range of 10 −2  Torr to 760 Torr and more preferably in the range of 10 −1  Torr to 760 Torr.  
         [0026]    When the conductivity type (the p-type/n-type) of Si needs to be controlled, a gas containing a dopant such as P, B, etc. may be introduced into the solvent as the occasion demands. Further, a solar cell element can be formed by growing a silicon crystal by use of indium as a solvent without addition of a particular dopant to form a silicon layer and thereafter forming an n-type layer, for example, by a method for diffusing the dopant into a part of the silicon layer by such a method as thermal diffusion, ion implantation, or the like.  
         [0027]    The growth of a desired crystal by the method of the present invention will be described in more detail using examples, but it should be noted that the present invention is by no means intended to be limited to these examples.  
       EXAMPLE 1  
       [0028]    In the present example an epitaxial layer of Si was grown using the liquid phase growth apparatus of the structure illustrated in FIG. 1. The solvent was In and the source gas was SiH 4 . While the wafer cassette  101  carrying five 5″ Si wafers  102  was kept on standby in a preliminary chamber (not illustrated), the solvent reservoir  103  storing the In solvent  104  was heated by the heater  108  to keep the temperature of the solvent at the constant temperature of 960° C. Here, 5″ means that the diameter of the wafers is 5 inches. Then the wafer cassette  101  kept on standby in the preliminary chamber was guided into the reactor  107  while opening the gate valve  110  and it was held immediately above the solvent reservoir  103 . The gate valve was kept open thereafter. The source gas SiH 4 , together with H 2  gas (in the ratio of gas flow rates: SiH 4 /H 2 =1:1), was injected through the source gas inlet pipe  106  into the In solvent  104  and these gases were kept flowing for 30 minutes. After the flow of the gases was stopped, the heater  108  was controlled so as to start slowly cooling the solvent in the reactor tube  107  at a rate of −1° C./min. When the temperature of the In solvent  104  reached 950° C., the wafer cassette  101  was moved down into the In solvent  104  while being rotated at the rotational speed of 10 rpm. When the wafer cassette  101  was completely dipped in the In solvent  104 , the down movement was stopped and the wafer cassette was held at that position. Then the liquid phase growth was carried on for 60 minutes while rotating the wafer cassette. After that, the wafer cassette  101  was drawn up out of the In solvent  104  and was temporarily stopped immediately above the solvent reservoir  103 . Then the rotational speed was increased up to 120 rpm to throw the partly remaining In off the wafer cassette, and the liquid phase growth was completed.  
         [0029]    Cross sections of the wafers thus obtained were observed with a scanning electron microscope and a transmission electron microscope and it was verified that the epitaxial silicon layers thus grown had a thickness of about 15 μm and also had good crystallinity.  
       EXAMPLE 2  
       [0030]    In the present example an epitaxial layer of Si was grown by using the liquid phase growth apparatus of the structure illustrated in FIG. 3 and using a mechanical agitating means (agitating mechanism) in combination to dissolve the solute in the solvent. The solvent was In and the source gas was Si 2 H 6 . While the agitating mechanism  312  was kept on standby in a preliminary chamber (not illustrated), the solvent reservoir  303  storing the In solvent  304  was heated by a heater  308  to keep the temperature of the solvent at the constant temperature of 960° C. Then the agitating mechanism  312  kept on standby in the preliminary chamber was guided into the reactor tube  307  while opening the gate valve  310  and was held immediately above the solvent reservoir  303 . The gate valve was kept opening thereafter. The source gas Si 2 H 6 , together with H 2  gas (in the ratio of gas flow rates: Si 2 H 6 /H 2 =1:1), was injected through the source gas inlet pipe  306  into the In solvent  304  and the agitating mechanism  312  was moved down into the In solvent  304  while being rotated at a rotational speed of 20 rpm. When the blades  313  of the agitating mechanism were adequately dipped in the In solvent, the down motion was stopped and the agitating mechanism was held at that position. Then the gases were allowed to flow for 30 minutes while agitating the solvent. After the end of the flow of the gases, the agitating mechanism  312  was drawn up to the preliminary chamber and then the wafer cassette  301  carrying five 5″ Si wafers  302  this time was guided from a preliminary chamber (not illustrated) into the reactor tube  307  to be held immediately above the solvent reservoir  303  for 10 minutes. Then the heater  308  was controlled to start slowly cooling the solvent in the reactor tube  307  at a rate of −1.5° C./min. When the temperature of the In solvent  304  reached 950° C., the wafer cassette  301  was moved down into the In solvent  304  while being rotated at a rotational speed of 10 rpm. When the wafer cassette  301  was completely dipped in the In solvent  304 , the down motion was stopped and the wafer cassette  301  was held at that position. Then the liquid phase growth was carried on for 45 minutes while rotating the wafer cassette. After that, the wafer cassette  301  was lifted up out of the In solvent  304  and was temporarily stopped immediately above the solvent reservoir  303 . Then the rotational speed was increased up to 120 rpm, thereby throwing the partly remaining In off the wafer cassette, and the liquid phase growth operation was ended. In FIG. 3 numeral  305  represents the reaction product gas,  309  the gas outlet holes, and  311  the exhaust port.  
         [0031]    Cross sections of the wafers thus obtained were observed with a scanning electron microscope and a transmission electron microscope and it was verified that the epitaxial silicon layers thus grown had a thickness of about 15 μm and also had good crystallinity.  
       EXAMPLE 3  
       [0032]    In the present example an epitaxial layer of Si was grown using the apparatus illustrated in FIG. 2.  
         [0033]    The solvent was Sn and the source gas was SiH 2 Cl 2 . The apparatus illustrated in FIG. 2 has a solvent reservoir  214  made of quartz, a growth vessel  203  in which a wafer cassette  201  carrying substrates (wafers)  202  are dipped, and quartz pipes  209   a ,  209   b ,  210  routed out of one side surface of the solvent reservoir  214 , through the growth cell  203 , and back to another side surface of the solvent reservoir  214 , inside an electric furnace  207 . The pipes  209   a ,  209   b  serve as heat exchangers. The solvent reservoir  214  and heat exchanger  209   b  are further surrounded by a heater block  208  so as to be able to control the temperature independently. Numeral  211  designates a rotor for circulation,  212  a gate valve,  206  a source gas inlet pipe, and  213  an exhaust port. Further, numeral  204  is the solvent and  205  the reaction product gas.  
         [0034]    The solvent  204  of Sn sufficiently purified in a hydrogen atmosphere was charged into the solvent reservoir  214 , growth vessel  203 , and quartz pipes  209   a ,  209   b ,  210  and the temperature inside the electric furnace  207  was kept at the constant temperature of 950° C. The temperature of the solvent reservoir  214  was set 10° C. higher by the heater block  208  than the temperature inside the electric furnace  207  and outside the heater block  208  and the solvent  204  was circulated by the rotor  211 .  
         [0035]    After a lapse of a sufficient time, the wafer cassette  201  carrying five 5″ p +  (100) Si wafers  202  (wafers doped with a relatively large amount of a p-type dopant and having the principal plane of the crystal plane orientation of (100)) was guided from a preliminary chamber (not illustrated) into the growth vessel  203  while opening the gate valve  212  to be held immediately above the Sn solvent  204 . The source gas SiH 2 C 2 , together with H 2  gas (in the ratio of gas flow rates: SiH 2 Cl 2 /H 2 =1:5), was injected through the source gas inlet pipe  206  into the Sn solvent  204  in the solvent reservoir  214  and the gases were kept flowing. After a lapse of 30 minutes, the wafer cassette  201  was moved down into the Sn solvent  204  in the growth vessel  203  while being rotated at a rotational speed of 10 rpm. When the wafer cassette  201  was completely dipped in the Sn solvent  204 , the down movement was stopped and the wafer cassette was held at that position. Then the liquid phase growth was carried on for 60 minutes while rotating the wafer cassette. Then the wafer cassette  201  was drawn up out of the Sn solvent  204  and was temporarily stopped immediately above the Sn solvent  204 . The rotational speed was increased up to 150 rpm to throw the partly remaining Sn off the wafer cassette  201 , and the liquid phase growth operation was terminated.  
         [0036]    Cross sections of the wafers thus obtained were observed with a scanning electron microscope and a transmission electron microscope and it was verified that the epitaxial silicon layers thus grown had a thickness of about 20 μm and also had good crystallinity.  
       EXAMPLE 4  
       [0037]    In the present example an Si layer was grown on polycrystalline Si substrates by use of the apparatus illustrated in FIG. 4. The solvent was In+Ga (Ga content: 0.1 atomic %) and the source gas was SiH 4 . The substrates were each obtained by processing polycrystalline Si formed by the casting method into the width 40 mm, the length 250 mm, and the thickness 0.6 mm, polishing the surface thereof, and thereafter cleaning it.  
         [0038]    The apparatus illustrated in FIG. 4 has a solvent reservoir  414  of carbon, and flat pipes  409   a ,  409   b ,  410  made of carbon in an electric furnace  407 , the pipes  409   a ,  409   b ,  410  being routed so as to leave one side surface of the solvent reservoir  414 , contact a slider  402  on which a plurality of substrates  401  are placed, at an aperture portion  403 , and then return to another side surface of the solvent reservoir  414 . The pipes  409   a ,  409   b  serve as heat exchangers. The solvent reservoir  414  and heat exchanger  409   b  are further surrounded by heater block  408 , so that the temperature can be controlled independently. Numeral  411  denotes the rotor for circulation,  406  the source gas inlet pipe, and  413  the exhaust port. Further, numeral  404  represents the solvent and  405  the reaction product gas.  
         [0039]    The solvent  404  of In+Ga sufficiently purified in a hydrogen atmosphere was charged into the solvent reservoir  414  and flat pipes  409   a ,  409   b ,  410 , and the position of the slider  402  was preliminarily adjusted so that the Si substrates  401  were not in contact with the solvent  404  at the aperture portion  403  of the flat pipe. In that state, the temperature inside the electric furnace  407  was kept at the constant temperature of 950° C. and, at the same time, the temperature of the solvent reservoir  414  was set 10° C. higher by the heater block  408  than the temperature inside the electric furnace  407  and outside the heater block  408 . The solvent  404  was circulated by the rotor  411 . At this time the length of the aperture portion  403  was 100 mm and the circulation rate of the solvent  404  was 40 mm/min. In the present example three Si substrates were placed on the slider.  
         [0040]    Then the source gas SiH 4 , together with the H 2  gas (in the ratio of gas flow rates: SiH 4 /H 2 =1:1), was injected through the source gas inlet pipe  406  into the In+Ga solvent  404  and the gases were kept flowing. After a lapse of 30 minutes, the slider  402  was conveyed at a conveyance speed of 20 mm/min and the liquid phase growth was effected at the aperture portion  403  with the polycrystalline Si substrate  401  being kept in contact with the In+Ga solvent  404 . After all the polycrystalline Si substrates  402  have passed the aperture portion  403 , the conveyance of the slider  401  was stopped and the liquid phase growth was ended.  
         [0041]    Cross sections of the wafers were observed with a scanning electron microscope and a transmission electron microscope, with the result that the Si layers thus grown had a thickness of about 20 μm. The orientations of the Si layers thus grown were inspected by the ECP (Electron Channeling Pattern) method and it was found that they inherited the crystal orientations of the respective grains of the base polycrystalline Si substrates. The present example verified that the crystalline Si layer was able to be grown continuously while conveying the substrates as described above.  
         [0042]    Example 4 described above showed the example using the substrates placed on the slider, but it is also possible, for instance, to bring a web-like substrate having an Si layer attached on a surface thereof into contact with a solvent and convey the substrate in one direction by the roll-to-roll method, thus continuously growing the Si layer.  
       EXAMPLE 5  
       [0043]    In the present example n + /p-type thin-film single-crystal solar cells were made using the liquid phase growth method of the present invention. First, by using the apparatus illustrated in FIG. 1, an epitaxial Si layer was grown on a 500 μm-thick p +  Si wafer (ρ=0.01 Ω·cm) in the similar fashion to Example 1. The epitaxial growth was carried out in the same manner as in Example 1 except that the wafer was different and that the slow cooling rate of the In solvent  104  was −2° C./min.  
         [0044]    The thickness of the Si layer thus grown was evaluated by a step gage or the like to be about 30 μm. Then thermal diffusion of P was effected at a temperature of 900° C. on the surface of the Si layer thus grown with a diffusion source of POCl 3 , thereby forming the n +  layer. The junction depth obtained was about 0.5 μm. The dead layer in the surface of the n +  layer thus formed was wet-oxidized and thereafter removed by etching, thereby obtaining the junction depth of about 0.2 μm with a moderate surface concentration.  
         [0045]    In the last place, by EB (Electron Beam) evaporation, a collector electrode (Ti/Pd/Ag (40 nm/20 nm/1 μm)) and an ITO transparent conductive film (82 nm) were deposited on the n +  layer and a back surface electrode (Al (1 μm)) was deposited on the back surface of the substrate, thereby forming the solar cell.  
         [0046]    The I-V characteristics of the thin-film single-crystal Si solar cells thus obtained were measured under irradiation with light of AM 1.5 (100 mW/cm 2 ). In the cell area of 6 cm 2 , typically an open-circuit voltage 0.6 V, a short-circuit current 33 mA/cm 2 , a fill factor 0.77, and an energy conversion efficiency 15.2% were obtained.  
         [0047]    The present invention has enabled to continuously perform the crystal growth without interruption for supply of a source material in the liquid phase growth method of a silicon crystal. The present invention is suitably applicable to volume production methods of devices required to have some thickness, particularly, to those of solar cells.