Patent Publication Number: US-2012040489-A1

Title: Method, apparatus and system of manufacturing solar cell

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of a U.S. patent application Ser. No. 12/597,169, Filed Oct. 22, 2009, which is a U.S. National Phase patent application of PCT International Application No. PCT/KR2008/002625, filed May 9, 2008, which claims priority of Korean Patent Application 10-2007-0046138 filed on May 11, 2007, the entire contents of which are hereby incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a solar cell, and more particularly, to a method, an apparatus and a system of manufacturing a solar cell that increase productivity and decrease manufacturing costs by simplifying a manufacturing process of a crystalline silicon solar cell. 
     BACKGROUND ART 
     Solar cells are devices that generate electromotive force from minor carriers, which are excited by sunlight, in P-N junction semiconductor devices. Single crystal silicon, polycrystalline silicon, amorphous silicon or compound semiconductors may be used for manufacturing the solar cells. 
     Single crystal silicon has the highest energy-converting efficiency. However, since single crystal silicon is expensive, polycrystalline silicon has been widely used. Recently, thin film solar cells have been widely used because they can be manufactured at small expense by depositing amorphous silicon or compound semiconductors on relatively cheap substrates, such as glass or plastic substrates. 
     Hereinafter, a manufacturing method of a crystalline silicon solar cell according to the related art will be described with reference to  FIG. 1  and  FIGS. 2 to 6 . 
       FIG. 1  is a flow chart of illustrating a manufacturing process of a crystalline silicon solar cell according to the related art.  FIGS. 2 to 6  are views of illustrating cross-sections in steps of manufacturing a crystalline silicon solar cell according to the related art. Referring to  FIG. 1  and  FIG. 2 , at step ST 11 , a crystalline silicon substrate  10  is prepared. Then, damages, which may be caused during a cutting process, are removed by wet etching using acids or bases. Here, the substrate  10  may be p-type, and an n-type substrate may be used. 
     At step ST 12 , a process of texturing a surface of the substrate  10  is performed to increase light absorption. During the texturing process, fine uneven patterns are formed on the surface of the substrate  10 . The uneven patterns, desirably, may have pyramid shapes. In general, the texturing process may be performed by wet etching using acids or bases. Referring to  FIG. 1  and  FIG. 3 , at step ST 13 , n-type dopants are diffused in the p-type substrate  10  to form a P-N junction structure after the texturing process. A thermal diffusion method has been widely used. In the thermal diffusion method, the p-type substrate  10  is disposed in a diffusion furnace under high temperatures, and gases including n-type dopants such as POCl3 or PH3 are provided. Then, the n-type dopants are diffused into the p-type substrate  10 , and an n+ doping layer  12  is formed as shown in  FIG. 3 . 
     A diffusion process of step ST 13  is performed under high temperatures over 800 degrees of Celsius, and residual products such as PSG (phosphor-silicate glass) may be formed on the surface of the substrate  10  due to the high temperatures. By the way, since PSG screens currents of a solar cell, PSG is removed by an etchant to increase an efficiency of the solar cell. Therefore, at step ST 14 , PSG is removed. 
     Alternatively, if p-type dopants including boron (B) are diffused in an n-type substrate, BSG (boro-silicate glass) may be formed. BSG also decreases the efficiency of the electric cell, and BSG should be removed by the same method as PSG. In the meantime, during the diffusion process of step ST 13 , the n+ doping layer  12  is formed on side edges of the substrate  10  too. Leakage currents may be generated between front and back electrodes through the doping layer  12  on the side edges of the substrate  10 . Accordingly, referring to  FIG. 1  and  FIG. 4 , at step ST 15 , to improve the efficiency of the solar cell, the n+ doping layer  12  on the side edges of the substrate  10  is removed. This may be referred to as an edge isolation process. 
     More particularly, the n+ doping layer  12  on the side edges of the substrate  10  may be cut by a laser or may be etched by wet etching or dry etching. The edge isolation process may be performed before testing a completed solar cell. 
     Referring to  FIG. 1  and  FIG. 5 , at step ST 16 , an anti-reflection film  14  is formed on the n+ doping layer  12 . The anti-reflection film  14  may be formed of silicon nitride (SiNx). A SiNx layer not only increases absorption of sunlight but also functions as a surface passivation layer and a hydrogen passivation layer. The SiNx layer is formed by a plasma enhanced chemical vapor deposition (PECVD) method. The SiNx layer may be formed by a sputter method. 
     Referring to  FIG. 1  and  FIG. 6 , at step ST 17 , electrodes are formed on front and back surfaces of the substrate  10  using a conductive material, respectively, after forming the anti-reflection film  14  of SiNx. To do this, conductive paste including aluminum (Al) or silver (Ag) is applied on the front and back surfaces of the substrate  10  by a screen printing method such that a predetermined pattern is formed. Then, a process of sintering the substrate  10  is performed in a furnace under high temperatures. The conductive paste is sintered, and a front electrode  18  and a back electrode  16  are formed on the front and back surfaces of the substrate  10 , respectively, as shown in  FIG. 6 . 
     Specially, if Al paste is applied on the back surface of the p-type substrate  10  and is sintered, Al is diffused into the n+ doping layer  12  during the sintering process, and a p+ layer  13  is formed. If the p+ layer  13  is formed on the back surface of the p-type substrate  10 , a back surface field is induced at the back surface of the substrate  10 . 
     The back surface field makes electrons, which are excited in the p-type substrate  10  by sunlight, move to the back electrode  16  due to and then move to the front electrode  18  without vanishing to contribute to photo currents and increase the efficiency of the solar cell. At step ST 18 , after forming the electrodes, the efficiency of the solar cell is tested and is classified according to results of the test. Before testing, an edge isolation process cutting or etching edge portions of the substrate  10  may be performed to remove leakage currents at edges of the solar cell. Next, a solar cell module is fabricated through a module process for connecting a plurality of completed solar cells. 
     DISCLOSURE 
     Technical Problem 
     However, the above-mentioned manufacturing process of the solar cell have the following several problems. 
     First, wet etching method is widely used during the texturing process of step ST 12 , and it is difficult to obtain uniform surface roughness because etch rates of polycrystalline silicon substrate may differ more than several ten times to several hundred times according to crystal faces. 
     Additionally, in the diffusion process of step ST 13  for forming the P-N junction, since residual products such as PSG or BSG are formed, an additional process of removing the residual products is needed. 
     Moreover, in the diffusion process of step ST 13 , the conductive layer is formed on the edges of the substrate  10 , and thus the edge isolation process is necessarily performed to prevent leakage currents from being induced between the front electrode and the back electrode. 
     The PSG- or BSG-removing process and the edge isolation process put a limitation on improving the productivity of the solar cells. 
     Meanwhile, it is not easy that a manufacturing system of a solar cell is designed as an integrated system or a continuous in-line system because the texturing process is generally performed by wet etching method and the diffusion process is carried out in a furnace under high temperatures. 
     Further, to carry the substrate into the diffusion furnace for performing the diffusion process under high temperatures, the substrate is transferred on the substrate support that is made of quartz. Accordingly, the productivity is lowered due to the transferring time. Moreover, the thermal diffusion process is performed under high temperatures for a long time to obtain an enough junction depth. Thus, there is disadvantage in the productivity and it is difficult to control the junction depth. 
     Technical Solution 
     Accordingly, the present invention is directed to a method of manufacturing a solar cell that simplifies a manufacturing process to increase productivity and reduce manufacturing costs. 
     Another object of the present invention is to provide an apparatus and a system of manufacturing a solar cell that are designed as an integrated structure or an in-line structure to increase productivity and decrease a footprint of the system. 
     Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
     To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a method of manufacturing a crystalline silicon solar cell includes steps of preparing a crystalline silicon substrate, texturing the substrate using plasma to form uneven patterns for increasing light absorption, doping ions in the substrate using plasma to form a doping layer for a P-N junction, heating the substrate to activate the doped ions, forming an anti-reflection film on the doping layer, and forming front and back electrodes on front and back surfaces of the substrate, respectively. 
     In another aspect, an apparatus of manufacturing a crystalline silicon solar cell includes a chamber having a reaction space and including a chamber lid that is grounded, a substrate support in the chamber, a gas distribution plate disposed under the chamber lid and including a plurality of injection holes, a gas supply line passing through the chamber lid and supplying source gases to the gas distribution plate, and an RF power source connected to the substrate support, wherein a substrate loaded on the substrate support is textured to form uneven patterns on a surface of the substrate and then continuously is doped with ions by using plasma to form a P-N junction in the chamber. 
     In another aspect, a system of manufacturing a crystalline silicon solar cell includes a transfer chamber including a substrate-transferring means, a texturing chamber connected to the transfer chamber and texturing a substrate by using plasma to form uneven patterns, a plasma ion doping chamber connected to the transfer chamber and doping the textured substrate with ions by using plasma to form a P-N junction, and a loadlock chamber connected to the transfer chamber and being alternately under vacuum and atmospheric conditions for carrying the substrate in and out. 
     In another aspect, a system of manufacturing a crystalline silicon solar cell includes a loading chamber being alternately under vacuum and atmospheric conditions for carrying a substrate in, a texturing chamber connected to the loading chamber and texturing the substrate by using plasma to form uneven patterns on a surface of the substrate, a plasma ion doping chamber connected to the texturing chamber and doping the textured substrate with ions by using plasma to form a P-N junction, and an unloading chamber connected to the plasma ion doping chamber and being alternately under vacuum and atmospheric conditions for carrying the substrate out. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
     Advantageous Effects 
     According to the present invention, when a crystalline silicon solar cell is manufactured, the texturing process and the ion doping process may be performed in the same chamber or may be performed in respective chambers subsequently arranged. Thus, the footprint of the manufacturing system of a solar cell is decreased, and manufacturing costs are reduced. 
     In addition, since the texturing process is performed using plasma, uniform surface roughness can be obtained regardless of crystal faces of crystalline silicon, and the reproducibility of the texturing process is increased. 
     Moreover, the ion doping process is performed by using plasma under relatively low temperature, and there exist no residual products such as PSG or BSG. Accordingly, a step of removing the residual products is not required, and productivity is considerably increased. Further, because ions normally incident on the substrate are doped, the edge isolation process can be omitted. Therefore, the productivity is considerably increased. 
     Additionally, the texturing process is performed by the dry etching method in place of the wet etching method in the related art, and expensive etchant is not necessary. Accordingly, manufacturing costs are decreased. 
     It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit or scope of the invention. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. 
    
    
     
       DESCRIPTION OF DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. In the drawings: 
         FIG. 1  is a flow chart of illustrating a manufacturing process of a crystalline silicon solar cell according to the related art; 
         FIGS. 2 to 6  are views of illustrating cross-sections in steps of manufacturing a crystalline silicon solar cell according to the related art; 
         FIG. 7  is a flow chart of illustrating a manufacturing process of a crystalline silicon solar cell according to an exemplary embodiment of the present invention; 
         FIGS. 8 to 13  are views of illustrating cross-sections in steps of manufacturing a crystalline silicon solar cell according to an exemplary embodiment of the present invention; 
         FIG. 14  is a view of illustrating an RIE apparatus for texturing according to the present invention; 
         FIG. 15  is a view of illustrating a plasma ion doping apparatus according to the present invention; 
         FIG. 16  is a view of illustrating a manufacturing system of a solar cell according to an exemplary embodiment of the present invention; and 
         FIG. 17  is a view of illustrating a manufacturing system of a solar cell according to another embodiment of the present invention. 
     
    
    
     BEST MODE 
     Reference will now be made in detail to the preferred exemplary embodiments, examples of which are illustrated in the accompanying drawings. 
     A manufacturing method of a crystalline silicon solar cell according to the present invention will be described with reference to  FIG. 7  and  FIGS. 8 to 13 . 
       FIG. 7  is a flow chart of illustrating a manufacturing process of a crystalline silicon solar cell according to an exemplary embodiment of the present invention.  FIGS. 8 to 13  are views of illustrating cross-sections in steps of manufacturing a crystalline silicon solar cell according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 7  and  FIG. 8 , at step ST 110 , a crystalline silicon substrate  100  is prepared. Then, damages, which may be caused during a cutting process, are removed by wet etching using acids or bases. Here, the substrate  100  may be p-type, and an n-type substrate may be used. 
     Referring to  FIG. 7  and  FIG. 9 , at step ST 120 , a process of texturing a surface of the substrate  100  is performed to increase light absorption. In the present invention differently from the related art, the surface of the substrate  100  is textured by reactive ion etching (RIE) using plasma. 
       FIG. 14  is a view of illustrating an RIE apparatus for texturing according to the present invention. In  FIG. 14 , the RIE apparatus  200  includes a chamber  210  having a reaction space, a substrate support  220  in the chamber  210 , a gas distribution plate  230  disposed under and spaced apart from a chamber lid  212 , and a gas supply line  250  passing through the chamber lid  212  and supplying source gases to the gas distribution plate  230 . The gas distribution plate  230  may be connected to a lower portion of the chamber lid  212 . The substrate support  220  and the gas distribution plate  230 , desirably, are formed of anodized aluminum. An exhaust port  214  is set up at a lower part of the chamber  210  to exhaust remaining gases and keep vacuum pressure. The chamber lid  212 , which is electrically connected to the gas distribution plate  230 , is grounded. The substrate support  220  is connected to an RF power source  260  for providing RF power. An impedance matching unit  262  for matching impedance between the RF power source  260  and the substrate support  220 . 
     To performing the texturing process in the RIE apparatus  200 , the p-type substrate  100  is carried into the chamber  210  and is loaded on the substrate support  220 . Here, the substrate  100  may be directly located on the substrate support  220 . To increase the productivity, a tray (not shown) on which a plurality of substrates  100  are disposed may be brought in the chamber  210 , and the process may be performed. At this time, a means for locating the tray (not shown) thereon may be set up in the chamber  210 . 
     Next, vacuum pumping is carried out through the exhaust port  214 , and process pressure is set up. One or more of etching gases, such as Cl 2 , SF 6 , O 2 , etc., are injected to an upper portion of the substrate support  220  by the gas distribution plate  230 . RF power of 13.56 MHz, for example, is applied to the substrate support  220  from the RF power source  260 . 
     When the RF power is applied to the substrate support  220 , RF electric field is induced between the substrate support  220  and the grounded chamber lid  212 . Electrons accelerated by the RF electric field collide with neutral gases, and plasma, which is a mixture of ions, electrons and radicals, is formed. 
     Here, ions is accelerated by the RF electric field and collide with the surface of the substrate  100 . Therefore, the surface of the substrate  100  is textured. In texturing using the RIE apparatus  200 , even though a crystalline silicon substrate has various crystal faces, uniform surface roughness can be obtained on a surface of the crystalline silicon substrate. According, reproducibility of the texturing process is considerably increased. 
     On the other hand, before texturing the substrate  100  in the RIE apparatus  200 , a process of removing surface damages of the substrate  100  may be performed in the same chamber as the RIE apparatus  200 . 
     Referring to  FIG. 7  and  FIG. 10 , at step ST 130 , n-type dopants are diffused in the p-type substrate  10  to form a P-N junction structure after the texturing process. While a thermal diffusion method has been widely used in the related art, an ion doping method using plasma is used in the present invention. 
       FIG. 15  is a view of illustrating a plasma ion doping apparatus according to the present invention. In  FIG. 15 , the plasma ion doping apparatus  300  includes a chamber  310  having a reaction space, a substrate support  320  in the chamber  310 , a gas distribution plate  330  disposed under and spaced apart from a chamber lid  340  for sealing up an upper part of the chamber  310 , and a gas supply line  350  passing through the chamber lid  340  and supplying gases to the gas distribution plate  330 . 
     Beneficially, the substrate support  320  and the gas distribution plate  330  are formed of anodized aluminum. An exhaust port  314  is set up at a lower part of the chamber  310  to exhaust remaining gases and keep vacuum pressure. 
     The chamber lid  340 , which is electrically connected to the gas distribution plate  330 , is grounded. The substrate support  320  is connected to an RF power source  360  for providing RF power. 
     Especially, it is desirable that the substrate support  320  is further connected to a DC power source  370  to increase incident energies of ions generated by the RF power and improve doping efficiency. 
     At this time, a high pass filter (HPF)  362 , beneficially, is disposed between the RF power source  360  and the substrate support  320  to prevent effects on the RF power source  360  by DC power. In addition, a low pass filter (LPF)  372 , desirably, is disposed between the DC power source  370  and the substrate support  320  to prevent effects on the DC power source  370  by the RF power. 
     An impedance matching unit (not shown) for matching impedance between the RF power source  360  and the substrate support  320 . 
     To perform the ion doping process in the plasma ion doping apparatus  300 , the p-type substrate  100  is carried into the chamber  310  and is loaded on the substrate support  320 . Here, the substrate  100  may be directly located on the substrate support  320 . To increase the productivity, a tray (not shown) on which a plurality of substrates  100  are disposed may be brought in the chamber  310 , and the process may be performed. At this time, a means for locating the tray (not shown) thereon may be set up in the chamber  310 . 
     Next, vacuum pumping is carried out through the exhaust port  314 , and process pressure is set up. Gases including phosphorus (P) as an n-type dopant are injected to an upper portion of the substrate support  320  by the gas distribution plate  330 . For example, the gases including P may be phosphorus hydride (PH3). In addition, argon (Ar) gas may be added. Alternatively, if an n-type substrate is used, gases including boron (B) as a p-type dopant may be injected. 
     RF power of 13.56 MHz and DC power, for example, are simultaneously applied to the substrate support  320  from the RF power source  360  and the DC power source  370 . The frequency of the RF power is not limited to the above-mentioned value, and other RF power of commonly used frequencies can be applied. 
     When the RF power is applied to the substrate support  320 , RF electric field is induced between the substrate support  320  and the grounded chamber lid  330 , and plasma is formed. At this time, p+ ions in the plasma are accelerated by the RF electric field and are incident the surface of the substrate  100 . Therefore, ion doping is carried out on the p-type substrate  100 . 
     Here, the DC power applied to the substrate support  320  from the DC power source  370  increases incident energies of ions generated by the RF power and improves doping efficiency. 
     In the plasma ion doping method as mentioned above, since doping density or P-N junction depth can be relatively accurately controlled by adjusting gas flow rates or the RF power, more precise and higher reproducible process can be performed than the thermal diffusion method. 
     Moreover, the plasma ion doping is performed under relatively low temperature, and there exists no PSG or BSG as residual products of the thermal diffusion process. Accordingly, a step of removing the residual products is not required, and the plasma ion doping method is advantageous in productivity. 
     Further, there is no n+ doing layer on side edges of the substrate  100  differently from the thermal diffusion method because ions normally incident with respect to the surface of the substrate  100  are doped. Therefore, an edge isolation process for preventing leakage currents is not necessary, and productivity is increased. 
     In the meantime, the plasma ion doping apparatus  300  of  FIG. 15  has a similar structure to the texturing apparatus  200  of  FIG. 14 . Thus, it is possible that the texturing process and the plasma ion doping process are subsequently performed in the plasma ion doping apparatus of  FIG. 15 . 
     Actually, since RF power of 13.56 MHz is commonly applied to the substrate supports  220  and  320  of the texturing apparatus  200  and the plasma ion doping apparatus  300  in respective processes, the texturing process and the plasma ion doping process can be subsequently performed in the plasma ion doping apparatus of  FIG. 15 . 
     To do this, the DC power source  370  may be off during the texturing process, and the DC power source  370  may be on during the plasma ion doping process. In addition, because gases supplied through the gas supply line  350  are different in respective processes, an additional gas supply line is needed, and enough exhausting time is necessary between the processes to prevent the gases from being mixed. 
     Referring to  FIG. 7  and  FIG. 11 , at step ST 140 , an activation process is performed after ion doping the p-type substrate  100  using plasma according to the above-mentioned method, and the substrate  100  is heated under predetermined temperatures. 
     In the activation process, the doped ions are activated by supplying additional energy to the substrate  100  such that the doped ions are combined with silicon (Si). The doped ions may function as impurities without the activation process. 
     Additionally, there may be an effect of preheating the substrate  100 , which is necessary for depositing an anti-reflection film by a PECVD method later, through the activation process. 
     It is desirable that the activation process is performed in an additional activation chamber, which includes an optical heat means such as a lamp heater or includes a substrate support with a heater such as resistance coil therein. Heating temperatures and time can be changes according to doped materials or degrees of activation. 
     Referring to  FIG. 7  and  FIG. 12 , at step ST 150 , after ion doping of the p-type substrate  100  is performed and the substrate  100  is preheated through the above-mentioned processes, an anti-reflection film  120  is formed on the n+ doping layer  110 . The anti-reflection film  120  may be a silicon nitride (SiNx) layer deposited by a PECVD method. 
     Referring to  FIG. 7  and  FIG. 13 , at step ST 160 , electrodes are formed on front and back surfaces of the substrate  100  using a conductive material, respectively, after forming the anti-reflection film  120  of SiNx. To do this, conductive paste including aluminum (Al) or silver (Ag) is applied on the front and back surfaces of the substrate  100  by a screen printing method such that a predetermined pattern is formed. Then, a process of sintering the substrate  100  is performed in a furnace under high temperatures. 
     The conductive paste is sintered, and a front electrode  18  and a back electrode  16  are formed on the front and back surfaces of the substrate  10 , respectively. 
     For example, when Al paste is applied on the back surface of the p-type substrate  100  and is sintered, Al is diffused into the substrate  100  during the sintering process, and a p+ layer  150  is formed. Therefore, a back surface field is induced at the back surface of the substrate  100 . The back surface field has the same functions as mentioned above. Referring to  FIG. 7 , at step ST 170 , after forming the electrodes, the efficiency of the solar cell is tested and is classified according to results of the test. Next, a solar cell module is fabricated through a module process for connecting a plurality of completed solar cells. 
     In the meantime, to manufacture a crystalline silicon solar cell according to the exemplary embodiment of the present invention, each process apparatus may be set up efficiently considering productivity and footprints. 
     As stated above, it is possible that the texturing process is performed in the plasma ion doping apparatus  300 . However, there is a limitation on combining respective process apparatuses because process conditions of respective processes are different. 
     Accordingly, it is important to design a manufacturing system of a solar cell such that time for transferring the substrate between processes is minimized and the whole footprint is decreased. 
     MODE FOR INVENTION 
       FIG. 16  is a view of illustrating a manufacturing system of a solar cell according to an exemplary embodiment of the present invention. In  FIG. 16 , the manufacturing system of a solar cell includes a transfer chamber  510  for transferring a substrate and further includes a loadlock chamber  520 , a texturing chamber  530 , a plasma ion doping chamber  540 , an activation chamber  550  and an anti-reflection film deposition chamber  560  connected to respective side portions of the transfer chamber  510 . 
     A slot valve is set up between the transfer chamber  510  and each chamber  520 ,  530 ,  540 ,  550  or  560  to selectively open a gateway. 
     In the manufacturing method of a solar cell according to the present invention, the texturing process, the ion doping process and the anti-reflection film depositing process are performed using plasma under predetermined vacuum pressures. 
     Therefore, the texturing chamber  530 , the plasma ion doping chamber  540  and the anti-reflection film deposition chamber  560  are connected to the transfer chamber  510 , which is always under vacuum, and time for transferring a substrate or vacuum pumping is considerably decreased. 
     The activation chamber  550  not only heats the substrate to provide activation energy to ions doped in the plasma ion doping chamber  540  but also preheats the substrate before depositing an anti-reflection film. 
     For consecutive processes, the activation chamber  550 , beneficially, is disposed between the plasma ion doping chamber  540  and the anti-reflection film deposition chamber  560 . 
     The substrate is carried in and/or out through the loadlock chamber  520  from the exterior. Thus, the loadlock chamber  520  is alternately under vacuum and atmosphere condition. 
     A transfer robot  512  is set up in the transfer chamber  510  to transfer the substrate. When the substrate is carried into the loadlock chamber  520  from the exterior, the transfer robot  512  transfers the substrate into the texturing chamber  530  from the loadlock chamber  520 , into the plasma ion doping chamber  540  after the texturing process, into the activation chamber  550  after the plasma ion doping process, into the anti-reflection film deposition chamber  560  after the activation process, and into the loadlock chamber  520  again after depositing the anti-reflection film. 
     The manufacturing system of a solar cell illustrated in  FIG. 16  is an example. Only the loadlock chamber  520 , the texturing chamber  530  and the plasma ion doping chamber  540  are connected to the transfer chamber  510 , and the activation chamber  550  and the anti-reflection film deposition chamber  560  may be omitted. In addition, to increase efficiency of exchanging substrates, more than two loadlock chambers  520  may be set up. Further, in addition to the texturing chamber  530 , the plasma ion doping chamber  540 , the activation chamber  550  and the anti-reflection film deposition chamber  560 , a process chamber of forming a contact hole for an electrode or applying electrode paste may be connected to a side portion of the transfer chamber  510 . 
     Meanwhile, transferring the substrate may be performed by the transfer robot  512  by a piece or by a tray (not shown) carrying a plurality of substrates. When the tray is used, the tray may be transferred into the loadlock chamber, the texturing chamber, the plasma ion doping chamber, the activation chamber and the anti-reflection film deposition chamber in order. 
     The substrate or the tray may be transferred by a transfer robot, which lifts and transfer the substrate or the tray, or may be transferred by an in-line method using a roller or linear motor. In the latter, the means may be also set up in each chamber. 
       FIG. 17  is a view of illustrating a manufacturing system of a solar cell according to another embodiment of the present invention. In the manufacturing system of a solar cell of  FIG. 17 , a substrate or tray is transferred by an in-line method. More particularly, the manufacturing system of a solar cell of  FIG. 17  includes a loading chamber  570  for carrying the substrate or tray into the system from the exterior and an unloading chamber  580  for carrying the substrate or tray out of the system. A texturing chamber  530 , a plasma ion doping chamber  540 , an activation chamber  550  and an anti-reflection film deposition chamber  560  are set up between the loading chamber  570  and the unloading chamber  580  according to a process order. 
     Functions of the chambers are the same as those of  FIG. 16 , and explanation for the functions will be omitted. 
     After a substrate or tray including a plurality of substrates is supplied in the loading chamber  570  from the exterior, the substrate or tray may pass through and be processed in the texturing chamber  530 , the plasma ion doping chamber  540 , the activation chamber  550  and the anti-reflection film deposition chamber  560  in order, and then the substrate or tray may be carried out through the unloading chamber  580 . 
     Here, only the texturing chamber  530  and the plasma ion doping chamber  540  may be set up between the loading chamber  570  and the unloading chamber  580 , and the activation chamber  550  and the anti-reflection film deposition chamber  560  may be separately set up. A transferring means of an in-line method, for example, a roller or a linear motor, is set up in each chamber to transfer the substrate or tray into a neighboring chamber. 
     In addition, a slot valve is set up between adjacent chambers to selectively open a gateway. 
     In the in-line type manufacturing system of a solar cell, the transfer robot, which is expensive, can be omitted, and costs of the system may be decreased. Since the in-line manufacturing system of a solar cell can be set up in a straight space, where a cluster-type system is difficult to be set up, spaces can be effectively used. In the present invention, the solar cell is manufactured by doping n-type dopants into the p-type substrate. Alternatively, the solar cell may be manufactured by doping p-type dopants into an n-type substrate.