WO2010136081A1

WO2010136081A1 - Fiber laser application for edge film removal process in solar cell applications

Info

Publication number: WO2010136081A1
Application number: PCT/EP2009/061017
Authority: WO
Inventors: Andrea Baccini; Marco Galiazzo
Original assignee: Applied Materials, Inc.
Priority date: 2009-05-27
Filing date: 2009-08-26
Publication date: 2010-12-02
Also published as: ITUD20090105A1; TW201101529A

Abstract

The present invention provides a method and apparatus for edge film stack removal process for fabricating photovoltaic devices. In one embodiment, a method for manufacturing solar cell devices on a substrate includes providing a substrate to an edge material removal apparatus, wherein the substrate has a plurality of materials disposed on a back side of the substrate, the plurality of materials including at least a first doped silicon material and a dielectric material, and removing at least one of the layers formed on the periphery region of the substrate by a fiber laser radiation disposed in the apparatus.

Description

"FIBER LASER APPLICATION FOR EDGE FILM REMOVAL PROCESS IN

SOLAR CELL APPLICATIONS"

*****

BACKGROUND Field of the Invention

[0001] The present invention relates to methods and apparatus for an edge film removal by a laser process, more particularly, for an edge film removal by a fiber laser process for fabricating photovoltaic devices. Description of the Background Art [0002] Photovoltaic (PV) devices or solar cells are devices which convert sunlight into direct current (DC) electrical power. PV or solar cells typically have one or more p-i-n junctions. Each junction comprises two different regions within a semiconductor material, where one side is denoted as the p-type region and the other as the n-type region. When the p-i-n junction of the PV cell is exposed to sunlight (consisting of energy from photons), the sunlight is directly converted to electricity through a PV effect. PV solar cells generate a specific amount of electric power and cells are tiled into modules sized to deliver the desired amount of system power. PV modules are created by connecting a number of PV solar cells and are then joined into panels with specific frames and connectors. [0003] Typically, a PV solar cell includes a plurality of conductive and dielectric materials deposited on a substrate to form solar cell devices. A plurality of conductive and dielectric materials may be formed in different deposition equipments, wherein the profile and dimension of each layer formed along the edge of the substrate may be different. Accordingly, different deposition processes used for depositing the film stack on the substrate surface may often result in mismatched film profiles and film thickness at the edge of the substrate. The film stack formed on the periphery of a substrate is typically removed so that the substrate is ready for subsequent packaging or bonding processes that allow the solar cell devices to be supported and framed. The mismatched edge film profile and a thickness of the films formed on the edge of the substrate often make the film removal process difficult and incomplete, thereby resulting in unwanted residual material that may cause subsequent packaging and/or bonding process problems. [0004] Therefore, there is a need for an improved method and apparatus for removing material from the edge of a substrate that is used to form a photovoltaic device.

SUMMARY OF THE INVENTION [0005] The present invention provides a method and apparatus for removing a film along an edge of a substrate. The method is particularly advantageous for fabricating photovoltaic devices. In one embodiment, a method for manufacturing solar cell devices on a substrate includes providing a substrate to an edge material removal apparatus, wherein the substrate has a plurality of materials disposed on a back side of the substrate, the plurality of materials including at least a first doped silicon material and a dielectric material, and removing at least one of the layers formed on the periphery region of the substrate by a fiber laser radiation disposed in the apparatus. [0006] In another embodiment, a edge material removal apparatus includes a stage, a translation mechanism configured to control movement of the stage, and a fiber laser module disposed adjacent to the stage, wherein the fiber laser module further comprises a laser radiation source, and a focusing optical module having an optical fiber disposed therein, wherein the optical fiber is configured to receive laser radiation transmitted from the laser radiation source and then amplify and emit the received laser radiation toward an edge of the stage.

[0007] In yet another embodiment, a method for removing layers on a periphery region of a substrate includes providing a substrate having a film stack disposed on a back side of the substrate into an edge material removal apparatus, wherein the film stack includes at least a patterned film stack having a conductive layer filled in between the patterned film stack, providing a fiber laser radiation toward a periphery region of the substrate, and removing the film stack from the periphery region of the substrate by the fiber laser radiation at a scan rate greater than 1000 millimeters per seconds. BRIEF DESCRIPTION OF THE DRAWINGS [0008] So that the manner in which the above recited features of the present invention are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings. [0009] Figure 1 depicts a diagram of a side view of one embodiment of a fiber laser edge removal apparatus that may be utilized to practice the present invention;

[0010] Figure 2A depicts a cross sectional view of a fiber laser assembly in accordance with one embodiment of the present invention;

[0011] Figure 2B depicts a cross sectional view of a fiber device disposed in the fiber laser apparatus of Figure 2A in accordance with one embodiment of the present invention;

[0012] Figure 3 depicts a process flow chart for removing a portion of the film stack from a periphery region of the substrate in the fiber laser edge removal apparatus of Figure 1;

[0013] Figure 4A depicts a top view of a substrate having solar cell devices formed thereon in accordance with one embodiment of the present invention;

[0014] Figure 4B depicts a cross sectional view of a substrate having solar cell devices formed thereon in accordance with one embodiment of the present invention;

[0015] Figure 5 depicts a cross sectional view of a substrate having solar cell devices formed thereon in accordance with another embodiment of the present invention; [0016] Figure 6 depicts a cross sectional view of a substrate after performing a fiber laser edge removal process in accordance with one embodiment of the present invention;

[0017] Figure 7A is a schematic isometric view of a screen printing system that may be used in conjunction with embodiments of the present invention; [0018] Figure 7B is a schematic top plan view of the system in Figure 7A according to one embodiment of the invention; and

[0019] Figure 7C is an isometric view of a printing nest portion of the screen printing system according to one embodiment of the invention.

[0020] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

[0021] It is to be noted, however, that the appended drawings illustrate only exemplary embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

DETAILED DESCRIPTION [0022] Embodiments of the present invention provide methods and an apparatus for removing a portion of a film stack disposed on a periphery region of a substrate by use of an edge material removal apparatus. The edge material removal apparatus may utilize an electromagnetic energy source that is used to ablate a portion of the film stack from the periphery region of the substrate. In one embodiment, the edge material removal apparatus provides a source beam that has a desired wavelength and an amount of energy to efficiently remove the film stack from the periphery region of the substrate. In one embodiment, the edge material removal apparatus may utilize a fiber laser source to ablate a portion of the film stack from the periphery region of the substrate. In other embodiments, the edge material removal apparatus may utilize other types of focused energy sources, such as an electron beam, ion beam or other similar source to ablate a portion of the film stack from the periphery region of the substrate. [0023] Figure 1 depicts an edge material removal apparatus 100 that may be used to remove one or more of films from the periphery region of a substrate. In one embodiment, the edge material removal apparatus 100 comprises a fiber laser module 106, a stage 103 configured to receive a substrate 102 disposed thereon, and a translation mechanism 116 configured to control the movement of the stage 103. The fiber laser module 106 comprises a laser radiation source 108 and a focusing optical module 126 disposed between the laser radiation source 108 and the stage 103.

[0024] Figure 2A illustrates a configuration of the laser radiation source 108 and a focusing optics module 126 disposed in the fiber laser module 106. The laser radiation source 108 includes a pumped laser source 108A that emits a light beam to an optical fiber 122 disposed in the focusing optical module 126. The optical fiber 122 servers as a gain medium that is configured to receive a pulse of energy delivered from the pumped laser source 108A having a first pulse wavelength and a first pulse energy. When received by the optical fiber 122, the pulse of energy from the pumped laser source 108 A is then amplified and emitted toward a target object, such as an edge of the substrate disposed on a stage 103. Suitable examples for the gain medium may be fiber doped with one or more rare-earth metals (e.g., actinides, lanthanides), such as erbium, neodymium, ytterbium, thulium, praseodymium, holmium, dysprosium, samarium or the like. Light emitting atoms, such as rare earth metals, are doped into a core of the optical fiber 122 that confines the light that the atoms emit. A pair of mirrors 120a, 120b may be disposed on each end of the optical fiber 122 to confine the pumped radiation inside the fiber gain medium and allow the emitted radiation to exit therefrom.

[0025] In one embodiment, the pumped laser source 108A may provide energy at a wavelength between about 900 nm and about 1000 nm, such as about 975 nm. As the energy is delivered through the optical fiber 122, an operating wavelength between about 950 nm and about 1060 nm, such as about 1030 nm, is obtained due to the presence of elements that are doped into the optical fiber 122. In one example, the power delivered by the pumped laser source 108A is in the range of about 10 Watts to about 500 Watts, such as about 100 Watts. The operating frequency of the delivered pulses of energy by the laser radiation source 108 is controlled at between about 20 kHz and between about 100 kHz. [0026] In one embodiment, the optical fiber 122 may include a core 210, an internal cladding 212 and an outer cladding 214, as depicted in the cross- sectional view shown in Figure 2B. The core 210 may be formed from a ceramic material that has the rare earth metals doped therein. Suitable ceramic containing materials may include suitable dielectric materials, such as silica, silicon containing material, silicon carbon, silicon oxide, and the like. In one embodiment, the rare earth metals selected to be doped into the core 210 are erbium or ytterbium. The internal cladding 212 may be made from a material having a first refractive index and the external cladding 214 may be made from a material having a second refractive index different from the first refractive index. It is believed that large refractive index contrast between the internal cladding 212 and the external cladding 214 may enhance light reflection when transmitting through the optical fiber 122, thereby amplifying the laser emitting efficiency. In one embodiment, the internal cladding 212 and the external cladding 214 may have a refractive index difference greater than 0.3 and the internal cladding 212 and the external cladding 214 may be fabricated from suitable ceramic materials, such as silica glass, silicon carbide, or the like.

[0027] Referring back to Figure 1, the focusing optics module 126 may also include one or more collimators to collimate radiation from the pumped laser source 108A into a substantially parallel beam. This collimated radiation beam is then focused by at least one lens 124 into a line of radiation 112 directed at a periphery region 110 of the substrate 102, as depicted in Figure 1. The radiation 112 is controlled to be scanned along the periphery region 110 found at the edge of the substrate 102 to remove a portion of a film stack 150 formed thereon. In one embodiment, the radiation 112 may scan around the edge of the substrate 102 as many times as needed until the film stack 150 has been completely removed. [0028] Lens 124 may be any suitable lens, or series of lenses, capable of focusing radiation into a line or spot. In one embodiment, lens 124 is a cylindrical lens. Alternatively, lens 124 may be one or more concave lenses, convex lenses, plane mirrors, concave mirrors, convex mirrors, refractive lenses, diffractive lenses, Fresnel lenses, gradient index lenses, or the like. [0029] The edge material removal apparatus 100 may include the translation mechanism 116 configured to translate the stage 103 and the line of radiation 112 relative to one another. In one embodiment, the translation mechanism 116 is coupled to the stage 103 so that it is adapted to move the stage 103 relative to the laser radiation source 108 and/or the focusing optics module 126. In another embodiment, the translation mechanism 116 is coupled to the laser radiation source 108 and/or the focusing optics module 126 to move the laser radiation source 108, the focusing optics module 126, and/or an actuated mirror (not shown) to cause the beam of energy to move relative to the substrate 102 that is disposed on the stage 103. In yet another embodiment, the translation mechanism 116 moves both the laser radiation source 108 and/or the focusing optics module 126, and the stage 103. Any suitable translation mechanism may be used, such as a conveyor system, rack and pinion system, or an x/y actuator, a robot, or other suitable mechanical or electro-mechanical mechanism. Alternatively, the stage 103 may be configured to be stationary, while a plurality of galvanometric heads (not shown) may be disposed around the substrate edge to direct radiation from the laser radiation source 108 to the substrate edge as needed.

[0030] The translation mechanism 116 may be coupled to a controller 114 to control the scan speed at which the stage 103 and the line of radiation 112 move relative to one another. In general, the stage 103 and the line of radiation 112 are moved relative to one another so that the delivered energy only translates along the periphery region 110 of the substrate 102 so that other regions of the substrate 102 are not damaged. In one embodiment, the translation mechanism 116 moves at a constant speed. In another embodiment, the translation of the stage 103 and movement of the line of radiation 112 follow different paths that are controlled by the controller 114.

[0031] A camera 152 may be positioned in the edge material removal apparatus 100 to monitor the patterns and/or features formed in the film stack 150 formed on the substrate 102. As each substrate 102 may have different patterned features formed thereon, the camera 152 and controller 114 may be configured to monitor and inspect the layout of patterns and/or features formed on either front side or back side of the substrate 102. The camera 152 and controller 114 can then be used to compare the current image of the substrate 102 with the images saved in the database to determine a proper size of the periphery region 1 10 that needs to be removed from the edge of the substrate 102 in a subsequent step.

[0032] Figure 3 depicts a method 300 for manufacturing solar cell devices on a substrate, such as the substrate 102 depicted in Figure 1. The method starts at step 302 by providing the substrate 102 into an edge material removal apparatus, such as the edge material removal apparatus 100 depicted in Figure 1. The substrate 102 may be a transparent substrate having a plurality of film layers disposed thereon. In one embodiment, the substrate 102 may have a first transparent conductive layer 414, a film stack 416, and a second conductive layer 418 disposed thereon, as depicted in Figure 4B. The first conductive layer 414 may serve as a first electrode disposed on the substrate 102. The second transparent conductive layer 418 may be fabricated from a material similar to the first transparent conductive layer 414, serving as a back electrode disposed on the substrate 102. A plurality of scribing lines 420A, 420B, 420C, or patterns, may be formed on the substrate 402 to form desired features on the substrate 102. In one embodiment, as depicted in Figure 4B, the interconnection lines, such as the scribing lines 420A, 420B, 420C (e.g., isolation grooves), which are generally required to form a high efficiency solar cell device, may be formed in the first conductive layer 414, the film stack 416 and the second conductive layer 418 on the substrate 102 by suitable interconnect formation process. The interconnect formation process is performed on the substrate to electrically isolate various regions of the substrate surface from each other by a laser ablation process, an etching process, or other suitable patterning process. In one embodiment, the first and the second transparent conductive layer 414, 418 are zinc containing material, aluminum containing material, tin containing material, ITO containing material, alloys thereof, and any other suitable conductive materials. [0033] In one embodiment, the film stack 416 includes a film stack typically including a p-type silicon containing layer, a n-type silicon containing layer and an intrinsic type (i-type) silicon containing layer sandwiched between the p-type and n-type silicon containing layers. The silicon layers may be microcrystalline silicon based material, amorphous silicon based materials, or polysilicon based material. It is noted that multiple layers, more than three layers, may be formed in the silicon-containing film stack 416 for different process purposes. For example, multiple silicon based layers may be used in the silicon-containing film stack 416 to provide one or more, e.g., multiple, junctions to improve light conversion efficiency. In one exemplary embodiment, the silicon-containing film stack 416 includes a single solar cell junction having a p-type amorphous silicon layer, an i-type amorphous silicon layer, and a n-type amorphous silicon layer. In yet another exemplary embodiment, the silicon-containing film stack 416 includes a tandem junction having a top cell including a p-type amorphous silicon layer, an i-type amorphous silicon layer, and a n-type microcrystalline silicon layer, and a bottom cell including a p-type microcrystalline silicon layer, an i-type microcrystalline silicon layer and a n-type amorphous silicon layer. One suitable example of the silicon-containing film stack is disclosed in detail by U.S. Application Serial No. 11/624,677, filed January 18, 2007 by Choi et al, titled "Multi-Junctions Solar Cells and Methods and Apparatus for Forming the Same", (Attorney Docket no. APPM/11709), U.S. Application Serial No. 12/208,478, filed September 11, 2008 by Sheng et al, titled "Microcrystalline Silicon Alloys for Thin Film and Wafer Based Solar Applications", (Attorney Docket no. APPM/13551) and are herein incorporated by references.

[0034] Figure 4A illustrates a top view of one embodiment of the substrate 102 that is positioned within the edge material removal apparatus 100. As discussed above, subsequent layers of deposited material at the periphery region 110 of the substrate 102 may have a different film stack thickness than the thickness of the film stack in the active region 412 of the formed solar cell device. In one embodiment, the periphery region 110 has the width 408 between about 10 mm and about 20 mm. In one embodiment, where the substrate is about 2.2 m x 2.6 m in size the periphery region 110 has the width 408 between about 5 mm and about 20 mm.

[0035] The first transparent conductive layer 414, the film stack 416, and the second transparent conductive layer 418 may each be formed by different deposition techniques having different film properties, different film edge exclusions and film thickness may be found in the periphery region 110 of the substrate 102. Accordingly, the substrate 102 is positioned in the edge material removal apparatus 100 to remove a portion of the film stack along the periphery region 110 of the substrate to reduce the likelihood of damage, such as chipping or particle generation, from occurring during the subsequent process steps. Removal of the film stack from periphery region 110 allows the periphery region 110 to be a frame holding area to facilitate the bonding or sealing the substrate 102 to a backside of another substrate to form a complete solar cell module assembly. [0036] At step 304, the substrate 102 is then transferred into the edge material removal apparatus 100, so that an edge removal process can be performed to remove a portion of the film stack from the periphery region 110 of the substrate 102. In one embodiment, the edge material removal apparatus 100 scans the substrate 102 at a rate between about 200 millimeters per seconds (mm/s) and about 1500 millimeters per seconds (mm/s), such as greater than 1000 millimeters per seconds (mm/s). The laser radiation may be in form of a pulse of energy that has a pulse width from a femtosecond (~10^~15 seconds) to about 80 nanoseconds. In one example, the wavelength of the delivered energy is in a range between about 800 nm and about 1500nm. The pulse repetition rate may be controlled about 20 kHz and about 100 kHz. The beam quality factor (M2) may be controlled about 1.6. The energy power per pulse is controlled between about 10 Watts to 500 Watts, such as about 100 Watts. By using the fiber laser radiation source 106, a high energy power per pulse, such as about 100 Watts or greater, may be obtained. Accordingly, a high relative scan speed of the delivered energy along the periphery region 110 may be used, such as greater than 1000 millimeters per seconds (mm/s), thereby improving throughput and manufacturing productivity. [0037] At step 306, after the film stack at the periphery region 110 of the substrate 102 has been removed, the substrate 102 may be unloaded from the edge material removal apparatus 100 to perform the end of the line process(es). The end of the line processes may include final wire attaching, bonding, packaging, and backside substrate bonding process. It is contemplated that other process steps associated with the solar cell device fabrication may also use the edge material removal apparatus 100 described in the present invention.

[0038] Referring first to Figure 6, Figure 6 depicts a cross sectional view of the substrate 102 after the edge removal process is performed. After performing the laser edge removal process, the films previously located at the periphery region 110 of the substrate 102 have been completely removed. Optionally, a portion of the substrate 102 may also be removed to assure the complete removal of the material that was positioned within the periphery region 110. In one embodiment, a portion of the substrate 102 having a depth 502 between about 10 μm and about 75 μm from the substrate surface is also removed. [0039] Figure 5 illustrates a cross sectional view of a crystalline silicon type solar cell substrate, or substrate 510, that may be positioned within the edge material removal apparatus 100 to perform the material removal process. Figure 5 schematically depicts one embodiment of a silicon solar cell 500 fabricated on a solar cell substrate 510 having a textured surface 512. The substrate 510 includes a p-type base region 521, an n-type emitter region 522, and a p-n junction region 523 disposed therebetween. An n-type region, or n-type semiconductor, is formed by doping the deposited semiconductor layer with certain types of elements (e.g., phosphorus (P), arsenic (As), or antimony (Sb)) in order to increase the number of negative charge carriers, i.e., electrons. In one configuration, the n-type emitter region 522 is formed by use of an amorphous, microcrystalline, nanocrystalline or polycrystalline silicon CVD deposition process that contains a dopant containing gas. In one embodiment, a thin intrinsic type layer may be formed between the p-type base region 521 and the n- type emitter region 522, to form a heterojunction type solar cell. In a formed solar cell 500, the electrical current generated when light strikes the front surface 520 flows through metal front contacts 508 and the metal backside contact 525 of the solar cell 500. The front contacts 508 are generally configured as widely- spaced thin metal lines, or fingers, that supply current to larger bus bars transversely oriented to the fingers. The back contact 506 is generally not constrained to be formed in multiple thin metal lines, since it does not prevent incident light from striking the solar cell 500. In one embodiment, the front contacts 508 and/or back contact 506 is a metal selected from a group consisting of aluminum (Al), silver (Ag), tin (Sn), cobalt (Co), nickel (Ni), zinc (Zn), lead (Pb), tungsten (W), titanium (Ti) and/or tantalum (Ta) or other similar materials. In one embodiment, the back contact 506 comprises an aluminum (Al) material and a nickel vanadium (NiV) material. In one embodiment, portions of the front contacts 508 and back contact 506 are disposed on the surfaces of the substrate 510 using a screen printing process performed in a screen printing tool, which is available from Baccini S.p.A, which is a subsidiary of Applied Materials, Inc. In one embodiment, the front contacts 508 and back contact 506 are heated in an oven to cause the deposited material to densify and form a desirable electrical contact with the substrate surface. The solar cell 500 may be covered with a thin layer of dielectric material, such as silicon nitride (Si₃N₄) or silicon nitride hydride (SixNy:H), to act as an anti-reflection coating layer 51 1, or ARC layer 51 1, that minimizes light reflection from the top surface of the solar cell 500. The solar cell device configurations illustrated in Figure 5A are not intended to be limiting as to the scope of the invention since other substrate and solar device region configurations can be metallized using the methods and apparatuses described herein without deviating from the basic scope of the invention. It is contemplated that the processes performed during the method 300 may be used to facilitate the formation of many different types of solar cell devices, such as heterojunction type cells, point contact type cells, tunnel junction solar cells, or other similar devices. An example of formed solar cell devices that can benefit from the processes described herein are further described in the commonly assigned United States Provisional Patent Application Serial Number 61/048,001 [Atty. Dkt No. 13438L], filed 7/16/08, United States Provisional Patent Application Serial Number 61/139,423 [Atty. Dkt No. 13437L03], filed 12/19/08, and United States Provisional Patent Application Serial Number 61/043,664 [Atty. Dkt No. 13306L], filed 4/9/08, which are all incorporated by reference in their entirety. [0040] As discussed above, after different film stacks and processes are performed on the substrate 510, the substrate 510 may be transferred into the edge material removal apparatus 100 to perform the edge film removal process, such as the process 300 depicted in Figure 3, prior to the end of the line processes, such as wire attaching, bonding, and packaging processes. [0041] In one embodiment, the periphery region 550 of the substrate 510 has the first width 518 between about 50 μm and about 60 μm on the front side of the substrate 510 and a second width 520 between about 50 μm and about 60 μm on the backside of the substrate 510. The distance from the substrate edge to the first metal front contact 508 formed on the substrate is between about 150 μm and about 200 μm. [0042] Figure 7A is a schematic isometric view and Figure 7B is a schematic top plan view illustrating one embodiment of a screen printing system, or system 700, that may be used in conjunction with embodiments of the present invention to remove material from a surface of a solar cell substrate 750 using the edge material removal apparatus 100. In one embodiment, the system 700 comprises an incoming conveyor 711, a rotary actuator assembly 730, a screen print chamber 702, an outgoing conveyor 712 and an edge material removal apparatus 100 coupled to the outgoing conveyor 712. The incoming conveyor 711 may be configured to receive a substrate 750 from an input device, such as an input conveyor 713 (i.e., path "A" in Figure 7B), and transfer the substrate 750 to a printing nest 731 coupled to the rotary actuator assembly 730. The outgoing conveyor 712 may be configured to receive a processed substrate 750 from a printing nest 731 coupled to the rotary actuator assembly 730 and transfer the substrate 750 to the edge material removal apparatus 100 where the method 300 can be performed. From the edge material removal apparatus 100 the substrate 750 can be transferred to a substrate removal device, such as an exit conveyor 714 (i.e., path "E" in Figure 7B). The input conveyor 713 and the exit conveyor 714 may be automated substrate handling devices that are part of a larger production line. For example, the input conveyor 713 and the exit conveyor 714 may be part of the Softline™ tool, of which the system 700 may be a module. [0043] The rotary actuator assembly 730 may be rotated and angularly positioned about the "F" axis by a rotary actuator (not shown) and a system controller 701, such that the printing nests 731 may be selectively angularly positioned within the system 700 (e.g., paths "Dl" and "D2" in Figure 7B). The rotary actuator assembly 730 may also have one or more supporting components to facilitate the control of the print nests 731 or other automated devices used to perform a substrate processing sequence in the system 700. [0044] In one embodiment, the rotary actuator assembly 730 includes four printing nests 731, or substrate supports, that are each adapted to support a substrate 750 during the screen printing process performed within the screen print chamber 702. Figure 7B schematically illustrates the position of the rotary actuator assembly 730 in which one printing nest 731 is in position "1" to receive a substrate 750 from the incoming conveyor 711, another printing nest 731 is in position "2" within the screen print chamber 702 so that another substrate 750 can receive a screen printed pattern on a surface thereof, another printing nest 731 is in position "3" for transferring a processed substrate 750 to the outgoing conveyor 712, and another printing nest 731 is in position "4", which is an intermediate stage between position "1" and position "3". [0045] As illustrated in Figure 7C, a printing nest 731 generally consists of a conveyor assembly 739 that has a feed spool 735, a take-up spool 736, rollers 740 and one or more actuators 748, which are coupled to the feed spool 735 and/or take-up spool 736, that are adapted to feed and retain a supporting material 737 positioned across a platen 738. The platen 738 generally has a substrate supporting surface on which the substrate 750 and supporting material 737 are positioned during the screen printing process performed in the screen print chamber 702. In one embodiment, the supporting material 737 is a porous material that allows a substrate 750, which is disposed on one side of the supporting material 737, to be retained on the platen 738 by a vacuum applied to the opposing side of the supporting material 737 by a conventional vacuum generating device (e.g., vacuum pump, vacuum ejector). In one embodiment, a vacuum is applied to vacuum ports (not shown) formed in the substrate supporting surface 738A of the platen 738 so that the substrate can be "chucked" to the substrate supporting surface 738A of the platen. In one embodiment, the supporting material 737 is a transpirable material that consists, for instance, of a transpirable paper of the type used for cigarettes or another analogous material, such as a plastic or textile material that performs the same function. In one example, the supporting material 737 is a cigarette paper that does not contain benzene lines.

[0046] In one configuration, the actuators 748 are coupled to, or are adapted to engage with, the feed spool 735 and a take-up spool 736 so that the movement of the substrate 750 positioned on the supporting material 737 can be accurately controlled within the printing nest 731. In one embodiment, the feed spool 735 and the take-up spool 736 are each adapted to receive opposing ends of a length of the supporting material 737. The actuators 748 may each contain one or more drive wheels 747 that are coupled to, or in contact with, the surface of the supporting material 737 positioned on the feed spool 735 and/or the take-up spool 736 to control the motion and position of the supporting material 737 across the platen 738.

[0047] Referring back to Figure 7A, the system 700 includes an inspection assembly 720 adapted to inspect a substrate 750 located on the printing nest 731 in position "1". The inspection assembly 720 may include one or more cameras 721 positioned to inspect an incoming, or processed substrate 750, located on the printing nest 731 in position "1", as shown in Figure 7B. In this configuration, the inspection assembly 720 includes at least one camera 121 (e.g., CCD camera) and other electronic components capable of inspecting and communicating the inspection results to the system controller 701 used to analyze the orientation and position of the substrate 750 on the printing nest 731.

[0048] The screen print chamber 702 is adapted to deposit material in a desired pattern on the surface of the substrate 750 positioned on the printing nest 731 in position "2" during the screen printing process. In one embodiment, the screen print chamber 702 includes a plurality of actuators, for example, actuators 702A (e.g., stepper motors or servomotors) that are in communication with the system controller 701 and are used to adjust the position and/or angular orientation of a screen printing mask 702B (Figure 7B) disposed within the screen print chamber 702 with respect to the substrate 750 being printed. In one embodiment, the screen printing mask 702B is a metal sheet or plate with a plurality of features 702C (Figure 7B), such as holes, slots, or other apertures formed therethrough to define a pattern and placement of screen printed material (i.e., ink or paste) on a surface of a substrate 750. In general, the screen printed pattern that is to be deposited on the surface of a substrate 750 is aligned to the substrate 750 in an automated fashion by orienting the screen printing mask 702B in a desired position over the substrate surface using the actuators 702A and information received by the system controller 701 from the inspection assembly 720. The screen print chamber 702 is adapted to deposit a metal containing or dielectric containing material on the substrate 750 having a width between about 125 mm and 156 mm and a length between about 70 mm and 156 mm. In one embodiment, the screen print chamber 702 is adapted to deposit a metal containing paste on the surface of the substrate 750 to form the metal contact structure on a surface of a substrate. The edge material removal apparatus 100 is thus positioned downstream of the screen print chamber 702 to remove the screen printed material disposed on the edges of the substrate 750. In one embodiment, an oven (not shown) is positioned between the screen print chamber 702 and the edge material removal apparatus 100 to density and anneal the metal containing or dielectric containing material disposed on the surface of the substrate 750 during the screen printing process.

[0049] The system controller 701 facilitates the control and automation of the overall system 700 and may include a central processing unit (CPU) (not shown), memory (not shown), and support circuits (or I/O) (not shown). The CPU may be one of any form of computer processors that are used in industrial settings for controlling various chamber processes and hardware (e.g., conveyors, optical inspection assemblies, motors, fluid delivery hardware, etc.) and monitor the system and chamber processes (e.g., substrate position, process time, detector signal, etc.). The memory is connected to the CPU, and may be one or more of a readily available memory, such as random access memory (RAM), read only memory (ROM), floppy disk, hard disk, or any other form of digital storage, local or remote. Software instructions and data can be coded and stored within the memory for instructing the CPU. The support circuits are also connected to the CPU for supporting the processor in a conventional manner. The support circuits may include cache, power supplies, clock circuits, input/output circuitry, subsystems, and the like. A program (or computer instructions) readable by the system controller 701 determines which tasks are performable on a substrate. Preferably, the program is software readable by the system controller 701, which includes a code to generate and store at least substrate positional information, the sequence of movement of the various controlled components, substrate optical inspection system information, and any combination thereof. In one embodiment of the present invention, the system controller 701 includes software to monitor and control the hardware and processes performed in the edge material removal apparatus 100 and screen print chamber 702.

[0050] Thus, improved methods and apparatus for removing a portion of a film stack disposed at a substrate edge are provided. The method and apparatus advantageously increase accuracy, throughput, and scan speed for removing film stack at a periphery region of the substrate, thereby providing a good seal surface for the substrate to facilitating bonding and packaging processes.

[0051] While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

CLAIMS 1. A method for manufacturing solar cell devices on a substrate, comprising: providing a substrate to an edge material removal apparatus, wherein the substrate has a plurality of materials disposed on a back side of the substrate, the plurality of materials including at least a first doped silicon material and a dielectric material; and removing at least one of the layers formed on the periphery region of the substrate by a fiber laser radiation disposed in the apparatus.

2. The method of claim 1, wherein a front side of the substrate includes a plurality of second dopant materials formed therein.

3. The method of claim 2, wherein the second dopant material is an n-type or p- type material in a gel or paste.

4. The method of claim 1, wherein the fiber laser radiation emits a wavelength between about 800 nm and about 1500nm.

5. The method of claim 1, wherein the fiber laser radiation is generated from a rare earth ion doped pulsed power.

6. The method of claim 5, wherein the rare earth ion is selected from a group of elements consisting of erbium, neodymium, ytterbium, thulium, praseodymium or the like.

7. The method of claim 1, wherein the fiber laser radiation provides a scan rate between about 200 millimeters per seconds (mm/s) and about 1500 millimeters per seconds (mm/s).

8. The method of clam 1, wherein the fiber laser radiation has an energy power between about 10 Watts and 500 Watts per pulse.

9. The method of claim 1, wherein the first doped silicon material is a p-type doped amoφhous silicon hydride (a-Si:H) layer.

10. The method of claim 1, wherein the periphery region of the substrate has a width between about 50 μm and about 60 μm.

11. The method of claim 1 , wherein removing at least one of the layers further comprises: continuously laser scanning the periphery region of the substrate along each side of the substrate.

12. A edge material removal apparatus, comprising: a stage; a translation mechanism configured to control movement of the stage; and a fiber laser module disposed adjacent to the stage, wherein the fiber laser module further comprises: a laser radiation source; and a focusing optical module having an optical fiber disposed therein, wherein the optical fiber is configured to receive laser radiation transmitted from the laser radiation source and then amplify and emit the received laser radiation toward an edge of the stage.

13. The apparatus of claim 12, wherein the optical fiber further comprises: a core; an internal cladding coated on the core; and an external cladding coated on the internal cladding.

14. The apparatus of claim 13, wherein the core is doped with rare earth metals selected from a group of element consisting of erbium, neodymium, ytterbium, thulium, praseodymium or the like.

15. The apparatus of claim 13, wherein the internal cladding and the external cladding have a refractive index contrast greater than 0.3.

16. The apparatus of claim 12, wherein the laser radiation source is a pump laser source having a light wavelength between about 800 nm and about 1500 nm.

17. The apparatus of claim 12, wherein the laser radiation source has a power ranging from between about 10 Watts and about 500 Watts.

18. The apparatus of claim 12, wherein the laser radiation is configured to remove at least one of the layers formed on a periphery region of a substrate disposed on the stage.

19. The apparatus of claim 18, wherein the at least one of the layers disposed on the substrate includes at least one of a conductive layer or a silicon containing layer configured to form solar cell devices.

20. The apparatus of claim 18, wherein the periphery region of the substrate has a width between about between about 50 μm and about 60 μm.

21. The apparatus of claim 12, wherein the fiber laser module gas a scan rate between about 200 millimeters per seconds (mm/s) and about 1500 millimeters per seconds (mm/s).

22. A method for removing layers on a periphery region of a substrate, comprising: providing a substrate having a film stack disposed a back side of the substrate into a edge material removal apparatus, wherein the film stack includes at least a patterned film stack having a conductive layer filled in between the patterned film stack; providing a fiber laser radiation toward a periphery region of the substrate; and removing the film stack from the periphery region of the substrate by the fiber laser radiation at a scan rate greater than 1000 millimeters per seconds.

23. The method of claim 22, wherein the film stack includes at least a doped silicon layer and a dielectric layer.

24. The method of claim 23, wherein the conductive layer is one selected from a group consisting of aluminum (Al), silver (Ag), tin (Sn), cobalt (Co), nickel (Ni), zine (Zn), lead (Pb), tungsten (W), titanium (Ti) or tantalum (Ta).

25. The method of claim 23, wherein a front side of the substrate has a plurality of conductive layer formed thereon, wherein the patterned conductive layer is a TCO layer.