Various embodiments described herein relate generally to systems for scribing or patterning a workpiece, and more particularly to systems for laser scribing a workpiece with a selectable size for a laser beam incident on the workpiece. Such systems can be particularly effective for laser-scribing glass substrates having at least one layer used to form thin-film solar cells.
Current methods for forming thin-film solar cells involve depositing or otherwise forming a plurality of layers on a substrate, such as a glass, metal or polymer substrate suitable to form one or more p-n junctions. An example thin-film solar cell includes a glass substrate having a transparent-conductive-oxide (TCO) layer, a plurality of doped and undoped silicon layers, and a metal back layer. Examples of materials that can be used to form solar cells, along with methods and apparatus for forming the cells, are described, for example, in U.S. Pat. No. 7,582,515, entitled “MULTI-JUNCTION SOLAR CELLS AND METHODS AND APPARATUSES FOR FORMING THE SAME,” the entire disclosure of which is hereby incorporated herein by reference.
When a panel is formed from a large substrate, a series of laser-scribed lines can be used within each layer to delineate individual cells.
The optimal beam size incident on the workpiece depends on the use of the resulting thin-film solar cell. For example, a small spot size can be used for interconnect line scribing in order to produce a high-efficiency solar panel by reducing the amount of inactive panel area. A relatively larger beam size (e.g., 1 mm wide) can be used for scribing wider P3 interconnect lines to fabricate semi-transparent modules for use in building integrated photovoltaics (BIPV) applications.
BIPV applications, however, may not yet have a sufficient level of market demand to justify separate dedicated laser-scribing systems. Accordingly, it is desirable to develop laser-scribing systems with a selectable size for a laser beam incident on the workpiece.
The following presents a simplified summary of some embodiments of the invention in order to provide a basic understanding of the invention. This summary is not an extensive overview of the invention. It is not intended to identify key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some aspects and embodiments in a simplified form as a prelude to the more detailed description that is presented later.
Systems in accordance with various aspects and embodiments are disclosed for laser-scribing a workpiece. The disclosed systems are operable to remove material from a workpiece with a selectable size of laser beam incident on a workpiece. The capability to change the beam spot size enables the production of different solar-cell assemblies (e.g., for different applications) on the same equipment. Such a capability may serve to reduce fabrication costs by decreasing associated capital costs and/or by increasing system utilization rates.
Thus, in a first aspect, a system is provided for scribing a workpiece. The system includes a frame, a laser coupled with the frame and operable to generate an output to remove material from at least a portion of the workpiece, a beam expander positioned along a path of the laser output and having a motorized mechanism operable to vary a beam expansion ratio applied to the laser output, and at least one scanning device coupled with the frame and operable to control a position of the laser output, after expansion, on the workpiece. In many embodiments, varying the beam expansion ratio varies a beam size incident on the workpiece. In many embodiments, the incident beam size is variable from approximately 20 um to about 1000 um, and in particular from about 50 um to 200 um in certain embodiments. In many embodiments, the motorized beam expander is disposed along an optical path for the laser output between the laser and the scanning device.
In many embodiments, the system for scribing the workpiece can include one or more additional components. For example, the scribing system can include a translation stage coupled with the frame to support the workpiece and translate the supported workpiece relative to the frame in a longitudinal direction. The at least one scanning device can include a plurality of scanning devices optically coupled with the laser and receiving the laser output via the beam expander. The system can include a lateral translation mechanism operable to translate the at least one scanning device traverse to the longitudinal direction. The system can include an exhaust mechanism operable to collect material removed from the workpiece via the laser output.
In another aspect, a method of scribing a workpiece is provided. The method includes generating a laser output to remove material from at least a portion of the workpiece, varying a beam expansion ratio applied to the laser output, and controlling a position of the laser output, after expansion, on the workpiece.
In another aspect, a system for scribing a workpiece is provided. The system includes a frame, a laser coupled with the frame and operable to generate an output to remove material from at least a portion of the workpiece, at least one scanning device coupled with the frame and operable to control a position of the laser output on the workpiece, and a variable aperture positioned along a path of the laser output between the laser and the scanning device and having a motorized mechanism operable to vary a diameter of the laser output entering the scanning device. The variable-aperture system can be configured and/or have the same functionality as the above-described motorized-aperture system.
For a fuller understanding of the nature and advantages of the present invention, reference should be made to the ensuing detailed description and the accompanying drawings. Other aspects, objects and advantages of the invention will be apparent from the drawings and the detailed description that follows.
In accordance with various aspects and embodiments of the present disclosure, systems are provided for scribing or otherwise patterning a workpiece with a selectable size of laser output incident on the workpiece. Such scribing systems can be used to scribe multiple line types into the workpiece (e.g., P1 interconnect lines, P1 isolation lines, P2 interconnect lines, P3 interconnect lines, P3 isolation lines). The ability to select the size of laser output incident on the workpiece enables the scribing of solar panel assemblies for different applications, for example, efficiency optimized thin-film solar assemblies and building integrated photovoltaic (BIPV) solar assemblies.
This movement is also illustrated in the side view 200 of
In this example, each laser device actually produces two effective beams 304 useful for scribing the workpiece. As can be seen, each portion of the exhaust 108 covers a scan field, or an active area, of the pair of beams in this example, although the exhaust could be further broken down to have a separate portion for the scan field of each individual beam. The figure also shows substrate thickness sensors 306 useful in adjusting heights in the system to maintain proper separation from the substrate due to variations between substrates and/or in a single substrate. Each laser can be adjustable in height (e.g., along the z-axis) using a z-stage, motor, and controller, for example. In many embodiments, the system is able to handle 3-5 mm differences in substrate thickness, although many other such adjustments are possible. The z-motors also can be used to adjust the focus of each laser on the substrate by adjusting the vertical position of the laser itself.
In order to provide the pair of beams, each laser assembly includes at least one beam splitting device.
In many embodiments, each scan head 414 includes a pair of rotatable mirrors 416, or at least one element capable of adjusting a position of the laser beam in two dimensions (2D). Each scan head includes at least one drive element 418 operable to receive a control signal to adjust a position of the “spot” of the beam within the scan field and relative to the workpiece. In one example, a spot size on the workpiece is on the order of tens of microns within a scan field of approximately 60 mm×60 mm, although various other dimensions are possible. While such an approach allows for improved correction of beam position on the workpiece, it can also allow for the creation of patterns or other non-linear scribe features on the workpiece. Further, the ability to scan the beam in two dimensions means that any pattern can be formed on the workpiece via scribing without having to rotate the workpiece.
The relationship between diameter of the beam (D) going into the scanner/telecentric lens (having focal length f) and the focused spot diameter(s) is given by the theoretical relationship: s=kλfM2/D; where k is a constant for the scanner, λ is the wavelength of the beam and M2 characterizes the Gaussian beam. Therefore, the focused spot size is inversely proportional to the incoming beam diameter (D). As such, to get a larger spot size, a smaller incoming beam is required. Thus, when the tool is needed for processing interconnect lines, a larger beam expanding ratio is used to reduce the spot size at the focus point. For example, with a scanner/telecentric lens having a focal length of 100 mm, a 2× beam expander can output a 2 mm collimated beam to produce a 50 um focused spot. When the tool is needed to process BIPV, a smaller beam expanding ratio is used to enlarge the spot size at the focus point. For example, a 0.5× beam expander can output a 0.5 mm collimated beam to produce a 200 um focused spot using the same scanner/telecentric lens (f=100 mm).
Existing motorized beam expanders can be used. For example, a Special Optics (A Navitar Company, 315 Richard Mine Road, Wharton, N.J. 07885) motorized beam expander (e.g., model 56C-30-2-8X @λ) can be used.
Alternatively, a variable aperture can be used to control the size of the beam going into the lens.
The optimal beam size incident on the workpiece can depend upon factors such as the intended use of the resulting thin-film solar cell. For example, a high precision and small spot size can be used for interconnect line scribing in order to produce a high-efficiency solar panel by reducing the amount of inactive panel area. In building integrated photovoltaic (BIPV) applications, a relatively larger beam size (e.g., 1 mm wide) can be used for scribing wider P3 interconnect lines to fabricate semi-transparent modules that can be used to replace a number of architectural elements commonly made with glass or similar materials, such as windows and skylights.
A laser-scribing system with the capability to change the beam spot size enables the production of different solar-cell assemblies (e.g., for different applications) on the same equipment. Such a capability may serve to reduce fabrication costs by decreasing associated capital costs and/or increasing system utilization rates.
It is understood that the examples and embodiments described herein are for illustrative purposes and that various modifications or changes in light thereof will be suggested to a person skilled in the art and are to be included within the spirit and purview of this application and the scope of the appended claims. Numerous different combinations are possible, and such combinations are considered to be part of the present invention.
This application claims the benefit of U.S. Prov. Patent Application No. 61/319,186 filed Mar. 30, 2010, and titled “LASER PROCESSING SYSTEM WITH VARIABLE BEAM SPOT SIZE,” which is incorporated in its entirety by reference for all purposes. The present application is related to U.S. patent application Ser. No. 12/939,137, entitled “MULTI-WAVELENGTH LASER-SCRIBING TOOL,” filed on Nov. 3, 2001, the full disclosure of which is incorporated herein by reference.
Number | Date | Country | |
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61319186 | Mar 2010 | US |