Patent Application
20120136470
The present invention relates to the field of Photovoltaic (“PV”) products and their manufacture and, in particular, to means of increasing efficiencies in such manufacture.
Photovoltaic (“PV”) products and devices directly convert absorbed illumination to electrical energy with the advantage of being non-polluting and silent in operation. They are readily adapted to either a centralized or distributed power generating system and as such, are an attractive alternative to fossil fuels and nuclear power sources. The relatively high cost of PV power has been a historical limitation upon its use; however, high volume processes for the preparation of crystalline silicon (c-Si) and thin film PV devices have now decreased the cost of PV materials. In spite of this, cost of manufacture remains an on-going concern.
The most imperative overall need in the PV industry is to reduce the cost of manufactured PV products sufficiently to achieve grid parity. For wafer, cell and module manufacturers, this drive for cost reduction has three aspects: improved product technology, providing higher power output for a given market price; reduced per-unit cost of materials and capital equipment through economies of scale; and improved manufacturing efficiency and yield. The present invention relates to improving efficiency and yield in the manufacture of PV products. To date, these have not been adequately addressed.
PV wafers, cells and modules are generally inspected manually or by single-point devices at varying intervals in the production process—mostly at the end of the production line. This means that while defects may be caught, accept/reject decisions can only be made on the limited data available at the point of inspection. Additionally, prior to the present inventions and except for the raw material acceptance stage (at the beginning of the line) and the final inspection and grading (at the end of the line), in-line unit-by-unit inspection of products during production is generally rudimentary or non-existent.
Further, wafer, cell and module production facilities frequently operate on a FIFO (First In, First Out) basis only. This means that the products are graded and sorted only at the end of the production line, with varying degrees of inspection at other points in production.
Additionally, most facilities currently monitor their production by measuring the operating parameters of each tool (such as gas flow, power consumption, temperature), not the actual production results by directly inspecting the products themselves at each stage of the process (except for occasional off-line sampling). See for example the disclosure in Patent Cooperation Treaty application published under number WO2009/026661. This produces several deficiencies. First, it gives the facility operator only one option if a process tool begins to operate outside of acceptable parameters (“operational drift”), or generates an error—adjust or fix the tool, which may involve a shutdown. Manual adjustments or outright shutdowns are costly, and it may be that an isolated operational drift can be tolerated, if inspection of the products themselves demonstrates that enough products are remaining in acceptable grades. Or if appropriate downstream adjustments may be made to resolve or mitigate identified potential problems with the products so that sufficient final products are of an acceptable grade or grades.
Conversely, a series of shifts in operating parameters that fall below unacceptable thresholds, but occur over a number of tools, can lead to a quality problem that is unobserved until final inspection and grading—and therefore very hard to isolate since no single tool is at fault. Also, defects may be introduced that have nothing to do with the operating parameters of the tools (such as handling-induced marking or airborne contamination at tool ingress or egress).
Monitoring of tool parameters alone will not find the source of these problems and consequently cannot lead to a resolution of the problems.
As the industry grows, solutions to the above needs, and as provided within the scope of this invention, can have significant financial impact. For example, if a 50 MW cell production line generates approximately $100M to $125M of finished goods value per annum, a yield improvement of only 2 percent would provide an additional $2M to $3.5M of margin per year.
Accordingly there is an unmet need for a method and system to more efficiently control the throughput of photovoltaic cells in a cell manufacturing production line.
Unless the context indicates otherwise the term “production step or steps” means a particular step or steps of the manufacture of PV products which produce measurable differences in the product. And an “intermediate production step or steps” means a production step or steps after the first production step in the production line and before the final step in the production line.
The present invention provides a production line method and system for PV device fabrication which is highly efficient, both in terms of required labour, time and the economical use of PV raw material and production material at each stage of the production process. These and other advantages of the present invention will be readily apparent from the drawings, discussion and description which follow.
The process of the present invention improves PV manufacturing efficiencies in the following ways:
One mode of achieving this within the scope of the invention: Provide for grading, separation or rejection, and (optionally) substitution of individual wafers, cells or modules much earlier in the process in an efficient manner so as not to unduly disrupt the production line. This can be achieved through a combination of end-to-end WIP unit tracking, coordinated in-line inspection, predictive WIP unit grading, distributed WIP unit buffering and closed-loop facility-wide inter-tool material handling. The predictive WIP unit grading and closed loop handling also allows the manufacturer to dynamically adjust grading and rejection thresholds based on end-to-end cost optimization calculated in real time.
One mode of achieving this within the scope of the invention: Through the use of the same technologies as above, plus WIP unit re-sequencing, WIP units that have flaws that are amenable to improvement via particular changes to equipment operational parameters in downstream process tools, are grouped together. The invention provides real-time feed-forward information to the process tools in question that specifies the operational changes to the tools in order to implement downstream solutions to bring the defective group to a acceptable grade by the time the processing of the WIP unit group is completed in the production line. The result is mitigation of the flaws by compensating physical, chemical or electrical characteristics in order to resolve or mitigate in the finished products, problems detected earlier in the manufacturing process. In addition the invention provides real-time feedback for “run-to-run” adaptation in process tool operating parameters to reduce re-occurrence of flaws as much as is possible.
One mode of achieving this within the scope of the invention: Through the use of the same technologies as above, the inventions solve part (a) of this need by providing for prioritization of individual WIP units, based on their (predicted) grade as they move through the production process. This will give the manufacturer a faster or more predictable unit-per-hour production rate for a desired grade of WIP units (order-based production), resulting in higher profitability from the production line investment. Part (b) is solved by providing the means to monitor and assess production results directly on the WIP units—both end-to-end and tool-by-tool—in real time, and to centrally consolidate these measurements to pinpoint issues among and between individual tools. This is accomplished using one or more of: (i) coordinated in-line inspection, (ii) end-to-end WIP unit tracking and (iii) a production performance database built and maintained by the system that can be used to monitor, analyze and report on performance (sometimes referred to herein as “True Production Measurement”).
In an embodiment of the invention a method of manufacturing photovoltaic products in a manufacturing production line of a series of production steps is provided where the following steps are undertaken at each of a plurality of intermediate production steps of the production line:
Alternatively the method can include associating all of the products in the production line at a particular step, having the same stored grade, together in a group for further processing as a group.
As another alternative, the method can include: for groups having grades indicative of products outside of the predetermined tolerances, adjusting the downstream production equipment of the production line to process each such group of products with the same grade so as to bring the group within the predetermined tolerances; and then processing the group together using the downstream production equipment as so adjusted, to bring the products of the group within the predetermined tolerances.
As another alternative, the method can include steps (a) to (d) above performed at every intermediate production step of the production line to obtain a grade for each product at every production step of the production line and associating all of the products in the production line at a particular step, having the same stored grade, together in a group for further processing as a group, at each one of those steps.
In a further alternative the grade assignable to a product at a production step is associated with information for adjusting the downstream production equipment so as to bring the group associated with the grade within the predetermined tolerances and wherein the downstream production equipment is adjusted accordingly for processing of that group.
In a further alternative, if groups at a step are identified as outside of the predetermined tolerances, process changes are made upstream of the step to production equipment to bring future products produced within the predetermined tolerances.
In a further alternative groups identified as outside of the predetermined tolerances at a step are prioritised for further processing after groups at that step which are within the predetermined tolerances.
In a further alternative groups at a step are prioritised for further processing based on the grade of the group, with groups of grades having more significant deviations from the predetermined tolerances positioned for processing behind groups with grades representing lesser deviations from the predetermined tolerances.
In a further alternative a method of controlling a series of production steps in a manufacturing production line for the manufacture of photovoltaic products, includes the steps of:
In a further alternative, at step (e) above:
In a further alternative, the grading information is based on either:
In a further alternative a method of controlling a series of production steps in a manufacturing production line for the manufacture of photovoltaic products, includes the steps of:
In a further alternative, at the comparison step, the real-time assessment is compared to the past assessments at that step. In another alternative, at the comparison step, the real-time assessment is associated with past assessments of the product at the production step and a predetermined number of past production steps compared to said past assessments at that step and the predetermined number of past production steps. In a further alternative:
In a further alternative:
In a further alternative together with said removal instructions, providing instructions to replace the product to be removed with instructions to replace the product with another product at that production step determined by its damage severity threshold to not be at risk of impairing the manufacturing production line at that production step.
In a further alternative an apparatus comprising a processing device is provided with a computer readable medium tangibly embodying a computer program product for manufacturing photovoltaic products, the computer program product comprises instructions for causing a processor to:
In a further alternative an apparatus for manufacturing photovoltaic products includes:
In another embodiment the apparatus includes:
In a further alternative a computer system includes a memory having stored therein a photovoltaic products manufacturing control application for a manufacturing production line of a series of production steps; and a processor coupled to the memory, with the execution of the manufacturing control application generating a method including:
In a further alternative the execution of the application further generates a method including:
In a preferred embodiment the present invention provides a Production Enhancing System (“PES System”) that optimizes the output of a PV factory by continuously evaluating the quality of WIP units through the manufacturing process and managing WIP unit mix and flow to generate improvements to economic value of the finished product relative to the cost of raw materials.
The PES System consists of two inter-linked products: a process measurement and control system (“PMC System”), and a set of inter-tool measurement and sorting units (“MS Units”). The MS Unit has two variants—a measurement-only version (the “Measurement MS Unit”), and a combined measurement and handling version (the “Measurement/Handling MS Unit”). The MS Unit of the preferred embodiment is designed for use in c-Si PV wafer or cell factories as an example. The PES System is shown generally in
The PES System 10 comprises a PMC System 12 connected through a ProfiNET/Ethernet IP/EtherCAT 16 to one or more inter-tool measurement and sorting units, the MS Units 14.
The PMC System 12 generally consist of a computer server comprising system software for operating a manufacturing production line for manufacturing photovoltaic products, including receiving measurement data 18 from the MS Units 14 and providing queuing and transfer instructions 20 to the MS Units 14. Each MS Unit 14 provides measurement data 18 through the ProfiNET/Ethernet IP/EtherCAT 16 to the PMC System 12 for the particular production stage or step of the production line with which the MS Unit is configured to operate. Similarly, each MS Unit 14 receives queuing and transfer instructions 20, as appropriate for each particular MS Unit 14 from the PMC System 12. Instructions 20 being appropriate for the particular MS Unit's operations in respect of the production step or steps for which it has been configured and in association with which it operates.
It should also be noted that other tools or instruments 22 and 24 may be connected to ProfiNET/Ethernet IP/EtherCAT 16 to provide appropriate tool or instrument measurement data 26 to PMC System 12.
As well, PMC System 12 can be configured to operate in association with manufacturing enterprise systems 28 of the operator of the manufacturing production line through Ethernet 30 to send and receive data, instructions and other information between system 28 and PMC System 12 in order to ensure that the manufacturing production line operates within the parameters of that operator's entire system.
The Measurement MS Unit inspects and grades each WIP unit according to programmable criteria, and passes this information to its controlling PMC System. The Measurement/Handling MS Unit also unloads WIP units from a process tool, and sorts, buffers or rejects each WIP unit according to instructions from the PMC System received after the Measurement/Handling MS Unit has passed the WIP unit grading information to the PMC System. In this case, the output of each MS Unit (as input to the next production stage) is then an optimally ordered “lot” (for batch processes) or “flow” (for continuous processes) of WIP units.
The PMC System consolidates measurement results from any number of MS Units and other sources (such as WIP unit flow rates and status measurements from PVD devices, laser isolation systems, etc.). The PMC System uses this information to direct each of the Handling/Measurement MS Units installed in a given facility to buffer or sequence individual WIP units for advancement to their respective next stage of production. The goal is to exploit variations in WIP unit quality—continuously and in-line with the end-to-end production process—to maximize the aggregate economic value of finished goods in the facility.
PMC System 12 of PES System 10 is shown connected to several MS Units 14 shown in a manufacturing production line 32.
An initial MS Unit 36 is associated at the beginning of the c-Si cell manufacturing process shown in
The next step in production line 32 is the washing and etching step 42 where the wafer from production step 38 is washed and etched by wet processing tools that remove saw marks, remove edge irregularities and create a surface texture to enhance photon capture. A second MS Unit 44 inspects the wafer exiting washing and etching step 42 for physical characteristics related to satisfactory removal of the saw marks and edge irregularities as well as creation of surface texturing and sends that information to PMC System 12 through communication bus 40. PMC System 12 then analyzes that data in order to grade the wafer by one or more of the methods below and sends instructions to second MS Unit 44 to either discard (or recycle), buffer or advance the wafer so inspected to the next step.
The next step in production line 32 is the diffusion for P/N junction step 46 where the wafer is doped to create the emitter. This may be implemented in two ways. In the first way, it may be implemented whereby the wafer has a wet film of dopant applied to its top surface, the film is dried, and then the dopant is diffused into the wafer in a furnace. In the second way, it may be implemented whereby the wafer is inserted into a furnace and the dopant is simultaneously introduced in a gaseous form during diffusion. After treatment at step 46 the wafer is examined by MS Unit 48 which inspects the wafer for the dopant concentration in the emitter and sends that information through communication bus 42 PMC System 12. If the first way is used, the wet film depth and distribution on the wafer may also be examined prior to the wafer entering the furnace. PMC System 12 then analyzes that data in order to grade the wafer by one or more of the methods below and provides instructions to MS Unit 48 to either discard (or recycle), buffer or advance the wafer so inspected to the next step in production line 32.
The next step in production line 32 is the removal of phospho-silicate glass and etching of the top and bottom surfaces of the wafer step 50 where the wafer is again processed through a series of wet etching tools. A further MS Unit 52 inspects the wafer leaving the removed phospho-silicate glass step 50 to determine the adherence of these etching steps to the desired specification, and sends that information to PMC System 12 which analyzes the data in order to grade the wafer by one or more of the methods below and returns instructions to MS Unit 52 to either discard (or recycle), buffer or advance the wafer to the next step of the manufacturing production line 32.
In this example at this step, after removal of phospho-silicate glass and top and bottom etching, the wafer is checked by MS Unit 52 to determine the sheet resistance or dopant concentration at particular locations and depths within the wafer. If these values are above or below a predetermined range of values as defined by the operator of the PES System 10, this measurement may be used at this production step for classifying or grading the wafer at a particular predetermined class or grade for sheet resistance or dopant content and distribution. This classification/grade is combined with other classification/grades on other criteria that were determined for that wafer in previous steps (such as the RMS texture peak-to-valley distance after isotropic texturing) to determine an aggregate grade for the wafer, to be compared by PMC System 12 to its database (or knowledge base) of aggregate grades at that production step (that is phospho-silicate glass step 50).
The next step in the production line 32 is edge isolation step 54 where the wafer is etched around its perimeter to remove any short circuits between the emitter and base and inspected by MS Unit 56 for the continuity and depth of such etching. That information is sent to PMC System 12 by bus 40 where the information is used to create an aggregate grade for step 54. At this time, the aggregate grade may be used to make the decision as to whether the wafer will be discarded (or recycled), buffered (that is placed in a specific group for processing as a group) or advanced to the next step. Alternatively, or additionally, the information may be used by PMC System 12 to establish a grade specific to step 56 (that is not on an aggregate basis with previous steps) to compare with a database/knowledgebase of grades specific to that step. As a further alternative, or further In addition, the information from MS Unit 56 can be used to determine a grade, per se, without comparing the information to a database/knowledgebase of prior WIP units. The grade information of each, or any one or more, of these alternative methods of grading is then used to assess the wafer to determine whether either discard (or recycle), buffer (with other like wafers) or advance the wafer so inspected to the next step in production line 32. PMC System 12 sends instructions to MS Unit 56 to either discard (or recycle), buffer (with other like wafers) or advance the wafer so inspected to the next step in production line 32.
This process of grading the wafer (or any other WIP unit) can be applied at any selected process step described above or as follows, of production line 32. That is grading by one or more of:
The next step in the production line 32 is the application of the anti-reflective coating (ARC) step 58 where the wafer is coated with a silicon nitride or equivalent chemical. MS Unit 60 inspects the wafer leaving ARC step 58 for the color, depth and uniformity of the coating. That information is sent through communication bus 40 to PMC System 12 where it is graded by one or more of the grading methods above. PMC System 12 then provides instructions to MS Unit 60 to either discard, buffer or advance the wafer to the next step in the production line 32.
The next step in the production line 32 is the printing step 62 where the wafer has the back electrical contacts, the back aluminum surface and the front electrical fingers and busbars applied. MS Unit 64 then inspects the wafer exiting screen printing step 62 for the physical quality of these printings and sends that information through communication bus 40 to PMC System 12. PMC System 12 then analyzes that information in order to grade the wafer by one or more of the methods above and provides instructions to MS Unit 64 to either discard, buffer or advance the wafer to the next step in the production line 32. Optionally, there could be a separate inspection after application of each of the back contact, back aluminum and front contacts.
The next step in the production line 32 is the annealing of the printed metal features applied in step 62 at step 66 where the wafer is passed through an annealing furnace. The wafer is then automatically advanced to the next step, the sorting step 68 can be seen here that not every step in the manufacturing production line 32 may necessarily include an MS Unit appropriately configured for that step. A wafer may proceed automatically from one step to another without the intervening measurement by any MS Unit 14 or any control from PMC System 12 at that step. Much will depend on the needs of a particular operator of the manufacturing production line 32. Inspection can also occur after the annealing furnace. That inspection would be to determine that the metal features had penetrated into the wafer correctly and maintained a correct physical orientation on the front and back surfaces of the wafer.
After sorting steps 68 the wafer is subjected to an inspection by MS Unit 70 which inspects for any final criteria as may be determined by the manufacturer, such as bar codes or visible defects introduced during sorting as the final inspection step in the manufacturing production line 32. MS Unit 70 then provides that information to PMC System 12 through communication bus 40. PMC System 12 then analyzes that information in order to grade the wafer by one or more of the methods above and provides instructions to MS Unit 70 to either discard or advance the wafer to a storage area or packaging area for shipment.
The MS Units provides a complementary function to the process tools by linking them together to achieve a continuous production flow—whether in a single production line or across multiple lines within a large facility.
The general mainline operational flow of the PES System is shown in the flowchart of
In general, the MS Units 14 function as the measurement and first level control computers. MS Units 14 talk to the PMC System 12 across the network, sharing measurement and control data so that the PMC system 12 can make decisions on the overall process. For example, there may be 5-10 MS Units 14 measuring and controlling each step (or selected steps) of the process. A set of algorithms in the PMC System 12 solve the optimization of the flow of wafers (or other WIP units) through production line 32—deciding which wafers are grouped together (based on their individual allocated grades), how they are processed downstream, and other types of processing decisions, which are passed on to the MS Units 14 for controlling the operations at particular process steps. Together, these make a PES System 10.
Referring to
As seen in
The networked nature of the PMC System 12 and MS Units 14 is inherently scalable. However, each MS Unit 14 itself should be configurable to allow for insertion in varying portions of the production line, and to support facility expansion. The MS Unit 14 hardware and software architecture to support this unit-level scalability is described below. In the PES System 10, the software architecture may also be designed for scalability—from interaction with a single PMC System 12 configured for “single-lane” operation to up to 50 MS Units 14 with multi-lane and line-switching capabilities.
One aspect of the invention provides a system in which multiple MS Units are placed between process tools in a manufacturer's production line, and a PMC System is networked to all those MS Units and (optionally) other third-party sensors and an ERP system. The architecture may also include the operational process software (software that links together the data from each MS Unit and makes factory-wide optimization decisions): the PMC System's integration of measurement data generated by the MS Units and third-party sensors, its use of this and other data to make factory-wide production flow control decisions, and the MS Units collective physical implementation of the PMC System's decisions on WIP units.
Referring to
In contrast to other material handling systems, the PMC System of the present invention directs and implements the flow control of WIP units as a “gestalt” throughout the entire production facility. That is, the PMC System fully encompasses and integrates real-time measurement; in-line control decisions based on these measurements; and real-time WIP unit handling to implement these decisions. Within the scope of this invention each WIP unit is tracked, and WIP unit sequencing, routing, rejection and buffering decisions are made continuously in a discrete-time control process by considering the status of all WIP inventory in the system, simultaneously and in parallel. This can be implemented because the PES System is unique in providing the WIP unit measurement, facility-wide production controller and WIP unit handling and transfer capabilities that are specifically designed to work in concert, in real-time and with a stable control loop.
As further provided within the scope of this invention, the Measurement/Handling MS Unit is a modular, configurable measurement and handling unit. Its unique design incorporates a configurable and scalable handling strategy. This provides for consistent handling throughout the manufacturing facility and cost-effective re-use of technology, even when individual MS Units are configured for different process tool interfaces and inspection tasks.
This feature of the present invention provides for the ability to uniquely identify and track individual cells, panels or modules—without the aid of special markings or tags—a unique capability enabled by the integrated real-time data management between the PMC System and all MS Units in a production facility, and the in-line measurement in each MS Unit. This tracking is done by either or both of:
This tracking is necessary for implementation of the predictive WIP unit grading algorithm, and for WIP unit production flow queuing and sequencing/routing. If a facility implements all of its handling with MS Units, the exact location of each WIP unit in the production line(s) can be known at all times with just the spatial tracking. If there is uncertainty regarding the handling or if line operators make non-recorded interventions that change WIP unit locations, the measured characteristics method, or wafer edge coding method, or both, are recommended to be used—either with or without spatial tracking. Generally an approach using at least two of these methods in tandem is expected to be most robust.
This feature of the present invention provides for the ability to hold or “buffer” WIP units at any MS Unit in the system. The method of physical implementation of this is described below. The method of buffering is centrally managed on a facility-wide basis from the PMC System. The purpose and use of WIP unit buffering is at least four-fold. First, buffered groups of WIP units are located at the MS Units for the purpose of substitution of “good” WIP when an opening is created in the production flow by the rejection of poor-grade WIP at that MS Unit. Second, faulty WIP is buffered to provide the ability to group it into “lots” for downstream mitigation of the faults. Third, WIP is buffered to also allow re-sequencing into lots that are based on business requirements. Finally, WIP is buffered to allow for a continuous flow of material through the line when individual process tools or material handling devices need to be taken off-line for scheduled maintenance or other reasons (including unscheduled shutdowns or errors).
At some steps in cell, module or panel production, WIP units may have a limited period of time in which they are usable for further processing. (Colloquially speaking, they can go “stale” if held in a buffered group too long at these stages). The WIP buffer management algorithm of the PMC System is designed to recognize this (based on data input from the manufacturer) and provides a “buffer refresh” capability that ensures that WIP units that are approaching their time limit for usability are cycled back into the manufacturing process and replaced with equivalent “fresh” WIP units.
The amount of WIP located at any given buffered group is determined by the following factors in combination:
In-line inspection is the act of inspecting every WIP unit during the production process, without removing the WIP units from the production flow. This feature of the present invention provides for coordinated in-line inspection by providing inspection undertaken by each MS Unit as they move WIP units from one stage in the production facility to the next. Additionally, the inspection algorithm is distributed and cumulative—meaning that each MS Unit can apply different sensors and sensor output processing to measure different characteristics of a particular WIP unit as it moves through production. The sum total of all of these diverse inspections, cumulatively, as they occur, can be used to grade or assess the WIP unit. The distributed and cumulative nature of the inspection process also provides a more cost-effective means to thoroughly measure and grade WIP units than traditional end-of-line grading and sorting.
A quality algorithm (“Quality Algorithm”) determines at what final quality level a partially finished WIP unit is destined. (“quality” is a pre-defined function of the measured WIP unit features or attributes (defects or otherwise), conditioned by their relative importance, as specified by the customer). The algorithm relies on a feature correlation database that enumerates individual WIP unit features and their co-incidences at various points in the end-to-end fabrication process. The database must contain a statistically valid number of measurements (thousands of WIP units tracked through the process). By using the database, a WIP unit can be predictively graded at any point by comparing its features to the end result of other WIP units with statistically similar features at the same stage in fabrication. If the prediction falls within a user-defined confidence level, then, as described in the next paragraph, a decision can be made regarding sequencing (or line-switching) of the WIP unit, or even outright rejection from the production line(s). Repeating this process later in fabrication allows refinement of the grading and re-sequencing such that, ideally, all WIP units are ordered based on the desired production targets and precisely graded by the end of the line.
This feature of the present invention provides for the reduction of the incidence of damage or handling errors caused by the MS Unit (or any other handling device that can be interfaced to the PMC System). What is controlled, for every handling device in the system, is their WIP pick-up orientation, timing (approach, dwell and take-off) and forces (gripper-related, accelerative and jerk), transfer velocity, acceleration and jerk, and placement orientation, timing and forces, for each individual WIP unit. If a particular WIP unit is predicted to be impossible to handle without causing breakage or mis-handling that might require a system stoppage, it is flagged and ejected from the production line prior to an attempted pick-up.
The preferred way this is accomplished is as follows:
In summary, if the system observes a wafer or cell that is going to break downstream, the system directs the next robot downstream to handle it carefully or reject the cell and replace it with good WIP. This comprises feed-forward adjustment of handling to minimize breakage or eliminate cells that will fail. This is all designed to improve cell production line performance and reduce the cost of unnecessarily processing cells that would break with downstream processing.
This algorithm is a further feature of the present invention that works in tandem with the Quality Algorithm and WIP unit tracking capabilities to enable the grouping of WIP units in like categories or grades throughout the production facility. On a facility-wide level the algorithm coordinates the MS Units to act as a network of routers—buffering WIP units, switching WIP units between lines and (re) sequencing and routing WIP units to achieve the desired output lot size and consistency to facilitate down-stream processing or customer order management (as specified by ERP input). It can also implement goal-seeking measures—most notably DRT, described below. Multi-line WIP routing is illustrated below.
This feature of the present invention provides for automatic continuous adjustment of the quality threshold at which WIP units are deemed “scrap”, in order to maximize the factory's economic output. At a given point in time, an adjustment decision is made based on a predictive measure of the cumulative value of all WIP units in the production line(s), compared against the cost of scrapped WIP units. The rejection threshold is set to maximize the cost-benefit equation (subject to some constraints that can be set by the operator). The unique DRT feature is enabled by the PMC System's ability to consolidate and process real-time measurements from all MS Units in a production facility.
By comprehensively measuring the quality of WIP units not just at the “end of the line”, but also at the outputs of the individual processes during their fabrication, the PES System builds and maintains a production performance database that can be uniquely used to monitor, analyze and report on the performance of each tool, tool group (i.e. portion of the fabrication process), and the overall production facility. This may be used for the following purposes:
As shown in
The linear and matrixed archetypes can be deployed independently or in combination in one or more manufacturing facilities. Multiple PMC Systems may be installed to support these configurations. Examples of these archetypes are shown (combined) in
The PMC System consolidates and inter-relates measurements from sensors located in various MS Units and may also be attached to other devices and systems in a particular unit manufacturing facility. It uses this information to direct the actions of the MS Units. As such, it is a facility-wide controller for managing aspects of the WIP unit flow through the facility.
Preferably an PMC System is comprised of the following major elements:
Two categories of software may form part of the PMC System. One category is standard third party software—most importantly the operating system and the database management system. The other category encompasses all proprietary software of the applicant required to program, configure, operate, administer and maintain the product.
Both the third party and applicant proprietary software may be provided to the customer as a single distribution (pre-loaded on the PMC System computer and as a backup DVD-ROM).
In a preferred form the applicant proprietary software comprises the following elements:
A high-level operational flow of the PMC System is shown in
The PMC System provides discrete feedback control for the flow of WIP units through the PV manufacturing facility. For each discrete time slice (or system “clock tick”) the PMC System receives information from all of the MS Units in a facility, plus measurements from any third-party devices (such as process tools) that are networked to it. Each WIP unit is uniquely identified by a tracking methodology.
The measurements pertaining to each WIP unit are added to a record, kept by the PMC System, which aggregates all of the measurements taken for that WIP unit as it progresses through the production process. Part of this record is also a “quality factor” (Q) for each WIP unit that (as an example in the case of c-Si cells) is a function of the following:
At any stage in the fabrication of a WIP unit, its quality factor is a predictive estimate based on incomplete information. A WIP unit's quality factor is determined using the Quality algorithm, and takes the general form:
Q=f(A,G,E,D)
where A is aesthetics, G is geometry, E is photo-electrical and D is defect.
Part of the process of determining the Q for a given WIP unit is the use of the defect correlation database to assess images of the WIP unit against known defects and determine the degree to which the WIP units have such defects. The closer the observed defects are in the WIP units to the stored defects, the closer D is to 100%. The closer the color image is to the desired color image, the closer A is to 100%. The closer the WIP unit geometry is to the target geometry, the closer G is to 100%. The closer the electrical performance is to the desired electrical performance, the closer E is to 100%.
The measurement results are also added to a database that tracks the results for each stage of the production process (the True Production Measurement Database). This database can be queried (and logs and alarms set) for the purposes of implementing the TPM feature, as described herein.
Once all of the WIP units have had their Q factor updated, they are assigned updated gradings, as defined by the customer. After this, the DRT algorithm (as described above) is invoked to update the quality threshold QT below which WIP units are rejected. Then the optimal facility-wide WIP unit ordering, (more specifically WIP unit sequencing—and routing, if multiple production lines exist in the facility) is determined, and the PMC System calculates and sends the specific WIP unit transfer, line switching, buffering and rejection instructions needed, to each MS Units to enact this sequencing and routing.
In accordance with the present invention, the Measurement MS Unit is a measurement device, and the Measurement/Handling MS Unit is a combined handling and measurement device. MS Units are placed between process tools to measure and/or effect the flow of WIP units through the PV manufacturing facility. MS Units may be placed singly or in parallel between tools.
MS Units are placed between process tools to measure and/or effect the flow of WIP units through the PV manufacturing facility. MS Units may be placed singly or in parallel between tools. Measurement/Handling MS Unit hardware architecture is depicted in
MS Units are comprised of some or all of the following major elements:
Computer program elements of the invention may be embodied in hardware and/or in software (including firmware, resident software, micro-code, etc.). It may take the form of a computer program product, that can be embodied by a computer-usable or computer-readable storage medium having computer-usable or computer-readable program instructions, “code” or a “computer program” embodied in the medium for use by or in connection with the system of the present invention. In the context of this application, a computer-usable or computer-readable medium may be any medium that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The computer-usable or computer-readable medium may be, for example but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, device, or propagation medium such as the Internet. Note that the computer-usable or computer-readable medium could even be paper or another suitable medium, upon which the program is printed, as the program can be electronically captured, via, for instance, optical scanning of the paper or other medium, then compiled, interpreted, or otherwise processed in a suitable manner. The computer program product and any software and hardware described herein form the various means for carrying out the functions of the invention in the example embodiments. Also, while software in the memory or in some other memory of the computer and/or server may be used to allow the system to carry out the functions and features described herein in accordance with the preferred embodiment of the invention, such functions and features also could be carried out via dedicated hardware, firmware, software, or combinations thereof, without departing from the scope of the invention.
Although the invention has been shown and described with respect to a certain preferred embodiment or embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed figures. For example, regard to the various functions performed by the above described elements (components, assemblies, devices, software, computer programs, etc.), the terms (including a reference to a “means”) used to describe such elements are intended to correspond, unless otherwise indicated, to any element that performs the specified function of the described element (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure that performs the function in the herein illustrated exemplary embodiment or embodiments of the invention. In addition, while a particular feature of the invention may have been described above with respect to only one or more of several illustrated embodiments, such feature may be combined with one or more other features of the other embodiments, as may be desired and advantageous for any given or particular application.
This application claims the benefit of U.S. Provisional Application No. 61/180,744, filed May 22, 2009 and U.S. Provisional Application No. 61/272,407, filed Sep. 22, 2009, the contents of each of which are hereby incorporated by reference in their entirety.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/CA2010/000772 | 5/21/2010 | WO | 00 | 2/20/2012 |
| Number | Date | Country | |
|---|---|---|---|
| 61180744 | May 2009 | US | |
| 61272407 | Sep 2009 | US |
