PV Standards

Another industry with that same potential is the photovoltaic industry. Addressing growing global energy needs while balancing environmental concerns is the major challenge of this century so far. Solar energy generation and distribution has the opportunity to become the one of the next great advances in human society.

Several factors drove the widespread adoption of semiconductor transistors. Increasing capability with reduced chip size and cost (as described by Moore’s Law) ultimately pushed the industry to create entire processors as small as a grain of rice. While impressive, this development was enabled by the global development and implementation of industry standards that allowed industry to focus on research and development that added value to the production and manufacturing processes. This led directly to improved technology and reduced costs, enabling widespread adoption.

Such standards were agreed upon by the semiconductor industry as far-sighted executives recognized the need for efficient capital investment. SEMI (the global industry association serving the manufacturing supply chains for the microelectronic, display and photovoltaic industries) was founded in 1970 to foster the growth of the semiconductor industry, and the SEMI International Standards Program was established to first address silicon wafer size specifications.

Executives quickly saw the value in a common understanding of wafer sizes, materials specifications, communication interfaces, and other critical factors, such as environmental, health and safety (EHS). This same recognition is spreading throughout the photovoltaic industry as companies throughout the supply chain recognize the value of establishing common standards on which to build innovation and process improvement. Indeed, standards are of such critical importance to manufacturing industries that a DIN (German Institute for Standardization) report notes that standards contribute more to economic growth than patents and licenses.

The Need for Solar Photovoltaic Standards

Today, the PV industry has few standards to support the manufacturing process or to help achieve cost reduction and process efficiency goals. As the market grows rapidly (some 40% per year, rising to an estimated €40 billion by 2010), many new companies will enter the manufacturing supply chain. The development and widespread adoption of standards will make it easier for these companies to both meet growing demand and to innovate in meaningful and valuable ways that advance the industry.

The value of standards has been proven in many industries around the world. Machine tools, lighting, communications and automotive fields all have standards that are universally adopted and used as a foundation for real innovation and production efficiency. The role that standards play can be defined as: bringing the global supplier and customer communities together; collectively reducing the number of options in a given process; and, agreeing on common parameters and terminology.

Photovoltaic Manufacturers Meet and Agree

The demand for quality silicon has been rising as the demand for solar energy and solar cells to produce energy has soared. A major problem with sourcing this material has been the lack of a standardized test method for detecting elemental impurities in photovoltaic silicon feedstock. To address this issue, the industry used the SEMI International Standards Program platform to develop and publish SEMI PV1: ‘Test Method for Measuring Trace Elements in Photovoltaic-Grade Silicon by High-Mass Resolution Glow Discharge Mass Spectrometry’.

Task force leader Richard Hockett of Evans Analytical Labs described the need for the standard, stating: ‘Although the total annual volume of silicon feedstock that goes into silicon solar cells has now surpassed the total annual volume of polysilicon used in the silicon semiconductor industry, SEMI PV1 is the first standard test method that specifically addresses the evaluation of some types of PV silicon feedstock. By standardizing this test method, the PV industry now has an international “ruler” that can be used for commerce.’

Of course, new standards take into account and rely on existing standards. SEMI PV1 relies on existing standards SEMI MF397-02 for measuring net resistivity, SEMI MF1389-00 for measuring dopants by photoluminescence, SEMI MF1724-01 for measuring surface metal contamination on granules, chunks or powders by acid extraction followed by atomic absorption spectroscopy, SEMI MF1188-1105 for measuring interstitial oxygen by Fourier Transform Infrared Spectroscopy, SEMI MF1391-0704 for measuring substitutional carbon by Fourier Transform Infrared Spectroscopy, and SEMI MF1630-0704 for measuring dopants by low temperature Fourier Transform Infrared Spectroscopy.

The next need this group will address is the ‘solar-grade silicon specification’, to be developed in collaboration with EPIA, the European Photovoltaic Industry Association, in the SEMI International Standards Program. Eight major companies are already supporting this effort (Dow Corning, Elkem Solar, Hemlock, PV Crystalox Solar Silicon, Wacker Chemie, REC, Siliken and Sunicon) and the specialized Dutch research centre, ECN, which brings experience gained during the recently finished European Project Crystal Clear. Daniel Fraile, the scientific officer of EPIA expects the results of this activity to be published before the autumn of 2010.

Another notable new effort will focus on PV wafer and cell carriers, as automated material (wafer and cell) handling is a prerequisite for efficient PV module fabrication. In reality, however, PV manufacturers and equipment suppliers have been spending significant time and effort on material handling within their production lines, distracting them from focusing on their core competencies. This new effort, led by Q-Cells, will also enable standardization of equipment load ports and transport systems, resulting in both direct and indirect cost savings throughout the whole supply chain, less risk during ramp-up and less effort for integration of the production line.

Communication Is Key

The next standard that was developed and released was SEMI PV2: ‘Guide for PV Equipment Communication Interfaces’. This standard addresses a unified communication standard between PV production equipment and the shop floor.

As Martin Zennig of Jonas & Redmann Automationstechnik GmbH (Berlin) says: ‘A lot of projects require us to develop and implement customer specific interfaces; this is time-consuming for the specification and development phase. In most cases the manufacturing execution system (MES) was not ready when we delivered our equipment, and no proven test tools existed, so these specific interfaces could not be tested in-house. This meant that bugs came up (and had to be solved) during the ramp-up time of the production line or (worst case) within production time. This is clearly time-consuming and expensive for both the equipment supplier and the customer.’

This is similar to the state of the semiconductor industry in the 1980s, when this lack of a standard was recognized as a major roadblock to efficient manufacturing. The development and implementation of SEMI Equipment Communication Standards/Generic Equipment Model (SECS/GEM) resulted in a reduction in the cost required to automate a factory, increasing throughput and efficiency, thus adding great value to the industry. PV2 is expected to reduce the effort that photovoltaic equipment suppliers have to spend to develop and maintain a variety of equipment communication interfaces, and establish the foundation for deploying advanced factory management and control software systems.

But with SEMI PV2, Zennig says, ‘...many proven libraries and products for SECS/GEM-based communications do exist on the market, and the know-how (mostly coming from semiconductor software suppliers) is available. An OEM can decide the level of detail he wants to put [in], for example, you can develop all from scratch by yourself, use proven libraries or completely order a fully running solution on the market and you can be sure that it will work. Now, we have a standard interface ready for each project, which significantly reduces specification and development time for each project. Also, the interface can be tested before the equipment is shipped to the customer, this reduces the time our employees need to stay at the customer side during ramp-up and so they can be used earlier for other projects.’

SEMI PV2 marks a significant industry milestone, as it defines a unified equipment communication interface for PV production systems, and is expected to provide multiple benefits to the PV industry, including shorter ramp-up times, increased functionality, simplified requirement specifications, and increased potential cost savings for manufacturers.

Today’s PV production lines demonstrate an increased need to control production equipment from external software systems and also to acquire data from production equipment, regardless of the base technologies (silicon, thin film) being used. As Matthias Meier, from the Fraunhofer Institute, a key leader in development of SEMI PV2, states: ‘Tasks such as equipment efficiency monitoring, maintenance management, scheduling, dispatching, work-in-progress tracking, yield optimization and process monitoring and control are either fully automated or at least strongly supported by shop floor IT systems that depend on being able to communicate with production equipment. The ability to communicate with production equipment from an IT point of view is a prerequisite to operate PV manufacturing systems at maximum efficiency.’

By implementing this SEMI Standard, manufacturers will no longer have to specify, test, and integrate specific interfaces to ensure IT functionality at the factory management level, and accordingly, suppliers will no longer be required to implement and maintain proprietary interfaces for each of their customers. Other benefits include: shorter ramp-up times due to the reduction of issues related to IT integration; increased functionality available through the standardized interface – supporting more sophisticated production through advanced process control, leading to yield improvement; simplified requirement specifications; simplified testing, as integrated equipment can be tested and verified based on generic tests for all interface layers; and increased potential cost savings as manufacturers are better able to predict integration risks.

An initial tool operation specification based on SEMI PV2 has already been developed and a high level of industry usage is projected. Mathias Glaser of Manz Automation confirms the benefits of SEMI PV2: ‘Implementation of the new equipment communication standard (PV2) into Manz’ advanced equipment control architecture (aico) took less effort than initially expected. Through utilization of SEMI PV2, Manz will be able to fulfill its customers’ increasing requirements related to equipment automation.’

The Standards Development Platform

The PV industry has been active in using the SEMI International Standards development platform to publish new standards and to leverage existing standards. Participation in the Standards Program is open to all interested parties and industry is encouraged to participate. As the benefits to the industry are obvious, SEMI’s PV Group and EPIA, the two leading European solar PV organizations, are fully engaged in moving the process forward.

Given the process and equipment similarity between semiconductor and PV manufacturing, many SEMI Standards are immediately applicable to PV. SEMI Standards are well-established with a transparent process for developing international consensus manufacturing standards since 1970, which has resulted in 770 SEMI standards and safety guidelines. Today, over 350 industry volunteer experts are working in SEMI PV Standards activities that will result in reduced manufacturing cost and accepted test methods. For instance, the task force that worked on the SEMI PV2 Standard for substrate tracking included representatives from Centrotherm, Deutsche Cell, Fraunhofer, ib-vogt, Manz Automation, Oerlikon, Q-Cells, Roth & Rau, Schott Solar, SolarWorld, and many others.

Momentum is building for the development and widespread adoption of standards in the solar photovoltaic manufacturing industry. Defining future standards development efforts has been a work-in-progress as companies collaborate to define the best path without stifling innovation and business growth. Companies that participate in this development process will have access to the most current information available, and these companies have an opportunity to shape the development of the industry and their role in it. SEMI PV Group invites anyone interested to inquire about membership. To learn more, please visit: www.pvgroup.org.

James Amano is director of international standards and Stephan Raithel is senior operations manager at SEMI.