Next Big Challenge for PV Makers: Wafer Handling

The push to crank out solar cells more quickly brings problems as manufacturers work with ever-thinner silicon wafers. Solar power still costs more than energy gained from burning coal or gas. That fact may put opponents of subsidies up in arms, but it’s great for companies that automate photovoltaic (PV) manufacturing lines. The reason: “Solar is driven by yield and throughput right now. They are trying to drive down the cost per solar cell so the technology approaches the economics of conventional energy,” explains Dan Tracy, senior director of industry research and statistics at , the overarching organization for the semiconductor industry. The push to drive down costs and boost throughput is proving to be a boon for systems integrators and for automation companies. Overall spending on semiconductor- manufacturing equipment is down by double digits this year, but that’s not the case for companies supplying automation gear to the solar industry. There’s a lot to do. “I would equate the PV industry today with the semiconductor industry in the early 1980s,” says Chief Technical Officer Dave Pap Rocki. About 75% of Adept’s Quattro robots sold so far have gone into PV applications, says Pap Rocki. “A lot of the manufacturing processes in PV are just now being defined. It took SEMI to standardize the equipment in the semiconductor industry, but there has been no such effort in solar. So there are a lot of inconsistencies with shapes as, for example, with the interface to wafer transfer boats,” he says. One factor that is complicating the task of handling solar-cell material is a trend toward thinner silicon wafers. Raw silicon has been expensive and in short supply. So there is an incentive to use as little as possible. This has led the industry to find ways of making substrates ever thinner, in some cases only about 100-microns thick. These wafers are delicate and notoriously difficult to handle without inducing damage in the form of chipping and cracking. Moreover, state-of-the-art PV wafers are thinner than those for conventional ICs. They are manufactured in