Applied Ventures, the venture capital fund of Applied Materials, has invested $3 million in Solaicx, a Santa Clara, Calif. start-up that makes single-crystal silicon wafers for the solar photovoltaic process.

Solaicx said it plans to use the investment to expand its business with a second U.S. manufacturing site in Portland, Oreg., scheduled for 2007 operation. The money comes in the form of a covertible note, part of a third round of funding that the company hopes to top off by the end of the year.

Solaicx’s technology produces high-quality ingots of silicon for solar wafers. The company says the process makes material up to five times more productive than traditional methods designed primarily for the semiconductor industry (which focused less on cost, more on precision).

The investment brings Solaicx’s total funding to $16.8 million. The company has been quiet about its funding. Almost three years ago, the company raised a $6.8 million in a first round from individuals. It then raised a second round of $7 million from the same individuals plus Labrador Ventures and Firsthand Capital. John Sedgwick, vice president and co-founder, said the company has started selling its product from a manufacturing facility at its company in Santa Clara — a facility that is testing whether the manufacturing process is working correctly. It then plans to open the Portland plant by second quarter.