Chipmaker TSMC is set back by a bad photoresist

A production outage at a semiconductor maker is providing a window into the computer chip industry’s dependence on its suppliers of high-purity materials—and what can happen when something goes wrong with those chemicals.

Taiwan Semiconductor Manufacturing Company (TSMC), the world’s largest contract chipmaker, disclosed to investors late last month that it had to halt one of its production lines in Taiwan after it discovered subpar devices. TSMC traced the problem to a bad batch of photoresist, the light-developable polymer used to create circuit lines, from one of its main suppliers.

Industry sources say the firm’s key photoresist suppliers are Dow Chemical, JSR, and Shin-Etsu Chemical.

The production line was making chips with 12 and 16 nm circuitry, one of the firm’s more advanced technologies. TSMC says it expects to make up for the loss in the coming months.

The core photopolymers used to create 12 and 16 nm circuit lines are typically acrylics based on three or four coreacted monomers, according to Mark Thirsk, an analyst with the electronic materials advisory firm Linx Consulting. The polymers are chemically amplified to boost the development process. The formula also contains quenchers, surfactants, solvents, and photoacid generators, which aid in the chemical amplification.

“The spec sheets for these sort of photoresists are horrendously complicated,” Thirsk says.

He speculates that TSMC’s problem was caused not by a contaminant but by some almost-undetectable variation in a photoresist component. “It could be the effect was so subtle that it got through all the quality testing,” Thirsk says.