Photronics to beta SiScan's mask tool

Electronic News, Nov 18, 1991

MILPITAS, Calif. -- Photronics Inc., an independent photomask producer, has agreed to act as a beta site for Campbell, Calif.-based SiScan Systems Inc.'s new mask metrology equipment.

The $1.6 million Impact-7000 (for integrated mask processing advanced cluster tool) automatically aligns, locates and measures user-selectable critical-dimension locations on the photomask from behind the glass, with accuracy specified at 0.003 micron, said Barry K. Rockwell, director of engineering at Photoronics. "That's about 300 times more accurate than what one of our more stringent tolerances for a single line are," he added.

Michael Mulholland, vice president of marketing and sales for SiScan, said the system is fundamentally, different from those in use today, both from a process and automation standpoint.

"In the manual systems that are used today, when you make a measurement prior to final etch, you measure over the resist. This creates an inaccuracy because the resist acts like a phase-shift mask," said Mr. Mulholland. "This system turns the whole process over, letting you measure through the glass rather than through the resist."

"The fact of the matter is that all conventional metrology approaches are fundamentally incapable of accurately measuring chrome features under an intact resist pattern," said Scott Landstrom, chief executive of SiScan. "We think we have solved this probelm in a way that our customers will be able to precisely and automatically 'dial in' their iterative process right on target value."

The highly automated cluster configuration further ensures reliability by eliminating human error, said Mr. Rockwell.

"With the present process, humans have to do the measuring for you. This system includes a confocal microscope with chemical processors and a robotic system, which in today's manufacturing environment is the equivalent of about 12 people. It's nonlabor-intensive, it reduces costs and its increases reliability substantially," said Mr. Rockwell.

Mr. Rockwell said Photronics is pleased with the system because it puts them "ahead of market requirements" for mask inspection systems, and it gives them "a marketing advantage" because the system's accuracy adds substantial value for the customer.

The system, which measures masks at a rate of about 10 per hour, has already been used to measure prototype masks for 16-and 64-megabit dynamic RAMs, said Rockwell. He declined to name the customers or give out more details.

Mr. Rockwell said the system is initially being used to support the Ateq Corp. laser-based Core reticle-engraving system located in Photronics' Milpitas facility, "but we also have plans to extend the Impact application to MEBES- and optically-generated photomasks."

Mr. Mulholland said SiScan expects to have the system ready to ship around August or September of next year. The company is also negotiating manufacturing and distribution rights in the Pacific Rim with Ishikawajima-Harima Heavy Industries Co. Ltd. of Japan. IHI has a joint development agreement with SiScan (EN, May 6).