3 tool producers interface with NVS

Electronic News, March 4, 1996 by Judy Erkanat

Cambridge, Mass.--March is coming in like a lion for New Visions Systems, Inc. (NVS) with three tool manufacturers offering interfaces to NVS' products and an award of a patent on its wafer pattern overlay registration methodology.

Overlay tool producers Bio-Rad, Interactive Video Systems, Inc. (IVS) and Optical Specialties, Inc. (OSI) are now offering direct, real-time interfaces to NVS' Mono-Lith analysis package.

"Mono-Lith Real Time enables semiconductor manufacturers to analyze wafer production data for errors on a lot-by-lot basis in a matter of seconds." said Joseph Pellegrini, NVS president.

The overlay tools automatically send data directly to the Mono-Lith workstation, which performs a pre-programmed wafer stepper analysis and sends the results back to the production floor. Since IVS introduced the first such interface for its product in 1994, over half its customers purchased the system.

"The interface has revolutionized overlay registration measurement, changing it from simply an adequate process monitoring step to an advanced process diagnostic application," said Robert Newcomb, product support manager at IVS. "By modeling each production lot for grid and intrafield errors, the interface allows the process engineer to use overlay data to monitor the process and the equipment simultaneously. This leads to improved process capability and increased chip yield."

The interface, available as an option on the IVS-120 Optical Overlay and CD Measurement system, makes interfaced to overlay tools compliant with NVS' Argus family of automatic control and product disposition software. Many metrology equipment vendors already have access to Argus components and, according to NVS, intend to embed its interfacing and analysis capabilities into tools scheduled for shipment 2Q96. NVS also plans to release supplementary, stand-alone Argus analysis systems to a limited number of customers this year. Full integrated Argus analysis systems will be available worldwide 1Q97.

Mono-Lith is priced between $20,000 to $50,000 per seat and is shipping now.

NVS was also awarded U.S. patent number 5,444,538 for its method to improve overlay registration between mix-and-match wafer steppers by up to 30 percent. The company will implement the patented method, developed at the request of Ultratech Stepper, in NVS' Argus non-concentric matching software, a member of the Argus family of automatic control and product disposition software, currently under development.

"As lithography becomes more complex and critical dimensions go well into the submicron range, the error budget becomes a limiting factor that keeps manufacturers from getting the maximum performance, productivity, and return on investment from their steppers," said Mr. Pellegrini, creator of the patented method. "Use of Argus non-concentric matching software will reduce the error budget allowing manufacturers to use mix-and-match techniques to build next-generation ICs with smaller geometries and tighter tolerances."

The patent uses a new technique to make the most of the overlay of two or more pattern layers produced by steppers with different field sizes. "Historically, we found that all optimization techniques assumed concentric matching--that the centers of all the exposure fields for the different layers were in the same location," Mr. Pellegrini said. "That's true in a homogeneous manufacturing environment where all field sizes are the same, but in a mix-and-match environment, exposure fields are non-concentric."

By eliminating this concentric assumption, NVS derived an equation optimizing the entire system for non-concentric environments. In a typical mix-and-match environment, the Argus product will improve overlay accuracy by an extra 40-50 nanometers.

"The main value of this method is in processes that are overlay limited," said Mr. Pellegrini. "Today's advanced wide-field steppers with 0.65-micron resolution are required to align with layers containing 0.35-micron structures. At that level, a savings of 40-50 nanometers becomes significant."