Milestone research enables double patterning lithography
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Sematech and the Semiconductor Metrology Systems (SMS) division of Carl Zeiss claim to have reached a key development milestone in the development of a next generation photomask registration and overlay metrology system. The jointly developed system – called PROVE - demonstrated the measurement capability for advanced photomasks for the 32nm node and below.
In a series of test runs, the key specifications - 0.5nm repeatability and 1.0nm accuracy in image placement, registration and overlay measurement - were verified.
Bryan Rice, director of lithography at Sematech, believes the partnership has resulted in a working metrology tool that is meeting specifications for repeatability, reproducibility, and accuracy at the 32nm half-pitch node. Rice said: "The industry now has the capability to determine smaller image placement errors than could be measured before. Achieving these specifications is a major milestone toward enabling the International Technology Roadmap for Semiconductors (ITRS) mask requirements for the 32nm node and below. This accomplishment will help to advance the development of photomasks with tighter overlay requirements, demanded by memory devices and double patterning methods."
The performance targets of the tool were driven by the requirements for advanced memory and double exposure/double patterning mask pattern placement and overlay that will help extend 193nm lithography according to the ITRS.
Dr Oliver Kienzle, managing director of Carl Zeiss SMS, added: "To achieve the performance specification of the PROVE system is a major milestone in the project and crucial for our customers in the mask making industry. The system is based on a completely new developed platform enabling in-die and sub-nanometer pattern placement metrology in a most versatile way. The measurements can be done on arbitrary production features in the active area of the photomask for accurate and cost efficient metrology and is extendable to EUV technology."
According to Kienzle, this technology represents a significant improvement over previous capability due primarily to the incorporation of high resolution 193nm wavelength imaging optics, a flexible illuminator that maximises image contrast, an in-die registration analysis algorithm and a metrology platform. The system can be extended to measure EUV photomasks and Kienzle believes the tool will play a vital role in enabling next generation mask-making technology.
