Product Briefing Outline: Carl Zeiss SMT has announced the completion of their final design - ‘PROVE’ - for the next generation Photomask Registration and Overlay Metrology system, which was developed in collaboration with SEMATECH. PROVE will allow for the production of more advanced photomasks with substantially improved image placement accuracy, according to the company. 

Problem: Future lithographic scaling places a high reliance on very tight overlay control of the various device levels, and the photomask is a key component of the overlay error budget, especially in consideration of double patterning strategies at the 32nm node and below. Carl Zeiss SMT and SEMATECH have completed a design for quantifying image placement errors as small as 2.4nm according to the ITRS roadmap, where previously ‘no known solution’ existed.

Solution: A key component of PROVE is the diffraction-limited, high-resolution imaging optics operating at 193nm corresponding to at-wavelength metrology for the majority of current and future photomask applications. An additional benefit is the reasonable working distance, which allows through-pellicle measurements. Two illumination paths offer measurements both in transmission and reflection (e.g. for EUV), providing flexible illumination for maximum contrast imaging.

Applications: Mask pattern alignment, and registration for 32nm photomasks and beyond.

Platform: The photomask resides on an ultra-precision stage, being the only movable part in the imaging path.

Availability: Production of the tool is expected to start in 2009.