Analysis of etched quartz solutions for 65-nm node critical layer lithography

Abstract

Manufacturability and economical viability of etched quartz solutions for 65nm node critical layer lithography is assessed through evaluation of mask technology conversion complexity, mask process complexity, wafer processing cost and SRAM cell critical layer lithography performance. The etched quartz technologies under consideration are the full-layout alternating phase shift mask solution (FullPhase altPSM) and chromeless hard shifter phase shift mask solution (crlPSM). Using 0.63 NA exposures, we achieve k 1 =0.29 (DOF=0.6µm) and k 1 =0.33 (DOF=0.8µm) for altPSM and crlPSM, respectively. 60nm isolated feature DOF is more than 0.8µm for altPSM. The crlPSM isolated feature DOF without sub resolution assist features is about 0.3µm. Simulations results of crlPSM isolated features with sub resolution assist features using NA=0.75 show that DOF of 0.3µm is attainable for crlPSM. Experimental results are used to calibrate wafer volume cross over model for these competing technologies with specific focus on die size, k 1 and DOF related yield as wafer processing cost drivers. Results show that altPSM has lower wafer processing cost due to better lithography yield at smaller die sizes. Thus, though the mask set of altPSM solution is more expensive than crlPSM, the altPSM solution is more economical for high volume production of 65nm node technologies. The wafer volume crossover model allows for the most cost effective mask solution to be employed for a given logic device and wafer volume expectation.Keywords: Alternating phase shift mask, chromeless phase shift mask, etched quartz, low k 1 , 65 nm lithography, wafer volume crossover model, cost of ownership, PSM 1. ecroffie@lsil.com; 503/618-4248

Second level exposure for phase shift mask applications using an SLM-based DUV mask writer

“…However, at the 65 nm node more aggressive PSM solutions are required that exceed the capability of i-line tools. For example, alternating PSM (Alt-PSM) masks are being used for 65 nm gate level patterning [3][4][5][6] . For this application, 2 nd level patterning is difficult with i-line laser tools.…”