An evaluation of X-ray lithography using a 0.175 μm (0.245 μm/sup 2/ cell area) 1 Gb DRAM technology

Conventional optical lithography is recognized to be approaching its limit for critical dimensions in the range of 0.1 /spl mu/m. There is considerable interest in candidates for imaging below this dimension. While several technologies (X-ray, EUV, e-beam, etc.) offer the resolution to print sub-0.1 /spl mu/m features, it is not clear if any of them will be production worthy in time to maintain traditional development cycles. In this paper we assess the maturity of X-ray proximity printing using a 1 Gb DRAM technology routinely practised with 248 nm DUV lithography for all critical levels. For this exercise several experimental lots were run with four critical levels printed with X-ray lithography. This paper reports the results from these lots and compares them to the baseline optical process in terms of electrical results and identifies logistical issues unique to X-ray lithography.