Evaluation of X-ray lithography using a 0.175 μm (0.245 μm² cell area) 1 Gb DRAM technology

Abstract

Conventional optical lithography is recognized to be approaching its limit for critical dimensions in the range of 0.1 μm. 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.01 μm 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 practiced 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.