Novel alignment method for planarized substrates in electron beam lithography

Improvement of an alignment accuracy is one of the key issues for achieving large scale integration. Recently, wafer planarization technique has been introduced to realize multilevel metalization with high reliability. However, it causes difficulty in obtaining high alignment accuracy because the alignment mark depth becomes small. In this paper, we propose a new alignment mark structure for planarized substrates to obtain high alignment accuracy in electron beam lithography. For multilevel metalization processes, advantages of buried heavy metal mark were confirmed by detection signal simulation and exposure experiments. Light elements such as Si in SiO/sub 2/ layer or SiO/sub 2/ mark in Si substrate, especially periodic deep line marks that are suitable for wafer planarization processes, are also found to be novel alignment mark structure.