An approach to quarter-micron e-beam lithography using optimized double layer resist process

An approach to quarter-micron e-beam lighography was directed by computer simulation and evaluated experimentally. A combination of multilayer resist and ordinary acceleration voltage, 20 kV, was adopted. The double layer structure was selected as the simplest multilayer structure. In order to transfer the resist pattern to the underlying polymer, it is necessary to develop an e-beam resist, which can extremely withstand in O2plasma. Metal addition to resists results in (1) dry etch resistance enhancement, and (2) resolution deterioration by electron scattering increase. However, the resolution deterioration should be more than compensated for by resist thickness reduction, due to the benifit of dry etch resistance enhancement. Trade-off between resolution deterioration and dry-etch resistance enhancement by metal-addition to resists was evaluated by Monte Carlo simulation. Si is foreseen as one of the most attractive metals to add. Commercially available Si-containing e-beam resist, silicone, has been utilized for double layer resist process and quarter-micron resolution has been obtained. Tapered step marks have been developed, avoiding excessive coverage by multilayer resist and to maximize registration signals. Detection accuracy of 0.1 um has been obtained.