A Bi-Level Resist System with a Conductive Bottom Layer for EB Lithography

We describe a new electron beam (EB) direct wafer writing process using a bi-level resist system of three-dimensional polysilphenylenesiloxane (TSPS) over a conductive bottom layer. The top-layer TSPS chemically amplified negative resist, developed with alkali, is highly sensitive and has high contrast. The conductive bottom layer comprises tetracyanoquinodimethane (TCNQ) complex salt, binder resin, crosslinker, and photoacid generator; it has excellent conductivity and stability with the developer used for the TSPS. We achieved high resolution with a high aspect ratio and significantly reduced pattern distortion caused by EB charging.