Electron-beam assisted resist sidewall angle control and its applications

Conventional lift-off process uses dual-layer resists for transferring image into the substrate (top layer) and releasing the deposit (bottom layer). However, as the critical dimension of top layer approaches sub-100 nm, the undercut of bottom layer for subsequent lift-off process becomes very difficult to control. An alternative approach is to use single-layer resist to do lift-off. Such a process requires resist patterns with a negative-slope sidewall angle, which is not easily achieved by the optical lithographic tools. In this communication, we presented a lift-off method using a tilted electron beam and further development to produce sub-100 nm features with a negative-slope sidewall angle. This process was demonstrated in a negative-tone chemically amplified resist (NEB22A2) by using an exposure electron-beam system (Hitachi-900D). The computations, based on Monte Carlo simulations, were found to be in good agreement with the experimental results. Two extensive applications for recording heads were also presented.