Embedded metal mask enhanced evanescent near field optical lithography

Simulation of evanescent optical lithography using an embedded metal mask (EMM) shows that resolution and throughput are significantly enhanced over conventional ENFOL, due to coupling between surface plasmons and cavity mode excitations. The key role played by surface plasmon polaritons and the effects of wave vector matching between the incoming photon and the EMM mask grating are clear from the simulation. In particular a double peaked resonant intensity distribution is revealed for the first time within the dielectric filled mask cavity, for the shorter wavelengths only. This effect is highly conducive to efficient sub wavelength lithography and has not been discovered by previous simulations. The EMM–ENFOL process has considerable potential for cheap, high throughput nanolithography with resolution well below diffraction limits.