High-resolution direct-write multiphoton photolithography in poly(methylmethacrylate) films

Multiphoton photolithography in poly(methylmethacrylate) films is demonstrated. High-resolution structures of arbitrary geometry with edge sharpnesses as small as 120 nm are produced using femtosecond pulses of 870 nm light focused to a diffraction-limited spot in the films. The power dependence of etching and tests of different polymers prove that the process is nonlinear and involves excitation of the polymer's chromophores. Atomic force microscopy images show that the vast majority of polymer is removed during etching. It is concluded that the etching mechanism involves depolymerization and thermal evaporation of the polymer. Application of this method in the fabrication of electrochemical microelectrodes is demonstrated.