Optical lithography: The implications of the electromagnetic field theory

Optical projection lithography and the contact printing of a half plane are treated, based on the electromagnetic diffraction theory. Integral representations are given for the time-average electric-energy density distribution of the projected edges which are illuminated by a linearly polarized monochromatic wave or by a quasi-monochromatic incoherent beam. The image space is either homogeneous or a perfectly conducting screen is inserted normal to the optical axis. Contact printing is treated in terms of rigorous electromagnetic-field theory, by which the electromagnetic-field distribution is derived in a stratified substrate, each layer of which may have an arbitrary refraction index. Numerical results for boil contact printing and projection are given for edges which are illuminated by coherent beams with the polarization either normal or along the edge. In addition, the distribution due to the projection of an incoherent edge is given. The distributions obtained through contact printing are presented in the resist layer, Which is applied directly on the aluminum substrate or on an amorphous silicon antireflection coating as the intermediate stratum. The ultimate positive and negative resist patterns are systematically compared.