The basic principle and the overall scheme of a new technique for nanostructure fabarication are described, and experimental results are given. A thermal atomic beam effusing out of an oven is firstly collimated by a small aperture and then collimated to a high degree by a polarization gradient laser field. This well-collimated atomic beam is patterned by a mechanical mask, and nanostructures are generated by atomic deposition. SEM profiles of nanostructures have shown that the feature size of the structure can reach nanometer scale. Compared to other micro-lithographic techniques, this technique has many advantages such as low cost, high throughput, mass production, simple process etc.
The two-level atom focusing in a Gaussian standing wave laser field was analyzed from the perspective of both classical mechanics and wave mechanics. The effects of source imperfection such as velocity spread and beam spread on atom focusing were analyzed by numerically integrating the classical equation of atomic motion. The ideal focal plane can be easily determined by the variation of atomic density at the minimal potential of the standing wave laser field as a function of traveling distance. In the absence of source imperfection, the contribution of diffractive aberration originating from the wave nature of the atom to broadening of feature width is larger than that of spherical aberration. Several methods for improving atom lithography experiments were presented.
The influence of polarization on the image performance of optical lithography systems has been systematically investigated through comparing the image contrast and the process window with TE-polarization, TM-polarization and un-polarized light, respectively. The simulation results show that the TE-polarization imaging is possible to improve the image performance of optical lithography systems, especially for those systems with high numerical aperture. The effects of polarized-light imaging with a conventional masks and a polarized film mask were studied by carrying out series of experiments under the conditions: 436nm exposure wavelength, numerical aperture of 0.5 and partial-coherence factor of 0.2. It is found that the image quality of the L&S patterns with the polarized film mask is better than that of with the conventional mask and, 0.3 μm L&S patterns are obtained with the polarized film mask.