Nanoimprinting over topography and multilayer three-dimensional printing

We have developed a simple imprinting technique that allows patterning over a nonflat substrate without the need for planarization. In this process, a polymer film is spin coated onto the mold and then transferred to a patterned substrate by imprinting. By selecting polymers with different mechanical properties, either suspended, structures over wide gaps or supported patterns on raised features of the substrate can be obtained with high uniformity. It. is found that imprinting at a temperature well above the glass transition temperature (T-g) of the polymer causes the thin residue film between features to dewet from the mold, which can greatly simplify the subsequent pattern transfer. process. Multilayer three-dimensional polymer structures have also been successfully fabricated using this new imprinting method. The yield and dimensional stability in the multilayer structure can both be improved when polymers with progressively lower T-g are used for different layers. Compared to existing techniques for patterning on nonflat substrates, the current method has a number of advantages, including simplicity, versatility, high resolution, and low pattern distortion. (C) 2002 American Vacuum Society.