(614d) Enhanced Photopatterning of Polymer Dielectrics Via Imprint Lithography

A challenging application space exists for photosensitive, thick-film, high aspect ratio polymers in microelectronics. Development of a process to fabricate high aspect ratio polymer molds for copper electroplating interconnects could enable improved IC electrical performance and reliability. However, high aspect ratio photo-processing of thick polymers is difficult with traditional photolithography techniques. Thick films suffer from light scattering, resulting in poor resolution compared to thin films. Furthermore, high aspect ratio hollow pillars are challenging to fabricate with photolithography because the transport of the developer in the core is slow in comparison with the transport of developer around the perimeter of the feature. As a result, hollow core pillars require longer development times than solid pillars of comparable aspect ratios, and at high aspect ratios delamination of the structure occurs before the core can be fully developed. A photo-imprint lithography process has been developed to improve the photo-patterning of polymer dielectrics for high aspect ratio hollow structures. In the photo-imprint process, a transparent stamp with surface relief structures is brought into contact with a photosensitive material. Temperature and pressure are applied to cause the photosensitive material to fill the mold, and ultra-violet light is then emitted to pattern the polymer. To develop high aspect ratio hollow pillars, a shallow photo-imprint stamp has been developed to physically move material in the polymer core. Since the imprint stamp displaces material in the area of the feature, the effective film thickness is reduced compared to the bulk film. The reduction in film height reduced the effects of scattering in the core and also facilitated transport of developer within the core. The photo-imprint lithography process fabricated high aspect ratio hollow core pillars that exceeded optical resolution capabilities.