High aspect ratio lithography for litho-defined wire bonding

To overcome some challenges and reliability issues of wire bonding, a study of a new interconnect technique is done. High aspect ratio interconnect called “litho defined wire bonding” can be a promising method to resolve these problems in many of the applications. Using contact aligner and resist multilayer spray-coating over high steps up to 150 μm, we are able to achieve AL interconnect lines with different parameters. Further, using multi step imaging on a ASM PAS 5500/80 projection aligner a resolution down to 2 μm on the bottom of a 150 μm deep cavity was attained. With simulation based on aerial image calculation, different multi step imaging schemes are studied to get higher resolution over topographies.