Patterning of 1µm Through Silicon via Critical Dimension Using Positive Tone Resist Mask with a Photolithography Stepper

Through-Silicon Via (TSV) formation is a key process in integrated circuit packaging, enabling high-density 2.5D/3D integration. This study investigated the impact of two different resist types-chemically amplified resist (CAR) and Novolac resist-on TSV patterning using an i-line stepper to improve critical dimension uniformity (CDU) across the wafer and within the field. Although the results showed minimal differences between the two resists, CAR exhibited better performance post-lithography, while Novolac performed better post-etch in terms of CDU. To understand the effect of varying incoming substrates, oxide hard mask schemes were compared to direct bare silicon to assess their influence on CDU. Additionally, the impact of TSV via pitch variation on patterning was explored, and how it could streamline development for finer pitch designs for TSV scalability, without requiring higher numerical aperture (NA) tools or advanced front-end equipment. Performance on bare Si wafers with Novolac resist was superior post-etch. However, achieving better CDU for denser pitch designs proved to be more challenging compared to baseline pitch. This comprehensive analysis of process splits provided valuable insights into lithography optimization and highlighted opportunities for pushing the boundaries of the etch process further.