Very High Aspect Ratio Deep Trench Structures for Sub-0.135μm DRAMs

摘要

With DRAM devices continuing to scale downward to feature critical dimensions smaller than 0.15 μm, it is becoming exceedingly difficult to etch trenches to larger depths as needed for cell capacitance requirements. This difficulty is due to the inherent aspect ratio dependent etch (ARDE) behavior that only gets worse at high aspect ratios, which are exceeding 40:1. In this paper, we report for the first time etching of 60:1 aspect ratio trenches in c-Si with an opening dimension of 90 nm. A comparison is also made of the ARDE behavior with 110 and 135 nm trench openings.