The Risk of Pattern Collapse for Structures in Future Logic Devices

Abstract

Pattern collapse has long been known in photoresist patterning where the resist patterns merge or collapse during rinsing and drying steps [. The forces responsible for this collapse were identified as capillary forces during the drying process. Structures such as titanium nitride DRAM cylinders [ and silicon Flash shallow trench isolation (STI) lines have also been observed to be pattern collapse sensitive due to increase in aspect ratio of the features. Micro-electromechanical systems (MEMS) devices also show a similar phenomenon, but on a larger length scale, and is referred to as stiction [. For the technology nodes <14 nm, back-end-of-line (BEOL) low-k structures are also on the verge to show pattern collapse behavior. Whether a structure is sensitive to pattern collapse or not depends on several parameters, which will be analyzed in this paper.