Monitoring of yield-critical STI oxide voids and residues in HAR structures

Shrinking deep trench DRAM geometries below the 100 nm design rule involves new design concepts in the frontend-of-line, which necessitate new monitoring strategies, such as high aspect ratio (HAR) inspection and reliable detection of stringers and voids. Additionally, known defects such as particles and voids become increasingly critical, as their sizes reach the typical design rule dimension. Infineon Technologies Dresden successfully developed monitoring strategies for residue in HAR structures and STI oxide voids based on a novel high-resolution darkfield inspection concept. These monitoring strategies are closely aligned to the exact process steps and, thus, enable faster response to potential excursions and a shorter learning cycle.