Study of Process Window Discovery Methodology for 28nm and Beyond Technology Node Process Window Limiting Structures

Process window limiting structures (PWLS) evaluated with process window discovery methodology (PWD) was studied on 28nm and beyond technology node wafers. Process window discovery methodology was innovated basing on process window qualification (PWQ) methodology. And the impacted factors, including focus energy matrix (FEM) wafer conditions, defects inspection conditions and defects filtering and sampling methods, were also investigated. With the innovated methodology, process window limiting structures were detected on 28nm wafers. Then the more reasonable process window target and spec, including lithography and etch process, were redefined. Furthermore, the process window limiting structures were enhanced monitored with Nano-point function of bright-field inspection system. Instead of end of line (EoL) chip probe (CP) test, inline process window discovery methodology has much time advantage for process window evaluation and process window limiting structures definition even monitoring.