100-nm defect detection using an existing image acquistion system

摘要

For obvious cost reasons, semiconductor manufacturers are constantly striving to produce ever smaller wafer geometries with the current installed base of wafer steppers. Many techniques have been used successfully to 'squeeze' more resolution from these steppers than was once thought possible. Wafers processed using non-aggressive k$-1$/ factors provided a linear correlation between mask and wafer feature sizes. However, it has been shown that pushing k$- 1$/ factors to very low levels causes a nonlinear response between changes in photomask and wafer critical dimension. This non-linearity demands extremely tight photomask CD control specifications. Total CD errors 50nm and smaller can cause unacceptable wafer CD variation. In this paper, defect sensitivity and false detection performance of a new advanced line measurement algorithm was tested. The test vehicles included both an industry standard and a custom designed programmed defect test mask. In addition, production masks with naturally occurring localized CD errors that caused wafer pattern bridging were analyzed. This new experimental algorithm has shown localized CD error detection of $LSEQ 100 nm reticle defects.