Effective exposure-dose monitor technique for critical dimension control in optical lithography

Abstract

We have established effective dose metrology using a dose monitor mark named the effective dose meter, which has no focus response. By placing the effective dose meter onto the scribe line in a device reticle, in-line monitoring of the effective dose on a product has been realized. The effective dose meter is designed to monitor the effective dose as a resist line length whose dimension is detectable with an optical measurement tool. The design is considered to have no impact on both reticle fabrication and wafer processing. By monitoring with the effective dose meter, the contribution of effective dose error to critical dimension variation is obtained independently of focus error. Dose budget analysis from the in-line effective-dose monitor clarifies the current process ability on reticle linewidth variation and resist processing uniformity. This paper describes the mark design and the analysis result of the in-line effective dose monitor in device fabrication with KrF lithography.