Study on Fabrication Process Parameter Estimation by Visual Measurement

The cross-sectional dimensions of the photoresist in the photolithography process are estimated from top-down scanning electron micrographs for improved control of photolithography conditions. As semiconductor design rules shrink, strict process control is becoming increasingly important. Two primary process parameters in the photolithography process, exposure dose and focus position, require strict control in order to achieve the desired photoresist profile. The relationship between the photoresist profile and changes in these two parameters of photolithography is determined by simulation, and features suitable for estimation of the photoresist profile are identified in conventional images obtained for critical dimension monitoring. Experimental results demonstrate that process parameters can be estimated to within error of 1.0 mJ/cm2 for exposure dose and 80 nm for focus position, making the proposed method suitable for photolithography process control.