Measurement of sidewall, line and line-edge roughness with scanning probe microscopy

Decreasing dimensions of features in semiconductor device manufacturing makes it imperative to control the sidewall, line and line-edge roughness. The roughness contributes to the variation in critical dimension (CD) and it might affect device functions and reliability. Roughness of vertical surfaces is needed in order to understand its effect on the performance, especially in the case of structures such as optical wave-guides. One of the ways to measure the sidewall, line and line-edge roughness is to use a scanning probe microscope. By using specific techniques in operating the scanning probe microscope and special analysis, we obtain the sidewall, line and line-edge roughness. We also use high-resolution image of the sidewall to characterize its roughness with various techniques including spatial frequency analysis. Both qualitative and quantitative evaluations are demonstrated. These measurements are made with an automated tool in a non-destructive fashion and are useful in production control.