Hiroshi Motoki

Mechanism of ArF resist-pattern shrinkage in critical-dimension scanning electron microscopy measurement

ArF resist-pattern shrinkage in critical-dimension scanning electron microscopy (CD-SEM) measurement is investigated, and its mechanism is discussed. In CD-SEM irradiation damage in the resist detected by Fourier transform infrared (FTIR) spectroscopy, we propose that C=O units of pendant polymer chains decompose COOH units at the first stage and that the COOH units finally decompose CO2 outgas at the second stage. We propose the mechanism of the ArF resist-pattern shrinkage in the CD-SEM measurement from experimental and simulation results of the FTIR spectroscopy and Monte Carlo simulation of electron scattering trajectories into the resist. The first resist polymer free volume shrinkage is caused by hydrogen bonds between the COOH units, as well as decomposition of dissolution inhibitor groups. The second resist polymer free volume shrinkage is caused by the CO2 outgas within 4–14 nm in depth from the resist surface depending on the CD-SEM acceleration voltages of 400 and 800 V, respectively, with prob...

Measurement precision of CD-SEM for 65-nm technology node

The measurement precision required for 65 nm technology node is 0.4 nm. However, ITRS has reported that the present CD-SEM has not had sufficient capability for 65 nm technology node. It is necessary to analyze the error factor of measurement precision thoroughly, in order to improve CD-SEM performance. Then, the items to be improved and the control method of tools for the measurement precision required for 65 nm technology node were examined. The error factors of CD measurement were divided into short-term repeatability, long-term variation, and tool matching. In factor analysis of short-term repeatability, the main factors of short-term repeatability were the image quality/measurement method and wafer load/unload. And it became clear that the interaction between local CD variation and scan shift accuracy had a remarkable effect on short-term repeatability. We established a method of monitoring tool condition in order to calculate long-term variation and tool matching with high accuracy. According to the experimental results of two tools for four weeks, the main factors of long-term variation and tool matching were initial variation and CD offset. From calculation of measurement precision using these results, measurement precision of the present CD-SEM has sufficient capability for hp90. It is reasonable to expect that improvement of these error factors will lead to the attainment of capability sufficient for hp65 measurement precision in the future.