Hiro-o Nakagawa

Primary evaluation of proximity and resist heating effects observed in high-acceleration voltage e-beam writing for 180-nm-and-beyond rule reticle fabrication

Higher resolution and accuracy are required in e-beam lithography for reticle fabrication for coping with further advances in optical lithography. The trend is to use high acceleration voltage (50 kV) e-beam to improve spatial resolution. However, in the case of high acceleration e-beam writing, a drastic critical dimension (CD) change is caused by a strong proximity effect and a large resist heating effect. The proximity effect is caused by the increase in the back- scattering radius. The back-scattering radius was estimated by two independent observations of the CD variation of a monitor and the thickness variation of a partially developed resist. It is found to be ca. 15 nm. Using the shot time modulation as a proximity correction reduced the proximity effect to a small level: CD error due to the pattern density change remained within 10 nm. On the other hand, the resist heating effect is caused by the change in resist dissolution speed by the temperature rise of the resist. In reducing this effect, multi-pass writing is found to be effective. The range of the CD error of 2 micrometer lines-and-spaces in the writing field has been reduced from 22 nm to 6 nm by changing the writing from one pass to four passes for a conventional resist. Moreover, when a chemically amplified resist (CAR) is exposed through one-pass writing, the range of the CD error is found to be 8 nm. Therefore, the use of the CAR is effective in reducing the resist heating effect. Simulation software ProBEAM/3D and TEMPTATION were used to obtain three- dimensional resist profile and the transient temperature rise of the resist, respectively. Both provided results that agreed well with those by experiment.

Development of bilayered TaSiOx-HTPSM: II

TaSiOx shifter has been developed for HT-PSM for ArF and F2 laser lithography. Adopting bilayered structure and embedding an etch-stop function into the transmittance control layer enable us to fabricate a TaSiOx-HT without quartz damage and to control the phase precisely. And less impact of TaSiOx shifter etching to CD was confirmed. It was confirmed this TaSiOx-HT was inspected by conventional inspection system without any problem.