For high absolute pattern placement accuracy and high throughput in x- ray mask writing, it is very important to firmly hold the mask with little holding deformation and large thermal conduction. For these purposes we have developed a new 'triple-chuck' mask holding mechanism. This triple-chuck mechanism is a hybrid of three-point-contact and conventional electrostatic-chuck holding mechanism, and, as the name implies, it uses three small-area electrostatic chucks. To determine the suitable shape, area, and position of the electrostatic chucks, we performed deformation simulation using the finite element method, and also conducted thermal conduction simulations. The results suggested that the triple-chuck mechanism could attain targets set for an x-ray mask with a feature size of 0.2 micrometers . Accordingly, we installed the new holding mechanism in the EB-X1 writer and found that when holding 3-inch mask (2-mm thick, before bulk etching), there is no microslippage between the mask and holding mechanism when the XY-stage is moved with an acceleration of 0.3 G and the maximum holding deformation is 0.22 micrometers in a 25-mm-square patterning area. This corresponds to the absolute pattern placement accuracy degradation of less than 11 nm in the patterning area. About 30 minutes pass before the mask temperature is within 0.1 degree of the holding-mechanism temperature. This was determined by two different methods: a patterning method and marek detection. These experimental results confirmed the triple-chuck holding mechanism attained the targets set for an x-ray mask with a feature size of 0.2 micrometers .

Date Published: 3 July 1995
PDF: 12 pages
Proc. SPIE 2512, Photomask and X-Ray Mask Technology II, (3 July 1995); doi: 10.1117/12.212770

Published in SPIE Proceedings Vol. 2512:
Photomask and X-Ray Mask Technology II
Hideo Yoshihara, Editor(s)