No abstract

The EUVL industry has unique material requirements, which are being addressed. Implementation of metrology methods new to ULE  Glass will be discussed along with material characteristics altered to meet the needs of EUVL. Metrology methods include multiple means of evaluating the striae, CTE and inclusions. Material characteristics have been altered to better meet the demands of the industry. The reduction in inclusion levels along with other improvements such as in the area of striae will be discussed here. Improvements of greater than 4x were achieved in these preliminary striae reduction trials.

No abstract

Ultra-Low Expansion ULE â Glass is the material of choice for substrates for masks and projection optics mirrors in EUV lithography. A key parameter is the temperature of zero crossover (T zc ), which is the temperature at which the coefficient of thermal expansion (expansivity, a(T)) is equal to zero. As the temperature of the glass departs from T zc , the absolute value of a(T) increases proportionally to the slope of the expansivity curve. As EUVL matures, substrates will experience wider temperature changes, while higher resolution demands tighter constrains in substrate deformation. We present data showing that through modification of the fictive temperature of the glass, T f , the expansivity slope can be lowered. This is combined with better control of T zc , which can be tuned to a narrower range to better match the requirements of each substrate. Depending on the application, performance improvements can exceed 30% with respect to traditional ULE â Glass.