Feb 14 2013
Toshiba Corporation and NuFlare Technology, Inc. have been awarded The 59th Okochi Memorial Grand Production Prize for their joint development and practical application of electron beam (EB) mask writers. The award ceremony will take place in Tokyo on March 22.
LSI circuits are fabricated by using lithography tools to project and shrink master circuit patterns onto wafers. The master circuit patterns are first written on masks by EB mask writers. Previously, most EB mask writers used point beams to write the patterns, and these had to become smaller with the scaling of LSIs. This increased the write time for masks and became the key challenge in improving productivity in mask making.
Toshiba and NFT together developed a practical EB mask writer with better writing accuracy and productivity that utilizes Variable Shaped Beam (VSB) mask writing method, where electron beams are formed into desired shapes to fill in the patterns.
The Companies developed a novel formula and calculation system that achieves faster and more accurate correction of proximity effect, the phenomenon whereby scattered electrons from the mask substrate change the beam exposure degrade the accuracy of mask patterning. The previous technology required a few days of calculations to achieve the target calculation error of less than 0.5%. The new formula cuts the calculation time to under 1 hour, allowing real time calculations to be coordinated with pattern writing (beam scanning and tool stage movements).
The development and application of a high brightness electron source shortens the mask write time. This was achieved by improving the material of the electron source and its operating conditions to boost brightness – the amount of electrons emitted in a certain time. This eventually reduced the time needed for exposing the electron beams on to the mask by 95%, significantly reducing the write time.
The Companies will continue to promote innovative technology to meet increasing demand for mask writers with better accuracy and productivity.