Toshikazu Segawa

Performance of positive-tone chemically amplified resists for next-generation photomask fabrication

Several types of chemically amplified resists (CARs) have been evaluated in comparison with other types of resists. The evaluated CARs were found to have better performance than conventional resists and to satisfy the requirements for next generation reticle fabrication. Especially CARs have high sensitivity and high contrast enough to make photomasks with e-beam writers and have good dry-etch durability. We evaluated the allowance of baking conditions. It was found that it was important to minimize the dependence on prebake temperature as well as on post exposure bake temperature. The influence of airborne contaminants on post exposure delay (PED) stability of CARs was investigated. PED stability depends on resist materials and the ammonia concentration in the process environment. The use of a chemical filter is effective in improving PED stability. In conclusion, CARs can meet the requirements for resists used for next generation reticle fabrication.

Electron beam lithography process for advanced optical masks

The requirements for advanced optical masks have been tightened according to the accelerated lithography roadmap for semiconductor manufacturing. The accuracy of the optical mask may be affected by the pattern exposure tools, the materials, and the processes. Higher acceleration voltage e-beam pattern exposure was evaluated with a chemically amplified resist. With the higher acceleration voltage e-beam system, proximity effect correction is needed to control the critical dimension (CD). CD linearity is maintained down to 400 nm for different kinds of patterns by adopting the 50 kV e-beam system and proximity effect correction. The results show that the method is an attractive candidate for fabrication of next generation optical masks. Dry etching is effective in achieving small feature sizes, such as optical proximity correction (OPC), with high pattern fidelity. Loading effects were evaluated, and inductively coupled plasma dry etching was found to be stable against those effects. Fabrication of the OPC ...

Performance of a chemically amplified positive resist for next-generation photomask fabrication

A positive-tone, chemically amplified resist (CAR) has been evaluated in comparison with non-CARs in its applicability to fabrication of reticles to be used for 180-nm-rule devices. The evaluated CAR is found to have better performance than the non-CARs. It has high sensitivity and high contrast enough to be used with e-beam writing systems, and good dry-etch durability. Its characteristics when exposed with e-beam writing system with different acceleration voltages is studied. The CD linearity is maintain down to 400 nm for all patterns by adoption of a 50 kV e-beam system and a proximity effect correction. The resolution limit is 150 nm for lines-and-space pattern. The allowance of the baking conditions is examined and the use of a highly temperature-controllable hot-plate yields good CD uniformity. The influence of the ammonia concentration in the process environment of the post exposure delay stability is investigated. The CAR should be used under a concentration of ammonia less than ca. 5 ppb, which is obtainable by use of a chemical filter. In conclusion, it is demonstrated that the CAR meets our requirements for resist for 180-nm-rule reticle fabrication.