| Popis: |
There is a limit to the minimum feature size that can be printed using current lithographic techniques. For that reason, engineers often employ various shrink methods in production to reduce the size of features generated by lithography. One such technique is the application of a shrink assisted film for enhanced resolution (SAFIER). In such a process, a SAFIER chemical is coated onto a patterned photoresist and baked. During the bake, the resist expands, and hence, the patterned spaces in the resist shrink. The shrink process, however, does not necessarily occur uniformly across the wafer, and some critical dimension (CD) non-uniformity can be introduced during this step. This study investigates the efficacy of using an intentionally biased SAFIER bake temperature profile to compensate for some of the CD nonuniformities introduced during the SAFIER process. In the baseline case, patterned wafers underwent a standard SAFIER process using a thermally uniform bake. The bake temperature of the SAFIER bake was then biased to cancel out some of the shrink induced CD non-uniformity. Wafers processed through the biased temperature SAFIER bake showed a 20% improvement in post-SAFIER (critical dimension uniformity) CDU. For comparison, a biased post exposure bake (PEB) temperature was used to create wafers with a non-uniform starting CD distribution designed to cancel out some of the CD non-uniformity from the SAFIER process. When these wafers were processed through a uniform temperature SAFIER process, a 54% improvement in post SAFIER CDU was observed over the baseline case. |
