Reduction of Local CD-Linewidth Variations in Resist Develop through Acoustic Streaming

According to the ITRS roadmap for lithography (2008 edition), the CD uniformity requirement of optical masks beyond 32nm HP is less than 1.5nm (3σ). Especially for double patterning lithography, not only the global uniformity but also the local uniformity is of very high concern. Therefore it is imperative that the develop process will yield CD-linewidth control independent of pattern sizes or pattern loading, following precisely those pattern size image correction strategies applied during mask writing (e.g. proximity and fogging correction). Conventional methods of resist develop cannot meet such requirement without negative side effects (e.g. increased dark loss, pattern collapse, global CD-uniformity degradation and/or defect issues). The ASonic ® nozzle developed by HamaTech APE combines the very favorable dark loss, defect and global CD-linewidth control benefits of a fast and uniform low impact initial develop dispense (surface wetting), with an enhanced developer agitation through acoustic streaming, which provides improved local CD-control independent of pattern size and loading. The principle functionality of the ASonic ® nozzle is described. Developing loading effect is examined with various ® nozzle, A + nozzle, photomask, resist development, CD-uniformity, photo resist, p-CAR, n-CAR