Photolithography resist process consists of priming, resist coating, post-apply bake, exposure, post-exposure bake
develop, and post bake; advanced RETs and immersion photolithography has more critical resist process steps.
Materials used in the resist process require the utmost in cleanliness, especially coating & develop process. In
photolithography, De-Ionized Water (DIW) or Ultra Pure Water (UPW) is used during resist developing process as the
pre-wet and rinsing material. UPW is supplied by a centralized auto supply system in a semiconductor fabrication; the
UPW is controlled for temperature, pH, resistivity, TOC, ions, and etc.
State of the art semiconductor design continues to shrink; defect control becomes essential for high yields in
semiconductor fabrication. In this paper, effect of UPW quality on resist process defect is revealed. Low resistivity
DIW used in resist developing process generates residue defects, which created killing block etch defect after the
subsequent etching process. Different measurements for DIW quality are demonstrated; water pH, conductivity, and
Total Organic Carbon (TOC) in this case reflected the quality issue of UPW. Detail study on the residue defect and the
cause-and-effect with UPW's quality is shown and discussed; the hypothesis is explained with experimental results.
High quality UPW is required to eliminate the residue defect, hence minimal defective wafer is obtained. Additionally,
resist developing process optimization to improve process robustness is also important.