Ion implantation as insoluble treatment for resist-stacking process

With regard to the resist-stacking process, it was proposed that the implantation of ions whose acceleration voltage was below 50 kV could make the lower-layer resist insoluble for the upper-layer resist-patterning process. However, the lower-layer resist pattern is observed to be removed after the upper-layer resist patterning in a pattern. In another type of a pattern, there are caves in the bottom of the lower-layer resist pattern after the upper-layer resist patterning. From the calculation of the projected range of the ions, it is found that the ions cannot reach the bottom of the lower-layer resist pattern, and therefore the bottom of the lower-layer resist is not hardened. The removal is due to the dissolution of the bottom in the lower-layer resist during the development of the upper-layer resist pattern. When the acceleration voltage of the implanted ions is set so that the projected range of the ions is larger than the resist thickness, the lower-layer resist can be made effectively insoluble for the upper-layer resist-patterning process. The ion-implanted pattern can be used as the etching mask. Moreover, the ions can be prevented from penetrating the film to be etched by adjusting the thicknesses of stacked antireflective coating. (C) 2010 Society of Photo-Optical Instrumentation Engineers. [DOI: 10.1117/1.3302123]