C. Pierrat et al., REPAIR OF PHASE-SHIFTING MASK DEFECTS USING A NOVEL PLANARIZATION TECHNIQUE WITH CONVENTIONAL BLANKS, Journal of vacuum science & technology. B, Microelectronics and nanometer structures processing, measurement and phenomena, 12(5), 1994, pp. 3057-3059
A new phase defect repair technique of phase-shifting masks made using
conventional chrome-on-quartz blanks is proposed. This technique is b
ased on the planarization of defects and dry etching of the defective
area under conditions where the planarization layer etch rate is made
equal to the quartz etch rate. The process consists of defining an ope
ning on top of the defective area of the mask in a photoresist layer c
overing the planarization layer using UV exposure. Phase defects can,
therefore, be etched away independent of their three-dimensional profi
le. An additional advantage of this technique is that the lithography
for defect repair and therefore the repair itself is automatically sel
f-aligned to the chrome edge. The feasibility of this process defect r
epair has been demonstrated using a test mask with programmed phase de
fects. Wafer printability results show that the defects were effective
ly removed. This technique has been used to successfully fabricate a p
hase-shifting mask contact level for a 4 Mbit DRAM product.