Repair of phase-shifting mask defects using a novel planarization technique with conventional blanks

Abstract

A new phase defect repair technique of phase-shifting masks made using conventional chrome-on-quartz blanks is proposed. This technique is based 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 opening on top of the defective area of the mask in a photoresist layer covering the planarization layer using UV exposure. Phase defects can, therefore, be etched away independent of their three-dimensional profile. An additional advantage of this technique is that the lithography for defect repair and therefore the repair itself is automatically self-aligned to the chrome edge. The feasibility of this process defect repair has been demonstrated using a test mask with programmed phase defects. Wafer printability results show that the defects were effectively removed. This technique has been used to successfully fabricate a phase-shifting mask contact level for a 4 Mbit DRAM product.