Quality and performance of late Ga+ ion FIB mask repair with the gas assist in DUV process

Abstract

Photomask quality for the next generation processing such as DUV scanner lithography is critical, but there still is many problems. In this situation, we have to find some keys to solve these problems to accommodate the narrow scope of the process margin and the printing bias control on wafer, as well as coarse lithography margins. Currently, the CD uniformity of the patterned Cr, or PSM features including the repaired mask patterns, is about In next generation photomask production, there are some fundamental difficulties to overcome as; Firstly, there is the inherent physical behavior of DUV laser on quartz substrate, and secondly, there are photomask defects that invisible to blue laser inspection, but can still be printed onto the wafer. In order to keep up with photomask product requirements, the next generation inspection systems are being developed with i-line and KrF laser sources. However, issues such as low-level transmission defects and critical line-widths defects have not been solved yet.In partially, the Ga+ implantation defect is one ofthese invisible transmission defects due to the fact that the carried inspection tools use a blue laser (488nm), so it is not be counted as a killing defect for the DUV transmitted types. Although it is captured into a false defect, we have a difficult to classify by ion implantation defect.This paper discusses the process margins of FiB Ga+ ion scanning on the opaque repairing of damaged quartz substrate. It will show the effects of reduced intensity or using the Gas Assisted Etching (GAE) process. And, though it has been solved somewhat, we also have to consider the CD control specifications for the next generation device such as 1G DRAM with DUV lithography. In this experiment, we have evaluated the printability of 4X DUV scanner after both opaque and clear defect repair with a Focused Ion Beam (FIB) system. We also confirmed the accuracy of edge repair, implantation effects of each FIB machine and determined the topography ofrepair by AFM.