Practical phase control technique for alternating phase shift mask fabrication

摘要

Techniques of fabricating altPSMs of single trenc structure by quartz etching have been developed. A two-step etching process was adopted to make the side-etchign structure. Shifter areas were etched by dry-method in first step and by wet-method in second step. In the experiments, by a RIE type dry-etching machine, a hydrofluoric (HF) acid etching system, a phase measurement system (MPM-248) and 6025-mask plate were used. We optimized dry-etching parameter, such as pressure, RF power and composition of gas mixture ratio. The smallest phase difference between the deviuce-pattern and the monitor-pattern was obtained in low pressure with inactive gas. The dry etching uniformity was improved and range value was reduced from 2.7 degrees to 1.1 degrees by using type B of the plate holder. In wet etching process, two modes of movement and two concentration of buffered HF acid were compared from the viewpoint of etching uniformity. The technique described in this study can be aplied to 150 nm node altPSMs fabrication and shows an extensibility to 130 nm node.