Zero lag dispense to increase the etching uniformity in a single wafer wet cleaner

Abstract

With the increase of the wafer size, it becomes more and more challenging to control the etching rate and etching non-uniformity precisely in the wet process of semiconductor manufacturing. In this paper, the effects of the DHF (diluted hydrofluoric acid) starting dispensing point, the dispensing time, and the wafer clean time on etching rate and non-uniformity of the silicon oxide wafer were investigated. The results indicated that the first reaction of DHF with silicon wafer surface plays an important role to the final etching rate and non-uniformity. Based on the analysis, a new method of zero lag dispense was proposed and tested to reduce the non-uniformity of etching. The method uses a special dispensing device to inject DHF on the surface instantaneously and uniformly before it is dispensed from the swinging nozzle. The non-uniformity within a wafer reduces to 1.8% under DHF process (1:220, 20°C, 60s).