Simultaneous Removal of Particles from Front and Back Sides by a Single Wafer Backside Megasonic System

Abstract

In IC manufacturing, particle removal from a wafer's back side (BS) has become as important as that from the front side (FS). For example, during lithography, BS particles can cause a variation on the topside surface topography. This may result in a focus-spot failure due to the reduced process window for depth of focus (DOF) as shown in Fig. 1. This problem increases as the feature size decreases. BS particles may cause other problems in wet benches, where BS particles can be transferred to the adjacent front side of wafers. Fig. 2 shows these FS particles, which usually appear as flow or streak patterns on the wafer [.