ANALYSIS OF WAFER BONDING BY INFRARED TRANSMISSION

In solid state technology, two silicon wafers can be combined by wafer bonding, Small particles between the two surfaces may cause voids. Fo r quality control: the voids can be detected by transmission of infrar ed light: provided by a Nd:YAG laser at a wavelength of 1.064 mu m, wh ere silicon is transparent. The defects are made visible via a CCD-cam era on the monitor of a computer and appear as interference rings. Thi s paper describes a method to enhance the visibility of the defect rel ative to other superimposed patterns e.g. from metallization. The void s are deformed elastically by applicating an external air pressure ins ide an inspection chamber. Insufficient bonded wafers; caused by parti cles as small as 1/2 mu m, can be detected by routine in order to enha nce the yield.