High Resolution Double-Crystal X-ray Diffraction Imaging for Interfacial Defect Detection in Bonded Wafers

Abstract

Wafer bonding is used for the integration of heterogeneous semiconductor materials, without the constraints of lattice constant or crystal structure mismatch. The most important aspect of such bonding is the surface flatness and the absence of particles in the bonded interface. It is very important to identify these particles, which can further result in poor bonding. The most common method for identifying has been IR imaging, but it is limited to materials which are transparent in the operating region of the CCD camera. Also, the resolution of IR image is low. X-ray diffraction imaging (topography) has been identified as the most sensitive and high resolution imaging technique capable of resolving variations due to very small particles within both the bonded and the unbonded areas. It also allows for imaging of samples which are opaque to IR, like heavily doped wafers.