Use of optical metrology for wafer level packaging of CMOS image sensor

For WLP and 3D integration, wafers are processed through several steps which generally include bounding and thinning processes. Those processes are generally realized by the use of carriers typically glass or Silicon substrates. In this paper, we present results about thickness measurements using optical techniques namely Infra-Red interferometer and white-light spectrometer on various stacked structures. These non contact optical techniques are demonstrated to be helpful methods for the in-line monitoring.