Digital holographic microscopy of buried specimen using a common-path reflective setup

Semi-destructive imaging methods for integrated circuits, system on a chip devices and microcontrollers are necessary to detect hardware Trojans, for reverse engineering and security related investigation of integrated cryptographic devices. We demonstrate a digital holography microscope setup in common-path reflective geometry. A near infrared low-coherent light source is used to examine, the still operational, semiconductor devices from the backside through the thinned Si-substrate without destroying the sample. The hologram is captured with a cooled sCMOS camera and characterized using the angular spectrum method. A numerical lens, created by Zernike modes, is applied to correct the phase distortions. After that the hologram is unwrapped using a quality guided algorithm. Buried structures generate additional inference patterns based on the reflections of different interfaces inside the media. We present different approaches to the challenging process of separating the wanted hologram from the unwanted phase disturbances. The resulting images provide information about the change of the refractive index in the media, as well as the topography of the buried structure.