Backside Infrared Imaging Using Improved Refraction-Assisted Illumination Methods

Infrared backside imaging using refraction assisted illumination (RAIL) allows for imaging microelectronic devices at high contrast and resolution through 700 microns of silicon without the need for specialized optics or coatings. However, due to the angle of illumination, not all of the metal features are equally illuminated. In this paper we present improvements on this method through image composition of a series of RAIL images taken at various illumination directions. The resultant composited image provides more uniform illumination and better approximates the features seen in scanning laser confocal microscopy.