Overlay and Alignment Control on Non-Developed Wafers by the Interferential Contrast Technique
Original Publication Date: 1989-Mar-01
Included in the Prior Art Database: 2005-Jan-27
The problem to be solved is overlay and alignment reading, just after exposure, but without any development of the photoresist. The novel disclosure is that of an application of the optical differential interference contrast technique in semiconductor manufacturing. Interferential contrast allows reading on any layer without photoresist development. The image is very clear and precise and thus allows very fine reading, as good as that provided by a developed wafer. Optical differential interference contrast allows easy microscope inspection for defect detection and film homogeneity. Details so small or refractive index variations that are not visible with any other optical inspection technique appear clearly with a three-dimensional effect.