Low cost application of oxide test wafer for defect monitor in photolithography process

Abstract

A low cost technique for detecting defects in photolithography processes in a submicron integrated circuit manufacturing environment combines use of a reusable test wafer with in-line processing to monitor defects using a pattern comparator system. A reusable test wafer having an oxide layer overlying a silicon substrate and having a thickness corresponding to a minimum reflectance for an exposure wavelength used for photolithography is patterned using a prescribed photolithographic fabrication process to form a repetitive pattern according to a prescribed design product rule. The pattern is formed using a reticle having a repetitive pattern array with a similar design rule as the product to be developed by the lithography processes. The patterned test wafer is then inspected using image-based inspection techniques, where the image has high resolution pixels of preferably 0.25 microns per pixel. An optical review station and scanning electron microscope system are used to review defect and classify defect types. The test wafer can then be reused by cleaning the photolithographic pattern by removing the photoresist, and then removing polymer particles adhering to the oxide layer following removal of the photoresist.