Improved Deep And Mid-UV Photolithography With Novel Wafer Warpage Control
Original Publication Date: 1988-May-01
Included in the Prior Art Database: 2005-Feb-15
Current optical projection printing tools operating in the mid ultraviolet (300 to 350 nanometers) and deep ultraviolet (220 to 300 nanometers) display increasingly shallow depth of focus due to the decreasing wavelength of exposing light. This shallow depth of focus problem is compounded by the increased wafer warpage caused by sequential hot processes and depositions on the wafer. The lithographic effect of this warpage is the decreased photoimage control across the wafer. Mechanical wafer chucking does not completely alleviate the warpage problem.