Light Absorbing Layer for Optical Projection Lithography
Original Publication Date: 1981-Oct-01
Included in the Prior Art Database: 2005-Feb-12
A light-absorbing layer of a baked polymer, such as a novolak resin, positioned on top of a silicon or garnet substrate and beneath a layer of aluminum reduces the standing wave produced by surface reflectance in optical projection lithography. The polymer material is dissolved in a solvent with a CELLOSOLVE* acetate to form a solution containing typically 10% solid content. A film of this solution is deposited on the substrate surface by a spinning process. The film is then baked at an elevated temperature, for example, 300 degrees C, for 30 minutes to increase its light absorbency. The light transmittance of this film is determined by the film thickness and the baking temperature; i.e., the transmittancy is lower for thicker films and for higher baking temperatures. * Trademark of Union Carbide Corporation.