Patent ID: 6562523
Filing Date: 2003-05-13
Classification: C03C,G03F

Abstract:
A method of fabricating a surface with a three dimensional structure in a photo resist layer coated on a substrate comprising:exposing a High Energy Beam Sensitive glass (HEBS-glass) plate to an electron beam (e-beam) in a vector scan e-beam writer to provide a gray scale pattern of varying optical density in the HEBS-glass plate to form a HEBS-glass grey level mask having multiple levels of optical density, each of said multiple levels of optical density in the HEBS-glass mask being written with a clock rate corresponding to a predetermined optical density value, the clock rate being determined from the predetermined optical density value using a selected calibration curve of the HEBS glass plate which is optical density versus clock rate, said calibration curve of the HEBS glass plate having been determined for a number of variable parameters which include glass composition of the HEBS glass plate and write parameters of the e-beam writer, the write parameters being beam acceleration voltage, beam current and addressing grid size; using the HEBS-glass gray level mask having multiple levels of optical density in an optical lithography tool to expose the photo resist layer coated on the substrate, to produce a certain resist thickness after development of the photo resist layer from each optical density level in the HEBS-glass mask and to produce the surface with the three dimensional structure in the photo resist layer in response to exposure with the gray scale pattern in the HEBS-glass plate; and determining the predetermined optical density value which corresponds to a designed resist thickness of the photo resist layer having the surface with a designed three dimensional structure from the designed resist thickness using a calibration curve of an analog transfer scheme which relates resist thickness versus optical density, said calibration curve of the analog transfer scheme having been determined experimentally for a selected photo resist used in the photo resist layer.