Green Masking for Microcircuit Litography

Current lithography techniques generally adopted by the semiconductor industry in the U.S. and other nations involve the use of masks which are prepared either by photolithography or by electron beam lithography. The masks consist of a glass plate on which a layer of chrome and another layer of resist are deposited. The resist is developed where it is irradiated and the chrome is etched thus leaving the pattern which is then imaged via steppers on the wafer. The preparation of masks generates undesirable chemical wastes which have to be specially disposed of to protect the environment. We propose to study the possibility of eliminating the chemical wastes by using a special glass whose opacity is directly affected by the electron beam. The glass can be used to image the pattern on the wafer and no resist or chrome is used or removed. Ideally, the glass can be restored to its original status when heated above a predetermined critical temperature. Thus, recycling of the mask becomes feasible under those conditions. Factors such as the resolving power of the glass, the amount of energy needed to change the opacity of the glass and the shelf life of the pattern written on the glass will be addressed.