Alternative Masking Materials for Photomasking
Original Publication Date: 1984-Sep-01
Included in the Prior Art Database: 2005-Feb-04
Instead of depositing multicoated layers on the chrome surface to reduce the high reflectivity of chrome on photomasks, which degrades the modulation transfer functions at the wafer plane, this article proposes alternate metal masking materials for photomasking. Chrome carbonyl is replaced with less reflective metal carbonyls, such as iron [Fe(CO)5], molybdenum [Mo(CO)6], nickel [Ni(CO)4], tungsten [W(CO)6], or cobalt [Co2(CO)8] carbonyls, which deposit a lower reflectivity metal layer on the substrate while still being conductive enough for use with E-beam pattern definition. The deposited metal is in a very inert form while using even normally unstable metals, such as iron. The deposition method makes these metals stable enough not to oxidize under normal conditions.