Reducing the Thickness of Resist Milling Masks
Original Publication Date: 1979-Jan-01
Included in the Prior Art Database: 2005-Feb-19
Photoresist is widely used as an ion milling mask because the substrate can be patterned immediately after lithographic exposure and development with no intermediate steps. However, there are certain disadvantages associated with a resist mask. Since the etch rate of photoresist is much greater than most substrate materials and since photoresist is subject to severe mask faceting, very thick amounts are required. However, as the resist is made thicker, it becomes difficult to control the wall shape and to resolve very fine features. Also, as photoresist experiences ion beam bombardment, it heats up and undergoes shape distortion which is transmitted into the substrate. This thermal degradation increases with thickness.