Bilevel resists process schemes

All future alternatives will require new resists and processes, and for the first time, manufacturing lines will be using at least two different resists. These new materials must have satisfactory sensitivity, resolution, and process latitude. In addition, the deep-UV tools will have limited depth of focus (1-2 (xm) and will be useful only with relatively planar surfaces. Multilayer-resist schemes have been proposed to overcome these limitations, and the simplest is the bilevel scheme that requires a resist that can be converted, after development, to a mask resistant to O2 reactive ion etching (RIE). Resistance to O2 RIE can be achieved by incorporating an element into the resist structure that easily forms a refractory oxide. Silicon performs this function very well and is relatively easy to include in a wide variety of polymer structures. 

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