Direct spray coating of photoresist for MEMS applications

Direct spray coating, a new photoresist deposition technique, is investigated to evaluate its potential for pattern transfer on wafers with very large topography. An Electronic Vision EV101 spray coating system is employed and AZ4823 photoresist is selected to form a thick layer of resist on flat wafers and to produce sufficient coverage on wafers with deep cavities. The dependence of the resist thickness on the dispensed volume of the resist is studied. A few key parameters are optimized to achieve a uniform resist layer. Special attention is paid to the layer characteristics when sprayed on wafers with cavities of various depths. A few applications of spray coating are shown to further illustrate its possibilities in MEMS.