MEMS fabrication process base on SU-8 masking layers
AssigneeThe United States of America as represented by the Secretary of the Air Force
InventorsScott A Ostrow, II, Ronald A Coutu, Jr.
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Abstract
A novel fabrication process uses a combination of negative and positive photoresists with positive tone photomasks, resulting in masking layers suitable for bulk micromachining high-aspect ratio microelectromechanical systems (MEMS) devices. This technique allows the use of positive photomasks with negative resists, opening the door to an ability to create complementary mechanical structures without the fabrication delays and costs associated with having to obtain a negative photomask. In addition, whereas an SU-8 mask would normally be left in place after processing, a technique utilizing a positive photoresist as a release layer has been developed so that the SU-8 masking material can be removed post-etching.
Claims18
A process for fabricating features into a wafer using a combination of negative and positive photoresists for use with positive photomasks, resulting in masking layers suitable for bulk micromachining in the fabrication of microelectromechanical systems (MEMS);
- comprising the steps of:
- (a) spinning a negative photoresist onto the wafer;
- (b) spinning a positive photoresist buffer layer onto the negative photoresist;
- (c) depositing a barrier layer onto the positive photoresist buffer layer;
- (d) spinning on an image reversal photoresist layer onto the barrier layer;
- (e) exposing the image reversal photoresist layer with a positive mask;
- (f) performing a post exposure bake;
- (g) flood exposing the image reversal photoresist layer;
- (h) developing away unexposed areas of the image reversal photoresist, creating windows in the image reversal photoresist to the barrier layer;
- (i) etching away the barrier layer through the windows;
- (j) flood exposing the positive photoresist buffer layer and the negative photoresist;
- (k) post exposure baking the negative photoresist;
- (l) removing remaining image reversal photoresist, barrier layer, and positive photoresist;
- (m) developing away unexposed areas of the negative photoresist to form features in the negative photoresist;
- and,
- (n) etching the features into the substrate.
Dependencies are inferred from the claim text.