Planarization and trench filling on severe surface topography with thick photoresist for MEMS

Jun-Bo Yoon; Gilbert Y. Oh; Chul-Hi Han; Euisik Yoon; Choong-Ki Kim

doi:10.1117/12.324314

31 August 1998 Planarization and trench filling on severe surface topography with thick photoresist for MEMS

Jun-Bo Yoon, Gilbert Y. Oh, Chul-Hi Han, Euisik Yoon, Choong-Ki Kim

Proceedings Volume 3511, Micromachining and Microfabrication Process Technology IV; (1998) https://doi.org/10.1117/12.324314
Event: Micromachining and Microfabrication, 1998, Santa Clara, CA, United States

Abstract

We have examined a simple and low-cost method to achieve planarization and trench filling on a severe surface topography for MEMS. The method simply uses a single-layer coating of a thick photoresist or polyimide, where the coating thickness is much greater than the severe surface topography. From extensive experiments, we extracted simple empirical formulae for the planarization factor (beta) of the thick photoresist AZ4562 and polyimide PI2611, which let us know the minimum film thickness required to obtain a certain (beta) on a given surface step height and pattern density. We could compare the planarization capability of AZ4562 and PI2611 by this method. Moreover, after the planarization with a thick photoresist, we have shown a new way, other than the plasma etching, to remove the upper photoresist layer conformally. Therefore, we could remain the photoresist only in trenches and fill up very deep and wide trenches with the photoresist. Also, we have shown the etch-back result of PI2611 using conventional O₂ plasma RIE. Using these methods, we obtained the (beta) of 98% on the surface of 20 micrometer-deep and 200 micrometer-wide lines and spaces with a single-coated 70 micrometer-thick photoresist. And 10-micrometer-deep and 200 micrometer-wide trenches as well as 2 micrometer-deep and 50 micrometer-wide trenches were neatly filled up with the photoresist. As applications for MEMS, we fabricated microchannels by metal coating after the trench fill-up process, and even multilevel microchannels by controlling the height of the photoresist remaining in the trench and repeating the trench fill-up process.

Citation Download Citation

Jun-Bo Yoon, Gilbert Y. Oh, Chul-Hi Han, Euisik Yoon, and Choong-Ki Kim "Planarization and trench filling on severe surface topography with thick photoresist for MEMS", Proc. SPIE 3511, Micromachining and Microfabrication Process Technology IV, (31 August 1998); https://doi.org/10.1117/12.324314

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