Modification of photoresist profile in lift-off process for MEMS application

Ranganathan Nagarajan; Rakesh Kumar

doi:10.1117/12.476090

13 November 2002 Modification of photoresist profile in lift-off process for MEMS application

Ranganathan Nagarajan, Rakesh Kumar

Proceedings Volume 4936, Nano- and Microtechnology: Materials, Processes, Packaging, and Systems; (2002) https://doi.org/10.1117/12.476090
Event: SPIE's International Symposium on Smart Materials, Nano-, and Micro- Smart Systems, 2002, Melbourne, Australia

Abstract

A CMOS compatible single resist layer lift-off process for forming patterns on a substrate is described. Unlike in most other methods, an ion bombardment is employed here to harden the top of the resist leaving the sidewall of the resist unaffected. The resist is then treated to a low temperature O₂ plasma etching process to achieve a T-shaped undercut profile. This process is found to be simple, repeatable and controllable. Resist profile with adjustable overhang length and the sidewalls of the resist profile with an almost T-shape could be achieved with the help of the process described in the current work. Such increased overhang length prevents metallization of the sidewalls of the resist, and thus facilitates more rapid removal of the resist during lift-off. The process starts from a patterned resist layer having vertical resist profile. It is then subjected to Ion bombardment to harden the top surface of the resist leaving the sidewalls unaffected. The ions are directed at sufficient dose and energy to cause the top of the resist mask to get hardened. Subsequently, the resist patterns are subjected to a low temperature isotropic plasma etching process resulting in an under-cut T-shaped resist profile. This process is highly suitable for MEMS application where metals like Cr, Au, Cu etc are frequently used but are difficult to dry etch.

Citation Download Citation

Ranganathan Nagarajan and Rakesh Kumar "Modification of photoresist profile in lift-off process for MEMS application", Proc. SPIE 4936, Nano- and Microtechnology: Materials, Processes, Packaging, and Systems, (13 November 2002); https://doi.org/10.1117/12.476090

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