Study of Stiction Mitigation in Micromachine Structures via Naphthalene Sublimation

Abstract

Micromachined devices are susceptible to stiction failure, where suspended structures irreversibly adhere due to surface forces. This paper investigates the effectiveness and reproducibility of simple, low-cost sublimation methods to reduce stiction using a saturated naphthalene-isopropyl alcohol (IPA) solution or molten naphthalene. Six categories of test structures were fabricated on silicon-on-insulator wafers, including narrow and wide cantilevers, clamped-clamped beams, parallel clamped-clamped beams, meandering beams, and suspended proof masses. We evaluated the effectiveness of air drying, IPA rinse, supercritical point drying (CPD), naphthalene-IPA solution, and molten naphthalene by identifying the longest and least stiff intact structure released for each method. Results showed that molten naphthalene outperformed CPD for wider structures, and reproducibility was confirmed over 10 repetitions per structure and method. These cost-effective, room-temperature techniques are well-suited for mitigating stiction in larger and softer structures, enhancing accessibility and availability for MEMS fabrication. [2024-0170]