21 November 2001 PZT stack etch for MEMS devices in a capacitively coupled high-density plasma reactor
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Ferroelectric thin films like lead zirconate titanate (PZT) are used to form several different families of MEMS devices. Moving mirrors for optical switching applications utilize the piezoelectric properties of PZT; varactors depend on its dielectric nonlinearity. The oxidizing environment during PZT deposition means that some material capable of resisting oxidation, like platinum, must be used as the metal electrode in any metal-ferroelectric-metal (MFM) stack. Ion milling has been used in laboratory applications for patterning MFM stacks. However, ion milling removal rates are low (~400 Angstroms/min), the throughputs are low, and the etched materials tend to redeposit along the edge of the etch mask, creating veils, or fences, after the etch mask is removed. These residues can lead to yield-limiting defects in finished devices. We report here on MFM stack etch results from a capacitively coupled high density plasma etch reactor. Using photoresist masks, we have demonstrated platinum and PZT etch rates greater than 1000 Angstroms/min at moderate (80 degree(s)C) wafer temperatures. Good etch profiles with no post-etch residue are produced for MFM stacks like those used for a MEMS-based Atomic Force Microscopy application, for example, which employs a bottom platinum layer 1500 Angstroms thick, 2800 Angstroms of PZT, and a platinum top electrode of 1500 Angstroms.
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Paul F. Werbaneth, Paul F. Werbaneth, John Almerico, John Almerico, Leslie G. Jerde, Leslie G. Jerde, Steve Marks, Steve Marks, } "PZT stack etch for MEMS devices in a capacitively coupled high-density plasma reactor", Proc. SPIE 4592, Device and Process Technologies for MEMS and Microelectronics II, (21 November 2001); doi: 10.1117/12.448976; https://doi.org/10.1117/12.448976

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