A single mask process for the realization of fully-isolated, dual-height MEMS metallic structures separated by narrow gaps

Abstract

Multi-height metallic structures are of importance for various MEMS applications, including master molds for creating 3D structures by nanoimprint lithography, or realizing vertically displaced electrodes for out-of-plane electrostatic actuators. Normally these types of multi-height structures require a multi-mask process with increased fabrication complexity. In this work, a fabrication technology is presented in which fully-isolated, dual-height MEMS metallic structures separated by narrow gaps can be realized using a self-aligned, single-mask process. The main scheme of this proposed process is through-mold electrodeposition, where two photoresist mold fabrication steps and two electrodeposition steps are sequentially implemented to define the thinner and thicker structures in the dual-height configuration. The process relies on two selfaligned steps enabled by the electrodeposited thinner structures: a wet-etching of the seed layer utilizing the thinner structure as an etch-mask to electrically isolate the thinner and the thicker structures, and a backside UV lithography utilizing the thinner structure as a lithographic mask to create a high-aspect-ratio mold for the thicker structure through-mold electrodeposition. The latter step requires the metallic structures to be fabricated on a transparent substrate. Test structures with differences in aspect ratio are demonstrated to showcase the capability of the process.

A bi-stable vertical magnetic actuator with non-contact latching based on magnetic microlamination technology

“…Conventional multimask layerby-layer fabrication is not ideal for the proposed design, due to increased fabrication complexity and alignment issues associated with thick, multiheight structures [17]. Hence, we developed a fabrication process capable of creating dualheight magnetic structures separated by a narrow gap detailed in [9]. A brief process description is provided here for the convenience of the reader, as shown in figure 5.…”

“…In this work, we propose a bi-stable vertical magnetic actuator design that utilizes only magneto-static force to realize latching (without any mechanical contact), and by integrating a current conductor and a permeable component into a single piece, we significantly reduce the fabrication complexity down to a single-mask process. This single-mask process is enabled by two recently-developed technologies: a single-mask process for dual-height metallic structures [9]; and a robotic-assisted magnetic lamination technology [10,11]. The magnetic lamination technology in which permeable and non-permeable materials are sequentially electrodeposited in a multilayer fashion has been previously used to achieve multilayer surface/interface-property enabled functions and applications (e.g.…”

In Situ Stress Measurement of Ni Electrodeposition Using Lateral Shearing Interferometry

“…Generally, the deposition process can be divided into two states (early state and steady-state) based on the stress-dependency on the process parameters via variation of deposition thickness 12 The stress behavior at different deposition thickness is responsible for different practical applications. For example, MEMS/NEMS processing needs the measurement of stress evolution at early-state with a relative thinner thickness, 13,14 while fabrication of mold inserts with multi-scale structures (micro/nano structures and macro structures) needs the measurements at a broad range of deposition thickness. 15,16 However, according to the Stoney formula, affected by the steadiness of substrate, the in situ stress measurement of the nanoscale deposition layer challenges the conventional experimental methods.…”