Hard-Baked Photoresist as a Sacrificial Layer for Sub-180 °C Surface Micromachining Processes

Abstract

This letter proposes a method for utilizing a positive photoresist, Shipley 1805, as a sacrificial layer for sub-180 °C fabrication process flows. In the proposed process, the sacrificial layer is etched at the end to release the structures using a relatively fast wet-etching technique employing resist remover and a critical point dryer (CPD). This technique allows high etching selectivity over a large number of materials, including silicon-based structural materials such as silicon-carbide, metals such as titanium and aluminum, and cured polymers. This selectivity, as well as the low processing thermal budget, introduces more flexibility in material selection for monolithic integration above complementary metal oxide semiconductor (CMOS) as well as flexible substrates.

Pattern transferring of Prolift-100 polymer sacrificial layers with controlled sidewall profile

“…While organic materials, including photo-definable epoxies such as SU-8, are also extensively used (Tripathi et al 2015), they require special care to prevent inadvertent cross-linking from exposure to high temperature or radiation during subsequent processing steps (Chung and Allen 2005). Photoresist sacrificial layers have also been used for MEMS devices fabrication but these materials cross-link at temperatures above 180 • C and they are unsuitable for inductively coupled plasma vapour deposition (ICPCVD) materials which require higher temperatures than 175 • C for high-quality, tensile-stress silicon based optical materials (Tawfik et al 2018, Minhas et al 2019, 2020. Polymer organic sacrificial layers offer good thermal stability, high radiation resistance, good mechanical strength, controllable thickness, and ease of removal using both wet and dry etching process.…”

Forming of Dynamic Microstructure of Flexible Polymer

“…Under the establishment and development of microsystem technology, microsystems have been rapidly, effectively, and continuously used in science and technology industries. The microelectromechanical system (MEMS) process technology [1,2,3,4] and semiconductor process technology [5,6,7] are critical in the mass production of microsystem components. They are both integrated with multiple technologies, and generally arranged according to multiple sequential processes, including the cleaning and surface preparation of wafer preprocesses, photoresist coating and baking, alignment exposure, development, etching (or ion implantation), etc., as the final process of creating micrographic components or micro molds.…”