Removal of MEMS sacrificial layers using supercritical fluid/chemical formulations

Abstract

A method and composition for removing silicon-containing sacrificial layers from Micro Electro Mechanical System (MEMS) substrates having such sacrificial layers is described. The etching compositions include a supercritical fluid, an etchant species, a co-solvent, and optionally a surfactant. Such etching compositions overcome the intrinsic deficiency of SCFs as cleaning reagents, viz., the non-polar character of SCFs and their associated inability to solubilize polar species that must be removed from the semiconductor substrate. The resultant etched MEMS substrates experience lower incidents of stiction relative to MEMS substrates etched using conventional wet etching techniques.

Description

FIELD OF THE INVENTION [0001] The present invention relates to supercritical fluid-based compositions useful in semiconductor manufacturing for the removal of sacrificial layers, e.g., silicon or silicon oxide, from Micro Electro Mechanical System (MEMS) substrates having such sacrificial layers. The compositions also have utility for removing post-ash and post-etch residue. DESCRIPTION OF THE RELATED ART [0002] Micro Electro Mechanical Systems (MEMS) are devices that integrate mechanical and electrical components on a single silicon wafer. The electrical and mechanical components are fabricated using traditional integrated circuit (IC) techniques and “micromachining” processes, respectively. Micromachining is used to produce a number of mechanical devices on the wafer that are able to sense and control the environment, including cantilever beams, hinges, accelerometers, microsensors, microactuators and micromirrors. [0003] The mechanical components on a MEMS wafer are created by de...

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Benefits of technology

[0011] Other aspects, features and embodiments of the invention will be more fully apparent from the ensuing disclosure and appended claims.

Problems solved by technology

A major problem with fabricating MEMS structures is that as aqueous based etching of the sacrificial layer proceeds, stiction may occur, wherein the surface adhesion forces are higher than the mechanical restoring force of the microstructure.

However, etching with neat anhydrous HF can require up to ten hours to form complex microstructures and as such, the presence of some water is necessary to initiate the etch reaction thereby eliminating the advantages of using a water-free etchant.

However, SCFs are highly non-polar and as such, many contaminant species are not adequately solubilized therein.

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