A method of making a microelectromechanical systems (MEMS) device includes etching away a sacrificial material layer to release a mechanical element of the MEMS device. The MEMS device is formed at least partially on the sacrificial material layer, and the etching leaves a residue in proximity to the mechanical element. The residue is exposed to an anhydrous solution to remove the residue. The residue may be an ammonium fluorosilicate-based residue, and the anhydrous solution may include acetic acid, isopropyl alcohol, acetone, or any anhydrous solution that can effectively dissolve the ammonium fluorosilicate-based residue.

The present disclosure involves forming a method of fabricating a Micro-Electro-Mechanical System (MEMS) device. A plurality of openings is formed in a first side of a first substrate. A dielectric layer is formed over the first side of the substrate. A plurality of segments of the dielectric layer fills the openings. The first side of the first substrate is bonded to a second substrate that contains a cavity. The bonding is performed such that the segments of the dielectric layer are disposed over the cavity. A portion of the first substrate disposed over the cavity is transformed into a plurality of movable components of a MEMS device. The movable components are in physical contact with the dielectric the layer. Thereafter, a portion of the dielectric layer is removed without using liquid chemicals.

In the method, a sidewall pattern is formed in a side wall of a first resist pattern that is formed on a second hard mask layer of a base material in which first and second hard mask layers are laminated in the order of description, a second hard mask pattern is formed by etching the second hard mask layer by using the sidewall pattern as a mask, a first hard mask pattern is formed by etching the first hard mask layer by using, as a mask, the second hard mask pattern and a second resist pattern that is formed on the first hard mask layer of the base material, and the first and second fine patterns are formed by etching the base material by using the first hard mask pattern as a mask.

A preclean process may be omitted from a eutectic bonding sequence. To remove oxide from one or more surfaces of a device wafer of a micro-electromechanical-system (MEMS) structure, a duration of an acid-based etch process in the eutectic bonding sequence may be increased relative to the duration of the acid-based etch process when the preclean process is performed. The increased duration of the acid-based etch process enables the acid-based etch process to remove the oxide from the one or more surfaces of the device wafer without the use of a preceding preclean process. This reduces the complexity and cycle time of the eutectic bonding sequence, reduces the risk of stiction between suspended mechanical components of the MEMS structure, and/or reduces the likelihood that the MEMS structure may be rendered defective or inoperable during manufacturing, which increases process yield.