US Patent 7595539 - MEMS release using hydrogen gas

http://www.freepatentsonline.com/7595539.html

The moving parts of micromechanical structures typically need to be formed by a method including an etching steps which removes some underlying sacrificial layer material. Hydrofluoric acid is often used for this purpose but can be damaging and leave behind residue. This patent from Robert Bosch GmbH teaches an alternative using a hydrogen gas etchant. The claims seem to rely on a product-by-process justification of patentability which indicates that the process should produce a structurally differentiated MEMS device from prior MEMS devices released by other etchants (otherwise the claims would be invalid). Claim 1 reads:

1. A device including micromechanical elements, comprising:

a substrate layer;

a sacrificial layer on at least a first portion of the substrate layer; and

a function layer on at least a second portion of the sacrificial layer;

wherein the function layer is released from the substrate layer by exposing the device to gaseous hydrogen.