Micro-electro-mechanical systems (MEMS) having vertical stops and anchor structures

A method of forming one or more stops for a moving mass of a microelectromechanical sensor (MEMS), the method comprising:

• providing a semiconductor substrate of a first material;
• etching a first intermediate layer of a second material overlying the semiconductor substrate to form one or more recessed regions;
• forming a device layer of a third material overlying the intermediate layer,
• wherein the semiconductor substrate, the first intermediate layer, and the device layer are single crystal layers and wherein the device layer is configured to fill the one or more recessed regions in the first intermediate layer that form the one or more stops of the moving mass;
• etching the device layer, the first intermediate layer, and the semiconductor substrate to form etched regions corresponding to at least one anchor;
• forming a first layer of a first dielectric material, wherein the first dielectric material is a conformal material, wherein the first dielectric material couples to the semiconductor substrate at or below a surface thereof, and wherein the at least one anchor is electrically isolated from the semiconductor substrate;
• forming a second layer of a fourth material;
• planarizing a surface of the device layer thereby removing the first dielectric material and the fourth material overlying a surface of the device layer;
• etching the device layer to define the moving mass to expose wherein a surface of the intermediate layer;
• and
• releasing the moving mass to define a predetermined distance between surfaces of the one or more stops and the substrate and to limit an extent of movement of the moving mass to the predetermined distance.

A microelectromechanical sensor (MEMS) having at least one stop for a moving mass, the sensor comprising:

• a substrate comprising silicon;
• a first intermediate layer overlying the substrate, the first intermediate layer comprising silicon germanium (SiGe);
• wherein the moving mass is formed in a device layer of the sensor, the device layer comprising silicon overlying the intermediate layer comprising SiGe,
• wherein the substrate, the first intermediate layer, and the device layer are single crystal layers,
• wherein the first intermediate layer and the device layer have thicknesses beyond a critical thickness,
• wherein the at least one stop extends from a bottom surface of the moving mass to a predetermined depth and has a predetermined area, and
• wherein the first intermediate layer is configured to be removable under the moving mass;
• at least one anchor coupled to the substrate and electrically isolated from the substrate;
• and
• a spring coupled between the at least one anchor and the moving mass and having a spring force greater than a stiction force of the at least one stop to the substrate to support release of the moving mass when the at least one stop couples to the substrate.