Method to form a rough crystalline surface

A microelectromechanical systems (MEMS) package comprising:

• an integrated circuit (IC);
• a substrate bonded to and independent of the IC, wherein the substrate defines a MEMS structure that is moveable relative to the IC within a cavity between the IC and the substrate;
• a crystalline layer in the cavity and having a rough surface configured to reduce stiction between the MEMS structure and the IC;
• and
• a plurality of micro features embedded in the crystalline layer along grain boundaries of the crystalline layer, wherein the crystalline layer defines trenches at the rough surface that space the micro features, and wherein the micro features are masks or cavities.

A microelectromechanical systems (MEMS) package comprising:

• an integrated circuit (IC);
• a substrate bonded to and independent of the IC, wherein the substrate defines a MEMS structure that is moveable relative to the IC within a cavity between the IC and the substrate;
• a crystalline layer in the cavity and having a rough surface configured to reduce stiction between the MEMS structure and the substrate;
• and
• a plurality of micro masks diffused into the crystalline layer along grain boundaries of the crystalline layer from the rough surface of the crystalline layer, wherein the rough surface has a plurality of trenches separating the micro masks from one another.

A microelectromechanical systems (MEMS) package comprising:

• a first substrate;
• a crystalline layer on the first substrate;
• and
• a plurality of dielectric masks extending into the crystalline layer along grain boundaries of the crystalline layer from a top surface of the crystalline layer, wherein the dielectric masks are localized to the grain boundaries and are on multiple sides of corresponding crystalline grains at the top surface;
• wherein the crystalline layer has a plurality of trenches uncovered by the dielectric masks.