Top notch slit profile for mems device

A structure comprising:

• a substrate;
• and
• a microelectromechanical systems (MEMS) device on the substrate, wherein the MEMS device comprises a mechanical mass formed in the substrate;
• wherein the substrate has a slit at the mechanical mass, wherein the slit is disposed through the substrate, from a top surface of the mechanical mass to a bottom surface of the mechanical mass, wherein a width of the slit is substantially uniform from the bottom surface of the mechanical mass to an elevation offset from and between the top and bottom surfaces of the mechanical mass, and wherein the width of the slit bulges from the elevation to the top surface of the mechanical mass.

A method comprising:

• performing a first etch into a first side of a substrate to form a notch extending into the substrate to a first depth;
• performing a second etch into the first side of the substrate to from a trench extending into the substrate to a second depth greater than the first depth, wherein the trench overlaps with the notch and has a lesser width than the notch;
• bonding a carrier substrate to the first side of the substrate with an adhesive filling the notch and the trench and covering the first side of the substrate;
• thinning the substrate from a second side of the substrate, opposite the first side;
• and
• removing the carrier substrate and the adhesive after the thinning.