Micromechanical arm array for mems actuators

A method for making a micromechanical arm array for a MEMS actuator, comprising:

• receiving a package that comprises a top wafer bonded to a bottom wafer;
• patterning the top wafer to form a recess that includes a plurality of pillars spaced apart from each other within the recess;
• forming a dielectric layer on exposed surfaces of the recess in the top wafer;
• forming a metal layer upon each pillar in the recess to obtain a horizontal composite structure upon each pillar;
• forming a sacrificial spacer upon each horizontal composite structure;
• forming a dielectric layer on exposed surfaces of the horizontal composite structures and the sacrificial spacers, resulting in a first set of trenches and a second set of trenches within the recess, and in a first dielectric layer upon the top wafer;
• depositing a piezoelectric material into the first set of trenches to form a first array of fingers;
• depositing an electrically conductive material into the second set of trenches to form a second array of fingers, wherein distal ends of the first array of fingers and distal ends of the second array of fingers are interposed between each other;
• forming a vertical composite structure upon each finger of the first array of fingers, each vertical composite structure comprising a dielectric layer bonded to a metal layer;
• forming a metal cap that contacts each finger in the second array of fingers and each vertical composite structure upon the first array of fingers;
• etching to remove the sacrificial spacers and form a cavity within the top wafer;
• and
• annealing to convert each horizontal composite structure and each vertical composite structure into a micro-spring.

A MEMS actuator, comprising:

• an anchor structure;
• and
• a plurality of micromechanical arm arrays connected to the anchor structure, each arm array comprising:
• a first array of spaced-apart fingers formed from a piezoelectric material and extending from a first arm in a first horizontal direction;
• and
• a second array of spaced-apart fingers formed from an electrically conductive material and extending from a second arm in a second horizontal direction opposite the first horizontal direction, wherein distal ends of the first array of fingers and distal ends of the second array of fingers are interposed between each other;
• and
• micro-springs connecting the interposed distal ends of each set of adjacent fingers.