Method for fabricating micromechanical arm array in micro-electromechanical system (mems) actuators

A method, comprising:

• providing a substrate;
• etching the substrate to form a first trench in the substrate;
• forming an etch stop layer on the substrate;
• forming a silicon sacrificial region in the first trench;
• forming a first micromechanical arm array in the silicon sacrificial region;
• forming a second micromechanical arm array in the silicon sacrificial region;
• patterning and etching a top portion of each micromechanical arm in the first micromechanical arm array to form a protrusion;
• forming a protection film on exposed surfaces of the micromechanical arms in the first micromechanical arm array;
• forming at least one polysilicon sacrificial layer on the micromechanical arms in the second micromechanical arm array and the micromechanical arms in the second micromechanical arm array, wherein the protrusion of each micromechanical arm in the first micromechanical arm array remains exposed;
• forming a metal layer on the at least one polysilicon sacrificial layer and the protrusion of each micromechanical arm in the first micromechanical arm array;
• and
• removing the silicon sacrificial region and the at least one polysilicon sacrificial layer to create a cavity, such that the first and second micromechanical arm arrays are suspended in the cavity.

A method, comprising:

• providing a substrate comprising a first trench;
• forming an etch stop layer on the substrate;
• forming a silicon sacrificial region in the first trench;
• forming a first micromechanical arm array in the silicon sacrificial region;
• forming a second micromechanical arm array in the silicon sacrificial region;
• patterning and etching a top portion of each micromechanical arm in the first micromechanical arm array to form a protrusion;
• forming a protection film on exposed surfaces of the micromechanical arms in the first micromechanical arm array;
• forming at least one polysilicon sacrificial layer on the micromechanical arms in the second micromechanical arm array and the micromechanical arms in the second micromechanical arm array, wherein the protrusion of each micromechanical arm in the first micromechanical arm array remains exposed;
• forming a metal layer on the at least one polysilicon sacrificial layer and the protrusion of each micromechanical arm in the first micromechanical arm array, the metal layer comprising a plurality of joint portions, each of the plurality of joint portions corresponding to and surrounding the protrusion of each micromechanical arm in the first micromechanical arm array;
• and
• removing the silicon sacrificial region and the at least one polysilicon sacrificial layer to create a cavity, such that the first and second micromechanical arm arrays are suspended in the cavity.