MEMS structure and manufacturing method thereof

A method for manufacturing a MEMS structure, comprising:

• providing a MEMS substrate having a first surface;
• forming a first buffer layer having a bixbyite cubic structure on the first surface of the MEMS substrate;
• annealing the first buffer layer, the first buffer layer has a rhombohedral corundum type structure after annealing;
• forming a first roughening layer on the first buffer layer;
• providing a CMOS substrate having a second surface and a bump protruding from the second surface;
• forming a second buffer layer having a bixbyite cubic structure on the second surface of the CMOS substrate, wherein the second buffer layer is apart from the first roughening layer;
• annealing the second buffer layer, the second buffer layer has a rhombohedral corundum type structure after annealing;
• forming a second roughening layer on the second buffer layer;
• removing a portion of the second buffer layer and a portion of the second roughening layer to expose at least a portion of a sidewall of the bump and cover a top surface of the bump;
• and
• bonding the MEMS substrate to the CMOS substrate through a pillar contacting the first surface and the second surface, thereby an air gap ranging from a surface of the first roughening layer to a portion of a surface of the second roughening layer facing toward the first roughening layer, wherein at least a portion of the surface of the first roughening layer is exposed to the air gap.

A method for manufacturing a MEMS structure, comprising:

• providing a MEMS substrate having a first surface;
• providing a CMOS substrate having a second surface, wherein the CMOS substrate comprises a bump protruding away from the second surface;
• forming a second buffer layer on the second surface of the CMOS substrate;
• annealing the second buffer layer, the lattice constant of the second buffer layer after annealing is between about 0.5431 nm and about 0.5507 nm;
• forming a second roughening layer on the second buffer layer, wherein the second roughening layer is free from being in direct contact with the CMOS substrate;
• removing a portion of the second roughening layer and a portion of the second buffer layer to expose at least a portion of a sidewall of the bump a top surface of the bump is remained covered by the second roughening layer and the second buffer layer;
• and
• bonding the MEMS substrate to the CMOS substrate through a pillar contacting the first surface and the second surface.