Manufacturing method of fir sensor with two absorption layers

A manufacturing method of a far infrared (FIR) sensor, comprising:

• forming a thermopile structure on a substrate;
• forming a first metal layer upon the thermopile structure and partially overlapping with the thermopile structure;
• forming a blocking layer upon the thermopile structure and opposite to the thermopile structure;
• forming a second metal layer upon the blocking layer and opposite to the blocking layer, wherein the thermopile structure, the first metal layer, the blocking layer and the second metal layer are encapsulated in a dielectric layer;
• etching from a surface of the dielectric layer to the first metal layer, the second metal layer and the substrate using a first etching process;
• and
• removing the first metal layer, the second metal layer and a part of the substrate under the thermopile structure using a second etching process such that the dielectric layer between the thermopile structure and the blocking layer forms a double-layer heat absorption layer.