Pressure sensor development
1) 1945 - 1960: This stage is marked by the invention of the bipolar transistor in 1947. Since then, this characteristic of semiconductor materials has been more widely used. C.S. Smith and 1945 discovered the piezoresistive effect of silicon and germanium, that is, when an external force acts on a semiconductor material, its resistance will change significantly. The pressure sensor made according to this principle is to attach a strain gauge to a metal thin film, that is, convert the force signal into an electrical signal for measurement. The minimum size at this stage is approximately 1 cm.
2) The stage of technological development (1960 - 1970): With the development of silicon diffusion technology, technicians choose the appropriate crystal orientation on silicon (001) or (110) crystal surface to directly spread the strain resistance on the crystal surface, then The back is processed into a concave shape to form a thin silicon elastic diaphragm called a silicon cup. This type of silicon sensor has the advantages of small size, light weight, high sensitivity, good stability, low cost, and ease of integration, and realizes a metal-silicon eutectic, which offers possibilities for commercial development.
3) Commercialization and integrated processing stage (1970 - 1980): The anisotropic etching of silicon was applied on the basis of silicon diffusion theory. The diffusion silicon sensor was mainly based on the anisotropic etching technology of silicon. It has developed into anisotropic silicon processing technology that can automatically control the thickness of silicon film [mainly in the V-groove method, automatic boron concentration suspension method, automatic anodic oxidation method, and computer control automatic suspension method]. Due to the possibility of simultaneous corrosion on multiple surfaces, thousands of silicon pressure membranes can be produced at the same time, achieving an integrated factory processing model and further reducing costs.
4) Micro-machining (1980-present): Nanotechnology emerged at the end of the last century, making micro-machining possible.