Rear-projection photodetection yarn clearing apparatus and ultraviolet enhanced silicon photodiode thereof

A rear-projection photodetection yarn clearing apparatus, comprising a light emitting diode and a detector arranged behind a to-be-detected yarn, and further comprising a reflector arranged in front of the to-be-detected yarn, wherein a front end face of the light emitting diode is flush with a photosurface of the detector, a light filter for capturing light rays having a waveband ranging from 330 nm to 470 nm is further arranged in front of the light emitting diode and the detector, a light-reflecting surface of the reflector is in parallel with the photosurface of the detector;

• the light emitting diode comprises an ultraviolet light emitting diode, the detector comprises an ultraviolet enhanced silicon photodiode, the ultraviolet enhanced silicon photodiode is made from a high-resistivity N-type (111) silicon wafer having a resistivity of 3,000Ω·cm and a field oxide thickness of 1,000 nm, a side of the silicon wafer is implanted with boron having an implantation dose of 4×1014 cm−2˜5×1014 cm−2 and energy of 30 Kev to form a P-type area, another side of the silicon wafer is implanted with phosphorus having an implantation dose of 5×1015 cm−2 and energy of 100 Kev to form an N+ area, the P-type area of the silicon wafer is polished, the N+ area of the silicon wafer is burnished, and both the P-type area and the N+ area have an oxide layer thickness of 50 nm˜60 nm.