Patent ID: 7824974

Claim:
A method for manufacturing a constant current source device comprising: (a) thermally oxidizing a P-type silicon substrate in an oxidation furnace to grow an oxide layer protecting film, providing a first photo mask on the oxide layer protecting film and processing in a photolithography machine, and using a corrosive liquid containing a HF (hydrofluoric acid) to etch the oxide layer protecting film; (b) implanting boron difluorides or boron ions in the P-type silicon substrate and forming a P+ guard ring and a P+ substrate region by thermally driven-in; (c) providing a second photo mask on the oxide layer protecting film and processing in the photolithography machine, etching the oxide layer protecting film by dry etching method, implanting arsenic ions or arsenic ions and phosphorous ions in the P-type silicon substrate, forming a heavily doped N+ region comprising an N+ drain region and an N+ source region after thermal driven-in and forming a N+ guard ring simultaneously after thermally driving-in; (d) providing a third photo mask on the oxide layer protecting film and processing in the photolithography machine, and using the corrosive liquid containing the HF (hydrofluoric acid) to etch the oxide layer protecting film, using a dry thermal oxidation or a wet thermal oxidation at high temperature to form gate, source and drain oxide layers, then implanting phosphorous ions or phosphorous ions and boron ions, followed by high temperature drive-in; (e) providing a fourth photo mask on the oxide layer protecting film and processing in the photolithography machine, etching the oxide layer protecting film with dry etch or wet etch processes to form drain through holes, source N+ through holes, and source P+ substrate through holes; and (f) depositing a metal layer by sputtering or evaporation, using a metal layer mask on the metal layer and processing in the photolithography machine, and etching the metal layer and forming a drain metal, a source metal, a gate metal, and a connection metal by a dry or wet etching method.