Patent ID: 8168509

Claim:
An etching method, comprising: forming a thin layer on a first surface of a first substrate, the first substrate being doped with first impurities having a first doping concentration and the thin layer being doped with second impurities having a second doping concentration lower than the first doping concentration; forming a second substrate on the thin layer; polishing a second surface of the first substrate to provide a polished first substrate; cleaning the polished first substrate using a cleaning solution including ammonia and deionized water to provide a cleaned first substrate, wherein the polishing of the second surface of the first substrate lowers a doping concentration of the first impurities at an exposed portion of the first substrate to be less than the first doping concentration to provide a lowered doping concentration, and the cleaning of the polished first substrate removes the exposed portion of the first substrate having the lowered doping concentration; and etching the cleaned first substrate to remove the first substrate and expose the thin layer.