| 摘要 |
PROBLEM TO BE SOLVED: To prevent a reaction by-product, i.e., gas molecules, from blocking high speed uniform reaction for forming porous silicon by performing a chemical reaction while controlling the concentration of a gas dissolved into the reaction liquid in a reaction tank below an under reaction saturation solubility. SOLUTION: A silicon wafer 200 is brought, on one side thereof, into contact a reaction liquid 201 and, on the other side thereof, to a conductive solution, i.e., an electrolyte 202. A negative voltage is applied to the reaction liquid 201 through a negative electrode 203 and a positive voltage is applied to the conductive solution 202 through a positive electrode 204. A PID cooler/heater or a heat-exchanger is set on a circulation line 210b in order to heat/cool the circulating reaction liquid. Preferably, the heating/cooling is performed to keep the temperature of the reaction liquid 201 in a reaction tank 30 within±0.5. When the quantity of hydrogen dissolved into the reaction liquid 201 in the reaction tank 30 is observed under that state, it is about 1 ppb or less which is significantly lower than the saturation solubility, i.e., 1 ppm, during anodic formation. |
