| 摘要 |
PURPOSE:To obtain impurity distribution during the anode oxidation with a constant current by executing the anode oxidation of semiconductor wafer with a constant DC and by measuring change of voltage across such DC source. CONSTITUTION:A wafer 1 is oxidized from the surface through the anode oxidation while a single surface, for example, the rear surface of semiconductor wafer 1 is not separated from the electrolyte. An externally applied voltage is equal to a sum of a voltage drop at the oxide film formed and a voltage drop at the semiconductor and a voltage drop of semiconductor is equal to a withstand voltage of semiconductor wafer under such condition. A withstand voltage of semiconductor wafer in the thickness direction is determined by distribution of impurity in such a direction but depends on electrode area. Therefore, when distribution of impurity from the surface to the end of depletion layer at the time of breakdown is known, distribution of impurity up the deeper area than the depletion layer end can be obtained by measuring voltage change through anode oxidation with a constant current. |
