ENDPOINT DETECTING METHOD AND ASHING DEVICE

PROBLEM TO BE SOLVED: To prevent charge-up damage by detecing the endpoint in a highly precise manner even when the condition of treatment changes. SOLUTION: Semiconductor wafers, on which dummy resist is applied, are treated for every prescrived number of sheets, and light-emitting spectral intensity is convertd to a voltage waveform using a sensor 6 and a monitoring part 7. The light-emitting spectral intensity ratio is computed by an arithmetic part 12, the voltage waveform of light-emitting spectral intensity, to be measured and converted when normal ashibng processing is conducted, is amplified by the light-emitting spectral intensity ratio, and the endpoint of ashing processing is detected by a CPU9 based on the amplified voltage waveform.