| 摘要 |
<p>PROBLEM TO BE SOLVED: To detect whether there is a substrate or not on each storing shelf in a cassette by comparing a reference waveform stored previously in a reference waveform storing means with a waveform of a substrate detecting signal from a substrate detecting means, while a cassette stage with a cassette thereon is moved relative to the substrate detecting means. SOLUTION: When a cassette (C), in which a wafer (W) is stored is mounted on a cassette mounting stage 1, a wafer detector 2 is moved downward after the wafer detector 2 is moved once above the cassette (C). At this time, a waveform of a substrate detecting signal from a wafer detector 2 is stored as a detection waveform in a memory. Then, the a reference waveform stored previously in the memory is compared with the detected waveform in the memory. On the basis of the difference between the reference waveform and the detected waveform, whether there is a wafer or not in each storing shelf (SL) in the cassette (C) is determined. Consequently, whether there is a wafer or not in each storing shelf (SL) can be determined without using a linear encoder.</p> |
