Patent ID: 11923223
Assignee: DISCO CORPORATION
Field: Semiconductors (Electrical engineering)
Classification: CPC H | IPC H

Claim 0:
1. A wafer detecting apparatus for detecting whether or not there is a wafer in a cassette that has opposite side-walls in which a plurality of pairs of slots vertically spaced from one another are defined and that is capable of storing wafers in such a manner that each of the wafers is retained by a corresponding one of the pairs of slots, the pair of slots being positioned at a same height in confronting relation to each other, the wafer detecting apparatus comprising:
a detecting unit having a non-contact-type sensor for detecting a front portion of the wafer laterally of the wafer in the cassette that has an open front end;
a lifting and lowering unit for selectively lifting and lowering the detecting unit vertically;
a tilting unit for selectively rotating the detecting unit about a horizontal rotational axis;
an output unit for outputting information regarding the wafer stored in the cassette;
a controller for controlling operation of the detecting unit, the lifting and lowering unit, the tilting unit, and the output unit; and
an input unit for entering information regarding the wafer stored in the cassette into the controller, wherein
the controller includes
a storage section for storing a value of an actual thickness of the wafer stored in the cassette, the value being entered from the input unit, and a threshold value representing an allowable range for a difference between a value of an apparent thickness of the wafer and the value of the actual thickness of the wafer,
a determining unit for determining whether or not the difference between the value of the apparent thickness of the wafer and the value of the actual thickness of the wafer that has been stored in the storage section exceeds the threshold value, the value of the apparent thickness of the wafer being obtained by operating, while actuating the lifting and lowering unit to selectively lift and lower the detecting unit and while actuating the tilting unit to selectively rotate the detecting unit about the horizontal rotational axis, the non-contact-type sensor to detect whether or not there is the wafer in the cassette, and
a warning section for operating the output unit to issue a warning about an irregularity concerning the wafer stored in the cassette, if the determining section determines that the difference exceeds the threshold value.