Automatic Inspection of Masks for Glass Substrates for the Production of Semiconductor Devices
Original Publication Date: 1986-Apr-01
Included in the Prior Art Database: 2005-Mar-08
The measuring values of the photoelectrically scanned mask to be inspected are digitized and directly compared with computer-stored digital values. During scanning, the influence of long-term variations, in particular of the illuminating system or the gain factor of a video scanner, is taken into account to avoid undesired glare, as occurs when the illumination is readjusted. For scanning the transparent glass substrate or a portion thereof (not including mask regions), the illumination has to be readjusted to a particular percentage, say, 5%, of the scanning points having a value that is less than the saturation value. This reference value of 5% is used as a basis for mask scanning.