X-RAY FLUX DETECTORS
Original Publication Date: 1991-Jul-01
Included in the Prior Art Database: 2001-Dec-12
Overlay of features in integrated circuits is a func- tion of critical dimension control and registration errors. Device functionality depends on overlay ade- quate for the design so critical dimension control receives a lot of attention from process engineers. Pattern transfer in optical lithography involves the use of light to transfer the image of a mask to the photore- sist on a wafer. The intensity and uniformity of the light source is an important parameter that is charac- terized routinely and studied carefully for its impact on critical dimension control. Optical lithography has some very mature tools to study the quality of the light source. These include real time sensors sensitive to the same wavelengths that the resist is most respon- sive to, sensors that detect at the most intense actinic wavelengths, and broadband sensors. Generally, the size of the monitoring pixel can be quite small so the exposure field can he examined in fine increments.