Dynamic Focusing Technique for Photolithographic Tools
Original Publication Date: 1986-Jan-01
Included in the Prior Art Database: 2005-Mar-08
All current techniques for focus optimization of photolithographic tools depend upon the use of the tool, the exposure and development of a suitable pattern onto a photoresist-coated wafer and the subsequent reading of this patterned wafer. Focus information is then entered into the tool microprocessor and adjustments made (if necessary). A new technique is now available to provide an active optical feedback system so that focus correction can be accomplished without the need for exposing, developing and reading a patterned wafer. A laser is used as the light source, preferably one which has a wavelength within the high reflectance bandpass of the mirror coatings but outside the sensitivity range of the photoresist used in the tool so that active focus monitoring and tool exposure can occur simultaneously.