DESIGN AND SIMULATION OF PERMISSIBLE TOLERANCE DURING FABRICATION OF INFRARED-INDUCED TRANSMISSION FILTERS

The design and simulated performance characteristics of narrow band-in duced transmission infrared filters in the wavelength range of 2000 to 4500 nm are presented. These dielectric-spacer-metal-spacer-dielectri c (D-S-M-S-D) filter structures are composed of Si as high index diele ctric (D) and Al2O3 as low index dielectric (D) or spacer (S) and Al a s the metal (M). Typically, a total of 10, 12, or 13 layers are requir ed with an aluminum layer in the middle of the filter stack. The bandw idth of these filters is in the range of 20 to 25 nm. Rejection of the se filters in the long wavelength range is very good. The effect of th ickness errors on the performance of filters has been analyzed. Based on the numerical simulation of an actual fabrication process, the perm issible tolerance for process monitoring is investigated. Numerical si mulations show that a high production yield may be obtained if the ref lectance errors are kept within +/-0.1% during process monitoring in t he manufacture of these filters. (C) 1997 Society of Photo-Optical Ins trumentation Engineers.