DUV radiation damage of the imaging sensor limits the lifetime of current Wafer/Mask Inspection (MI) cameras. Presented are design considerations and recent 193nm lifetime results of Back-Side Thinned (BST) CMOS sensors. Extremely high DUV durability along with high sensitivity (Quantum Efficiency) were achieved, using unique BST and passivation processes developed at JPL/NASA especially, for our application, by the utilization of a multi-layer MBE Delta-Doping (DD) of Boron Ions on the light sensitive surface of the CMOS. The sensors endured billions of pulses without degradation, in comparison to the much shorter DUV lifetime of current imaging sensors, even at lighter operating exposure conditions. A unique measurement method, developed at AMAT for this purpose, had been utilized, measuring small changes (1%) in local response,

A 3 Megapixel, 5 um square pixels sensor, was back-thinned and DD with two, very dense, thin layers of Boron ions, separated by only 1 nm silicon, that were produced using an automated MBE system. An Excimer 193nm, pulsed DUV laser that emits collimated 10 nsec pulses at a 1000 Hz, was used to illuminate the camera sensor at controlled exposures. A unique beam shaping system was developed and employed in order to expose the sensor to the DUV illumination and enable to measure small possible changes in local QE while eliminating most of the noise sources. An analysis of a 100 consecutive images following 2.1B (Billions) of 193 nm laser pulses showed no evidence of any degradation of the illuminated area (within +1%).

Current estimations are that actual lifetime exceeds 10B laser pulses (equivalent to on tool lifetime of >2 years). The BST DD technology was also verified to meet inspection requirements by measurements of the internal QE to be ~100% (excluding Quantum Yield), no image memory (LAG), to be present at 1000 fps, no blooming and almost ideal MTF (Modulation Transfer Function).