Proceedings Article | 28 April 2017
Proc. SPIE. 10209, Image Sensing Technologies: Materials, Devices, Systems, and Applications IV
KEYWORDS: Visible radiation, Avalanche photodetectors, Magnesium fluoride, Sensors, Metals, Ultraviolet radiation, Dielectrics, Silicon, Quantum efficiency, Reflectivity, Atomic layer deposition, Aluminum, Dielectric filters, Avalanche photodiodes, CCD image sensors, Far ultraviolet, Internal quantum efficiency, Bandpass filters
In this work, we show that the direct integration of ultraviolet metal-dielectric filters with Si sensors can improve throughput over external filter approaches, and yield devices with UV quantum efficiencies greater than 50%, with rejection ratios of visible light greater than 10<sup>3</sup>. In order to achieve these efficiencies, two-dimensional doping methods are used to increase the UV sensitivity of back-illuminated Si sensors. Integrated filters are then deposited by a combination of Al evaporation and atomic layer deposition of dielectric spacer layers. At far UV wavelengths these filters require the use of non-absorbing dielectrics, and we have pursued the development of new atomic layer deposition processes for metal fluorides materials of MgF<sub>2</sub>, AlF<sub>3</sub> and LiF. The performance of the complete multilayer filters on Si photodiodes and CCD imaging sensors, and the design and fabrication challenges associated with this development are demonstrated. This includes the continued development of deep diffused silicon avalanche photodiodes designed to detect the fast 220 nm emission component of barium fluoride scintillation crystals, while optically rejecting a slower component at 300 nm.
