Materials and process development for the fabrication of far ultraviolet device-integrated filters for visible-blind Si sensors

Abstract

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 3 . 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 2 , AlF 3 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.

Mu2e-II: Muon to electron conversion with PIP-II

“…Atomic-layer-deposition (ALD) bandpass filters integrated with the silicon structure of the photosensor promise several advantages. These can be either avalanche photodiode [121] or silicon photomultiplier devices [122]; work has been done on both. These have excellent quantum efficiency at 220 nm, strong rejection of 300 nm response, time response superior to existing SiPMs and adequate longevity in the face of exposure to strong UV ra-diation.…”

Hyperion: the origin of the stars. A far UV space telescope for high-resolution spectroscopy over wide fields

“…The CCD has a 4k×4k format with 12 μm pixels. The detectors are UV optimized via delta-doping 29 , 163 – 165 and a detector-integrated directly deposited metal-dielectric filter, 166 , 167 which provide out of band rejection. The UV camera system meets all Hyperion performance and environmental requirements and has been demonstrated to be technology readiness level (TRL) 6 by means of a combination of analysis and measurements on high fidelity prototypes.…”

Advances in detector-integrated filter coatings for the far ultraviolet

“…Because silicon itself is an effective UV reflector, there are significant throughput advantages in integrating these coatings directly on a device as highlighted in Figure 1. [3,4] In these calculations the modeled transmission of the filter coating is equivalent to the predicted external QE of the detector due to the 100% internal QE afforded by the delta-doping process. As shown in Figure 2, these filters have been developed at JPL for a number of applications including high energy physics detectors, [5,6] and astrophysics instruments such as the SPARCS CubeSat.…”