Backside illuminated AlGaN‐on‐Si UV detectors integrated by high density flip‐chip bonding

Abstract

We report on the fabrication of integrated AlGaN‐on‐Si‐based ultraviolet photodetectors. Devices were interconnected with dedicated Si‐based fanout structures using flip‐chip bonding. The interconnects were In solder bumps with a 20 µm pitch. Backside illumination was enabled by removing the Si substrate over the active area, leaving an ultrathin AlGaN membrane with the thickness of 400 nm and the area of 4x4 mm2 supported by an array of In bumps. The presented devices act as a test vehicle for the 10 µm pitch hybrid AlGaN Extreme Ultraviolet (EUV) imagers and prove the feasibility of backside illumination in an integrated device. The use of AlGaN as the active layer provides intrinsic solar blindness with a high rejection ratio of visible and infrared spectra, which is one of the most critical limitations of the commonly used Si‐based devices. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Ultraviolet Photodetectors: From Photocathodes to Low-Dimensional Solids

“…However, illumination from the front is necessary for reaching shorter wavelengths than the cut-off wavelength of the substrate material, e.g., in the case of VUV applications. Backside illumination is conceivable in the EUV (i.e., below 30 nm) using a backside thinned device (e.g., removing the Si substrate [79]) and making it transparent to the EUV and X-ray radiation. A cross-sectional view of an AlGaN p-i-n back-illuminated photodiode is shown in Figure 35 [80].…”