Effect of a guard-ring on the leakage current in a Si-PIN x-ray detector for a single photon counting sensor (Silicon devices and materials: 第15回先端半導体デバイスの基礎と応用に関するアジア・太平洋ワークショップ(AWAD2007))

概要

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PIN diodes for digital X-ray detection as a single photon counting sensor were fabricated on a floating-zone (FZ) n-type (111), high resistivity (5〜10kΩ・cm) silicon substrates (500μm thickness). Its electrical properties such as the leakage current and the breakdown voltage were characterized. The size of pixels was 100μm×100μm. The p+ guard-ring was formed around the active area to reduce the leakage current. After the p+ active area and guard-ring were fabricated by the ion-implantation, the extrinsic-gettering on the wafer backside was performed to reduce the leakage current by n+ ion-implantation. PECVD oxide was deposited as an IMD layer on front side and then, metal lines were formed on both sides of wafers. The leakage current of detectors was significantly reduced with a guard-ring when compared with that without a guard ring. The leakage current showed the strong dependency on the gap distance between the active area and the guard ring. It was possible to achieve the leakage current lower than 0.2 nA/cm^2.
社団法人電子情報通信学会の論文
2007-06-18