Single (111)-Wafer Fabrication of 100-μm Scale Thermopile/Absorber Double-Deck Structure for High-Detectivity IR-Detection

摘要

This paper reports a $100-mu mathrm{m}$ scale p^{+Si/Au infrared (IR) thermopile detector with a novel thermopile/absorber double-deck structure, which is micromachined only from the front side of (111) silicon wafer for low-cost IC-foundry compatible manufacturing. The tiny-sized IR detector consists of six pairs of single-crystalline-silicon/ Au thermocouples that show significantly higher Seebeck coefficient and lower noise, compared with the traditional polysilicon/metal counterparts. In order to increase absorption of IR radiation, an umbrella-shaped Si3N4 IR absorbing membrane is designed to replace the traditional plane IR absorbing film. The umbrella-shaped absorbing film is suspended above the thermopile layer to form a double-deck 3D-structure for increasing heat absorbing area. The novel structural configuration is realized to achieve high detectivity of the ultra-small sized ($96 mu mathrm{m}imes 106 mumathrm{m}$) IR thermopile detector. The testing results demonstrate that the tiny-size IR thermopile detector achieves an ultra-high detectivity of $1.01imes 10^{8}$ cm·Hz1/2·W−1 and a fast response of 0.74ms.}