Design of an integrated circuit with buried double junction photodiodes for optical immunoassays

Abstract

Optical immunoassays require measurement systems capable of distinguishing the light from the laser source, used to illuminate the assay, from the light generated by the particles contained within the assay itself (fluorescence). The main challenge is that the light used to excite the sample is several orders of magnitude more intense than that generated by fluorescence. Usually, single junction photodiodes and optical filters are used. The sensitivity of these schemes is limited by the filter performance. In this work, the design of a CMOS integrated circuit including buried double junction photodiodes (BDJ) is presented. This approach allows the measurement of both light sources simultaneously. From simulations, it is shown that this integrated circuit with BDJ would achieve a better detection limit than the scheme based on single-junction photodiodes of equivalent silicon area. Furthermore, integrating the photodetectors and the reading circuit on the same chip would make the system suitable to be used in biomedical applications such as Point-of-Care (POC) devices.

Keywords

• inmunoensayos
• fotodiodos
• point-of-care
• cmos