Development of Micro-Machined Porous-Silicon Capacitive Chip for Quantification & Sensing of Organic Solvents
In this work, a porous structured single-layered silicon chip is developed using laser micro-machining, and capacitive-based sensing application is demonstrated for quantification and characterization of organic chemical compounds. The design of capacitive silicon chip is analyzed by simulating the porous silicon structure with electrode contact pads using Synopsys Sentaurus Technology Computer-Aided Design (TCAD) tool. The prototype chip was fabricated with a pulsed fiber laser. The scanning electron microscopy of the porous silicon wafer shows an average pore diameter of 55.22 µm and pore depth of 98.9 µm. The prototype chip was realized by the deposition of electrical contact pad using silver (Ag) conductive paste and Cu-wire along the two opposite facing edges of the silicon die. Different organic solvents were tested and analyzed to estimate the linearity performance of the proposed chip. The developed chip also has a stable performance up to 28 days at room temperature. The applicability of the proposed sensor chip is demonstrated for sensing and quantification of Fenvalerate chemical which is a synthetic pesticide used in farming. The sensitivity and the limit of detection was found to be 0.26 nF/ppm and 0.4900 ppm respectively. The capacitive based porous silicon chip is suitable for low-cost sensing and monitoring of chemical used in pharmaceutical, food and chemical industry.
Keywords-Capacitive sensing; Chemical; Porous silicon structure; Pulsed Fiber Laser (PFL); Scanning Electron Microscope; Sensitivity