Humidity Diode Sensors Based on 1D Nanosized Silicon Structures

Introduction. Humidity measurement is essential in microelectronics, aerospace, biomedical, and food industries, as well as in households for climate control. Currently, various types of devices have been used as humidity sensors: capacitive, resistive, diode, gravimetric, optical structures, field-effect transistors and devices based on surface acoustic waves.Problem Statement. Today, there is a need to develop IC-compatible humidity sensors that have high sensitivityand low cost. To this end, silicon nanowires have been successfully used in resistive and capacitive humidity sensors. However, there is a lack of research on the nanowire effect on device parameters of diode-type humidity sensors.Purpose. To develop diode sensors based on silicon nanowires and to determine the effect of process parameters of synthesis and structural features of nanowires on the performance of humidity sensors.Materials and Methods. The process of sensor fabrication includes several steps: chemical cleaning of silicon wafer, synthesis of silicon nanowires using standard or modified metal-assisted chemical etching, phosphorus diffusion to create a p-n junction, front and back metallization. The surface morphology of the nanostructures has been studied by scanning electron microscopy. The humidity-sensitive characteristics have been studied with theuse of salt hygrostats.Results. It has been shown that the addition of one-dimensional silicon nanostructures to the diode-type sensor signifi cantly improves its characteristics. The rectification ratio increases from 161 to 1807, the response ups from 4.5 to 25, the sensitivity grows from 1.6 to 4.02 (%RH)–1, while the response time and recovery time are reduced from 85/90 to 25/30 s, the hysteresis value goes down from 75 to 16%, the signal deviation after cycling drops from 15to 3%, and the signal fluctuation during continuous device operation decreases from 17 to 15%.Conclusions. The results have shown that the use of a simple and cheap nanowire synthesis technology is effective to produce humidity sensors.