Effects of Temperature, Thickness and Bias Current on Magnetoelectric Characteristics of Silicon Micro-Hall Sensors

A quest for a quantitative and noninvasive method for the measurement of local magnetic fields with high spatial and field resolution at variable temperatures calls for a selection of suitable magnetic sensor and appropriate scanning system. Scanning Hall probe microscopy (SHPM) is one of the choices as it addresses the stated issues and complements the other magnetic imaging methods. Compatibility of Si-Hall sensor fabrication with standard CMOS fabrication process and controllability of silicon characteristics parameters make them more suitable, for Hall probe applications, over other compound semiconductors (AlGaAs/GaAs, InSb, and AlGaN/GaN). However, the effect of Si-Hall sensor's device thickness, applied bias current, and impediments in its use at variable temperatures SHPM application need to be investigated. In this article, a systematic study on the optimization of performance parameters of silicon-on-insulator micro-Hall sensors for their dedicated application in SHPM system is presented. Si similar to 0.7 mu m x 0.7 mu m Hall sensors have been fabricated using monolithic device fabrication steps. These Hall sensors have been investigated based on the electrical, magnetic and noise characteristics to study the effect of thickness of the active layer (300-550 nm) and temperature (25-150 degrees C). Formation of trapping centers and defects have been observed due to device layer thinning, which not only limit the working temperature, bias current but also the minimum thickness of the device layer to be 300 nm. This compromise in Si-Hall sensor characteristics due to surface morphology of thinned films can be removed by growing the device layer on SiO2 instead of thinning the device layer.