Boron-doped buried inverted pyramid Hall device

Abstract

This thesis presents a comprehensive study on the fabrication and characterization of a buried invertedpyramid Hall sensor realized using pure-boron LPCVD. Conventional inverted-pyramid Hall sensors typically suffer from high residual offset and elevated flicker noise, effects that are often attributed to charge trapping at the passivation surface. Introducing a buried sensing layer is an effective strategy to mitigate these surface-related disturbances.
Motivated by this concept, a p+ layer was integrated into the pyramid Hall sensor architecture. Pureboron LPCVD was employed to form the required ultra-shallow junction, taking advantage of the absence of channeling and transient-enhanced diffusion effects commonly observed in ion-implanted boron. To minimize interference from the junction field effect, the boron deposition process was modeled and simulated using Synopsys Sentaurus. Based on these results, a one-minute LPCVD boron process was implemented to form the p+–n junction above the active region.
The fabricated sensors exhibit an equivalent magnetic residual offset ranging from 7.5 μT to 710 μT, with the buried sensor showing a lower residual offset in most modes. The sensor demonstrates a thermal noise floor of approximately 1 μT/√Hz at a 1.26 V supply. Flicker-noise analysis using the Hooge model reveals that the buried inverted-pyramid Hall sensors exhibit a lower αH/N and a reduced corner frequency compared to conventional devices, indicating a possible improvement in low-frequency noise performance.