Hydrogen Passivation Effects on Spatially Resolved Charge Trap Densities in Si(100)-SiO$_2$

TL;DR

This study uses frequency-modulated atomic force microscopy to spatially resolve and quantify charge traps at the Si-SiO2 interface, demonstrating hydrogen passivation reduces trap density and improves nanoscale device performance.

Contribution

It introduces a method to detect individual traps and shows hydrogen termination further decreases donor-like trap densities in Si(100)-SiO2.

Findings

Hydrogen passivation reduces charge trap densities.

fm-AFM enables spatial mapping of individual traps.

Hydrogen-terminated samples show fewer donor-like traps.

Abstract

As silicon-based devices continue to shrink to the nanoscale, traps at the Si-SiO$_2$ interface pose increasing challenges to device performance. These traps reduce channel carrier mobility and shift threshold voltages in integrated circuits, and introduce charge noise in quantum systems, reducing their coherence times. Knowledge of the precise location of such traps aids in understanding their influence on device performance. In this work, we demonstrate that frequency-modulated atomic force microscopy (fm-AFM) allows the detection of individual traps. We use this to study how sample preparation, specifically the introduction of a buried hydrogen termination layer, and post-processing annealing in forming gas (N$_2$+H$_2$), affects the density of donor-like traps in Si(100)-SiO$_2$ systems. We spatially map and quantify traps in both conventionally prepared ("pristine") silicon samples and those processed under ultra-high vacuum for hydrogen resist lithography (HRL). We confirm previous studies demonstrating hydrogen passivation of traps and find that hydrogen termination further reduces the donor-like trap density. We also observe a significant reduction in two-level donor-like traps in the hydrogen-terminated samples compared to pristine silicon samples. These findings suggest that HRL-prepared silicon may offer advantages for high-performance nanoscale and atomic-scale devices due to reduced trap densities.