Reducing Graphene Device Variability with Yttrium Sacrificial Layers

TL;DR

This study demonstrates that using yttrium sacrificial layers during graphene device fabrication significantly reduces variability, improves yield and performance, and simplifies large-scale manufacturing by minimizing contamination and damage.

Contribution

The paper introduces yttrium sacrificial layers as an effective method to enhance uniformity and performance in graphene transistors, addressing key variability issues in large-scale production.

Findings

Yield increased from 73% to 97%.

Mobility improved threefold.

Contact resistance reduced by 58%.

Abstract

Graphene technology has made great strides since the material was isolated more than a decade ago. However, despite improvements in growth quality and numerous 'hero' devices, challenges of uniformity remain, restricting large-scale development of graphene-based technologies. Here we investigate and reduce the variability of graphene transistors by studying the effects of contact metals (with and without Ti layer), resist, and yttrium (Y) sacrificial layers during the fabrication of hundreds of devices. We find that with optical photolithography, residual resist and process contamination is unavoidable, ultimately limiting device performance and yield. However, using Y sacrificial layers to isolate the graphene from processing conditions improves the yield (from 73% to 97%), average device performance (three-fold increase of mobility, 58% lower contact resistance), and the device-to-device variability (standard deviation of Dirac voltage reduced by 20%). In contrast to other sacrificial layer techniques, removal of the Y sacrificial layer with HCl does not harm surrounding materials, simplifying large-scale graphene fabrication.