am7b00538_si_001.pdf (4.84 MB)
Uniform Growth of Sub-5-Nanometer High‑κ Dielectrics on MoS2 Using Plasma-Enhanced Atomic Layer Deposition
journal contribution
posted on 2017-06-27, 00:13 authored by Katherine
M. Price, Kirstin E. Schauble, Felicia A. McGuire, Damon B. Farmer, Aaron D. FranklinRegardless of the
application, MoS2 requires encapsulation
or passivation with a high-quality dielectric, whether as an integral
aspect of the device (as with top-gated field-effect transistors (FETs))
or for protection from ambient conditions. However, the chemically
inert surface of MoS2 prevents uniform growth of a dielectric
film using atomic layer deposition (ALD)the most controlled
synthesis technique. In this work, we show that a plasma-enhanced
ALD (PEALD) process, compared to traditional thermal ALD, substantially
improves nucleation on MoS2 without hampering its electrical
performance, and enables uniform growth of high-κ dielectrics
to sub-5 nm thicknesses. Substrate-gated MoS2 FETs were
studied before/after ALD and PEALD of Al2O3 and
HfO2, indicating the impact of various growth conditions
on MoS2 properties, with PEALD of HfO2 proving
to be most favorable. Top-gated FETs with high-κ films as thin
as ∼3.5 nm yielded robust performance with low leakage current
and strong gate control. Mechanisms for the dramatic nucleation improvement
and impact of PEALD on the MoS2 crystal structure were
explored by X-ray photoelectron spectroscopy (XPS). In addition to
providing a detailed analysis of the benefits of PEALD versus ALD
on MoS2, this work reveals a straightforward approach for
realizing ultrathin films of device-quality high-κ dielectrics
on 2D crystals without the use of additional nucleation layers or
damage to the electrical performance.