Modulation of sub-threshold properties of InGaAs MOSFETs by La2O3 gate dielectrics

C.-Y Chang,S Takagi,K Kato,K Endo,M Takenaka

doi:10.1063/1.4999958

Abstract

We have found the ferroelectric-like characteristics in atomic layer deposition (ALD) La2O3 films with thermal budget lower than 300oC in polarization-electric field (P-E) and capacitance-gate voltage (C-V) measurements on W/La2O3/W and W/La2O3/InGaAs capacitors. The observed hysteresis and saturation of polarization in the P-E characteristics of the W/La2O3/W and the W/La2O3/InGaAs capacitors, and the counter-clockwise C-V hysteresis in the C-V curves of the W/La2O3/InGaAs capacitors suggest a possibility of ferroelectricity in the present La2O3 films. By using this gate stack, W/La2O3/InGaAs metal-oxide-semiconductor field-effect transistors (MOSFETs) were fabricated in order to examine the negative capacitance (NC) effect due to La2O3. It is found that the sub-threshold swing (SS) of W/La2O3/InGaAs MOSFETs is lower at low temperature than the theoretical limit of MOSFETs. This result strongly suggests that the W/La2O3/InGaAs MOSFETs can work as a steep-slope III-V negative capacitance field-effect transistor (NCFET).

Highlights

A considerable attention has been paid to developing NCFETs for realizing a steep-slope transistor with SS below the limitation of conventional MOSFETs.[1,2] Here, this limitation amounts to 2.3 · or 60 mV/decade at room temperature (RT), where k is the Boltzmann constant, T is temperature and q is the elementary charge
We have found that the another high-k dielectric, La2O3, which can be a candidate for gate dielectrics compatible with the CMOS technology, have ferroelectric-like characteristics under low thermal budget, which is very suitable for NCFET applications on III-V semiconductors
The saturation of polarization and the squareshaped hysteresis loops are observed more clearly at 150K, as shown in Fig. 1 (b) and Fig. 2 (b), which seems consistent with the typical ferroelectric characteristics accompanying the phase transition

Summary

Introduction

A considerable attention has been paid to developing NCFETs for realizing a steep-slope transistor with SS below the limitation of conventional MOSFETs.[1,2] Here, this limitation amounts to 2.3 · (kT /q) or 60 mV/decade at room temperature (RT), where k is the Boltzmann constant, T is temperature and q is the elementary charge. The steep-slope NCFET is expected to be realized by replacing ordinary (paraelectric) gate dielectrics in conventional MOSFETs with ferroelectric gate dielectrics. We have found that the another high-k dielectric, La2O3, which can be a candidate for gate dielectrics compatible with the CMOS technology, have ferroelectric-like characteristics under low thermal budget, which is very suitable for NCFET applications on III-V semiconductors. We have applied this ferroelectric-like La2O3 to the gate insulator for InGaAs and have realized InGaAs MOSFET operation. The steep-slope properties have been experimentally demonstrated in this La2O3/InGaAs MOSFET, suggesting the NCFET operation on III-V semiconductor channels

Methods

Results

Conclusion