Improvement of Fermi-Level Pinning and Contact Resistivity in Ti/Ge Contact Using Carbon Implantation.

Iksoo Park,Donghun Lee,Bo Jin,Jungsik Kim,Jeong-Soo Lee

doi:10.3390/mi13010108

Abstract

Effects of carbon implantation (C-imp) on the contact characteristics of Ti/Ge contact were investigated. The C-imp into Ti/Ge system was developed to reduce severe Fermi-level pinning (FLP) and to improve the thermal stability of Ti/Ge contact. The current density (J)-voltage (V) characteristics showed that the rectifying behavior of Ti/Ge contact into an Ohmic-like behavior with C-imp. The lowering of Schottky barrier height (SBH) indicated that the C-imp could mitigate FLP. In addition, it allows a lower specific contact resistivity (ρc) at the rapid thermal annealing (RTA) temperatures in a range of 450–600 °C. A secondary ion mass spectrometry (SIMS) showed that C-imp facilitates the dopant segregation at the interface. In addition, transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) mapping showed that after RTA at 600 °C, C-imp enhances the diffusion of Ge atoms into Ti layer at the interface of Ti/Ge. Thus, carbon implantation into Ge substrate can effectively reduce FLP and improve contact characteristics.

Highlights

As a channel material for the next-generation field-effect transistors (FETs), Germanium (Ge) is considered a promising alternative to silicon (Si) owing to its higher carrier mobility and the process compatibility with the advanced Si microfabrication
Ohmic-like behavior with relatively other hand, the Ti/Ge contact with Carbon implantation (C-imp) shows an Ohmic-like behavior with relatively high current under the reverse regime, alleviation of Fermi-level pinning (FLP)
Ti and forms the Ti-germanide during the rapid thermal annealing (RTA) process, which is beneficial to reduce the contact resistivity [14,15]. These results show that the C-imp is a promising approach to lower the contact resistivity in Ti/Ge contact by inducing the dopant segregation and Ge diffusion into the Ti layer

Summary

Introduction

As a channel material for the next-generation field-effect transistors (FETs), Germanium (Ge) is considered a promising alternative to silicon (Si) owing to its higher carrier mobility and the process compatibility with the advanced Si microfabrication. The formation of metal germanide can be another approach because the MIGS from metal dangling bond states in germanide can lead to an FLP reduction [14,15]. Ion implantation is another approach to achieving low ρc and suppressing dopantdiffusion behaviors. We investigated the effects of C-imp on the FLP reduction of a Ti/Ge contact and the related contact characteristics. Physical and structural properties of Ti/Ge contact with C-imp were anausing scanning electron microscopy (SEM), transmission electron microscopy (TEM), eleclyzed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), tron energy loss spectroscopy (EELS), and secondary ion mass spectrometry (SIMS). Electron energy loss spectroscopy (EELS), and secondary ion mass spectrometry (SIMS)

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