An Introduction to Contact Resistance

188 Pages·2020·10.441 MB·English

by  Zuoguang Liu

MATERIALS SCIENCE AND TECHNOLOGIES

A I
N NTRODUCTION TO
CONTACT RESISTANCE

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MATERIALS SCIENCE AND TECHNOLOGIES

A I
N NTRODUCTION TO
CONTACT RESISTANCE

ZUOGUANG LIU
EDITOR
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Library of Congress Cataloging-in-Publication Data

ISBN: 978-1-53618-501-0
Names: Liu, Zuoguang, editor.
Title: An introduction to contact resistance / Zuoguang Liu (editor).
Description: New York : Nova Science Publishers, Inc., [2020] | Series:
Materials science and technologies | Includes bibliographical references
and index. |
Identifiers: LCCN 2020038446 (print) | LCCN 2020038447 (ebook) | ISBN
9781536185010 (paperback) | ISBN 9781536185836 (adobe pdf)
Subjects: LCSH: Semiconductor-metal boundaries. | Electric contacts. |
Electric resistance.
Classification: LCC TK7872.C68 I58 2020 (print) | LCC TK7872.C68 (ebook)
| DDC 621.3815/2--dc23
LC record available at https://lccn.loc.gov/2020038446
LC ebook record available at https://lccn.loc.gov/2020038447

Published by Nova Science Publishers, Inc. † New York
CONTENTS

Preface vii
Chapter 1 Introduction to Semiconductor
Transistor Resistances 1
Zuoguang Liu
Chapter 2 Physics and Materials
of Semiconductor-Metal Contacts 25
Zuoguang Liu and Nicolas Breil
Chapter 3 Electrical Characterization of Contact Resistance 51
Zuoguang Liu
Chapter 4 Contact Resistance Reduction Approaches 79
Heng Wu
Chapter 5 Meta-Stable Alloys for Ultra-Low
Contact Resistance 101
Zuoguang Liu and Heng Wu
Chapter 6 Low-Resistance Contact Integration
in CMOS Technology 123
Heng Wu
vi Contents
Chapter 7 Contact Engineering of Two-Dimensional
Transition Metal Dichalcogenides 137
Zhihui Cheng and Aaron D. Franklin
About the Editor 167
Index 169
PREFACE

Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) has
been the fundamental building block in integrated circuits (IC) over the
past fifty years. Performance of the MOSFET is increased in each
technology node according to the famous Moore’s Law. In the 1970s to
1990s, performance gain was mainly from the reduction of transistor gate
length, thus charge carriers could travel a shorter distance for fast
switching and high drive current. In the 1990s to 2000s, scaling the
thickness of gate oxide SiO was the focus in performance step-up as
2
higher gate capacitance with thinner oxide brings more drive current at the
same operating voltages. Around end of the 2000s, scaling the SiO
2
reached its limit, and high-K oxide replaced SiO to continue the Moore’s
2
Law. As the MOSFETs become smaller and smaller, device parasitics start
to dominate the performance since 22nm node in the 2010s. The resistance
part in the MOSFET RC delay is mainly from external components
particularly the source/drain contact. This is quite unexpected by a lot of
semiconductor community who was betting on high mobility channels and
carbon-based devices for future logic technology because those exotic
devices all try to address device internal components rather than the
external. In the past decade, 3-D MOSFETs, also named FinFETs, became
the leading technology device structure, and it brings a unique opportunity
viii Zuoguang Liu
for the contact resistance engineering. Among the device performance
elements, contact resistance surpasses gate dielectrics, SiGe channel, and
low-k materials in major semiconductor forums and journals in the past
five years.
MOSFET contact resistance is both an old and new topic. It is old
because principles of the MOSFETs are well established since the early
1960s, and even earlier than the MOSFETs are the fundamentals of
semiconductor-metal contacts which were established in the 1930s. In
Chapter 1, we will go over basic device physics of modern MOSFETs with
focus on the resistance components. Chapter 2 introduces Schottky-type
and ohmic-type semiconductor-metal contacts. This is to provide
background for the contact resistance topics in the following chapters. The
new knowledge is on material and integration aspects for contact resistance
reduction. Chapter 2 also discusses the contact metal, semiconductor
substrate, and silicide materials for a low contact resistivity. Chapter 3
introduces the test structures and measurements of contact resistance, and
explains how to calibrate the contact resistivity. Chapter 4 and Chapter 5
discuss the approaches for contact resistance reduction. State-of-the-art
process techniques and material engineering are introduced. Integration of
the contact resistance reduction into CMOS FinFET flow is presented in
Chapter 6. Beside standard Si-based CMOS technology, 2-D devices based
on transition metal dichalcogenides (TMDs) have attracted a lot of
attention in recent years for energy storage, photonics, and sensors.
However, the metal-2D contacts suffer from high resistance, which limits
the 2-D devices in product application. As an expansion in this book, we
introduce the 2-D TMDs and important aspects of their contact interface
engineering in Chapter 7.
The authors acknowledge IBM Research where the Si CMOS related
content in this book is conducted. We thank Dr. O. Gluschenkov, for his
guidance in the CMOS contact resistance work with his deep knowledge in
thermal process, SPE, and LPE. I would like to acknowledge my doctoral
advisor Professor T.P. Ma for his academic guidance; my colleagues in
IBM for research and career support: Drs. H. Bu, T. Yamashita, D.C. Guo,