— 01 — MKS INSTRUMENTS HANDBOOK Section A — Semiconductor Device Physics, Materials and Fabrication 9/2017 © 2017 MKS Instruments, Inc. All rights reserved. Limit of Liability/Disclaimer of Warranty: The purpose of this book is to educate and should be used only as a general guide. The authors and publisher are providing this book and its contents on an “as is” basis and make no representations or warranties of any kind. Neither the authors nor the publisher shall be liable for any costs, damages and expenses whatsoever (including, without limitation, incidental, special and consequential damages) resulting from any use of or reliance on the information contained herein, whether based on warranty, contract, tort or any other legal theory, and whether or not they have been advised of the possibility of such damages. This document shall not be copied, reproduced, distributed or published, in whole or in part, without the prior written consent of MKS Instruments, Inc. 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MKS Instruments Handbook Semiconductor Devices and Process Technology by the Office of the CTO — 03 — MKS INSTRUMENTS HANDBOOK Section A — Semiconductor Device Physics, Materials and Fabrication This page intentionally left blank. — 04 — Acknowledgments MKS Instruments Handbook Semiconductor Devices and Process Technology by the Office of the CTO Office of the CTO Josh Ding, Ph.D., Chief Technology Officer, Flow Solutions Atul Gupta, Ph.D., Head of Technology, Plasma & Reactive Gas Solutions Jim Kafka, Ph.D., Chief Technology Officer, Lasers John TC Lee, Ph.D., Chief Operating Officer & Senior Vice President Aaron Radomski, Chief Technology Officer, Power Solutions Erik Saarmaa, J.D., Chief IP Counsel, Intellectual Property Eric Snyder, Vice President, Quality & Reliability Philip Sullivan, Ph.D., Fellow & Chief Technology Officer, Pressure & Vacuum Measurement Solutions Robin Swain, Ph.D., General Manager, Integrated Solutions Business Eric Taranto, Vice President Analytical & Control Solutions & Integrated Solutions Business Ruben Zadoyan, Ph.D., Chief Technology Officer, Newport Products Former CTO Members Gerardo Brucker, Ph.D., Chief Scientist, Pressure & Vacuum Measurement Solutions Steve Walther, Ph.D., former Chief Technology Officer, Plasma & Reactive Gas Solutions Kevin Wenzel, Ph.D., former Chief Technology Officer, Plasma & Reactive Gas Solutions Peter Zemek, Ph.D., former Chief Technology Officer, Process & Environmental Analysis Solutions Contributing Editors Shannon Whidden, TechLink Writers Group Tom K. Whidden, Ph.D., TechLink Writers Group Special Thanks Anne Devine, Graphic Designer Jane Lawlor, Senior Marketing Specialist, Creative Design MaryAnn Naddy, Senior Director, Corporate Marketing (retired) — e — MKS INSTRUMENTS HANDBOOK Foreword Semiconductor devices have become essential and ubiquitous parts of our everyday lives, and this has been enabled by an industry that has pursued a relentless reduction in cost per function for over 50 years. Today’s devices contain billions of transistors interconnected by kilometers of “wires,” yet all fitting in a fingernail-sized integrated circuit. These devices are enabled by manufacturing processes that continue to increase in complexity and require unprecedented innovation in physical structure, new materials, process control, and throughput. Some of the most important unit processes required to sustain this pace of innovation include Etching, Deposition, Lithography, Metrology, and Wet Cleaning. In turn, the improvements in these unit processes are dependent on critical subsystem technologies and instruments that measure, control and sustain pristine vacuum systems, deliver critical gases, reactive species, and power to these systems, and provide state-of-the-art laser, optics and photonics capabilities to define and measure sub-nanometer features. MKS Instruments uniquely serves this market with the broadest portfolio of solutions in the industry. The Semiconductor Devices and Process Technology handbook presents the fundamental device physics, materials, and fabrication processes used to manufacture semiconductors, as well as the technologies, instruments, and equipment that are used to monitor, control, and automate the fabrication processes. This handbook was initially conceived as training material for our employees. As it has evolved, we want to share it with you, our customers, suppliers, and partners in the semiconductor industry, with the hope that you will find it informative and of some value to your work. This handbook came about thanks to what we learned from working alongside you for over half a century. In that spirit, we welcome your feedback and input to future editions. There’s no denying that rapidly evolving technology will continue to shape and transform this industry in the years to come. MKS Instruments looks forward to facing the opportunities and challenges this will present—together. Gerald G. Colella Chief Executive Officer & President About MKS Instruments MKS Instruments, Inc. is a global provider of instruments, subsystems and process control solutions that measure, control, power, monitor, and analyze critical parameters of advanced manufacturing processes to improve process performance and productivity. Our products are derived from our core competencies in pressure measurement and control, flow measurement and control, gas and vapor delivery, gas composition analysis, residual gas analysis, leak detection, control technology, ozone generation and delivery, RF & DC power, reactive gas generation, vacuum technology, lasers, photonics, sub-micron positioning, vibration isolation, and optics. Our primary served markets include semiconductor capital equipment, general industrial, life sciences, and research. Additional information can be found at www.mksinst.com. — f — Table of Contents Table of Contents Section A - Semiconductor Device Physics, Materials and Fabrication . 1 I. Semiconductor Physics and Basic Device Structures . 3 A. Semiconductor Physics . 3 1. Electrical Characteristics of Solids . 3 2. Electrical Conduction in Semiconductors . 4 B. Basic Device Structures . 9 1. P-N Junction . 9 2. Diodes . 10 3. Bipolar Junction Transistor . 11 4. MOSFET . 12 5. FinFETs . 14 6. Other Common Semiconductor Devices . 15 II. Semiconductor Materials . 19 A. Bulk Crystalline Silicon and Compound Semiconductors . 19 1. Electronic Grade Polycrystalline Silicon (Polysilicon) . 19 2. Single Crystal Silicon Wafer Manufacture . 21 3. Compound Semiconductor Wafer Production . 23 B. Thin Films for Device Fabrication . 25 1. Polycrystalline Silicon Thin Films . 25 a. Overview . 25 b. Material and Electrical Properties . 25 c. Deposition of Polycrystalline Silicon Thin Films . 27 2. Epitaxial Thin Films . 31 a. Silicon Based Epitaxial Thin Films . 31 b. Compound Semiconductor Epitaxial Thin Films . 37 3. Dielectric Thin Films . 41 a. Silicon Dioxide . 41 b. Silicon Nitride . 48 c. High-k and Low-k Dielectrics . 49 d. Other Dielectrics . 50 — i — MKS INSTRUMENTS HANDBOOK 4. Metal Thin Films for Contacts and Interconnects . 52 a. Metal Materials Requirements . 52 b. Aluminum . 54 c. Tungsten . 56 d. Copper . 58 e. Barrier Layers . 60 III. Example Fabrication Process: CMOS Devices . 63 A. Wafer Surface Cleaning . 63 1. Contaminant Types and Solution Cleaning Methods . 65 a. Particles . 65 b. Metals . 65 c. Chemical Contamination . 66 B. CMOS Device Structure . 67 C. CMOS Process Steps . 69 1. Pad Oxide (Thermal Oxidation) . 69 2. Silicon Nitride . 69 3. Shallow Trench Isolation (STI) Process . 70 4. N- and P-Well Process . 71 5. Gate Process . 72 6. Contact Process . 72 Section B - Process Equipment, Technology, and MKS Instrument's Product Applications . 75 I. Vacuum Technology . 77 A. Basic Concepts . 77 B. Creating a Vacuum . 79 C. Measuring Vacuum . 85 D. Vacuum/Pressure Control . 98 E. Residual Gas Analysis . 104 II. Substrate Surface Cleaning . 109 A. Piranha, SC1, SC2, RCA and DHF . 109 B. “Dry” Substrate Cleaning . ..