Low Temperature Plasma Etching Control through Ion Energy Angular Distribution and 3 ...

271 Pages·2015·15.18 MB·English

by  Yiting Zhang

Low Temperature Plasma Etching Control through Ion Energy
Angular Distribution and 3-Dimensional Profile Simulation

by
Yiting Zhang

A dissertation submitted in partial fulfillment
of the requirements for the degree of
Doctor of Philosophy
(Electrical Engineering)
in the University of Michigan
2015

Doctoral Committee:
Professor Mark J. Kushner, Chair
Associate Professor John E. Foster
Professor Brian E. Gilchrist
Professor Yogesh B. Gianchandani
Associate Professor Steven C. Shannon, North Carolina State University
Professor Fred L. Terry, Jr
Copyright © Yiting Zhang 2015
All rights reserved
DEDICATION
To my parents, Shuiping Zhang 张水平 and Meijuan Shao 邵梅娟.

“谁言寸草心，
报得三春晖。”

-唐·盂郊《游子吟》
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ACKNOWLEDGEMENTS
I would like to express my great appreciation to my research supervisor, Prof. Mark J.
Kushner, for guiding me through my plasma journey. His patient guidance, encouragement and
insightful critiques of research have been extremely instrumental in increasing my knowledge of
plasma physics. I would also like to thank him for providing me numerous opportunities and
valuable advice at every step of the way. I would like to offer my special thanks to the members
of my committee- Prof. John Foster, Prof. Brian Gilchrist, Prof. Yogesh Gianchandani, Prof.
Steven Shannon and Prof. Fred Terry for their thoughtful comments and suggestions.
I am also grateful to all my fellow group members through the years- Dr. Julia
Falkovitch-Khain, Dr. Zhongmin Xiong, Dr. Natalia Yu. Babaeva, Dr. Yang Yang, Dr. Mingmei
Wang, Dr. Juline Shoeb, Dr. Sang-Heon Song, Dr. Jun-Chieh Wang, Dr. Michael D. Logue, Dr.
Aram H. Markosyan, Wei Tian, Seth Norberg, Peng Tian, Shuo Huang, Amanda Lietz and
Chenhui Qu. I would like to thank Dr. Elizabeth Hildinger and Thara Visvanathan for
proofreading this dissertation. I would like to acknowledge the staff of the Electrical
Engineering and Rackham Graduate School at the University of Michigan for helping me with
scheduling and paperwork through my defense.
I would like to thank the following collaborated groups for their support in experiment
measurements: Prof. Walter Gekelman, Nathaniel B. Moore and Patrick Pribyl in Department of
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Physics and Astronomy at University of California - Los Angeles, David Coumou from MKS
instruments, Abdullah Zafar in Nuclear Engineering at North Carolina State University and Dr.
Alex Paterson, Dr. John Holland, Dr. Saravanapriyan Sriraman, Dr. Alexi Marakhtanov, Dr.
Tom Kamp from Lam Research.
My special thanks to all my friends in Ann Arbor who made my life in graduate school
enjoyable. Without them, I could not have survived the long, cold and harsh winters in Michigan.
Finally, I would like to thank my beloved parents, grandparents and relatives for their support
and encouragement throughout my many years of study abroad. I am deeply grateful to them for
their love.
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Table of Contents
DEDICATION .............................................................................................................................. ii
ACKNOWLEDGEMENTS ........................................................................................................ iii
List of Figures ............................................................................................................................... ix
List of Appendices ...................................................................................................................... xix
List of Acronyms ......................................................................................................................... xx
ABSTRACT ................................................................................................................................ xxi
Chapter 1 INTRODUCTION ...................................................................................................... 1
1.1 An Introduction to Low Temperature Plasma in Semiconductor Fabrication ................. 1
1.2 Plasma Sources ................................................................................................................. 3
1.3 Control and Customization of Ion Energy Distributions ................................................. 6
1.4 Modeling of Low Temperature Plasma ............................................................................ 9
1.5 Plasma Experimental Diagnostics .................................................................................. 12
1.6 Summary ........................................................................................................................ 15
1.7 Figures ............................................................................................................................ 18
1.8 References ...................................................................................................................... 29
Chapter 2 HYBRID PLASMA EQUIPMENT MODEL ......................................................... 32
2.1 Introduction .................................................................................................................... 32
2.2 The Electromagnetics Module (EMM) .......................................................................... 33
2.3 The Electron Energy Transport Model (EETM) ............................................................ 35
2.3.1 The Electron Monte Carlo Simulation (eMCS) ...................................................... 35
2.4 The Fluid Kinetics-Poisson Module (FKPM) ................................................................ 37
2.4.1 Continuity and energy equation for electrons ......................................................... 37
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2.4.2 Continuity, momentum and equation equations for heavy particles....................... 39
2.4.3 Poisson’s equation .................................................................................................. 39
2.5 Plasma Chemistry Monte Carlo Module (PCMCM)...................................................... 43
2.6 Figure ............................................................................................................................. 47
2.7 References ...................................................................................................................... 48
Chapter 3 MONTE CARLO FEATURE PROFILE MODEL ............................................... 49
3.1 Introduction .................................................................................................................... 49
3.2 Description of the Model................................................................................................ 51
3.2.1 Particle Initialization and Motion ........................................................................... 51
3.2.2 Energetic Particle Surface Interaction .................................................................... 54
3.3 Surface Reaction Mechanisms ....................................................................................... 56
3.4 Three-Dimensional Monte Carlo Feature Profile Model (MCFPM 3-d) ....................... 58
3.4.1 3-d Mesh Generation............................................................................................... 59
3.4.2 3-d Surface Advancement ....................................................................................... 59
3.5 Figures ............................................................................................................................ 63
3.6 References ...................................................................................................................... 71
Chapter 4 SPACE AND PHASE RESOLVED ION ENERGY AND ANGULAR
DISTRIBUTIONS IN SINGLE- AND DUAL-FREQUENCY CAPACITIVELY COUPLED
PLASMAS ................................................................................................................................... 72
4.1 Introduction .................................................................................................................... 72
4.2 Description of the Model................................................................................................ 74
4.3 Plasma Properties in an ICP Reactor with a Single Frequency rf Biased Substrate ...... 75
4.3.1 IEADs with a Single LF .......................................................................................... 76
4.3.2 IEADs with a Single HF ......................................................................................... 81
4.3.3 Comparison to Experiment ..................................................................................... 83
4.3.4 Dual Frequency IEADs ........................................................................................... 85
4.4 Concluding Remarks ...................................................................................................... 89
4.5 Figures ............................................................................................................................ 91
4.6 References .................................................................................................................... 115
Chapter 5 CONTROL OF ION ENERGY AND ANGULAR DISTRIBUTIONS IN DUAL-
FREQUENCY CAPACITVIELY COUPLED PLASMAS THROUGH POWER RATIOS
AND PHASES ........................................................................................................................... 116
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5.1 Introduction .................................................................................................................. 116
5.2 Description of the model .............................................................................................. 118
5.3 Plasma Properties in DF-CCP ...................................................................................... 118
5.3.1 Control of IEDs with Ratio of the HF/LF Power .................................................. 123
5.3.2 Etching SiO with Power Adjusted Ar/CF /O Gas Mixture in DF-CCPs ........... 126
2 4 2
5.4 Control of IEDs in DF-CCP with Phase Shifting ......................................................... 131
5.5 Concluding Remarks .................................................................................................... 134
5.6 Figures .......................................................................................................................... 136
5.7 References .................................................................................................................... 157
Chapter 6 CONTROL OF ION ENERGY DISTRIBUTION USING PHASE SHIFTING
IN MULTI-FREQUENCY CAPACITIVELY COUPLED PLASMAS .............................. 158
6.1 Introduction .................................................................................................................. 158
6.2 Description of Models and Experiment ....................................................................... 161
6.3 Plasma properties and IEDs in a dual- frequency CCP reactor ................................... 164
6.4 Plasma properties and IED in a triple- frequency CCP reactor .................................. 173
S
6.5 Concluding Remarks .................................................................................................... 178
6.6 Figures .......................................................................................................................... 180
6.7 References .................................................................................................................... 198
Chapter 7 COMPUTATIONAL INVESTIGATION OF ION KINETICS IN PLASMA 3-
DIMENSIONAL FEATURE ETCHING ............................................................................... 199
7.1 Introduction .................................................................................................................. 199
7.2 Description of Models .................................................................................................. 202
7.3 Model Validation.......................................................................................................... 203
7.4 Predicted profiles and discussion ................................................................................. 205
7.4.1 3-d Pattern Etching ............................................................................................... 206
7.4.2 Aspect Ratio Dependent Etching .......................................................................... 209
7.4.3 Circular Via Etching ............................................................................................. 210
7.5 Concluding Remarks .................................................................................................... 212
7.6 Figures .......................................................................................................................... 215
7.7 References .................................................................................................................... 228
Chapter 8 CONCLUSION AND FUTURE WORK .............................................................. 230
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8.1 Overview of Research .................................................................................................. 230
8.2 Future Work ................................................................................................................. 233
8.3 References .................................................................................................................... 236
Appendices……………………………………………………………………………………..237

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List of Figures
Fig. 1.1. Electron temperature and density of natural and manmade plasma.[3] ......................... 18
Fig. 1.2. Ion-assisted gas-surface chemistry using Ar+ +XeF on silicon. [6] .............................. 19
2
Fig. 1.3. Illustration of wet etching limitation and anisotropic dry etching. ................................ 20
Fig. 1.4. Plasma rf sources: a) Capacitively Coupled Plasma and b) Inductively Coupled Plasma
with cylinder coil antenna. ............................................................................................................ 21
Fig. 1.5. a) IEDs from Tsui[64] for different values of a ( / )2. The unexpected
i rf ion
disappearance of the low-energy peak at higher a1 is due to Tsui's assumption of constant sheath
width.[23] b) PDP1 Modeled results from Kawamura et al.[23] showing IEDs of He+ at bias
frequencies from 1 MHz to 100 MHz. c) Experiments and d) simulation for IEDs of Ar+ and O +
2
from Liu et al.[32] ........................................................................................................................ 22
Fig. 1.6. Space and phase resolved optical emission measured by Gans et al.[17] The produced
electron dynamics exhibits a strong coupling of both 2 and 27 MHz. The emission maxima
indicated as 2 and 2’ scale with the 2 MHz power relative to the 27 MHz power while the
maxima indicated as 27 and 27’ scale vice versa. ........................................................................ 23
Fig. 1.7. Mean electron energy at four times in the rf period and period average ionization
profile from a) the PIC model and b) the fluid model.[43] ........................................................... 24
Fig. 1.8. Surface normal is determined at the interaction of particle tractor and fitted polynomial
surface. Slight difference in the intersection results in different angles of incidence.[50] ......... 25
Fig. 1.9. a) Device structure of FinFet, which has a double gate structure. b) Top view and tilted
view SEM pictures of gate double pattering in sub 0.1 um2 FinFET 6T-SRAM.[52] ................. 26
Fig. 1.10. LIF schematic: The laser beam passes through a quartz vacuum window on the top of
the chamber and strikes the wafer at normal incidence to measure z component of the ion
velocity distribution.[59] .............................................................................................................. 27
Fig. 1.11. a) Schematic of the retarding field energy analyzer structure. b) An example of
normalized IEDs for various 2 MHz rf bias potentials measured by the RFEA.[63] ................... 28
Fig. 2.1. Flow chart of modules information exchange used for this thesis. ................................ 47
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