Monitoring and Control of Semiconductor Manufacturing Using Acoustic Techniques

143 Pages·2003·0.83 MB·English

Monitoring and Control of Semiconductor Manufacturing Using
Acoustic Techniques

A Thesis
Presented to
The Academic Faculty

By

Frances R. Williams

In Partial Fulfillment
of the Requirements for the Degree
Doctor of Philosophy in the
School of Electrical and Computer Engineering

Georgia Institute of Technology
November 2003
Monitoring and Control of Semiconductor Manufacturing Using
Acoustic Techniques

Approved by:

Dr. Gary S. May, Advisor

Dr. Mark G. Allen

Dr. Farrokh Ayazi

Dr. Peter J. Hesketh

Dr. William D. Hunt

Date Approved November 25, 2003

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This thesis is dedicated to my parents for the many sacrifices they made throughout the
years to ensure this day would come to pass.

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ACKNOWLEDGEMENTS

To God be the glory for the things He has done. I would like to thank you God for
the gift of Life through Your Son Jesus and for the daily guidance and strength to strive
and endure. Thank you for this journey You have brought me through while in Atlanta.
It has not only developed me and revealed to me who I am, but it has shown me just how
awesome and great You are. I am humbled to be Your child. I will praise You all my
days!
To my parents, I love you very much and thank you for all of the encouragement,
support, and many (MANY) prayers. You knew I could when I didn’t. To my siblings,
thank you all for being such wonderful and supportive siblings. You all are the wind
beneath my wings.
I give special thanks to my advisor, Dr. Gary S. May, for his support and guidance
throughout my studies at Georgia Tech. He supported and believed in my efforts even
when I was frustrated with my research and has served as a source of inspiration,
encouragement, and professional guidance. Thus, I am a better researcher, teacher,
mentor, and person. I would also like to thank Dr. Mark Allen and Dr. William Hunt for
serving on my reading committee. A sincere thanks is also extended to the other
members of my defense committee, Dr. Farrokh Ayazi and Dr. Peter Hesketh.
I am also grateful to Yong Kyu Yoon, Shawn Pinkett, Seong-O Choi, Jin-Woo Park,
Gregory Triplett, Terence Brown, and Pam Jackson who contributed to my research
endeavors. I would also like to thank Mrs. Laureen Rose, Mr. Gary Spinner, and the
other MiRC staff whose assistance helped facilitate the processing of my device. Special
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thanks to the Intelligent Semiconductor Manufacturing research group for their support
and friendship. I would also like to thank Ameisha Sampson for her editing assistance.
I would be remiss if I did not mention all of the wonderful friends and associates I
have met while at Georgia Tech. Your friendship, prayers, support, and encouragement
have carried me through my time at Tech. I would especially like to thank Vanessa Hall,
Charima Young, Lavinna King, Avalon Blenman, and Kendra Taylor. Special thanks to
the MiRC crew: Cleon Davis, Gregory Triplett, Terence Brown, and Demetris Geddis. I
cannot forget all of my friends who have been there for me since my days at A&T (and
some since high school): Tameka Paschal, Nikki Darden, Tanja Darden, Fonda
Daughtery, and Kim Rains. I would also like to thank my New Birth Cathedral church
family and the 7th Day Dance Ministry—I’m going to really miss you all!

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Table of Contents

Dedication iii
Acknowledgements iv
List of Tables ix
List of Figures x
Summary xiii
Chapter 1. Introduction 1
1.1. Process Monitoring in Semiconductor Manufacturing 3
1.2. Motivation for Thesis Work 5
1.2.1. Acoustic Sensing 5
1.2.2. Electrochemical Deposition 6
1.2.3. Research Objectives 8
1.3. Thesis Organization 9
Chapter 2. Review of Existing In-Situ Process Monitoring Techniques 10
2.1. Optical-Based Sensors 10
2.1.1. Optical Emission Spectroscopy 11
2.1.2. Interferometry 13
2.1.3. Spectroscopic Ellipsometry 15
2.1.4. Optical Pyrometry 17
2.2. Acoustic Sensors 19
2.2.1. Acoustic Wave Devices 19
2.2.1.1.Types 22
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2.2.1.2.Parameter Sensitivity 25
2.2.2. Silicon Microphones 26
2.2.2.1.Types 27
2.2.2.2.Parameter Sensitivity 33
2.2.3. Acoustic Sensors in Semiconductor Process 33
Manufacturing

2.3. Summary 35
Chapter 3. A Piezoelectric Sensor for Process Monitoring 37
3.1. Sensor Theory and Operation 37
3.2. Piezoelectric Materials 43
3.3. Circuit Model 46
3.4. Summary 50
Chapter 4. Fabrication Process 51
4.1. Sensor Design 51
4.2. Micromachining 55
4.3. Emulsion Plating 57
4.4. Process Sequence 59
Chapter 5. Sensor Response and Measurement 64
5.1. Theory of Thin Plates 64
5.2. Theoretical Sensitivity Calculations 67
5.3. Experimental Results 73
5.3.1. Test Set-up 73
5.3.2. Results 75
5.4. Comparison 75
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5.5. Summary 77
Chapter 6. Monitoring Electrochemical Deposition Using the
Acoustic Sensor 79
6.1. Electroplating Mechanism 81
6.2. Nickel-Iron Plating 88
6.3. The Propagation of Sound in Fluids 89
6.4. Plating Set-Up 91
6.5. Predictive Model for Metallization 96
Chapter 7. Conclusion 105
7.1. Summary of Contributions 106
7.2. Future Work 109
Appendix A Time Delay Experiments 112
Appendix B Statistical Model Results 121
References 122
Vita 129

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List of Tables

Table 1 Parameters to be measured 3
Table 2 Piezoelectric constitutive equations and definitions
of piezoelectric parameters 44

Table 3 Composition of Ni-Fe electroplating solution 88

Table 4 Time delay measurements 114

Table 5 Salt molarity and time delay data 115

Table 6 ANOVA table for response thickness T 121

Table 7 Least squares coefficients for regression model 121

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List of Figures

Figure 1 OES system set-up 12
Figure 2 Characteristic plasma emissions 12
Figure 3 Physical principle of interferometry 14
Figure 4 Basic geometry of Ellipsometry measurements 16
Figure 5 IDT design 21
Figure 6 Acoustic wave device structure 23
Figure 7 Capacitive microphone 28
Figure 8 Piezoresistive microphone 30
Figure 9 Position of piezoresistors on microphone membrane 30
Figure 10 Piezoelectric microphone 31
Figure 11 Optical-waveguide microphone 32
Figure 12 Simple piezoelectric structure 38
Figure 13 Piezoelectric effect in quartz 39
Figure 14 Sensor equivalent circuits 47
Figure 15 Sensor circuit employing a charge amplifier 48
Figure 16 Cross-sectional view of piezoelectric acoustic sensor 53
Figure 17 ANSYS plot of stress in x-direction 53
Figure 18 Electrode pattern 54
Figure 19 Piezoelectric response 55
Figure 20 Pyroelectric response 55
Figure 21 Mask layout 58
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