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Atomic Layer Deposition of Metal, Metal Oxide, and Metal Carbide Thin Films

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Atomic Layer Deposition of Metal, Metal Oxide, and Metal Carbide Thin Films ABSTRACT STEVENS, ERIC CHRISTOPHER. From Novel Processes to Industrially Relevant Applications: Atomic Layer Deposition of Metal, Metal Oxide, and Metal Carbide Thin Films. (Under the direction of Dr. Gregory N. Parsons). The demand for faster electronic devices with better storage capacity, all without being prohibitively expensive, requires innovations in process design and chemistry. Atomic layer deposition (ALD) is one such process which allows for thin films of material to be deposited with sub-nanometer thickness control. ALD relies on self-limiting chemical reactions, which leads to uniform, pin-hole free, and conformal coatings on substrates with complex and three-dimensional architectures. We investigated a novel ALD process for the deposition of tin (Sn) metal using a vapor phase reducing agent and a metal halide precursor. This study marked the first thermal (i.e., without plasma) ALD process for elemental Sn, where the mechanism and growth properties as a function of temperature were studied using in situ methods. Sn metal films have a broad range of applications from nanowire transistors to anode materials for lithium ion batteries. In a similar fashion, we also studied the use of a novel ALD precursor, tungsten (V) chloride, to deposit tungsten carbide (WC) thin films, using trimethyl aluminum as a co-reagent. In situ studies revealed key information regarding the likely reaction pathways as well as saturation behavior at different temperatures. The deposited WC films were doped with aluminum and had low Cl impurities. WC films have many applications in the semiconductor industry due to their chemical stability, hardness, and high conductivity. We also investigated area-selective ALD of metal oxide and metal nitride materials on amorphous carbon (aC) substrates, deposited on 300 mm silicon wafers, for use in advanced patterning applications. Without any treatment to as-formed aC substrates, uninhibited ALD growth of titanium oxide (TiO2), hafnium oxide (HfO2), and titanium nitride (TiN) was observed. The use of a hydrogen plasma pretreatment on aC removed oxygen species and passivated the surface with C-H groups, leading to a nucleation delay for TiO2, HfO2, and TiN. We showed that the use of water as a co-reagent in metal oxide ALD leads to significant nucleation site generation, while the ammonia co-reagent in TiN ALD resulted in enhanced selectivity. We applied two different models to describe the nucleation behavior of metal oxide and metal nitride ALD on plasma-treated aC. The best fit of the experimental data was obtained using a modification based on the Avrami Equation, which assumed random dispersion of nucleation sites on the surface increasing at some rate. The insights gained from the model fit show that water plays a key role in the generation of new nucleation sites for metal oxide ALD. This model can be applied to other ALD processes to gain valuable information regarding the nucleation behavior as well as potential selectivity losses. We demonstrated the use of plasma pre-treatments to selectively deactivate aC lines in a sub-50 nm aC/Si3N4 line/space patterned structure on 300 mm substrates. ALD films of TiN and TiO2 were deposited on Si3N4 spaces, with particle formation on aC lines. Nucleation density was observed to be greater on the tops and corners of aC lines, implying optimization in the pattern formation is needed to realize maximum selectivity. Furthermore, aC lines were selectively removed using oxygen plasma to give sub-50 nm patterned lines TiN on Si3N4. Post-process cleans steps are likely to remove undesired particles which may form during ALD processing. © Copyright 2018 by Eric Christopher Stevens All Rights Reserved From Novel Processes to Industry-Relevant Applications: Atomic Layer Deposition of Metal, Metal Oxide, and Metal Carbide Thin-Films. by Eric Christopher Stevens A dissertation submitted to the Graduate Faculty of North Carolina State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy Chemical Engineering Raleigh, North Carolina 2018 APPROVED BY: _______________________________ _______________________________ Dr. Gregory N. Parsons Dr. Michael D. Dickey Committee Chair _______________________________ _______________________________ Dr. Saad Khan Dr. Fanxing Li DEDICATION I dedicate this work to my incredible wife, Amy. She is my rock and the love of my life. Without her, I would not be here today. Thank you, Amy. This is for you. ii BIOGRAPHY Eric Stevens was born and raised in Phoenix, AZ, to Chuck and Margaret Stevens. Eric attended Arizona State University (Go Devils) in Tempe, AZ, where he studied chemical engineering. Eric gained valuable research experience under the mentorship of Professor Lenore Dai, where he worked on the integration of silicon ribbons with stimuli responsive hydrogels. While at Arizona State, Eric was a teaching assistant for lower and upper division chemical engineering courses, as well as a tutor for organic chemistry. Eric decided to pursue graduate school following the completion of an internship at Pacific Northwest National Laboratory. Under the direction of Dr. Carlos Fraga, Eric designed and implemented a novel, chemical forensic technique to identify trace impurities in chemical warfare agents and establish a direct link to the respective manufacturer using two-dimensional gas chromatography/time-of-flight mass spectrometry. In Fall 2013, Eric began his Ph.D. in chemical engineering under the direction of Professor Gregory Parsons at North Carolina State University in Raleigh, NC. Eric’s research was mainly focused on development of new atomic layer deposition processes for deposition of metal and metal carbide thin films. Eric continued his studies at IMEC in Leuven, Belgium, under the mentorship of Professor Annelies Delabie. At IMEC, Eric studied the use of atomic layer deposition for advanced patterning applications relevant to the semiconductor industry. Eric will join the Research and Development team at ASM America in Phoenix, AZ, after graduation. Outside of research, Eric enjoys hiking and camping with his wife Amy and dog Pinot “Mr. Grigio” Stevens. Eric and Amy love to travel and experiencing new cultures together. During his free time, Eric also enjoys playing guitar, wood working, and playing basketball. iii ACKNOWLEDGMENTS To my advisor Professor Gregory Parsons, thank you for your guidance and support throughout this process. You have molded me into a researcher and scientist, constantly encouraging me to find answers to challenging problems. Thank you for sticking by me through everything and helping me with a slight nudge here and a carefully crafted “…” in your emails. I am honored to be one of your students and future colleague in the ALD community. To Professor Annelies Delabie, thank you for giving me the opportunity to conduct research at IMEC. That experience was both challenging and gezellig (did I use this in the correct context?), and one that had a profound impact on my future and for that I am extremely grateful to you and entire team at IMEC, including Yoann, BT, Efrain, Sven, and Elie. Dank u wel voor alles! To Professor Lenore Dai, thank you for your support and guidance during my time at ASU. You helped me tremendously along the way, without you I wouldn’t have likely pursued graduate school. To Mr. Mariner, thank you for piquing my interest in chemistry and steering me towards a major in Chemical Engineering. You gave me a passion for teaching and I aim to make STEM outreach a major part of my life going forward. With regards to breaking things and setting them on fire… you also gave me that passion as well. A special thanks to my fellow classmates and friends at NC State: Wenyi, Jenny, Mariah, Jason, Adam, Ryan, and Ishan. It has been a long journey, but we finally made it. All the long nights working on transport and perturbation theory were well worth it in the end! To my parents, Chuck and Margaret, thank you for instilling a sense of curiosity and encouraging my success in school. Without your support and guidance, I would not be the person I am today. You’ve been incredible parents to me and I hope you know just how appreciative I am iv of the sacrifices you made for my future. I hope to be half the person you both are in the future. Thank you and I love both you so much. To the rest of my family, Matt, Lauren, Shawn, Gina, Daniel, Jim, and Lisa, thank you for your love and support through this, and for all the less than exciting conversations you all endured regarding my research. Although I am the youngest of the three brothers, I feel that I am the favorite. I wanted that to be in writing for future generations to know. Joking aside, your support has no bounds and for that I am grateful. Love you guys. Lastly, to Amy. Thank you. From encouraging me during those first few discussions about pursuing graduate school, to moving across the country and starting our married life together in North Carolina, to crossing off a bucket list item as we lived, worked, and explored in Europe, and navigating through our toughest times – thank you for being my partner. Your unconditional love and support provided me with hope and a renewed vigor going into the next day. You’ve been my shoulder to cry on, my hand to hold, my ear to listen, and my light in the darkest times. Without you, I would have never reached this point and for that I am grateful. I cherish the moments we shared during this journey and I am ecstatic to experience the next chapter in our lives. Thank you for always making me the luckiest guy in the room. Love you, Cherish. v TABLE OF CONTENTS LIST OF TABLES ...................................................................................................................... xiii LIST OF FIGURES .................................................................................................................... xiv Chapter 1: Introduction and Background ................................................................................. 1 1.1 Atomic Layer Deposition Background and Applications ...............................................
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