University of Massachusetts - Amherst ScholarWorks@UMass Amherst Doctoral Dissertations 2014-current Dissertations and Theses 2014 Self-Assembly of Block Copolymers by Solvent Vapor Annealing, Mechanism and Lithographic Applications Xiaodan Gu University of Massachusetts - Amherst, [email protected] Follow this and additional works at:http://scholarworks.umass.edu/dissertations_2 Recommended Citation Gu, Xiaodan, "Self-Assembly of Block Copolymers by Solvent Vapor Annealing, Mechanism and Lithographic Applications" (2014). Doctoral Dissertations 2014-current.Paper 7. This Open Access Dissertation is brought to you for free and open access by the Dissertations and Theses at ScholarWorks@UMass Amherst. It has been accepted for inclusion in Doctoral Dissertations 2014-current by an authorized administrator of ScholarWorks@UMass Amherst. For more information, please [email protected]. SELF-ASSEMBLY OF BLOCK COPOLYMERS BY SOLVENT VAPOR ANNEALING, MECHANISM AND LITHOGRAPHIC APPLICATIONS A Dissertation Presented by XIAODAN GU Submitted to the Graduate School of the University of Massachusetts Amherst in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY February 2014 Polymer Science and Engineering (cid:1) (cid:1) © Copyright by Xiaodan Gu 2014 All Rights Reserved (cid:1) (cid:1) SELF-ASSEMBLY OF BLOCK COPOLYMERS BY SOLVENT VAPOR ANNEALING, MECHANISM AND LITHOGRAPHIC APPLICATIONS A Dissertation Presented by XIAODAN GU Approved as to style and content by: __________________________________________ Thomas P. Russell, Chair __________________________________________ Kenneth R. Carter, Member __________________________________________ Mark Tuominen, Member ________________________________________ David A. Hoagland, Department Head Polymer Science and Engineering (cid:1) (cid:1) DEDICATION To my parents, Jianfei Gu and Caifeng Zhong. (cid:1) (cid:1) ACKNOWLEDGMENTS The work in this thesis was not possible without the efforts from my collaborators and coworkers. First, my thesis advisor Prof. Thomas P. Russell deserves the credits for directing my research project, funding my work, and providing me collaboration resources through out my Ph.D. degree. Tom, as a pioneer in block copolymer self-assembly, showed me the beauty of the molecular self-assembly. Numerous times, Tom stimulates my interested in the polymer physics, provides me invaluable guidance, and nudges me in the right direction. I also want to thank Prof. Mark Tuominen and Prof. Kenneth R. Carter to serve on my thesis committee and provide me valuable suggestions on the research proposal and thesis writing. I also want to acknowledge my collaborators, especially Dr. Deirdre Olynick in the Molecular Foundry at Lawrence Berkeley National Lab (LBNL) and Paul Dorsey at Western Digital Inc. Deirdre’s expertise in the plasma etching greatly facilitates the projects related to block copolymer lithography. Dr. Paul Dorsey, my supervisor at the Western Digital, gives me unique experiences to work at corporative environments and carry out cutting edge research projects. I also want to thank all of the members in the Russell group for their assistance not only in lab but also in life during my stay in Amherst. I enjoyed working together with them for the past five years. I own a lot to the helps I received from the BCP self- assembly research team members, including Dr. Soojin Park, Dr. Donghyun Lee, Dr. Sungwoo Hong, Dr. Bokyung Kim, Dr. Yunxia Hu, Dr. Wei Chen, Dr. Ji Xu, Dr. Wei (cid:3)(cid:1) Zhao, Dr. Weiyin Gu, Dr. Ilja Gunkel, Zhiwei Sun, Gajin Jeong. Especially, I want to thank Sungwoo and Ilja, both who I have been closely interacted with. Sungwoo, a very hard working person, is a role model for me to start my research career. Working with Ilja is an amazing thing in my Ph.D. Lots of research ideas were spackled from our lunch discussion at ALS. He made my stay in ALS not boring. I also own a lot for the assistances I received from Laurie Banes, who helped me with purchases of chemicals. I would also like to thank Advanced Light Source at LBNL for providing the doctoral fellowship to me, and allow me to perform experiments using state-of-art synchrotron facility. Especially, thanks Dr. Alexander Hexemer to host me as a student researcher at the Advanced Light Source at LBNL in beamline 7.3.3 for the past years. His knowledge in X-ray science is very beneficial for the projects. He also showed me how to balance work and family and I enjoyed the BBQ parties in his house. This project would have gone nowhere real fast without the assistance from the 7.3.3 and 11.0.1.2 staffs at the Advanced Light Source and Nano-fabrication facility in the Molecular Foundry in the LBNL. Thanks to Eric Schabile, who received my phone calls at midnight to ask for help on instrumental problems. I appreciate the help from beamline associates Steven Alvarez, Eumhee Lin, Polite Staward, Dr. Elaine Chan. I appreciate Dr. Cheng Wang’s sincere help on the soft X-ray measurements and suggestions on project and career plan. I also would like to thanks knowledgeable and helpful staffs at the Molecular Foundry. The supports I received from Dr. Stefano Cabrini, Bruce Harteneck, Erin Wood, Dr. Scott Dhuey, Dr. Adam Schwartzberg, Dr. Zuwei Liu are very important for the block copolymer lithgraphy project. I am proud and honored to stay at the world-renowned department of Polymer (cid:3)(cid:2)(cid:1) Science and Engineering at University of Massachusetts at Amherst. I must express my thankfulness to the entire faculties, who curate the next generation polymer scientist, staffs, who keeps the department running smoothly, and 2008 PSE classmates, whom made my life in Amherst very entertaining. At last, I am grateful to my family and friends for their supports throughout my study. Finally, thanks to Yuanyuan, your encouragement to me on my career and life. I am extremely lucky to meet you and have you in my life. (cid:3)(cid:2)(cid:2)(cid:1) ABSTRACT SELF-ASSEMBLY OF BLOCK COPOLYMERS BY SOLVENT VAPOR ANNEALING, MECHANISM AND LITHOGRAPHIC APPLICATIONS FEBRUARY 2014 XIAODAN GU B.S., NANJING UNIVERSITY M.S., UNIVERSITY OF MASSACHUSETTS AMHERST Ph.D., UNIVERSITY OF MASSACHUSETTS AMHERST Directed by: Professor THOMAS P. RUSSELL Block copolymers (BCP) are a unique class of polymers, which can self-assemble into ordered microdomains with sizes from 3 nm to about 50 nm making BCPs an appealing meso-scale material. In thin films, arrays of BCP microdomains with long- range lateral order can serve as ideal templates or scaffolds for patterning nano-scale functional materials and synthesizing nanostructured materials with size scales that exceed the reach of photolithography. Among many annealing methods, solvent vapor annealing (SVA) is a low-cost, highly efficient way to annihilate defects in BCP thin films and facilitates the formation of highly ordered microdomains within minutes. Directing the self-assembly of BCPs could, in principle, lead to the formation of domains with near perfect lateral ordering. The mechanism of SVA of BCPs, however, is still ill- understood, albeit it has been widely adopted in research laboratories around the world (cid:3)(cid:2)(cid:2)(cid:2)(cid:1) for the past decade. In the first part of this thesis, the ordering process of BCP thin films during annealing in neutral solvents was investigated mainly by in situ synchrotron X-ray scattering. Briefly, the solvent molecules impart mobility to the BCP and enable a marked improvement in the lateral ordering of the BCP microdomains. Both, BCP concentration in the swollen film and the rate of solvent removal play a key role in obtaining films with well-ordered microdomains. The amount of swelling in a BCP thin film during SVA depends on the chemical nature of the blocks, the quality of the solvent, and the molecular weight of the BCP. A high degree of swelling - still low enough to prevent solvent-induced mixing (disordering) of BCP microdomains,- provides a high chain mobility, and thus results in the formation of arrays of ordered microdomains with large grain sizes after SVA in neutral solvents. The rate of solvent removal is another critical parameter for obtaining long-range lateral order in BCP thin films after SVA in neutral solvents. While in the swollen state ordered structures form with exceptional order, removal of the solvent results in a deterioration of order due to the confinement imposed to a BCP in a thin film by the rigid silicon substrate. It was found, however, that an instantaneous solvent removal can minimize disordering to preserve the order formed in the swollen state. Self-assembled BCP microdomains also serve as ideal template to pattern other materials with exceptional lateral resolution. In this thesis, two examples of BCP lithography was also demonstrated. A reconstruction process was used to enhance the etch contrast between two organic blocks. In one example, a BCP pattern was transferred to a silicon substrate to form high aspect ratio, 5:1, sub-10nm silicon lines or holes with (cid:2)(cid:4)(cid:1)