Watch Professor Brainard's "Inside CNSE" video interview on the use of extreme ultraviolet (EUV) photoresists in making computer chips

Degrees

• Post-Doc (Chemical Engineering), Stanford University
• Ph.D. (Organic Chemistry), Massachusetts Institute of Technology
• B.S. (Chemistry), University of California, Berkeley

Research areas

• Extreme ultraviolet (EUV, 13.5 nm) photoresists: new materials and exposure mechanisms
• 193-nm blocking groups and polymers
• New photoacid generator (PAG) chemistry
• Acid amplifiers for microelectronic and biological applications
• Molecular Organometallic Resists for EUV (MORE)
• Self-assembling polymers for biological applications
• Design of small-molecules for biological applications

Research Description

Dr. Brainard's research is concerned with the design, synthesis and characterization of new molecules and polymers for their use in nanotechnology. His projects are divided between those involving the synthesis of new compounds and those involving characterizing the functionality of these new materials in chemical systems relevant to nanotechnology.

Much of this research is focused on photoresists. Photoresists are light-sensitive layers used in nearly every step in the manufacture of integrated circuits and the building of circuit boards. Photoresists are also essential to the fabrication of micro-electro-mechanical systems (MEMs). Dr. Brainard’s research studies many of the components of photoresists including: polymers, photoacid generators and acid amplifiers. Much of this research is based on first developing mechanistic understanding of how these components work (using kinetics and computer modelling) and then redesigning and synthesizing small molecules and polymers. Ultimately, the new materials are evaluated as photoresists by exposure to 365-nm, 248-nm, 193-nm or 13.5-nm light.

EUV Photoresists. Dr. Brainard is the first chemist in the world to design resists for use in Extreme Ultraviolet (EUV, 13.5 nm) Lithography, starting in 1998 while working at Rohm and Haas in Massachusetts. As a professor, he and his students have continued to design, synthesize and characterize new materials for use in photoresist. Additionally, much of his group’s research has focused on understanding the fundamental mechanisms of exposure to EUV light.

EUV Exposure Mechanisms. The exposure mechanisms that occur in chemically amplified resists (CARs) during exposure to 193- or 248-nm light are well understood. For example, either the photon is absorbed by a photo-acid generator (PAG), creating an excited state in the PAG, or the photon is absorbed by the polymer, which can then sensitize a PAG molecule.

However, the underlying physical and chemical mechanisms of EUV exposure are areas of active research, and many of the fundamental questions remain unanswered. Research in the Brainard group attempts to answer specific questions, namely:

1. What are the elementary physical and chemical mechanisms in EUV photochemistry?
2. What is the total number of electrons generated (total electron yield) during EUV exposure?
3. How far do electrons generated in EUV exposure travel in resists?

New PAG Chemistry. Photoacid Generators (PAGs) are at the heart of every chemically-amplified resist. While the electronics industry has been well served by three basic types of PAG classes (Onium, Imide, and Diazo), there are other types of PAG classes that can be developed based on a simple set of assumptions. Dr. Brainard's group has investigated the design, synthesis and evaluation of new types of PAG molecules.

Acid Amplifiers. Photogenerated acid is an extremely important component to all photoresists used to manufacture state-of-the-art electronic devices. A class of compound, known as an acid amplifier can autocatalyically generate acid. The Brainard group has designed and synthesized more than forty new acid amplifiers for use in 193-nm and EUV lithography. This is still an active area of research as the group seeks new applications in which the manipulation of acid concentration can be beneficial.

Double Deprotected-CAMP Photoresists. Most positive-tone photoresists work through acid-catalyzed deprotection reactions. These deprotection steps occur via a single acid catalyzed step. Based on the mechanistic insight gained from the development of acid amplifiers, the Brainard group designed a new type of photoresist based on Double Deprotected-CAMP polymers which require two acid-catalyzed steps to remove a protecting group from a polymer. This new approach provides advantages in its ability to manipulate the information delivered to the resist via exposure systems.

Molecular Organometallic Resists for EUV (MORE). In 2009 key researchers in the microelectronics industry realized that EUV photoresists needed to be more efficient at stopping and absorbing EUV photons. Additionally, since second-row elements (e.g., C, O, N, F) are relatively transparent to EUV light, other elements must be used. In 2011, the Brainard group started a program to design and synthesize organometallic compounds containing transition or main group metallic elements. To date, over a thousand compounds have been synthesized and evaluated lithographically. This project continues to this day.

Selected Publications

Books

1. Y. Wei and R. Brainard, "Advanced Processes for 193-nm Immersion Lithography", SPIE Press, 2009.

Book Chapters

1. R. Brainard, M. Neisser, G. Gallatin, A. Narasimhan, “Photoresists for EUV Lithography”; Ed.: V. Bakshi; In: EUV Lithography. SPIE Press, 2018; Chapter 8 pp 493-591.
2. R. Brainard, "Photoresists for Extreme Ultraviolet Lithography"; Ed.: V. Bakshi; In: EUV Lithography. SPIE Press, 2008; Chapter 8 pp 383-448.

Journal Publications

1. M. Wilklow-Marnell, D. Moglia, B. Steimle, B. Cardineau, H. Al-Mashat, P. Nastasi, K. Heard, A. Aslam, R. Kaminski, M. Murphy, R. Del Re, M. Sortland, M. Vockenhuber, Y. Ekinci, R. L. Brainard, D. A. Freedman, "First-row transitional-metal oxalate resists for EUV," J. Micro/Nanolith. MEMS MOEMS 17(4), 043507 (2018).
2. M. Murphy, J. Sitterly, S. Grzeskowiak, G. Denbeaux, R. L. Brainard, "Mechanisms of photodecomposition of metal-containing EUV photoresists: isotopic labelling studies"; Proc. SPIE 10586, Adv. Pat. Mat. Proc., 1058608 (2018).
3. J. Sitterly, M. Murphy, S. Grzeskowiak, G. Denbeaux, R. L. Brainard, "Molecular organometallic resists for EUV (MORE): Reactivity as a function of metal center (Bi, Sb, Te and Sn)"; Proc. SPIE 10586, Adv. Pat. Mat. Proc., 105861P (2018).
4. M. Murphy, J. Sitterly, S. Grzeskowiak, G. Denbeaux, R. L. Brainard, “Mechanisms and Reactivity of EUV Photoresists Containing Antimony, Bismuth, Tellurium and Tin”, J. Photopolym. Sci. Technol. 31(2) 233 (2018).
5. A. Narasimhan, L. Wisehart, S. Grzeskowiak, L. E. Ocola, G. Denbeaux, R. L. Brainard, “What We Don’t Know About EUV Exposure Mechanisms”, J. Photopolym. Sci. Technol. 30(1), 113-120 (2017).
6. M. Murphy, A. Narasimhan, S. Grzeskowiak, J. Sitterly, P. Schuler, J. Richards, G. Denbeaux and R. L. Brainard, “EUV Mechanistic Studies of Antimony Resists”, J. Photopolym. Sci. Technol. 30(1), 121-131 (2017).
7. D. Soucie W. Earley, K. Hosoi, A. Takahashi, T. Aoki, B. Cardineau, K. Miyauch, R. Brainard; “Higher-Order Lithography: Double-Deprotected Chemically Amplified Photoresists (DD-CAMP)”, J. Photopolym. Sci. Technol. 30(3), 351-360 (2017).
8. S. Rangan, R. A Bartynski, A. Narasimhan, R. L. Brainard, “Electronic structure, excitation properties, and chemical transformations of extreme ultra-violet resist materials”, J. Applied Phys. 122(2), 025305 (2017).
9. Narasimhan, S. Grzeskowiak, C. Ackerman, T. Flynn, G. Denbeaux, R. L. Brainard; "Mechanisms of EUV exposure: electrons and holes”; Proc. SPIE, 10143, EUVL, 101430W (2017).
10. M. Murphy, A. Narasimhan, S. Grzeskowiak, J. Sitterly, P. Schuler, J. Richards, G. Denbeaux, R. L. Brainard; "Antimony photoresists for EUV lithography: mechanistic studies”; Proc. SPIE, 10143, EUVL, 1014307 (2017).
11. L. Wiseheart, A. Narasimhan, S. Grzeskowiak, M. Neisser, L. E. Ocola, G. Denbeaux, R. L. Brainard; “Energy deposition and charging in EUV lithography: Monte Carlo studies”; Proc. SPIE, 9776, pp 97762O (2016).
12. A. Narasimhan, S. Grzeskowiak, J. Ostrander, J. Schad, E. Rebeyev, M. Neisser, L. E. Ocola, G. Denbeaux, R. L. Brainard; “Studying electron-PAG interactions using electron-induced fluorescence”; Proc. SPIE, 9779, Advances in Patterning Materials and Processes XXXIII, 97790F (2016).
13. Narasimhan, S. Grzeskowiak, B. Srivats, H. Herbol, L. Wisehart, J. Schad, C. Kelly, W. Earley, L. E. Ocola, M. Neisser, G. Denbeaux, and R. L. Brainard, “Studying thickness loss in extreme ultraviolet resists due to electron beam exposure using experiment and modeling” J. Micro/Nanolith. MEMS MOEMS 14(4), 043502 (2015).
14. J. Passarelli, M. Murphy, R. Del Re, M. Sortland, J. Hotalen, L. Dousharm, Y. Ekinci, M. Neisser, D. Freedman, R. Fallica, D. A. Freedman, R. L. Brainard, "Organometallic carboxylate resists for extreme ultraviolet with high sensitivity," J. Micro/Nanolith. MEMS MOEMS 14(4), 043503 (2015).
15. R. Del Re, J. Passarelli, M. Sortland, B. Cardineau, Y. Ekinci, E. Buitrago, M. Neisser, D. A. Freedman, and R. L. Brainard, ”Low-line edge roughness extreme ultraviolet photoresists of organotin carboxylates”, J. Micro/Nanolith. MEMS MOEMS 14(4), 043506 (2015).
16. M. Sortland; J. Hotalen; R. Del Re, J. Passarelli, M. Murphy, T. S. Kulmala, Y. Ekinci, M. Neisser, D. A. Freedman, R. L. Brainard, "Platinum and palladium oxalates: positive-tone extreme ultraviolet resists," J. Micro/Nanolith. MEMS MOEMS 14(4), 043511 (2015).
17. J. Passarelli, M. Sortland, R. Del Re, B. Cardineau, C. Sarma, D. Freedman, R. Brainard; “Bismuth resists for EUV lithography,” J. Photopolym. Sci. Technol. 27(5), 655-661 (2014).
18. J. Torok, B. Srivats, S. Memon, H. Herbol, J. Schad, S. Das, L. Ocola, G. Denbeaux, R. Brainard, “Electron penetration depths in EUV photoresists,” J. Photopolym. Sci. Technol. 27(5), 611-615 (2014).
19. B. Cardineau, R. Del Re, M. Marnell, H. Al-Mashat, M. Vockenhuber, Y. Ekinci, C. Sarma, D. Freedman, R. Brainard, “Photolithographic properties of tin-oxo clusters using extreme ultraviolet light (13.5 nm),” Microelectronic Engineering 127, 44-50 (2014).
20. J. Torok, R. Del Re, H. Herbol, S. Das, I. Bocharova, A. Paolucci, L. E. Ocola, C. Ventrice, E. Lifshin, G. Denbeaux and R. L. Brainard; "Secondary electrons in EUV lithography," J. Photopolym. Sci. Technol. 26 (5), 625-634 (2013).
21. B. Cardineau, P. Garczynski, W. Earley and R. L. Brainard; "Chain-scission polyethers for EUV lithography," J. Photopolym. Sci. Technol. 26 (5), 665-671 (2013).
22. B. Cardineau, W. Earley, T. Fujisawa, K. Maruyama, M. Shimizu, S. Sharma, K. Petrillo and R. L. Brainard; "LER limitations of resist thin films," J. Photopolym. Sci. Technol. 25 (5), 633-640 (2012).
23. K. Hosoi, B. Cardineau, S. Kruger, K. Miyauchi and R. L. Brainard; "Fluorine-stabilized acid amplifiers for Use in EUV lithography," J. Photopolym. Sci. Technol. 25 (5), 575-581 (2012).
24. M. Trikeriotis, M. Krysak, Y. Sook Chung, C. Ouyang, B. Cardineau and R. Brainard, C. K. Ober, E. P. Giannelis, K. Cho; "Nanoparticle photoresists from HfO2 and ZrO2 for EUV patterning," J. Photopolym. Sci. Technol. 25 (5), 583-586 (2012).
25. S. Kruger, C. Higgins, G. Gallatin and R. L. Brainard; "Lithography and chemical modeling of acid amplifiers for use in EUV photoresists," J. Photopolym. Sci. Technol. 24 (2), 143-152 (2011).
26. C. D. Higgins, C. R. Szmanda, A. Antohe, G. Denbeaux, J. Georger, R. L. Brainard, "Resolution, line-edge roughness, sensitivity tradeoff, and quantum yield of high photo acid generator resists for extreme ultraviolet lithography” Jpn. J. Appl. Phys. 50(3) 036504, (2011).
27. S. Kruger, C. Higgins, S. Revuru, S. Gibbons, D. Freedman, R. L. Brainard, “Can Acid Amplifiers Help Beat the Resolution, Line Edge Roughness, and Sensitivity Trade-Off?” Jpn. J. Appl. Phys. 49(5) 041602, (2010).
28. S. A. Kruger, C. Higgins, B. Cardineau, T. R. Younkin, R. L. Brainard, "Catalytic and Autocatalytic Mechanisms of Acid Amplifiers for Use in EUV Photoresists", Chemistry of Materials (2010), 22(19), 5609-5616.
29. C. Higgins, S. Kruger, V. Kamineni, R. Matyi, J. Georger, R. Brainard, "Understanding ultra-thin film resist and underlayer performance through physical characterization", J. Photopoly. Sci. Tech., 23(5), 699-707, (2010).
30. B. Cardineau, S. Kruger, W. Earley, C. Higgins, S. Revuru, J. Georger, R. Brainard, "Chain-scission polyesters for EUV lithography", J. Photopoly. Sci. Tech., 23(5), 665-671, (2010).
31. S. Kruger, S. Revuru, C. Higgins, S. Gibbons, D. Freedman, W. Yueh; T. Younkin, R. Brainard, "Fluorinated Acid Amplifiers for EUV Lithography", J. Am. Chem. Soc., 131(29), 9862–9863 (2009).
32. R. Brainard, S. Kruger, C. Higgins, S. Revuru, S. Gibbons, D. Freedman, W. Yueh, T. Younkin, "Kinetics, Chemical Modeling and Lithography of Novel Acid Amplifiers for Use in EUV Photoresists", J. Photopoly. Sci. Tech. 22(1), 43-50, (2009).
33. R. Brainard, C. Higgins, E. Hassanein, R. Matyi, A. Wuest, "Film quantum yields of ultrahigh PAG EUV photoresists", J. Photopoly. Sci. Tech. 21(3), 457-464 (2008).
34. K. Petrillo, Y. Wei, R. Brainard, G. Denbeaux, D. Goldfarb, C. Koay, J. Mackey, W. Montgomery, W. Pierson, T. Wallow, O. Wood, "Are extreme ultraviolet resists ready for the 32 nm node?", J. Vac. Sci. Tech., B25(6), 2490-2495 (2007).
35. R. Brainard, S. Kruger, E. Block, "Models for predicting the index of refraction of compounds at 193 and 589 nm", Proceed. SPIE, 6519, 651920/1-651920/7, (2007).
36. G. Gallatin, P. Naulleau, R. Brainard, "Fundamental limits to EUV photoresist", Proceed. SPIE, 6519, 651911/1-651911/10, (2007).

Patents

1. R. L. Brainard, W. G Earley, B. Cardineau, T. Aoki, “Double-deprotected chemically amplified photoresists”, PCT Int. Appl. (2016), WO 2016161067 A1 20161006
2. R. Brainard, “Acid amplifiers,” US 8501382 B1 (2013).
3. Brainard, Robert L.; Revuru, Srividya; “Chain scission polyester polymers for photoresists” U.S. (2013), US 8349990 B2 20130108.
4. Robert L. Brainard and Brian Cardineau, Patent No. WO2012135286A2 (2012).
5. Brian Cardineau and Robert L. Brainard, Patent No. WO2012135278A2 (2012).
6. Robert L. Brainard, Patent No. US20110130538A1 (2011).
7. Robert L. Brainard and Brian Cardineau, Patent No. US20110152570A1 (2011).
8. Robert L. Brainard and Brian Cardineau, Patent No. US20110152496A1 (2011).
9. R. Brainard, "Acid-Labile Polymers and Monomers for their Construction", Provisional Application, Aug. 2009.
10. R. Brainard, "Photolytic Acid-Generating Polymers and Monomers for their Construction", Provisional Application, Aug. 2009.
11. B. Cardineau, R. Brainard, "Methods for Making Sterically Hindered Ethers", Provisional Application, Aug. 2009.
12. R. Brainard, "Acid Amplifers (1,3-Acyclic, Fluorinated)", Provisional Application, Feb. 2009.
13. R. Brainard, "Acid Amplifers (Cyclohexyl, Fluorinated)", Provisional Application, Feb. 2009.
14. R. Brainard, S. Revuru, "Chain Scission Polyester Polymers for Photoresists", Full Application, Feb. 2009.
15. R. Brainard, "Cyclohexane-1,2-diol Derivative Acid Amplifiers", Provisional Application, Feb. 2009.
16. R. Brainard, R. Auger, J. Lachowski, "Stripper", US2007066502, 2005-07-28.
17. G. Taylor, R. Brainard, "Novel polymers and photoresist compositions for short wavelength imaging", AU8895201, 2002-03-22.
18. G. Taylor, R. Brainard, "Novel polymers and photoresist compositions for short wavelength imaging", US7132214, 2006-11-07.
19. R. Brainard, C. Szmanda, "Photoresist for imaging with high energy radiation", JP2002055457, 2002-02-20.
20. R. Brainard, "Novel polymers and photoresist compositions comprising same", EP1031878, 2000-08-30.
21. R. Brainard, "New Polymer and Photoresist composition containing the same", JP2000239538, 2000-09-05.
22. R. Brainard, "Polymers and photoresist compositions comprising same", US6492087, 2002-12-10.