Molecular Organometallic Resists for EUV (MORE) October 6, 2013

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1 Molecular Organometallic Resists for EUV (MORE) October 6, 2013 Brian Cardineau, 1 James Passarelli, 1 Miriam Sortland, 1 Ryan Del Re, 1 Westly Tear, 1 Hashim Al-Mashat, 2 Miles Marnell, 2 Kara Heard, 2 Amber Aslam, 2 Jason Pavlich, 2 Rachel Kaminski, 2 Peter Nastasi, 2 Chandra Sarma, 3 Dan Freedman, 2 Robert Brainard 1 1. CNSE 2. SUNY New Paltz 3. Sematech I. Introduction Presenter Wang Yueh, Intel II. III. Organo-Tin Complexes Ligand Studies: Oxalate Anions IV. Summary Financial Support by Intel and Sematech 1

2 Recent Advances in Inorganic Photoresists Recently, some researchers have developed new EUV resists based on inorganic compounds and nanoparticles with excellent performance. HSQ Hafnium-Oxide Nanoparticles A Inpria B Cornell 7-nm h/p lines 294 mj/cm 2 12-nm h/p lines 8-nm h/p lines 36-nm h/p lines 25 mj/cm 2 47 mj/cm 2 12 mj/cm 2 Ekinci et al., Proc. SPIE, 2013, Trikeriotis et al., Proc. SPIE, 2012,

3 Molecular Organometallic Resists for EUV (MORE) We have proposed a new EUV resists consisting of molecular inorganic or organometallic compounds that utilize metal centers with high EUV optical density. Potential Benefits: 1. High EUV OD: Maximize the use of precious EUV photons. 2. High Mass Density: The mean-free path of secondary-electrons is shorter in high mass-density materials. For resists this would result in a decrease in electron blur. 3. No Acid Diffusion: No acid catalysis. 4. Excellent Etch Rates: Metal oxide films can have significantly better etch performance than even the best organic films (HfO 2 ~ 25x better).* 5. High Uncatalyzed Reactivity: Since metals have a large range of redox potentials, resist chemistry can be engineered for high sensitivity without acid catalysis. * Trikeriotis et al., Proc. SPIE, 2012,

4 Optical Density of the Elements The MORE program is exploring the utility of compounds made from the darkest elements in the periodic table. 4

5 Processing of MORE Compounds Pure MORE compounds were spin-cast from organic solvents 1.5 to 3% Solids Solvents: Mixtures of MEK, THF, Hexane, CH 2 Cl 2, Water, IPA. Most films had no other additives Soft bakes were generally not used. Film thicknesses were nm. EUV Exposures Berkeley exposures used the DCT and produced contrast curves. PSI exposures produced dense-line patterns. 18 nm was the smallest feature on the masks. Development Solvents were selected that just cleared the resists in seconds. Developer Solvents: Mixtures of MEK, THF, Hexane, CH 2 Cl 2, Water, IPA. Negative Tone Although some positive-tone behavior has been observed, everything presented today is of negative-tone resists. 5

6 II. Organo-Tin Complexes Tin is one of the darkest elements in the periodic table. Tin is used as fuel in many EUV sources. A. Mononuclear Tin Complexes B. Sn-12 Oxo Complexes Kuhlman et al., 2005 US Patent Cl - Cl - Preliminary Results showed 20 mj/cm 2 Negative-Tone Sensitivity 6

7 A. Evaluation of Eleven Mononuclear Tin Complexes 7

8 B. Possible Mechanisms for Photoreactivity of Sn-12 Oxo Clusters 1. Anionic Ligand Dissociation 2. Homolysis of Sn-C Bond 3. Sn-O Metathesis 8

9 Tin-12 Oxocluster Investigation 1) Anionic Ligand Dissociation What effect does changing the anionic ligand have on resist performance? 9

10 Effect of Counter-Ion Structure on E Size Bond Dissociation Energy (Kcal/mol) Luo, Handbook of Bond Dissociation Energies in Organic Compounds, (2003). * - Value calculated through H-R bond energy 10

11 BMET Results: Contrast Curves Expected Decarboxylation Reactivity E max The resist sensitivity seems to be affected more by ligand bulk and less by decarboxylation. Therefore, anion decomposition is probably NOT the photochemical mechanism. 11 BMET

12 LER (nm) Dose (mj/cm 2 ) Tin metal-oxide films are capable of resolving nm, but sensitivity is a problem h/p CD (nm) (PSI March 2013)

13 III. Ligand Studies: Oxalate Anions 1. Known, useful photochemistry: Crosslinking through open coordination sites. Metal is both reduced and has lower coordination number, changing solubility. 2. Ease of synthesis for a wide variety of metals and ancillary ligands. - We have synthesized over 30 new compounds, selected to give systematic information on the EUV photochemistry of metal oxalate compounds. 13

14 Central Metal Through this work we have tested Cr, Fe, Co, Cu and Ni oxalate complexes. In general: Cu and Ni form 4-coordinate complexes with poor solubility. Fe complexes are often very crystalline and difficult to get coatings of. The general reactivity is in the order of Cr Fe < Co. NP1 Cr Co E max = 35 mj/cm 2 E max = 8 mj/cm 2 BMET 14

15 Central Metal Through this work we have tested Cr, Fe, Co, Cu and Ni oxalate complexes. In general: Cu and Ni form 4-coordinate complexes with poor solubility. The general reactivity is in the order of Cr < Fe Co. NP1 The metals are all in the +3 oxidation state. 15

16 Oxalate Loading Through this work we have also tested the effect of oxalate loading on resist sensitivity. Increasing oxalate from 0 to 3 improves sensitivity by several orders of magnitude (1400 to 3 mj/cm 2 ). NP1 * E max (mj/cm 2 ): >1400 ~ BMET 16

17 NP1 Imaging Studies PSI MEK Develop / 15s 30 nm Thickness Dose of 30 mj/cm 2 PAB = 90 /60s PEB = None Resolution h/p (nm): LER (nm): (PSI March 2013) 17

18 NP1 Bake Study A bake study was performed and a PAB of 90 for 60s with no PEB appears to perform the best. LER (nm) MEK Develop / 15s 43 nm Thickness Dose (mj/cm 2 ) PAB (None) PEB (None) PAB (90 /60s) PEB (90 /60s) PAB (90 /60s) PEB (None) h/p CD (nm): Imaging Conducted at PSI

19 IV. Summary Over a hundred compounds were tested for spin-coating and EUV sensitivity during Year 1 under Intel. About half of the complexes have good coating and good air stability. We have discovered 6-10 new MORE complexes with 18 nm resolution. Most coatings showed some EUV sensitivity, although some were quite slow ( mj/cm 2 ). Oxalate has proven to be an excellent ligand and produces highly sensitive non-chemically amplified resists. Our best resist (NP1) is capable of ~22 nm dense lines at ~20 mj/cm 2. In year 2 of MORE, under Sematech, we plan to continue to develop the successful resists we have, while developing new platforms: o o Improve Current Platforms Explore New Platforms 19

20 Acknowledgements Financial Support: Intel Corporation Steve Putna Wang Yueh Sematech Mark Neisser Stefan Wurm Staff at PSI: Michaela Vockenhuber Yasin Ekinci Staff at LBNL: Patrick Naulleau Brian Hoef Lori Mae Baclea Gideon Jones Paul Denham And you for your time 20

21 Appendix 21

22 Expected Metal-Oxide Etch Rates The etch rates for most metal oxides are unknown. However, due to the high melting points / boiling points of the metal fluorides, we expect extremely good etch rates. Traditional CAMP: Fluoride MP (ºC) BP (ºC) CF SiF MORE Resists: SnF 4 >700 BiF CoF CoF FeF 3 >1000 FeF CrF CrF Unlike the fluorides of carbon and silicon which volatilize during the etch, MORE materials should remain solid, dramatically improving etch resistance. 22