1. Fabrication of nanostructures by means of Block Copolymer based lithography Monica Ceresoli Supervisor: Prof. Paolo Milani Co-Supervisor: Dr. Michele Perego

2. Introduction Implementation of self-assembling materials in Microelectronics lithography. ITRS 2011 Edition: “Emerging Research Materials” 2003 90 nm 2005 65 nm 2007 45 nm 2009 32nm 2011 22 nm 2013 14 nm 2015 10 nm ManifacturingDevelopmentResearch Fabrication issue: sub 20 nm structures Requirements: High density Long range order Simple and short process

3. BLOCK COPOLYMERS (BCP): class of macromolecules produced by covalently bonding two or more chemically distinct polymer blocks. Thermal treatment Introduction I.Botiz et al., Materials Today 13, 42-51 (2010), F. S. Bates et al., Physics Today 52, 32-38 (1999) Lamellae Thermodynamic Incompatibility + Covalent Bond Phase separation in ordered nano-domains

4. Introduction Lithographic application of Lamellar thin films. Requirements: High density Long range order Simple and short process R. Ruiz et al., Adv. Mater. 2007, 19, 2157–2162, R. Ruiz et al., Adv. Mater. 19, 587–591 (2007) Furnace 100 minutes Annealing temperature (°C) Annealing time (min) Correlation length ξ (nm) Problems: Long time process. Weak dependence on Temperature and time of annealing. Small dimension of ordered domains (correlation length ξ)

5. Introduction Lithographic application of Lamellar thin films. Requirements: High density Long range order Simple and short process R. Ruiz et al., Adv. Mater. 2007, 19, 2157–2162, R. Ruiz et al., Adv. Mater. 19, 587–591 (2007) New study: Thermodynamics on short time-scale Problems: Long time process. Weak dependence on Temperature and time of annealing. Small dimension of ordered domains (correlation length ξ)

6. Materials and Techniques Preparation of lamellar thin films. Si SiO 2 Random Copolymer Neutralization of the substrate.

7. Materials and Techniques Preparation of lamellar thin films. Si SiO 2 Random Copolymer Neutralization of the substrate. Block Copolymer deposition. Poly (Styrene-block-Methyl Methacrylate) 50% PS 50% PMMA Block Copolymer

8. Materials and Techniques Preparation of lamellar thin films. Si SiO 2 Random Copolymer Neutralization of the substrate. Block Copolymer deposition. Block Copolymer Thermal treatment.

9. Materials and Techniques F. Ferrarese Lupi et al., Nanotechnology, 24 (2013) 315601 Standard thermal process in furnace : Hours! Slow heating and cooling ramp. Impossibility to fine-tuning the rate of thermal energy transferred to the sample. Novel approach with Rapid Thermal Processing: Seconds! Temperature (°C) Time (s) Heating ramp Steady state Cooling ramp Samples are heated by halogen lamps irradiation. Fast heating and cooling ramp. Real time –control of sample temperature. Temperatures up above 300°C.

10. Increasing the annealing temperature more and more ordered films get formed. Experimental Results 60s of annealing Temperature M. Ceresoli et al., 2013, submitted.

11. Experimental Results Temperature (°C) 60s treatment 10s treatment M. Ceresoli et al., 2013, submitted. Significant variations of the correlation length (ξ) have been observed.

12. Experimental Results Temperature (°C) 100 minutes conventional furnace 1minute in RTP time of process reduced by two orders of magnitude ? 60s treatment 10s treatment R. Ruiz et al., Adv. Mater. 2007, 19, 2157–2162 Two times higher ξ in respect to literature results.

13. Experimental Results R. Ruiz et al., Adv.Mater. 2007,19, 587-591, S. Ji, P.F. Nealey et al., Macrom. (2011) 44.4291. time (s) 290°C 270°C 250°C RTP 290°C Time of annealing 1s5s 10s 60s 5m 15m Correlation length ξ (nm)

14. Experimental Results 100 nm FFT  A double phase appears! 100 nm Selective remotion of PMMA phase Residual solvent at the interface with the substrate F. Ferrarese Lupi et al., Nanotechnology, 24 (2013) 315601

15. Experimental Results On courtesy of Prof. M. Laus, Università del Piemonte Orientale 1 10 100 1000 Time (s) 290°C RTP 290°C 1s Time of annealing Time (s) Solvent content 5s 10s 60s 5m 15m  cylinders drive order Correlation length ξ (nm)

16. Perspectives and Open Points Morphology investigation with Grazing Incident Small Angle X-ray Scattering. Analysis in progress…

17. Perspectives and Open Points The presence of a double phase is affected by solvent choise… Boiling Temperature of solvent Toluene 20 nm ? Chloroform Acetone 1min, 250°C, RTP 20 nm THF PS selective PMMA selective

18. Perspectives and Open Points In very fast thermal treatment, heating and cooling ramps become relevant… No significant variation for steady state as long as 30 s. What about 5 s or 1 s of steady state? Temperature (°C) Time (s) Heating ramp Steady state Cooling ramp Heating rate (°C/s) Correlation length (nm)

19. Pubblications Conferences  Rapid Thermal Processing of self-assembling block copolymer thin films F. Ferrarese Lupi, T.J. Giammaria, M. Ceresoli, G. Seguini, K. Sparnacci, D. Antonioli, V. Gianotti, M. Laus and M. Perego. Nanotechnology, 24 (2013) 315601.  Higly ordered lamellar patterns in symmetric block copolymer thin films M.Ceresoli, F.Ferrarese Lupi, G.Seguini, K. Sparnacci, V. Gianotti, D. Antonioli, M. Laus, L. Boarino and M. Perego. submitted.  Flash Grafting of Functional Random Copolymers for surface neutralization F. Ferrarese Lupi, T.J. Giammaria, G. Seguini, M. Ceresoli, M. Perego, D. Antonioli, V. Gianotti, K. Sparnacci and M. Laus. submitted.  EPF2013 European Congress of Polymers, Pisa, June16th-21th 2013. Stabilization of mixed morphology in Block Copolymer thin films by solvent assisted thermal processing. Poster presentation

20. Thank you for your attention. Monica Ceresoli 15/10/2013 Fabrication of nanostructures by means of block copolymer based lithography

22. Technologies under study

23. Residual solvent Residual solvent locally trapped at the interface between random and block copolymer. Toluene amount in the block layer in the absence of random is 0,083 ng mm -2 nm -1. "local" toluene rich interphase.

24. Correlation length SEM images are mapped through a intensity gradient function. C. Harrison et al,,Macromolecules 33, 857-65 Gradient vector of intensity Extraction of correlation length ξ correlation function

25. How to get an effective plateau … setting an overheating in the nominal temperature, the radiative power of infrared lamps can keep the temperature costant.  This assures control on very short thermal treatments too (from minutes to seconds).  Study of the Early stages of self-assembling evolution in symmetric PS-b-PMMA thin films Optimization of RTP

26. Materials and Techniques Samples preparation Si SiO 2 Random Copolymer Neutralization of the substrate. Block Copolymer deposition. Block Copolymer Thermal treatment for self-assembling. Remotion of PMMA Acquisition of images by SEM