Polymer Synthesis CHEM 421 “Organic imaging materials: a view of the future” J. Phys. Org. Chem. 2000, 13, 767 “Advances in Patterning Materials for 193 nm Immersion Lithography” Chem. Rev. 2010, 110, 321–360 “Block Copolymer Nanolithography: Translation of Molecular Level Control to Nanoscale Patterns” Adv. Mater. 2009, 21, 4769–4792 “Tech Focus – Lithography” Nature Photonics 2010, 4, Science 2008, 322, 429 (Hawker, block copolymer lithography) nphoton (EUV) More Reading Materials

Polymer Synthesis CHEM 421 Semiconductor Manufacturing

Polymer Synthesis CHEM 421 Photolithographic Process J. Phys. Org. Chem. 2000, 13, 767. Coat Exposure Develop Strip Etch Photoresist Substrate Mask h Positive Negative

Polymer Synthesis CHEM 421 Model for Constructing a Chemically Amplified Resist Levinson, Harry J. Principles of Lithography. SPIE Press, Etch Barrier Backbone Protecting Group Acidic Group

Polymer Synthesis CHEM 421 Low- and High-Activation Energy Chemically Amplified Resists Copolymer of hydroxy styrene and t-BOC protected hydroxy styrene Good hydrophilic/hydrophobic balance IBM’s Apex Resist Low activation energy, very reactive PAB below Tg IBM’s ESCAP Resist High activation energy, lower reactivity Allows for high T bake PAB above Tg removes stress removes residual solvent higher density films Low diffusion of PAG

Polymer Synthesis CHEM 421 “Transitions” in Optical Lithography 365 nm 248 nm 193 nm 157 nm E-beam X-ray EUV ?

Polymer Synthesis CHEM 421 How? R: resolution or critical dimension k1: Rayleigh coefficient of resolution Λ0: vacuum wavelength n: refractive index of the incident medium θ: angular aperture of the lens n · sin θ is also referred to as the numerical aperture (NA) of the imaging system.

Polymer Synthesis CHEM 421 Polymer Absorbtion Coefficient (157 nm) Thickness (nm) (OD = 0.4) Poly(hydrosilsesquioxane) Poly(tetrafluoroethylene) Poly(tetrafluoroethylene-co- ethylene) (30% TFE) Poly(dimethylsiloxane) Poly(vinyl alcohol) Poly(methyl methacrylate) Poly(norbornene) Polystyrene Poly(p-hydroxystyrene) Poly(p-chlorostyrene) R. R. Kunz et.al. J. Vac. Sci. Technol. B 17(6), Nov/Dec 1999 Polymeric Materials Outlook for 157 nm Resist Design

Polymer Synthesis CHEM 421 Emerging 157 nm Resist Platforms A. E. Feiring and J. Feldman, DuPont WO 00/ SO 2 OH CF 3 H. Ito, G. Walraff, et. al. IBM CH 2 C C OCH 3 O CF 3 G. Willson, UT R. Dammel, Clariant C. Ober, Cornell 157 nm 1.4 micron nm 3.1 micron nm 2.7 micron nm 2.8 micron nm 2.5 micron -1

Polymer Synthesis CHEM 421 Poly(TFE-co-NB-co-EVE) Lowers Absorbance Increases CO 2 Solubility Increases Etch Resistance Increases T g Provides Contrast Lowers Absorbance Increases CO 2 Solubility EVE is Ester Vinyl Ether

Polymer Synthesis CHEM 421 Poly(TFE-co-NB-co-EVE) TFE (mol %) NB (mol %) FG (mol %) T g (°C) Mn / MWD Liq. CO 2 Sol. 157 nm ?? 3300 / 1.47 Insol.Insol / 1.32 Insol / 1.42 Insol. To be determined

Polymer Synthesis CHEM /193 nm Photoresists Teflon® AF as Backbone Material Due to its amorphous structure and rigid backbone, Teflon® AF has unique properties that are desirable in a photoresist backboneDue to its amorphous structure and rigid backbone, Teflon® AF has unique properties that are desirable in a photoresist backbone AdvantagesChallenges very low absorbance cost of PDD monomer rigid structure (good etch resistance) need functional monomer without significantly increasing absorbance forms smooth films broad range of T g s available Tetrafluoroethylene (TFE) 2,2-Bis(trifluoromethyl)-4,5- difluoro-1,3-dioxole (PDD) Teflon® AF

Polymer Synthesis CHEM /193 nm Photoresists Absorbance at 157 nm and 193 nm Values for Teflon® AF and the CO2 synthesized copolymer are very close and well below 1  m -1 at 157 nmValues for Teflon® AF and the CO2 synthesized copolymer are very close and well below 1  m -1 at 157 nm Values at 193 nm are slightly different but both extremely lowValues at 193 nm are slightly different but both extremely low Sample (nm) 193 (nm) Teflon® AF CO 2 Synthesized Copolymer Absorbance [    m  

Polymer Synthesis CHEM /193 nm Photoresists Teflon® AF as Backbone Material Protected Functional Monomer Acidic Group PAG In order for a Teflon® AF derivative to serve as a photoresist, a functionalized monomer that can be cleaved by an acid must be incorporated into the backboneIn order for a Teflon® AF derivative to serve as a photoresist, a functionalized monomer that can be cleaved by an acid must be incorporated into the backbone After cleaving with a photo acid generator (PAG) the functional monomer will exhibit different solubility properties from unexposed regionsAfter cleaving with a photo acid generator (PAG) the functional monomer will exhibit different solubility properties from unexposed regions

Polymer Synthesis CHEM /193 nm Photoresists EVE/PDD/TFE Plackett-Burman Experiment Scheme Chose to explore Ester Vinyl Ether (EVE) as a prototype for potential EVE derived functional monomersChose to explore Ester Vinyl Ether (EVE) as a prototype for potential EVE derived functional monomers Conducted a Plackett-Burman experimental scheme varying five parameters (composition, initiator concentration, temperature, pressure and reaction time) to study the reaction of EVE with PDD and TFEConducted a Plackett-Burman experimental scheme varying five parameters (composition, initiator concentration, temperature, pressure and reaction time) to study the reaction of EVE with PDD and TFE Exp. #EVE/PDD/TFE (mol %) Initiator (mol %) Temp ( o C)Pressure (psi) Rxn Time (hr) 17/73/ /55/ /55/ /55/ /73/ /73/ /55/ /73/ poly(TFE-co-PDD-co-EVE)

Polymer Synthesis CHEM /193 nm Photoresists EVE/TFE/PDD - Absorbance Absorbance values at 157 nm increase with increasing EVE content but still remain well below 1  m  Absorbance values at 157 nm increase with increasing EVE content but still remain well below 1  m   Values at 193 nm are very low and vary only slightlyValues at 193 nm are very low and vary only slightly Sample Composition (mol %) (nm) 193 (nm) REH-004 7/73/20 EVE/PDD/TFE (Charged) REH /59/29 EVE/PDD/TFE REH /54/28 EVE/PDD/TFE VASE® Absorbance [    m   Measurements

Polymer Synthesis CHEM /193 nm Photoresists Absorbance at 157 nm and 193 nm Values for Teflon® AF and the CO2 synthesized copolymer are very close and well below 1  m -1 at 157 nm Values at 193 nm are slightly different but both extremely low Sample (nm) 193 (nm) Teflon® AF CO 2 Synthesized Copolymer Absorbance [    m  

Polymer Synthesis CHEM /193 nm Photoresists Teflon® AF as Backbone Material Protected Functional Monomer Acidic Group PAG In order for a Teflon® AF derivative to serve as a photoresist, a functionalized monomer that can be cleaved by an acid must be incorporated into the backbone After cleaving with a photo acid generator (PAG) the functional monomer will exhibit different solubility properties from unexposed regions

Polymer Synthesis CHEM /193 nm Photoresists EVE/PDD/TFE Plackett-Burman Experiment Scheme Chose to explore Ester Vinyl Ether (EVE) as a prototype for potential EVE derived functional monomers Conducted a Plackett-Burman experimental scheme varying five parameters (composition, initiator concentration, temperature, pressure and reaction time) to study the reaction of EVE with PDD and TFE Exp. #EVE/PDD/TFE (mol %) Initiator (mol %) Temp ( o C)Pressure (psi) Rxn Time (hr) 17/73/ /55/ /55/ /55/ /73/ /73/ /55/ /73/ poly(TFE-co-PDD-co-EVE)

Polymer Synthesis CHEM /193 nm Photoresists EVE/TFE/PDD - Absorbance Absorbance values at 157 nm increase with increasing EVE content but still remain well below 1  m   Values at 193 nm are very low and vary only slightly Sample Composition (mol %) (nm) 193 (nm) REH-004 7/73/20 EVE/PDD/TFE (Charged) REH /59/29 EVE/PDD/TFE REH /54/28 EVE/PDD/TFE VASE® Absorbance [    m   Measurements

Polymer Synthesis CHEM 421 “Transitions” in Optical Lithography 365 nm 248 nm 193 nm 157 nm E-beam X-ray EUV ?

Polymer Synthesis CHEM 421 Immersion: Win of 193 nm over 157 nm

Polymer Synthesis CHEM 421

Polymer Synthesis CHEM 421

Polymer Synthesis CHEM 421 EUV: 13.5 nm wavelength 38 nm: feature size can be resolved by most advanced 193 nm immersion lithography systems < 10 nm: by EUV

Polymer Synthesis CHEM 421 Technically Very Challenging!

Polymer Synthesis CHEM 421 Block Copolymer Lithography a thin film of PS-b-PMMA BCP thermally annealed to produce the PMMA cylindrical microdomains oriented normal to the surface. Exposed to UV radiation i.PMMA block is degraded ii.PS matrix is cross linked. removing the decomposition products with acetic acid nanoporous crosslinked PS templates are produced

Polymer Synthesis CHEM 421 Cross-linking units

Polymer Synthesis CHEM 421 Tri-block

Polymer Synthesis CHEM 421 E-Beam Lithography

Polymer Synthesis CHEM 421 Nanoimprint Lithography (NIL)