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 Important Properties of a Photoresist Resist Thickness (etch resistance)Resist Thickness (etch resistance) Solubility for deposition/developmentSolubility for deposition/development WettabilityWettability Lithographic performanceLithographic performance –Sensitivity, contrast Transparency (more important for 193 nm and beyond)Transparency (more important for 193 nm and beyond)

Polymer Synthesis CHEM 421 Optics of Imaging R = resolution = smallest feature size R  / NA is the wavelength of light NA is the numerical aperture (a function of the optics) Wavelength Wavelength 365 nm 248 nm 193 nm 157 nm Notation Notation i-line DUV 193 nm 157 nm Source mercury KrF ArF F 2 excimer Source lamp excimer excimer laser laser laser Feature Size Feature Size 365+ nm nm nm* nm*

Polymer Synthesis CHEM 421 G- and I-line Resists Novolac resinNovolac resin –Base-soluble positive resist (TMAH) –Variety of structures and MW’s Diazonapthaquinone (DNQ)Diazonapthaquinone (DNQ) –Photoactive compound (Wolfe Rearrangement) –Inhibits base-dissolution of novolac h -N 2

Polymer Synthesis CHEM 421 “Transitions” in Optical Lithography 365 nm 248 nm

Polymer Synthesis CHEM 421 Chemical Amplification DUV exposure generates catalytic amount of acid from a photoacid generator (PAG)DUV exposure generates catalytic amount of acid from a photoacid generator (PAG) 1-2 min PEB to trigger deprotection1-2 min PEB to trigger deprotection Catalytic chain length is extremely longCatalytic chain length is extremely long –About carbonate cleavages per proton J. Phys. Org. Chem. 2000, 13, 767. Acc. Chem Res. 1994, 27, 150.

Polymer Synthesis CHEM 421 Challenges with Chemical Amplification What if trace amounts of base (NMP solvent) was found in the air in a FAB?What if trace amounts of base (NMP solvent) was found in the air in a FAB? Levinson, Harry J. Principles of Lithography. SPIE Press, Catalyst susceptible to poisoning by atmospheric basesCatalyst susceptible to poisoning by atmospheric bases

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

Polymer Synthesis CHEM 421 Absorption of Resins Absorption Coefficient (micron -1 ) Wavelength (nm) Poly(p-hydroxy styrene) Polyacrylate Optimal range

Polymer Synthesis CHEM 421 Design Criteria for 193 nm Resists Optical transparency Hydrophilicity High Tg ( °C) Good etch resistance Easily blocked hydroxyl group

Polymer Synthesis CHEM 421 Photoresists for 193 nm Lithography Extremely transparent at 193 nm Tunable composition Property diversity Good hydrophilicity High activation energy cleavable group Easily synthesized But poor etch resistance…

Polymer Synthesis CHEM 421 Photoresists for 193 nm Lithography Dry etch resistance & transparency Cleavable group Hydrophilicity

Polymer Synthesis CHEM 421 Photoresists for 193 nm Lithography AT&T / Lucent / Agere

Polymer Synthesis CHEM 421 “Transitions” in Optical Lithography 365 nm 248 nm 193 nm 157 nm Absorption at 157 nm??!!

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 421 Bilayer Resist Processes Levinson, Harry J. Principles of Lithography. SPIE Press, 2001.

Polymer Synthesis CHEM 421 Top-Surface Imaging Levinson, Harry J. Principles of Lithography. SPIE Press, 2001.

Polymer Synthesis CHEM 421 Comparisons Spin coating Expose Develop 1 st Spin coating 2 nd Spin coating Expose Develop O 2 - RIE Spin coating Negative Exposure Single Layer Resist Top-Surface Imaged Resist Bi-Layer Resist O 2 - RIE Silylate

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 “Advances in Patterning Materials for 193 nm Immersion Lithography” Chem. Rev. 2010, 110, 321–360 “Organic imaging materials: a view of the future” J. Phys. Org. Chem. 2000, 13, 767 More Reading Materials