A comparison of electron beam lithography resists PMMA …

1 A comparison ofelectron beam lithography resistsPMMA and ZEP520 Amaterial propertiespropertyPMMAZEP520manufacturer Micro Chem (USA)Zeon Chemicals (Japan)polymerpoly methyl methacrylate1:1 co-polymer -chloromethacrylate, -methylstyrenechemical formula(C5O2H8)nC3H3O2Cl, C9H10molecular weight950,00055,000solution suspension anisoleanisoleappearanceclear liquidclear g/cm3Tg / melting point105 C105 C1, 145 C2melting point160 C?refractive index @ 600 Technical Report Oct 2010, , Quantum Wire Fabrication by E-beam Elithography Using High-Resolution and High-Sensitivity E-Beam Resist ZEP-520 , Jpn. J. Appl. Phys. Vol. 31 (1992) pp. 4508-45142chemical structurePMMAZEP3 pmma Process ConditionsSubstrate: 4 silicon wafer cleaved into 1 x1 piece, then spunCoat: pmma A6 resist 6000 RPM, 3000 RPM / sec, 60sec 180 C hot plate bake for 90 sec Thickness: 301 nm (measured on the Nanospec reflectometer)Expose: 2 nA current, 100 kV accelerating voltage, 8 nm shot pitch Dose varied for 100 nm line featuresDevelop: 1:1 MIBK:IPA immersion for 2 minutes Isopropanol immersion for 30 seconds N2blow dry4 ZEP520A Process ConditionsSubstrate: 4 silicon wafer cleaved into 1 x1 piece, then spunCoat: ZEP520A resist 5000 RPM, 2500 RPM / sec, 60sec 180 C hot plate bake for 2 minutes Thickness: 312 nm (measured on the Nanospec reflectometer)Expose.

2 2 nA current, 100 kV accelerating voltage, 8 nm shot pitch Dose varied for 100 nm line featuresDevelop: Amyl acetate immersion for 2 minutes Isopropanol immersion for 30 seconds N2blow dry5 Dose sensitivity curve dose sensitivity curve for 75 x 75 um squares ZEP520 has higher contrast (although pmma develop conditions could be modified) dose to clear ZEP520 = ~220 uC/cm2 pmma = ~270 uC/cm20500100015002000250030003500050100 150200250300350400450500dose (uC/cm2)thickness (Ang)PMMAZEP5206 SEM image of 100 nm line and uC/cm2200 uC/cm2210 uC/cm2 ZEP5207 ICP Etch Process ConditionsSubstrate: 4 SiO2 coated silicon carrier wafer resist samples (ZEP520, pmma ) mounted simultaneously on carrier wafer and etched togetherEtch: Plasma Therm ICP recipe = DKB_SI press = 5 mTorr 16 sccm Cl2 4 sccm Ar 50W RIE power 200W coil power etch time = 30 sec8 Post etch cross section comparison 100 nm line and space x-section images post silicon ICP etching resist still remainingPMMA, uC/cm2 ZEP520, 200 uC/cm29etch rate and selectivity datafirst etch runsecond etch runcomparison of Si to resist etch A6 ZEP520r e si stselectivity (Si.)

3 Resist)first etch runsecond etch runresistpre-etch resist thickness (Ang)post-etch thickness (Ang)etched resist (Ang)resist etch rate (Ang/sec)etched silicon (Ang)silicon etch rate (Ang/sec)selectivity (Si to resist) pmma resist thickness (Ang)post-etch thickness (Ang)etched resist (Ang)resist etch rate (Ang/sec)etched silicon (Ang)silicon etch rate (Ang/sec)selectivity (Si to resist) pmma