Polymer Matrix Effects on EUV Acid Generation

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1 Polymer Matrix Effects on EUV Acid Generation Theodore H. Fedynyshyn, Russell B. Goodman, and Jeanette Roberts # Lincoln Laboratory Massachusetts Institute of Technology # Intel Corporation The Lincoln Laboratory portion of this work was performed under a Cooperative Research and Development Agreement between and Intel Corporation. pinions, interpretations, conclusions, and recommendations are those of the authors, and do not necessarily represent the view of the United States Government. EUVL

2 Acid Generation Does the polymer matrix affect acid generation? Acid generation is the product of photon absorption and quantum yield PAG absorbance often drives the acid generation rates Sensitization of the PAG can increase acid generation rates Longer wavelength absorbers sensitize by energy transfer Electron rich polymers can sensitize by energy transfer EUV can yield Auger electrons and secondary electrons Shorter lithographic wavelengths have higher polymer absorbance Greater than 95% of energy absorbed in the polymer Polymer photochemistry is greatly increased PAG photochemistry may be influenced by polymer photochemistry Study the effect of the polymer matrix on PAG decomposition Test different polymers with different absorbances at EUV EUVL

3 Acid Generation Available acid Resist sensitivity is a convolution of many factors Acid generation efficiency Concentration of PAG Concentration of base Polymer deprotection Strength of photogenerated acid Kinetic reaction rate for polymer deprotection Polymer dissolution Concentration of protecting groups Dissolution rate of deprotected polymers In dissimilar polymer systems cannot use E 0 to predict available acid Dill s C value and quantum efficiency allow direct comparisons EUVL

4 EUV Polymer Sensitization Determine Dill C value with different polymer matrixes Employ standard addition method of Szmanda & Pawloski Requires contrast curve measurements (imaging polymers) Six resists employed for each polymer tested Level of base varied from 0.0 to 0.25 molar ratio to PAG Clearing dose (E 0 ) measured for each resist Linear relationship between base molar ratio and E 0 Slope of linear relationship gives the Dill C value Correction for resist absorbance (a) required (a = A Ln x D) C = slope x (a / (1-e -a )) EUVL

5 Measurements of Acid Generation [H + ] = [PAG]e -CE Dill s C parameter is the kinetic rate constant for photoactive species in resists C = kinetic rate constant [H + ] = concentration of acid [PAG] = concentration of PAG E = incident energy dose (exposure tool friendly) Φ = CN a hc / aλ(mw) Quantum efficiency is the ratio between acid molecules generated and number of photons absorbed (chemist friendly) N a = Avogadro number, MW = PAG molecular weight h = Planck s constant, c= speed of light a = PAG absorbance, λ = wavelength Works best if non-absorbing polymer matrix EUVL

6 EUV Polymer Sensitization Determine if EUV polymer absorbance is directly related to acid generation The polymer matrix can affect acid generation efficiency in EUV Polymer absorbance of EUV photons can generate low ev electrons Low ev electrons can convert PAG to photoacid Degree of polymer sensitization depends on energy transfer mechanism Effect should be controlled by polymer absorbance at EUV (13.4 nm) Four resist polymers selected with calculated EUV absorbences (base e) ESCAP copolymer (4.61) and terpolymer (4.34) Methacrylate copolymer (4.77) FESCAP copolymer (12.58) EUVL

7 Initial Polymers 248-nm ESCAP & FESCAP Polymers H H HST:TBA (E1) HST:ST:TBA (J) 193-nm Methacrylate Polymer & 157-nm FESCAP Polymer F 3 C CF 3 MAdMA:GBLMA (A2) HFIPST:TBA (F1) H EUVL

8 EUV Polymer Sensitization Poly-J is an ESCAP terpolymer of 65:20:15 HST:ST:TBA EUV Resist (Poly-J + DTBPI-PFBS) y = x R= Resist absorbance at 13.4 nm calculated to be 4.34 (base e) Slope of linear fit is with R =.999 Dill C calculated to be cm 2 /mj Molar Ratio H E 0 (mj/cm 2 ) EUVL

9 EUV Polymer Sensitization Poly-E is an ESCAP copolymer of 60:40 HST:TBA EUV Resist (Poly-E + DTBPI-PFBS) y = x R= Resist absorbance at 13.4 nm calculated to be 4.61 (base e) Slope of linear fit is with R =.994 Dill C calculated to be cm 2 /mj Molar Ratio H E 0 (mj/cm 2 ) EUVL

10 EUV Polymer Sensitization Poly-A2 is a methacrylate copolymer of 50:50 MAdMA:GBLMA EUV Resist (Poly-A2 + DTBPI-PFBS) y = x R= Resist absorbance at 13.4 nm calculated to be 4.77 (base e) Slope of linear fit is with R =.977 Dill C calculated to be cm 2 /mj Molar Ratio E 0 (mj/cm 2 ) EUVL

11 EUV Polymer Sensitization Poly-F is an FESCAP copolymer of 60:40 HFIPST:TBA EUV Resist (Poly-F1 + DTBPI-PFBS) y = x R= Resist absorbance at 13.4 nm calculated to be (base e) Slope of linear fit is with R =.988 Dill C calculated to be cm 2 /mj Molar Ratio F 3 C CF H E 0 (mj/cm 2 ) EUVL

12 EUV Polymer Sensitization (2006) Dill C v. Absorbance No simple relationship between polymer absorbance and EUV sensitivity for polymers Methacrylate Polymer FESCAP Polymer Is methacrylate polymer different due to possibility of polymer chain scission photochemistry? Is the aromatic polymer different due to possibility of radical stabilization? Dill C (cm 2 /mj) ESCAP Polymers Additional polymers must be investigated Absorbance (μm -1 ) EUVL

13 Aromatic Polymers H X Y ESCAP Copolymers Polymer HST TBA Poly-E Poly-E Poly-E ESCAP Terpolymers H X Y Z Polymer HST ST TBA Poly-J Poly-T Poly-D Varying the monomer ratios between hydroxystyrene, styrene, and t-butyl acrylate to determine difference in acid generation ability EUVL

14 Non-Aromatic Polymers Fluoro(meth)acrylate Polymers F 2 C CF F 2 C CF H 2 C 65 C 35 CF 3 H F 3 C H CF 3 CF 3 TFE:NbFH:TBA (F2) FUGU:MAdMA (F5) Methacrylate Polymer H EAdMA:GBLMA:HAdMA (A3) EUVL

15 EUV Polymer Sensitization Polymer Absorbance (µm -1 ) Dill C (cm 2 /mj) E 0 (mj/cm 2 ) Poly-E Poly-E Poly-E Poly-J Poly-T Poly-D Poly-A Poly-A Poly-F Poly-F Poly-F E 0 values for 0.2 molar base EUVL

16 EUV Polymer Sensitization (2006) Relationship between polymer absorbance and EUV sensitivity for acrylate based polymers Dill C v. Absorbance Methacrylate Polymer 0.2 Different relationship between polymer absorbance and EUV 0.15 sensitivity for methacrylate based polymers due to 0.1 polymer chain scission photochemistry 0.05 Presence of the aromatic 0 group may also be key Dill C (cm 2 /mj) Acrylate Polymer y = x R= y = x R= Absorbance (μm -1 ) EUVL

17 EUV Polymer Sensitization (2007) Linear relationship between (meth)acrylate level and Dill C for hydrocarbon polymers or inverse relationship with aromatic content Fluoropolymer has increased Dill C at similar acrylate levels but no linear relationship Dill C (cm 2 /mj) Dill C v. Acrylate Content Fluoroacrylate Polymer Acrylate Polymer Absorbance increase of X gives a Dill C increase of X for comparable acrylate levels 0.05 y = x R= Acrylate (%) EUVL

18 EUV Polymer Sensitization (2007) Relationship between polymer type and EUV sensitivity Linear inverse relationship between aromatic content and Dill C Fluoropolymer increase Dill C at similar aromatic content by ~0.1 Absorbance increase of ~3.0X gives a Dill C increase of ~3.3X for ESCAP v. fluoropolymer Dill C (cm 2 /mj) Dill C v. Aromatic Content Fluoroacrylate Polymer y = x R= Acrylate Polymer y = x R= Aromatic (%) EUVL

19 Polymer Properties and IMR CEFFICIENTS P TERM CNSTANT Absorbance Aromatic N trials = 12 N terms = 3 Residual SD = Residual DF = 9 R Squared = 0.945, P= *** ECHIP software final model containing only absorbance and percent aromatic terms Aromatic (%) ECHIP Predicted Dill C (cm 2 /mj) Absorbance (µm -1 ) Dill C predicted by both absorbance and aromatic content in polymer Linear model has > 99% confidence level with no interaction term EUVL

20 EUV Polymer Sensitization Apparent relationship between E 0 and Dill C Acid generation efficiency is related to resist sensitivity PAG and base amount constant for all polymers and will not affect resist sensitivity Dill C (cm 2 mj) Correlation Clearing Dose v. Dill C ESCAP Copolymer ESCAP Terpolymer Methacrylate Fluoropolymer Polymer deprotection 0.05 kinetics and dissolution kinetics will also strongly 0 influence the resist E E 0 (mj/cm 2 ) EUVL

21 EUV Polymer Sensitization Apparent power law relationship between E 0 and Dill C Dill C = constant + E 0-1 Increasing Dill C leads to a marginally decreasing increase in resist sensitivity Many other factors influence resist sensitivity Dill C (cm 2 mj) Correlation Clearing Dose v. Dill C ESCAP Copolymer ESCAP Terpolymer Methacrylate Fluoropolymer All Polymers PAG and base amounts y = * x^( ) R= Level of polymer protection Polymer deprotection and dissolution kinetics E 0 (mj/cm 2 ) EUVL

22 Proposed Sensitization Mechanism Photochemical PAG Decomposition hυ I X I X.. proton abstraction I. IH. XH X CH 3 Polymer Photochemistry leading to radical transfer CH 3. H. R Unstabilized polymer radical Stabilized polymer radical EUVL

23 Summary EUV Polymer Sensitization Polymer sensitization is important for acid generation with EUV exposure Increase in Dill C value can be up to 5 times with selected polymers Increase in resist sensitivity of up to 5 times is possible How excited would you be with a 5X increase in laser output? Polymer absorbance can be used to increase acid generation efficiency Linear relationship between polymer absorbance and Dill C value Polymer generated secondary electrons converting PAG to acid Higher polymer absorbance can be tolerated at the 32 and 22 nm nodes A 70 nm thick film give an.d. of 0.4 with fluoropolymer (A = 5.5 to 6.0) Aromatic content of the polymer will lower the Dill C value Radical stabilization of polymer generated secondary electrons Non-aromatic fluoropolymers will give the highest sensitivity EUV resists EUVL

24 Acknowledgments Support: Andrew Rudack, Matt Malloy, and Cecilia Montgomery of Sematech North for EUV exposures and measurements Materials: Dupont Electronic Polymers for supplying polymers Asahi Glass for supplying polymers Toyo Gosei Kogyo for supplying PAGs The Lincoln Laboratory portion of this work was performed under a Cooperative Research and Development Agreement between and Intel Corporation. pinions, interpretations, conclusions, and recommendations are those of the authors, and do not necessarily represent the view of the United States Government. EUVL

Screening of basic resist materials and PAGs for EUV-Lithography

Screening of basic resist materials and PAGs for EUV-Lithography 1. Int. EUVL-Symposium, Dallas, TX Klaus Lowack, Wolf-Dieter Domke, liver Kirch, Karl Kragler, Heinz-Ulrich Scheunemann* Infineon Technologies