Impact of Polymerization Process and OOB on Lithographic Performance of a EUV Resist

Transcription

1 Impact of Polymerization Process and B on Lithographic Performance of a EUV Resist Vipul Jain* a, Suzanne M Coley a, Jung June Lee b, Matthew D Christianson c, Daniel J Arriola c, Paul LaBeaume a, Maria E Danis a, Nicolas rtiz a, Su-Jin Kang a, Michael D Wagner d, Amy Kwok a, David AValeri a, James W Thackeray a a Dow Electronic Materials, 455 Forest Street, Marlborough, MA USA 1752 b The Dow Chemical Company, 736 Back-Seok Dong, Cheonan, Korea c The Dow Chemical Company, Midland, MI USA d The Dow Chemical Company, 257 Fuller Road, Suite 22, Albany, NY USA 1223 ABSTRACT Several approaches have been used to minimize LWR in advanced resists Various polymer and matrix properties, such as polymer molecular volume and free volume fraction, polymer dissolution, impact of activation energy of the deprotection reaction and distribution of small molecules in the polymer matrix have been shown to influence the functional behavior of the resist We have developed polymerization methods to improve the incorporation and homogeneity of monomers, including PAG monomer, in an EUV resist polymer Further, we report on use of a new cation which imparts reduced B character and a 3% improvement in LWR for a 28nm L/S feature with sensitivity of 1mJ/cm 2 versus a control containing the TPS cation Additionally this new material is capable of 21nm resolution We also tested the new cation for outgassing by RGA and observed a 6% reduction in outgassing versus a TPS control Keywords: EUV lithography, photoresist, polymer bound PAG (PBP), radical polymerization, kinetic modeling, polymer process optimization, B, outgassing 1 INTRDUCTIN There are many unique resist design considerations when building EUV resist materials The ionizing radiation of EUV photons at 134nm provides a high energy photon (~92eV) which quickly generates secondary electrons that are captured by the photoacid generator 1,2 ne must consider absorption and density of the resist material to EUV energies 3-6 Also, one must consider the PAG selection and the activation energy of the protecting group 7 In this paper, we will focus on the synthesis of methacrylate-based polymer-bound PAG [PBP] polymers as described in Figure 1 In earlier work 8,9, we reported the role of the protecting group, EUV sensitization, and the fundamental performance differences between a PBP system versus the traditional PAG blended resist system In this paper, we will focus on reaction kinetics of the individual resist monomers, optimization of PAG incorporation into the polymer, and finally optimization of the PAG cation to reduce the effects of out-of-band radiation [B] Numerous papers have been published on the effect of B radiation on EUV resist materials 1 ne of the worst PAGs for B is the ubiquitous triphenyl sulfonium cation [TPS] which is extremely sensitive to 193nm and 248nm wavelength light Through systematic PAG variation we have been able to reduce the sensitivity to B substantially while maintaining similar EUV sensitivity In concert with the aforementioned efforts, is the importance of EUV outgassing products from the resist cation Again, numerous papers have been published recently on the high outgassing rate for TPS cation and in particular large amounts of diphenyl sulfide and benzene 11 This paper will show that the low B sensitive PAG has also reduced outgassing Finally, we will show the EUV lithographic capability of these resists on the EMET tool in Albany *vipuljain@dowcom; phone ; fax Extreme Ultraviolet (EUV) Lithography II, edited by Bruno M La Fontaine, Patrick P Naulleau, Proc of SPIE Vol 7969, SPIE CCC code: X/11/$18 doi: 11117/ Proc of SPIE Vol

2 LG F F ESM F F S+ S 3 Figure 1 Typical EUV methacrylate-based PBP system with a covalently attached anion (LG Leaving Group, ESM - Electron Sensitizer Monomer) 2 RESULTS AND DISCUSSIN 21 Determination of monomer reactivity ratios using 1 H and 19 F spectroscopy Measurement of monomer reactivity ratios and polymerization kinetics is necessary to develop a polymerization procedure in which polymer with a consistent composition and molecular weight is generated throughout the entire reaction time For example, if one constituent monomer is more reactive than the others, its concentration will decrease relative to the other monomers throughout the polymerization and its incorporation in the polymer will decline unless a process is adopted to compensate for this behavior For these instances, a simplified reactivity ratio model can be employed wherein there is only one reactivity ratio for each monomer in a given system The reactivity ratios 12 are defined as k rx k px p1 Where k px is the propagation rate constant for the xth monomer such that the rate of the xth monomer disappearing is d[ M x ] k px[ M x ][ P ] dt Where, M x is the monomer and P is the propagating radical chain The reactivity ratios were determined by fitting the model to time dependent concentrations obtained through 1 H NMR experiments To illustrate our method, we show results for a polymerization of monomer 1 (Leaving Group - LG), monomer 2 (lactone), monomer 3 (ESM), and monomer 4 (PAG 1) with V-61 radical initiator in a 2:1 mixture of acetonitrile and tetrahydrofuran (Figure 1) A NMR tube was charged with all four monomers, the radical initiator, and deuterated polymerization solvent such that the monomer and initiator concentrations were similar to typical polymerization conditions The tube was placed into a preheated NMR probe (6-8 C) and the resulting batch polymerization was followed by 1 H NMR spectroscopy The vinylic protons for all four monomers were distinct in the 1 H NMR spectrum, so the concentration of each monomer was determined with time In addition, the unreacted V-61 radical initiator was observed in the 1 H NMR spectrum, so the initiator decomposition was monitored simultaneously Also, 19 F NMR spectra were acquired between the 1 H NMR spectra to follow the conversion of the monomer 4 (PAG 1) independently Examples of the modeled monomer concentrations fit to the concentrations measured by NMR spectroscopy are shown in Figure 2 Table 1 summarizes the reactivity ratios of these monomers, determined at three different polymerization temperatures Proc of SPIE Vol

3 && Monomers Monomers : : :' Monomers 3 4! I!! time in seconds time in seconds tieeieseoonds Figure 2 Fits (lines) of modeled monomer concentrations to measured concentrations throughout polymerizations at 6 C (left), 7 C (center), and 8 C (right) Table 1 Relative reactivity ratios for monomer 1, monomer 2, and monomer 4 versus monomer 3 (rate = 1) from best fits to the 1 H NMR data at 6 C, 7 C, and 8 C in acetonitrile/thf using V61 initiator Monomer 6 C 7 C 8 C The largest reactivity difference is monomer 4, reacting twice as fast as monomer 3 at 6 C Thus, the development of a polymerization process wherein all four monomer concentrations remain constant throughout the reaction should be possible As expected, the reactivity ratios approach unity with increased polymerization temperature However, a comparison of monomer 2 and monomer 4 shows that the magnitude of change is not the same for every monomer At low temperature monomer 4 has the fastest propagation rate of the monomers, but at higher temperatures monomer 2 becomes the fastest propagating monomer This result highlights the importance of determining reactivity ratios under the same conditions as the polymerization in order to provide a scaffold for process development Reactivity ratios of the monomers, with respect to Monomer 3, were also determined for Polymer 2 (Figure 3) containing PAG 2 monomer at 67 C and 75 C The polymerizations were performed at 67 C and 75 C in acetonitrile/thf and ethyl lactate/cyclohexanone, respectively using V-65 initiator The reactivity ratios were determined by fitting the model to time dependent concentrations obtained through HPLC (residual monomer analysis) Monomer 2 was the fastest propagating monomer at 75 C and has substantially reduced reactivity at 67 C (Table 2) PAG monomer has the smallest reactivity ratio at lower temperature and could thus result in residual PAG monomer in the resist formulation if the polymerization is done at these temperatures For the PBP system, it is critical to avoid residual PAG monomer in the resist to limit acid diffusion during the PEB step Figure 3 EUV polymer 2, containing stonger sulfonium anion monomer (LG: Leaving Group, LA: Lactone: ESM: Electron Sensitizer Monomer) Proc of SPIE Vol

4 Table 2 Relative reactivity ratios for monomer 1, monomer 2, and monomer 5 vs monomer 3 (rate = 1) at 67 C and 75 C The polymerizations at 67 C and 75 C were run in acetonitirle/thf and ethyl lactate/cyclohexanone, respectively V-65 was used as an initiator at both temperatures Monomer 67 C 75 C Polymer process optimization effects on PAG monomer incorporation Several platforms such as PBPs, PHS systems, molecular glasses and hybrid systems are being considered by various resist vendors worldwide 13 PBP systems are currently one of the most promising candidates to print sub 16nm node features However, continuous improvement is still needed to meet the stringent RLS requirements set forward for patterning EUV resists It is expected that EUV resists must simultaneously pattern 22nm half pitch, with an LWR less than 18 nm, and a sensitivity of 1-15mJ/cm 2 In the case of the PBP system, these requirements could potentially be met by varying monomer composition, monomer distribution, molecular weight, choice of the PAG, leaving group and/or ESM monomer A more uniform PAG monomer distribution along the polymer chain should help in achieving an EUV resist with reduced likelihood of chain aggregation and a more uniform dissolution rate after exposure/peb and hence improved LER/LWR 14 Another important aspect relating to the polymer homogeneity is the variation in Molecular weight (Mw) and polydispersity (PDI) during the polymerization process Resist polymers with a wider PDI may lead to chains with very different dissolution rates A controlled PDI would thus result in a consistent dissolution rate of the resist during the development step and may help in reducing defects In order to explore the effect of monomer distribution on lithographic performance, five polymers consisting of monomer 1, monomer 2, monomer 3 and monomer 5 (Figure 2) were synthesized using different semi batch processes as described in Table 3 This was achieved by altering the reaction temperature, reaction concentration, feed rates and amounts/composition of the heel charge Table 3 Description of polymerization processes -4 Process Reaction Feed solids Feed time Heel charge Hold time temperature ( o C) 67 1x 1x 1x 1x x 2x 1x 2x x 2x 1x 1x x 2x 6x x 2x 6x 1x Each process variation contributed an incremental improvement with respect to increasing yields, consistent monomer incorporation, lower residual PAG (Table 4), tighter PDI distribution (Figure 5) and ease of scale up in going from version to version 4 process Aliquots from the reaction mixtures were collected at various time intervals Each aliquot was analyzed through HPLC (residual monomers) and GPC (Molecular weight) Because the PAG monomer contains both the anionic and cationic species, the peak corresponding to the anionic part was only analyzed to determine the amount of un-reacted monomer The peaks for other monomers were well separated and used to determine the amount of un-reacted monomer Since the feed rates, volumes and feed times of each monomer were known, the molar concentration of each monomer was thus calculated through mass balance The cumulative polymer composition (bulk polymer composition), defined as the composition of the polymer with respect to various monomers at a given time, was plotted as a function of reaction time (Figure 4a and b) for the version and version 4 process The molar concentration of residual PAG as a function of reaction time was also plotted for version and version 4 process as shown in Figure 4c Proc of SPIE Vol

5 Version through version 3 process led to polymers with varying levels of monomer incorporation either at the beginning or towards the end of the reaction As shown in Figure 4a, the cumulative polymer composition for version process shows inconsistent monomer incorporation at the early stages of the reaction In version process (along with version 1 and 2 process), due to a very small heel charge, there is a larger temperature variation expected at the beginning of the reaction which would lead to a significantly different reactivity ratios of the monomers and therefore a very different polymer composition at the onset of the reaction We also observed a wider PDI for version process which is attributed to a poor temperature control in the reaction vessel during the first hour of the reaction prior to attaining an equilibrium state (Figure 5) I I 7 4 os,4 3,2 1 a 6 (4a) S U (4b) a -U U U U S U 4 I Monoinm I Mmiornml I Moirnrm 2 A P,Imouim 3 2 IAI( 3 a A A S 3 Ponon,mS - x ) X )( )( X ix x X X 13m 1mW 6 C a C 5 to 3 In U U U V!%1li UVmcon I Tim, U U Figure 4: Cumulative polymer composition with respect to various monomers as a function of polymerization time scale for version (4a) and version 4 process (4b) Residual concentration of PAG monomer in version and version 4 process (4c) after polymerization 3S z is Vmcion 4 Tin, (mm) Figure 5 PDI of polymers made through version and version 4 process Based on the residual monomer data and kinetic models obtained from version through version 3 processes, an optimal heel charge, reaction concentration, temperature and feed rates were determined and used in the optimized version 4 Proc of SPIE Vol

6 process Version 4 process shows a more uniform bulk composition through the course of the reaction The polymer made with process 4 has consistent monomer incorporation along with minimal variation in PDI throughout the polymerization (Figure 4b & 5) and yielded a polymer with lower residual PAG monomer (Table 4) As can be seen in Figure 4c, altering the reaction conditions helped us attain polymers with very low residual PAG monomer at the end of the reaction using an optimized process Table 4 Summary of results for polymer processes -5 Residual PAG amounts are normalized to version 4 process Process Isolated polymer yield Residual PAG 65% % % % % 1 23 ptimization of PAG cation for reduced outgassing and improved B Polymer process optimization for polymer 2 (Versions - 4) did not yield the expected improvement in RLS properties, specifically, there was no clear trend showing reduced LWR as the polymer process moved from to 4 Since polymer process optimization with a TPS containing PAG monomer did not yield a satisfactory result, we next looked at altering the PAG monomer cation as a potential method of performance improvement EUV sources emit a range of wavelengths other than EUV, collectively referred to as out-of-band radiation (B) 15 The EUV optics reflect this B radiation on to the wafer plane, resulting in undesirable exposure of the resist and a reduction in image contrast The TPS cation imparts excellent EUV sensitivity to resists Unfortunately, it is also extremely sensitive to longer exposure wavelengths, such as 193nm and 248nm, and as a result EUV resists utilizing the TPS cation are strongly impacted by B radiation It would be advantageous for a cation to have good sensitivity to EUV radiation and limited sensitivity to longer exposure wavelengths Polymer 3 was made by the version 4 process described above, using monomer 6, containing a modified cation (X + ) (PAG 3, Figure 6) instead of monomer 5, containing TPS cation (PAG 2, Figure 3) Figure 6 EUV polymer 3, containing improved B cation Introduction of PAG 3 cation imparts improved B to polymer 3 compared to polymer 2 used as a reference B performance can be estimated by the ratio of E at EUV and E at a longer wavelength, such as 193nm and 248nm A lower ratio indicates a better B characteristic Polymer 3 has a E EUV /E 248 ratio of 2, which is 35x lower than that of polymer 2, consisting of TPS cation The improved B property of PAG 3 is even better at 193nm wavelength, where the E EUV /E 193 ratio is 5 times lower for polymer 3 versus polymer 2 (TPS) (Figure 7) The B impact on pattern fidelity can be directly seen in the x-section SEM comparison of polymer 2 and polymer 3 (Figure 8) Polymer 2 shows substantial top-profile erosion, while polymer 3 shows a much smoother feature, with substantially less erosion Furthermore, based on masking linearity, polymer 3 has been shown to be capable of 21nm resolution (Figure 9) Polymer 3 also shows a good process window at 22nm line/space under dipole illumination LWR of less than 55nm was observed over a 28nm focus range with a 16% exposure latitude for the resist utilizing polymer 3 (Figure 1) Proc of SPIE Vol

7 2 E 15 >- i W 5 LU 4TPS --low 1% catioti 1 2 waviength (rim) Figure 7 E comparison of polymer 2 (TPS cation) and polymer 3 (low B cation) at 3 exposure wavelengths (134nm, 193 nm, and 248nm) Dose = 99mJ, 28nm 1:1 Dose = 998mJ, 28nm 1:1 269nm measured, LWR = 58 nm 261nm measured, LWR = 42 nm ` Figure 8 SEM comparison between polymer 2 (left) and polymer 3 (right) at EUV exposure (Quad illumination) ti1t -I TT - -'I Figure 9 Polymer 3 showing 21nm resolution capabilities through mask linearity (Dipole illumination) 22nm CD 22nm LWR E IbM la_a 5 t4m -12l mj 12- BmJ 135 mj el mj l5 a mj E II4mJ I2I mj I2SmJ I35 mj 142 mj 14 9 mj Foous(um) Foous(um) Figure 1: Process window and LWR variation on Polymer 3 at 22nm CD (Dipole Illumination) Proc of SPIE Vol

8 utgassing is another EUV resist performance characteristic greatly influenced by the identity of the PAG cation The TPS cation has been shown to produce volatile photolysis products (benzene and diphenylsulfide) during EUV, 193 and 248nm exposure 11 Because the EUV exposure takes place in a vacuum, the EUV optics are at greater risk of contamination than those of longer wavelength exposure tools Thus, a cation with a much lower tendency to produce volatile organic photolysis products is more desirable Polymer 2 and polymer 3 were tested for outgassing by Residual Gas Analysis (RGA) The results show that the low B cation of polymer 3 reduces outgassing by greater than 6% versus the TPS cation (Figure 11) 11 I 8 ' 4 2 potytier 2 polymer 3 relativerga Figure 11 Relative outgassing data for polymers 2 and 3; 35-2 amu excluding 44 amu 3 CNCLUSINS We have shown improvements in monomer incorporation using kinetic modeling for a four monomer radical polymerization system containing a polymerizable PAG Process improvements resulted in polymers with more uniform monomer incorporation, better Mw control and lower residual monomers Additionally, we showed that optimization of the PAG monomer cation to a species with improved B characteristics resulted in a EUV resist with 3% improvement in LWR (28nm hp) and 21nm resolution capability Furthermore, we showed that this improved B cation also imparted a 6% reduction in outgassing as measured by RGA versus the standard TPS cation 4 EXPERIMENTAL The monomers were either purchased from commercial sources or prepared in house PBP methacrylate polymers were synthesized as described below Monomer 1 refers to leaving group monomer, Monomer 2 refers to lactone, Monomer 3 is the electron sensitizing monomer and Monomer 4, 5 and 6 represents the PAG monomer Polymerization and precipitation solvents were purchased from commercial sources and used without further purification Final polymer and/ or polymer aliquots were analyzed by NMR ( 1 H, 13 C and 19 F) GPC and HPLC Monitoring polymerizations by 1 H, 19 F and 13 C NMR Spectroscopy: Reactivity ratios of the various monomers were determined using 1 H and 19 F NMR by dissolving the various monomers in acetonitrile-d 3 /THF-d 6 (2/1 v/v) in a nitrogen atmosphere dry box The mixture was stirred to form a clear, colorless solution, loaded into a 5 mm NMR tube, and stored in a -4 C freezer until use The probe of a Varian 4-MR NMR spectrometer was heated to 6 C, and the sample was inserted into the spectrometer Within three minutes, an arrayed data collection was started (one 1 H spectrum every 8 s with a 19 F spectrum interwoven between each 1 H spectrum) The reaction was monitored for 15 hours The NMR integrations were converted to concentrations by assuming the initial PAG 1 (Monomer 4) signal was equal to the gravimetric concentration Signature peaks for other monomers were used for quantification The residual PAG amounts were quantified using 19 F NMR spectroscopy The polymers were dissolved in acetone d 6 at 5-7 weight% A 3MHz Proc of SPIE Vol

9 Varian NMR was used to evaluate free and bound PAG monomer Typically, the Fluorine on the un-reacted monomer appears as a sharp singlet at 156 ppm (PAG 1) A broad peak is seen for the fluorine on the PAG bound to the polymer at 152 ppm The relative integration between the two peaks was used to determine the % residual PAG The polymer compositions of the final polymers were evaluated using quantitative 13 C NMR Typically 25 weight % solution of the polymer was prepared in acetone d 6 with chromium acetyl acetonate and transferred to a 5mm NMR tube A 15 hour run in a 3 MHz Varian NMR at 21 C was used to determine the molar composition of the polymer with respect to each individual monomer Determination of instantaneous polymer composition using HPLC: Aliquots from reaction mixtures were collected at timed intervals and analyzed for un-reacted monomer content using an Agilent 11 HPLC, attached with an ACE C18 column at 214 nm Molecular weight determination: Molecular weight on reaction aliquots and final polymers were determined (relative to polystyrene) using a Waters GPC employing a mixed bed column with a dual detector Resist formulations: Various polymers were formulated for positive tone EUV lithographic evaluation at EMET Albany A typical resist formulation was obtained by dissolving the polymer in ethyl lactate and hydroxymethyl isobutyrate Base quencher and surface leveling agent were added to the polymer solution The resist solution was passed through a 1um PTFE filter Resist formulations were spun cast on 2mm Si wafers coated with 25nm of underlayer to a resist thickness of 6nm The films were annealed at 13 C for 9 seconds and exposed to EUV light source (NA=3; Quad; 22σ/ 68σ ) using both an open frame array in order to obtain a contrast curve and through a binary mask containing dark field line/space patterns The exposed wafers were baked at 1 C for 6 seconds and then developed with 26N tetramethylammonium hydroxide solution for 6 seconds Synthesis of various polymers (polymer 2 and 3) using version through version 4 process: Monomers 1-4 were dissolved in the reaction solvent at a desired concentration to target a 2g yield Depending on the process used, an appropriate amount of heel charge was made either consisting of just the solvent or monomers and solvent mix nce an equilibrium temperature was attained, the feed solution was fed into the reactor Feed time/rate and hold time were altered depending on the process used The reaction mixtures were cooled to room temperature followed by precipitation All polymers were precipitated twice followed by vacuum drying at 45 C for 8 hours to yield a white flaky powder The isolated polymer was analyzed by GPC (Mw), 19 F NMR (residual PAG) and 13 C NMR (bulk polymer composition) REFERENCES [1] Kozawa T, Saeki, A, Tagawa S, Modeling and simulation of chemically amplified electron beam, x-ray and EUV resist processes, J Vac Sci Technol B, 22(6), (Nov/Dec 24) [2] Yamamoto H, Kozawa T, Nakano A, kamoto K, Tagawa, S, Ando T, Sato M, Komano H, Dependence of acid generation efficiency on the protection ratio in chemically amplified electron beam, x-ray and EUV resists, J Vac Sci Technol B, 22(6), (Nov/Dec 24) [3] Yamaguchi, T, Yamazaki, K, Namatsu H, Molecular weight effect on line-edge roughtness, Proc SPIE, 539, (23) [4] (a) Chandhok, M, Cao, H, Yueh, W, Gullikson, EM, Brainard, RL, Robertson, SA, Proc SPIE, 5374, 861 (24); (b), Matsuzawa N N, Mori S, Yano, E, kazaki, S, Ishitani, A, Dixon, D A, Theoretical calculations of photoabsorption of molecules in the vacuum ultraviolet region, Proc SPIE, 4343, 278 (21); (c) Henke L, et al, Atomic Data and Nuclear Data Tables, 54 (2) 181 (1993); Dai, J, ber C K, Proc SPIE, 5376, 58 (24) [5] (a) Kwark Y J, Bravo-Vasquez J P, ber C K, Cao, H B, Deng H, Meagley, R, Novel Silicon-containing Polymers as Photoresist Materials for EUV Lithography, Proc SPIE, 539, (23); (b) Bravo-Vasquez, J P, Kwark Y J, ber C K, Cao, H B, Deng H, Meagley, R, Silicon Backbone polymers as EUV Resists, Proc SPIE, 5376, (24); (c) Kwark Y J, Bravo-Vasquez, J P, Chandhok, M, Cao, H, Deng, H, Gullikson, E, ber, C K, Absorbance Measurement of Polymers at Extreme UV Wavelength: Correlation between Experimental and Theoretical Calculations, J Vac Sci Tech B, 24(4), (26) Proc of SPIE Vol

10 [6] Chandhok, M, Cao, H, Yueh, W, Gullikson, E, Brainard, R L, Robertson, S, Techniques for directly measuring absorption at EUV wavelength, Proc SPIE, 5374, (24) [7] Foucher J, Pikon, A, Andes, C, Thackeray, J W, Impact of Acid Diffusion Length on Resist LER and LWR measured by CD-AFM and CD-SEM, Proc SPIE, 6518, 65181Q Q (27) [8] Van Steenwinckel, D, Lammers, J, Koehler, T, Brainard, R L, Trefonas, P, Resist effects at small pitches, J Vac Sci Technol B, 24(1) (26) [9] (a) Thackeray, J W, Nassar, R A, Brainard, R L, Goldfarb, D, Wallow, T, Wei, Y, Mackey, J, Naulleau, P, Pierson, B, Solak, H H, Chemically amplified resists resolving 25 nm 1:1 line: space features with EUV lithography, Proc SPIE, 6517, (27) (b) Thackeray J W, Nassar, R A, Spear-Alfonso, K, Brainard, R L, Goldfarb, D, Wallow, T, Wei, Y, Montgomery, W, Petrillo, K, Wood,, Koay C S, Mackey J, Naulleau, P, Pierson, B, Solak, H, Pathway to sub-3 nm Resolution in EUV Lithography, J Photopoly Sci Tech, 2 (3), (27) [1] (a) Roberts J M, Bristol, R L, Younkin, T R, Fedynyshyn, T H, Astolfi, D K, Cabral A, Sensitivity of EUV resists to out-of-band radiation, Proc SPIE, 7273, 72731W (29) (b) Mbanaso C, Denbeaux G, Dean, K, Brainard, R L, Kruger, S, and Hassanein, E, Investigation of sensitivity of extreme ultraviolet resists to out-ofband radiation, Proc SPIE, 6921, 69213L (28) [11] (a) Pollentier, I, Goethals, A M, Gronheid, R, Steinhoff, J, Van Dijk, J, Characterization of EUV optics contamination due to photoresist related outgassing, Proc SPIE 7636, 76361W (21) (b) Kobayashi, S, Santillan, J J, izumi, H, Itani, T, EUV resist outgassing quantification and application, Proc SPIE, 7273, 72731P (29) (c) Antohe A, Mbanaso, C, Fan, Y J, Yankulin, L, Garg, R, Thomas, P, Denbeaux, G, Piscani, E C, Wuest, A F, EUV resist outgassing: scaling to HVM intensity, Proc SPIE, 7271, (29) (d) Tagawa, S, Nagahara, S, Iwamoto T, Wakita, M, Kozawa, T, Yamamoto, Y, Werst D, and Trifunac, A D, Radiation and photochemistry of onium salt acid generators in chemically amplified resists, Proc SPIE, 3999, 24 (2) [12] dian G, Principles of Polymerization, 4 th Ed; Wiley-Interscience, (24) [13] Koh, C, Georger, Ren, J L, Huang, G, Goodwin, F, Wurm, S, Ashworth, D, Montgomery, W, Pierson, B, Park, J, Naulleau, P, Characterization of promising resist platforms for sub-3-nm HP manufacturability and EUV CAR extendibility study Proc SPIE, 7636, 76364/1 (21) [14] Kozawa, T, Yamamoto, H, Tagawa S, Effect of inhomogeneous acid distribution on line edge roughness - relationship to line edge roughness originating from chemical gradient, J Photopoly Sci Tech, 23 (5), (21) [15] (a) George S A, Naulleau, P, Rekawa, S, Gullikson, E, Kemp, C D, Estimating the out-of-band radiation flare levels for extreme ultraviolet lithography, J Micro/Nanolith MEMS MEMS, 8, 4152 (29); (b) Lorusso, G F, Roey, F V, Hendrickx, E, Fenger, G, Lam, M, Zuniga, C, Habib, M, Diab, H, Word J, Flare in extreme ultraviolet lithography: metrology, out-of-band radiation, fractal point-spread function, and flare map calibration, J Micro/Nanolith MEMS MEMS, 8, 4155 (29) Proc of SPIE Vol