Comparative Study of Binary Intensity Mask and Attenuated Phase Shift Mask using Hyper-NA Immersion Lithography for Sub-45nm Era

Transcription

1 Comparative Study of Binary Intensity Mask and Attenuated Phase Shift Mask using Hyper-NA Immersion Lithogr for Sub-45nm Era Tae-Seung Eom*, Jun-Taek Park, Sarohan Park, Sunyoung Koo, Jin-Soo Kim, Byoung-Hoon Lee, Chang-Moon Lim, HyeongSoo Kim, and Seung-Chan Moon Hynix Semiconductor Inc. Semiconductor Outline 1. Characterization of Hyper NA Polarized Imaging a. Merit of Polarization b. Transmittance Change for Polarization State c. Comparison of Att.PSM and BIM. Experimental Results a. Simulation & Experimental Set up b. Comparison of Image Contrast for Mask Structure c. Experimental Verification for 3 Dimensional Mask Effect d. 1.35NA Polarized Imaging of 44nm DRAM Cell for several Mask Structure (Isolation Pattern & Contact Hole Pattern) e. OPE Change by Pellicle Interference Effect 3. Conclusion 1 1

2 Limit of conventional lithogr From 3nm node, completely new technology should be required such as EUV and DPT Water immersion ArF, the last conventional lithogr technology standing, will have max. 1.35NA tool Hence, capability of 1.35NA ArF will decide the limit for conventional lithogr 1.35NA ArF: Last node of ArF water immersion Litho k1 criteria Resolution Limit How much the Polarization Helps Unpolarized vs. Polarized Lithogr 1D Pattern Simulation with in-house tool D Pattern Contrast Scalar Vector TE Unpolar N.A. Contrast Scalar Vector TE Unpolar N.A. Polarized illumination can guarantee better image contrast 3

3 Mask 3D effect should be considered 4 Mask Pattern Size (nm) Litho 1.35NA Exposure Wavelength ArF 193nm As pattern size on mask decreases to the level of λ, Mask 3D effect gets significant. 4 Mask Structure Effect on Polarization.8 Mask Incident light Mask Pattern Att.PSM BIM ransmittance (A.U.) Tr ansmittance (A.U.) TM( ) )polarization TE(//) polarization Pattern size(1x, nm).6 As pattern size on mask decreases to the level of λ, specific polarization direction gets transmitted higher than others. Preferred polarization direction is different by different mask stacks used. Tra TM( ) polarization TE(//) polarization Pattern size(1x, nm) 5 3

4 Degree of Polarization (PSM vs. BIM) Simulation w/ G-Solver Incident Angle 18 (1.35NA Immersion).6 DOP Half Pitch (nm) th order PSM 1 st order PSM th order BIM 1 st order BIM Oblique incidence gives different DOP behavior to normal incidence and 1st order diffraction is different from th order. 6 Image Contrast considering Polarization Crosspole Dipole Amplitude of th and 1 st order diffracted light; A and A 1 A = Mag A = Mag 1 zero first order order = = [ 1 + T ] [ 1 + T ] ( s / p) sin ( πs/p) π T : Transmittance of Pattern s : space size, p : pitch size r : ratio of captured 1 st order (1 st order efficiency) Unpolarized Case Scalar model ra A Contrast = A + 1 ra1 Polarized Case Vector model Crosspole Contrast = A _ TM ra _ TE + A T A _ TE 1_ TE + ra 1_ TE I(x) Dipole Contrast = ra A _ TE _ TE A + ra 1_ TE 1_ TE 7 4

5 Experimental Exposure ArF 1.35NA Immersion Scanner Illumination Resist Mask Simulation Pattern Size Crosspole and Dipole w/ Polarization ArF.1 μm thickness on Organic BARC 6% Att.PSM and 3 Types of BIM HOST (Diffused Aerial Image Model) EM-Suite (rigorous EMF Simulation) 38nm ~ 5nm Line & Space 44nm DRAM Isolation & Contact Hole Patterns 8 Mask Structure for Experiment (a) ArF Att.PSM Shifter (MoSi) : 68 (c) Thin Cr BIM Cr : 59 (b) Thick Cr BIM Cr : 13 (d) Multi Layer BIM Cr : 74 /MoSi : 93 Quartz Shifter (MoSi) Cr 9 5

6 Image Contrast on Mask Bias 1. 4nm Half Pitch 1. 44nm Half Pitch Contrast rast Contr Mask Bias (nm) nm Half Pitch Mask Bias (nm) Contrast Mask Bias (nm) ArF Att.PSM Thick Cr BIM Thin Cr BIM Multi Layer BIM Simulation w/ EM-Suite (Panoramic) N.A. / 1.35, λ / 193nm, Dipole Illumination 1 DOP for Mask Structure.4.3 th Diffraction Order 1st Diffraction Order DOP Half Pitch (nm) Half Pitch (nm) Att.PSM Thick Cr BIM Thin Cr BIM Multi Layer BIM First and zero diffraction order polarization are shown to be influenced by the structure of masking film. 11 6

7 NILS for Mask Structure NILS Half Pitch (nm) Simulation w/ EM-Suite (Panoramic) N.A. / 1.35, λ / 193nm, Dipole Illumination Att.PSM MoSi : 68 Thick Cr BIM Cr : 13 Thin Cr BIM Cr : 59 Multi Layer BIM Cr : 74, MoSi : 93 As half-pitch of pattern decreased, NILS of MoSi decreases significantly while those of thick Cr and Multi layer BIM are not much varied. 1 MEF according to Mask Structure MEF Half Pitch (nm) Experiment Condition Dipole 1.35NA w/ Polarization AFA ArF Att.PSM Thick Cr BIM Thin Cr BIM Multi Layer BIM Thick and thin Cr BIM show better MEF value than others. But MEF is not matched with NILS result in case of thin Cr BIM. 13 7

8 Comparison of Exposure Latitude L/S Pattern with Dipole NA CD (nm) nm Half Pitch 44nm Half Pitch 48nm Half Pitch Energy (mj) Energy (mj) Energy (mj) Att.PSM Thick Cr BIM Thin Cr BIM Multi Layer BIM Half Pitch Att.PSM Thick Cr BIM Thin Cr BIM Multi Layer BIM 4nm 14.7 % 17.4 % 13. % 13.3 % 44nm 15. % 18. % 17.5 % 16.8 % 48nm 14.5 % 18.4 % 18.8 % 17.6 % 14 Comparison of DOF L/S Pattern with Dipole NA CD (nm) nm Half Pitch 44nm Half Pitch 48nm Half Pitch Defocus (um) Defocus (um) Defocus (um) Att.PSM Thick Cr BIM Thin Cr BIM Multi Layer BIM Half Pitch Att.PSM Thick Cr BIM Thin Cr BIM Multi Layer BIM 4nm.15 μm.1 μm.8 μm.15 μm 44nm.1 μm.15 μm.15 μm.16 μm 48nm.8 μm.8 μm.1 μm.1 μm 15 8

9 SEM for L/S Pattern 38nm 4nm 44nm 48nm Att.PSM Thick Cr BIM Thin Cr BIM ) EL (%) Half Pitch (nm) Att.PSM Multi Layer BIM Thick Cr BIM Thin Cr BIM Multi Layer BIM 16 DRAM Isolation Pattern Crosspole 1.35NA 44nm Half Pitch Isolation Pattern Att.PSM Thick Cr BIM Thin Cr BIM Multi Layer BIM Mask Type EL DOF Eop Att.PSM 8.7 %.4 μm 43.1 mj Thick Cr BIM 6.66 %.6 μm 45.9 mj Thin Cr BIM 644% μm mj Multi Layer BIM %.4 μm mj Similar dose to size for different mask structures contrary to 1D L/S means polarization dependent transmittance behavior is Different in D BW pattern. Peak EL in multilayer BIM needs to be examined again! 17 9

10 Diffraction vs. Polarization in D BW Incidence angle 17, 45nm Brick Wall pattern (,) Diffraction intensity Thin Cr BIM Mask Linewidth ( μm ) (,)_TE (1,-1)_TE (,-)_TE (,)_TM (1,-1)_TM (,-)_TM Diffraction intensity Att.PSM (1,-1) (1,-1) (,-) Mask Linewidth ( μm ) In D BW pattern, att.psm shows no TM preference to TE in th and even higher intensity of 1 st order diffraction in TE polarization contrary to 1D L/S case while similar behavior in thin Cr Mask show 18 DRAM Contact Hole Pattern EL (%) Crosspole 1.35NA 44nm Half Pitch Hole Pattern Exposure Latitude Att.PSM Thick Cr Thin Cr Multi Layer BIM BIM BIM Eop (mj) Att.PSM Optimum Energy Thick Cr BIM Thin Cr BIM Multi Layer BIM Similar E/L and dose to size for D contact array patterns regardless of mask structures except for eccentric low dose to size behavior in multi-layer BIM. 19 1

11 Pattern Fidelity for Contact Hole Crosspole 1.35NA 44nm Half Pitch Hole Pattern Att.PSM Thick Cr Thin Cr Multi Layer BIM BIM BIM (Cr/MoSi) Pattern fidelity of the hole pattern is similar to all mask structure. Pellicle Effect on Hyper NA 1 Simulation w/ G-Solver Transmittance N.A..815 μm Thickness.85 μm Thickness.835 μm Thickness.845 μm Thickness.855 μm Thickness Current 1.35NA Transmittance of pellicle is changed by the incident angle according to NA. Thickness of pellicle should be optimized to minimize the transmission loss as NA gets higher. 1 11

12 Experimental Verification for Pellicle Effect 1.NA, Dipole Y Open Angle 9,.97/.8(Inner σ/outer σ), x-polarization CD Difference (nm) w/ Pellicle w/o Pellicle Horizontal Pattern Vertical Pattern Pellicle can change optical proximity effect by transmittance change. Summary Technical issues of polarized illumination in hyper NA imaging were studied through experiment and simulation. How much merit by Polarization on through pitch Light interaction with mask structure is significant in Hyper NA Effect of 3D mask structure is studied through simulation and experiment. 4 types of mask were made for this experiment such as att. PSM, Thick Cr BIM, Thin Cr BIM and multi layer BIM The image contrast is strongly dependent on mask bias, need to be taken into account for comparison of att.psm and BIM BIM shows better performance than att.psm below 44nm half pitch L/S pattern. But MEF is not matched well to simulation result because of incomplete optimization on mask bias. In case of D pattern, it is difficult to find the advantage of BIM for sub-45nm. It needs further study for D pattern Pellicle transmittance is changed by thin film interference effect and should be corrected through the optimization of pellicle thickness 3 1