NanoImprint Materials Ratnam Sooriyakumaran Hiroshi Ito Mark Hart Frances Houle Geraud Dubois Robert Miller Robert Allen March, 2006 05/24/2006
Imprint in IBM IBM Research Division is conducting an exploratory project on Materials for Imprint Lithography and Applications. This is not part of IBM s Semiconductor Lithography Roadmap. 2 Sematech Litho Forum 05/24/2006
NanoImprint Materials: utline Imprint: A Lithography System process/materials/tool Imprint Materials Requirements Core Challenges in Imprint Materials with examples Resists for high speed patterning Low Dielectric Materials for Dual Damascene Template Fabrication Materials Summary and Conclusions 3 Sematech Litho Forum 05/24/2006
Imprint: The System (thanks to Molecular Imprints!) TL MATERIAL TEMPLATE ETCHER FR DRY DEVELP Litho Metrics Tool Impact Material Impact Template Impact Etcher Impact Resolution HIGH LW HIGH LW CD control HIGH LW HIGH LW verlay HIGH LW HIGH LW Defects HIGH HIGH HIGH LW Throughput HIGH HIGH LW LW 4 Sematech Litho Forum 05/24/2006
It s different this time.with few similarities Conventional (193nm) Squirt the juice 1-5 cc of photoresist solution per wafer Bake (PAB) Introduce wafer into exposure tool Scan/expose Exit wafer out of tool PEB Develop Etch Transfer Squirt the juice onto wafer inside the tool 1-5 microliters of photoactive monomers per field Fill the mold (quickly!) Expose Imprint Material Cures (really quickly!) Delaminate mold Step and repeat Etch Transfer 5 Sematech Litho Forum 05/24/2006
Step and Flash Imprint Taxonomy Template Etch Barrier (Resist) Transfer Layer Charge Dissipation Layer Patterned Layer Release Layer Residual Layer Adhesion Layer Adhesion Layer Substrate 6 Sematech Litho Forum 05/24/2006
Interface energetics and stability in UV-cure nanoimprint lithography: potential sources of defectivity Cohesive failure of resist Resist adhesion to template despite release layer template polymer silicon Release layer Cured resist Adhesion failure Failure of resist to wet surfaces 7 Sematech Litho Forum 05/24/2006
Imprint Materials Requirements Low Viscosity Required for high fill rates Proper Surface Tension and compatibility with release coating High speed cure (for low dwell times) Low adhesive forces after cure (Clean Release) Proper Mechanical Properties after cure? Etch Resistance for pattern transfer In resist (Si Resist) In planarization material (reverse tone process) 8 Sematech Litho Forum 05/24/2006
Core Challenges: Materials for NIL Materials Sacrificial (resist) layers Image reversal materials Permanent Materials (e.g., Dual Damascene ILD Material) Template fabrication materials fundamentals High Performance Release (Low Defectivity) Durability of release coating Control/robustness of surfaces 9 Sematech Litho Forum 05/24/2006
Release Investigations glass resist XPS, contact angle, AFM silicon cure conditions: 365nm (unfiltered), 30s, 35mW/cm 2 separate or delaminate in double cantilever beam mode for adhesion measurement XPS, contact angle, AFM Resists: acrylates, vinyl ethers and NID with varying chemical characteristics Release layers: fluorosilanes 10 Sematech Litho Forum 05/24/2006
Chemical degradation of release layer during cure: XPS of SiA resist and release surfaces shows fluorine loss and oxidation release layer (unused) (CF 2 ) x SiA resist, glass side C region SiA resist, silicon side C region C-C,H intensity, arb units release layer after cure CF, C, C-C,H intensity, arb. units material on glass after cure, no release treatment resist cured in contact with glass, no release resist cured in contact with release layer C,F C, 310 305 300 295 290 285 280 275 binding energy (ev) Surface compositions Si/C F/C Si/ Glass, no release 3.64 0 0.45 Resist, no release 0.07 0 0.21 Virgin release layer 0.65 1.91 0.6 Glass, release 0.99 1.71 0.39 Resist, release 0.12 0.004 0.36 310 305 300 295 290 285 280 275 binding energy (ev) No release: resist transfer to glass Release: some C, F loss and increase on glass, little F on resist 11 Sematech Litho Forum 05/24/2006
Cure Chemistry ptions for Imprint Resists Free Radical (e.g., Acrylate) Higher Viscosity Carefully balanced volatility High Speed Cure Simple formulations Cationic (e.g., Epoxy or Vinyl Ether) Low Viscosity High Speed Cure Possible Although most are slow! Complex Formulations 12 Sematech Litho Forum 05/24/2006
Cationically Curable Etch Barrier Silanol condensation (slow, H 2 elimination) Ring-opening polymerization of Si-containing epoxides (slow especially with perfluoroalkanesulfonic acid, less shrinkage) Addition polymerization of Si-containing vinyl ethers (fast, more shrinkage) EGDVE 0.75 cps at 25 o C (UT Austin) volatile, poor solvent of PAG DEGDVE TEGDVE good solvent for PAG E. K. Kim et al., J. Vac. Sci. Technol., B22(1), 131(2004); B23(6), 2967(2005) Si-VE Si 1.0 cps at 25 o C (UT Austin) poor solvent for PAG Si=16.3% Si Si Si Si Si Si=21.6% Si=35.2% TMS 3 Si-VE TMS-VE Viscosity (less viscous than acrylates) Volatility Si concentration PAG solubility TFEVE CF 3 better release? CF 2 CF 2 CF 2 CF 3 NFHVE Central Glass 13 Sematech Litho Forum 05/24/2006
Epoxy vs. Vinyl Ether Cure Time (7.4 mw/cm 2 at 254 nm without filter) Cure Kinetics EGDGE + 4.9 wt% S SbF 6 40-45 sec 10 9 photo DSC 2797-13A, B, & C 250-450 nm, 25 o C DEGDVE + 4.9 wt% + 2.9 wt% S S S 2 CF 3 S 2 CF 3 >>200 sec <5 sec Heat Flow (W/g) 8 7 6 5 4 3 2 1 0 2766-85D DEGDVE + Ph 2 SPhCH 3 Tf +anthmeh 0.05 min exp 2766-89A EGDGE + TPSSbF6 1.0 min exp 2766-89B EGDGE + TPSTf 5.0 min exp CH 3 + H -1-2 0 1 2 3 4 5 6 7 Time (min) 14 Sematech Litho Forum 05/24/2006
AMRC Project on Low-k Dielectric Materials for NIL Grant Willson and team working with IBM Research (Scope ILD NIL Materials and Processes for back-end process simplification).can NIL be used for semiconductor processing? Almaden Team represented by Mark Hart Assignee to AMRC/Nanoimprint Lithography Experiments @ UT Mark is backed up by chemists in 3 groups at Almaden Low-k team (characterization and new materials designs) Resist (litho materials) Team (Silicon Chemistry) SDL (Formulation Scale-up) Willson Group has NanoImprint experience IBM supplying initial materials to UT with new design IBM supplying low-k know-how and characterization Exchange of personnel for future materials directions IBM Research Assignee: Mark W. Hart (External Programs (7/05 1/06), Lithography (1/06 7/06)) 15 Sematech Litho Forum 05/24/2006
Why NIL for Integration? Current Dual-Damascene Integration Scheme Dispense ur Proposed Integration Scheme Template PSS Deriva Patterned Wa Press and Photocure Release Breakthrough Etch High Temp Thermal cure M. Neisser et. al, Solid State Technology August 2000, Pp.127-132 Up to 18 steps Metal Deposition CMP 16 Sematech Litho Forum 05/24/2006
Photocurable Dielectric Material Requirements Property/Characteristic Low Viscosity Photocurable Cure Shrinkage Dielectric Constant Thermal Stability Mechanical Properties CTE Water Sorption Requirement Less than 50 cps Fast Chain polymerization Less than 15% ε 3 Less than 1% wt loss/hr @ 400 o C Young s Modulus 5 GPa Less than 25 ppm/ o C Less than 0.5% wt 17 Sematech Litho Forum 05/24/2006
Nano Imprint Materials for Back End Process (Project Flow) Early Charcterization Viscosity Volatility Cure kinetics (photodsc) New Materials Synthesis Formulation Development Cured film properties Mechanical and Electrical Adhesion/Delamination/Interfacial Volatility measurement using the TGS-2 microbalance Printing w/ P Imprio-55 and Suss a Interface Crack b Adhesion energy 18 Sematech Litho Forum 05/24/2006
ur Material Design Polymerizable functional groups R = R R Si Si R R Si Si Si Si R R Si Si R R cto-pss (an 8-legged beast) IBM Process + Polymerizable diluent to adjust the viscosity + Photoinitiators High Temperature Cure after printing (burn out) (this removes most of acrylic for lower density (lower k) 19 Sematech Litho Forum 05/24/2006
PSS Reactive Diluents for NIL Property Adjustment (methacrylates) ur toolbox CH 3 IBMA (High Tg, high viscosity) Si Si Si Si MMA (Low viscosity, high volatility) CHMA 4SiMA (% silicon adjustor) EHMA (High Tg, Lower Viscosity) (Low viscosity. Low Tg, Low Volatility) 20 Sematech Litho Forum 05/24/2006
NIL Material Data printing on MI-55 @ UT 50 nm l/s Reference Acrylate IBM ILD NIL material (1 cp) (25 cp) 21 Sematech Litho Forum 05/24/2006
NIL Material Data printing on MI-55 @ UT Before and After Cure k ~ 3.9 k < 2.9 IBM ILD NIL material (25 cp) IBM ILD NIL material (25 cp) (Shrinkage > 25% after 400 0 C cure) 22 Sematech Litho Forum 05/24/2006
PSS based Low-k NanoImprinting Materials Properties Treatment t (nm) RI Density (g/cm3) k (25 0 C) E Modulus (GPa) UV/ RT 1075 1.4901 1.348 4.33 6.29+-0.12 UV/RT 400 o C / 1h 664 1.4811 1.268 3.05 5.97+-0.10 23 Sematech Litho Forum 05/24/2006
Summary IBM engaged with UT (Willson Group) and Sematech on exploratory project on materials for NanoImprint Litho for Back End Process Simplification Several chemical approaches toward NIL ILD s have been indentified. We ve created a class of materials with low viscosity and volatility, good printability and low k after curing/burning. ctoposs/monofunctional methacrylate formulations Si/C ratio is easily modulated for etch property control Several approaches for NIL back end processes beginning Permanent (complex template, difficult materials) PSS Standard (sacrificial) (template easier, materials easier, etch difficult) 24 Sematech Litho Forum 05/24/2006
Template Materials (e-beam resists) Desire positive and negative tone materials with the following characteristics for this 1X application Resolution to support 22nm node Low LER Relatively fast writing speeds 25 Sematech Litho Forum 05/24/2006
nable-an Internally developed negative resist (e-beam) 200 nm pitch/200uc/cm 2 Linewidth = 31 nm Height = 119 nm 26 Sematech Litho Forum 05/24/2006
Conclusions and Recommendations Template is Achilles Heel Industry focus on mask technology should be leveraged Better Resists for mask/template making (resolution/speed/ler) Imprint R&D should be enabled by Sematech for 22nm node Tooling Materials Testing 27 Sematech Litho Forum 05/24/2006