Organic Materials Development for Advanced Lithographic Applications Jacob

Organic Materials Development for Advanced Lithographic Applications Jacob R. Adams Willson Research Group University of Texas at Austin 1 1

Rising Cost of Wafer Fabs Vs. GNPs 100 nm technology node, 2004 70 nm technology node, 2007 50 nm technology node, 2010 35 nm technology node, 2013 1000 Denmark Singapore Hungary Czech Rep. Luxemburg Guatemala Panama Kenya Macedonia Monaco 100 billion $ GNP of: 10 1 0. 01 feature size [µm] Ralph Dammel 2 2

# Transistors Moore’s Law http: //www. intel. com/technology/timeline. pdf 3 3

Minimum Feature Size Reduction in Semiconductor Devices: Moore’s Law 10, 000 436 nm Contact Exposure 4 K / 7000 Minimum Dimension (nm) 5, 000 16 K / 5000 436 nm 64 K / 3000 2, 000 1: 1 Projection 256 K / 1500 436 nm 1 M / 1000 1, 000 5: 1 Projection 4 M / 750 365 nm 16 M / 500 64 M / 350 R= k l NA 200 100 256 M / 250 248 nm 1 G / 180 193 nm 4 G / 120 157 nm ? 50 1976 1980 1984 1988 1992 Year 1996 2000 16 G / ? 2004 4 4

Photolithographic Process Photoresist Substrate Silicon Wafer 5 5

Well, How do These Things Really Work? ? resist image 6 6

Some Scale Perspective 1990 1980 800 Å 193 nm resist images 2001 2002 40 nm images These 80 nm features are less than 600 carbon atoms wide [based on the average length of a carbon bond] 7 7

Modular Resist Design Backbone Etch Barrier Latent Acidic Group Protecting Group Patterson, K. et. al. Proc. SPIE-Int. Soc. Opt. Eng. 2000, 3999, 365 -374. 8 8

Resist Progression 436 nm 248 nm 365 nm 193 nm 9 9

Modular Resist Design for 193 nm • Aromatics become too absorbing at 193 nm • Etch rate α N/(Nc-No) • Replace with bridged cyclic aliphatics Ohnishi, Y. et al. J. Electrochem. Soc. 1983, 130(1), 143 -46. 10 10

Examples of 193 nm resists COMA (Cyclic Olefin Maleic Anhydride) Acrylate with Pendant Cage Structure 11 11

Early Imprint Lithography Tang Dynasty Templates 600 AD Mesopotamian Templates 12 12

The Step and Flash Imprint Lithography (SFIL) Process Steps Components Template Release treatment 1. Monomer Dispense Monomer droplet Substrate film stack 2. Spread and Fill 3. UV Cure 4. Separate Spreading Monomer UV radiation Crosslinked film 13 13

Unparalleled Resolution 20 nm Replication with no LER Rogers, J. A. et al. Nano Letters 2004 4(12), 2467– 71. 14 14

SFIL Formulations • Bulky Monomer – Increase Tg • Low Viscosity Monomer – Improve Template Filling • Silicon Containing Monomer - Etch Resistance • Cross-linkable Monomer – Strengthen Mechanical Properties • Photoinitiator 15 15

Motivation for Strippable Materials • Issues: – Highly cross-linked polymers are insoluble – Silicon containing polymers resist oxidative cleaning Cross-linked Imprint Resist • Solution: – Strippable polymers • Improve template lifetime • These templates are EXPENSIVE!!! • Aid wafer reworking 16 16

Strippable Materials De-cross-linking Insoluble Soluble Cross-linked Polymers. Network Cross-linker Polymer Heat, Acid, light, etc. Polymer 17 17

Acid Degradable Cross-linkers • Tertiary Ester Diacrylate (TEDA) – Viscosity: 21. 1 c. P – Dose to cure: 13. 5 m. J/cm 2 • Acetal Diacrylate (ADA) – Viscosity: 12. 3 c. P – Dose to cure: 58. 3 m. J/cm 2 Targeted values: Viscosity < 20 c. P, Dose to cure < 90 m. J/cm 2 Palmieri, F. L. Ph. D. Thesis, Univ. of Texas at Austin, TX USA 2008. 18 18

Mechanism for acid-catalyzed cleavage of tert-Butyl esters 19 19

Mechanism of Acetal Formation -Driving the Process 20 20

Retrosynthetic Analysis 21 21

How to Avoid This Problem • An azeotrope is a mixture of two or more liquids whose proportions cannot be altered by simple distillation. This happens because, when an azeotrope is boiled, the vapor has the same proportions of constituents as the unboiled mixture. 22 22

A Few Boiling Points Component Water Methanol Benzene: Water Benzene: Methanol Boiling Point (o. C) 100. 0 64. 7 80. 2 69. 3 58. 3 23 23

Transketalization Mechanism 24 24

Trans-acet(ket)alization 25 25

Stripping Demonstration Imprinted ADA Stripping Demo Control Acid Treated Polymer Filled Vias Control Acid Treated Cleaned Vias 7: 1 Aspect ratio 26 26

Resolution and Mechanical Integrity 15% TEDA 10% ADA Palmieri, F. et al. ACS Nano 2007, 1(4), 307 -312. 27 27

Conclusions • Acetal Cross-Linked Acrylate – Compatible with SFIL Formulation – Decross-links • Strips from Wafer • Cleans from Template – Sufficient Mechanical Strength • Imprintable 28 28

Acknowledgements • Prof. C. Grant Willson • Dr. Frank Palmieri • Dr. Bill Heath 29 29