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

Rising Cost of Wafer Fabs Vs. GNPs 100 nm technology node, 2004 70 nm 50 nm 35 nm technology technology technology GNP of: node, 2007 node, 2010 node, 2013 1000 Denmark Singapore 100 Hungary Czech Rep. Luxemburg Guatemala billion $ 10 Panama Kenya Macedonia 1 Monaco 0.1 0.01 10 1 0.1 0.01 feature size [µm]  Ralph Dammel

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

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

Photolithographic Process Photoresist Substrate Silicon Wafer

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

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

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

Resist Progression 365 nm 436 nm 193 nm 248 nm

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.

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

Early Imprint Lithography Tang Dynasty Templates 600 AD Mesopotamian Templates 12

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

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

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

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

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

Acid Degradable Cross-linkers Tertiary Ester Diacrylate (TEDA) Viscosity: 21.1 cP Dose to cure: 13.5 mJ/cm2 Acetal Diacrylate (ADA) Viscosity: 12.3 cP Dose to cure: 58.3 mJ/cm2 Targeted values: Viscosity < 20 cP, Dose to cure < 90 mJ/cm2 Palmieri, F. L. Ph.D. Thesis, Univ. of Texas at Austin, Austin, TX USA 2008.

Mechanism for acid-catalyzed cleavage of tert-Butyl esters

Mechanism of Acetal Formation -Driving the Process

Retrosynthetic Analysis

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.

A Few Boiling Points Water 100.0 Methanol 64.7 Benzene 80.2 Component Boiling Point (oC) Water 100.0 Methanol 64.7 Benzene 80.2 Benzene:Water 69.3 Benzene:Methanol 58.3

Transketalization Mechanism

Trans-acet(ket)alization

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

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

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

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