3-29-2018

DisCharge: Spin-On Anti-Charging Agent for Electron Beam Lithography

Gerald G. Lopez Ph.D.

Singh Center for Nanotechnology, lopezg@seas.upenn.edu

Glen de Villafranca

Singh Center for Nanotechnology, devilla@seas.upenn.edu

Follow this and additional works at: https://repository.upenn.edu/scn_protocols

Part of the Electronic Devices and Semiconductor Manufacturing Commons, and the Nanotechnology Fabrication Commons

Lopez, Gerald G. Ph.D and de Villafranca, Glen, “DisCharge: Spin-On Anti-Charging Agent for Electron Beam Lithography”,

Protocols and Reports. Paper 50. https://repository.upenn.edu/scn_protocols/50

This paper is posted at ScholarlyCommons. https://repository.upenn.edu/scn_protocols/50 For more information, please contact repository@pobox.upenn.edu.

DisCharge: Spin-On Anti-Charging Agent for Electron Beam Lithography

Abstract

This report documents the chemical DisCharge from DisChem, Inc. used as an anti-charging agent for electron beam lithography at the University of Pennsylvania Singh Center for Nanotechnology Quattrone Nanofabrication Facility. Charge accumulation while exposing atop an electrically insulating substrate can severely impact positional accuracy of the beam yielding poor litho. Using DisCharge has been shown to reduce charge accumulation for insulating substrates such as fused silica pieces, glass slides, and PDMS for positive resists such as PMMA, ZEP520A, CSAR 62 and mr-PosEBR.

Keywords

DisCharge, DisChem, EBL, electron beam lithography, e-beam, e-beam lithography, anti-charging, anti- charging agent

Disciplines

Electronic Devices and Semiconductor Manufacturing | Nanotechnology Fabrication

This working paper is available at ScholarlyCommons: https://repository.upenn.edu/scn_protocols/50

Introduction

This report documents the chemical DisCharge from DisChem, Inc. used as an anti-charging agent for electron beam lithography at the University of Pennsylvania Singh Center for Nanotechnology Quattrone Nanofabrication Facility. Charge accumulation while exposing atop an electrically insulating substrate can severely impact positional accuracy of the beam yielding poor litho. Using DisCharge has been shown to reduce charge accumulation for insulating substrates such as fused silica pieces, glass slides, and PDMS for positive resists such as PMMA, ZEP520A, CSAR 62 and mr-PosEBR.

Spin Curves

DisCharge DI and DisCharge IPA, as the names imply, are provided as DI water or IPA as the main solvent. Using the J A Woolam Vase Ellipsometer, dispersion curves for use on the Filmetrics F40 and F50 were generated. Four inch Si wafers were then spun at different speeds to yield the following spin curves for the two formulations of DisCharge.

Application and Removal

1. Spin coat and pre-bake per the resist
2. Let wafer/sample cool to room temperature for 5-10
3. Spin coat DisCharge a specific RPM for desired thickness for 60 seconds. No pre-bake is required. The thin film should have a gloss finish similar to a properly spun If a matte finish is observed, it means the sample was too hot during application and the solvent evaporated too quickly. Follow removal instructions and re-apply DisCharge. The film does not dry. Be careful not to smudge the surface after spin coating.
4. EBL Tool: Mount sample and be sure the grounding clip is properly touching the sample Expose pattern.
5. Follow removal any one of the instructions below and dry
   1. Spin Rinse Method Removal
      1. Using a spinner, set the spin speed to 3000 RPM for 60
      2. Initiate While spinning, use a rinse bottle to apply generous amounts of IPA (or DI water) followed by an N2 blow dry.
   2. Sink Rinse Method Removal: DI Water
      1. While firmly holding the sample, place sample in direct path of running DI water over a
      2. Dry thoroughly with an N2 blow dry
   3. Solvent Rinse Method Removal: IPA
      1. While firmly holding the sample, place in direct path of an IPA stream using a rinse bottle over a cup sink or beaker to capture the solvent. Do not pour solvents down the drain.
      2. Dry thoroughly with an N2 blow dry
6. Develop the resist as normal.

Evidence of DisCharge as an Anti-Charging Agent

The following experiments provide evidence of DisCharge as an anti-charging agent using the Elionix ELS-7500EX 50 keV at the QNF. Preliminary test structures are contrast curve patterns that consist of 60 micron squares exposed at different dose using a 20 nm beam step size (shot pitch) with a 1 nA beam current.

Impact of DisCharge at the Nanoscale

DisCharge was also tested for its efficacy at the nanoscale using tower patterns exposed In a dose matrix using 300 nm ZEP520A atop fused silica. The tower patterns consist of 300 nm line space patterns at various pattern densities.

Acknowledgements

The QNF would like to acknowledge MicroResist Technologies, AllResist and DisChem for providing courtesy samples of their materials for testing at the Singh Center for Nanotechnology.