Cleaning of Hydrocarbon Buildup on Metallic-oxide Thin-Films Richard Sandberg Ross Robinson, Dr. David Allred, Dr. R. Steven Turley, Aaron Jackson, Shannon Lunt, Elke Jackson, Kristi Adamson, Guillermo Acosta, Nick Webb, Mike Diehl, Luke Bissell Brigham Young University Department of Physics and Astronomy

How to Stay Clean in an Unclean World? Determining Optical Properties for Ur, V, Sc:  Applications: -Image satellites -Medical equipment -UV computer chip lithography  We need to understand the optical properties of these materials in this region. EUV light is highly reactive to materials—a few Ångstrons of material greatly affect reflectivity.

Lithography Multilayer Mirrors Images from XUV Astronomy XUV Microscopy

Purpose: What does hydrocarbon buildup do to reflectance? How do we effectively remove hydrocarbon buildup? Does this cleaning process damage our thin films? Outline 1. Effects of hydrocarbon Contamination buildup 2. Opticlean Process 3. Opticlean Residue 4. Damage to thin films? 5. Removing Opticlean Residue through plasma etching 6. Conclusions

Sample Creation  Creation in vacuum chamber on silicon substrates RF Sputtering Evaporation  We are working in high vacuum, but not Ultra high vacuum

Reflectance goes down with hydrocarbon buildup in the EUV Produced on IMD Software

A Clean Surface is Important EUV light is very reactive with materials, therefore, a few angstroms of contaminant will greatly reduce reflectivity. We expect to see the following decreases from initial reflectance due to buildup of 18 days: 46% of initial reflectance due to leaving in ambient air (Corresponds to 20 Ångstroms of buildup) 36% of initial reflectance due to touching with a latex glove (Corresponds to 46 Ångstroms of buildup)

Opticlean Process leaves hydrocarbon residue Opticlean significantly removes contaminants, but leaves a residue Ellipsometric Results Opticlean residue thickness on two runs: 1.17 Ångstroms 2.22 Ångstroms Opticlean made by Dantronix Research and Technologies, LLC Ellipsometer Type: J.A. Woollam Co., Inc Multi-Wavelength Ellipsometer (EC110)

Does the Opticlean process damage thin films?  Scanning Electron Microscope with EDAX showed no thin film damage, nor trace of materials used in thin films on pulled of Opticlean (U, Sc, Va).  X-Ray Photoelectron Spectroscopy found no trace of materials used in thin films on pulled of Opticlean.

XPS revealed components of Opticlean, but not heavier metals used in thin films. Prominent thin-film lines: Ur-380 eV, V-515 eV, Sc-400 eV Photon Energy (eV) Photons (Counts) 97 eV (Si 2p) 148 eV (Si 2s) 281 eV (C 1s) 527 eV (O 1s)684 eV (F 1s)

Cleaning residue with “Matrix” Plasma Etch  RF Plasma Etching with O 2 Plasma Torr Pressure 250W RF (max 350) 0.75 SCCM O 2 flow No extra heat applied  Good for removing polymers, but not bulk contaminants (i.e. Dust)  Active Oxygen plus mechanical sputtering removes surface layers  Used to clean Opticlean residue RF

 Samples cleaned with Opticlean to remove bulk contaminants without damaging sample.  Opticlean residue was subsequently removed with “Matrix” Plasma Etch 23 Å residue left on surface 1:20 min. in O 2 plasma Plasma removed 22 Å  Hydrocarbon goo can effectively be removed with a two step cleaning process of Opticlean and Plasma Etching Putting It All Together

Thank You!Stay Clean!! My Information Richard Sandberg BYU Department of Physics and Astronomy (801)