HARRICK PLASMA

For references citing the use of our plasma cleaners, categorized by research application, see the References: Technical Articles page.

Benefits of Plasma Cleaning

  • Remove organic contaminants by chemical reaction (O2 or air plasma) or physical ablation (argon plasma)
  • Eliminate the use of chemical solvents as well as storage and disposal of solvent waste
  • Clean surfaces with microscale porosity or microchannels not suitable for solvent cleaning due to surface tension limitations
  • Render most surfaces hydrophilic; decrease water droplet contact angle and increase surface wettability [Figure 1] (see also Surface Adhesion and Wettability)
  • Promote adhesion and enhance bonding to other surfaces
  • Prepare surface for subsequent processing (e.g. film deposition or adsorption of molecules)
  • Sterilize and remove microbial contaminants on the surface; beneficial for biomedical applications and biomaterials (see also Biomaterials)
  • Clean surface without affecting the bulk properties of the material
  • Can treat a wide variety of materials as well as complex surface geometries; examples include:
    • Semiconductor wafers and substrates (Si, Ge)
    • Glass slides and substrates
    • Optics and optical fibers
    • Oxides (quartz, indium tin oxide (ITO), TiO2, Al2O3; mica)
    • Gold and metal surfaces
    • Electron microscopy (EM) grids
    • Atomic force microscopy (AFM) cantilever tips

Applications

  • Clean substrates to reduce background autofluorescence originating from organic contaminants for fluorescence microscopy
  • Clean optics, crystals (quartz, Ge, ZnSe), cuvettes, and substrates for spectroscopic measurements (ATR-FTIR, UV-Vis, SERS)
  • Clean quartz crystals for quartz crystal microbalance (QCM) measurements
  • Clean AFM cantilever tips for surface morphology and frictional force measurements
  • Clean electron microscopy (EM) grids, specimen holders, and substrates
  • Clean printed circuit (PC) board and die surface prior to bonding
  • Clean gold surfaces for self-assembly experiments

Processing Methods

  • Oxygen or air plasma
    • Removes organic contaminants by chemical reaction with highly reactive oxygen radicals and ablation by energetic oxygen ions
    • Promotes hydroxylation (OH groups) on the surface
    • May oxidize the surface; oxidation may be undesirable for some materials (e.g. gold) and may affect surface properties
  • Argon plasma
    • Cleans by ion bombardment and physical ablation of contaminants off the surface
    • Does not react with the surface or alter surface chemistry
  • For applications that are sensitive to potential contamination from trace impurities (e.g. Ca, K, Na) in borosilicate glass, a quartz chamber is recommended over the standard Pyrex chamber
  • Suggested process parameters values for plasma cleaning using a Harrick Plasma cleaner (some experimentation may be required to determine optimal process conditions)
    • Pressure: 100 mTorr to 1 Torr
    • RF power: Medium or High
    • Process time: 1-3 minutes
    • Low RF power may be used to minimize surface roughening; the process time may require adjustment to compensate for the lower power

Figure 1. Water droplet contact angle measurements on 3 different borosilicate glass surfaces: (a) halocarbon wax-coated (92°), (b) untreated (32°), and (c) argon plasma-cleaned using a Harrick Plasma cleaner (<10°). Source: Sumner, A. L., E. J. Menke, Y. Dubowski, J. T. Newberg, R. M. Penner, J. C. Hemminger, L. M. Wingen, T. Brauers, B. J. Finlayson-Pitts. "The Nature of Water on Surfaces of Laboratory Systems and Implications for Heterogeneous Chemistry in the Troposphere." Phys. Chem. Chem. Phys. (2004) 6: 604-613 - Reproduced by permission of The Royal Society of Chemistry (http://www.rsc.org/pccp).