What is Sputter Coating?


In conventional SEM mode (high vacuum, high voltage), samples need to be coated with a layer of conductive material to prevent the accumulation of electric charges on their surface when hit by the electron beam used for imaging. This is because charged specimens will alter the trajectory of the electrons in the beam and result in a distorted, low resolution image. Sputter coating is the process by which samples are coated with a thin layer of conductive material. Sputter coating is a physical vapor thin film deposition method in which atoms are vaporized from a solid target and deposited on a sample to form a solid, conductive layer.

In addition to reducing sample charging, sputter coating also improves secondary electrons emission, protects electron sensitive samples, reduces beam penetration and improves edge resolution.The parameters to consider when performing sputter coating include the material for deposition and the thickness and grain size of the deposited layer. Gold/Palladium (80:20) targets are the most common choice for routine coating of a wide range of samples. This target alloy is advantageous because the palladium acts as a physical barrier to prevent the gold to conglomerate into large islands that would restrict ultimate resolution performance. Many other target materials may be used (carbon, chromium, silver, etc.) depending on the requirement for X-ray analysis or back scattered electron detection. However, the deposition of these elements require very low vacuum levels not attainable with the EMS550X. The thickness and grain size of the deposited layer are determined by setting up the 'voltage' 'deposition'. 'current' and 'vacuum' parameters of the instrument. A typical coating layer is I0 nm thick or less, with grain sizes better than 2nm.

Features & Specifications of the EMS 550X Sputter Coater

  • Fully automatic control

  • Low voltage sputtering

  • High resolution fine coating (order of 2nm gold grain)

  • Special rotating stage with full tilt facility fitted as standard

  • Even thickness deposition (typically 20nm or 200 Angstroms for SEM work)

  • 165 mm diameter (6 inches) chamber

  • Borosilicate work chamber dimensions: 165 mm dia x 125 mm high

  • Polycarbonate safety shield

  • Target dimensions: 60 mm dia x 0.1 mm thick

  • Specimen stage: 60mm Dia., Rotating with tilt facility, spacing to target 40 mm

  • Vacuum Gauge Range ATM - 1x10-4 mbar

  • Deposition range 0-50mA

  • Deposition rate 0-25nm/minute

  • Sputter timer 0-4 minutes