FAQ's | Vacuum coating systems | thin film deposition | - Element-Pi

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FAQ's

In sputtering deposition, many factors affect the grain size of the deposited layer. Target material, working pressure, and base pressure of the chamber can greatly influence the grain size. For a more detailed discussion on effect of base pressure on thin films grain size in magnetron sputtering deposition systems, you can see Effect of Base Pressure on Thin Film Grain Size in Sputtering.

Several parameters in a sputtering deposition process, like working chamber pressure and deposition power affect the layer grain size. Higher argon pressure (working gas pressure) (>50 mTorr) result in a lower density, porous and void structure; where higher sputtering power (larger current), rising temperature of the plasma and the substrate, results in larger particle size. Also, chamber ultimate pressure affects Pt grain size, which is discussed in the article titled as “Effect of base pressure on thin film grain size in magnetron sputtering” in our blog.

Yes, PTFE (Teflon) can be sputter deposited by our RF magnetron sputtering systems. Parameters may differ from device to device, but in the literature the power is set less than 200 W, to avoid melting effects of Teflon targets. The deposition can be performed reaching 10^-3 mbar (low vacuum) or 10^-6 mbar (high vacuum) for the base pressure.

Yes, one can bias the substrate by applying a DC voltage to it, which makes it possible to improve or modify the coating properties and the coating process for targets like ITO.

Several types of sputtering targets like ceramic, inorganic compound, most oxides, nitride and silicide targets are so fragile and show poor heat transfer, so they might crack during sputtering as a result of bearing thermal stress. To avoid this happen, it is recommended to bond such targets to an appropriate backing plate, whom characteristics might affect the deposition parameters.

Also, precious metal targets may need a backing plate, since thinner targets are normally preferred as it highly costs.

Thin film thickness can be measures by various methods, depending on estimated range of thickness. For layers with thickness in the range of 1-2 nm, typical methods like AFM and ellipsometry are not recommended; since if not using highly smooth substrates like Si (100), substrate roughness influences thickness measurement. However; XPS and TEM characterizations are most proper choices. For thickness measurement during layer deposition, quartz crystal microbalance (QCM) technology is mainly used. Using Sauerbrey equation, which relates the mass change per unit area at the QCM electrode surface to the observed change in oscillation frequency of the crystal, one can measure the thickness of the deposited layer. (Read about thickness uniformity of thin films here)

Pulsed Laser Deposition can maintain the correct target composition since it is a pulsed process. In principle, the main mechanism can be explained as flash evaporation of 100% of a small part of the target in a few nano-seconds. So a small volume of the solid target is evaporated during the laser pulse entirely, no matter if different composite materials in the target have different vapor pressures. In contrast, vapor pressure normally determines the composition of the deposited film in an evaporation-based deposition method, where the deposited layer is rich in the materials with the highest vapor pressures.

The sputter deposition rate is related to the type of working gas and pressure, sputtering power applied to the target during deposition, including sputtering voltage and current, the temperature of the target, diameter of the target, the strength of the magnetic field, sputtering yield of the target and so on. For example for Cr, the sputtering rate could be 10nm/min, while for a gold target it can reach to 40nm/min. (You can use the Deposition Material Table for choosing the best method for your coating systems)

In RF magnetron sputtering, if there are cavities or cracks on the sputtering target, it can be source of outgassing that may cause impurities in the deposited layer and degrade some layer properties, e.g. increase stress or create unwanted surface roughness and anisotropies. Cracks may also cause deposition of mesoscopic particles on the substrate which will deteriorate desired properties of the resulting thin film.