In some PVD systems, used in our laboratories to prepare thin films, plasma is generated. Plasma properties significantly influence the growth and properties of deposited films. The systems include magnetron sputtering and pulsed laser deposition (PLD) alone, and hybrid laser deposition systems based on combinations of PLD and additional RF discharges, ECR plasma, magnetron sputtering employing several plasma sources. Measuring and evaluating the plasma composition and its properties in these systems is very important to us. The dependence of plasma parameters on the deposition conditions (working gas pressure, working gas type, target performance, distance from target) is usually determined.
We use several techniques for plasma characterization:
- mass spectroscopy, where we extract the ions from the plasma into a mass analyzer, where they are divided according to the ratio of mass and charge (m/Z). Combination with an energy analyzer can also directly measure the energy of ions. Ions can be collected at different locations in the discharge geometry.
- optical emission spectroscopy, which is based on the detection and analysis of light emitted by excited particles (atoms, ions, molecules) in plasma. This technique is very often used in PLD. Its great advantage is that it is non-destructive and has relatively simple implementation, it allows monitoring plasma directly during deposition. From the OES measurements, information about plasma composition (identification of individual particles - atoms, molecules, ions) and important plasma parameters such as: temperature and electron density, vibrational and rotational temperature of molecules can be obtained. Plasma evolution can be examined both in time - time resolved spectroscopy and in space - spatially resolved spectroscopy.