You are watching the sputtering of CoFe and Permalloy on a 3 inch Si wafer. The first faint plasma is the CoFe sputtering. When the CoFe gun shuts off the screen goes dark and the Permalloy gun is turned on. The plasma from the Permalloy deposition follows the path of the magnetic field.
In magnetron sputtering with a suitable magnetic field configuration it is also possible to control the microstructure, chemical and phase composition of the growing film. Besides balanced discharges, two types of unbalancements are possible: type I and type II.
In type I, the plasma that is not strongly confined on the target, does not interact with the substrate. This magnetic assessment is specially used for sputtering multi-compositional films containing low melting point elements. In type II the plasma is confined both on the target and in a secondary confinement that bombards the growing film with a flux of ions extracted from the plasma. In such latter case, the ion bombardment has an effect of “plasma washing” of the film in the mean time it grows. Impurities weakly bounded to the film are knocked out from the impinging ions. That results into a strong increase of purity of the films in the substrate regions touched by plasma, while all the rest has higher impurity content. In the magnetron source we built, it is possible to pass from the balanced to unbalanced regime, just changing the magnetic core, without breaking vacuum.
The drawback of magnetically unbalanced configurations is that the plasma cone flushin the substrate has very narrow dimensions.
We have developed an electrostatic imbuto that opens the cone of plasma extending the unbalancement effect to larger dimension substrates.
This is a glow discharge ball located in the Scitech museum in Western Australia
* Museum Exhibit Display
* Definition: Kinetic Plasma Display/Sculpture
* Total Height: 62 inches (5 foot 4 inches) tall.
* Globe Width/Diameter: 24 inches wide.
* Globe: Hand-blown Borosilicate/Pyrex (Corning) crystal sphere.
* Power supply (included): 240/220volts AC
* Cabinet Finish: Satin Black Matt
* Electrode: Thinly coated Silver Colloidal on inner electrode terminal wall.
* Fill Mixture: Research Purity Grade Inert Gas (non toxic) plus catalysts.
* Run time testing = 36 hours continuous for testing.
* Condition: Filled 2008 – ‘Vintage’ 1988 Borosilicate Corning Crystal globe.
* Color: Unique steel-blue & violet with crimson highlight effect
* Discharge effect: Single streamer from electrode to top of the sphere, which then splits and creates a “plasma dome” or “inverted cauldron” effect. The high conductance of the gas combination means a single fingertip will attract the plasma strands on contact. (see video) Glass walls are thermal shock resistant.