This device allows a variety of materials to be presented for laser ablation without breaking vacuum. The planetary-action target carousel holds up to 6 targets, with computer control for depositing multi-layer films using different materials. A water (or LN2) cooled baffle protects the mechanism and the other targets from over-spray or stray deposition during processing. Made using 100% UHV-compatible materials and processes, the MTS PLD carousel can be used in any environment.
How it works
Pulsed laser deposition (PLD) is a thin film deposition (specifically a physical vapor deposition, PVD) technique where a high power pulsed laser beam is focused inside a vacuum chamber to strike a target of the material that is to be deposited. This material is vaporized from the target (in a plasma plume) which deposits it as a thin film on a substrate (such as a silicon wafer facing the target). This process can occur in ultra high vacuum or in the presence of a background gas, such as oxygen which is commonly used when depositing oxides to fully oxygenate the deposited films.
While the basic setup is simple relative to many other deposition techniques, the physical phenomena of laser-target interaction and film growth are quite complex. When the laser pulse is absorbed by the target, energy is first converted to electronic excitation and then into thermal, chemical and mechanical energy resulting in evaporation, ablation, plasma formation and even exfoliation. The ejected species expand into the surrounding vacuum in the form of a plume containing many energetic species including atoms, molecules, electrons, ions, clusters, particulates and molten globules, before depositing on the (typically) hot substrate.
The flange-to-target distance is adjustable over a range of distances. Targets are driven by a 0-20 RPM DC motor, which includes a variable-speed supply. Indexing from one target to another is via a stepper motor, which allows multi-layer devices to be deposited automatically. A water- or LN2 cooled shield protects the mechanism and other targets from over-spray or undesirable coating. The shield includes flex lines, reservoir and feedthroughs. An optional shutter is also available.