Thin Film Deposition Using Excimer Lasers

Brant Campbell, Idaho State University

Advances in laser technology have led to the creation of a high power ultraviolet laser.  The excimer laser operates on the same basic premise as other types of lasers, but has some very distinct differences in how lasing is achieved.  An excimer is a diatomic molecule that only exists in an excited state.  In an excimer laser, a large electrical discharge excites gases in a chamber in such a way that they will combine to form a stable molecule in an excited state.  The molecule then decays to the ground state by emitting a characteristic photon and the molecule dissociates.  The UV photons emitted have an energy greater than the binding energy of many molecules and can therefore be used to break apart molecules.  The plume created by the laser pulse can be directed onto a substrate and the particles from the target will be deposited onto the substrate.  This process is called pulsed laser deposition (PLD).  PLD can be used to create thin films on many types of materials useful in modern technology.  One tool used to analyze thin films created by PLD is the atomic force microscope (AFM).  The AFM uses a cantilever with a very small tip to characterize the nature of the substrate surface.  This results in a two or three dimensional representation of the thin film being scanned.  With appropriate software, a very detailed roughness analysis can be obtained, including quantities such as total surface area, maximum, minimum, and average height of the surface, and average thickness.  This technique is important for many areas of research including integrated circuits and optoelectronics, micromechanics, and medical implants.