Mechanical Properties of Carbon Thin Films

Abstract

Thin film — substrate interaction, residual stress and elastic properties in the disperse and films of nanometeric size are of great importance in the development of microsystems, nanostructures and nanomaterials when working with atoms, molecules or supramolecule structures. Scaling down of geometrical dimensions of the structures, devices and systems is accompanied by control of matter on the micro and nano-meter length scale.

Physical principles of the conventional method for the internal stress measuring — the cantilever technique and electronic speckle pattern interferometry are discussed and related to the stress control in thin film — semiconductor substrate system. Stress kinetics of the thin film structure can be monitored in — situ allowing to control this process at the nucleation stage of the film. The main advantage of the electronic speckle pattern interferometry as compared to the classical interferometry and holographic methods is ability to measure strain of the real diffusive surfaces. Development of the electronic speckle pattern interferometry allows to apply it to the small size (hundreds of micrometers) objects (microelectromechanical devices, microstructures etc.) to monitor and control variations of geometrical dimensions of the different components. Development of the new analysis method is prospective for the new type of structures — freestanding films. Technology of producing of such form film (metallic, diamond like carbon, multilayer structures) combines advantages of plasma based technologies of deposition and combinations of different type of etching. Application of the newly developed optical method with the microtensile machine allows defining elastic properties of such thin film and influence of different technological conditions during deposition.

Carbon nanofibers have been grown by direct ion beam deposition from the acetylene gas (C₂H₂) and hexane-hydrogen vapor (C₆H₁₄+H₂).on Si‹100› substrates at 500°C and 750°C temperature. In all cases SiO₂ overlayer with catalytic Ni film has been used. Features of the nanofiber structures and relation with the residual stress were defined.

Optimization of the technology of the diamond like carbon films enabled to apply this film in the mold used for the nanoimprint lithography (NIL). Equipment and the technology of the NIL was created and applied in our institute for the replication of the photonic structures in the semiconductor substrate. Preparation of the diamond mold for the NIL let to avoid polymer — mold sticking problems during mold separation and raise mold durability as well.