Experimental and theoretical investigation of the excimer laser ablation process.

摘要

Excimer lasers are beginning to find extensive applications in surface modification and drilling due to their ability to pattern high resolution features in a reproducible and controlled manner, with minimal thermal damage. These ultraviolet (UV) and vacuum ultraviolet (VUV) lasers also have extensive applications in materials processing because of the unique interaction between the UV radiation and the material. Thus, this technique has been used to deposit a variety of thin films, and is the method of choice for the deposition of thin films of superconductor materials.; In the course of this research, the ablation of various polymers and polymer composites was investigated. Effluent analysis was performed using mass spectrometry, and techniques were developed to control/reduce the amount of unwanted and toxic products when various polymers were drilled. Emission spectrometry was shown to be a simple but efficient technique for end point detection. The laser ablation of the polymer composite system of polytetrafluoroethylene (PTFE) and polyimide (PI) was also investigated. The effect of dopant concentration on etch rates and the taper of the drilled holes was studied.; The etch rates of various polymers were modeled as a function of the polymer properties and the incident laser radiation. It is shown that a thermal mechanism is the cause of ablation for the nanosecond pulses that were investigated. Based on these results a new model was developed that describes the ablation process more accurately. The etch rates of various polymers at 248 nm and 308 nm for a range of pulsewidths have been successfully modeled. Threshold fluences are also accurately predicted by this model, and the morphology of the drilled structures for low and high absorption materials is explained in terms of the temperature profile.; Excimer laser ablation and deposition is shown to be a very versatile technique for the deposition of thin films. Thin films of Boron Nitride (BN) were deposited by sputtering a bulk target of hexagonal BN. The dependence of the crystalline structure, atomic composition and morphology on the laser energy, the ambient during deposition and the temperature of the substrate was investigated.