This research focuses on what happens when energetic ions collide with surfaces and addresses long-standing issues in plasma-surface interactions. Ion-surface collisions are of paramount importance in many surface-sensitive analytical techniques. They are also essential in industrial processes, such as plasma etching and deposition, both indispensable in semiconductor chip fabrication. In spite of their significance, understanding of plasma-surface interactions has lagged behind applications, forcing process development by cumbersome, time-consuming, and costly trial and error. Such understanding can be obtained through ion beam experiments, which are themselves very difficult to perform. A unique and powerful ion-beamline scattering apparatus, custom-built in the PI's group over the last 6 years with NSF and industrial support, makes the proposed research possible. The apparatus utilizes plasmas to extract and purify ions, such as fluorine and carbon fluorides, which are then transported to and allowed to interact with a grounded sample surface, such as silicon, aluminum, and silicon oxide, all important in fabricating microprocessors. The outcome of the interaction is monitored using sensitive mass spectrometers and energy analyzers to infer the identity and measure the energy of the scattered products. Specific phenomena to be studied include charge exchange at surfaces, ion fragmentation, energy losses due to quantum mechanical effects, and reaction mechanisms. A detailed picture of the scattering interaction will be produced including etch yields and reaction products as a function of incident energy and angle. The experiments will be complemented by molecular dynamics simulations to improve atomistic understanding.
Broad Impact: This research is expected to generate results that are fundamental enough to be used by theorists for validating atomistic simulations of beam-surface interactions and practical enough to be useful to process engineers for selecting chemistries and operating conditions for rapid optimization of plasma tools. The intent is to establish a new paradigm in etch process development through a combination of fundamental beam scattering experiments and etch profile evolution simulations, thus speeding up the development of new etch processes for semiconductor fabrication. Knowledge and understanding obtained through these experiments will be incorporated in courses and tutorials on plasma-surface interactions to educate students and engineers on the underlying principles of chemical reaction dynamics. In addition, a new, low-cost experiment involving atmospheric microplasmas in direct patterning of silicon will introduce plasma-surface interactions to undergraduates.
