FRG: High Pressure Phase Transformations of Silicon, Germanium and Silicon Nitride

University Of North Carolina At Charlotte, Charlotte NC

Investigators

Abstract

The objective of the proposed research program is to establish an interdisciplinary group of researchers from UN-Charlotte, NCSU and U TN with the necessary range of expertise to characterize the role and influence of the high pressure phase transformations of silicon, germanium, and silicon nitride during manufacturing processing. It is envisaged that this material behavior may be exploited to improve the manufacturing processes by increasing yields, decreasing defects, and reducing the manufacturing costs of devices and products manufactured from these materials. The research plan proposes to extend significantly the understanding of the fundamental principles and mechanics of the deformation and machining of these materials. The high-pressure phase transformations that occur during machining of silicon, germanium, and silicon nitride are a recently discovered manufacturing process mechanism. Existing scientific and engineering models do not include this important effect. It has been suggested that the knowledge of the existence of the high-pressure metallic phase of silicon "has about it the unmistakable scent of a major advance: it is likely to lead to a host of consequential researches". This knowledge is a major breakthrough for the semiconductor and optical research and materials' community. The use of the high-pressure phase transformations of these materials to improve the manufacturing process is a strategic change in the basic conception of the fundamental material process mechanisms. The necessary conditions for exploiting the high-pressure phase transformation of semiconductors and ceramics will be evaluated. This research will advance the knowledge of the mechanics of these materials and permit manufacturers to hurdle the present obstacles that confront them as they attempt to produce products of higher precision and lower cost. The high pressure phase transformation work on these materials promises to be applicable to other engineering ceramics, such as silicon carbide, and to manufacturing processes such as slicing, grinding, lapping and polishing. The high-pressure phase transformation represents a new means for controlling materials, manufacturing processes, and equipment to produce the desired end effect or product. The global importance of semiconductors and ceramics has led to extensive research into the nature of surface deformation as a consequence of materials processes such as machining, grinding, lapping and polishing. With the exception of steels, semiconductors and their various physical properties as the target for research are unsurpassed in terms of human effort invested. In spite of this a detailed knowledge of the physical processes involved in elastic and more so plastic deformation is still at issue. Based on accumulated knowledge it is recognized that the high-pressure phase transformations of silicon (Si), germanium (Ge), and silicon nitride (Si3N4) are responsible for their ductile material behavior during mechanical deformation-based material fabrication processes. The proposed team-based project will provide the direction, focus and synergy needed to successfully bring current knowledge of the influence of the high pressure phase transformation to the forefront of research activities in such areas as materials, tribology, and precision engineering. Through the proposed multi-university small group effort our effectiveness is enhanced by providing for the extension of the basic knowledge and potential relevance of the high pressure phase of these materials to applications involving friction, wear and precision machining. This small group of researchers will provide a coordinated and integrated resource group to industry. The group will provide a reference source for information and expertise on material processing of silicon, germanium and silicon nitride.