GOALI: Diamond Wire Slicing of Crystalline Silicon Materials with Application to Manufacturing of High Quality Solar Cell Substrates

在固定磨料金刚石线切割中，利用由涂覆有金刚石磨料的细钢丝组成的移动线网将非常硬且脆的材料（例如晶体硅和蓝宝石）切割成薄晶片。这些晶片被用作光伏太阳能电池和节能照明设备（如发光二极管）的基板。虽然固定磨料金刚石线切割工艺可以提供比现有半导体晶片切割方法更高的生产率，但缺乏其成本效益应用和优化所需的科学知识。该奖项支持基础研究，这些研究将产生生产高质量光伏太阳能硅基板所需的科学知识，并将机械损伤降至最低。由于更高质量的晶圆在太阳能电池制造过程中不太容易破损，因此从这项研究中获得的知识将导致太阳能电池生产成本降低，进而导致太阳能成本降低。这将直接有利于美国经济和整个社会。从这项研究中获得的知识也将有利于其他行业，如微电子和光电子，其中金刚石线切割工艺用于切割其他半导体和光学材料。该研究涉及先进制造，材料科学和力学等学科。该项目将吸引来自不同背景的学生，包括代表性不足的群体，从而有助于培养先进制造领域的下一代工程师。研究团队将专注于了解和最大限度地减少用于光伏太阳能电池基板的微结构复杂晶体硅材料在金刚石线切割过程中产生的表面和亚表面损伤。该项目的具体目标是了解和量化金刚石磨粒几何形状、晶体取向和缺陷（如晶粒/孪晶边界、位错密度变化）以及金刚石磨粒磨损对切割模式（延性与脆性）、表面形态和金刚石线切割单晶和多晶太阳能硅材料时产生的亚表面损伤的影响。单磨粒金刚石划片实验使用金刚石压头与理想化的形状，晶体缺陷表征作为晶体取向的函数，使用扩展的有限元建模方法的数值模拟，和实验室规模的金刚石线切片实验将被用来研究这些影响。从这些调查的结果可以用来合成金刚石线与优化的砂砾形状和磨损行为，用于制造高品质的薄半导体晶片。

In fixed abrasive diamond wire slicing, very hard and brittle materials such as crystalline silicon and sapphire are cut into thin wafers utilizing a moving wire web consisting of thin steel wires coated with diamond abrasives. These wafers are used as substrates for photovoltaic solar cells and energy efficient lighting devices such as light emitting diodes. Although the fixed abrasive diamond wire slicing process can potentially offer higher production rates than existing semiconductor wafer slicing methods, scientific knowledge required for its cost-effective application and optimization is lacking. This Grant Opportunity for Academic Liaision with Industry (GOALI) award supports fundamental research that will yield the scientific knowledge needed to produce high quality photovoltaic solar silicon substrates with minimal mechanical damage. Since higher quality wafers are less prone to breakage during solar cell manufacture, the knowledge derived from this research will lead to lower solar cell production costs, which in turn will lead to lower solar energy costs. This will directly benefit the United States economy and the society at large. Knowledge derived from this research will also benefit other industries such as micro and optoelectronics where the diamond wire slicing process is used to cut other semiconductor and optical materials. The research involves the disciplines of advanced manufacturing, materials science, and mechanics. The project will engage students from diverse backgrounds including underrepresented groups, and will thereby contribute to educating the next generation of engineers in advanced manufacturing.The research team will focus on understanding and minimizing the surface and sub-surface damage generated in diamond wire slicing of microstructurally-complex crystalline silicon materials used as substrates in photovoltaic solar cells. The specific objectives of the project are to understand and quantify the effects of diamond grit geometry, crystal orientation and defects (such as grain/twin boundaries, dislocation density variations), and diamond grit wear on the cutting mode (ductile vs. brittle), surface morphology, and sub-surface damage produced in diamond wire slicing of mono- and multi-crystalline solar silicon materials. Single grit diamond scribing experiments using diamond indenters with idealized shapes, crystal defect characterization as a function of crystal orientation, numerical modeling using the extended finite element modeling method, and lab-scale diamond wire slicing experiments will be used to investigate these effects. The findings from these investigations can be used to synthesize diamond wires with optimized grit shapes and wear behavior for use in the manufacture of high quality thin semiconductor wafers.