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片中，利用涂有金刚石磨料的细钢丝组成的移动钢丝网，将非常坚硬和易碎的材料（如晶体硅和蓝宝石）切割成薄晶片。这些晶圆被用作光伏太阳能电池和节能照明设备（如发光二极管）的衬底。虽然固定磨料金刚石线切片工艺可能比现有的半导体晶圆切片方法提供更高的生产率，但缺乏其成本效益应用和优化所需的科学知识。这项“与工业界学术联系资助机会”（GOALI）奖支持基础研究，这些研究将产生生产高质量光伏太阳能硅衬底所需的科学知识，同时将机械损伤降到最低。由于高质量的晶片在太阳能电池制造过程中不易破损，因此从本研究中获得的知识将降低太阳能电池的生产成本，从而降低太阳能成本。这将直接使美国经济和整个社会受益。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，其中金刚石线切片工艺用于切割其他半导体和光学材料。研究涉及先进制造、材料科学、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，从而有助于培养下一代先进制造业工程师。该研究团队将专注于了解和最小化用于光伏太阳能电池衬底的微结构复杂晶体硅材料在金刚石丝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粒度几何形状、晶体取向和缺陷（如晶粒/孪晶界、位错密度变化）以及金刚石粒度磨损对单晶和多晶太阳能硅材料金刚石丝切割过程中产生的切削模式（韧性与脆性）、表面形态和亚表面损伤的影响。使用理想形状的金刚石压头进行单粒金刚石刻划实验，将晶体缺陷表征作为晶体取向的函数，使用扩展有限元建模方法进行数值模拟，并使用实验室规模的金刚石线切片实验来研究这些影响。这些研究结果可用于合成具有优化粒度形状和磨损性能的金刚石线，用于制造高质量的薄半导体晶圆。

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.