GOALI/IUCRP: Uniform Grain Size Polysilicon for Thin Film Transistors

目标是与工业合作伙伴合作，定义低温工艺，形成均匀晶粒的硅薄膜，用于制造薄膜晶体管，以在静态随机存取存储系统（RAMS）中进行基准测试。目前，晶体管在非晶硅中实现了低泄漏，而在多晶硅中实现了载流子高迁移率。但是一种材料不可能同时提供两种理想的性能，除非使用晶体硅。研究方法是使用阳极氧化铝作为种子床，其中种子均匀间隔，使随后的多晶硅晶粒被迫具有极窄的晶粒尺寸分布，从而在薄膜晶体管中提供更紧密的阈值电压，迁移率和泄漏电流分布。第一步是使用阳极氧化形成氧化铝的铝基板，然后将Al金属化硅晶片作为基板，通过器件制造进行最终的硅晶片加工。由于底层器件的温度限制，在氧化铝上形成多晶硅的过程中，被加工的晶片不能超过350摄氏度，因此将结合非热电子辐照，以使弱结合的物质更有效地解吸或重新排序，从而为均匀颗粒硅提供新的微观结构途径。首先，在阳极化铝上生长具有单一强取向的硅种子层，其晶粒尺寸尽可能大。其次，采用高能粒子轰击辅助化学气相沉积法生长Si-on-Si厚膜，实现晶粒尺寸均匀。最后，通过低温等离子体退火或等离子体浸没离子注入实现晶界钝化。用这些硅片制造的晶体管的电性能将以超过10的10次方的开/关电流比和超过500平方厘米/ v秒的迁移率为目标进行测量。硅仍然是制造计算机、电信设备和无数电子设备的主要半导体材料。该研究项目的成功完成有可能降低许多电子应用中硅片的成本，并提高许多电子设备的效率。此外，工业合作伙伴密切合作，让大学教师和一名学生呆三个月，并派遣自己的研究人员到大学呆一年。学术界和产业界之间的思想相互交融影响了国家选择相关研究领域并将成果转化为商业部门以保持全球竞争力的能力。

9424399 Collins The goal is to define low temperature processes to form uniform grain silicon films for use in fabricating thin film transistors to be benchmarked in static Random Access Memory System (RAMS), in collaboration with industrial partners. At present, transistors in amorphous silicon achieve low leakage, while in polysilicon, they achieve carrier high mobility. But one material is not able to provide both desirable properties at the same time unless crystalline silicon is used. The research approach is to use anodic aluminum oxide as a seed bed, where the seeds are uniformly spaced so that the subsequent polysilicon grains are forced to have an extremely narrow distribution of grain sizes thereby providing a tighter distribution of threshold voltages, mobilites and leakage currents in the thin film transistors. The first step is to use aluminum substrates that are anodized to form alumina and then move on to Al metalized Si wafers as substrates for final Si wafers processing through device fabrication . Since the processed wafer must never exceed 350 degrees celcius during the polysilicon formation on alumina due to the temperature limits of the underlying devices, non-thermal electron irradiation will be incorporated to cause weakly-bound species to desorb or re-order more efficiently, thereby allowing new microstructural pathways for uniform grain silicon. First, a silicon seed layer that has a single strong preferred orientation will be grown on the anodized Al, with as grown grain size as large as possible. Second, energetic particle bombardment-assisted Chemical Vapor Deposition will be used for the thick Si-on-Si film growth to achieve uniform size grains. Finally, grain boundary passivation is achieved via either low temperature plasma-based anneals or plasma immersion ion implantation. The electrical performance of transistors built with these silicon wafers will be measured with a target to exceed on/off current ratios above 10 to the power of 10 and mobilitie s exceeding 500 square cm./V-sec. Silicon remains the workhorse semiconductor material in the manufacture of computers, telecommunication equipment and myriad's of electronics devices. Successful completion of this research project has the potential to drive down the cost of silicon wafers for many electronic applications and improve the efficiency of many electronic devices. Further, industrial partners are collaborating closely by hosting university faculty and one student for three months and sending their own researcher to the university for one year. Cross fertilization of ideas between academia and industry impacts the Nation's ability to select relevant areas for research and then transform the results into the commercial sector to maintain global competitiveness.