P-type Oxides for CMOS Devices: Thermodynamics-based In-situ Synthesis and In-Situ Integration

非技术性：几十年来，硅金属氧化物半导体一直是电子设备的行业标准。然而，近年来，新的非硅薄膜半导体金属氧化物获得了突出的地位。它们是电子设备，特别是下一代显示器的一项很有前途的新技术。氧化物电子具有很高的载流子迁移率，使它们能够有效地传导电流，并且可以在低温下制造。这使得它们与柔性电子产品兼容。掺杂的半导体是n型还是p型，这取决于大多数载流子是电子还是空穴。绝大多数薄膜氧化物半导体是n型的，这限制了它们在单极器件中的应用。使用互补金属氧化物半导体(CMOS)技术开发更复杂的电路需要p型和n型器件。该项目的目标是解决阻碍高性能p型和n型氧化物半导体实现的科学问题。这反过来将使低温处理柔性cmos反相器和其他电路的开发成为可能。基本的器件物理以及热力学和动力学方面的考虑是实现氧化物的原位合成和制造CMOS器件的关键组成部分。在贝勒大学，基础材料加工和器件制造的结合在课堂内外都产生了教育影响。低成本金属氧化物技术是电子材料和器件本科课程原型制造实验室的理想选择。PI与当地行业的紧密联系将进一步提升学生专业培训体验的价值。该项目还包括与当地学校的接触，例如每年为初中生和高中生举办的德克萨斯州中部科学与工程博览会。技术：几种宽禁带氧化物半导体的最新发展以及基本薄膜晶体管(TFT)结构的制造在柔性电子产品和高性能TFT中的应用引起了人们的关注。然而，目前对这些氧化物TFT器件的研究仅限于n型氧化物TFT。近年来，前景看好的p型氧化物的出现为探索氧化物基互补金属氧化物半导体(CMOS)器件的应用提供了机会。可重复的p型氧化物半导体及其TFT器件的发展将极大地加速柔性电子学的发展，并将开创新的氧化物CMOS器件的发展。简单的二元氧化物(SnOx，1x2)由于可能形成NS2杂化轨道而成为p型半导体的候选材料。然而，由于SnO2(n型)的形成和金属锡的析出，p型SnOx的生长条件被认为是狭窄的。这项研究提出了在200℃以下的低温下合成p型氧化物半导体的可行方法。低T(200℃)原位合成p型SnOx(1x2)是金属化材料与SnO2接触时热力学不稳定的结果。相同的金属化材料必须是热力学稳定的n型In(Ga)ZnO。这种独特的原位方法为合成p型氧化物的复杂挑战提供了简单的解决方案：p型和n型氧化物TFT的金属化，以及低T退火工艺(提高TFT性能所必需的)。因此，氧化物CMOS器件将被原位制造。该项目还包含控制空穴载流子密度的策略。高压氧化的使用将载流子密度与氧逸度(即有效反应性)联系起来，结果将确定p-氧化物的基于缺陷的掺杂机制。从这些调查中获得的信息将与TFT和CMOS器件性能仔细关联，以了解合成、成分、材料特性和器件特性之间的关系。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Nontechnical:Silicon metal oxide semiconductors have been the industry standard in electronic devices for decades. However, new non-silicon thin film semiconducting metal oxides have gained prominence in recent years. They are a promising new technology for electronic devices, particularly next generation displays. Oxide electronics have high carrier mobility, allowing them to conduct current efficiently, and can be fabricated at low-temperatures. This makes them compatible with flexible electronics. Doped semiconductors are n-type or p-type, depending upon if the majority charge carriers are electrons or holes. The vast majority of thin film oxide semiconductors are n-type, which limits their applications to unipolar devices. The development of more sophisticated circuits using complementary metal-oxide-semiconductor (CMOS) technology requires both p- and n-type devices. The goal of this project is to resolve the scientific questions that prevent the realization of high performance p- and n-type oxide semiconductors. This in turn will enable the development of low-temperature processed flexible CMOS inverters and other circuits. Fundamental device physics together with thermodynamic and kinetic considerations are the key components to enable in-situ synthesis of the oxides and fabrication of CMOS devices. The combination of fundamental materials processing and device fabrication has educational impacts in and out of the classroom at Baylor University. Low cost metal oxide technology is ideal for a prototype fabrication lab in an undergraduate course on electronic materials and devices. Strong connections between the PI and local industry will further enhance the value of the professional training experience for students. The project also includes outreach to local schools, such as The Annual Central Texas Science and Engineering Fair for middle and high school students.Technical:The recent development of several wide bandgap oxide semiconductors and the fabrication of basic thin film transistor (TFT) structures have garnered attention for applications in flexible electronics and high performance TFTs. However, research efforts of these oxide TFT devices are currently limited to n-type oxide TFTs. Recently, promising p-type oxides have emerged providing the opportunity to explore applications in oxide-based complementary metal-oxide-semiconductor (CMOS) devices. The development of reproducible p-type oxide semiconductors and their TFT devices will greatly accelerate flexible electronics and will pioneer the development of new oxide CMOS devices. A simple binary oxide (SnOx, 1x2) is an emerging candidate for a p-type semiconductor due to the possible formation of ns2 hybrid orbitals. However, the growth conditions for p-type SnOx are believed to be narrow, due to the formation of SnO2 (n-type) and the precipitation of metallic Sn. This research suggests reproducible approaches to synthesize p-type oxide semiconductors at low temperatures (T) below 200 ?C. Low-T (200 ?C) in-situ synthesis of p-type SnOx (1x2) is a consequence of the thermodynamic instability of the metallization material in contact with SnO2. The same metallization material must be thermodynamically stable with n-type In(Ga)ZnO. This unique in-situ approach offers simple solutions to the complex challenges of synthesizing p-type oxides: the metallization of both p- and n-type oxide TFTs, and the low-T annealing processes (necessary for improving TFT performance). As a result, oxide CMOS devices will be fabricated in situ. This project also contains strategies for controlling hole carrier densities. The use of high pressure oxidation relates carrier density to the oxygen fugacity (i.e., effective reactivity), and the results will identify the defect-based doping mechanisms for p-oxides. The information obtained from these investigations will be carefully correlated with TFT and CMOS device performance in order to understand the relations between synthesis, composition, material properties and device characteristics.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.