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

非技术：几十年来，硅金属氧化物半导体一直是电子设备的工业标准。然而，新的非硅薄膜半导体金属氧化物近年来获得了突出的地位。它们是一种很有前途的电子设备新技术，尤其是下一代显示器。氧化物电子具有高载流子迁移率，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设备兼容。根据主要载流子是电子还是空穴，掺杂的半导体是n型还是p型。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实现高性能p型和n型氧化物半导体的科学问题。这反过来又将使低温加工柔性CMOS逆变器和其他电路的发展成为可能。基本器件物理以及热力学和动力学考虑是实现氧化物原位合成和CMOS器件制造的关键组成部分。在贝勒大学，基础材料加工和设备制造的结合对课堂内外的教育产生了影响。低成本金属氧化物技术是电子材料与器件本科课程中原型制造实验室的理想选择。学院与本地工业的紧密联系将进一步提升学生的专业培训经验的价值。该项目还包括向当地学校推广，例如为中学生和高中生举办的德克萨斯州中央科学与工程年度博览会。技术方面：最近几种宽禁带氧化物半导体的发展和基本薄膜晶体管（TFT）结构的制造引起了人们对柔性电子和高性能薄膜晶体管应用的关注。然而，这些氧化物TFT器件的研究工作目前仅限于n型氧化物TFT。最近，有前途的p型氧化物已经出现，为探索在氧化物基互补金属氧化物半导体（CMOS）器件中的应用提供了机会。可重复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器件的发展，并将开拓新的氧化物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型半导体的新兴候选者。然而，由于SnO2 （n型）的形成和金属Sn的沉淀，p型SnOx的生长条件被认为是狭窄的。本研究提出了在200℃以下低温(T)下合成p型氧化物半导体的可重复性方法。低- t (200 ？C)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具有n型In(Ga)ZnO的热力学稳定性。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器件将在原位制造。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，结果将确定基于缺陷的p-氧化物掺杂机制。从这些研究中获得的信息将仔细地与TFT和CMOS器件性能相关联，以了解合成，组成，材料性质和器件特性之间的关系。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.