DEVELOPMENT OF NANO-CBN THIN FILM DEVICES WORKING AT HIGH-TEMPERATURES UNDER SEVERE CONDITIONS

能在高温下工作的半导体器件越来越受到人们的重视。这些装置将在更高的工作温度下应用于飞机喷气发动机和大型发电机的控制单元，作为整个系统提供更高效和可靠的性能。具有宽带隙和高导热性的半导体可以在自然界中实现这些应用，而GaN， SiC和金刚石被许多研究人员列为良好的候选者。其中，立方氮化硼（cBN）在III-V族和IV-族半导体中具有最宽的带隙，并且具有较高的化学稳定性和导热性，因此被认为是最适合这些应用的材料。大约在10年前，我们成功地用ICP-CVD和溅射方法沉积了这种cBN薄膜。从那时起，我们一直被公认为领先集团之一。基于这一领域的可靠记录，重要的发现和进步已经在这个项目中取得了…该项目的第一个主要成果是在硅衬底上制备了cBN薄膜，抑制了非晶间层的形成。这种仅通过硅的t-BN相生长的cBN是通过使用ICP-CVD方法的时间相关偏倚技术（TDBT）的发明实现的。在硅上外延生长cBN将是未来大面积、高质量合成cBN的重大突破，因此该工艺对实现这一目标至关重要。氮化硼纳米阵列（BNNA）在纳米尺度上的弹性变形的发现是透射电子显微镜（TEM）观察到的第二个重要发现。这种特殊的变形是在sp^2键合的涡轮氮化硼（tBN）中产生的，用ICP-CVD建立在硅的薄边缘上。该阵列的可逆最小弯曲曲率半径约为0.3 nm。这种独特的弹性变形是传统的陶瓷和金属变形理论无法解释的，需要进一步的研究来深入了解其机理。在微机电系统和各种纳米级器件中作为减震器或相关缓冲器仍具有应用潜力。作为第三个主要成果，我们已经用cBN制作了一个高温半导体原型器件，以证明在新开发的超清洁溅射系统中加工的薄膜具有高潜力和高质量。该器件具有cBN和硅之间的异质结二极管结构，在室温下的整流比超过10^4，工作温度可达570K。从以上可以看出，本项目的总体目标取得了相当大的进展，目前取得的结果也清楚地证明了这种方法的可行性。少

Increasing attention has been paid to the semiconductor devices that can work at high temperature. These devices will be applied to the control units for aircraft jet engines and giant power generators at higher operating temperatures, offering more efficient and reliable performances as the total system. Semiconductors with wide bandgap and high thermal conductivity can realize these applications in nature and GaN, SiC and Diamonds are listed as good candidates by many researchers. Among these, cubic boron nitride (cBN) has the widest bandgap in III-V and IV- group semiconductors as well as high chemical stability and thermal conductivity, and hence is considered to be the most suitable material for these applications. About 10 years ago, we succeeded to deposit such cBN thin films both by ICP-CVD and sputtering methods. Since then, we have been recognized as one of the leading groups. Based firmly on this proved track records in this field, important findings and advancements have be … More en achieved in this project.The first major achievement in this project is the fabrication of cBN thin films on silicon substrate suppressing amorphous interlayer formation. Such cBN growth only through the t-BN phase from silicon was realized by an invention of time-dependent-bias-technique (TDBT) using ICP-CVD method. Epitaxial growth of cBN on silicon will be a major breakthrough for the large area, high-quality synthesis of cBN in future, so this process will be essential to reach this goal.The discovery of the elastic deformation of boron nitride nano array (BNNA) in nano-scale is the second important finding, observed by the transmission electron microscopy (TEM). The peculiar deformation was caused in sp^2-bonded turbostratic boron nitride (tBN), built on a thin edge of silicon by ICP-CVD. The reversible minimum-bending curvature radius of the arrays was found to reach approximately 0.3 nm. Such an unique elastic deformation can not be explained by the conventional theory of deformation of ceramics and metals, and requires further investigation for thorough understandings of the mechanism. Still it can possess the potential of being applied in both MEMS and various nano-scale devices as shock absorber or relevant buffers.As the third major result, we have fabricated a prototype device of high temperature semiconductor with cBN to demonstrate the high potential and high quality of the films processed in a newly developed ultra-clean sputtering system. This device has the structure of heterojunction diode between cBN and silicon and has exhibited the rectification ratio over 10^4 at room temperature, capable of working up to 570K.From the above, it can be seen that considerable progress was made towards the overall goal of this project, and the results obtained so far clearly demonstrate the feasibility of this approach. Less