超薄钛基金属中间层实现耐热低势垒金半接触的研究

Lowering the barrier of metal/semiconductor (MS) contact is very important to reduce the contact resistivity of transistors and improve the Schottky power diode performance. However, the conventional low barrier solutions including Fermi level depinning by means of the dielectric interlayer and direct contact of rare earth metal (RE) to n-Si have not enough thermal endurance. The followed thermal process will destroy the dielectric interlayer or induce the strong reaction between RE and Si, which makes it very difficult to keep a stable low barrier. Combining the low work function RE and the ultra thin metallic interlayer, this proposal suggests making use of RE/ultra thin Ti based metallic interlayer/n-Si, a metallic bilayer MS contact (MBC) to realize the low barrier with improved thermal endurance. With a successful demonstration of the MBC structure effectiveness by an initial experiment, the project will further explore the physical mechanism of MBC with a low barrier and good thermal endurance. The influence of Ti based metallic interlayer on barrier modulation will be systematically investigated. The MBC performance will be optimized by N and O as dopants. After study, the function principles of Ti based metallic interlayer will be understood, the optimized MBC solution will be revealed too. And a MS contact with a barrier height ranging from 0.25 to 0.35eV and thermally stable after 450 degree C/30mins annealing can be obtained.

降低金半接触势垒对减小晶体管的接触电阻率和提升肖特基功率二极管的特性都非常重要。然而在n-Si上利用介质中间层解钉扎或稀土金属直接接触获得的低势垒都不耐热。后续工艺的热处理过程会破坏介质中间层或让稀土金属与衬底Si发生强烈反应，低势垒很难保持稳定。联合低功函数的稀土金属和超薄的金属中间层，本项目提出利用稀土金属/超薄钛基金属中间层/n-Si这种双层金属金半接触（MBC）来实现耐热低势垒目标。在初步实验已证明这种MBC结构有效性的基础上，项目将深入探索MBC结构实现耐热低势垒接触的物理机制；系统研究钛金属中间层对势垒调制的影响；利用N、O杂质元素优化MBC特性。通过研究，掌握钛基金属中间层的作用机理，获得优化的MBC方案，实现势垒高度在0.25-0.35eV范围且能稳定忍耐450摄氏度/30分钟热处理的金半接触。

降低金半接触势垒对减小晶体管的接触电阻率和提升肖特基功率二极管的特性都非常重要。然而在半导体上利用介质中间层解钉扎或稀土金属直接接触获得的低势垒都不耐热。后续工艺的热处理过程会破坏介质中间层或让稀土金属与衬底半导体发生强烈反应，低势垒很难保持稳定。本项目提出利用接触电极金属/超薄金属中间层/半导体这种双层金属金半接触（MBC）来实现耐热低势垒目标。研究表明；1）在i-AlGaN/GaN异质结构衬底上，巧妙利用了Ti和Al在分凝后产生的Ti中间层，实现了对AlGaN中N元素的有效萃取，首次通过使用Ti5Al1的合金在880oC热处理后获得了小于0.1欧姆-毫米的超低无金欧姆接触；2）在InGaAs的欧姆接触研究中，提出了基于超薄Pd中间层的Mo/Pd/IGA接触新结构，在不高于450oC热处理后使得接触电阻相对于传统Mo/IGA方案有20%以上的降低，且热稳定性也更佳；3）在i-AlGaN/GaN异质结构衬底上，首次通过使用Au/Ta5Al1合金叠层结构在900oC热处理后获得了0.14欧姆-毫米的超低有金欧姆接触，并揭示了一种全新欧姆接触形成机制。