Study in Metal-Gas-Semiconductor Field-Effect Transistor with High Radiation Hardness

本研究旨在以气体取代栅极绝缘子氧化物，实现具有辐射硬度的金属-气体-半导体场效应晶体管（mgset）。栅极高击穿电压和器件可靠性的附加影响是可以预期的。以SF_6气体为例的高压绝缘早已应用于电力变压器，但在场效应晶体管上的应用在集成电路领域尚未公开。2005年，我们选择了一种需要去除的绝缘体材料及其蚀刻溶液来实现器件结构。由于热磷酸对硅衬底表面有不利的腐蚀作用，证明了一组Si_3N_4和热磷酸是不够的。因此，选择了一套SiO_2和缓冲HF溶液。2006年，利用所开发的技术，成功地获得了具有氮气气栅绝缘的mgfet，并使其正常工作。这可能是世界上第一个气体绝缘FET的成功。MOS和MGS晶体管在强制栅极击穿后，MOS的栅极漏电流变大，而MGS的栅极漏电流则小得多。这表明MGS具有抗宇宙射线辐射和热载子效应的辐射硬度特性。和

This study is to aim at realization of metal-gas-semiconductorfield-effect transistor (MGSFET) with radiation hardness by replacing gate insulator oxide by gas. Additional effects of high breakdown voltage of the gate and device reliability can be expected. High voltage insulation with, for example, SF_6 gas has long been applied to power transformer, however, the application to field-effect transistor in not yet disclosed in integrated circuit field.In 2005, an insulator material to be removed and its etching solution were chosen to realize the device structure. A set of Si_3N_4 and hot-phosphoric acid was proven to be inadequate because that the hot-phosphoric acid adversely etched silicon substrate surface. Thus, a set of SiO_2 and buffered HF solution was chosen.In 2006, utilizing the developed techniques, an MGSFET with N_2 gas gate insulation was successfully obtained resulting in normal FET operation. This may be the world-first success for gas-insulated FET. After forced gate breakdown of MOS and MGS transistors, the gate leakage current becomes bigger for the MOS, otherwise, much smaller for the MGS. This implies MGS has a potential of radiation-hardness characteristics against cosmic-ray radiation and hot-carrier effect. and