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

本研究旨在用气体代替栅绝缘层实现抗辐射金属-气体-半导体场效应晶体管(MGSFET)。栅极高击穿电压和器件可靠性的额外影响是可以预期的。以SF_6气体为代表的高压绝缘在电力变压器中的应用由来已久，但在集成电路领域应用于场效应管的研究尚不多见，2005年选择了一种需要去除的绝缘体材料及其腐蚀液来实现器件结构。一套Si3N4和热磷酸被证明是不够的，因为热磷酸对硅衬底表面进行了反向刻蚀。在此基础上，选择了一套SiO_2和缓冲的HF溶液。2006年，利用所开发的技术，成功地制作了一种氮气栅绝缘型MGSFET，实现了FET的正常工作。这可能是气体绝缘FET在世界上第一次取得成功。在MOS和MGS晶体管强制栅击穿后，MOS的栅漏电流变大，而MGS的栅漏电流变小。这意味着MGS具有潜在的抗宇宙射线辐射和热载流子效应的抗辐射特性。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