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据日本电视杂志1988年第10期报道,日本NTT公司研制成功采用含有氮的钨硅合金新材料作为栅电极的GaAs MESFET,这种MESFET在电流激励能力、工作速度方面超过以往的GaAs FET。 GaAs材料,由于在离子注入后的活性热处理时砷蒸发,衬底表面质量变差,因此必须制作表面保护膜。这种保护膜以前采用氮化钨、钨硅等材料,在热处理时产生结晶而成为晶粒界面限制了微细加工技术。该公司所开发的钨硅氮膜,与以前的保护膜材料不同,在800℃以上的高温下处理,不会产生结晶而保持非晶状态。由此,若能控制导电沟道表面载流子(电子)浓度,就能进行在0.25μm以下的微细加工,器件的高速化是可能的。采用在氮气气氛中的反应溅射形成膜。
According to Japanese TV magazine No. 10 of 1988, NTT Corporation of Japan successfully developed GaAs MESFETs using nitrogen-containing tungsten-silicon alloy as the gate electrode. This MESFET surpasses previous GaAs FETs in terms of current pumping capability and operating speed. GaAs material, due to evaporation of arsenic during the active heat treatment after ion implantation, deteriorates the surface quality of the substrate, so a surface protective film must be fabricated. This protective film used in the past, such as tungsten nitride, tungsten and other materials, produce heat during crystallization and become a grain boundary to limit the micro-processing technology. The company developed tungsten-silicon nitride film, with the previous protective film material, at 800 ℃ above the high temperature treatment, will not produce crystallization and remain amorphous. Therefore, if the concentration of carriers (electrons) on the surface of the conductive channel can be controlled, it is possible to perform microfabrication at 0.25 μm or less and increase the speed of the device. The film was formed by reactive sputtering in a nitrogen atmosphere.