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良好的抛光表面,对改善硅器件性能起着重大作用,本工作特别研究了经过等离子体抛光(干式加工)后硅的表面特性。实验表明,经过等离体抛光后,硅的原始表面损伤密度可减至最少程度,只剩下个别特别深的伤痕。相应的电子衍射实验发现与这些机械损伤相联系的带点的衍射环,随着抛光的加深而逐渐减少,当抛光深度足够深并经过氧化后,表面的机械损伤可基本消除,相应的衍射花样则是典型的硅单晶的衍射图。 其次,等离子体抛光后的样品能改善由此所形成的Si-SiO_2系统的一些电学性质,发现: ①在此抛光面上热氧化生成的SiO_2薄层的耐压强度有所提高——对同一片子取样,最大击穿电场由没有抛光的约小于1×10~6v/cm提高到抛光后大于6×10~6V/cm。 ②由MOS电容测得表面储存时间Ts由毫秒数量级提高到大于10秒的数量级。 本工作还发现一个值得注意的现象,在这种射频辐射场中进行的干法抛光会在Si表面产生一定程度的“电损伤”,电子衍射花样表明这是一种表面结构损伤,随加工时间增长而增大,严重时可使表面几十至几百埃左右的一层晶格排列严重混乱,甚至变成接近多晶以至无定形状态。有趣的是,这种“电损伤”会对随后热氧化形成的Si-SiO_2系统特性带来直接影响,使其表面固定电荷Q_(ss)与界面态N_(ss)与不经抛光的样品比较,严重
A good polished surface plays a significant role in improving the performance of silicon devices. In this work, the surface properties of silicon after plasma polishing (dry machining) are especially studied. Experiments show that after plasma polishing, the original silicon surface damage density can be reduced to a minimum, leaving only a few special deep scars. Corresponding electron diffraction experiments show that the diffraction rings with points associated with these mechanical damage gradually decrease with the deepening of the polishing. When the depth of the polishing is deep enough and the surface is oxidized, the mechanical damage of the surface can be basically eliminated. The corresponding diffraction pattern It is the diffraction pattern of a typical silicon single crystal. Secondly, the plasma-polished samples can improve some of the electrical properties of the resulting Si-SiO 2 system and found that: ① the compressive strength of the thin layer of SiO 2 produced by thermal oxidation on this polished surface has increased - Film sampling, the maximum breakdown electric field by the non-polished about less than 1 × 10 ~ 6v / cm increased to more than 6 × 10 ~ 6V / cm after polishing. ② measured by the MOS capacitor surface storage time Ts increased from the order of milliseconds to the order of magnitude greater than 10 seconds. The work also found a noteworthy phenomenon in which dry-polishing in this RF field produces some degree of “electrical damage” on the Si surface and electron diffraction patterns indicate that this is a surface structure damage that occurs with processing time Grow and increase, in severe cases can make the surface of a few tens to several hundred angstroms of the orderly arrangement of a serious disorder, and even become close to polycrystalline and amorphous state. Interestingly, this “electrical damage” has a direct effect on the Si-SiO 2 system characteristics formed by the subsequent thermal oxidation, making the surface charge Q_ (ss) and interface state N_ (ss) compare with non-polished samples ,serious