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本文将讨论MOS电容中辐照及高电场隧道注入的实验结果。与辐照剂量有关的禁带中央电压的漂移仅仅是由空穴俘获引起。在隧道注入的情况下,由碰撞离子化引起的电子-空穴对的产生需要很大的电子密度和强电场。因此,所建立的电荷产生模型考虑到了中性氧化层中的空穴俘获,其次考虑了在带正电的状态中的电子俘获以及被俘获的电子的排空。利用这种模型,只要精确地知道了碰撞离化系数α,就能够对MOS器件的抗核辐照强度进行预测。假如不是这种情况,则需利用电离辐照和隧道注入的混合技术来确定与电场强度F相关的碰撞电离系数α=α_0 exp(-Hα/F)。利用实验结果与该模型相拟合的方法,就可分别导出电子俘获截面σn和排空截面βn,得到σn依赖于F~(-3)和βn依赖于exp(-Hβ/F)的关系。发现工艺参数的变化对其影响是很小的。提出的这个模型是通过一系列的辐照和注入实验验证的。氧化层电荷的产生伴随界面态密度分布的增加,在两种实验中,它的峰值是在禁带中央之上约0.15eV处。结果表明,界面态的产生与俘获的空穴数成正比。注入实验得到了如下的界面态类型,受主型界面态在禁带中央之上,施主型界面态在禁带中央之下。这进一步证实了禁带中央电压的变化是判断氧化层电荷变化的分类点,因为在禁带中央,界面态变成中性的了。
This article will discuss the experimental results of tunneling with high electric fields in MOS capacitors. The drift of the center band gap associated with the dose of radiation is only caused by hole trapping. In the case of tunnel injection, the generation of electron-hole pairs caused by collision ionization requires a large electron density and a strong electric field. Therefore, the established charge generation model takes into account hole trapping in the neutral oxide layer, followed by consideration of electron trapping in the positively charged state and evacuation of trapped electrons. With this model, as long as the collision ionization coefficient α is accurately known, it is possible to predict the anti-nuclear irradiation intensity of the MOS device. If this is not the case, a hybrid technique of ionizing radiation and tunneling is required to determine the impact ionization coefficient α = α_0 exp (-Hα / F) that is related to the electric field strength F. By fitting the experimental results with this model, the electron capture cross sections σn and the empty cross sections βn can be deduced, and the dependence of σn on the dependence of F ~ (-3) and βn on exp (-Hβ / F) is obtained. It is found that the change of process parameters has little effect on it. The proposed model is verified by a series of irradiation and injection experiments. Oxide charge generation is accompanied by an increase in the density of interface states, and in both experiments it peaks at about 0.15 eV above the center of the forbidden band. The results show that the generation of interface states is proportional to the number of trapped holes. The experimental results show that the interface state of the acceptor type is above the center of the forbidden band and the donor interface state is below the center of the forbidden band. This further confirms that the change in central voltage of the forbidden band is a classification point for judging the charge change of the oxide layer because the interface state becomes neutral at the center of the forbidden band.