利用通道背向散射理論對遠距庫倫散射遷移率之研究

Abstract

近來許多研究指出，當氧化層厚度小於2~3奈米時，等效電子遷移率會隨著氧化層厚度的減少而減少。研究認為等效電子遷移率的減少是因多晶矽閘極中的遠距電荷所產生的遠距庫倫散射所導致。利用通道背向散射理論以及建立在三角位能井理論基礎上的模擬器，我們可以從Fischetti的蒙地卡羅模擬結果中得到平均自由徑λ。透過不同情況下的等效電子速度所推得的不同平均自由徑λ，可以從中分析出由多晶矽閘極空乏區中的電荷所造成的遠距庫倫散射造成的平均自由徑λ變化量，並由此經通道背向散射理論計算得遠距庫倫散射電子遷移率。這個方法提供了一個簡單的新方式可以估算遠距庫倫散射電子遷移率μrcs，其結果與其他相關研究比較，亦合理且接近。

Many investigations point out that when the thickness of oxide layer is less than 2~3nm, the effective electron mobility will be degraded with the reduction of gate oxide thickness. It is suggested that the mobility degradation of ultrathin gate oxide devices may be caused by the Coulomb scattering from remote charge in the poly gate. Using the channel backscattering theory and triangular potential approximation simulator TRP, an important parameter mean free path λ can be fitted to the Fischetti’s Monte Carlo data. After fitting the mean-free-path λ from effective electron velocity in the different cases, we can distinguish the fraction of λ caused by the remote charge scattering due to the charge in the depletion region of the poly gate and calculate the remote charge scattering mobility μrcs with λrcs through the backscattering theory. This new method can therefore offer a simple way to estimate Coulomb scattering mobility μrcs; and the results have been corroborated proved through the comparison with the recent experiment date.