對深次微米金氧半電晶體在軟崩潰之後的1/f 雜訊之研究

Abstract

對於閘氧化層厚度3.3奈米的n通道金氧半電晶體, 將它置於定電壓破壞下, 一開始閘極電流呈現破壞導致的漏電流, 接著發生數起軟崩潰造成的閘極電流暴增, 這些軟崩潰事件分別由不同位置的電流路徑之形成所產生, 這些位置可由電性得知。在定電壓破壞過程中, 停下來量汲極電流1/f雜訊頻譜、臨界電壓和轉導係數。相對於臨界電壓和轉導係數不明顯的退化, 汲極電流雜訊在定電壓破壞過程中所發生的變化較為顯著。所量得的汲極電流雜訊在軟崩潰後發生的變化是來自於載子數量與表面載子移動率的隨機變動。在軟崩潰發生後, 軟崩潰路徑與載子通道產生顯著的交互作用, 其相關係數約10-4。值得注意的是, 汲極電流雜訊在軟崩潰後發生的變化與軟崩潰路徑上電子在缺陷間跳動有關。

For 3.3-nm thick gate oxide n-channel MOSFETs subjected to constant voltage stress, the gate current monitored initially behaves as the stress-induced-leakage-current (SILC), then followed by some sudden events due to soft breakdown (SBD). These SBD paths are appropriately located electrically. At several stress times, we characterize the 1/f noise power spectra of the drain current, Sid, as well as the threshold voltage Vth and transconductance gm. It is found that, relative to the weak dependencies of Vth and gm degradations, the Sid degradation can exponentially follow up the spontaneous evolution during the stressing. The measured Sid before soft breakdown is evidenced the carrier number and surface mobility fluctuations in the channel. The origin of the post-SBD Sid can be attributed to a significant coupling from the localized SBD percolation path to the underlying channel. The efficiency of such coupling is estimated around 10-4. In particular, a fluctuation in Sid after soft breakdown is observed for the first time, which can be consistently related to the current fluctuations due to the trapping and detrapping processes in and around the SBD paths. English Abstract…………………………………………………ii Acknowledgement……………………………………………….iii Contents…………………………………………………….……iv Figure Captions………………………………………………….vi Chapter 1 Introduction….……………………………………………………1 1.1 Soft Breakdown…………………………………………………………1 1.2 Noise….…………………………………………………………………3 1.2.1 Introduction to Noise…………………………………………..…3 1.2.2 Carrier Number Fluctuation Model………………………………4 1.2.3 Bulk Mobility Fluctuation Model………………………………...4 1.2.4 A Unified Model…………………………..……………………...5 Chapter 2 Measurement Setup and Programs..…….………………………...7 2.1 Introduction………………………………………………………………7 2.2 Noise Measurement Setup…………………………..………...…………7 2.3 Control Hp4156B by LabView Program…………………………….…..9 Chapter 3 Degraded Flicker Noise after Soft Breakdown……….………….12 3.1 Experiment…………………………………………...…………………12 3.2 Experimental Results and Discussion…………………….…………….13 Chapter 4 Detailed Analysis................................................................………..15 4.1 Results and Disscussion....…………………………...…………………15 4.2 Origin of Sid.......................................……………………………….….16 4.2.1 Before Soft Breakdown.................................................................16 4.2.2 After Soft Breakdown....................................................................17 Chapter 5 Conclusion……………………………………………………….….19 References………………………………………………………………….…..21