探討快閃記憶體元件製程中氫氣濃度對可靠度特性影響分析之研究

Abstract

本篇論文研究兩個不同氫氣濃度的製程對快閃記憶體元件可靠度的影響。我們比較兩種不同氫氣濃度的可靠度特性，以此去了解氫氣濃度對表面能態以及臨界電壓在資料保存測試中的變化。比較高的氫氣濃度可以提供比較多的氫氣和氫分子去降低矽與氧化層介面的表面能態。從我們研究得知在較長的周期區間中，可以藉由把氫氣濃度從4%提高到100%去降低約15.5%的表面能態。我們也從實驗中也發現比較高的氫氣濃度會有比比較低得氫氣濃度擁有更好的可靠度。除此之外，兩個不同氫氣濃度的製程都表現出在較長的周期區間會有更嚴重的轉導與次臨限擺幅的劣化。因此在資料保存測試中，大量的表面能態會劣化臨限電壓對週期區間的依賴程度，尤其是在低氫氣濃度的情況下更為嚴重。

In this thesis, we investigate the reliability of two different hydrogen concentration processes. The impacts of hydrogen concentration on interface state density and VT shifts after bake are studied by comparing two different hydrogen concentration. Higher hydrogen concentration provides more hydrogen molecular and hydrogen atoms to passivate the interface states at Si/SiO2 interface. The interface state density can be reduced around 15.5% in long interval by increasing hydrogen concentration from 4% to 100%. In our measurements, higher hydrogen concentration shows better reliability than lower hydrogen concentration. Moreover longer interval during cycling shows worse transconductance (Gm) and subthreshold swing (SS) degradation in both processes. In retention test, large interface states density would degrade the interval dependence of VT shifts after bake especially in lower hydrogen concentration.