HfSiON閘極氧化層成份對nMOSFET之PBTI效應

PBTI Effects on nMOSFETs Having Various Compositions of HfSiON Gate Dielectrics

蘇文祥(Wen-Xiang Su)

指導教授 ： 黃恆盛 ； 陳雙源

國立臺北科技大學/機電學院/機電整合研究所/碩士(2008年)

摘要

偏壓溫度效應是金氧半場效電晶體(MOSFETs)的可靠度問題之一，早期的研究指出，主要的劣化情況是發生在施加負偏壓於p通道電晶體時，故稱負偏壓溫度不穩定性 (NBTI)，然而，隨著閘極氧化層由high-k材料取代傳統介電質，正偏壓溫度不穩定性(PBTI)影響nMOSFETs劣化的問題，已受到重視，因此理解這些可靠度問題的嚴重程度是很重要的課題。
在本研究中，我們使用來自UMC90 nm製程的nMOSFET當實驗樣本，這些電晶體之通道為90 nm，具有不同比例HfSiON(Hf:Si=3:1、1:1、1:3)之閘極介電層，厚度為20Å、介面氧化層厚度為5 Å、寬度為10 μm。我們在25℃、75℃、125℃等三種不同的溫度下，進行PBTI的加壓測試，並隨時觀察及記錄測試元件的退化情形。
研究結果發現，HfSiON閘極介電質，在PBTI模式下，隨著溫度或電壓的提高，會有較嚴重的劣化情況，且顯示主要是由氧化物陷入電荷(ΔNot)所造成，而不是介面電荷(ΔNit)。另外，在經過PBTI的應力後，Hf:Si=3:1的劣化情形是較劣於Hf:Si=1:1和 Hf:Si=1:3，而且經由模式預測，這三種比例的HfSiON之壽命，都不超過10年。

關鍵字

矽氧化鉿 ； 正偏壓溫度不穩定性 ； 退化 ； 溫度 ； 氧化物陷入電荷 ； 介面電荷

並列摘要

Biased temperature instability effect is one of the problems amidst MOSFET reliability. Early researches indicated that the main deteriorated situation is occurs when applying a negative bias to a p channel transistor, therefore it is called the negative bias temperature instability (NBTI). However, positive biased temperature instability (PBTI) induced nMOSFETs degradation has become more obvious as high-k gate oxide replacing conventional dielectrics. Therefore, it is important to understand these reliability questions.
In this research, the nMOSFET tested samples are from 90 nm technology of UMC. The nMOSFETs transistors have Lg = 90 nm, different compositions ( Hf:Si = 3:1, 1:1, and 1:3) of HfSiON gate dielectrics with 20Å thickness plus chemical oxide 5 Å. Stress conditions were set at temperature 25℃、75℃ and 125℃. Degradation of tested devices were measured and recorded during the stress.
From the tested results, it is found that the nMOSFETs exhibit more serious degradation with the enhancement of temperature and stress voltage. The generation oxide trapped charges (ΔNot) rather than the interface trapped charges (ΔNit) is the main cause. In addition, the Hf:Si=3:1 deteriorated situation is worse comparing to Hf:Si=1:1 and Hf:Si=1:3 after PBTI stress. Furthermore, the lifetime of all kinds of HfSiON does not surpass 10 years expectation after applying model analysis.

並列關鍵字

HfSiON ； NBTI ； Degradation ； Temperature ； oxide bulk trapped charges ； interface charge

參考文獻

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