氧氣退火對二氧化鉿nMOSFET熱載子可靠度的影響

Effect of Oxygen Annealing on Hot-Carrier Reliability of HfO2 nMOSFETs

蕭美宜(Mei-Yi Hsiao)

指導教授 ： 陳雙源 ； 黃恆盛

國立臺北科技大學/機電學院/機電整合研究所/碩士(2011年)

https://doi.org/10.6841/NTUT.2011.00293

摘要

在目前的IC製程中，金氧半場效電晶體(MOSFET)為了避免短通道效應，其介電層的厚度也越來越薄，導致更大的漏電流及可靠度問題，因此使用高介電係數材料為不可避免的趨勢。在高介電係數材料中，含有鉿（Hf）成分的材料被認為極有應用的潛力。而過去研究指出，添加氧氣進行沉積後退火，能修補介電層中的氧缺陷，使元件在偏壓不穩定性之可靠度測試能有所改善，但卻極少有探討添加氧氣退火對二氧化鉿介電層之熱載子效應及基本電性的影響，因此，我們將針對此方面做一探討。
實驗元件是聯華電子所提供45奈米製程的n型電晶體（nMOSFET），二氧化鉿介電層的製作方式是由原子層沉積技術完成。實驗考慮的參數，包括改變電壓、溫度以及不同通道長度等，再依據所得資料，進行統計、分析實驗結果與電壓及溫度的關係，且探討有無添加氧氣進行沉績後退火之間的差異。
研究結果顯示，添加氧氣進行沉積後退火，對於二氧化鉿介電層在基本電性分析上，並沒有較大差異的改善，其相似的電容-電壓曲線，使得等效氧化層厚度也雷同。而在CHC的加壓測試條件下，短通道(0.1μm)元件劣化程度明顯比長通道(10μm)嚴重，且依據實驗數據及分析，添加氧氣進行退火之n型電晶體元件，經由添加氧氣於退火製程，臨界電壓偏移量及汲極電流劣化量能有效降低，進而改善元件劣化程度。

關鍵字

氧缺陷 ； HfO2 ； 熱載子效應 ； 高介電材料

並列摘要

In order to avoid the short channel effect in the MOSFET, the thickness of the dielectric has gradually become thinner. However, the serious problems of leakage current and reliability due to the thinning oxide are also unavoidable. Therefore, using high-k materials passes into one of the most significant studies. After many years of researches, the Hafnium-based high-k materials emerge as the most promising candidates to replace SiO2 and SiON gate dielectrics. It has been reported that the oxygen vacancy defects of high-k dielectrics can be passivated by annealing process, and the device degradation of bias temperature instability (BTI) tests can be improved. However, the hot carrier injection (HCI) is still an important reliability issue. And only few literatures concerned about the channel hot carrier reliability for adding oxygen in post-deposition annealing. Hence, this study is concentrated on this subject.
The nMOSEFT experimental samples were fabricated from 45 nm node high performance logic technology of UMC. The process of HfO2 dielectric layer was deposited by atomic layer deposition (ALD). The wafers were then annealed with and without oxygen after ALD. The channel width of the nMOSFETs is 10 μm and channel lengths are 10 μm and 0.1 μm. In this research, the different stress voltages and temperatures are included in the experiment. Consequently experimental data are used to figure out the dependence of degradation on stress voltage and temperature, and to determine the difference of two kinds of wafers.
The experimental results show that the basic electric characteristics have no significant improvement for the process with oxygen post-deposition annealing. After the CHC stress, the degradation in those short channel nMOSFETs reveals larger than that in long channel. The threshold voltage shift becomes larger as stress voltage and temperature increasing. From the analyzed data, the process with oxygen post-deposition annealing can effectively reduce the degradation of the devices; it should be due to the passivation of oxygen vacancies during the oxygen annealing.

並列關鍵字

HfO2 ； Oxygen vacancy ； Channel hot carrier effect (CHC) ； High-k dielectric

參考文獻

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