The Study of Cerium-based Gate Dielectrics, Hafnium-based Gate Dielectrics, and Interpoly oxynitride
KUO CHENG CHIANG.
|關鍵字:||二氧化鈰;二氧化鉿;複晶矽氮氧化層;電漿處理;高介電材料;光觸媒;CeO2;HfO2;SiNO;plasma treatment;high-k material;Photocatalyst|
在論文中，用快速退火處理二氧化銫絕緣層可以有效改善絕緣層特性。根據實驗的結果,快速退火可以有效消除絕緣層中的缺陷和Si基材中的介面層,進而改善二氧化銫的品質和可靠度。除此我們也研究了二氧化鈰閘極漏電對溫度的相關性,及 F-N 和 F-P特性,進而從這些數據中我們提出Al/CeO2/n-Si 的能階圖和電子傳遞的機制。我們發現沒有經過處理的試片是由F-P主導,而隨著高溫退火處理,會逐漸轉為F-N主導.因為絕緣層中的缺陷已被退火處理消除。
For the system on a chip (SOC) application, a continuously scaling of interpoly dielectrics for electrically-erasable programmable read only memory (EEPROM) and gate dielectrics for complementary metal oxide semiconductor (CMOS) is needed to have high density and low operation voltage. To meet the above requirements and exhibit a low leakage current and a good reliability, the replacement of high dielectric constant (high-k) materials for silicon dioxide and additional treatment have become indispensable. In this thesis, the improved characteristics of ultra–thin cerium dielectrics with rapid thermal annealing are investigated. Based on the experimental results, the rapid thermal annealing can effectively improve the reliability and quality of the cerium dioxide owing to the elimination of traps in the dielectrics and interfacial layer between CeO2/Si.Besides, we also report the temperature dependence of gate leakage current, Frenkel-Poole (F-P) conduction and Fowler-Nordheim (F-N) tunneling characteristics, from which we deduce the energy band diagram for Al/CeO2/n-Si structure as well as its current transport mechanisms for the first time. Besides, the experimental results shows that F-P conduction dominants the as-deposited sample, and as the RTA temperature increases, the F-N tunneling become more important owing to the elimination of traps in the dielectrics. Furthermore, for the first time, we present that irradiated TiO2 Photocatalyst can obviously improve the HfO2 with post NH3 plasma treatment, including of lower gate leakage current, higher breakdown electric field, better reliability, and longer 10-year lifetime. It is because that irradiated TiO2 Photocatalyst can induce a lot of electron traps owing to the O-H and N-H bonds breakage, which results in more obvious improvement of the HfO2 film prepared with NH3 plasma treatment. It is reported that the hydrogen-related traps (-H,-OH and –NH) provided by NH3 in the dielectrics can cause fairly high fixed charge (Qf), trapped charge (Qot),and interface state density (Dit) , which can result in serious reliability issue. Finally, the interpoy-dielectrics deposited by LPCVD nitride and then prepared with N2O RTA and followed by N2O plasma treatment were studied. N2O plasma treatment can cause the reoxidation of the nitride film to form a SiOxNy, which exist at the top of nitride (near the polyⅡ).Although the effective oxide thickness of the oxynitride film slightly increases after N2O plasma treatment, it is found that the samples after the process of N2O plasma treatment exhibit obviously higher breakdown field, lower leakage current, longer time-to-breakdown, and larger effective barrier height than the control samples. Moreover, the improvement is more apparent under negative bias(gate injection). Unfortunately, N2O plasma treatment can bring about plasma damage, which leads to higher gate voltage shift due to higher electron traps and defects. In sum, the oxynitride treated by N2O RTA and N2O plasma treatment is still suitable for use in the next generation on EEPROM.
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