二氧化鋯氧化層之磁滯現象與直/交流可靠性研究

Abstract

依據全球半導體技術藍圖的預估，未來的閘極絕緣層將會以高介電係數材料取代傳統的二氧化矽。在本論文中，吾人探討以原子層化學氣相沈積（ALCVD）之二氧化鋯氧化層，經爐管退火與快速退火處理後之特性。實驗結果顯示，後續熱處理可以改善二氧化鋯氧化層的特性，而爐管退火處理可獲致最薄之等效氧化層厚度（EOT, effective oxide thickness）與最佳之可靠性特性。 磁滯現象在高介電係數材料中十分常見，吾人對此提出一『內部介面缺陷』模型。此模型可解釋磁滯現象之光照效應與厚度相依性，並可解釋於電流電壓特性中，所觀察到之轉折點漂移現象。於直/交流電壓應力實驗中，吾人觀察到明顯的電壓應力導致漏電流（SILC）、電荷累積與假性崩潰現象。並且電荷累積時間隨交流頻率增加而減少，此係因交流頻率增加時，電荷被釋放的時間縮短所致。此外，交流電壓應力之時間導致介電層崩潰（TDDB）優於直流電壓應力，且交流頻率越高，所需之崩潰時間越長。

According to International Technology Roadmap for Semiconductor, the high K dielectrics would be used as gate dielectrics for future ULSI technology. In this thesis, The characteristics of ZrO2 oxide deposited by Atomic Layer Chemical Vapor Deposition (ALCVD) with furnace annealing or RTP annealing had been investigated. The results have shown that after thermal post-treatment, the zirconium dioxide layer exhibits superior quality. Furthermore, furnace post-treatment has the thinnst effective oxide thickness (EOT) and the best lifetime reliability. Hysteresis phenomenon is usually observed in high K dielectrics. We proposed an "inner-interface trapping model", and this model could explain the light effect and thickness dependence of hysteresis. Besides that, the shift of turnaround point in I-V characteristics is another evidence for this model. Apparent SILC, charge build-up, and soft breakdown phenomena had been observed under DC/AC stress. The charge build-up time would decrease as the frequency of AC stress increase. The reason should be the shorter detrapping time under the higher AC stress frequency. Moreover, the AC lifetime is better than DC, and increases as AC frequency increases.