利用氫氣電漿清理砷化銦基板再用氧化物磊晶系統成長氧化鉿之介面特性分析

Analysis of Hydrogen plasma clean before deposition of HfO2 on InAs by Oxide MBE system with deflector interface

伍存龍(Thein Naing)

指導教授 ： 林浩雄

國立臺灣大學/電機資訊學院/電子工程學研究所/碩士(2016年)

https://doi.org/10.6342/NTU201602557

摘要

本論文利用氧化層磊晶系統(Oxide MBE system) 在砷化銦基板上成長氧化鉿的金氧半電容元件之特性分析。氧化鉿的成長方式為鉿金屬搭配氧氣電漿成長，有做氫氣電漿前置處理及沒有氫氣電漿前置處理比較; 在成長氧化層前先用氫氣電漿前置處理有效去除原生氧化物及修復浮懸鍵結(dangling bonds)鈍化(passivation)基板，減少C-V曲線延伸(stretch-out)現象。並且可有效抑制閘極漏電流密度，在-1 V時閘極漏電流密度約為1x10-6 A/cm2。利用X 光射線電子能譜儀(XPS)探討有氫氣電漿前置處理及無氫氣電漿前置處理的表面狀況，有氫氣電漿前置處理的介面原生氧化層大幅度降低。利用鉿(Hf) 4f軌域及氧(O) 1s軌域頻譜計算氧化層的品值。得Hf及O比值為1:1.95非常接近理想的1:2。沒有氫氣電漿前置處理的介面原生氧化物明顯地偵測到，在-1 V時閘極漏電流密度約為1x10-4 A/cm2，比有氫氣電漿前置處理高2個數量級。利用鉿(Hf) 4f軌域及氧(O) 1s軌域頻譜計算Hf及O比值為1:1.79。部分氧會跟基板元素結合故氧的比值較低於理想值。經金屬後退火處理後(Post Metallization Annealing)電容調變率變大，費米能階釘札(Fermi-level pinning)改善，有效改善元件特性。正反掃電容-電壓圖計算出磁滯電壓差(hysteresis)來判斷氧化層內缺陷的增減及探討邊緣缺陷(border trap)造成的累積區頻散(Accumulation frequency dispersion)的問題。
本論文亦研究使用氫氣電漿前置處理後在成長氧化層時加入導流板(deflector)偏壓去除氧氣電漿內的带電離子(ionic species)成長出缺陷較少的氧化層。有加導流板量測所得電容值較大，有效減少带電離子成長出較簿的氧化層且品質較好。在-1 V時閘極漏電流密度約為4x10-6 A/cm2。加導流板偏壓750 V的元件在金屬後退火處理前磁滯電壓差為114 mV，做金屬後退火處理後磁滯電壓差為57 mV。沒加導流板偏壓的元件在金屬後退火處理前磁滯電壓差為205 mV，做金屬後退火處理後磁滯電壓差為90 mV。加導流板有效提升元件特性。邊緣缺陷密度(border trap density)也隨著金屬後退火處理後減少。累積區頻散(Accumulation frequency dispersion)也有所改善。

關鍵字

砷化銦 ； 氧化物磊晶系統 ； 氧化鉿 ； 氫氣電漿 ； 導流板 ； 金屬後退火 ； 邊緣缺陷 ； 累積區頻散

並列摘要

In this thesis, we use Oxide MBE system to deposit oxide layers (HfO2) on InAs substrates to fabricate the Metal-oxide-semiconductor capacitor (MOSCAP). Hafnium dioxide was grown by hafnium metal source with oxygen plasma. Before depositing high κ dielectric layers, we used hydrogen plasma to remove the native oxide and passivate the substrates, which effectively reduced C-V stretch-out and suppressed the gate leakage current density, which was about 1x10-6 A/cm2 at Vg = -1 V. We used X-ray photoelectron spectroscopy (XPS) to discuss interface properties with and without hydrogen plasma pretreatment. With hydrogen plasma treatment, the XPS spectra show that the treatment can effectively reduce As-related oxides. And then, we used Hf (4f) spectrum and O (1s) spectrum to calculate the ratio of Hf and O, which is 1: 1.95. It is very close to prefect ratio, which can justify quality of oxide layers. Without hydrogen plasma treatment, the data of XPS showed the signal of native oxides distinctly. The gate leakage current density was about 1x10-4 A/ cm2 at Vg = -1 V, two order higher than that of with hydrogen plasma pretreatment. We used Hf (4f) spectrum and O (1s) spectrum to calculate the ratio of Hf and O is 1: 1.79, some portion of oxygen combined with As- and In- is not close to perfect ratio. The results show that with post metallization annealing improve device performances exhibiting larger C-V modulation, unpinned Fermi-level. By bidirectional C-V sweep, we calculated hysteresis voltage difference(ΔV), which used to determine whether oxide layer traps increasing or decreasing. The problems of border traps due to accumulation frequency dispersion will be discussed later.
In this thesis, we also use deflector bias when growing HfO2. Using the deflector can effectively reduce ionic species and get high quality oxide layer. With deflector bias, we get larger capacitances and thinner oxide layers. The gate leakage current density is about 4x10-6 A/ cm2 at Vg = -1 V. With deflector bias at 750 V, the samples showed hysteresis voltage difference is 114 mV before Post Metallization Anealing (PMA) and 57 mV after PMA. Without deflector bias, the samples showed hysteresis voltage difference is 205 mV before PMA and 90 mV after PMA. With deflector bias, it can effectively improve device performances. Border trap density and accumulation frequency dispersion are also effectively reduced by post metallization annealing process.

並列關鍵字

InAs ； Oxide MBE system ； HfO2 ； Hydrogen plasma ； Deflector ； Post Metal Annealing ； Border trap ； Accumulation frequency dispersion

參考文獻

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