- 學位論文
氧化鉿/氧化鋁/銻化鎵金氧半結構製備與界面缺陷之研究
Interfacial Electrical Properties of HfO2/Al2O3/GaSb MOS Capacitors Prepared by Atomic Layer Deposition
摘要
隨著科技進步，對於元件效能需求的提高，互補式金氧半場效電晶體的尺寸逐漸微縮，矽材料與閘極氧化層將面臨其物理極限，以三五族材料搭配高介電常數氧化層來取代目前現有矽基電晶體是目前眾人研發的趨勢之一。但是對三五族材料來說，氧化層與半導體界面缺陷的問題仍是目前最需要深入研究的一項課題。本論文即針對此課題，提出兩個有效降低高介電材料/銻化鎵界面缺陷之方法，並分析其金氧半結構之電氣特性。 本論文中首先聚焦於開發臨場沉積的氧化鉿/氧化鋁(5 nm/1 nm)雙層膜於銻化鎵上，希望藉由磊晶後直接於高真空腔體中傳輸的方式，防止表面原生氧化層生成，以降低界面缺陷。研究結果顯示，以此方式製作的金氧半電容，室溫下電容調變率約為31%，界面能態密度約為5.27×1012 eV-1cm-2。 本論文亦提出利用氫氣電漿清理銻化鎵表面的方法，以氫原子與表面原生氧化物進行化學反應，進而去除原生氧化層。實驗結果顯示，在適當的條件下，此方法同樣能達到降低界面缺陷的效果，室溫下電容調變率約為36 %，界面能態密度約為3.81×1012 eV-1cm-2。利用此兩種氧-半界面處理方式有助於元件閘極通道之調控能力，改善次臨界擺幅等電氣特性，使三五族金氧半場效電晶體之實用化再進一步。
並列摘要
According to Moor’s law, the density of transistors on a single integrated circuit chip doubles every 18 months. However, the gain in cost and performance is not commensurate with simple dimension scaling anymore because Si-based transistors are approaching their physical limit, especially in the sub-10 nm regime. This has prompted great interest in high mobility III-V compounds as alternatives of transistor channel materials. However, the native oxides of III-V compounds are complex in structure and composition. They form defects at the oxide-semiconductor interface and hinder the construction of ideal metal-oxide-semiconductor field-effect transistors. In this study, two methods are successfully used to suppress the defect state density of high-κ/GaSb interface as demonstrated in the metal-oxide-semiconductor capacitors (MOSCAPs). The HfO2/Al2O3 bi-layer oxide films used in this study are deposited on GaSb samples in an atomic layer deposition system that is connected to a molecular beam epitaxy system with ultra-high vacuum transfer chambers. With this tool, the as-grown GaSb can be transferred to the atomic layer deposition system for high-κ deposition with no or little surface native oxides. The MOSCAPs prepared by this method show effective capacitance modulation of 31 % with interface state density of 5.27×1012 eV-1cm-2 at 300 K. Hydrogen plasma treatment is another method proposed to clean the surface of GaSb before high-κ dielectric deposition. The native oxide on GaSb, which has been exposed to air, is effectively removed through the chemical reactions with hydrogen radicals. The MOSCAPs prepared by this method show effective capacitance modulation of 36 % with interface state density of 3.81×1012 eV-1cm-2. The result obtained in this work is encouraging toward the realization of GaSb MOSFETs with high on/off ratio and low sub-threshold swing.