原子層化學氣相沉積之高介電閘極絕緣層於矽及銻化銦基板之研究

Atomic Layer Deposition of High-k Gate Dielectrics on Silicon and Indium Antimonide

侯承浩(Chen-Hao Hou)

指導教授 ： 吳泰伯

國立清華大學/工學院/材料科學工程學系/博士(2009年)

https://doi.org/10.6843/NTHU.2009.00412

摘要

In this thesis, atomic layer deposition (ALD) will be used to deposit high dielectric constant film on Si and InSb (III-V) semiconductor substrates. Firstly, the researches are focused on the preparation of ultrathin hydroxyl (-OD) and nitric (-NH) groups on H-terminated Si by using high-reactive D2O and N2/H2 free radicals. These ALD starting layers will prevent the island nucleation at the initial cycles. The results show that in-situ radical surface pre-treatments could descend the leakage current of the metal-oxide-semiconductor (MOS) capacitor and scale down the equivalent oxide thickness (EOT) to 0.72nm. The detailed experiments and results will be discussed in Chapter 3.
Furthermore, in order to improve the thermal stability of the high-κ films grown by ALD, in Chapter 4, we propose an innovative method －“inter-layer D2O radical anneal” in which the high reactive D2O radicals are pulsed in between every two ALD cycles. The D2O radical anneal will effectively link the deposited HfO2 molecules in lateral and eliminate the un-reacted precursors, resulting both densification and purification effects on the grown films. The result shows a significant improvement that the EOT could even maintain stable at 1.0 nm after passing through 900°C PDA.
Finally, in Chapter 5, we try to passivate InSb compound semiconductor by using ALD grown Al2O3 film. An particular interfacial self-cleaning phenomenon is found in the ALD of Al2O3 on InSb substrate, using Al(CH3)3 (TMA) and H2O as the precursors. The native oxides of InSb are greatly removed from the interface through ligand exchange (substitution) reactions with the TMA precursor. Besides, intentional 100 cycles of TMA/Ar half ALD-cycle pulses and CP4A chemical clean are also applied to InSb surface before Al2O3 deposition. An Al2O3/InSb structure without residual native oxides is achieved by these surface pretreatments and in-situ self clean effect. With the removal of the native oxides from the interface, a clear transition from accumulation to depletion region and insignificant frequency dispersion are found in the capacitance-voltage relations, which reveals the releasing of the Fermi-level pinning.

關鍵字

原子層化學氣相沉積 ； 三五族化合物半導體 ； 高介電常數閘極氧化層

並列摘要

本篇論文將利用原子層化學氣相沉積的方法分別在矽基板及三五族化合物半導體基板上做高介電氧化物的沉積。首先，在矽基板上，研究將聚焦於利用水氣及氮氣/氫氣自由基，在氫鈍化保護的矽基板上分別製作一層超薄氫氧根層及氮氫根層以作為原子層化學氣相沉積之初始反應層來防止島狀成核的發生。實驗結果顯示，經由此表面預處理後，可使金屬-氧化物-半導體電容之漏電流大幅下降，等效氧化物厚度也可有效微縮至0.72奈米，此部分之結果將在第三章中討論。
為了進一步提升以原子層化學氣相沉積製作之薄膜的熱穩定性，在第四章中，我們在每兩個循環的原子層化學氣相沉積後進行重水自由基之退火處理。此自由基退火將可以有效的對氧化鉿薄膜進行橫向的連結，並且消除未反應完全的前趨物官能基，此方法可同時降低薄膜中的雜質含量以及提高薄膜之緻密性。經過自由基退火處理的氧化鉿薄膜即使經過九百度的高溫後薄膜沉積退火處理後其等效氧化物厚度仍可維持在1奈米，沒有上升。此結果和以一般原子層化學氣相沉積方式製作之薄膜有著顯著的改善。
最後，在第五章的研究當中，我們嘗試利用原子層化學氣相沉積的方式在銻化銦化合物半導體上鍍製氧化鋁作為表面披覆層。在研究中發現，三甲基鋁金屬前趨物將會與表面之原身氧化物進行官能機交換（替換）的反應並在薄膜沉積的過程中間接移除此原身氧化物，達到自我清潔的效果。除此之外，在氧化鋁薄膜沉積之前，我們亦利用了一百次的三甲基鋁/氬氣循環和CP4A化學溶液來預先清潔銻化銦基板的表面。經由此些表面處理技術以及原子層化學氣相沉積過程中特殊的原身氧化物自我清潔效應，我們可以得到一無原身氧化物殘留的氧化鋁/銻化銦結構。當原身氧化物被清除後，電容-電壓曲線呈現一個理想的累積區至反轉區的轉變以及微小的頻率分散，這代表費米能偕拴鎖現象已經解除。

並列關鍵字

ALD ； III-V compound semiconductor ； high-k dielectrics ； CMOS ； HKMG

參考文獻

1.7 J. Kwo and M. Hong, J. Crystal Growth 311, 1944 (2009)

1.8 P. D. Ye, J. Vac. Technol. A 26, 697 (2008).

1.15 K. Tomida, K. Kita, and A. Toriumi, Appl. Phys. Lett. 89, 142902 (2006).

1.17 Available on line: http://www.cambridgenanotech.com/index.php

1.19 Available online: http://www.picosun.com