以電漿增強式化學氣相沈積法成長奈米矽晶及其特性研究

Abstract

我們成功以PECVD與成長後高溫熱退火製程在矽基板上成長內含奈米矽晶的富矽氧化矽薄膜，量測光激螢光頻譜、XPS能譜和TEM觀測，確定了奈米矽晶的存在，並且分別改變成長氣體流量(SiH4/N2O)、高溫熱退火溫度和成長時PECVD的功率，再透過各種量測研究其對奈米矽晶的影響。 發現當固定N2O氣體流量並增加SiH4流量時，矽晶顆粒因流量變動而變大造成發光波段會有紅移現象且強度先升後降。也發現隨著高溫熱退火溫度改變，當退火溫度達到特定溫度以上時，可使薄膜中矽鍵結的方式從Random Bonding Model (RBM)主導轉變成Random Mixture Model(RMM)主導，使得成晶明顯且有助於減少缺陷，讓PL強度增強，也隨著退火溫度增加造成晶粒變大，使得PL頻譜紅移。並改變成長PECVD時的功率，隨著功率上升，會使得成長晶粒變小且密度上升，讓PL頻譜有藍移且增強的現象產生。

We have successfully fabricated Si nanocrystal embedded in Si-rich Oxide thin films on Si substrates by the processes of PECVD and the post-annealing. The existence of Si nanocrystal has been demonstrated by Photoluminescence(PL), X-ray Photoelectron Spectrum(XPS) and Transmission Electron Microscopy(TEM). And we also changed the gas flow rate of (SiH4/N2O), the temperature of annealing and the RF power of PECVD and then discussed about the influence on Si nanocrystal. In this thesis, we observed that with increasing of the gas flow rate (SiH4/N2O), the PL peak blueshifts and the intensity increases first and then decreases. This effect is due to the increasing of the Si nanocrystal size with the increasing flow rate. And we also found that with rising of the annealing temperature, the major bonding way of Si atoms is transferred from Random Bonding Model (RBM) to Random Mixture Model (RMM) which makes Si nanocrystal more remarkable and fewer defects in the films. It also makes the PL peak blueshift and the intensity increase. And we observed the PL peak redshifts and the intensity increases with the rising RF power of PECVD. We ascribed this effect to the smaller nanocrystal and higher density of nanocrystal.