以常壓式化學氣相沉積法成長氮化矽薄膜之特性研究

可發強烈白光的silicon-rich nitride (SRN)薄膜已由常壓式化學氣相沉積法製作而成。SRN薄膜利用 SiH2Cl2 (DCS)與NH3 氣體源來分別作為矽和氮原料成長於矽基板上。薄膜成長溫度維持在850℃，而氫氣則被用來當作乘載氣體並調節整個成長腔體維持在1大氣壓下。有關SRN薄膜的光特性則是利用光激螢光photoluminescence(PL)系統，量測不同的氣體源化學流量比[NH3]/ [DCS]: 從0.6至1.4，與量測改變薄膜成長時間從15分鐘至60分鐘的樣品而得到。從PL光譜結果指出，所有利用常壓式化學氣相沉積法直接成長出來的樣品，都具有不因量測溫度的改變而影響其高亮度螢光波段(1.5 – 3.5 eV)的特性。此外，SRN薄膜的螢光光譜，會隨NH3氣體源流量增加而藍位移，以及當SRN薄膜成長厚度大於600 nm時薄膜干涉(multiple interference effects)也會產生。SRN薄膜time-resolved (TRPL)量測結果亦指出光複合時間約為1 ns。更近一步，高解析度俯視穿隧式電子顯微鏡(TEM)也同時驗證矽量子點的存在，其大小分布從2 奈米到6奈米，而量子點密度則是每平方公分約有4e1012個量子點。依據上述理論，氮化矽薄膜的發光機制可視為是埋藏於薄膜中的矽量子點所產生的。此外，我們固定成長溫度、時間以及化學流量比分別為850aC、20 分鐘和R=1.2。高純度的氮氣以及氫氣則是作為乘載氣體並維持整個成長腔體壓力保持在1大氣壓。PL、FTIR以及X-ray photoelectron spectroscopy(XPS)等量測結果也表示出SRN薄膜的發光機制不單單只有矽量子點發光，還有表面狀態能階的發光。憑藉著矽量子點、表面狀態能階以及薄膜干涉，才能觀測到發高強度的白光氮化矽薄膜。

關鍵字

氮化矽；常壓式化學氣相沉積

並列摘要

Silicon-rich nitride (SRN) films that could present an intense white-light emission were fabricated by atmospheric pressure chemical vapor deposition. The SRN films were deposited on Si substrates using gaseous SiH2Cl2 (DCS) and NH3 as the source materials for Si and N, respectively. The deposition temperature was kept at 850aC and H2 was used as the carrier gas with its flow rate being modulated to maintain the chamber pressure at 1 atm during the deposition. The optical properties of films obtained by varying the flow ratio of source chemistry: R = from 0.6 to 1.4 and the deposition time from 15 to 60 min were examined by photoluminescence (PL) measurements. It was indicated that an intense luminescence band (1.5 – 3.5 eV) with temperature independent peak positions could be observed by the naked eye for all as-deposited samples. Besides, a blue-shift in PL spectrum was found with increasing NH3 flow rate and multiple interference effects became evident when the film thickness was over 600 nm. Also, time-resolved PL exhibited a short radiative lifetime around 1 ns for the SRN films. Moreover, high resolution plan-view transmission electron microscopy (plan view HRTEM) demonstrated the existence of Si dots in the SRN films with the dot sizes ranging from 2 to 6 nm and the dot density of about 4e1012/cm2. Based on the results obtained, related luminescent mechanisms for the SRN films were considered to be connected to the Si dots produced therein. Furthermore, the growth temperature, deposited time and the chemical flow rate were all maintained at 850aC, 20 min and R=1.2, respectively. High purity N2 and H2 were used for different carrier gases to keep the chamber pressure held at 1 atm. PL measurements, Fourier-transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) also displayed unique results which indicated the luminescent mechanisms were not only caused by Si dots but also surface states. According to Si dots, surface states, and multiple interference effects, high intensity whitely luminescent from silicon nitride films were observed.