電漿化學氣相沉積法成長氮氧化矽在III-V化合物半導體之性質研究

Abstract

在三五族化合物半導體技術中, 利用電漿化學汽相沉積法所長氮化矽已被 廣泛地應用, 但是此膜質對熱抵抗力較弱, 且在沉積界處仍具頗高的機械 應力. 由於電漿化學氣相沉法所成長氮氧化矽比同種成長方式的氮化矽, 含氫量較低因而有較高熱抵抗能力且在界面處的應力也較小, 所以近來氮 化矽常被氮氧化矽所取代. 例如 金屬-絕緣體-半導體 場效電晶體 (MIS- FET)閘極絕體以及光電元件保護層, 而由一氧化氮-氮-矽烷/氦之電漿混 合所製成的氮氧化矽, 其結構和電性特質則將被探討.本文討論在三五族 半導體基板的沉積參數效應, 固定 矽烷/氦流量 (100 sccm)及一氧化氮 和氮流量的總合(400 sccm), 改變 氣體流量 (N2O=0~400 sccm), 反應器 內氣壓(266~1000 mtorr), 射頻功率(50~130瓦特), 以及基板溫度(150 ~350 C).在這條件之下, 我們可得到1.469至1.907的折射率以 及264.67-399埃/min)的沉積率, 而電阻率和漏電流在0.2百萬電子伏特/ 公分下分別大於10E13歐姆-公分和小於五十微微安培, 崩潰強度在3-9百 萬伏特/公分之間, 以及介質長數在4-6之間也被量測到, 這些膜質皆足以 符合元件的絕緣保護. Silicon nitride obtained by plasma enhanced chemical vapor deposition (PECVD) is now widely used in III-V semiconductor device technology. However the plasma silicon nitride layer normally has a quite high mechanical stress and poor relative heat treatment. So, silicon oxynitride film prepared by PECVD have recently gained interest as well as interlayer dielectric because of their lower hydrogen content and lower mechanical stress as compared to silicon nitride. This material has been found to be a promising gate insulator for MIS-FET transistors on compound semiconductors and electrical properties for PECVD amorphous silicon oxynitride films prepared from N2O-N2-SiH4/He mixtures have been investigated. The effects of deposition parameters, i.e. SiH4 is fixed on 100 sccm, N2O flow rate (N2O 0~400 sccm and N2O+N2 are 400 sccm ), chamber pressure (266~1000 mtorr), R.F. power (50~130 W) and substrate temperature (150 ~350 C) which were systematically varied on various film properties deposited on III-V semiconductor substrate (GaInP/GaAs/GaAs-substrate) are discussed. The characteristics of the films such as composition, refractive index, deposition rate, and hydrogenous bond content qualitative analysis were investigated by AES, ellipsometry, and FTIR spectrometry. Under these conditions films have been made with a refractive index of 1.469~1.907 and a deposition rate of 264.67~339 A/min. Electrical resistivity greater than 10E13 ohm-cm at 0.2 MV/cm, leakage current lower than 50 pA at 0.2 MV/cm, breakdown strength of 3~9 MV/cm, and a dielectric constant of 4~6 were observed. These films can afford to passivate the devices.