以電漿增強化學氣相沈積摻氟二氧化矽薄膜之研究

Abstract

本論文可分為兩部分，第一部份是研究未摻雜質二氧化矽薄膜，另外一部份是研究摻氟二氧化矽薄膜。我們利用SAMCO公司型號PD-240的PECVD成長薄膜，並且找出最佳的條件。 首先利用PECVD通入TEOS及O2氣體成長未摻雜質二氧化矽薄膜，藉由控制氧氣流量、RF功率、壓力、成長溫度、TEOS流量等條件來成長薄膜，我們發現當TEOS流量為7sccm時可以得到最佳均勻度，而且增加RF功率、壓力、及溫度我們可以得到較佳品質的二氧化矽薄膜，同時為了進一步改善二氧化矽薄膜的品質，我們利用高溫爐管及快速高溫退火來使沈積的二氧化矽薄膜更為致密。 我們使用PECVD通入TEOS、氧氣、CF4等氣體，沈積摻氟二氧化矽薄膜，我們將CF4氣體由0sccm增加到40sccm，其介電係數由4.08降到3.37，而且我們也試著再利用高溫爐管850℃30分鐘及RTA 1000℃30秒進行退火，由於受熱氟由薄膜脫附，使的介電係數上升。 在摻氟二氧化矽中當氟含量很高時，薄膜變的不穩定且很容易吸水，這是由於氟含量很高時，產生Si-F2鍵結使薄膜較為鬆散所致，因此高含氟濃度的薄膜易於吸附水氣使介電係數上升，為了改善此一現象我們利用N2電漿的後續處理，來穩定含氟的二氧化矽薄膜，只要處理的時間在20分鐘以上，都可有效阻擋水氣的吸附，使薄膜較為穩定。

We can divide the thesis into two parts. One part of the thesis studies the un-doped oxide. Another studies the F-doped oxide. We grew the thin films by the PD-240 PECVD from SAMCO International Inc and found the optimum conditions of the oxide films. First, we deposit the un-doped oxide films by PECVD process using TEOS/O2 gases. There are five controlled conditions, which are O2 flow rate, RF power, pressure, temperature, and TEOS flow rate, to deposited the un-doped oxide films. We found that optimum TEOS flow rate was 7sccm for the PD-240 PECVD. Also, with increasing RF power, pressure, and temperature, we can get better quality of the un-doped oxide films. In order to improve the quality of the un-doped oxide films, the as-deposited oxide films were annealed by furnace or RTA process. FSG films were deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) process using TEOS/O2/CF4 gases. The dielectric constants of the as-deposited films decreased from 4.08 to 3.37 with the increase CF4 flow rate from 0sccm to 40sccm. We also tried to use furnace annealing at 8500C for 30 mins and Rapid Thermal Anneal (RTA) at 10000C for 30sec after the as-deposited FSG films. The relative dielectric constant of as-deposited films with thermal annealing was higher than the SiOF films without thermal annealing. The result of higher dielectric constant was induced by fluorine desorption from the SiOF films. At the high F concentration of the SiOF films, the SiOF films become more unstable to moisture absorption. The moisture absorption of SiOF with high fluorine concentration are caused by the porosity and the formation of Si-F2 in the films. The absorbed water causes increase of dielectric constant and reliability problems in ULSIs. In order to improve the moisture resistance of the SiOF films, we would use N2 plasma annealing as the post treatment to stabilize the films. With increasing the plasma post treatment time above 20min, it is effective to stabilize the SiOF films.