探討不同型態二氧化矽粒子及大小對孔洞型低介電薄膜的影響

Studying the Effects of Different Types and Different Particles Sizes On Porous Silica Low-K Thin Films

柳佑樵(Yu-Chiao Liu)

指導教授 ： 萬本儒

國立臺灣大學/工學院/化學工程學研究所/碩士(2006年)

https://doi.org/10.6342/NTU.2006.01228

摘要

中孔二氧化矽做為低介電薄膜材料，有介電常數低於2、熱穩定性佳、製程簡單的優點。不過也因具備孔洞的特性，造成薄膜有機械強度不佳的缺點。為了達到半導體工業應用的標準，本研究探討膠體溶液中二氧化矽顆粒大小對中孔二氧化矽低介電薄膜(電性及機械強度)的影響。
本研究應用兩種方式製備含二氧化矽顆粒膠體溶液。第一種是以70℃回流攪拌方式，在酸性條件下合成實心二氧化矽顆粒膠體溶液。第二種是以95℃水熱法方式，在鹼性條件下合成含小孔洞二氧化矽沸石顆粒膠體溶液。研究中是以HRSEM觀察粒徑大小。合成出之二氧化矽膠體溶液再添加界面活性劑，以旋轉鍍膜方式鍍於矽晶片，然後應用介電常數、漏電流、機械強度、XRD圖分析薄膜性質。
研究結果顯示，第一種以回流方式合成二氧化矽顆粒，回流90分鐘後開始出現約4.5nm小顆粒，隨回流時間越長顆粒越大。隨後鍍出之薄膜則發現機械強度隨時間越長而提升，硬度由0.8GPa提升至1.2GPa，但介電常數則有上升趨勢，由2左右上升至2.4，各薄膜漏電流則均約為10-8(A/cm2)。第二種以水熱法方式合成二氧化矽沸石顆粒，使用兩種鹼(TPAOH、TBAOH)作為合成沸石顆粒的模板。TPAOH結果中，顆粒隨時間越長變大，由10nm成長為30nm。在薄膜表面有缺陷，造成介電常數量測不易；TBAOH的結果中，顆粒隨時間則沒有明顯改變，薄膜表面則沒有出現缺陷。當沸石合成時間由6小時至18小時，介電常數與漏電流均下降；時間由18小時至48小時，介電常數與漏電流都變大，這是18小時的沸石膠體溶液內有較多SiOH能與Tween 80間作用力較好，薄膜經過熱處理後SiOH縮合成穩定結構Si-O-Si結構，能夠支撐孔洞，表面修飾之後，孔洞表面的親水基可被置換為疏水基，所以介電常數與漏電流均會下降。

關鍵字

低介電常數 ； 薄膜 ； 界面活性劑 ； 水熱反應 ； 粒徑大小

並列摘要

Mesoporous silica has been widely studied for low-k materials, because of it’s low dielectric constant (about 2), good thermal stability, and friendly-preparation procedures. However, the porosity in the film makes the mechanical strength insufficient. The improvement of mechanical strength of the films is essential. This research intends to solve the problem by making the films with small silica particles. The correlations among the particles size, the dielectric constant and mechanical strength of the films were systematically studied.
Two different kinds of procedure to produce SiO2 particle colloids were used. The first one was the reflux procedure at 70℃ under acidic condition. The second one was the hydrothermal procedure at 95℃ under basic condition, and TPAOH or TBAOH was used as the template. The particle sizes were measured by HRSEM. The coating solution was a mixture of SiO2 colloids and Tween 80 at 30℃. The resulting solution was spin-on a 4-inch silicon wafer. Dielectric constant, leakage current density, mechanical strength and XRD results were applied to analyze the characteristics of the thin films.
By using reflux procedure, the particle sizes were about 4.5nm after refluxing for 90 minutes. The particle sizes increased with the reflux time. The larger the particle sizes were, the better the mechanical strength of the films was However, the dielectric constant was slightly increased with the increase of the particle size. The leakage current densities of all the films were about 10-8 (A/cm2). By using hydrothermal procedure and TPAOH as the template, the particle size was found to increase from 10 nm to 30nm within 6 ~ 48 h hydrothermal treatment. There were defects on the surface of those films. Therefore, it was hard to measure the dielectric constant precisely. Only one data of the dielectric constant could be measured and the value was 2.9. The mechanical strength decreased with the increase of hydrothermal period. When TBAOH was used as the template, no particle was observed in the solution. The hardness of all the films was higher than 1GPa. However, all the films also have higher values of dielectric constant, then the leakage current densities of the films from the hydrothermal procedure were all about 10-6(A/cm2)~10-7(A/cm2).

並列關鍵字

low dielectric constant ； thin film ； surfactant-templating ； hydrothermal ； particle size

參考文獻

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