Effects of Preparation Processes on Low-k Porous Silica Thin Films
Date Issued
2007
Date
2007
Author(s)
Yu, Chun-Wei
DOI
zh-TW
Abstract
Mesoporous silica has been widely used for low-k materials because of it’s low dielectric constant, good thermal stability, and easily-preparation procedures. However, the porosity within the film makes the mechanical strength bad. To solve the problem and reach the industrial standard, we made use of some methods as follows which can make the process improved.
First, we tried to change the procedures of surface modification (under reflux process), the end set point of calcination temperature and add soaking step in order to lower the opportunity of absorbing water and safety concern. The reflux temperature was 70℃ under acid conditions and adding TPAOH to synthesize the colloidal solution with SiO2 solid particle in it. Then we added tween80 and spanned on P-Si wafer. After baking, calcination and surface modification, we got the low-k films and analyzed by CV、SEM、nanoindentor. Second, we made a series of tests and decided how to synthesize the colloidal solution with zeolite particle in it by hydrothermal process under base conditions. Then we also added tween80, got the low-k films and analyzed by CV、IV、nanoindentor、SEM、XRD、N2 adsorption/desorption system.
From the results of first part, soaking step didn’t affect the electric properties of the films. The k value became lower and the mechanical strength became stronger while the end set point of calcination temperature became higher. But the mechanical strength still couldn’t be up to the industrial standard. From the second part, we found that aging time, hydrothermal temperature and time would directly affect the dielectric properties of the films. When the aging time became longer, the films had better structures. The electric properties would be measured more easily. In addition, raising the hydrothermal temperature or prolonging the time would make the particles more crystalline. Adding a little tween80 could lower the k value to 2.30. On the contrary, lowering the hydrothermal temperature or shorting the time would make the particles less crystalline. Adding more tween80 could lower the k value to 2.16. Of all the mechanical strength and the leakage current could meet the industrial standard.
The best films our lab can prepared had k value=2.16, leakage current=8.37*10-8 A/cm2, elastic modulus=18.0GPa, hardness=2.0GPa.
Subjects
低介電常數
薄膜
孔洞材料
回流程序
水熱程序
沸石顆粒結構
low dielectric constant
thin film
porous material
reflux process
hydrothermal process
zeolite particle structure
Type
thesis
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