鹼式單階段水熱製程製備結晶孔洞型二氧化矽低介電薄膜

Preparing Crystalline Porous Silica Low-k Thin Films by One Stage Hydrothermal Process in Base Environment

龔建豪(Chien-Hao Kung)

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(2009年)

https://doi.org/10.6342/NTU.2009.02185

摘要

低介電常數材料在現今半導體工業中扮演相當重要的角色，其中在鹼性環境下以多階段水熱法製備之孔洞結晶型二氧化矽薄膜具有介電常數低、機械強度佳以及製程整合簡單的優點，相當具有發展潛力。但由於目前相關的程序仍相當冗長，因此本研究將改以單階段水熱法，研究水熱反應時間、離心程序等因素對於孔洞結晶型二氧化矽薄膜的影響。
　　由研究結果發現，單階段的水熱反應所產生的奈米粒子其均勻性較差且粒徑較大，因此本研究導入離心程序來篩選適合鍍膜的奈米粒子。但結果顯示，離心程序在篩選奈米粒子的同時，也會改變粒子的濃度、結晶性及溶液的黏度，進而對薄膜性質造成影響。本研究的其他發現簡述如下，第一是水熱反應時間越久，薄膜總孔洞體積越大且顆粒彼此間堆疊的大孔隙越多，除了會造成較大的漏電流外，也可能因金屬的滲透而影響介電常數之量測；第二是結晶性越高，顆粒表面的氫氧基越少，因此薄膜機械強度越差；第三是較厚的薄膜可能會有表面修飾不完全的問題，因此介電常數無法降低；第四是離心後取上層液塗佈所得到的薄膜其介電常數較低、機械強度越高且漏電流較小，而中層比上層之各項性質差，但仍比未離心者佳。
　　在製程中同時使用界面活性劑與離心程序除了可以藉由增加總洞體積而達到降低介電常數值的效果外，也可以有效地避免大孔隙的產生並增加塗佈之均勻性。
　　本研究中的最佳結果在水熱反應時間36~42小時，離心後取上層液塗佈，所得之薄膜具介電常數1.78~1.88，Hardness 1.33~1.46 Gpa，Elastic module 11.10~12.72 Gpa，漏電流密度1.37e-8~4.97e-8 A/cm2。該薄膜的各項性質皆符合未來IC工業所需之標準。

關鍵字

低介電常數 ； 界面活性劑 ； 沸石 ； 孔洞材料 ； 離心程序 ； 鹼式法

並列摘要

Low dielectric constant (low-k) material is important in semiconductor industry. Crystalline porous silica which is prepared by two stages hydrothermal process in base environment possesses advantages of low dielectric constant, good mechanical strength, and easily-preparation procedures. However traditional synthesis process is very tedious, and some procedures are not necessary actually. In the present study, an one stage hydrothermal method is used, and the effects of hydrothermal process and centrifugation on the properties of crystalline porous low-k silica thin film were examined.
It was found that the size, concentration, and crystallinity of the particles are proportional to hydrothermal period. Also the particle size is less uniform than what is prepared by two stage process. After the reaction, the solution containing particles was centrifuged, and it showed that centrifugation process would influence the crystalline, concentration of particle and viscosity of solution. However, the followings were observed: First, longer hydrothermal time would result in higher porosity in thin film and more large voids from particles piled up each other which would result in serious leakage current and influence the measurement of k value. Second, the better crystalline of particles in the colloid would cause the mechanical strength poor, since pooler hydroxide groups on particle surface. Third, thicker thickness of film might result in the process of surface modification incomplete, and the dielectric constant couldn’t be decreased. Finally, the film derived from the solution taken from the upper side of centrifugation tube after centrifuged was used for the spin-coating on silicon wafer. The film possesses lower k value and leakage current density and higher mechanical strength than the film spun by the solution un-centrifuged.
The processes applying surfactant and centrifugation both could not only decrease k value by increasing the total pore volume in the film, but also decrease quantity of large voids, and facilitate the coating situation on the surface.
The best thin films prepared in this research possess the k value of 1.78~1.88, hardness of 1.33~1.46Pa, elastic modulus of 11.10~12.72Gpa, and leakage current of 1.37e-8~4.97e-8 A/cm2. The films were derived by taking the upper side solution of centrifugation tube after centrifuged, and the solution were synthesized under the hydrothermal conditions, temperature 100℃ for 36~42 hours.

並列關鍵字

low dielectric constant ； thin film ； surfactant ； zeolite ； porous material ； crystalline ； centrifugation ； base environment ； one stage hydrothermal method

參考文獻

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