以純氧化矽沸石奈米顆粒製備低介電膜及抗腐蝕膜之研究

Abstract

本研究利用水熱程序，以四丙基氫氧化銨(TPAOH)作為結構導向試劑，製備含MFI結構的純氧化矽沸石(PSZ)與MFI-like非結晶型氧化矽(NCS)奈米顆粒，並將此奈米顆粒應用於低介電膜及抗腐蝕膜的製備。 研究中討論不同厚度的水熱反應器，對於水熱程序合成奈米顆粒的影響。研究發現，水熱反應的初期升溫速率，對於合成奈米顆粒是重要的。經由熱傳模擬分析，得知當反應器的器壁厚度下降，於水熱反應初期，反應器內部的溫度上升速率較快，因此使水熱程序合成出較大粒徑的顆粒。 關於低介電膜的研究，薄膜是利用純氧化矽沸石奈米顆粒與界面活性劑組成的鍍膜溶液所製備。鍍膜液的製備，至少被三個因素(四丙基氫氧化銨濃度、水熱反應時間、與界面活性劑尾基長度)所影響。研究中利用不同濃度之四丙基氫氧化銨或不同水熱反應時間，製備奈米顆粒；以及使用不同疏水尾基鏈長度的聚山梨醇酯(Polysorbate)界面活性劑。由於純氧化矽沸石奈米顆粒表面的氫氧基數量(或表面親水性)，隨著四丙基氫氧化銨濃度的上升或水熱時間的下降而上升，且界面活性劑的親水性隨著尾基長度上升而下降；若使用不同親水性的奈米顆粒與界面活性劑形成的鍍膜液製備薄膜，薄膜將具備不同的性質(例如:介電常數、漏電流密度、孔隙度、表面型態、硬度、彈性模數)。使用親水性低的奈米顆粒或界面活性劑製備薄膜，可提升薄膜的孔隙度。此外，親水性低的奈米顆粒表面含較少的氫氧基，有利於製備介電常數低的薄膜。然而，當奈米顆粒表面的親水性太低，使界面活性劑形成大的聚集物，進而造成煅燒後的鍍膜表面有大孔洞。薄膜表面的大洞，使薄膜有較高的漏電流密度與較高的介電常數。薄膜的機械強度(硬度與彈性模數)，隨著奈米顆粒的表面氫氧基減少而下降。此外，機械強度較低的薄膜，其表面出現奈米尺度的裂縫。另一方面，親水性較高的界面活性劑對於奈米顆粒有較強的作用力，使製備後的薄膜於六甲二矽氮烷(HMDS)表面修飾步驟後殘留較少的氫氧基團，進而降低薄膜介電常數、降低薄膜漏電流密度、與提高薄膜崩潰電場。 MFI-like非結晶型氧化矽(NCS)奈米顆粒可經由短時間水熱程序製備而得。由於非結晶型氧化矽顆粒的粒徑約5奈米，本研究嘗試利用此奈米顆粒於鋁基材上製備緻密的氧化矽薄膜，應用於金屬防蝕塗佈。然而，隨著製備的薄膜厚度增加，薄膜表面產生裂縫；產生裂縫主要是因為氧化矽顆粒與鋁金屬間的熱膨脹係數差異所造成。為了製備較厚且表面沒有裂縫的抗腐蝕薄膜，利用有機矽烷化物與非結晶型氧化矽奈米顆粒製備有機-無機混成薄膜。由研究結果發現，添加此奈米顆粒，可提升薄膜的抗腐蝕能力。塗佈後的有機-無機混成薄膜，膜厚約4 μm且具備高的抗腐蝕性；且此薄膜具備3H的鉛筆硬度(此表面硬度與市售塗佈商品-南美特R 5200-具備相同的機械強度)。

Pure-silica-zeolite (PSZ) Mobil-Five (MFI) and MFI-like noncrystalline silica (NCS) nanoparticles synthesized using tetrapropylammonium hydroxide (TPAOH) as a structure directing agent were produced via hydrothermal processes, and those nanoparticles were applied to fabricate porous silica low dielectric constant (low-k) films and anti-corrosion films in this dissertation. When hydrothermally producing the PSZ MFI nanoparticle suspensions, effect of wall thickness of autoclave reactor is studied. Heat transfer simulation indicates that decreasing the wall thickness increases temperature rising rate in the reactor at initial stage of hydrothermal synthesis. An increased initial temperature rising rate produces the suspensions with large particle size. That is, initial temperature rising rate in the reactor affects significantly on sizes of the PSZ MFI nanoparticles at the final stage of hydrothermal synthesis. Porous silica low-k films are prepared from coating solutions containing the nanoparticles and surfactants. Effects of TPAOH concentration, hydrophobic tail length of polysorbate surfactants, and hydrothermal time on coating solutions to produce low-k films are studied. Because increasing the TPAOH concentration or decreasing the hydrothermal time increases the number of silanol groups (or hydrophilic property) on the particles and because increasing the tail length decreases hydrophilic property of the surfactants, coated films from coating solutions containing these particles and surfactants with various hydrophilic properties are substantially different. Thus, their effects on low-k film properties (i.e., k value, leakage current density, porosity, surface morphology, hardness, and elastic modulus) are investigated. Using nanoparticles or surfactants with a low hydrophilic property produces films with high porosity. Additionally, particles with few silanol groups are preferable to prepare films with ultra-low-k values. However, when the hydrophilic property of particles is too low, large micelle aggregates that form in coating solutions result in large holes on film surfaces after the calcination. These large holes can cause extremely high leakage current densities and high k values >2. Further, mechanical strength of films decreases as the number of silanol groups on particles decreases. Additionally, surfaces of the resulting films with poor mechanical strength have some nano-sized cracks. Conversely, increasing hydrophilicity of surfactants increases their interaction with silica particles, resulting in a decreased number of remaining silanol groups in films after hexamethyldisilazane (HMDS) surface treatment. The small number of remaining of silanol groups can cause films to have low k values, low leakage current densities, and high breakdown fields. When using a short hydrothermal time to synthesize the nanoparticle suspensions, only MFI-like NCS nanoparticle suspensions are produced. The MFI-like NCS particles with small size of about 5 nm are attempted to prepare dense silica coatings for protection of aluminum from corrosion. However, as coating thickness increases, the number and size of cracks increase. Cracks on films are a result of thermal expansion mismatch between silica particles and aluminum substrate. To produce thick and crack-free films as anti-corrosion coatings, MFI-like NCS suspensions were mixed with an organosilane solution to develop hybrid coating solutions. Anti-corrosion ability increases as the suspension loading increases. Hybrid films with smooth surface and thickness of about 4 μm have good anti-corrosion ability. Additionally, the films have pencil hardness of 3H, which is comparable with that of a commercial product of NanoMateR 5200.