- 學位論文
應用氨基矽烷化合物改質於矽晶圓上高附著性金屬化及擴散阻障層之研究
The Application of Amino-silane Compound Modification on Silicon Wafer for Adhesive Metallization and Diffusion Barrier
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摘要
在半導體和IC封裝上利用無電鍍的技術來沉積金屬層已廣泛被應用，通常在無電鍍的反應過程中都需要利用觸媒(如鈀觸媒)來降低活化能以利無電鍍的發生，而這些觸媒的附著關聯到金屬層與矽基板間的附著力，因此為了有效提升觸媒在矽基板上的附著，有研究學者利用氨基矽烷化合物作為矽基板的表面改質劑以增加觸媒的附著並同時提升金屬層的黏著性，然而在一些文獻中可知要讓氨基矽烷化合物於矽基板表面達到單層吸附狀態(Self-Assembled Monolayer)是一件非常困難的事情，因此在本研究的主題中主要是探討氨基矽烷化合物的改質優化並應用於矽晶圓上達到高附著力金屬層與矽基板間的黏著，另外在實驗過程中也發現氨基矽烷化合物的改質搭配高分子奈米鈀(Polyvinyl alcohol-capped palladium, PVA-Pd)的修復可作為銅擴散阻障層的使用，達到阻障銅層擴散進入矽基板中而造成元件的損壞或是可靠性下降，因此在研究方向與成果上分為兩大部分進行探討。 第一部分的研究是探討3-[2-(2-Aminoethylamine)ethyl-amino]propyltrimethoxysilane (ETAS)氨基矽烷化合物溶解在四種不同極性溶劑內(分別為甲苯(TOL, 非極性溶劑)、乙醇(ETL, 極性質子溶劑)、丙酮(ACT, 極性非質子溶劑)以及異丙醇(IPA, 極性質子溶劑))於相同改質時間下(30分鐘)在矽基板表面所呈現出的特性與改質效果，此外對於後續PVA-Pd的吸附量以及金屬層附著力的影響進行比較。首先在粒徑分析結果中可發現ETAS在眾多文獻常用的甲苯溶劑下所呈現出的粒徑較其它三者溶劑大，且改質於矽基板表面後形貌也有明顯的團聚存在，因此對於眾多文獻提到甲苯溶劑可形成單層吸附狀態是具有疑慮的，而在丙酮溶劑中，由於ETAS上的氨基官能團會與酮結構發生不可逆反應並生成席夫鹼，因此丙酮溶劑不適用為氨基矽烷化合物的溶解溶劑，最後在乙醇和異丙醇兩種極性質子溶劑內，雖然粒徑分析上呈現相似的結果，但由於醇類溶劑對氨基官能團會產生醇化反應而導致氨基官能團質子化，而在這兩種溶劑中又以一級醇的乙醇溶劑較二級醇的異丙醇嚴重，所以在乙醇溶劑下進行改質對表面形貌及結構都有影響，另外利用異丙醇作為ETAS溶劑進行改質後在後續PVA-Pd的吸附量上及金屬層附著力測試結果中皆呈現出比其它溶劑更優異的表現，因此綜合上述的結果可知異丙醇是較適合ETAS的溶解溶劑選擇。 在第二部分的研究則是沿用第一部分中的異丙醇溶劑並於不同改質時間下搭配不同重量比例的PVA-Pd應用於銅擴散阻障層上，並探討其阻障效益及後續銅層附著力的影響。從片電阻電性分析、XPS結構分析及TEM介面分析的實驗的結果得知，當ETAS改質不完整時(稱為島狀吸附狀態)搭配2倍重量比例的PVA-Pd能夠額外提供銅擴散阻障的效果，而當ETAS改質完整時(稱為單層吸附)，僅需搭配0.5倍重量比例的PVA-Pd就能達到阻障效果。在附著力的檢測上可發現未經熱退火前，附著力的表現都並不理想，然而經過熱退火處理後在ETAS為島狀吸附或是單層吸附下搭配1倍重量比例的PVA-Pd後皆能表現出優異的銅層與矽基板間的附著力，最終在裂面分析結果中得知，附著力的提升來自於ETAS與PVA經熱退火處理後形成O-N-O的鍵結而讓銅層與矽基板間的附著力提升，綜合上述結果可知高重量比例的PVA-Pd能修補ETAS的缺陷並用於提升銅擴散阻障的效果，而在附著力的表現上可發現過多的PVA含量並非能幫助到附著力的提升，反倒適當比例的PVA-Pd才能有效在熱退火處理後得到較佳的附著力特性。
並列摘要
In semiconductor manufacturer and IC package, electroless plating (ELP) of metal film is a special promising skill. In general, the determinant of ELP is a catalytic reaction that needs a trace amount of noble metal such as palladium as the activator to lower the activation energy of metal formation. Because the adhesion of ELP metal film relates to the interfacial characteristic of catalyst and silicon surface. In order to enhance the bridging between the silicon substrate and palladium (Pd) catalyst, modifying silicon surface with organo-silane compound such as 3-[2-(2-aminoethylamino)ethylamino] propyl-trimethoxysilane (ETAS) is commonly used. The ETAS treatment then forms a self-assembled monolayer (SAM) which is capable to interact with polymer-capped Pd catalyst and thereby promotes the adsorption of ELP metal film. However, it is known that the SAM formation is very sensitive to process condition such as soaking time and solvent agents. Therefore, in the first study, the amino-terminated silane compound modification was wet-processed on silicon wafer using four different solvents to investigate the property of forming SAM and its influence on the adhesion of eletroless deposited nickel-phosphorus film. Analyzed by various tools including the dynamic light scattering (DLS), the atomic force microscope (AFM), the X-ray photoelectron spectroscopy (XPS), the inductively coupled plasma with mass spectroscopy (ICP-MS), a proper link between the processing solvent and SAM quality is established. It is found at least the chemical compatibility, the polarity and the acidity of solvents can affect the final morphology of the resultant SAM. Unlike toluene and ethanol that are most-frequently chosen in literatures, we conclude the isopropyl alcohol (IPA) is a superior solvent for amino-terminated silane compound. Owing to the good SAM quality formed in IPA, the adhesion of eletroless deposited nickel-phosphorus film is largely strengthened, even as high as the bulk strength of silicon wafer. Although previous studies have confirmed that organosilane-based compounds can be effective inhibited Cu ion diffusion and improved the adhesion strength, forming SAM is extremely process-sensitive such as stock solvent or during surface silanization, which adds complexity and difficulty to form an ideal SAM on inch-sized area and thus impairs their practical use. In this study, we proposed a major breakthrough of utilizing amino-silane compound of ETAS as the advanced copper diffusion barrier. By designing a self-healing mechanism using polymer-capped palladium nanoparticles right after surface silanization, the inherent flaw of large-area SAM formation largely reduced. From our results, we discovered the defect of ETAS via polymer-capped palladium nanoparticles healing, which provided the additional copper suppression properties. In addition, along with the PVA weight ratio of polymer-capped palladium nanoparticles increased, the diffusion of Cu significantly reduced. Detailed comparison for polymer-capped palladium nanoparticles self-healing effect was studied through surface morphological characterization, chemical bonding characterization, sheet resistance test, and adhesion property characterization.
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