奈米鈀觸媒於矽烷改質之矽晶片上無電鍍鎳沉積之研究

Application of Nano Palladium Catalyst for Electroless Nickel Deposition on Silane-compound Modified Silicon Wafer

潘贈傑(Tseng-Chieh Pan)

指導教授 ： 衛子健

國立清華大學/工學院/化學工程學系/碩士(2014年)

摘要

矽太陽能電池已問世五十餘年，對效率的追求、製程的改善仍是不斷的改進。其中在正面金屬化製程中，發展無電鍍鎳/電鍍銅之正面導線結構取代傳統網印銀線為其中一重要目標。前人的研究顯示，無電鍍鎳與矽晶表面間附著力不佳是個關鍵。因此本論文致力於無電鍍鎳沉積層與矽晶表面間之附著力的改善，方法為在矽晶表面以矽烷表面改質作，並搭配上自行開發的奈米鈀觸媒(Polyvinylpyrrilidone Capped Palladium, PVP-Pd)，並藉由矽烷分子與矽晶表面以及奈米鈀觸媒間的交互作用，增加後續鍍層之附著力。
實驗的首部分是在矽烷表面改質之結果分析，先利用接觸角量測來判定表面改質的效果，再以螢光染色來觀察表面塗佈情形並以原子力顯微鏡觀察表面型態在表面改質前後的變化。最後以傅立葉紅外光譜儀觀察超音波震盪前後矽烷表面改質層官能基的吸收波值變化，並再以原子力顯微鏡觀察超音破震盪步驟前後表面粗糙度之變化。
實驗的第二部分為無電鍍鎳沉積層與矽晶表面之附著力以及接觸電阻之討論。進行其測試之試片皆為無電鍍鎳沉積1分鐘(厚度約0.2 μm)，在所有實驗條件中附著力表現最佳的條件為未經熱退火之矽烷表面改質搭配濃度100ppm之PVP-Pd觸媒之試片，其附著力平均值為11 MPa，且與使用商用觸媒之試片(2.57 MPa)相比有明顯提升。在進一步的探討中，針對矽烷分子與PVP-Pd觸媒之間的交互作用機制作探討，藉由X射線光電子能譜儀證明兩者間經由電子交換產生交互作用情形。另一方面，以傳輸線模型量測得無電鍍鎳層與矽晶表面之特徵電阻後，可計算出特徵接觸電阻值，在所有量測試片中以未經熱退火之矽烷表面改質搭配濃度50ppm之PVP-Pd觸媒之試片，特徵接觸電阻值最低，其值為0.0532 ohm．cm2，是僅使用商用錫鈀膠體之試片的1/3倍。

關鍵字

奈米鈀觸媒 ； 矽烷 ； 表面改質 ； 無電鍍鎳 ； 附著力

並列摘要

Although silicon solar cell is discovered more than 50 years, the chase on raising high efficiency as well as improving fabrication technology continuous. During the process of front metallization, electroless plating of nickel/copper bi-layer an alternative for conventional srcreen-printing silver past is one of important technical goal. However, it is revealed that the physical adhesion between electroless plating nickel layer (ELS/Ni) and silicon (Si) wafer is too weak to provide adequate contact. Therefore in this study, we aim to improve the physical adhesion as well as electrical contact of ELS/Ni on Si wafer. In particular, we attempt to modify Si wafer surface with silane compound and then utilize a novel, self-developed nano-palladium particle catalyst (Polyvinylpyrrilidone Capped Palladium, PVP-Pd); the PVP-Pd is found to have molecular-level interaction with the functional groups on the silane compound and consequently provide better macroscopic adhesion.
In the first part, we focus on the effect of silane compound modification which is examined by contact angle measurements, fluorescent labelling, as well as atomic force microscope (AFM). In addition, the fourier-transform infrared spectrometer (FTIR) is applied to explain the effect of post-sonication on silane-modified Si surface.
The second part of this study is to examine the adhesion and contact resistance between ELS/Ni layer and Si wafer. All of the sample prepared by ELS/Ni (shows comparable film thickenss of ~ 0.2μm for a depositon time of 1 minute). As to the adhesion test, the result shows that the best adhesion value of 11 MPa is found in the sample using 100ppm PVP-Pd on silane-modified silicon surface without the need of post rapid thermal annealing (RTA), which is much higher than the sample made of commercial Sn/Pd catalyst (2.57 MPa). To explain this improvement, X-ray photoelectron spectroscopy (XPS) is applied results to understand the interaction between sialne compound and PVP-Pd particle. Meanwhile, we also try to measure the specific contact resistance between the ELS/Ni and Si wafer. According to the transmission line model (TLM) method and proper pattern on the sample, an acceptable value of 0.0532 ohm．cm2 is measured in the sample using 50ppm PVP-Pd on silane-modified Si surface without RTA, which is one third of the sample using commercial catalyst.

並列關鍵字

PVP-Pd ； silane ； surface modification ； electroless Ni plating ； adhesion

參考文獻

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