利用电子脉冲电镀技术改善GaAs晶圆背侧深孔镀膜.doc

利用電子脈衝電鍍技術改善GaAs晶圓背側深孔鍍膜均勻度 黃振國、陳錫榮 建國科技大學 電機工程系暨研究所 中文摘要 　　目前高頻微波通訊常用的GaAs異質接面雙極電晶體(HBT)及假型通道高速電子移動電晶體(pHEMT)其晶片背面皆施加鍍金薄膜，做為接地及散熱之用。深孔鍍金為GaAs半導體較具競爭力的一種製程技術，其利用乾式蝕刻形成晶圓背面孔洞，因為陰極層必須有高密度及較好的均勻度，故先用成本高均勻度佳之濺鍍方式形成金種層，再使用低成本但均勻度較差之溼式電鍍沈積出厚膜，因此改善鍍膜均勻度將會是一項重要的課題。 　　本實驗利用電子脈衝時間來控制成膜速率，因深孔電鍍會造成孔內外之金溶液濃度不同，影響金沈積厚度不均勻導致薄膜電阻率飄升，因此必須精確的控制孔內外金溶液濃度、溫度、pH值、比重、流動速率及所使用的電流密度，以達到最佳化的電鍍條件：時間短、良率高、成本低。在調整最適化之測試參數，於晶圓有效電鍍面積1.65Dm2，孔洞深100μm寬50μm，深寬比為2：1，電子脈衝比1:10時，可獲得晶面：孔璧：底層之厚度比趨近 1：1：1設計值之4μm鍍金薄膜。 關鍵字：GaAs、電鍍、電子脈衝、均勻度 Uniformity Improvement of GaAs Wafer Backside Via Plating by Using Electron Pulse Plating Technique Jenn-Gwo Huang, Si-Rong Chen Department of Electric Engineering and Graduate School, Chienkuo Technology University Abstract The deep-hole plating is one of the competitive techniques in manufacturing GaAs HBT and pHEMT’s devices for grounding and heat dissipation. In common practice, holes are formed on the wafer backside, then a gold seed-layer is coated uniformly by sputtering followed by a low cost thick film deposited by electrical plating with the expense of poor uniformity. Therefore, how to improve the quality of the plating film becomes a critical issue in developing modern advanced devices. It is noted that the film uniformity of deep-hole plating will be influenced majorly by the concentration of the solution and current density inside and outside of the hole, causing the contact resistivity fluctuation. Therefore, the purpose of this work is to precise control the deposition rate by pulse time and current density, in other words, to control solution concentration, temperature, pH value, flow rate and current density for optimizing plating conditions to achieve high yield and low cost. Under controlled operation parameters, on effective plating area 1.65Dm2, via depth 100μm with width 50μm, aspect ratio 2:1, an ideal uniformity of 4μm thickness was obtained on wafer surface, via sidewall and bottom layer approaching 1:1:1 design contour. Keyword: GaAs, electro