应用于三维集成的金铟键合技术研究

Research on the Au-In Bonding Technology for 3D Integration

由于埋置芯片耐受温度的限制,圆片级低温键合技术是MEMS三维集成的关键工艺之一。金属In凭借自身熔点低而金属间化合物(Intermetallic compound, IMC)熔点高且性质稳定的特点,使得Au-In固液扩散键合法成为颇具前景的低温键合技术之一。本文采用Au-In二元共晶化合物进行圆片级低温键合,在键合衬底上先后制备了0.4μm的SiO/SiN介质层、3.5μm的Au层和1.7μm的In层,然后分别研究了先预加热键合极板再贴合圆片和先贴合再加热两种键合方式。电性能测试、An/In组分分析和剪切试验结果表明:先贴合再加热的键合样品芯片形成了性质稳定的IMC组分,具有良好的电学互连特性稳定性,且剪切强度达到100 MPa。一定样本容量的实验结果证明隔绝键合前Au-In的相互扩散能够有效增强键合的可靠性。

Low temperature wafer bonding with chips is a critical process for 3D multi-chip inte-gration due to its compatibility with the temperature tolerance of embedded chips.Low melting point metal indium can be manipulated into high melting point Au-In intermetallic compounds(IMC)with appropriate Au/In concentration and inter-diffusion conditions,and Au-In IMC can withstand the sub-sequent wafer processes without degradation.Therefore,An-In solid-liquid inter-diffusion(SLID)process is a promising low-temperature bonding technology.Au-In SLID bonding process had been studied in this work.0.4μm SiO/SiN dielectric layer,3.5μm electroplated Au and 1.7μm evaporated In were coated before bonding process.Preheating the bonding plates before the wafers transferred on-to or heating the wafers on the plates were compared in the bonding process.The electrical intercon-nection test,Au/In concentration analysis on Au-In IMC bonding layer and the de-bonding shear force test had been conducted.The measured results of electrical performance test,An/In component analysis and shear test demonstrate that the chips without heating before the pressing achieved good electrical interconnection,stable IMC components and de-bonding shear force beyond 100 MPa.The necessity of preventing Au-In inter-diffusion before wafer bonding has been convincingly verified with massive measurement results.