Low temperature Cu-Cu thermo-compression bonding with temporary passivation of self-assembled monolayer and its bond strength enhancement

Abstract Self-assembled monolayer (SAM) of alkane-thiol is formed on copper (Cu) thin layer coated on silicon (Si) wafer with the aim to protect the surface against excessive oxidation during storage in the room ambient. After 3 days of storage, the temporary SAM layer is desorbed with in situ anneal in inert ambient to uncover the clean Cu surface. A pair of wafers is bonded at 250 °C. Clear evidences of in-plane and out-of-plane Cu grain growth are observed resulting in a wiggling bonding interface. This gives rise to enhancement in shear strength in the bonded Cu Cu layer.

[1]  Kaustav Banerjee,et al.  3-D ICs: a novel chip design for improving deep-submicrometer interconnect performance and systems-on-chip integration , 2001, Proc. IEEE.

[2]  R. Gutmann,et al.  Wafer Level 3-D ICs Process Technology , 2008 .

[3]  Ranko Babić,et al.  Copper Protection by a Self-Assembled Monolayer of Alkanethiol Comparison with Benzotriazole , 2007 .

[4]  D. F. Lim,et al.  Void Density Reduction at the Cu–Cu Bonding Interface by Means of Prebonding Surface Passivation with Self-Assembled Monolayer , 2010 .

[5]  Chuan Seng Tan,et al.  Cu-Cu diffusion bonding enhancement at low temperature by surface passivation using self-assembled monolayer of alkane-thiol , 2009 .

[6]  K. Maex,et al.  Corrosion Inhibition by Thiol-Derived SAMs for Enhanced Wire Bonding on Cu Surfaces , 2004 .

[7]  Kuan-Neng Chen,et al.  Morphology and Bond Strength of Copper Wafer Bonding , 2004 .

[8]  T. Suga.  Cu-Cu Room Temperature Bonding - Current Status of Surface Activated Bonding(SAB) - , 2006 .

[9]  S. Sircar,et al.  Influence of Oxygen Pressure on the Oxidation Kinetics of Copper in Dry Air at Room Temperature , 1969 .

[10]  Young-Bae Park,et al.  Effect of Wet Pretreatment on Interfacial Adhesion Energy of Cu-Cu Thermocompression Bond for 3D IC Packages , 2009 .

[11]  Kuan-Neng Chen,et al.  The effect of forming gas anneal on the oxygen content in bonded copper layer , 2005 .

[12]  D. Hutt,et al.  Fluxless Soldering of Copper Substrates Using Self-Assembled Monolayers for Preservation , 2006, IEEE Transactions on Components and Packaging Technologies.

[13]  A. Fan,et al.  Copper Wafer Bonding , 1999 .

[14]  Zhiqiang Gao,et al.  Corrosion Protection of Copper by a Self‐Assembled Monolayer of Alkanethiol , 1997 .

[15]  K. Maex,et al.  In-situ cleaning and passivation of oxidized Cu surfaces by alkanethiols and its application to wire bonding , 2004 .

[16]  Chuan Seng Tan,et al.  Silicon Multilayer Stacking Based on Copper Wafer Bonding , 2005 .