Effect of Au Film Thickness and Surface Roughness on Room-Temperature Wafer Bonding and Wafer-Scale Vacuum Sealing by Au-Au Surface Activated Bonding

Au-Au surface activated bonding (SAB) using ultrathin Au films is effective for room-temperature pressureless wafer bonding. This paper reports the effect of the film thickness (15–500 nm) and surface roughness (0.3–1.6 nm) on room-temperature pressureless wafer bonding and sealing. The root-mean-square surface roughness and grain size of sputtered Au thin films on Si and glass wafers increased with the film thickness. The bonded area was more than 85% of the total wafer area when the film thickness was 100 nm or less and decreased as the thickness increased. Room-temperature wafer-scale vacuum sealing was achieved when Au thin films with a thickness of 50 nm or less were used. These results suggest that Au-Au SAB using ultrathin Au films is useful in achieving room-temperature wafer-level hermetic and vacuum packaging of microelectromechanical systems and optoelectronic devices.

[1]  T. Itoh,et al.  Room-temperature pressureless wafer-scale hermetic sealing in air and vacuum using surface activated bonding with ultrathin Au films , 2019, Japanese Journal of Applied Physics.

[2]  T. Itoh,et al.  Comparison of Argon and Oxygen Plasma Treatments for Ambient Room-Temperature Wafer-Scale Au–Au Bonding Using Ultrathin Au Films , 2019, Micromachines.

[3]  Y. Kurashima,et al.  Room-temperature bonding of single-crystal diamond and Si using Au/Au atomic diffusion bonding in atmospheric air , 2018, Microelectronic Engineering.

[4]  Hideaki Matsuzaki,et al.  High-Speed InP/InGaAsSb DHBT on High-Thermal-Conductivity SiC Substrate , 2018, IEEE Electron Device Letters.

[5]  Y. Kurashima,et al.  Room-temperature Au–Au bonding in atmospheric air using direct transferred atomically smooth Au film on electroplated patterns , 2018 .

[6]  Shuji Tanaka,et al.  Bonding-Based Wafer-Level Vacuum Packaging Using Atomic Hydrogen Pre-Treated Cu Bonding Frames , 2018, Micromachines.

[7]  T. Itoh,et al.  Properties of various plasma surface treatments for low-temperature Au–Au bonding , 2018 .

[8]  L. Martinu,et al.  Review Article: Stress in thin films and coatings: Current status, challenges, and prospects , 2018 .

[9]  K. Schjølberg-Henriksen,et al.  Characterization of interfacial morphology of low temperature, low pressure Au–Au thermocompression bonding , 2018 .

[10]  E. Higurashi.  Heterogeneous integration based on low-temperature bonding for advanced optoelectronic devices , 2017 .

[11]  Tadatomo Suga,et al.  Room-Temperature Bonding of Wafers with Smooth Au Thin Films in Ambient Air Using a Surface-Activated Bonding Method , 2017, IEICE Trans. Electron..

[12]  Takeshi Sato,et al.  Room-Temperature Gold-Gold Bonding Method Based on Argon and Hydrogen Gas Mixture Atmospheric-Pressure Plasma Treatment for Optoelectronic Device Integration , 2016, IEICE Trans. Electron..

[13]  Tadatomo Suga,et al.  Review of Low-Temperature Bonding Technologies and Their Application in Optoelectronic Devices , 2016 .

[14]  Hideki Takagi,et al.  Replication of atomically smooth surface shape onto electroplated Au patterns by lift-off process and room-temperature Au–Au bonding in atmospheric air , 2014 .

[15]  Tadatomo Suga,et al.  Low-Temperature Solid-State Bonding Using Hydrogen Radical Treated Solder for Optoelectronic and MEMS Packaging , 2014 .

[16]  Hiroshi Toshiyoshi,et al.  3-D Silicon-on-Insulator Integrated Circuits With NFET and PFET on Separate Layers Using Au/SiO2 Hybrid Bonding , 2014, IEEE Transactions on Electron Devices.

[17]  Shuji Tanaka,et al.  Wafer-level hermetic MEMS packaging by anodic bonding and its reliability issues , 2014, Microelectron. Reliab..

[18]  Y. Kurashima,et al.  Room temperature wafer bonding of metal films using flattening by thermal imprint process , 2013 .

[19]  F. Fournel,et al.  Measurement of bonding energy in an anhydrous nitrogen atmosphere and its application to silicon direct bonding technology , 2012 .

[20]  M. Uomoto,et al.  Atomic diffusion bonding of wafers in air with thin Au films and its application to optical devices fabrication , 2012, 2012 3rd IEEE International Workshop on Low Temperature Bonding for 3D Integration.

[21]  Tadatomo Suga,et al.  Low-temperature hermetic packaging for microsystems using Au–Au surface-activated bonding at atmospheric pressure , 2012 .

[22]  T. Suga,et al.  Low-Temperature Bonding of GaN on Si Using a Nonalloyed Metal Ohmic Contact Layer for GaN-Based Heterogeneous Devices , 2012, IEEE Journal of Quantum Electronics.

[23]  D. F. Lim,et al.  Low temperature wafer-level bonding for hermetic packaging of 3D microsystems , 2011 .

[24]  T Kawanishi,et al.  Passive Alignment and Mounting of LiNbO$_3$ Waveguide Chips on Si Substrates by Low-Temperature Solid-State Bonding of Au , 2011, IEEE Journal of Selected Topics in Quantum Electronics.

[25]  Zhang Xin,et al.  Thickness dependence of grain size and surface roughness for dc magnetron sputtered Au films , 2010 .

[26]  Jianmin Miao,et al.  Optimization of sputtered Cr/Au thin film for diaphragm-based MEMS applications , 2009 .

[27]  T. Suga,et al.  Au–Au Surface-Activated Bonding and Its Application to Optical Microsensors With 3-D Structure , 2009, IEEE Journal of Selected Topics in Quantum Electronics.

[28]  Tadatomo Suga,et al.  Optical Microsensors Integration Technologies for Biomedical Applications , 2009, IEICE Trans. Electron..

[29]  Tadatomo Suga,et al.  Room-Temperature Bonding of Vertical-Cavity Surface-Emitting Laser Chips on Si Substrates Using Au Microbumps in Ambient Air , 2008 .

[30]  T. Suga,et al.  Low-Temperature Bonding of Laser Diode Chips on Silicon Substrates Using Plasma Activation of Au Films , 2007, IEEE Photonics Technology Letters.

[31]  Q. Wang,et al.  Application of Au-Sn eutectic bonding in hermetic radio-frequency microelectromechanical system wafer level packaging , 2006 .

[32]  Yong Kook Kim,et al.  Low-Temperature Silicon Wafer-Scale Thermocompression Bonding Using Electroplated Gold Layers in Hermetic Packaging , 2005 .

[33]  H. Okada,et al.  Room temperature vacuum sealing using surfaced activated bonding with Au thin films [microresonator example] , 2005, The 13th International Conference on Solid-State Sensors, Actuators and Microsystems, 2005. Digest of Technical Papers. TRANSDUCERS '05..

[34]  M. Schmidt,et al.  Characterization of wafer-level thermocompression bonds , 2004, Journal of Microelectromechanical Systems.

[35]  Srinivas Tadigadapa,et al.  Tin-based solder bonding for MEMS fabrication and packaging applications , 2004 .

[36]  Henrik Jakobsen,et al.  Strong, high-yield and low-temperature thermocompression silicon wafer-level bonding with gold , 2004 .

[37]  I. Ohlídal,et al.  Atomic Force Microscopy Characterization of ZnTe Epitaxial Thin Films , 2003 .

[38]  T. Suga,et al.  Effect of Surface Roughness on Room-Temperature Wafer Bonding by Ar Beam Surface Activation , 1998 .

[39]  M. Esashi,et al.  Vacuum packaging for microsensors by glass-silicon anodic bonding , 1994 .

[40]  W. Maszara,et al.  Bonding of silicon wafers for silicon‐on‐insulator , 1988 .

[41]  D. W. Hoffman,et al.  Internal stresses in Cr, Mo, Ta, and Pt films deposited by sputtering from a planar magnetron source , 1982 .

[42]  G. Stoney.  The Tension of Metallic Films Deposited by Electrolysis , 1909 .

[43]  Y. Kurashima,et al.  Room-temperature wafer scale bonding using smoothed Au seal ring surfaces for hermetic sealing , 2015 .

[44]  Tetsuya Kawanishi,et al.  Low-Temperature Au-to-Au Bonding for LiNbO3/Si Structure Achieved in Ambient Air , 2007, IEICE Trans. Electron..

[45]  U. Gösele,et al.  Low Vacuum Wafer Bonding , 1999 .

[46]  W. Brantley.  Calculated elastic constants for stress problems associated with semiconductor devices , 1973 .