Characterization of Wafer Level Metal Thermo-Compression Bonding

2010 ◽  
Vol 2010 (DPC) ◽  
pp. 002326-002360
Author(s):  
Erkan Cakmak ◽  
Bioh Kim ◽  
Viorel Dragoi
Keyword(s):  
Surface Treatment ◽  
Metal Surface ◽  
Bonding Temperature ◽  
Transient Liquid Phase ◽  
Bonding Process ◽  
Bending Test ◽  
Strength Analysis ◽  
Mems Devices ◽  
Wafer Level ◽  
Bond Quality

The process of wafer-level bonding is being successfully used to form MEMS devices. Wafer level bonding may be realized by different methods such as thermo compression, transient liquid phase, anodic, glass frit, or polymer bonding. These methods have different requirements and the choice of wafer level bonding method is defined by the application type. Metal TCB has a wide variety of applications with materials of choice including Au, Cu and Al. 3D electrical connections are created by the use of Cu-Cu TCB; while CMOS MEMS devices may be realized by Al-Al TCB. In this study the wafer level bonding process of Cu-Cu and Al-Al TCB are characterized. The effects and significance of various bonding process parameters and surface treatment methods are reported on the final bond interfaces integrity and strength. Analysis methods include SAM, SEM, AFM, and four point bending test. Al-Al TCB samples were investigated on the interfacial adhesion energy and bond quality. IAE and bond quality were found to be positively correlated with bonding temperature. A bonding temperature of 500 °C or greater is necessary to obtain bond strengths of 8–10 J/m2. A positive relation between IAE and bonding temperature was observed for Cu-Cu TCB. IAE's of greater then 10 J/m2 were obtained on bonded samples that do not show a post bond residual seam on the bonding interface. An acid based pre treatment was shown to impact the surface properties of the initial metal surface hence affecting the IAE. Post bond annealing processes showed the most significant impact on the IAE of the Cu-Cu TCB system. To obtain comparable IAE values the Al-Al TCB method requires a higher bonding temperature. However the Cu-Cu TCB is sensitive to the initial metal surface condition and requires surface treatment processes prior to bonding to obtain high quality bonding results.

Aluminum Thermo Compression Bonding Characterization

2009 ◽  
Vol 1222 ◽  
Author(s):  
Erkan Cakmak ◽  
Viorel Dragoi ◽  
Eric Pabo ◽  
Thorsten Matthias ◽  
T. L. Alford
Keyword(s):  
Interfacial Adhesion ◽  
Microelectromechanical Systems ◽  
Bonding Temperature ◽  
Acoustic Microscopy ◽  
Bending Test ◽  
Wafer Level ◽  
Bond Quality ◽  
Four Point Bending ◽  
Bond Strengths ◽  
Four Point Bending Test

AbstractWafer level bonding is an important technology for the manufacturing of numerous Microelectromechanical Systems. In this work the aluminum thermo-compression wafer bonding is characterized. The effects and significance of various bond process parameters and surface treatment methods are reported on the final bond interfaces integrity and strength. Experimental variables include the bonding temperature, bonding time, and bonding atmosphere (forming gas and inert gas). Bonded wafer samples were investigated with scanning acoustic microscopy, scanning electron microscopy, and four point bending test. Interfacial adhesion energy and bond quality were found to be positively correlated with bonding temperature. A bonding temperature of 500 °C or greater is necessary to obtain bond strengths of 8-10 J/m2.

Low Temperature Wafer Level Bonding Using Benzocyclobutene Adhesive Polymers

2012 ◽  
Vol 2012 (DPC) ◽  
pp. 1-24
Author(s):  
Michael Gallagher ◽  
Jong-Uk Kim ◽  
Eric Huenger ◽  
Kai Zoschke ◽  
Christina Lopper ◽  
...  
Keyword(s):  
Low Temperature ◽  
Wafer Bonding ◽  
Flip Chip ◽  
Bonding Temperature ◽  
Bonding Process ◽  
Curing Temperature ◽  
Wafer Level ◽  
Mechanical Adhesion ◽  
3D Stacking ◽  
Dry Etch

3D stacking, one of the 3D integration technologies using through silicon vias (TSVs), is considered as a desirable 3D solution due to its cost effectiveness and matured technical background. For successful 3D stacking, precisely controlled bonding of the two substrates is necessary, so that various methods and materials have been developed over the last decade. Wafer bonding using polymeric adhesives has advantages. Surface roughness, which is critical in direct bonding and metal-to-metal bonding, is not a significant issue, as the organic adhesive can smooth out the unevenness during bonding process. Moreover, bonding of good quality can be obtained using relatively low bonding pressure and low bonding temperature. Benzocyclobutene (BCB) polymers have been commonly used as bonding adhesives due to their relatively low curing temperature (~250 °C), very low water uptake (<0.2%), excellent planarizing capability, and good affinity to Cu metal lines. In this study, we present wafer bonding with BCB at various conditions. In particular, bonding experiments are performed at low temperature range (180 °C ~ 210 °C), which results in partially cured state. In order to examine the effectiveness of the low temperature process, the mechanical (adhesion) strength and dimensional changes are measured after bonding, and compared with the values of the fully cured state. Two different BCB polymers, dry-etch type and photo type, are examined. Dry etch BCB is proper for full-area bonding, as it has low degree of cure and therefore less viscosity. Photo-BCB has advantages when a pattern (frame or via open) is to be structured on the film, since it is photoimageable (negative tone), and its moderate viscosity enables the film to sustain the patterns during the wafer bonding process. The effect of edge beads at the wafer rim area and the soft cure (before bonding) conditions on the bonding quality are also studied. Alan/Rey ok move from Flip Chip and Wafer Level Packaging 1-6-12.

Low-temperature Cu-Cu thermocompression bonding for encapsulation of a MEMS mirror

2019 ◽  
Vol 2019 (NOR) ◽  
pp. 000012-000016
Author(s):  
Henri Ailas ◽  
Jaakko Saarilahti ◽  
Tuomas Pensala ◽  
Jyrki Kiihamäki
Keyword(s):  
Low Temperature ◽  
Bond Strength ◽  
Bonding Temperature ◽  
Bonding Process ◽  
Ex Situ ◽  
High Yield ◽  
Maximum Temperature ◽  
Wafer Level ◽  
Cu Films ◽  
Thermocompression Bonding

Abstract In this study, a low temperature wafer-level packaging process aimed for encapsulating MEMS mirrors was developed. The glass cap wafer used in the package has an antireflective (AR) coating that limits the maximum temperature of the bonding process to 250°C. Copper thermocompression was used as copper has a high self-diffusivity and the native oxidation on copper surfaces can be completely removed with combination of ex situ acetic acid wet-etch and in situ forming gas anneal. Making it suitable for a development of a low temperature bonding process. In this work, bonding on of sputtered and electrodeposited copper films was studied on temperatures ranging from 200°C to 300°C as well as the effect of pretreatment on bond strength. The study presents a successful thermocompression bonding process for sputtered Cu films at a low temperature of 200°C with high yield of 97 % after dicing. The bond strength was recorded to be 75 MPa, well above the MIL-STD-883E standard (METHOD 2019.5) rejection limit of 6.08 MPa. The high dicing yield and bond strength suggest that the thermocompression bonding could be possible even at temperatures below 200°C. However, the minimum bonding temperature was not yet determined in this study.

scholarly journals Wafer Level Solid Liquid Interdiffusion Bonding: Formation and Evolution of Microstructures

2020 ◽  
Author(s):  
V. Vuorinen ◽  
H. Dong ◽  
G. Ross ◽  
J. Hotchkiss ◽  
J. Kaaos ◽  
...  
Keyword(s):  
Microelectromechanical Systems ◽  
Bonding Temperature ◽  
Transient Liquid Phase ◽  
Wafer Level ◽  
Simultaneous Formation ◽  
Die Attach ◽  
Local Stresses ◽  
Formation And Evolution ◽  
Solid Liquid ◽  
Global And Local

Abstract Wafer-level solid liquid interdiffusion (SLID) bonding, also known as transient liquid-phase bonding, is becoming an increasingly attractive method for industrial usage since it can provide simultaneous formation of electrical interconnections and hermetic encapsulation for microelectromechanical systems. Additionally, SLID is utilized in die-attach bonding for electronic power components. In order to ensure the functionality and reliability of the devices, a fundamental understanding of the formation and evolution of interconnection microstructures, as well as global and local stresses, is of utmost importance. In this work a low-temperature Cu-In-Sn based SLID bonding process is presented. It was discovered that by introducing In to the traditional Cu-Sn metallurgy as an additional alloying element, it is possible to significantly decrease the bonding temperature. Decreasing the bonding temperature results in lower CTE induced global residual stresses. However, there are still several open issues to be studied regarding the effects of dissolved In on the physical properties of the Cu-Sn intermetallics. Additionally, partially metastable microstructures were observed in bonded samples that did not significantly evolve during thermal annealing. This indicates the Cu-In-Sn SLID bond microstructure is extremely stable.

Mechanics of Direct Wafer Bonding

2003 ◽  
Author(s):  
K. T. Turner ◽  
S. M. Spearing
Keyword(s):  
Wafer Bonding ◽  
Microelectromechanical Systems ◽  
Surface Condition ◽  
Bonding Process ◽  
Mems Devices ◽  
Wafer Level ◽  
Modeling Framework ◽  
Etch Patterns ◽  
Direct Wafer Bonding ◽  
Bonding Failure

Direct wafer bonding, also known as fusion bonding, has emerged as a key process in the manufacture of microelectromechanical systems (MEMS). The use of wafer bonding increases design flexibility, allows integration of dissimilar materials, and permits wafer-level packaging. While direct wafer bonding processes are becoming more prevalent in the fabrication of MEMS devices, failure during the bonding process is often a problem and is not completely understood. A modeling framework, based on the mechanics of the bonding process, has been on the mechanics of the bonding process, has been developed to correlate bonding failure to wafer geometry, surface condition, and etch patterns. The modeling approach is based on an energy balance between the reduction in surface energy as the bond is formed and the strain energy that is stored in the wafers as they conform to each other. The model allows the effect of flatness deviations, wafer geometry (i.e. thickness, diameter), wafer mounting, and etched features on the bonding process to be shown. Modeling results demonstrate that wafer bow, wafer thickness, and certain types of etch patterns are critical factors in controlling bonding success. Bonding experiments, in which specific flatness deviations and etch patterns have been introduced on wafers prior to bonding, have been carried out and compared to the modeling results. The understanding of the process gained through the modeling can be used to set tolerances on wafers, assist in mask layout, and guide the design of bonding equipment to ensure success in direct wafer bonding processes.

scholarly journals Overview of transient liquid phase and partial transient liquid phase bonding

2011 ◽  
Vol 46 (16) ◽  
pp. 5305-5323 ◽  
Author(s):  
Grant O. Cook ◽  
Carl D. Sorensen
Keyword(s):  
Liquid Phase ◽  
Bonding Temperature ◽  
Transient Liquid Phase ◽  
Isothermal Solidification ◽  
Bonding Process ◽  
Advantages And Disadvantages ◽  
Tlp Bonding ◽  
Wide Range ◽  
Kinetics Of ◽  
Bonding Kinetics

AbstractTransient liquid phase (TLP) bonding is a relatively new bonding process that joins materials using an interlayer. On heating, the interlayer melts and the interlayer element (or a constituent of an alloy interlayer) diffuses into the substrate materials, causing isothermal solidification. The result of this process is a bond that has a higher melting point than the bonding temperature. This bonding process has found many applications, most notably the joining and repair of Ni-based superalloy components. This article reviews important aspects of TLP bonding, such as kinetics of the process, experimental details (bonding time, interlayer thickness and format, and optimal bonding temperature), and advantages and disadvantages of the process. A wide range of materials that TLP bonding has been applied to is also presented. Partial transient liquid phase (PTLP) bonding is a variant of TLP bonding that is typically used to join ceramics. PTLP bonding requires an interlayer composed of multiple layers; the most common bond setup consists of a thick refractory core sandwiched by thin, lower-melting layers on each side. This article explains how the experimental details and bonding kinetics of PTLP bonding differ from TLP bonding. Also, a range of materials that have been joined by PTLP bonding is presented.

Laser Bonding and Modeling for Wafer-Level and Chip-Scale Packaging of Micro-Electro-Mechanical Systems

2002 ◽  
Author(s):  
Yi Tao ◽  
Ajay P. Malshe ◽  
W. D. Brown
Keyword(s):  
Low Temperature ◽  
Continuous Wave ◽  
Bonding Temperature ◽  
Mems Devices ◽  
Wafer Level ◽  
Micro Electro Mechanical Systems ◽  
Silicon Chips ◽  
Laser Bonding ◽  
Sealing Ring ◽  
Carbon Dioxide Co2

In this work, low temperature selective solder (Pb37/Sn63) bonding of silicon chips or wafers for MEMS applications using a continuous wave (CW) carbon dioxide (CO2) laser at a wavelength of 10.6μm was examined. The low reflectivity, fair transmittance, and high absorptivity of silicon at the 10.6μm wavelength led to selective heating of the silicon and reflow of an electroplated or screen printed intermediate solder layer which produced silicon-solder-silicon joints. Finite element simulations were carried out to optimize the process parameters in order to achieve uniform heating and minimum induced thermal stress. The bonding process was performed on the fixtures in a vacuum chamber at an air pressure of one milliTorr to achieve fluxless soldering and vacuum encapsulation of silicon dies. The bonding temperature at the sealing ring was close to the reflow temperature of the eutectic lead tin solder, 183°C. Pull test results showed that the joint was sufficiently strong and could not be separated before the silicon die broke. Helium leak testing showed that the leak rate of the package was below 10−8 atm · cc/sec under optimized bonding conditions. The results of the Design of Experiment (DOE) method indicated that both laser incident power and scribe velocity significantly influenced bonding results. This novel method is especially suitable for vacuum bonding wafers containing MEMS and other micro devices with low temperature budgets where managing stress distribution is important. Further, sealed encapsulated and released wafers can be diced without damaging the MEMS devices at wafer scale.

Reduced Temperature Metal Based Bonding Processes for Wafer Level Packaging and 3D Integration

2012 ◽  
Vol 2012 (DPC) ◽  
pp. 002509-002542 ◽  
Author(s):  
Eric F. Pabo ◽  
Viorel Dragoi ◽  
Tian Tang ◽  
Thorsten Matthias
Keyword(s):  
Melting Point ◽  
Bonding Temperature ◽  
Transient Liquid Phase ◽  
Bonding Process ◽  
Maximum Temperature ◽  
Eutectic Bonding ◽  
Working Temperature ◽  
Solid Diffusion ◽  
Step Coverage ◽  
Tlp Bonding

Metal based bonding processes are commonly selected because of the need for a conductive interface along with a high degree of hermeticity. Metal based bonding process can be based on solid diffusion which is commonly called thermo-compression or can be based on liquefying part or all of the metal in the bond interface. Thermo-compression bonding has the primary challenges of being slow because it is based on solid diffusion and has very poor step coverage. The most common liquid metal bonding processes are commonly called solder or eutectic bonding. The solder or eutectic bonding process allows some step coverage and the time required for the process is driven by the maximum temperature required, the residence time at this temperature and the maximum ramp rate. The process temperature and the required process time can be reduced by selecting an alloy with a low melting point; however this reduced melting point reduces the maximum post bond working temperature. TLP (Transient Liquid Phase) also known as SLID (Solid Liquid Inter Diffusion) bonding decouples the bonding temperature from the post bond maximum working temperature which allows the selection of alloys that reduce the bonding temperature while maintaining a high post bond maximum working temperature. For example a Cu-Sn TLP process can be performed at 280°C that will survive post bond temperature of up to 415°C. The fundamentals of TLP bonding will be reviewed and data will be presented for Cu-Sn TLP bonding

An all-silicon process platfom for wafer-level vacuum packaged MEMS devices

2021 ◽  
pp. 1-1
Author(s):  
Mustafa Mert Torunbalci ◽  
Hasan Dogan Gavcar ◽  
Ferhat Yesil ◽  
Said Emre Alper ◽  
Tayfun Akin
Keyword(s):  
Mems Devices ◽  
Wafer Level

scholarly journals Control of Local Hardness Gradient of Metal Surface by Inclined Surface Treatment Using Ultrasonic Nanocrystal Surface Modification

2021 ◽  
Vol 8 (2) ◽  
pp. 533-546
Author(s):  
Yeong-Kwan Jo ◽  
Yeong-Wook Gil ◽  
Do-Sik Shim ◽  
Young-Sik Pyun ◽  
Sang-Hu Park
Keyword(s):  
Surface Modification ◽  
Surface Treatment ◽  
Metal Surface ◽  
Incident Angle ◽  
Surface Hardness ◽  
Parameter Study ◽  
Local Hardness ◽  
Practical Usefulness ◽  
Inclined Surface ◽  
Hardness Gradient

AbstractWe propose an effective method to control the local hardness and morphology of a metal surface by tilting the incident angle of a horn during ultrasonic nanocrystal surface modification (UNSM). In this study, surface treatment using UNSM was performed on an S45C specimen and a parameter study was conducted for optimization. The process parameters were the feeding rate, static load, striking force, and processing angle (Ф). In particular, the Ф was analyzed by tilting the horn by 0°, 10°, 20°, 30°, 40°, and 45° to understand its effect on surface hardness and changes in the morphology. From fundamental experiments, some important phenomena were observed, such as grain-microstructure changes along the processing and thickness directions. Furthermore, to verify the practical usefulness of this study, a flat and a hemispherical specimen of S45C material were treated using UNSM with various values of Ф. A significant change in hardness (an increase from 2–45%) and a gradual hardness gradient on the tested specimens could be easily realized by the proposed method. Therefore, we believe that the method is effective for controlling the mechanical hardness of a metal surface.

Sign in / Sign up

Export Citation Format

Share Document