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.

A Low Temperature, Non-Aggressive Wafer Level Hermetic Package With UV Cured SU8 Bond

2007 ◽  
Author(s):  
Yexian Wu ◽  
Guanrong Tang ◽  
Jing Chen
Keyword(s):  
Low Temperature ◽  
Bonding Temperature ◽  
Adhesive Layer ◽  
Glass Wafer ◽  
Wafer Level ◽  
Etching Technique ◽  
Micro Electro Mechanical Systems ◽  
Level 3 ◽  
A New Technique ◽  
Hermetic Package

In this paper, we present a new technique that could realize wafer level 3-D hermetic package in a very low bonding temperature (120°C) for MEMS (Micro-electro-mechanical Systems) devices. Microcavities were etched on a host glass wafer and were bonded with a carrier silicon wafer. MicroChem SU-8 photoresist is used as the intermediate adhesive layer between the host and carrier wafer. The devices were fabricated by self-aligning etching technique and were finally sealed by coating the structures with sputtered aluminum. Helium leak testing is carried out to verify the hermetic characteristics of the package, 99.7% of the tested devices were qualified. This technology shows a significant improvement of the hermeticity properties of adhesive bonded cavities, making it particularly suitable for applications on gas-tightness with low temperature, non-aggressive demands.

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.

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.

Integrated Microsystems

2012 ◽  
Vol 81 ◽  
pp. 55-64 ◽  
Author(s):  
Masayoshi Esashi ◽  
Shuji Tanaka
Keyword(s):  
Wireless Systems ◽  
Tactile Sensor ◽  
Wafer Level ◽  
Micro Electro Mechanical Systems ◽  
Silicon Chips ◽  
Open Collaboration ◽  
Wafer Level Packaging ◽  
Integrated Microsystems ◽  
Safety Systems ◽  
The Cost

Technology called MEMS (Micro Electro Mechanical Systems) or microsystems are heterogeneous integration on silicon chips and play important roles as sensors. MEMS as switches and resonators fabricated on LSI are needed for future multi-band wireless systems. MEMS for safety systems as event driven tactile sensor network for nursing robot are developed. Wafer level packaging for MEMS and open collaboration to reduce the cost for the development are discussed.

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.

Ceramic Via Wafer-Level Packaging for MEMS

2005 ◽  
Author(s):  
John M. Heck ◽  
Leonel R. Arana ◽  
Bill Read ◽  
Thomas S. Dory
Keyword(s):  
Mems Devices ◽  
Wafer Level ◽  
Micro Electro Mechanical Systems ◽  
Mems Switches ◽  
Mems Packaging ◽  
Wafer Level Packaging ◽  
Novel Approach ◽  
Electrical Interconnection ◽  
Tin Silver Copper ◽  
Board Level

We will present a novel approach to wafer level packaging for micro-electro-mechanical systems. Like most common MEMS packaging methods today, our approach utilizes a wafer bonding process between a cap wafer and a MEMS device wafer. However, unlike the common methods that use a silicon or glass cap wafer, our approach uses a ceramic wafer with built-in metal-filled vias, that has the same size and shape as a standard 150 mm silicon wafer. This ceramic via wafer packaging method is much less complex than existing methods, since it provides hermetic encapsulation and electrical interconnection of the MEMS devices, as well as a solderable interface on the outside of the package for board-level interconnection. We have demonstrated successful ceramic via wafer-level packaging of MEMS switches using eutectic gold-tin solder as well as tin-silver-copper solder combined with gold thermo-compression bonding. In this paper, we will present the ceramic via MEMS package architecture and discuss the associated bonding and assembly processes.

An Investigation of Residual Stress Effects due to the Anodic Bonding of Glass and Silicon in MEMS Fabrication

2006 ◽  
Vol 5-6 ◽  
pp. 501-508 ◽  
Author(s):  
I. Sadaba ◽  
Colin H.J. Fox ◽  
Stewart McWilliam
Keyword(s):  
Residual Stress ◽  
Anodic Bonding ◽  
Fe Model ◽  
Moderate Pressure ◽  
Mems Devices ◽  
Wafer Level ◽  
Micro Electro Mechanical Systems ◽  
Ion Migration ◽  
Compositional Gradients ◽  
Rate Sensor

Anodic bonding is widely-used in the fabrication of Micro-Electro-Mechanical Systems (MEMS) devices to join silicon and glass components. The process involves the application of temperature, moderate pressure and an electric field. This paper investigates residual stresses arising during anodic bonding, focusing on the resulting induced distortions. Components of a MEMS silicon rate sensor, in which a silicon wafer is anodically bonded to Pyrex™ glass, were used as the vehicle for the investigation. Distortions generated by the anodic bonding process when using two different electrode configurations (point and planar) were measured using a surface optical profiler. These showed a particular pattern across the wafers for both configurations. An efficient FEM study was carried out to model the qualitative effect of the following residual stress sources; thermal stress, glass shrinkage due to structural relaxation and compositional gradients due to ion migration. Importantly, the FE model takes account the actual multi-device wafer-level configuration, as opposed to a single device. The results demonstrate that compositional gradients can make a significant contribution to the observed pattern of distortions.

Hermetic Packaging Technique Featuring Through-Wafer Interconnects and Low Temperature Direct Bond

2008 ◽  
Author(s):  
James Lee ◽  
Tony Rogers
Keyword(s):  
Low Temperature ◽  
Wafer Bonding ◽  
High Strength ◽  
Mems Devices ◽  
Wafer Level ◽  
Direct Bond ◽  
Hermetic Packaging ◽  
Wafer Level Packaging ◽  
Hermetic Seal ◽  
Silicon Silicon

A novel wafer level packaging method suitable for low production volumes, R&D, and multi-project wafers is presented, providing a hermetic seal suitable for vacuum encapsulation with wafers bonded at a low temperature. Hermetic through-wafer interconnects are bump bonded to a CMOS chip encapsulated by bonding a cap wafer after activating surfaces with free radicals, the Silicon-Silicon direct bond is then annealed to a high strength at 200°C to avoid chip damage. The application for which this system is proposed is an implantable multi-contact active nerve electrode for the treatment of epilepsy via vagus nerve stimulation. Although intended for human implantation of integrated systems, this technology may be applied across a range of devices requiring hermetic or vacuum sealing and through-wafer interconnection. Solid electroplated through-wafer interconnects (aspect ratio 5) enable hermetic interconnection of direct bonded packages with low connection impedance, offering benefits across a range of packaging applications. A key feature of this packaging method is it’s versatility, the proposed embodiment features chip to wafer bonding with an ASIC, but the package is equally suitable for MEMS devices and also for wafer to wafer bonding.

Wafer Level Hermetic Packaging for RF-MEMS Devices Using Electroplated Gold Layers

2006 ◽  
Vol 326-328 ◽  
pp. 617-620
Author(s):  
Gil Soo Park ◽  
Ji Hyuk Yu ◽  
Sang Won Seo ◽  
Woo Beom Choi ◽  
Kyeong Kap Paek ◽  
...  
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Rf Mems ◽  
Gold Films ◽  
Mems Devices ◽  
Wafer Level ◽  
Promising Technique ◽  
Hermetic Packaging ◽  
Thermocompression Bonding ◽  
Via Hole

Thermocompression bonding of electroplated gold is a promising technique for achieving low temperature, wafer level hermetic bonding without the application of an electric field or high temperature. Silicon wafers were completely bonded at 320 at a pressure of 2.5. The interconnection between the packaged devices and external terminal did not need metal filling and was made by gold films deposited on the sidewall of the via-hole. In the hermeticity test, packaged wafers had the leak rate of 2.74 ± 0.61 × 10-11 Pa m3/s. In the result of application in packaging of FBAR filter, the insertion loss is increased from -0.75dB to -1.09dB at 1.9.

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