Low temperature Si-Si, SiO2-SiO2 covalent bonding structures with thin siloxane layer

We present new Si to Si, SiO2 to SiO2 bonding technologies for low temperature applications (<200°C). Direct bonding process between Si (or SiO2) substrates makes high bonding strength without contamination problems. However, high temperature over 1000°C is needed for the reliable Si to Si and SiO2 to SiO2 direct bonding processes. To reduce the bonding temperature, thin siloxane layer and low-powered oxygen plasma treatment was used in this study. We used dimethyl siloxane layer having siloxane chains (-Si-O-)n and methyl ends. Siloxane layer is able to be bonded strongly with Si-based substrates at low temperature (<200°C) when oxygen plasma is treated on it. Polymerized siloxane layer such as PDMS has much higher coefficient of thermal expansion (CTE) of 300ppm/K than Si of 2.6ppm/K. When the bonded structure is cooled or heated, the interfaces is possibly distorted and cracked by the high residual stress between siloxane layer and Si substrate. To solve these problems, we developed new fabrications of reducing the siloxane layer thickness to 3∼4nm, that is the monomer layer levels. Extremely thin thickness of siloxane layer prevented the problems of the CTE differences. The Si to Si bonding structure with siloxane layer showed strong adhesion properties in this study. The bonded body kept reliable bonding force when it was heated to high temperature (∼900°C). The feasible wafer-level bonding process was demonstrated. We investigated the siloxane layer thickness by TEM images. The bonding strength was confirmed by dicing test by 1mm and measured over 20MPa. We also expended this new development to SiO2 to SiO2 bonding structures. Low temperature bonding between non-Si substrates such as GaN was possible with thin siloxane layer when amorphous Si thin film was deposited on these substrates.

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Study on Bonding Properties of Copper and Aluminum in Nano Scale Using Molecular Dynamics Simulation

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.152-154.183 ◽

2012 ◽

Vol 152-154 ◽

pp. 183-187 ◽

Cited By ~ 6

Author(s):

Quang Cherng Hsu ◽

Yen Yu Cheng ◽

Bao Hsin Liu

Keyword(s):

High Temperature ◽

Low Temperature ◽

Bonding Strength ◽

High Speed ◽

Tensile Force ◽

Pure Aluminum ◽

Pure Copper ◽

Dynamics Simulation ◽

Low Speed ◽

Speed Condition

According to MD simulation results, pressing depth between two bonding materials will affect bonding strength. Alloy material (Al0.9Cu0.1) had void defect phenomenon in low bonding speed condition because the increasing chance of atom migration which will result in low bonding strength. High tensile speed causes material fracture phenomena happen earlier than low speed. Material stress in low speed is smaller than in high speed. Fracture morphology of material is different in different tensile speed. In low speed condition, material can be stretched thinner than in high speed condition. Material in high temperature has greater kinetic energy than low temperature; therefore, material in high temperature has better formability and behaves larger tensile strain than low temperature. For pure aluminum, when temperature raises to 900K which is close to melting point (933K), its crystal structure is no longer belongs to F.C.C. structure, so bonding strength is weaker than low temperature. Large size material has larger contact area than small size material; therefore, the tensile force and tensile strength of the former are larger than the latter. The order of bonding strength for these three materials is: binary alloy > pure copper > pure aluminum.

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Vacuum Adhesive Bonding and Stress Isolation for MEMS Resonant Pressure Sensor Package

Materials Science Forum ◽

10.4028/www.scientific.net/msf.694.896 ◽

2011 ◽

Vol 694 ◽

pp. 896-900 ◽

Cited By ~ 3

Author(s):

Yu Xin Li ◽

De Yong Chen ◽

Jun Bo Wang

Keyword(s):

Pressure Sensor ◽

Bonding Strength ◽

Adhesive Bonding ◽

Thermal Stresses ◽

Time Pressure ◽

Bonding Temperature ◽

Bonding Process ◽

Temperature Drift ◽

Stress Isolation ◽

Sensor Package

This paper presents a method of low temperature adhesive bonding and stress isolation for MEMS resonant pressure sensor hermetic packaging using non-photosensitive benzo-cyclo-butene (BCB) from Dow Co. According to the bonding process, pre-bake time, pumping time, pressure placed on the sensor and the thickness of crosslink layer are the most important factors. Stress isolation is designed to minimize thermal stresses to the resonant pressure sensor package. Experimental results show that this bonding process is a viable for MEMS resonant pressure sensor with the bonding temperature below 250°C, measured bonding strength more than 30MPa, the temperature drift less than 0.05%/°C in the range of -40°C to 70°C(10% of that without stress isolation), and the bonding strength maintains well after thermal treatments, handling, bench testing and implantations.

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TLP Bonding Technologies for Micro Joining and 3D Packaging

Additional Conferences (Device Packaging HiTEC HiTEN & CICMT) ◽

10.4071/2010dpc-wa12 ◽

2010 ◽

Vol 2010 (DPC) ◽

pp. 001221-001252 ◽

Cited By ~ 1

Author(s):

Kei Murayama ◽

Mitsuhiro Aizawa ◽

Mitsutoshi Higashi

Keyword(s):

High Temperature ◽

Melting Point ◽

Low Temperature ◽

Wafer Bonding ◽

Bonding Process ◽

Tlp Bonding ◽

Hermetic Sealing ◽

Low Temperature Bonding ◽

Free Material ◽

Bonding Technique

The bonding technique for High density Flip Chip(F.C.) packages requires a low temperature and a low stress process to have high reliability of the micro joining ,especially that for sensor MEMS packages requires hermetic sealing so as to ensure their performance. The Transient Liquid Phase (TLP) bonding, that is a kind of diffusion bonding is a technique that connects the low melting point material such as Indium to the higher melting point metal such as Gold by the isothermal solidification and high-melting-point intermetallic compounds are formed. Therefore, it is a unique joining technique that can achieve not only the low temperature bonding and also the high temperature reliability. The Gold-Indium TLP bonding technique can join parts at 180 degree C and after bonding the melting point of the junction is shifted to more than 495 degree C, therefore itfs possible to apply the low temperature bonding lower than the general use as a lead free material such as a SAC and raise the melting point more than AuSn solder which is used for the high temperature reliability usage. Therefore, the heat stress caused by bonding process can be expected to be lowered. We examined wafer bonding and F.C bonding plus annealing technique by using electroplated Indium and Gold as a joint material. We confirmed that the shear strength obtained at the F.C. bonding plus anneal technique was equal with that of the wafer bonding process. Moreover, it was confirmed to ensure sufficient hermetic sealing in silicon cavity packages that had been bonded at 180 degree C. And the difference of the thermal stress that affect to the device by the bonding process was confirmed. In this paper, we report on various possible application of the TLP bonding.

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Low Temperature Wafer Level Bonding Using Benzocyclobutene Adhesive Polymers

Additional Conferences (Device Packaging HiTEC HiTEN & CICMT) ◽

10.4071/2012dpc-wp13 ◽

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.

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Low Temperature Direct Cu-Cu Immersion Bonding for 3D Integration

MRS Proceedings ◽

10.1557/proc-1156-d08-02-f06-02 ◽

2009 ◽

Vol 1156 ◽

Cited By ~ 1

Author(s):

Rahul Agarwal ◽

Wouter Ruythooren

Keyword(s):

Citric Acid ◽

Low Temperature ◽

Bonding Temperature ◽

Atmospheric Condition ◽

High Strength ◽

Bonding Process ◽

3D Integration ◽

Temperature And Pressure ◽

Low Temperature Bonding

AbstractHigh yielding and high strength Cu-Cu thermo-compression bonds have been obtained at temperatures as low as 175°C. Plated Cu bumps are used for bonding, without any surface planarization step or plasma treatment, and bonding is performed at atmospheric condition. In this work the 25μm diameter bumps are used at a bump pitch of 100μm and 40μm. Low temperature bonding is achieved by using immersion bonding in citric acid. Citric acid provides in-situ cleaning of the Cu surface during the bonding process. The daisy chain electrical bonding yield ranges from 84%-100% depending on the bonding temperature and pressure.

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Low temperature and deformation-free bonding of PMMA microfluidic devices with stable hydrophilicity via oxygen plasma treatment and PVA coating

RSC Advances ◽

10.1039/c4ra12771d ◽

2015 ◽

Vol 5 (11) ◽

pp. 8377-8388 ◽

Cited By ~ 37

Author(s):

H. Yu ◽

Z. Z. Chong ◽

S. B. Tor ◽

E. Liu ◽

N. H. Loh

Keyword(s):

Low Temperature ◽

Plasma Treatment ◽

Oxygen Plasma ◽

Microfluidic Devices ◽

Oxygen Plasma Treatment ◽

Bonding Method

A deformation-free bonding method with stable hydrophilicity in PMMA devices has been proposed through oxygen plasma treatment and PVA coating.

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Low Temperature Anodic Bonding for MEMS Applications

Electronic and Photonic Packaging, Electrical Systems Design and Photonics, and Nanotechnology ◽

10.1115/imece2002-39272 ◽

2002 ◽

Cited By ~ 4

Author(s):

J. Wei ◽

Z. P. Wang ◽

L. Wang ◽

G. Y. Li ◽

Z. Q. Mo

Keyword(s):

Low Temperature ◽

Bonding Strength ◽

Transition Period ◽

Bonding Temperature ◽

Testing Machine ◽

Acoustic Microscopy ◽

Anodic Bonding ◽

Dominant Factor ◽

Glass Wafer ◽

Bonding Parameters

In this paper, anodic bonding between silicon wafer and glass wafer (Pyrex 7740) has been successfully achieved at low temperature. The bonding strength is measured using a tensile testing machine. The interfaces are examined and analyzed by scanning acoustic microscopy (SAM), scanning electron microscopy (SEM) and secondary ion mass spectrometry (SIMS). Prior to bonding, the wafers are cleaned in RCA solutions, and the surfaces become hydrophilic. The effects of the bonding parameters, such as bonding temperature, voltage, bonding time and vacuum condition, on bonding quality are investigated using Taguchi method, and the feasibility of bonding silicon and glass wafers at low temperature is explored. The bonding temperature used ranges from 200 °C to 300 °C. The sensitivity of the bonding parameters is analyzed and it is found that the bonding temperature is the dominant factor for the bonding process. Therefore, the effects of bonding temperature are investigated in detail. High temperatures cause high ion mobility and bonding current density, resulting in the short transition period to the equilibrium state. Almost bubble-free interfaces have been obtained. The bonded area increases with increasing the bonding temperature. The unbonded area is less than 1.5% within the whole wafer for bonding temperature between 200 °C to 300 °C. The bonding strength is higher than 10 MPa, and increases with the bonding temperature. Fracture mainly occurs inside the glass wafer other than in the interface when the bonding temperature is higher than 225 °C. SIMS results show that the chemical bonds of Si-O form in the interface. Higher bonding temperature results in more oxygen migration to the interface and more Si-O bonds. The bonding mechanisms consist of hydrogen bonding and Si-O chemical reaction.

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