Wafer Scale Packaging of MEMS by Using Plasma-Activated Wafer Bonding

Suni, Tommi; Henttinen, Kimmo; Lipsanen, Antti; Dekker, J.; Luoto, Hannu; Kulawski, Martin

doi:10.1149/1.2135209

Cited by 23 publications

(17 citation statements)

References 4 publications

(6 reference statements)

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“…The degassing issue seems to be significant for silicon oxide deposited by techniques such as PECVD and LPCVD but not for thermally grown oxide [15]. It has been demonstrated that patterned films can produce void-free bonds, even without densification, because grooves provide escape paths for gases produced during the bond-annealing step [16]- [19].…”

Section: Film Densificationmentioning

confidence: 99%

The Nanoaquarium: A Platform for In Situ Transmission Electron Microscopy in Liquid Media

Grogan

Bau

2010

J. Microelectromech. Syst.

125

123

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Transmission electron microscopes (TEMs) and scanning transmission electron microscopes (STEMs) are powerful tools for imaging on the nanoscale. These microscopes cannot be typically used to image processes taking place in liquid media because liquid simply evaporates in the high-vacuum environment of the microscope. In order to view a liquid sample, it is thus necessary to confine the liquid in a sealed vessel to prevent evaporation. Additionally, the liquid layer must be very thin to minimize electron scattering by the suspending medium. To address these issues, we have developed a flow cell with a height of tens of nanometers, sandwiched between two thin silicon nitride membranes. The cell is equipped with electrodes for actuation and sensing. The cell is thin enough to allow the transmission of electrons and the real-time imaging of nanoparticles suspended in liquid. This paper details the fabrication process, which relies on plasma-activated wafer bonding. Some of the advantages of our nanoaquarium include the thinnest observation chamber of any reported in situ TEM/STEM device, integrated electrodes for sensing and actuation, and wafer-scale processing that allows bulk device production. Device performance was demonstrated by STEM imaging of gold and polystyrene nanoparticles suspended in water with excellent resolution. Potential applications of the device include imaging of colloidal crystal formation, aggregation, nanowire growth, electrochemical deposition, and biological interactions.[ 2010-0023]Index Terms-Electron microscopy, fluidics, in situ, nanotechnology, wafer bonding.

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Section: Film Densificationmentioning

confidence: 99%

The Nanoaquarium: A Platform for In Situ Transmission Electron Microscopy in Liquid Media

Grogan

Bau

2010

J. Microelectromech. Syst.

125

123

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“…It refers to the technology of packaging a sensor or an integrated circuit at wafer level [2], instead of chip scale packaging, the process of assembling the package of each individual unit after wafer dicing. WLP can offer reduction in cost, give high throughput and increased reliability by high-quality front-end sealing.…”

Section: Introductionmentioning

confidence: 99%

Al-Al thermocompression bonding for wafer-level MEMS packaging

Malik¹,

Schjølberg-Henriksen²,

Poppe³

et al. 2013

2013 Transducers &Amp; Eurosensors XXVII: The 17th International Conference on Solid-State Sensors, Actuators and Microsystems

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The Al-Al thermocompression bonding is studied on test structures suitable for wafer level packaging of MEMS devices. Si wafers with protruding frame structures have been bonded to planar Si wafers all covered with a 1 µm sputtered Al film. The varied bonding process variables were temperature (400 °C-550 °C), bonding force (18-36 kN) and frame widths (100 µm, 200 µm, rounded or sharp corners). The delamination caused by dicing and pull tests is systematically studied. It is concluded that bonding is incomplete at 400 °C, with a low dicing yield. The quality of the bonding is increased by increasing bonding temperature and force as expected. The fractured surfaces and the bonding strength have been studied in detail. The test structures showed an average strength of 20-50 MPa for bonding at or above 450 °C. The current study indicates that strong Al-Al thermocompression bonds can be achieved at or above 450 °C for a typical MEMS bond frame.

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“…(a) First, the wafer was thermally oxidized to a thickness of 500 nm or 1 lm as electrical insulation and diffusion barrier between Pt and Si; (b) Pt thin film was sputtered directly on the substrate up to a thickness of 1 lm without adhesion layers (Käpplinger et al 2007); (c) the wafer was coated by photoresist and structured by photolithography; (d) about 900 nm of Pt was etched through ion beam etching (with a tilt of 20°to enhance the etching rate); (e) the residual Pt was etched in aqua regia (to avoid trench formation and possible short cut between Pt and Si); (f) optionally the wafer was coated with CVD-SiO 2 and CMP planarized to allow the direct wafer bonding (Jia et al 2006;Suni et al 2006); (g) the wafer was diced into single chips; (h) five holes were bored into the chip. Optionally the chip was thermally insulated through laser ablation; (i) when coated with CVD-SiO 2 , the coating layer covering the contact pads was removed with local HF-etching.…”

Section: Fabricationmentioning

confidence: 99%

“…3.3). In the future, the established fabrication process will be extended with direct wafer bonding as assembling method (Jia et al 2006;Suni et al 2006). …”

Section: Fabricationmentioning

confidence: 99%

MEMS-based microthruster with integrated platinum thin film resistance temperature detector (RTD), heater meander and thermal insulation for operation up to 1,000°C

Miyakawa¹,

Legner²,

Ziemann³

et al. 2012

Microsyst Technol

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We have fabricated microthruster chip pairs-one chip with microthruster structures such as injection capillaries, combustion chamber and converging/diverging nozzle machined using the deep reactive ion etching process, the other chip with sputtered platinum (Pt) thin film devices such as resistance temperature detectors (RTDs) and a heater. To our knowledge, this is the first microelectromechanical systems-based microthruster with fully integrated temperature sensors. The effects of anneal up to 1,050°C on the surface morphology of Pt thin films with varied geometry as well as with/without PECVD-SiO 2 coating were investigated in air and N 2 and results will also be presented. It was observed that by reducing the lateral scale of thin films the morphology change can be suppressed and their adhesion on the substrate can be enhanced. Chemical analysis with X-ray photoelectron spectroscopy showed that no diffusion took place between neighboring layers during annealing up to 1 h at 1,050°C in air. Electrical characterization of sensors was carried out between room temperature and 1,000°C with a ramp of ±5 Kmin -1 in air and N 2 . In N 2 , the temperature-resistance characteristics of sensors had stabilized to a large extent after the first heating. After stabilization the sensors underwent up to eight further temperature cycles. The maximum drift of the sensor signal was observed for temperatures above 950°C and was less than 8.5 K in N 2 . To reduce the loss of combustion heat, chip material around microthruster structures was partially removed with laser ablation. The effects of thermal insulation were investigated with microthruster chip pairs which were clamped together mechanically. The heater was operated with up to 20 W and the temperature distribution in the chip pairs with/without thermal insulation was monitored with seven integrated RTDs. The experiments showed that a thermal insulation allows the maximum temperature as well as the temperature gradient within the microthruster chip pairs to be increased.

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Wafer Scale Packaging of MEMS by Using Plasma-Activated Wafer Bonding

Cited by 23 publications

References 4 publications

The Nanoaquarium: A Platform for In Situ Transmission Electron Microscopy in Liquid Media

The Nanoaquarium: A Platform for In Situ Transmission Electron Microscopy in Liquid Media

Al-Al thermocompression bonding for wafer-level MEMS packaging

MEMS-based microthruster with integrated platinum thin film resistance temperature detector (RTD), heater meander and thermal insulation for operation up to 1,000°C

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