Change search
ReferencesLink to record
Permanent link

Direct link
Sealing of adhesive bonded devices on wafer level
KTH, Superseded Departments, Signals, Sensors and Systems.
2004 (English)In: Sensors and Actuators A-Physical, ISSN 0924-4247, Vol. 110, no 1-3, 407-412 p.Article in journal (Refereed) Published
Abstract [en]

In this paper. we present a low temperature wafer-level encapsulation technique to hermetically seal adhesive bonded microsystem structures by cladding the adhesive with an additional diffusion barrier. Two wafers containing cavities for MEMS devices were bonded together using benzocyclobutene (BCB). The devices were sealed by a combined dicing and self-aligning etching technique and by finally coating the structures with evaporated gold or PECVD silicon nitride. The sealing layer was inspected visually by SEM and helium leak tests were carried out. Devices sealed with silicon nitride and with known damage of the sealing layer showed a helium leak rate of about 7-14 times higher than the background level. Devices of the same size without damage in the sealing layer had a leak rate of only 1.5 times higher than the background level. Experiments with evaporated gold as cladding layer revealed leaking cracks in the film even up to a gold thickness of 5 mum. The sealing technique with silicon nitride shows a significant improvement of the hermeticity properties of adhesive bonded cavities, making this bonding technique suitable for applications with certain demands on gas-tightness.

Place, publisher, year, edition, pages
2004. Vol. 110, no 1-3, 407-412 p.
Keyword [en]
hermetic sealing, wafer-level encapsulation, adhesive bonding, benzocyclobutene, fabrication, cavities, mems
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
URN: urn:nbn:se:kth:diva-13415DOI: 10.1016/j.sna.2003.06.003ISI: 000188700700064ScopusID: 2-s2.0-1642566508OAI: diva2:325198
QC 20100617Available from: 2010-06-17 Created: 2010-06-17 Last updated: 2011-10-31Bibliographically approved
In thesis
1. Novel RF MEMS Switch and Packaging Concepts
Open this publication in new window or tab >>Novel RF MEMS Switch and Packaging Concepts
2004 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Radio-frequency microelectromechanical systems (RF~MEMS) are highly miniaturized devices intended to switch, modulate, filter or tune electrical signals from DC to microwave frequencies. The micromachining techniques used to fabricate these components are based on the standard clean-room manufacturing processes for high-volume integrated semiconductor circuits. RF~MEMS switches are characterized by their high isolation, low insertion loss, large bandwidth and by their unparalleled signal linearity. They are relatively simple to control, are very small and have almost zero power consumption. Despite these benefits, RF~MEMS switches are not yet seen in commercial products because of reliability issues, limits in signal power handling and questions in packaging and integration. Also, the actuation voltages are typically too high for electronics applications and require additional drive circuitry.

This thesis presents a novel MEMS switch concept based on an S-shaped film actuator, which consists of a thin and flexible membrane rolling between a top and a bottom electrode. The special design makes it possible to have high RF isolation due to the large contact distance in the off-state, while maintaining low operation voltages due to the zipper-like movement of the electrostatic dual-actuator. The switch comprises two separately fabricated parts which allows simple integration even with RF circuits incompatible with certain MEMS fabrication processes. The two parts are assembled by chip or wafer bonding which results in an encapsulated, ready-to-dice package. The thesis discusses the concept of the switch and reports on the successful fabrication and evaluation of prototype devices.

Furthermore, this thesis presents research results in wafer-level packaging of (RF) MEMS devices by full-wafer bonding with an adhesive intermediate layer, which is structured before bonding to create defined cavities for housing MEMS devices. This technique has the advantage of simple, robust and low temperature fabrication, and is highly tolerant to surface non-uniformities and particles in the bonding interface. It allows cavities with a height of up to many tens of micrometers to be created directly in the bonding interface. In contrast to conventional wafer-level packaging methods with individual chip-capping, the encapsulation is done using a single wafer-bonding step. The thesis investigates the process parameters for patterned adhesive wafer bonding with benzocyclobutene, describes the fabrication of glass lid packages based on this technique, and introduces a method to create through-wafer electrical interconnections in glass substrates by a two-step etch technique, involving powder-blasting and chemical etching. Also, it discusses a technique of improving the hermetic properties of adhesive bonded structures by additional passivation layers. Finally, it presents a method to substantially improve the bond strength of patterned adhesive bonding by using the solid/liquid phase combination of a patterned polymer layer with a contact-printed thin adhesive film.

Place, publisher, year, edition, pages
Stockholm: KTH, 2004. xii, 142 p.
Trita-ILA, ISSN 0281-2878 ; 0401
0-level packaging, adhesive bonding, BCB, benzocyclobutene, bond strength, contact printing, film actuator, glass lid encapsulation, glass lid packaging, helium leak test, hermetic packaging, hermeticity, high isolation switch, low stress silicon nitride, low volt
National Category
Engineering and Technology
urn:nbn:se:kth:diva-3817 (URN)91-7283-831-0 (ISBN)
Public defence
2004-09-10, 00:00
QC 20100617Available from: 2004-08-26 Created: 2004-08-26 Last updated: 2010-06-18Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textScopus

Search in DiVA

By author/editor
Oberhammer, JoachimNiklaus, FrankStemme, Göran
By organisation
Signals, Sensors and Systems
In the same journal
Sensors and Actuators A-Physical
Electrical Engineering, Electronic Engineering, Information Engineering

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 195 hits
ReferencesLink to record
Permanent link

Direct link