PECVD silicon nitride diaphragms for condenser microphones

Scheeper, P.R.; Voorthuyzen, J.A.; Bergveld, Piet

doi:10.1016/0925-4005(91)80180-r

Cited by 24 publications

(16 citation statements)

References 11 publications

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“…The film is irreversibly modified by annealing process and following heating at lower temperature don't cause other changes. Annealing at T>600°C causes the hydrogen desorption [17], whose presence degrades the mechanical properties of the film. With FTIR spectroscopy we observed a strong reduction of hydrogen content in annealed films.…”

Section: Analysis Of Silicon Mtride Film Stressmentioning

confidence: 99%

“…The classical gain-bandwidth trade-off is experienced by this acoustical device; cMUT transducers try to overcome this trade-off reducing the lateral dimension up to about 10 tm in order to reach high frequencies (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20), and using a large array of such micro capacitive microphones (some thousands) in order to obtain a reasonable sensitivity. Fig.…”

Section: Introductionmentioning

confidence: 99%

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<title>Development of silicon ultrasonic transducer using micromachining</title>

Caliano

Galanello

Foglietti³

et al. 2000

Micromachined Devices and Components VI

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Ultrasonic transducers are generally based on the piezoelectric effect and they are used in a variety of applications (medical imaging, NDE, ranging). Some of the main reasons for choosing an alternative technology, based on electrostatic effect, are low impedance mismatch with air and in water, low energy density, high efficiency, low costs, good integration with control electronics. Capacitive ultrasonic transducer consists in a parallel plates capacitor (like a condenser microphone) with a fixed electrode and a free one (membrane). A cMUT (capacitive Micromachined Ultrasonic Transducer) consists of an array of capacitive ultrasonic transducer with metallized membranes suspended on silicon bulk. The membrane thickness is 0.4 sum. Tests of these transducers ( @ 2.5 MHz) fabricated in our laboratories are in progress.

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Section: Analysis Of Silicon Mtride Film Stressmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

<title>Development of silicon ultrasonic transducer using micromachining</title>

Caliano

Galanello

Foglietti³

et al. 2000

Micromachined Devices and Components VI

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“…Also, it is easy to control stress in PECVD nitride by changing process parameters such as temperature and pressure. 13,14 Therefore, PECVD nitride is chosen structural material. A 500nm thick PECVD nitride is deposited on top of patterned polyimide and etched to form support beams (see one example of patterned support beams in Fig.2).…”

Section: Building the Foundation Layer And The First Sacrificial Layermentioning

confidence: 99%

Fabrication of adaptive microbolometers

Song

Talghader

2004

SPIE Proceedings

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In this paper, the fabrication of microbolometers with electronically controllable responsivity is presented. The first generation devices are built in a standard polysilicon-based micromachining process with HF etch-release and demonstrated with a responsivity that can be tuned over a factor of 50. The responsivity is controlled by applying a voltage between the microbolometer and the substrate. The resulting electrostatic force causes a small portion of the support beam to contact the substrate, which thermally shorts the device at that point. The thermal contact points are defined using curved support beams with residual-stress from a Cr/Au metallization. The lowest portion of the beams contacts the substrate, and the curvature protects the device from full "snapdown," which might induce stiction. The fabrication of the second generation microbolometers based on V O x and silicon nitride materials with a polyimide etch-release is also described. The thermal contact points for these devices are defined by beam mechanics rather than by beam curvature induced by stress, and they actuate at 17 volts. The test array has a fill-factor of 91% for a pixel period of 140µm limited by our photolithography equipment.

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“…This equation has been rewritten so that it can be seen that the second term between the brackets represents the stress that is caused by stretching of the middle plane of the diaphragm. Equation (l), the pressure-deflection curve for a flat diaphragm without initial stress, can be rewritten in a similar way as (7). The second term between the brackets is then exactly the same as in (7) and also represents the stress that is caused by stretching of the middle plane of the diaphragm.…”

Section: The Mechanical Sensitivitymentioning

confidence: 99%

“…The tensile stress in thin silicon nitride films is typically of the order of lo8 N/m2 [7]. The stress in silicon diaphragms is determined by the diaphragm fabrication process.…”

Section: Introductionmentioning

confidence: 99%

The design, fabrication, and testing of corrugated silicon nitride diaphragms

Scheeper

Olthuis

Bergveld

1994

J. Microelectromech. Syst.

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122

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Silicon nitride corrugated diaphragms of 2 mm x 2 mm x l p m have been fabricated with 8 circular corrugations, having depths of 4 1 0 , or 14 pm. The diaphragms with 4-pm-deep corrugations show a measured mechanical sensitivity (increase in the deflection over the increase in the applied pressure) which is 25 times larger than the mechanical sensitivity of flat diaphragms of equal size and thickness. Since this gain in sensitivity is due to reduction of the initial stress, the sensitivity can only increase in the case of diaphragms with initial stress. A simple analytical model has been proposed that takes the influence of initial tensile stress into account. The model predicts that the presence of corrugations increases the sensitivity of the diaphragms, because the initial diaphragm stress is reduced. The model also predicts that for corrugations with a larger depth the sensitivity decreases, because the bending stiffness of the corrugations then becomes dominant. These predictions have been confirmed by experiments. The application of corrugated diaphragms offers the possibility to control the sensitivity of thin diaphragms by geometrical parameters, thus eliminating the effect of variations in the initial stress, due to variations in the diaphragm deposition process andlor the influence of temperature changes and packaging stress.

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PECVD silicon nitride diaphragms for condenser microphones

Cited by 24 publications

References 11 publications

<title>Development of silicon ultrasonic transducer using micromachining</title>

<title>Development of silicon ultrasonic transducer using micromachining</title>

Fabrication of adaptive microbolometers

The design, fabrication, and testing of corrugated silicon nitride diaphragms

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