A novel polysilicon based process for three terminal surface micromachined cantilever
01 Dec 2007-pp 733-736
TL;DR: In this article, a three terminal cantilever beam can be used as a switch and also for material and process characterization, and the problems encountered in each step of fabrication and possible solutions are discussed in detail.
Abstract: A three terminal cantilever beam can be used as a switch and also for material and process characterization. This paper deals with process optimization for its fabrication with surface micromachining steps compatible with standard integrated circuit manufacturing technology. The problems encountered in each step of fabrication and possible solutions are discussed in detail. The process makes extensive use of polysilicon deposited by Low Pressure Chemical Vapour Deposition for contacts, sacrificial oxide as well as the structural layer.
References
More filters
TL;DR: In this paper, an overview of the materials available in integrated circuit manufacturing is given, and the etch mechanism and sacrificial layer etch kinetics are reviewed, and selectivity issues important for the proper choice of layers and etchants are addressed.
Abstract: Silicon dioxide sacrificial layer etching has become a major surface micromachining method to fabricate microsensors and microactuators often made of polycrystalline silicon. An overview of the materials available in integrated circuit manufacturing is given, and the etch mechanism and sacrificial layer etch kinetics are reviewed. Selectivity issues important for the proper choice of layers and etchants are addressed discussing the chemical attack of aluminum during long sacrificial layer etching, as an example. Various etchants known from other studies are compared: concentrated and dilute HF, buffered HF (BHF), nitric acid based etchants known as P-etch, R-etch, S-etch, as well as mixtures of HF and HCl, and vapor HF. `Pad-etch', an acetic acid/ammonium fluoride/ethyleneglycole solution is shown to have an enhanced selectivity against aluminum. Some device examples such as arrays of deflectable micromirrors demonstrate the versatile application of sacrificial oxide etching in surface micromachining.
178 citations
07 Feb 1993
TL;DR: In this article, a fabrication process that eliminates the adhesion of surface-micromachined suspended mechanical structures to the underlying substrate during a sacrificial-etch release is presented, based on the construction of a periodic array of polymer columns or rubber feet that stiffen the structure during the sacrificial etch.
Abstract: A fabrication process that eliminates the adhesion of surface-micromachined suspended mechanical structures to the underlying substrate during a sacrificial-etch release is presented. The method is based on the construction of a periodic array of polymer columns or rubber feet that stiffen the structure during the sacrificial etch. Flat polycrystalline silicon plates measuring 3000*3000*1- mu m suspended 1 mu m above the substrate are easily fabricated by this method. This process has applications in the fabrication of micromachined plates used in devices such as accelerometers and pressure sensors. >
93 citations
TL;DR: In this article, hot-wire a-SiNx:H thin-film transistors have been applied to thin-filament transistors with an ammonia/silane gas-flow ratio of R=30.
Abstract: Hot-wire chemical vapor deposition (HWCVD) is a promising technique for the deposition of silicon nitride layers (a-SiNx:H) at low temperatures. In contrast to the commonly used plasma-enhanced chemical vapor deposition, no ion bombardment is present in HWCVD, which makes it particularly attractive for the deposition of passivation layers on structures that are sensitive to the impact of energetic ions. We deposit hot-wire a-SiNx:H from a mixture of silane and ammonia at substrate temperatures in the range of 300–500 °C. Layers deposited with an ammonia/silane gas-flow ratio of R=30 are close to stoichiometry (N/Si=1.33) with a hydrogen content around 10 at. %. Such films have been implemented in hot-wire a-Si:H thin-film transistors. Deposition with R>30 did not result in an increase of the N content, but led to more porous films. Infrared spectroscopy revealed that moisture penetrates these layers and that oxygen is incorporated in the network under air exposure. Cross-sectional transmission electron mi...
63 citations
TL;DR: In this article, a series of thermal cycling experiments were conducted with various types of oxide and nitride films to elucidate the control mechanism of intrinsic stress generation and to develop engineering solutions for improving reliability of microelectromechanical system fabrication processes.
57 citations
TL;DR: In this article, the authors estimate the stiction force from electrical measurements on surface micromachined polysilicon cantilever beams in terms of the pull-in and pull-out voltages.
Abstract: In this paper, we estimate the stiction force from electrical (current-voltage) measurements on surface micromachined polysilicon cantilever beams A bias voltage was applied between the beam and the substrate At the pull-in voltage, the beam collapsed to the substrate and the current rose rapidly from zero Similarly, at the pull-out voltage during bias sweep back, the current dropped rapidly to zero when the contact between the beam and the substrate was broken An analytic model for the stiction force was developed in terms of the pull-in and pull-out voltages and was used to estimate a stiction force of about 70 nN from the measured electrical characteristics This method of characterization is suitable for use in packaged devices An analytic model was developed to estimate stiction force from optical surface-profile measurements of the curvature of long collapsed cantilever beams in a cantilever-beam array, in the absence of any electrostatic actuation The force per unit length of about 14 nN/m thus obtained was used to compare the effects of surface roughness on stiction
31 citations
"A novel polysilicon based process f..." refers background or methods in this paper
...Recently, a model has been proposed which allows the determination of stiction force from measured quantities alone and has been used for two terminal cantilever beams [ 3 ]....
[...]
...Table1 shows pull-in and pull-out voltages [ 3 ] for different beam lengths and pull in characteristics of a 360 μm long released beam is shown in figure 7....
[...]