Application of Porous Silicon to Bulk Silicon Micromachining

1996 ◽  
Vol 459 ◽  
Author(s):  
G. Kaltsas ◽  
A. G. Nassiopoulos
Keyword(s):  
Porous Silicon ◽  
Smooth Surface ◽  
Sacrificial Layer ◽  
Monocrystalline Silicon ◽  
Back Side ◽  
Bulk Silicon ◽  
Free Standing ◽  
Integrated Devices ◽  
Silicon Micromachining ◽  
Deep Cavities

ABSTRACTA fully C-MOS compatible process for bulk silicon micromachining using porous silicon technology and front-side lithography is developed. The process is based on the use of porous silicon as a sacrificial layer for the fabrication of deep cavities into monocrystalline silicon, so as to avoid back side lithography. Cavities as deep as several hundreds of micrometers are produced with very smooth surface and sidewalls. The process is used to produce : a) suspended monocrystalline silicon membranes, b) free standing polysilicon membranes in the form of bridges or cantilevers with lateral dimensions from a few μms to several hundreds of μms. Important applications to silicon integrated devices as sensors, actuators, detectors etc., are foreseen.

Porous Silicon as a Sacrificial Material for Microstructures Fabrication

1999 ◽  
Vol 605 ◽  
Author(s):  
M. Morel ◽  
M. Le Berre ◽  
V. Lysenko ◽  
G. Delhomme ◽  
A. Dittmar ◽  
...  
Keyword(s):  
Porous Silicon ◽  
Electrochemical Etching ◽  
Sacrificial Layer ◽  
Formation Rate ◽  
Free Standing ◽  
Wide Range ◽  
Silicon Bulk ◽  
Reduced Costs ◽  
Optimized Conditions ◽  
Koh Etching

AbstractPorous silicon (PS) is generated by electrochemical etching in hydrofluoric acid (HF). Recently porous silicon has been applied to micromachining and micro-devices as an alternate material, this material being used as a sacrificial layer. This technology competes with conventional techniques like surface and bulk micromachining regarding its speed, simplicity and reduced costs. A wide range of microstructures and free-standing structures can be fabricated with a large freedom of design in relation to the isotropic behavior of the etching. A sacrificial layer may be realized fast over varying thickness (PS formation rate 45 μm/h compared to silicon bulk micromachining rate 20 μm/h for KOH etching).This contribution is devoted to the materials aspects of patterning and processing: we will show how basic microstructures (trenches, polysilicon cantilevers, polysilicon free-standing membranes) may be fabricated using a very simple process based on a single photolithography. The important points are the choice of the mask, porous silicon properties as a function of its formation parameters and the choice of the solution removing the sacrificial layer. The morphology and porosity of the porous silicon layers are indeed mainly determined by the electrolyte composition and by the current density for a given substrate type. Optimized conditions (HF 15% and 80 mA/cm2) lead us to an appropriate porous silicon. Finally the applicability of this technology for various microsensors will be underlined.

Surface Micromachining of Polyureasilazane Based Ceramic-MEMS Using SU-8 Micromolds

2006 ◽  
Vol 45 ◽  
pp. 1293-1298 ◽  
Author(s):  
Vahid Fakhfouri ◽  
Sébastien Jiguet ◽  
Juergen Brugger
Keyword(s):  
Thermogravimetric Analysis ◽  
Aspect Ratio ◽  
Material Characterization ◽  
Smooth Surface ◽  
Sacrificial Layer ◽  
Green Body ◽  
Mems Devices ◽  
Surface Micromachining ◽  
Free Standing ◽  
Liquid Precursor

We describe a novel surface micromachining process for the fabrication of ceramic-type MEMS devices, such as free-standing cantilevers, that is based on the use of high-aspect ratio micromolds of SU8 and aluminum as sacrificial layer. 250μm-high and 100-1000μm-wide molds were used to confine a liquid precursor of SiC/Si3N4 based ceramics on the sacrificial layer that enables the detachment of the green body before the pyrolysis step at 1000°C. The final ceramic cantilever has dimensions ranging from 100-500μm x 1-2mm x 50μm and a smooth surface. Details of the processing, structural and material characterization such as Dynamic Rheological and Thermogravimetric Analysis under UV will be presented and compared to those found in the literature.

Strongly Superlinear Light Emission and Large Induced Absorption in Oxidized Porous Silicon Films

1998 ◽  
Vol 536 ◽  
Author(s):  
H. Koyama ◽  
P. M. Fauchet
Keyword(s):  
Porous Silicon ◽  
Thermal Effects ◽  
Light Emission ◽  
Laser Intensity ◽  
Excitation Intensity ◽  
Silicon Films ◽  
Free Standing ◽  
Induced Absorption ◽  
Cw Laser ◽  
Oxidized Porous Silicon

AbstractThe optical properties of oxidized free-standing porous silicon films excited by a cw laser have been investigated. It is found that samples oxidized at 800–950 °C show a strongly superlinear light emission at an excitation intensity of ∼10 W/cm2. This emission has a peak at 900–1100 nm and shows a blueshift as the oxidation temperature is increased. These samples also show a very large induced absorption, where the transmittance is found to decrease reversibly by ≤99.7 %.The induced absorption increases linearly with increasing pump laser intensity. Both the superlinear emission and the large induced absorption are quenched when the samples are attached to materials with a higher thermal conductivity, suggesting that laser-induced thermal effects are responsible for these phenomena.

Stabilization of Porous Silicon Free-Standing Coupled Optical Microcavities by Surface Chemical Modification

2019 ◽  
Vol 16 (3) ◽  
pp. 211-219 ◽  
Author(s):  
Bernard Gelloz ◽  
Kouichiro Murata ◽  
Toshiyuki Ohta ◽  
Mher Ghulinyan ◽  
Lorenzo Pavesi ◽  
...  
Keyword(s):  
Porous Silicon ◽  
Chemical Modification ◽  
Surface Chemical ◽  
Free Standing ◽  
Optical Microcavities ◽  
Surface Chemical Modification
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