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ELECTROPLATING
The electroplating area deals with 2 technologies: wet anisotropic etching and electroplating of metals.
Wet anisotropic etching
The wet anisotropic etching is used for silicon micromachining: the etch thickness varying from some microns to several hundred microns.
The alkaline solutions attack silicon preferentially in the <100> plane, producing a characteristic anisotropic V-etch, with sidewalls that form a 54.7° angle with the surface (35.3° from the normal).
The KOH etch requires a “hard mask” of silicon dioxide or silicon nitride (nitride is preferred since oxide is slowly etched by KOH).
Electroplating of metals
In the electroplating process the substrate is placed in a liquid solution (electrolyte). When an electrical potential is applied between a conducting area on the substrate and a counter electrode (usually platinum) in the liquid, a chemical red-ox process takes place resulting in the formation of a layer of material on the substrate and usually some gas generation at the counter electrode. This process is also known as "electroplating" and is typically restricted to electrically conductive materials. We can plate in the entire wafer or in resist molds from several microns to several hundred microns.
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KOH etching (free access)
TMAH etching (free access)
Laboratory reactor for Au plating
Laboratory reactor for Cu plating
Laboratory reactor for Co, Fe, Ni plating
Laboratory reactor for Pb plating
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| Industrial reactor for Au plating |
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| Industrial reactor for Cu plating |
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Industrial reactor for FE, Ni, Co plating
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Polarography, CVS, Titration for control of plating solutions
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| Know-how : |
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Anisotropic wet etching :
KOH etching:
The etching speed depends on KOH concentration (from 20 to 50 % weight) and temperature (from 50 à 90°) and varies from 0.5 to 2.5 µm /min.
TMAH etching:
The etching speed depends on TMAH concentration (from 20 to 50 % weight) and temperature (from 50 à 90°) and varies from 0.2 to 1 µm /min.
This chemistry doesn’t etch the silicon dioxide, so silicon dioxide can be used as mask
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Realisation of a hole by KOH
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Influence of IPA on the etching
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TMAH 20% - 2 min
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| TMAH 20% + 17 % IPA - 2 min |
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Electro plating of metals
Gold plating : Gold electroplating with continuous current on full wafer or on photoresist moulds for thickness until dozen microns.
 
RF-MEMS
Copper Plating :Copper electroplating with continuous or pulsed current on full wafer or on photoresist moulds for thickness until hundred microns
Micro convertiseurs d'énergie
Co-Ni-Fe plating : NiCoFe electroplating with continuous current on full wafer or on photoresist moulds for thickness until several dozen microns.
Micro –Transformers for power components
Lead plating :
Lead electroplating with continuous current on full wafer or on photoresist moulds for thickness until several dozen microns.
Gold electroless in order to protect copper
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