Electrolytic microfabrication

Electrolytic microfabrication

Contact :

Laurent ROBERT
TEMIS Sciences building – Office N1-21
03 81 66 66 47 (Office)
laurent.robert@femto-st.fr

Tristan FAURE
Bâtiment TEMIS Sciences – Bureau RC-LAB-24
03 63 08 26 56 (Bureau)
tristan.faure@femto-st.fr

Location :

TEMIS cleanroom
Area Chemistry / Electroplating

Industrial Nickel electroplating machine 4 inch wafers

Technical characteristics :

- Substrate: 4 inch metallic or metallized wafer with (electrical connection located at the rim with 3 mm of exclusion)
- Type of deposit: matt Nickel
- Electrolyte composition:
o Nickel: 89 g/L
o Boric acid: 55g/L
- Electrolyte temperature: 52 °C
- pH: 3.6 - 3.8
- Volume: 100 L au total
o Working cell: 20 L
o Reservoir: 80 L
- speed of growth: up to 100µm/h with a current density of 10A/dm² maximum
- Nickel thickness: limited by the thickness of the photoresist (typically several tens of microns)
- Stirring: pump (13 l/min) which threw the electrolyte towards the surface of the substrate through a diffuser to for a better uniformity
- substrate rotation: 60 rpm
- selective cleaning in the reservoir to avoid metallic impurities

General machine description :

Measured characteristics of Electroplating Nickel :

- Roughness (Rt) : 1 à 2 µm
- Intrinsic stresses : from +30 to +40 MPa

Nickel bath in a homemade tank

Technical characteristics :

- Substrate: metallic or metallized wafer
- Type of deposit: matt nickel
- Electrolyte temperature: 50 °C
- Plating speed: several µm/h to several tens of µm/h
- Thickness: limited by the thickness of the photoresist (typically several tens of microns)


Measured properties of the electroforming Nickel :

- Young modulus: 200 GPa
- Hardness: 300 à 600 Hv
- Yield strength: 300 MPa
- Roughness (Rt) : 0,8 to 1,2 µm
- Intrinsic stress:
o from -30 to 20 MPa on Cu
o from 140 to 220 MPa on Si

Achieved results :

Gold Cobalt bath in beaker

Technical characteristics :

- Substrate: metallic or metallized wafer (4 inch max)
- Type of deposit : matt acid gold
- Electrolyte composition:
o Gold: 15 g/L
o Cobalt: 0.3 g/L
- Electrolyte temperature: 55 °C
- pH: 4 - 4.1
- Electrolyte volume: 2 liters
- speed of growth : up to 12 µm/h
- Stirring: mechanical