Fraunhofer Institute for Electronic Nano Systems
Fraunhofer Institute for Electronic Nano Systems

Electrochemical Deposition

Stack of Palladium-Tin consisting of 40 Bi-Layers

© Fraunhofer ENAS

Electrochemical Deposition

Wirebonds onto electoplated aluminum

© Fraunhofer ENAS

Electrochemical Deposition

Focused Ion Beam cut through AuSn Bi-Layer

© Fraunhofer ENAS

Research Field Electrochemical Deposition

Separation of special materials

The department System Packaging investigates the electrochemical metal deposition (ECD) for the fabrication of intermediate bonding layers regarding wafer und chip bonding processes. For instance, the SLID bonding can be carried out with numerous metal combinations, which can be produced by ECD. These include Cu-Sn, Au-Sn, Cu-In, Au-In, Cu-Ga or Ni-Sn. Every combination shows different properties in terms of bonding temperature, stability of the intermetallic compound (IMC) against environmental impacts and re-melt temperature of the IMC. In addition, the ECD of nano scale multilayer systems (Pd-Sn) are investigated regarding their application for the reactive bonding of components in electronic manufacturing.

Furthermore, the ECD process is not limited to aqueous electrolytes. The department System Packaging works on the ECD with ionic liquids focused on Al deposition as well. Electroplated Al could be applied as electrical traces and bonding layers in microsystem technology as well as in printed circuit boards.

Applications

Various application fields of the ECD metal layers are listed below.

Application

Material

Substrate size

Intermediate layers for wafer bonding

Cu, Au, Sn, AuSn (eutect.) In, Ga, SnAg, Al (ILs)

100 mm … 200 mm

 

Multilayer deposition for reactive wafer bonding

 

Pd, Sn

Bumping (UBM, pillars, solder bumps)

 

Ni, Au, Cu, Sn, SnAg, AuSn (eutect.) Al (ILs)

Through Silicon Vias (TSVs)

Cu, Al (ILs)

100 mm

(150 mm planned)

 

Equipment

The available deposition equipment and processes are shared with the department Nano Device Technologies.

  • Semi-automatic vertical deposition tool for 100…200 mm wafer (Ramgraber)
  • Semi-automatic fountain plater for 100…200 mm wafer (RENA)
  • Vertical deposition tool for wafer and customized substrates (panels, foils) up to 200 mm in size (Walter Lemmen)
  • Mobile Plating Unit for ionic liquid based ECD for 100…150 mm wafer (Silicet AG)
  • Mobile Plating Unit for AuSn alloy deposition for 150…200 mm wafer (Silicet AG)
  • Basic research with a Hull cell (Yamamoto) or in a beaker
  • Different pulse plating power sources (plating electronic) and a potentiostat VersaSTAT 3 (Princeton Applied Research)