Surface Preparation for Interconnect Bonding

ONTOS Atmospheric Plasma was developed to eliminate hydrocarbon contamination and reduce surface oxides to promote metal-to-metal bonding. The initial development was carried out on Indium to Indium compression bonding at room temperature or for reflow bonding .

The system is also capable of passivating the exposed metal surfaces against re-oxidation. This passivation is performed at the atomic level on the surface and therefore can be left in place during subsequent bonding without affecting interconnect adhesion or conduction. Consistent bonding is enabled at reduced temperatures and bond forces, compared to other surface preparation techniques.

Untreated Indium to Indium surface


  • The presence of organics and native sub-oxides inhibit Indium-to-Indium adhesion.
  • The “Skin” must be split by excessive deformation to get In-In contact (white lines above)
  • This results in poor hybrid reliability
Treated Indium to Indium surface


  • Proper surface preparation removes organics and native sub-oxides.
  • Enables instant bonding with the slightest contact.
  • Results in ideal metallurgical bond with high reliability

Surface activation for direct bonding.

  • SiO2–to–SiO2 (demonstrated at Room Temperature)
  • Au-to-Au (demonstrated as low as 100°C).
  • Cu-to-Cu (demonstrated as low as 250°C).

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ONTOS is used for many applications within the semiconductor industry for Surface Preparation using a uniquely designed, patented Atmospheric Plasma with oxidizing or reducing chemistry. ONTOS:

  • Performs Cleaning
  • Eliminates Organic Contamination
  • Activates Surfaces
  • Removes Oxidation

Our innovative process applies a gaseous passivation that delays the re-oxidation of the metallic surfaces. Learn more about the process and where ONTOS is used!