There is significant experience and expertise in bonding standard and novel substrates within QAMEC. A number of techniques have been developed inhouse to ensure substrate integrity and improve yield.
Direct or spontaneous bonding describes a wafer bonding process without any additional intermediate layers. The bonding process is based on chemical bonds between two surfaces of any material possible meeting numerous requirements. These requirements are specified for the wafer surface as sufficiently clean, flat and smooth. Otherwise unbonded areas so called voids, i.e. interface bubbles, can occur.
- Silicon on Insulator SOI
- Silicon on Sapphire SOS
- Germanium on Insultor GeOI
- Germanium on Sapphire GeOS
Anodic bonding describes is a process to seal glass to either silicon or metal. The glass typically contains a high concentration of alkali ions. When the joined substrates are heated the ions become more mobile and when a sufficiently powerful electrostatic field is applied the two substrate surfaces are drawn together.
- Typically used as a low temperature capping layer for micro fluidics were a hermetic seal is required
Adhesive bonding describes a wafer bonding technique with applying an intermediate layer to connect substrates of different materials. The adhesive Benzocyclobuten (BCB) is deposited on one or both substrate surfaces. As the adhesive is fluid prior to bonding this process facilitates the integration of patterned surfaces.