Operating instructions

Bond Module
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2.5 Eutectic Wafer Bonding
This is a wafer bonding process which uses as bonding layer an
eutectic alloy formed during bond process. Eutectic alloy is formed at
the bonding interface in a process which goes through a liquid phase:
for this reason, eutectic bonding is less sensitive to surface flatness
irregularities, scratches, as well as to particles compared to the direct
wafer bonding methods (metal layer can incorporate particles with
diameter lower than the eutectic layer thickness).
Figure 12 - Eutectic wafer bonding process flow
Some of the main eutectic alloys used for wafer bonding applications
are listed in table 1.
Eutectic System
Eutectic
Temperature
Bonding
Temperature
(recommended)
Au:Sn (80:20)
Au:Sn- 300°C
290°C
Au:Si
363°C
375°C
Au:Ge
380°C
390°C
Al:Ge
423°C
435°C
Au:In
510°C
520°C
Table 1 - Main eutectic combinations used for wafer bonding
For a successful eutectic bonding process it is very important that
bonder assures a good temperature uniformity across the entire wafer
surface and also to control very well the temperature value (avoid
overshooting the setpoint) in order to have a reliable process.
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