Bonding of Glass

Direct aligned bonding is done at high temperature, which makes the bond very strong (high-pressure resistant - to 150 bar / 2175 psi). In the basic chip manufacturing process, a glass layer with holes is bonded to another glass layer with channels. For more complex devices, multi-stack bonding is required. Micronit has in-house capabilities to bond multiple wafers. This is also suitable when a large internal volume is required. Devices can then be stacked in order to raise the internal volume.

Micronit is one of the few companies in microtechnology that offers direct glass to glass and glass to silicon bonding (without an intermediate layer).

Standard Process
In the figures below three different possible processes are shown. Depending on the designs of chips or structured wafers the processes can be mixed or other possibilities can be added.

Basic Process Top substrate (typically 1.1 mm or 700 µm) with powderblasted holes is  bonded to bottom substrate (typically 700 µm) with HF etched or powderblasted channels.

Thin Bottom Process Top substrate (typically 1.1 mm or 700 µm) with powderblasted holes and HF etched or powderblasted channels is bonded to thin glass bottom substrate (typically 175 µm).

Integrated Electrodes Top substrate (typically 1.1 mm or 700 µm) with powderblasted holes and HF etched or powderblasted channels is bonded to bottom substrate with electrodes.