Wafer bonding is a procedural step in semiconductor technology, where two wafers are joined. For certain applications like the encapsulation of chip sensors this process is carried out under vacuum.
When loaded the bond chamber is evacuated in a bypass connection by means of the roughing pump until a vacuum level is reached, where the system can be switched smoothly to the high vacuum pump. The bonding process is then performed under high vacuum conditions. Absolute pressure in the bypass-line must be accurately controlled during evacuation in order to prevent damaging of the high vacuum system. During the wafer bonding the vacuum inside the chamber has to be monitored to guarantee the required results.
A VSC43MA4 type rough vacuum transducer is used for controlling the bypass cycle. Its ceramic sensor measures the absolute pressure with the required accuracy and is nearly maintenance-free. The process pressure of the bonding procedure is monitored by means of a VSM transducer with Pirani/Cold Cathode combination sensor.