"Hybrid bonding" is an advanced connection technology in semiconductor production in which two wafers or chips (dies) are connected directly to each other via copper contact surfaces. This eliminates the need for conventional solder balls. In modern die-to-wafer (D2W) or wafer-to-wafer (W2W) hybrid bonding, real-time planarity measurement is the decisive factor for a reliable process.

Capacitive distance sensors play a central role here by enabling the non-contact measurement of shape deviations on wafers - for example due to bending, twisting or local distortion. In this way, the sensors check the planarity of the wafers and provide essential measurement data for adaptive leveling of the bonding units.

Inline planarity control before bonding

Depending on the measurement task, sensor arrays scan the surface of the upper and lower wafer and detect local elevations, depressions, inclinations or the entire deflection. The measurement data flows into an active position correction of the wafer stages. If height differences are detected, the bonding unit can be precisely aligned in the Z direction using piezo actuators or precision axes, for example. For very small chips, segmented surfaces on the chuck are also used, which can be leveled locally.

Thanks to the vacuum-compatible design, the compact sensors can be used in almost all areas of application.