Die singulation

The areas that have been cut or sawn away, called die streets, are typically about 75 micrometres (0.003 inch) wide.

The wafer is ground down in a process called back side grinding (BSG) before it is diced.

It works as a two-stage process in which defect regions are firstly introduced into the wafer by scanning the beam along intended cutting lines and secondly an underlying carrier membrane is expanded to induce fracture.

[6] Defect regions of about 10 μm width are inscribed by multiple scans of the laser along the intended dicing lanes, where the beam is focused at different depths of the wafer.

[7] The figure displays an optical micrograph of a cleavage plane of a separated chip of 150 μm thickness that was subjected to four laser scans, compare.

A defected region of about 10 μm width is finally inscribed in the wafer, along which preferential fracture occurs under mechanical loading.

The fracture is performed in the second step and operates by radially expanding the carrier membrane to which the wafer is attached.

Dry dicing methods inevitably have to be applied for the preparation of certain microelectromechanical systems (MEMS), in particular, when these are intended for bioelectronic applications.