Wafer Backgrind

Wafer Backgrind is the process of grinding the backside of the wafer to the correct wafer thickness prior to assembly. It is also referred to as 'wafer thinning.' Wafer backgrinding has not always been necessary, but the drive to make packages thinner and thinner has made it indispensable. Most package types in the semiconductor industry today would require a wafer thickness ranging from 8 mils to 20 mils.

Wafers normally undergo a cleaning and surface lamination process prior to the actual backgrinding process. Surface lamination involves the application of a protective tape over the surface of the wafer to protect it from mechanical damage and contamination during backgrinding.

The surface-laminated wafers are then loaded into cassettes that will go into the cassette holder of the backgrinding machine. The machine picks up the wafer from its backside (untaped side) with a robotic arm, which positions the wafer for backgrinding. The backgrinding process is automatically accomplished by a grinding wheel, following a precise set of parameters to ensure proper backgrinding.

To remove debris from the wafer while backgrinding, the wafer is usually washed continuously with D/I water while undergoing backgrinding. Once the wafer has been background, the wafer is returned to the cassette, and the cycle is repeated for the next wafer.

Parameters set for backgrinding include spindle speed, spindle coolant water temperature and flow rate, D/I water temperature, initial and final wafer thickness, and feed speeds.