Quality control stage in the fabrication of silicon-based integrated circuit wafers, showing a close-up of a probe which automatically test the circuitry of each chip on the wafer. Any chips that are found to be faulty are marked with ink contained in the two pens visible in centre. After probing, a wafer is baked to harden the ink; defective chips may then be identified and discarded when the wafer is sawn into individual integrated circuits, ready for the attachment of connector wires and final packaging (encapsulation).