Hi,guys!
I'm reading "cmos IC layout"
It's said " Probe pads ,are used exculsively for the preproduction debugging and
evaluation stage.Product engineers use probe pads to check the functionality and
timing of internal nodes of that have not been qualified for production.
Probe pads can be placed anywhere on the die ,since they are used when the die
is completely unprotected. The size of the probe pads is dependent on the equipment that is used.
Historically,probe pads were not explicitly implemented,because a single via was big enough for the probes that were avialable .As layer geometries have shrunk,a single via has become too small for physical probing.Generally ,a probe pad that is in the range of 1 um*um is sufficient. Page 205.