PCB soldermask endurance
To quote the linked datasheet:


  Note that in both of these patterns, the solid ring around the sound
  port is still present; this ring is needed to ground the microphone
  and for acoustic performance. The pad on the package connected to this
  ring is ground and still needs a solid electrical connection to the
  PCB ground. If a land pattern similar to Figure 16 or Figure 17 is
  used on a PCB, make sure that the unconnected rectangle on the bottom
  of the INMP521 is not placed directly over any exposed copper. The
  ring on the microphone is still at ground, and any PCB traces routed
  beneath it must be properly masked to avoid short circuits.


As it says, avoid exposed copper. Standard solder mask should be sufficient to insulate traces from the ground ring on the device. If in doubt, you can use vias and put the traces on another layer.