sound advice above! If you read up alittle on this topic, You'll find that you can add ..lets say.. room temp water to your carboy and then add you cooled wort...then top up to final volume! The first water in the carboy will absorbe the heat shock!
I personaly do this and dump the wort when it is about 80 deg. I have to admit I have been pitching yeast a little cold!
Since I've got the chiller in the boil, I just wait until it's down to 70-80 deg. Unless I'm lagering, which means I've got to chill it in the fridge, I just let the chiller do it's work. My $0.02
I'm assuming partial boil extract and a room temp carboy ( or at least not freezing cold carboy- PHX yeah right!)
The wort needn't be that cold if your only concern is carboy breakage.
The old-school (no thermometer) technique was to wait until you could pick the pot up with your hands on the side and not burn your hands. That puts the wort temp between 80° - 90° F.
Add some of your top off water to the carboy (to buffer), then your wort and then the remaining top off water.