Milwaukee (20-13) will face No. 3 seed Wright State in the championship on Tuesday.
The Panthers trailed by four late in regulation, but Aaron made two free throws and a layup in the final minute to force overtime. He split a pair of free throws and missed a 3-pointer on the following possession, but Tiby got the putback. Aaron drained the clock down to 22 seconds and drilled a jumper, making it 69-64.
Keifer Sykes followed with two free throws, but couldn't connect on a jumper following a Kyle Kelm turnover. Tiby sank four straight free throws to ice it.
Greg Mays had 17 points and nine boards, while Sykes had 15 for the Phoenix (24-6).