Abstract: A system for testing circuits of an integrated circuit semiconductor wafer includes a tester system for generating signals for input to the circuits and for processing output signals from the circuits for testing the wafer and a test stack coupled to the tester system. The test stack includes a wafer probe for contacting a first surface of the wafer and for probing individual circuits of the circuits of the wafer, a wafer thermal interposer (TI) layer operable to contact a second surface of the wafer and operable to selectively heat areas of the wafer, and a cold plate disposed under the wafer TI layer and operable to cool the wafer. The system further includes a thermal controller for selectively heating and maintaining temperatures of the areas of the wafer by controlling cooling of the cold plate and by controlling selective heating of the wafer TI layer.