A device for individually testing semiconductor integrated circuits in wafer form at elevated and/or reduced temperatures include a fixture body for connection to a conventional probing device. The fixture body has an open-ended aperture to permit visual inspection of a circuit being tested, a plenum to receive pressurized gas at a selected temperature(s), and nozzles to direct the gas from the plenum into the aperture for ejection onto to the surface of the integrated circuit being tested to rapdily bring that circuit to the temperature of the gas.

A wafer scale test system for testing redundant integrated circuit dies formed on a semiconductor wafer includes wafer scale test pads formed on the wafer and interchip multiplexor means for directing test signals applied to the wafer scale test pads to the individual integrated circuit dies. The interchip multiplexor means includes an input/output buffer circuit for receiving test signals from the wafer pads and applying the test signals to selected interchip multiplexor lines routed to the individual circuit dies. Readouts from output pads on said integrated circuit dies are routed back through the input/output buffer circuit to the wafer test pads to provide test output signals. Low cross-section connecting means are provided across dicing lanes between the integrated circuit die contact pads and the interchip multiplexor lines to avoid shorting during the dicing operation. Additionally, line protection circuits are provided to prevent destruction of the integrated circuit dies should shorting occur during dicing. The integrated circuit dies and wafer scale test system may optionally be partitioned into several separate groups to prevent faults in the interchip multiplexor system from rendering the entire wafer useless.

In order to permit probing access to a printed circuit board while the printed circuit board is under test in a cold controlled environment, a doubled walled environmental hood is provided, the inner and outer walls spaced apart by rings containing orifices therein, a probe hole formed in the center of the ring and the outer wall cut away in the area of the ring, with a cold gas supplied to the inside of the inner wall and a hot gas supplied to the space between the walls, whereby the hot gas escaping through the orifices in the rings will raise the temperature of the cold gas escaping from the probe hole to prevent frosting and permit viewing of the printed circuit board under test for probing.

A prober for the electrical testing of unpackaged integrated circuits on a semiconductor wafer can test these devices between subfreezing to elevated temperatures without generating atmospheric fog or frost on the wafer or associated equipment by directing an enclosed tubular curtain of dry gas, such as heated liquid nitrogen, down from a circular nozzle above the wafer to encircle the device under test. Observations can be made and electrical tests performed within the curtain while all moist atmospheric air is purged from the wafer and surrounding areas so that fog and frost cannot form.

A wafer probe station has a wafer-supporting vacuum chuck, together with one or more substrate-supporting auxiliary vacuum chucks having independent vacuum controls for mounting contact substrates and calibration substrates simultaneously with the wafer. A detachable interconnection of the various chucks enables independent replacement of each chuck to accommodate various different chuck types, and also permits the elevations of the respective chuck surfaces to be adjusted relative to each other to compensate for differences in thicknesses between the wafer substrate and the calibration or contact substrates. The invention is especially useful in wafer probe stations equipped with enclosures for controlled-environment testing where a large variety of different wafer chucks must be readily interchangeable for testing under different conditions.