Method of having good thermal isolation in wafer test cassette

A wafer test cassette, having at least one fluid inlet and at least one fluid outlet, and the wafer test cassette comprising:

• a first housing including a probe card, wherein the probe card includes at least one probe;
• and
• a second housing set below and coupled to the first housing, a test space being defined by the second housing and the first housing, wherein the second housing is configured to carry a wafer therein, the wafer is arranged in the test space, and the at least one probe is in electrical contact with an upper surface of the wafer to perform a test process,
• wherein the second housing includes a heat source and an isolation device, the heat source configured to heat a lower surface of the wafer, and a high temperature region is defined between the lower surface and the second housing, and
• the isolation device surrounding the high temperature region for thermally isolating the high temperature region from the test space;
• wherein the at least one fluid inlet is configured to receive a gas, the gas circulates in the test space and is filled between the probe card and the upper surface of the wafer, and the gas is configured to exit through the at least one fluid outlet.