A probe station allows a user to position electrical, optical or RF probes onto a device and to then test the response of that device to an external stimulus (electrical, optical or RF). These tests can be simple such as continuity or isolation checks, or more sophisticated involving full functional tests of complex microcircuits.
A probe station can run tests on a full wafer or after it has been sawn up into individual die. Testing at a whole wafer level allows the manufacturer to test a device multiple times at different stages throughout the production process, and closely monitor fabrication to see if any defects are present. Testing on individual die prior to final packaging allows defective devices to be removed from circulation ensuring only functioning devices are packaged.
How does it work?
A probe station holds a wafer or a die on a chuck mounted on a stage which allows the positioning of the DUT in the centre of the field of view of the microscope. Manipulators are placed on the planar surface of the platen, and into the manipulators are inserted probe arms & tips. The probe tips must be suitable for the test programme to be carried out. The user then precisely positions the probe tips on the correct locations within the device by adjusting the corresponding manipulator. The probes are then brought into contact with the wafer by lowering the platen; the device is now able to be tested.
For wafers with multiple devices, after the first device is tested the platen can be raised and the stage holding the wafer moved to the next device. The process of positioning the probe tips is repeated until all required devices have been tested. This process can all be done manually by an operator but if the stages and manipulators are motorised and the microscope connected to a computer vision system then the process can become semi-automatic or fully automatic. This can increase the productivity and throughput of the probe station and reduce the labour needed to run multiple tests.