What is a probe station comprised of?
A probe station is composed of a few basic components, including:
The core of a probe station is a device to position the wafer or die. This is usually done with a “Stage” that moves the device in three axes (X, Y, and Z) and provides a way to rotate the device (Theta).
The station needs a way to hold the device without damaging it, which is usually accomplished with a very flat, metal surface called a “Chuck.” The chuck secures the device mechanically with clamps or uses a light vacuum to secure the wafer in place.
Accessories such as chip trays or frame slides may be added if individual dies or stretched, sawn wafers are being probed.
Probe stations use manipulators to position probes on the device under test (DUT). Manipulators sit on a flat surface referred to as a “Platen” and usually have a way to position probes easily and secure them rapidly. Manipulators often use magnets or a vacuum to affix them to their proper position. Once secured, the manipulator can accurately position the probe tip in X, Y and Z directions and, in some cases, provide rotational movement.
Probe tips, also known as probe needles, are inserted into a single probe arm and mounted to a manipulator. The probe tip size and material depends on the size of the feature being probed and the type of measurement needed. Probe tips directly contact the DUT, and the probe arms should be matched to the probe tip.
The final element of the probe station is a mechanism to visually magnify the device and probe tip, often referred to as the system’s ‘Optics.’ This enables the user to precisely and correctly place the probe tips on the DUT. Most probe stations use either a stereozoom microscope, a digital camera, or both.
In Conclusion:
A basic probe system is comprised of five different parts: a stage, a chuck, manipulators, probe needles, and a mechanism to visually magnify the device.
More advanced systems will incorporate motorized stages or manipulators under computer control to automate the die to die movement process. Probe stations are often built upon a vibration isolation table to ensure stability of the measurement platform. Depending on the test parameters, probe stations may be equipped with an environmental chamber and thermal control so testing can be performed in a cold or hot environment.
For more information on probe stations, click here or Request a Discovery Call.