Thermal Control Wafer With Integrated Heating-Sensing Elements

What is this patent about?

’432 is related to the field of integrated circuit (IC) testing, specifically wafer probe testing, where individual IC chips are electrically tested while still part of a semiconductor wafer. This testing is crucial for identifying defective chips early in the manufacturing process, preventing further costly processing steps. A key challenge is maintaining accurate and stable temperatures of the IC chips during testing, as testers are expensive and any idle time waiting for temperature stabilization results in significant financial losses. Prior solutions involve using heated or cooled chucks, but these may not adequately respond to localized temperature changes or transition quickly between set point temperatures.

The underlying idea behind ’432 is to use a thermal control wafer (TCW) with independently controllable heater zones, each containing a heater-sensing element . This element serves a dual purpose: it generates heat via Joule heating during a heating mode and acts as a resistance temperature detector (RTD) during a sensing mode. By using the same element for both heating and sensing, the system can more accurately control and monitor the temperature of each zone, responding quickly to localized temperature changes during IC testing.

The claims of ’432 focus on an apparatus for controlling the temperature of devices under test (DUTs) using a thermal control wafer (TCW). The TCW has multiple independently controllable heater zones, each with a heater-sensing element. This element generates heat during a heating mode and provides a resistance reading during a sensing mode. The apparatus also includes a coldplate positioned under the TCW and a thermal controller with multiple thermal control channels multiplexed to the heater zones.

In practice, the TCW is placed between the wafer under test (WUT) and a coldplate. The thermal controller activates specific heater zones based on the location of the DUTs being tested. During the heating mode, the resistive trace in the heater-sensing element generates heat. During the sensing mode, the controller measures the resistance of the trace to determine its temperature, using pre-established calibration data. This allows for precise temperature control of individual DUTs or groups of DUTs on the wafer.

This approach differs from prior solutions that use separate heating elements and temperature sensors. By integrating both functions into a single element, ’432 reduces the number of components, simplifies wiring, and potentially minimizes electrical noise. The use of multiplexed thermal control channels allows for individual control of each heater zone, enabling the system to respond quickly to localized temperature changes and maintain stable temperatures during testing. The coldplate provides a means for cooling the TCW, and the thermal controller can adjust the fluid flow rate through the coldplate based on the power supplied to the heater zones.