Thermal Control Wafer With Integrated Heating-Sensing Elements

What is this patent about?

’609 is related to the field of integrated circuit (IC) chip testing, specifically wafer probe testing, where IC chips are electrically tested while still part of a semiconductor wafer. The background involves applying signals to electrical pads on the IC chip using a wafer prober interface to determine if the chips meet performance criteria. Existing systems use thermal control elements, such as heated or cooled chucks, to maintain accurate and stable temperatures during testing. However, these systems may not adequately respond to localized temperature changes or quickly transition between set point temperatures, leading to costly idle time for expensive test systems.

The underlying idea behind ’609 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 through Joule heating during a heating mode and provides a resistance reading during a sensing mode. By using the same element for both heating and sensing, the system can more accurately and efficiently control the temperature of individual DUTs or groups of DUTs on the wafer.

The claims of ’609 focus on an apparatus for controlling the temperature of devices under test (DUTs) using a thermal control wafer (TCW). The TCW includes a plurality of independently controllable heater zones, each with a heater-sensing element. This element, a resistive trace, generates heat during a heating mode and provides a resistance value during a sensing mode. A thermal controller determines the temperature of each heater zone based on the resistance of its heater-sensing element. The apparatus also includes a coldplate disposed under the TCW.

In practice, the TCW is placed between the wafer under test (WUT) and a coldplate. The thermal controller activates specific heater zones to heat the corresponding DUTs to a desired temperature. During the sensing mode, the controller measures the resistance of the heater-sensing element in each zone to determine its temperature. This feedback allows the controller to precisely adjust the power supplied to each heater zone, maintaining the DUTs at the required temperature for testing. The coldplate helps to dissipate heat and maintain a stable base temperature.

’609 differentiates itself from prior approaches by integrating the heating and sensing functions into a single element within each heater zone. This eliminates the need for separate heaters and temperature sensors, reducing the number of electrical connections and simplifying the design. Furthermore, the independent control of each heater zone allows for more precise temperature management of individual DUTs or groups of DUTs, addressing the limitations of traditional chuck-based thermal control systems that struggle with localized temperature variations. The use of a TCW also enables faster temperature transitions, reducing test system idle time and improving overall testing efficiency.