Design and Fabrication of a Multi-Functional Programmable Thermal Test Chip

Abstract

This paper focuses on the design and fabrication of a new programmable thermal test chip as a flexible and cost-effective solution for simplification of characterization/prototyping of new packages. The cell-based design format makes the chip fit into any modular array configuration. One unit cell is as small as 4x4 mm2, including 6 individually programmable micro-heaters and 3 resistance temperature detectors (RTDs). All micro-heaters and sensors have 4-point Kelvin connections for improved measurement accuracy. The chip contains 2 metal layers: 100 nm thin-film Titanium to create micro-heaters and RTDs, and 2 μm Aluminum to add single bump measurement units and daisy chain connections. These structures facilitate bump reliability investigations during thermal/power cycling tests in flip-chip assembly technology. The calibration curves of RTDs show a sensitivity of 12 $\Omega$/K which is improved by 50 percent compared to the state-of-the-art TTC. The proposed design provides higher spatial resolution in thermal mapping by accommodating 3 RTDs per cell. The dense configuration of micro-heaters increases the uniformity of the power dissipation, which enhances the accuracy of thermal interface material (TIM) characterizations. The steady-state infrared (IR) thermography of a 20x20 mm2 TTC, including 150 active micro-heaters, verifies the promising uniformity of the heat profile over the chip surface.