Design and fabrication of an ultra-thin silicon vapor chamber for compact electronic cooling

This paper presents the design and the fabrication of an ultra-thin vapor chamber exclusively composed of silicon, aimed to be integrated in microelectronic chips to spread highdensity hot spots. A process flow fully compatible with the presence of a circuit on the front side has been developed and a 1 x 1 cm2 prototype with an internal vapor cavity and a wick thickness of 210 μm has been designed and fabricated. The wick is composed of a matrix of micropillars with 5 μm diameter and 30 μm high in a square arrangement. The cavity is obtained by plasma activated direct bonding of two wafers with complementary cavities. The spreading performances have been estimated by a finite element method (FEM) modeling and presents higher performances compared to copper heat spreader with 4°C less temperature difference for a 4 W and 1 x 1 mm2 hotspot.