Plasma dicing enables high accuracy self-alignment of thin silicon dies for 3D-device-integration

Abstract

Thin silicon chips with a thickness of 50 m are of light weight and are able to swim on droplets of fluids like for instance water. If the liquid shows a specific wetting behavior with respect to the underlying substrate then droplet and chip can move and self-align. Recent research work was carried out to determine the self-alignment accuracy of 50 m thin silicon dies on plasma programmed surfaces. The self-alignment process sequence for die assembly comprise the following steps: surface programming by CF4 plasma treatment, dispense droplets of water on the metal target areas, pick-up of a 50 m thin chip, move chip tool above the selected target area, let the chip fall down and self-align on the liquid surface on the target area. Within short time the droplet dries off and then the thin die sticks to the substrate. Self-alignment accuracy was measured by infrared microscopy at the position of the alignment marks of top and bottom devices. The paper will report in detai l about sample preparation, selective plasma programming, self-alignment accuracy of thin dies and its dependence of the die size. Furthermore, the chemical composition of the relevant surfaces after CF4 plasma activation were analysed by XPS measurements

Roll-to-roll processing of film substrates for hybrid integrated flexible electronics

“…After successful self-alignment of the chips on the wafer substrate, IR microscopy analysis conducted on the samples revealed that the overall alignment accuracy was well below 3 μm and an accuracy in the range of just 1 μm was observed several times repeatedly [50]. Figure 16 exhibits the alignment accuracy graph of 7×7 mm 2 chips on a wafer substrate.…”