Surface tension-driven chip self-assembly with load-free hydrogen fluoride-assisted direct bonding at room temperature for three-dimensional integrated circuits

Abstract

We have demonstrated fluidic chip self-assembly on Si wafers for fabricating three-dimensional integrated circuits. In this self-assembly technique, small droplets of hydrofluoric acid were employed to simultaneously align many millimeter-scale chips and directly bond them to the hydrophilic bonding areas formed on the host wafers by oxide–oxide bonding. The liquid surface tension enables many Si chips to be self-assembled with the highest alignment accuracy of 50 nm. In addition, many chips were tightly bonded to the hydrophilic bonding areas without applying a mechanical force after the liquid was evaporated at room temperature.

Dynamics of capillary self-alignment for mesoscopic foil devices

“…Capillary SA can complement pick-and-place assembly approaches to overcome their performance trade-offs. 4 Several groups have modeled 5 and demonstrated 6,7 the accuracy and repeatability of the technique. Conversely, only few studies have addressed the lateral dynamics of the alignment process 8 and, to our knowledge, only for (sub-) millimetric dies where the Bond numbers are much smaller.…”

Self-Assembly in Micro- and Nanofluidic Devices: A Review of Recent Efforts

“…Other fluid self-assembly techniques utilized load-free oxide-oxide direct bonding of self-assembled chips to wafers at room temperature after liquid evaporation when they used a solution of hydrogen fluoride in water as a liquid. This paper suggested that hydrogen fluoride concentration strongly influenced the bonding strength of self-assembled chips to wafers [72]. Arase and Nakagawa used a novel blade-coating technique that takes advantage of capillary force for rectangular-shaped SiO 2 plates of micrometer-size onto selected areas on large-scale substrates [73].…”

High precision self-alignment using liquid surface tension for additively manufactured micro components

“…Several approaches have been developed in order to alter the wetting properties of specific regions of a surface. These include (super)hydrophilic and (super)hydrophobic target sites [10][11][12][13][14][15], (super)oleophilic and (super)oleophobic for oil-based liquids [16][17][18], micropillar arrays to create hydrophobic regions [19,20], as well as most recently, receptor sites with sharp edges to inhibit liquid spreading [21][22][23][24]. These methods can be divided into two distinct areas; those which rely on altering the surface properties of specific regions to influence wetting behaviour, and those that utilise physical geometric structures to constrain liquid spreading.…”