Thin glass substrates, such as Corning® Willow® Glass, offer various potential applications. These include thin and /or flexible displays for smart phones, tablets, televisions as well substrates with low dielectric constant and high temperature capability for faster and thinner microelectronic packages. However, handling thin glass is challenging due to lack of mechanical stiffness and requires innovative approach. Temporary bonding of thin wafers or panels to stiffer carrier substrates offers a solution. While adhesive based temporary bonding solutions are available, they are usually not compatible with high temperatures involved in device fabrications, such as Thin Film Transistor (TFT) fabrication for flat panel displays (FPD). Additionally, many adhesive-based technologies require laser lift-off which is expensive. In Corning, we have developed an array of surface treatment/coating technologies that offer high temperature capability (as high as 700°C) as well as potential for mechanical lift-off. These technologies are based on various surface treatments or polymeric coatings of stiff carrier substrates to achieve strong non-covalent bonding with the thin glass substrates. The technologies enable: (a) high enough adhesion energy at room temperature to withstand the device processing steps, (b) low enough adhesion energy after the thermal processing steps which allow mechanical lift-off of the thin glass from the carrier, (c) spontaneous bonding via self-propagating bond wave due to strong Van der Waal interactions between the two substrates and (d) minimal outgassing. The technologies range from vacuum based sub-monolayer surface functionalization to high throughput solution processed molecularly-thin polymeric coatings. In this talk we will first describe the theoretical and conceptual framework of various surface forces that control the adhesion between the glass pair, models to predict the bond energy as function of surface chemistry and surface energy parameters, influence of surface chemistry on bond wave propagation and thermal stability of the interface. We will also describe the processes developed and their relative strengths and applicability.

Modulation of Van der Waal forces through high temperature capable surface functionalization and coating for temporary bonding of thin glass substrates

ACS Fall 2021

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