Demand for flexible display for hand-held devices and television has led manufacturers to invent new ways of handling ultra-thin flexible substrates in display manufacturing platform. To enable handling of ultra-thin substrates, temporary bond-debond technology has been invented by which an ultra-thin flexible substrate can undergo all necessary process steps for manufacturing microelectronics while it is temporarily bonded to a rigid carrier. While the rigid carrier provides support by preventing bowing and bending of the ultra-thin substrate during processing it remains chemically inert to the flexible substrate. Thus, at the end of microelectronics processing, the flexible substrate can be debonded from the supporting carrier without any breakage. Several approaches of temporary bonding-debonding have been investigated over the years and it is still an active area of research. In general, the technique involves creating a temporary adhesive interlayer between the two substrates using adhesive films, or, plasma-polymerized fluorocarbon layer, or, laser-releasable polymers etc. The interlayer between flexible substrate and rigid carrier is generally chosen based on the peak processing temperature requirement for the microelectronics devices.<br/>In this work, we present a simple method of modulating wetting and adhesion of glass substrates by a variety of surface treatments in order to achieve temporary bonding and debonding. First, we discuss an aqueous surface functionalization process using surfactant molecules which provides partial blocking of surface hydroxyl groups on carrier substrate to allow enough adhesion between flexible glass and a rigid glass carrier via secondary forces while allowing mechanical debonding even after heating to 400C (relevant for thin film transistor processing). For even higher temperature, up to 650C, complete blocking of surface hydroxyl groups is required which can be achieved by using polymeric molecules. Through optimization of processing and surface chemistry we achieve three key attributes – (i) self-bonding of glass pairs via strong secondary forces (ii) manual debonding after thermal treatment and (iii) minimal defect formation related to degradation of interlayer molecules as a result of high temperature processing. Additionally, we show feasibility of high-throughput manufacturing-friendly processability of this technology.

Modulating wetting and adhesion properties of glass for temporary bonding

ACS Fall 2021

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