Temporary Bonding for High Temperature Processing of Thin Glass Using Plasma Activated DLC Layer

Abstract

Commercial temporary bonding technologies utilize relatively thick polymeric materials whose use is limited to below 400oC, typically below 250oC. While adequate for many BEOL processes, the temperature limitation and outgassing from the bonding media are incompatible with higher temperature processes such as CVD growth, Au eutectic bonding and other processes for MEMS, photonics, or packaging applications. This talk describes a temporary van der Waals wafer bonding method using a thin continuous layer of PECVD deposited diamond like carbon (DLC) layer suitable for smooth glass, silicon and sapphire substrates. Rapid self-propagating bonding is achieved through plasma activation of the bonding surface. Raman and optical characterization of the DLC layer are consistent with a hydrogenated amorphous carbon structure. A 4 nm thick N2-O2 treated DLC layer is shown to bond thin glass to a display glass carrier with a bond energy <500mJ/m2 and minimal blistering at temperatures up to 600C. Bond energy of thin glass bonded with DLC was shown to be less than 400 mJ/m2 throughout a simulated LTPS TFT thermal cycle. The DLC bonding layer remains adherent throughout the vacuum, thermal and wet processing steps of typical semiconductor and MEMS fabrication; yet the bond energy between the pair remains low-enough after the thermal processing steps that renders the pair fully detachable.