Fabrication and Modeling of Nitride Thin-Film Encapsulation Based on Anti-Adhesion-Assisted Transfer Technique and Nitride/BCB Bilayer Wrinkling

This paper presents buckled nitride thin-film encapsulation using anti-adhesion layer-assisted transfer technique and benzocyclobutene (BCB)/nitride bilayer wrinkling due to elastic property mismatch between the two attached materials. A 900-nm silicon nitride film is deposited on a Si carrier wafer coated with hydrophobic monolayer, and then nonpatterned nitride film is directly bonded to BCB sealing rings prepared on a target wafer at 250 °C. As bonding and subsequent cooling proceed, shearing force generated by BCB shrinking is applied to the thin nitride film. After bonding, the Si carrier wafer is mechanically separated, leaving only nitride membrane inside BCB ring. Thus, self-patterning and self-alignment have been achieved. Interestingly, most different-size nitride membranes are successfully transferred even though large-size ones have partially collapsed or highly deformed. Also, finite-element method modelings have been carried out to comprehend the formation of the wrinkling of thin elastic film on compliant substrate as well as the debonding of the transfer process of the thin film. It is found that Young's modulus of compliant substrate is significant to the wavelength of the wrinkle and maximum deflection of the buckled film. The debonding may apply substantial force to the elastic film, and thus the nitride membrane needs stabilization time as its shape changes after the debonding.