Innovative Nanoimprint Tools for Optoelectronic Applications

摘要

This project addresses a low pressure, room-temperature nano imprint lithography that uses low viscosity UV curable imprint liquids. As compared to Si wafers, compound semiconductor wafers are known to be more fragile and prone to breakage under localized stresses. Further, the flatness and parallelism for this type of wafer is known to be not as good as those of Si wafers. During imprinting processes, a pushing force occurs when a master mold contacts the wafer via a fluid layer between them and a pulling force applies to the wafer when they separate after the fluid layer is UV cured. Excessive deformation and local stresses can cause either a mechanical failure of the wafers or undesirable imprint layers. During the reported period, imprints were performed on 2(inch) GaAs and 2(inch) InP wafers. Even though the imprinting and separation can induce large forces and deformations to the wafers, they do not appear to cause local stresses to the wafers. However, when there is a particle that can cause a locally concentrated stress in the wafer, wafer failures occurred in the form of crack propagation and breakage failure. In order to avoid the local stress and large deformation to the wafers, fine-grooved wafer chucks were designed and prototyped. Force estimations based on a Newtonian fluid model provided the force-time-thickness relationship of the imprint layer. The thickness variation of the imprinted layer on compound semiconductor wafers was measured. Three potential solutions to handle the excessive surface variation are suggested as future work.