STP transfer system for uniform dielectrics formation

This paper describes a novel film transfer system that enables to forth uniform dielectrics in STP (Spin coating film Transfer and hot-Pressing) technology. STP technology is a new planarization and gap filling technology for interlayer dielectrics in multi-level interconnects. STP process consists of three steps: a spin coating step, a transfer step in a vacuum chamber and a peeling off step. In the transfer step, the film formation depends on the viscosity of dielectrics. Viscosity under vacuum condition is controlled by drying the solvent of dielectric in the transfer unit. In order to transfer a dielectric to a wafer uniformly, it is necessary to investigate influence of gas flow around the film in the vacuum that is critical to film drying condition. The behavior of gas flow in the transfer unit was investigated on fluid dynamics. The calculation results showed that the transfer unit was improved for better uniformity. In the experiments, PBO (polybenzoxazole) dielectrics were formed by both units with and without improvement. It was confirmed that gas flow becomes more uniform by improving the transfer unit. The unit after improvement could form uniform PBO dielectrics on the Si wafers. Considering that the film drying uniformity is an important factor for design of the transfer unit, it is possible to apply this technology to large sized wafers and miniaturize the volume of the transfer unit.