It is very important to understand the mechanical properties of polymers at the nanoscale with the continuing demand of decreasing the size of circuit in the electronic industry. There has been considerable research on the confinement effect in thin films with a variety of techniques, often with conflicting results. We developed the stress-strain analysis and energy balance approach to separate the surface tension contribution to the observed rubbery stiffening. Further, the geometry effect in the nanobubble inflation technique was investigated by comparing the creep behavior of circular bubbles with that of rectangular bubbles. Next, we investigated the molecular architecture effect in the nanobubble inflation technique by comparing the creep behavior of linear PS with that of the three-arm star PS. In the last part of this thesis, the capability of the nanobubble inflation technique to investigate the yield and fracture behavior of ultrathin films was demonstrated.