Three-dimensional (3D) integration is promising to provide dramatic performance and energy efficiency improvement to 3D logic-DRAM integrated computing system, but also poses significant challenge to the yield. To address this challenge, this paper explores a way to leverage logic-DRAM co-design to reactivate unused spares and thereby enable the cost-efficient technique to repair 3D integration-induced defective DRAM cells after die stacking. In particular, we propose to make the DRAM array open its spares to off-chip access by a small architectural modification and further design the defective address comparison and redundant address remapping with an efficient architecture on logic die to achieve equivalent memory repair. Simulation results demonstrate that the proposed repair technique for stacked DRAM can significantly alleviate potential yield loss, with minimal area and power consumption overhead and negligible timing penalty.