New Method for Reduction of the Capacitor Leakage Failure Rate Without Changing the Capacitor Structure or Materials in DRAM Mass Production

摘要

In the development of dynamic random access memory (DRAM) with a device size of 20 nm or less, the leakage current of a capacitor with high-k dielectrics is one of the main factors causing the failure of a device. To reduce the failure rate of the device, we conducted experiments to reduce the boron impurities, which form defect sites in the dielectrics of the capacitor. The boron source flux was reduced during the deposition process of the capping layer after the formation of the capacitor, and the actual boron concentration in the capping layer was measured by an atom probe tomography. The leakage current characteristics of the samples were confirmed through the dielectric leakage failure test, which is a mass production test technique. In addition, the resistance failure test was performed to measure the risk of increased resistance. From these results, it was confirmed that the failure rate due to the leakage current of the capacitor decreased linearly with reduced boron concentration and the increase in failure rate due to the cell node resistance was negligible. In addition, the results show that the failure rate of mass-produced DRAM products can be significantly reduced without any change in the structure or materials of the capacitor. This is expected to contribute greatly to the development of DRAM with dimensions on the scale of 20 nm or less.