Gate leakage evaluation of GAA transistors using SEMs

Abstract

Voltage contrast is an important imaging technique that allows SEMs to inspect electrical defects in plugs and wires by probing the presence or absence of charging upon electron beam irradiation. However, SEMs also have the potential to be inline electrical metrology tools that can evaluate device critical properties by quantifying the level of charging. One technique to assess the amount of charging is to analyze transient detector signal upon electron beam irradiation. Previous study has shown that this technique can be used to evaluate the leakiness of MOS capacitors when the oxide thickness varies. In this work, we have explored the technique’s sensitivity to various MOS capacitor parameters: interlayer thickness, high-k oxide material, work function metal thickness, and interface dipole formation. The results show that the technique is sensitive to the leakiness of the capacitors regardless of the parameter causing the leakage. The demonstration of the technique was further extended to the evaluation of leakiness of gate-all-around transistor gate electrodes. The leakiness measured with the technique on probe pads connected to the gate was compared to the leakage current measured by an electrical tester. These results show the electron beam technique can be sensitive to the leakage current of gate-all-around transistor gate electrodes with a precision of about 1 order of magnitude in terms of leakage current.