In-line monitoring of the change of residual stress in nano-scale transistors during their thin-film processing and packaging

In this study, the change of the residual stress in transistors during their fabrication processes was analyzed by a finite element method (FEM) and measured by developed strain sensors. The sensors embedded in a PQC-TEG were applied to the measurement of the change of the residual stress in a nano-scale transistor structure during thin film processing. The change of the residual stress was successfully monitored through the process such as the deposition and etching of thin films. In addition, the fluctuation of the process such as the intrinsic stress of thin films and the height and the width of the etched structures was also detected by the statistical analysis of the measured data. The sensitivity of the measurement was 1 MPa and it was validated that the amplitude of the fluctuation during thin-film processing exceeded 100 MPa. This technique is also effective for detecting the spatial distribution of the stress in a wafer and its fluctuation among wafers.