Preliminary Study on Detecting the Internal Voltage Values of Integrated Circuits Based on Electro-Optical Frequency Mapping

Abstract

Electro-optical frequency mapping (EOFM) technology can detect node signals from the backside of integrated circuits (ICs). In the past, the detected signal only qualitatively represented the electrical activity strength inside the device. In this paper, the electro-optical signal generation mechanism of the device is systematically studied, and a concise physical model of laser beam modulation based on the optical transmission matrix is proposed. Firstly, the influence of the bandwidth of the laser and each structure covered by the laser spot on the electro-optical signal of the device is well described by the model. Secondly, the model quantifies the electro-optical signal strength, and shows it is positively correlated with the laser wavelength and the reverse bias voltage. Finally, the model is used to quantitatively calculate the accurate voltage level of the internal node inside the device using the detected signal, and the calculation results match well with the experimental results. The model provides theoretical guidance for the efficient and accurate extraction of internal voltage values of devices by EOFM technology.