Understanding spatial resolution of laser voltage imaging
Laser voltage imaging (LVI) is a commonly used electrical fault isolation technique that is extremely useful in the localization of defects in serial chains and circuits generating specific frequencies within modern integrated circuits. The signals are generated by electro-optic phenomena and the resolution of the tool is therefore constrained by the optical diffraction limit. As such, conventional methods of understanding optical resolution in optical systems such as Rayleigh and Sparrow criteria are currently used to describe the effective resolution. This work formalizes the description of resolution in LVI considering the point spread function of the laser and the electrical circuitry the laser interacts with. Finally, the model is compared with real results across multiple laser wavelengths and is shown to be useful for resolution prediction, determination of optimum probe placement position and predicting the shape of LVI under constrained space conditions.