Estimating heights of defects in a wafer

A method of correlating a plurality of scaling factors to a plurality of defects, wherein the plurality of scaling factors is used to estimate height of defects present in wafers, the method comprising:

• obtaining a set of Scanning Electron Microscope (SEM) images corresponding to a defect present in a wafer from a training dataset, wherein the training dataset comprises a plurality of sets of SEM images corresponding to the plurality of defects;
• creating an un-calibrated 3D model of the defect based on the obtained set of SEM images;
• transforming the un-calibrated 3D model to a calibrated 3D model using a scaling factor;
• creating a shadow mask associated with the defect based on the obtained set of SEM images;
• creating a candidate shadow mask based on the calibrated 3D model and a light variable from a set of light variables, wherein each variable in the set of light variables is representative of a light direction;
• determining a shadow loss based on the shadow mask and the candidate shadow mask;
• determining whether a minimum value of the shadow loss is obtained based on a set of previous values of the shadow loss;
• and
• mapping the scaling factor with one or more attributes of the un-calibrated 3D model of the defect based on determining that the minimum value of the shadow loss is obtained.