Patent ID: 7145140

Claim:
A method of determining whether a conductive layer of a wafer is exposed through a contact hole that is formed in an overlying insulating layer by a plasma process, comprising: repeatedly scanning an inside of the contact hole with a beam of primary electrons; collecting secondary electrons that are generated by a reaction between the primary electron beam and an inside surface of the contact hole and that are emitted from the contact hole; and determining whether a surface of the conductive layer is exposed through the contact hole in the insulating layer pattern based on a change in an amount of collected secondary electrons, wherein said determining comprises, providing a sample graph which shows the change in the amount of collected secondary electrons with respect to a number of scans of primary electrons; providing a reference graph which shows a change in the amount of secondary electrons detected in a standard state where the conductive layer is exposed with respect to a number of scans of primary electrons; and determining whether the conductive layer is exposed by comparing a waveform of the sample graph to a waveform of the reference graph.