Using scanned electron beams for testing microstructure isolation and continuity

Scanned electron beams provide a superior method of testing for isolation and continuity in integrated circuit microstructures by observing the voltage contrast generated by charge storage on isolated nodes. The authors discuss how such beams can be used to test, ICs during the manufacturing steps to insure proper pattern transfer and isolation and, to a more limited degree, continuity. The method uses the electron beam as the active probe to both drive and test the device. Under the proper conditions, the beam can deposit charge on nodes of the IC. Nodes which are isolated change potential and exhibit voltage contrast with respect to the nodes that are fixed in potential. Thus, the beam also instantly reads out the success or failure of the isolation of a node. Examples are shown from silicon-on-insulator (SOI) mesas and from novel test structures for checking patterning fidelity in polysilicon and metal layers.<>