Thomas J. Aton

Microstructure isolation testing using a scanning electron microscope

A new form of testing is described that is suitable for verifying isolation in many forms of microstructures. Excess charge is deposited on the microstructures by a scanning electron microscope (SEM) beam. On elements of the microstructures that are isolated, this excess charge induces a voltage contrast that is detected at the same time by the same beam. Isolation to approximately 2×1011 Ω can be verified. The method is simple and fast, requiring only a standard SEM and simple test structures.

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.<<ETX>>

Comparison of charge collection from energetic ions typical of neutron-recoil events with charge collection from alpha particle strikes

We describe experimental measurements of the charge collection from fluorine ions striking ICs. The fluorine ion strikes produce charge bursts similar to the charge bursts from energetic heavy ions produced when cosmic-ray-generated neutrons collide with silicon nuclei in an IC. Charge collection from the ions strikes is about ten times as large as from alpha strikes, too large to be easily overcome in DRAM design. The ion-beam technique provides a useful tool for investigating charge bursts of the silicon-recoil events, now thought to be a major source of DRAM errors.