RS50

The RS50 is capable of handling wafers up to 200 mm in diameter. The RS50 measures sheet resistance over a range from 1 mohm/sq to 200 Mohm/sq. The RS50 is a mapping system, meaning it can automatically collect data across the surface of a wafer to generate a spatial map of sheet resistance.^[2]

Four-point probe systems operate by placing four equally spaced probes in contact with the surface of a thin film. A current is forced through the two outer probes while the voltage drop is measured across the two inner probes. The sheet resistance is calculated from the current and voltage values using a geometric correction factor that accounts for the probe spacing and sample dimensions.

Four-point probe mapping systems like the RS50 are used in semiconductor fabrication lines for inline quality control. The RS50 is typically positioned after thin-film deposition steps such as metal sputtering, chemical vapor deposition, or ion implantation. Sheet resistance measurements provide feedback on film thickness, doping level, and uniformity before subsequent process steps such as etching or lithography.

The RS50 can also be used in research and development environments to characterize experimental films. The mapping capability allows engineers to identify non-uniformities in deposition or doping processes. The tool is typically operated in a cleanroom environment and requires calibration with known resistance standards.

Common processes that require sheet resistance mapping include metal deposition quality control, doped polysilicon monitoring, and ion implant uniformity verification. The RS50 can also be applied to characterization of thin films in photovoltaic devices, flat-panel displays, and other microelectronic structures. The mapping feature provides spatial information about resistance variations that is critical for process development and yield improvement.