The calibration procedure is one of the key functions of the GSR software. After calibration of the SEM system, batches of GSR samples are configured to begin a run.
Samples can be arranged on the stage in a regular or irregular array of up to 16 samples. In both cases, the operator can use the pre-defined substage layout. This allows fast and accurate recording of the sample positions without moving the stage.
Information such as sample size, search area, sample array, number of samples, minimum size of search particles, and percentage of stubs to be analyzed are defined. Search “stop” criteria and “run-time” options such as maximum number of particles per sample and “pause” are available. A typical GSR run requirement is to search for particles 0.5 microns or greater in size over the 100 mm² surface of a taping. The GSR software optimizes the search by calculating the search magnification based on the minimum particle size sought. For a search of 100 mm², an array of 130 fields is needed, using a typical magnification of 120x, with a confidence level of 2×2 pixels per particle. “A confidence level of 2×2 pixels per particle” means that in order for a group of bright neighboring particles to be classified as a particle, there must be at least two neighboring bright pixels in the X and two in the Y direction. In order to search at as low a magnification as possible, there is the option of defining a particle as one pixel (typical magnification is 60x for 0.5 micron particles or 30x for 1.0 micron particles). The latter results in a search of only 9 fields for a 100 mm² taping. Using the fast scan on the SEM, the empty fields can be searched in as little as 60 minutes for a 10 mm x 10 mm field, giving a fourfold improvement over the generic scan rate. Operating at one pixel per particle as a minimum particle-definition criterion will result in a faster scan, but may not be as reliable if there are very small GSR particles present. It can, however, be used as the first, fast indication of the suspect sample.