2.
Measurement Process Characterization
2.6. Case studies 2.6.3. Evaluation of type A uncertainty 2.6.3.2. Analysis and interpretation


Measurements with the probe configured in two ways  The graphs below are constructed from resistivity measurements (ohm.cm) on five wafers where the probe (#2362) was wired in two different configurations, A and B. The probe is a 4point probe with many possible wiring configurations. For this experiment, only two configurations were tested as a means of identifying large discrepancies.  
Artifacts for the study  The five wafers; namely, #138, #139, #140, #141, and #142 are coded 1, 2, 3, 4, 5, respectively, in the graphs. These wafers were chosen at random from a batch of approximately 100 wafers that were being certified for resistivity.  
Interpretation  Differences between measurements in configurations A and B, made on the same day, are plotted over six days for each wafer. The two graphs represent two runs separated by approximately two months time. The dotted line in the center is the zero line. The pattern of data points scatters fairly randomly above and below the zero line  indicating no difference between configurations for probe #2362. The conclusion applies to probe #2362 and cannot be extended to all probes of this type. 
