Specific Process Knowledge/Characterization/Profiler: Difference between revisions
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[[File:Error probability distributions sep 2020 update big.png|upright=2|alt=Four different probability distributions that contribute to the total error on the Dektak measurement for the 6.5 micron range. By far the widest distribution is the one from the error on the calibration standard, which is a Gaussian. The others are the non-Gaussian spread of the average measurement of the calibration standard height, which cuts off at the QC limits, the resolution, which is a very narrow uniform distribution, and the spread of measurement values for a given step being measured, which is a Gaussian whose width depends on the step in question.|right|thumb|The probability distributions of the main sources of error that are convoluted to create the total error on a Dektak measurement.]] | [[File:Error probability distributions sep 2020 update big.png|upright=2|alt=Four different probability distributions that contribute to the total error on the Dektak measurement for the 6.5 micron range. By far the widest distribution is the one from the error on the calibration standard, which is a Gaussian. The others are the non-Gaussian spread of the average measurement of the calibration standard height, which cuts off at the QC limits, the resolution, which is a very narrow uniform distribution, and the spread of measurement values for a given step being measured, which is a Gaussian whose width depends on the step in question.|right|thumb|The probability distributions of the main sources of error that are convoluted to create the total error on a Dektak measurement.]] | ||
To estimate the accuracy of the Dektak's measurements we have to combine the error of the calibration with the error from the limit on the resolution and the scatter of repeated measurements. This is shown graphically on the right. You can see an uncertainty budget for the Dektak measurements here (made by Rebecca Ettlinger in 2020): [[Media:uncertainty budget DektakXT | To estimate the accuracy of the Dektak's measurements we have to combine the error of the calibration with the error from the limit on the resolution and the scatter of repeated measurements. This is shown graphically on the right. You can see an uncertainty budget for the Dektak measurements here (made by Rebecca Ettlinger in 2020): [[Media:uncertainty budget DektakXT.xlsx]]. It is based on the assumption that all the error sources are independent and can therefore be added by the sum of squares method, which you can read about here: [[Media:JCGM_100_2008_E.pdf]]. | ||
The error stemming from the uncertainty on the calibration standard dominates for the 6.5 micron range, while for the other ranges the scatter of repeated measurements is also important. Using the sum of squares method leads to the 95 % confidence intervals listed above in the table: just over 18 nm for the smallest range and around 0.2 µm for the other ranges. | The error stemming from the uncertainty on the calibration standard dominates for the 6.5 micron range, while for the other ranges the scatter of repeated measurements is also important. Using the sum of squares method leads to the 95 % confidence intervals listed above in the table: just over 18 nm for the smallest range and around 0.2 µm for the other ranges. | ||