Specific Process Knowledge/Characterization/Stylus Profiler Measurement Uncertainty: Difference between revisions
Created page with " =Stylus Profiler Measurement Accuracy= The accuracy of a height measurement with the profiler depends on the measurement settings, the sample, the instrument calibration and the resolution. ===Adjust Measurement Settings for your Sample=== Both the force setting and the scan speed are important: Too high force may compress a soft material like Al, Au or some polymers, while too low force may lead to the stylus "jumping" over features, especially if the scan speed is hi..." |
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[[File:intrinsic step h error.png|350px|upright=2|alt=Axes with Measured values versus expected values and three lines illustrating measured=expected, plus two not-quite straight lines illustrating the confidence intervals growing as the values grow constrained by the calibration standard measurements. Two diamonds illustrate the location of the calibration sample measurement points. The plot's title says "Error from intrinsic uncertainty step height used for calibration".|right|thumb|Figure 1: Measurement uncertainty from uncertainty in the calibration standard (Not to scale). The linearity of the sensor means that the measurement error increases approximately linearly with the size of the feature being measured. The percentage-wise error on the smallest standard step is larger than on the bigger standard step, meaning the lines are not completely straight.]] | [[File:intrinsic step h error.png|350px|upright=2|alt=Axes with Measured values versus expected values and three lines illustrating measured=expected, plus two not-quite straight lines illustrating the confidence intervals growing as the values grow constrained by the calibration standard measurements. Two diamonds illustrate the location of the calibration sample measurement points. The plot's title says "Error from intrinsic uncertainty step height used for calibration".|right|thumb|Figure 1: Measurement uncertainty from uncertainty in the calibration standard (Not to scale). The linearity of the sensor means that the measurement error increases approximately linearly with the size of the feature being measured. The percentage-wise error on the smallest standard step is larger than on the bigger standard step, meaning the lines are not completely straight.]] | ||
Nanolab staff check the instrument's measurement accuracy with a standard step height of | Nanolab staff check the instrument's measurement accuracy with a standard step height of 923 nm for the smaller ranges and 23.058 µm (previously almost 25 µm) for the larger ranges, so that the middle ranges are checked with both standards. The 95 % confidence intervals for the standards are 18 nm for the 917 nm standard and 0.068 µm for the 23.058 µm standard. If the control measurement is beyond the limit set in our Quality Control procedure, the instrument is calibrated and the users informed (see LabManager for details, for instance the Dektak XTA [http://labmanager.dtu.dk/d4Show.php?id=2493&mach=304 control instruction] and [https://labmanager.dtu.dk/view_binary.php?type=data&mach=304 control measurement data]) | ||
This means the 95 % confidence interval of a 1 µm step measured with the smallest measurement range is at least the 1.8 % error of the standard step while the 95 % confidence interval of a 25 µm step measured with a larger range is at least the 0.3 % error of the standard step. Steps between 1 and 25 µm measured with the intermediate ranges will presumably have an intermediate error ''just due to the intrinsic uncertainty on the standard step height''. See Figure 1. | |||
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