Specific Process Knowledge/Characterization/Stylus Profiler Measurement Uncertainty: Difference between revisions
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KLA, the manufacturer of the P17 profiler, provides some information on the flatness one can expect from the scans, some of which is freely available in [https://www.kla.com/wp-content/uploads/KLA_AppNote_Stylus_2D_Stress.pdf this document]. Here we see that we can expect a variation of up to 40 nm across a flat scan of 3 cm. Thus the variation of up to 40 nm across 2 cm that we have seen in practice is not far beyond the presumably best-case scenario stated by the manufacturer (our tool could use some lubrication of the scan axes at the time of measurement). | KLA, the manufacturer of the P17 profiler, provides some information on the flatness one can expect from the scans, some of which is freely available in [https://www.kla.com/wp-content/uploads/KLA_AppNote_Stylus_2D_Stress.pdf this document]. Here we see that we can expect a variation of up to 40 nm across a flat scan of 3 cm. Thus the variation of up to 40 nm across 2 cm that we have seen in practice is not far beyond the presumably best-case scenario stated by the manufacturer (our tool could use some lubrication of the scan axes at the time of measurement). | ||
For the P17 the underlying scan noise or bow is extremely reproducible for many scans in the same position whether or not the vacuum hold is turned on. Therefore it seems that the non-flatness of the scans derive from some underlying structure on the optically flat surface or the scan rails. | For the P17 the underlying scan noise or bow is extremely reproducible for many scans in the same position whether or not the vacuum hold is turned on. However the underlying noise varies when measuring different locations on a blank wafer. Therefore it seems that the non-flatness of the scans derive from some underlying structure on the optically flat surface or the scan rails. | ||
For the Dektaks, we have in some cases seen that the scan noise is reproducible not only for scans in the same location, but even for scans in different locations on the stage, which must be due to | For the Dektaks, we have in some cases seen that the scan noise is reproducible not only for scans in the same location, but even for scans in different locations on the stage, which must be due to dust or bumps on the "feet" of the stage as they move across the optical flat. However in other cases, as in all scans shown in the document above, the bowing/noise of the scan varies even though the scan coordinates and sample are the same. The latter might be because the stage positioning is a little less accurate than for the P17 or because there is more environmental noise influencing the measurement. | ||
===How does the underlying scan noise affect the measurement accuracy?=== | ===How does the underlying scan noise affect the measurement accuracy?=== | ||