Wavelength, light, measurement accuracy

Optical radiation is distributed over time, position, direction, wavelength, and polarization, so field measurement accuracies within 10% are normal. There are over 30 potential sources of error in light measurement (D. Ryer, personal communication, 1983-1999), six of these sources involving optical error are considered foremost. 

This system employs a simultaneous film thickness measurement method, which incorporates a two-dimensional CCD camera detector , a variable wavelength light source, and an analyzer for the captured image data. With this configuration the system can, not only measure test pattern film thickness but also be used for a variety of visual wafer checks and film data inspections for Cu and other metal films during metal CMP. Moreover, we now have evidence that the system may even be able to handle moving wafers. With such potential, this system could evolve into a true In-Situ Monitor which measures film thickness inside the CMP unit itself with the same precision and accuracy. 

Emrich, M., Wameck, P. Photodissociation of acetone in air dependence on pressure and wavelength. Behavior of the excited singlet state. J. Phys. Chem. A 104, 9436-9442 (2000) Fahr, A., Braun, W., Kurylo, M. J. Scattered light and accuracy of the cross-section measurements of weak absorptions gas and liquid phase UV absorptitm cross sections of CH3CFCI2. J. Geophys. Res. 98, 20467-20472 (1993)... 

If we increase the accuracy with which the position of the electron is determined by decreasing the wavelength of the light that is used to observe the electron, then the photon has a greater momentum, since p = hiA. The photon can then transfer a larger amount of momentum to the electron, and so the uncertainty in the momentum of the electron increases. Thus any reduction in the uncertainty in the position of the electron is accompanied by an increase in the uncertainty in the momentum of the electron, in accordance with the uncertainty principle relationship. We may summarize by saying that there is no way of accurately measuring simultaneously both the position and velocity of an electron the more closely we attempt to measure its position, the more we disturb its motion and the less accurately therefore we are able to define its velocity. 

Table 20-1 gives the absorbance of a solution that you can prepare to test the accuracy of absorbance measurements on your spectrophotometer. Absorbance accuracy is affected by all components of the spectrophotometer, as well as stray light. Standards are also available to measure wavelength accuracy.9... 

In 1972 a 100-fold increase in the accuracy of the known speed of light was achieved by measuring the frequency of a helium-neon laser line in terms of the Cs time standard (Appendix Table A.2) and measuring its wavelength in terms of the Kr length standard. [K. M. Evenson et al., Phys. Rev. Letters, 29, 1346 (1972).] The improved value is... 

In ultraviolet, visible, and infrared spectroscopy, one usually measures the spectral line wavelengths (rather than frequencies), using a prism or diffraction grating. Until 1972, the speed of light was not known to very high accuracy, so it became traditional to convert measured wavelengths to reciprocal wavelengths 1 /A (rather than to frequencies) the quantity 1 /A is called the wave number. 

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