Nondestructive Depth Profile Analysis by Changing Escape Depth of Photoelectrons

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Abstract
Nondestructive depth profile analysis by changing the photoelectron escape depth was investigated at a soft X-ray beamline of the Photon Factory (KEK-PF). The escape depth was controlled by changing the energy of incident soft X-rays. The depth profile was determined from the observed photoelectron intensities based on the fact that the photoelectron intensity can be described by the Laplace transform of the depth profile. The oxidized silicon thin film on a silicon substrate was analyzed with this method, and depth profiles of SiO2 and Si were obtained. The depth resolution was 0.4 nm according to the 10-90% width of the transition region between the SiO2 and the Si. Improvement of depth resolution is discussed in terms of several simulations performed using a simple depth structure.