Nondestructive one-dimensional scanning capacitance microscope dopant profile determination method and its application to three-dimensional dopant profiles

Abstract

In this article, we present a new one-dimensional (1D) dopant profile determination method, which extends to the quantitative three-dimensional (3D) dopant profile extraction. This nondestructive method, which is different from the common scanning capacitance microscopy (SCM) measurement/dopant extraction, can potentially measure real metal–oxide–semiconductor field-effect transistor devices having 3D structure. Through SCM modeling, we found that the depletion layer in silicon was of a form of a spherical capacitor with the SCM tip biased. Two-dimensional (2D) finite differential method code with a successive over relaxation (SOR) solver has been developed to model the measurements by SCM of a semiconductor wafer that contains an ion-implanted impurity region. Then, we theoretically analyzed the spherical capacitor and determined the total depleted-volume charge Q, capacitance C, and the rate of capacitance change with bias dC/dV. It is very important to observe the depleted carriers’ movement in the silicon layer by applying the bias to the tip. So, we calculated the depleted-volume charge, considering different factors such as tip size, oxide thickness, and applied bias (dc+ac), which have an influence on potential and depletion charges. Finally, we developed a 1D inversion algorithm to convert the SCM output (dC/dV) into real dopant concentration, comparing the SCM signal output with the calculated dC/dV. Using the inversion modeling, we have quantitatively extracted the 1D dopant profile from the SCM dC/dV vs V curves.