Study of submelt laser induced junction nonuniformities using Therma-Probe

Abstract

Submelt laser annealing is a promising technique to achieve the required sheet resistance and junction depth specifications for the 32 nm technology node and beyond. In order to obtain a production worthy process, it is important to minimize possible nonuniformities caused by the annealing process both at macroscopic and microscopic levels. In this work, the authors present high resolution Therma-Probe® measurements to assess the junction nonuniformity on 0.5 keV boron junctions and zoom in on the effect of temperature variations and multiple subsequent laser scans. The results are compared to standard and micro-four-point probe sheet resistance data, secondary ion mass spectrometry, and Hall measurements obtained during earlier studies. Besides the impact of the nonuniformities on the “conventional” thermal wave signal, they found a strong correlation to the dc reflectance of the probe laser (λ = 675 nm). The dc probe reflectance is dominated by free carriers and is highly correlated to the sheet resistance both on blanket wafers and on real device wafers.