Metrology for Implanted Si Substrate Loss Studies

Abstract

A spectroscopic ellipsometry (SE) model was developed and implemented to study substrate loss in shallow implanted silicon (i-Si) substrates following a photoresist strip. The model is based on different optical properties of silicon dioxide (SiO2) and i-Si layers and silicon substrates and is used to characterize relevant layers, i-Si and SiO2 , before and after plasma treatment. An increase in SiO2 and a decrease in the i-Si layer were observed after plasma exposure. Changes in the i-Si layer are the result of two phenomena, oxidation and heating-induced regrowth of the i-Si layer, while changes in the SiO2 thickness represent the direct measure of substrate loss due to oxidation. Transmission electron microscopy (TEM) and secondary-ion mass spectrometry (SIMS) analysis were performed to cross-check the validity and accuracy of the SE model. The TEM results confirm that the SE model can distinguish between a crystalline (c-Si) substrate and an i-Si layer regardless if the i-Si is damaged, crystalline, or amorphized. There is also good consistency between the SE and SIMS results. For the plasma processes studied in this work, minimal changes in layer thicknesses and substrate losses measured by SE agree very well with the measured SIMS dopant profiles.

Metrology and Measurement Systems

“…In the most common case of the implantation of the crystalline material at a relatively high energy (more than 10 keV), amorphization of the implanted area occurs and, obviously, the amorphous medium has very different optical properties from the crystalline one. However, as was recently shown, even in the case of low energy ion implantation (around 1 are keV), where no amorphization is observed, implantation-induced damages change optical constants of the media which, thanks to their high precision, can be observed with ellipsometry [45][46][47].…”

Spectroscopic Ellipsometry of Ion-Implantation-Induced Damage

“…At such low energies Si might not be amorphized but only damaged. However, recently published papers Radisic et al, 2009Radisic et al, , 2010 demonstrated that spectroscopic ellipsometry can be used for implanted Si measurements even in the case of low energy ion implantation, when no Si amorphization is observed.…”

Characterization of Arsenic Ultra-Shallow Junctions in Silicon Using Photocarrier Radiometry and Spectroscopic Ellipsometry

“…Photocarrier radiometry (PCR) [1,2] and spectroscopic ellipsometry (SE) [3,4] have been widely used in the characterization of ion-implanted wafers at high implantation energy. However, only a few investigations [5,6] were carried out with SE measurements in the visible range for the as-implanted USJ wafers. In this study, SE with a spectral range from 0.27 μm to 20 μm and PCR are employed to measure the As + -implanted USJ wafers, before annealing and after spike annealing.…”