Distortion of sims profiles due to ion beam mixing: Shallow arsenic implants in silicon

Abstract

Secondary Ion Mass Spectroscopy (SIMS) is extensively used in microelectronics in order to measure the depth profiles of dopants in silicon wafers. During the SIMS analysis, the sputtering ion beam induces several mass transport processes (collisional mixing, radiationenhanced diffusion of the dopant atoms) which depend on ion beam characteristics (ion mass, energy, incident angle) and on atomic transport properties of the sample. The atomic transport leads to broader and shifted depth profiles in the measurements compared to the original ones. For a delta distribution of the analyzed impurity in depth, the signal of the SIMS apparatus leads to the response function; this function represents the distortion introduced by the measuring technique. In a first approximation, this response function is assumed to be independent of the initial depth profile. The resulting experimentally measured depth profile can be described as a convolution of the original undistorted profile and the SIMS response function. The SIMS distortion function associated with collisional mixing during SIMS analysis is calculated in the present work using a dynamic version of the TRIM program. As the depth dependence of the response function is important for SIMS analysis of shallow ion-implanted profiles of arsenic, this effect was taken into account to improve the precision of the SIMS profile modeling.

Measurement of Shallow Arsenic Impurity Profiles in Semiconductor Silicon Using Time‐of‐Flight Secondary Ion Mass Spectrometry and Total Reflection X‐Ray Fluorescence Spectrometry

“…The beam induced broadening and mixing of impurity layers will be constant at depths more than 5 to 8 nm. 8 At those depths, simulation of the broadening of delta layers showed a profile with exponential slope and a decay which is shifted by 1.5 nm toward the surface with respect to the delta layer and has a leading edge of 2.5 nm/dec and a trailing edge of 10 nm/dec. From this, it is expected that the true 500 eV As profile should show a higher surface concentration and a steeper slope of the profile.…”

“…Monte Carlo simulation of low energy sputtering has also shown severe distortions of profiles close to the surface by the sputtering beam. 8 A delta-type arsenic impurity layer located directly at the surface will be broadened by a 3 keV oxygen beam under an angle of 52 °leading to a step decay of approximately 1 dec/nm in the first 2 nm followed by a less steep decrease of 1 dec/5 nm. The beam induced broadening and mixing of impurity layers will be constant at depths more than 5 to 8 nm.…”

Diffusion kinetics of Cr in spinel: Experimental studies and implications for 53Mn–53Cr cosmochronology

“…The effect of ion beam mixing on diffusion profiles (e.g. Montandon et al, 2006) in the SIMS analysis, which is discussed below, was evaluated by conducting zero time experiments (ZTE) in which a dummy sample was analyzed under identical analytical conditions as employed for the samples from the diffusion experiments. This sample was prepared by depositing the diffusant material on a polished surface of a spinel crystal in the same way as in the diffusion experiments and annealing it at 900°C for 50 min, which is too short to induce significant Cr diffusion at this temperature.…”

Atomic mass spectrometry

“…The DRF was inadequate for highthe emission of species independent of their IP as a result of energy high-dose implanted As layers, analysed with a Cs+ the Coulomb explosion, which in turn was driven by the beam. Montandon et al 151 have studied the depth dependence release of numerous electrons from the local microvolume of the DRF by Monte Carlo simulations of the sputtering and upon the incident ion impact. The secondary ion yield the atomic collisional mixing, the theoretical implantation and decreased with increasing thickness of the silica layer on silicon the SIMS depth profile.…”