B segregation to grain boundaries and diffusion in polycrystalline Si with flash annealing

Abstract

Three-dimensional atom probe tomography was used to characterize the segregation of B dopant atoms to grain boundaries in polycrystalline Si after flash-assisted rapid thermal annealing. Tomographic reconstructions allowed direct measurement of segregation coefficients, which were found to be greater at lower flash temperatures with thermal budgets that limit grain growth. Hall measurements confirmed the deactivation of B at the grain boundaries, while secondary ion mass spectrometry was used to measure B diffusion in the film. Experimental parameters were then simulated in a diffusion model which accurately predicts the diffusion of B in polycrystalline Si at flash temperatures of 1150 C, 1250 C, and 1350 C, as well as with conventional rapid thermal annealing. V

Atom Probe Tomography Characterization of Dopant Distributions in Si FinFET: Challenges and Solutions

“…In contrast, atom probe tomography (APT) has exhibited its potential in characterizing 3D nanoscale semiconductor devices due to its high 3D spatial resolution and chemical sensitivity (Martin et al, 2016, 2018; Melkonyan et al, 2017; Barnes et al, 2018; Giddings et al, 2018). APT has recently been used in analyzing dopant distributions in polycrystalline Si or Si/SiO 2 interfaces (Ngamo et al, 2010; Jin et al, 2012; Han et al, 2015; Tu et al, 2017 a , 2017 b ), planar-type Si transistor devices (Inoue et al, 2009; Larson et al, 2011; Takamizawa et al, 2011) with high- k metal gate stacks (Panciera et al, 2012; Estivill et al, 2016), FinFET structures (Martin et al, 2016, 2018; Melkonyan et al, 2017), and gate-all-around structures (Grenier et al, 2014).…”

Selenium Segregation in Femtosecond-Laser Hyperdoped Silicon Revealed by Electron Tomography

“…Segregation has been studied using electron tomography at a larger scale for the identification of germanium precipitates in an Al-Ge alloy using HAADF-STEM (Kaneko et al, 2008) and for the studies of oxide precipitates in silicon using bright-field transmission electron microscopy (TEM) tomography (Schierning et al, 2011). Another frequently used method for studies of dopant segregation is atom probe tomography (Thompson et al, 2005; Duguay et al, 2010; Jin et al, 2012), but atom probe tomography is not suited for the present case due to the strong structural disorder caused by the doping process, which makes evaporation of the material difficult. For very small samples electron tomography has been shown to provide near-atomic resolution (Scott et al, 2012) and even atomic resolution in combination with prior assumptions about the object (Bals et al, 2010; Van Aert et al, 2011; Goris et al, 2012 a ).…”

“…tomography~Schierning et al, 2011!. Another frequently used method for studies of dopant segregation is atom probe tomography~Thompson et Duguay et al, 2010;Jin et al, 2012!, but atom probe tomography is not suited for the present case due to the strong structural disorder caused by the doping process, which makes evaporation of the material difficult. For very small samples electron tomography has been shown to provide near-atomic resolution~Scott et al, 2012!…”

Anomalous B diffusion profiles in nanocrystalline Si

“…However, such electrical effects have never been observed for dopant diffusion in GBs. Usually, dopants are not activated in GBs [17]. At point defect equilibrium, GB diffusion coefficients (D gb ) were found to be constant at given temperature, and for B diffusion in Si GBs D gb = 0.8 exp(À2.6 eV/k B T) cm 2 s À1 [15].…”

“…The results are in good agreement with the experimental profiles presented in Figure 1. B has been shown to segregate in Si GBs [17], and GB segregation is known to be able to prevent grain growth in polycrystalline layers, blocking or reducing GB migration [24]. Concentrations measured by SIMS in polycrystals correspond to the average concentration between the grains and the GBs at a same depth.…”