Mechanism of dopant segregation toSiO2/Si(001)interfaces

Abstract

Dopant atoms can segregate to SiO 2 /Si͑001͒ interfaces and be deactivated there. Using phosphorus as a typical example of a donor and guided by results of ab initio calculations, we present a model of donor segregation. We find that P is trapped at the interface in the form of threefold-coordinated atoms. The atomic detailed configuration and the process of P incorporation depend on P concentration C P in the vicinity of the interface. At low C P , phosphorus atoms prefer to substitute Si atoms with dangling bonds. At high C P , phosphorus pairs are formed. At intermediate C P , ͑around 10 17-10 19 cm Ϫ3 ͒ segregation occurs to sites associated with interface roughness and to interface Si-Si bridges, and is mediated by diffusion and annihilation of Si dangling bonds and by reoxidation during oxide annealing. Making diffusion of dangling bonds more difficult ͑for example, by nitridation͒ should, therefore, reduce the trapping efficiency of SiO 2 /Si͑001͒ in the technologically important regime of intermediate C P .

Advanced front-end processes for the 45nm CMOS technology node

“…A 10 s 1000 • C RTP step however does cause a major deactivation of the layer and increase in segregated Sb (62%) to nearly a monolayer. This concurs with recent theoretical predictions of maximum segregation for As and P [19]. It is also interesting to note that the dechanneling yield after the Si surface peak is constant for all three RTP steps.…”

Impurity segregation and ordering inSi/SiO2/HfO2structures

“…3͒ suggest that P does not segregate to the interface plane, where P-O bonds are energetically very costly, in agreement with previous results. 27,28 Instead, segregation is predicted to the subinterface Si plane with a small energy gain ͑0.16 eV͒. We also found that segregation of two isolated P dopants on this plane is always preferable against pair formation.…”

“…30 Pair formation is driven by the tendency of neutral dopant atoms to establish their preferred threefold coordination as in PH 3 and AsH 3 molecules. Pairing was also later suggested 27,28,31 to occur at the Si-SiO 2 interface in order to explain the observed dopant pile up for higher implanted doses. 27 We found that a nearest-neighbor P-P pair just below the interface plane lowers its energy ͑by 0.23 eV with respect to two isolated P dopants͒ by breaking the P-P bond ͑P-P distance of 3.28 Å͒ and achieving a threefold coordination for the two dopant atoms ͓Fig.…”

Influence of Dopants on Mechanical Properties of Steel: A Spin-Polarized Pseudopotential Study

“…In this work we used the spin-polarized version of DFT realized within the FHI96md package [6] based ont he density functional theory (DFT) [7,8] and the pseudo-potential method [9]. This package was previously used with advantage for many systems, including transition metal compositions [10][11][12][13][14]. In all cases, the generalized gradient approximation [15] to description of the exchange-correlation interactions has been chosen and the optimization of the atomic geometry has been performed.…”