Physical insight into boron activation and redistribution during annealing after low-temperature solid phase epitaxial regrowth

Abstract

Kinetic Monte Carlo simulations of B diffusion and activation in preamorphized Si during annealing after solid phase epitaxial regrowth have been used to provide insight into the mechanisms that drive these phenomena. Simulations show that the presence of an initially high active B concentration along with a Si interstitial supersaturation set by end of range defects leads to simultaneous B deactivation and uphill diffusion through the capture of mobile interstitial B in the high concentration region during subsequent anneal treatments. Once the Si interstitial supersaturation decays close to equilibrium values, B clusters dissolve and emitted B diffuses downhill, following the B concentration gradient. The active B concentration at the minimum state of activation becomes higher as the annealing temperature increases as a consequence of a faster increase of the B cluster dissolution rate compared with the formation rate.

Atomistic analysis of B clustering and mobility degradation in highly B‐doped junctions

“…are electrically active) after the regrowth, according to experimental data [6,7]. Moreover, we consider that B concentrations above that value are in the form of small BICs, in agreement with theoretical calculations [8] and previous work [9][10][11]. Although there is still no agreement on the particular configurations of max $2 Â 10 20 cm À3 are considered electrically active [2,3] whereas B concentrations above that value are stored in small BICs [2][3][4][5][6][7][8].…”

“…During post-regrowth annealing, B deactivation and subsequent reactivation, as well as B redistribution, have been reported [6,7,10]. As discussed in previous works [9,10], Si interstitials emitted from end-of-range (EOR) defects (that remain beyond the amorphous/crystalline interface after SPER) interact with the B profile, leading to some growth of preexisting BICs and resulting in the observed B deactivation. Moreover, we have shown recently that even if EOR defects are deep enough to avoid the interaction between EOR defects and the B profile, slight B deactivation also takes place, due to thermally generated equilibrium Si interstitials [11].…”

“…On the other hand, KMC codes allow the simulation of the annealing step by only handling dopant atoms and lattice defects and their interactions [1,3,[9][10][11][13][14][15]. Parameters that define these interactions, such as diffusivities, binding energies, capture radius, etc., must be specified.…”

“…The use of a very refined grid and the addition of new equations slow down the resolution of the problem using continuum methods. Then, atomistic simulation techniques, which traditionally have been just used to extract continuum model parameters, become a good alternative even for industrial applications [1,3,[9][10][11][13][14][15].…”

“…Higher B concentrations lead to the formation of some BICs in the amorphous region and remain electrically inactive after SPER [6][7][8][9]. During post-regrowth annealing, B deactivation and subsequent reactivation, as well as B redistribution, have been reported [6,7,10]. As discussed in previous works [9,10], Si interstitials emitted from end-of-range (EOR) defects (that remain beyond the amorphous/crystalline interface after SPER) interact with the B profile, leading to some growth of preexisting BICs and resulting in the observed B deactivation.…”