A model for the segregation and pileup of boron at the SiO2/Si interface during the formation of ultrashallow p+ junctions

Abstract

Approach to the characterization of through-oxide boron implantation by secondary ion mass spectrometryWe have quantitatively investigated how boron segregates to regions close to the surface, and what controls this phenomenon, using x-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and backside secondary ion mass spectrometry measurement techniques. We found that, contrary to the equilibrium segregation, the pileup of boron is mainly on and within 0.6 nm of the Si side of the interface, and that there is no difference between the kind of encapsulation. This also suggests that the pileup of boron is mainly on the Si side, and implies that the main factor in this segregation is the existence of the Si surface. From the viewpoint of device fabrication, this result seems to be useful in terms of the fabrication of sidewalls. The possibility of boron pileup to occurring in the interstitial state was also shown. Our results suggested a way of looking at dopant profiles by predictive computer modeling.

Uphill diffusion of ultralow-energy boron implants in preamorphized silicon and silicon-on-insulator

“…Under these experimental conditions, several mechanisms such as diffusion in amorphous Si ͑Ref. 5͒ and uphill diffusion [6][7][8][9][10][11][12][13] influence the dopant redistribution and activation. In particular, the surface ͑and the interfaces͒ affect the impurity profile through both the segregation and trapping of dopant atoms in energetically favorable places and acting on point defects distribution, and consequently, on the TED phenomena.…”

“…In particular, the surface ͑and the interfaces͒ affect the impurity profile through both the segregation and trapping of dopant atoms in energetically favorable places and acting on point defects distribution, and consequently, on the TED phenomena. These effects are particularly evident for boron [6][7][8][9] and phosphorous, 10,11 but have been also evidenced in ultrashallow junctions obtained by low-energy arsenic implantation. 12,13 A preferential diffusion of boron at high concentrations toward the surface against the concentration gradient has been recently observed by Wang et al 6 after ultralow-energy implants and low-temperature thermal cycles.…”

Boron pile-up phenomena during ultra shallow junction formation

“…The surface (and the interfaces) affect the impurity profile both through the segregation and trapping of dopant atoms in energetically favourite places and acting on point defects distribution, and consequently, on the TED phenomena. These effects are particularly evident for boron [5][6][7][8] and phosphorous [9,10], but have been also evidenced in ultrashallow junctions obtained by low energy arsenic implantation [11,12].…”

Surface control of interstitial behavior for improved ultrashallow junction formation

“…Matches of similar quality were obtained for other experimental data at different peak temperatures and ramp rates. that boron can exhibit apparent "uphill diffusion" behavior [28,29,30, 31, 32,331. In some cases, pile-up has been observed in the vicinity of a surface or interface [28,30,321 [34], probably caused by surface oxygen. However, Shima et al [28] employed SIMS conducted from the front and back sides of implanted specimens to conclude that the pile-up observed in their data within 0.6 nm of the surface was genuine.…”

“…that boron can exhibit apparent "uphill diffusion" behavior [28,29,30, 31, 32,331. In some cases, pile-up has been observed in the vicinity of a surface or interface [28,30,321 [34], probably caused by surface oxygen. However, Shima et al [28] employed SIMS conducted from the front and back sides of implanted specimens to conclude that the pile-up observed in their data within 0.6 nm of the surface was genuine. Such effects have been suggested to result from implantation-induced gradients in interstitial concentration due to localized interstitial clustering or related effects [29].…”