Localized Enhanced Diffusion in NPN Silicon Structures

Gereth, R.; Loon, P. G. G. van; Williams, Victoria Ann

doi:10.1149/1.2423532

Cited by 33 publications

(29 citation statements)

References 8 publications

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“…Since _Axj outside the emitter (nonpushed-out base) is negligible, under the emitter ~xj ~ 6 [see Fig. Equation [5] is basically the same as Eq. In the boron push-out work described above xj was 2.0 ~m and ~ had a maximum value of 0.3 ~m, while in the gallium push-out vs. te results xj was 1.5 ~m and ~ had a maximum value of 0.6 ~m so that the condition ~xj << xj was barely met in these cases.…”

Section: Discussionmentioning

confidence: 99%

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Studies of the Push‐Out Effect in Silicon: I . Comparison of Sequential Boron‐Phosphorus and Gallium‐Phosphorus Diffusions

Jones¹,

Willoughby²

1975

J. Electrochem. Soc.

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The push-out effect in silicon has been investigated by comparing the effect of similar phosphorus emitter diffusions on previously diffused boron and gallium base diffusions, using junction depth and electrical measurements. The closely similar behavior of the two base dopants suggests that both diffuse by the same mechanism in silicon, despite their different covalent radii. For both dopants the amount of push-out increases with emitter diffusion time for constant base diffusion and emitter surface concentration, and decreases as base depth increases for constant emitter diffusion and base surface concentration, and it is concluded that push-out occurs during the emitter diffusion rather than during cooling. The results are discussed with reference to an approximate theory, and agreement between experiment and this theory strongly suggests that push-out is due to a uniform enhancement of the base diffusivity throughout the emitter diffusion period. This study, using junction depth and electrical profiling techniques only, is the first part of this investigation, the second of which will report results of a radiotracer study of push-out.

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Section: Discussionmentioning

confidence: 99%

“…[5] by assuming that after drive-in and before the emitter diffusion the base is given by N ----Nbo exp (--X2/4Db~b) an assumption which is valid when the diffusion length for the drive-in is much larger than for the deposition step. This is avoided in Eq.…”

Section: (It) Equation [4] Contains a Characteristic Constantmentioning

confidence: 99%

Studies of the Push‐Out Effect in Silicon: I . Comparison of Sequential Boron‐Phosphorus and Gallium‐Phosphorus Diffusions

Jones¹,

Willoughby²

1975

J. Electrochem. Soc.

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“…'s work is its dismissal of the claim by Gereth el al. 17 that the emitter-push effect occurred predominantly during cooling.…”

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confidence: 95%

Reply to ``Discussion on `Approximate Theory of Emitter-Push Effect' ''

Yeh

1971

Journal of Applied Physics

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“…Thus, when EF ----Ec --0.11 eV P+V=~----P+V-+e-~----P++V--Se - [15] will be favorable as the V = vacancy loses an electron to the conduction band, and in its new charge state the PeV-pair is more likely to dissociate. The mass action equation at n = ne for the reaction in Eq.…”

Section: Nd = Ktmentioning

confidence: 99%

“…[13]. In order to account for the fact that reaction [12] also is generating V = vacancies which give up an electron to become Vvacancies, and that reaction [15] is exp (0.3 eV/kT) times more probable than [12], the total concentration of generated V-vacancies becomes…”

Section: Cv-mentioning

confidence: 99%

A Quantitative Model for the Diffusion of Phosphorus in Silicon and the Emitter Dip Effect

Fair¹,

Tsai²

1977

J. Electrochem. Soc.

327

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A consistent model of P diffusion in Si is presented which accounts quantitatively for the existence of electrically inactive P, the "kink" and the tail regions of the P profile, and the emitter dip effect. In this model it is shown that three intrinsic P diffusion coefficients exist, each one associated with the diffusion of P with vacancies in three different charge states. In the so-called "anomalous" high concentration region of the profile (n ~ 10 2~ cm-a), it is shown that equilibrium concentration of P+V = pairs dominates P diffusion and P electrical activity. At lower electron concentrations when the Fermi level is ,~0.11 eV below the conduction band, the V = vacancy gives up an electron, and the 0.3 eV lower binding energy of the resulting P+V-pairs enhances the probability for pair dissociation by a factor of 10-35, depending on the temperature. This effect creates a steady-state excess concentration of Vvacancies which flow away from the point of pair dissociation. The concentration of excess V-vacancies created is proportional to the number of P +V = pairs created at the Si surface times the enhanced probability for pair dissociation. These vacancies in the V-charge state interact with P to create the enhanced tail diffusion. In a npn structure, the charge state of the excess vacancies becomes V + in the base region, thus enhancing the diffusivity of the base dopant and causing the emitter dip effect. The magnitude by which the P tail diffusivity and the base dopant diffusivity are enhanced is the same and may reach a factor of 135 for a 900~ diffusion.At high concentrations the diffusion of phosphorus (P) into silicon (St) produces an impurity atom distribution that differs considerably from the Gaussian or complementary error-function distributions (I-7). Numerous models have been proposed to explain this anomalous deviation from simple diffusion theory. Lawrence (8) suggested that the retardation of P diffusion was a result of the precipitation of P at moving dislocations. Dash and Joshi similarly postulated that the onset of anomalous P diffusion occurred simultaneously with the generation of dislocations in the Si lattice, at a critical integrated P concentration (9). However, the recent results of Sato et al. (10) disagree with this model, and Duffy et al. (11) found no evidence of dislocations or precipitation following the predeposition of prominently kinked P profiles. Significant numbers of dislocations and accompanying preCipitation occur only after the drive-in cycle (11).Other P diffusion models include the saturated lattice site model of Bakeman and Borrego (12), the thin surface barrier model of Makris et al. (13), impurity band effects on the electron activity coefficient (10, 14), the existence of a molten Si-P phase to explain the apparent flattened region of the P profile (15), and That's model of enhanced diffusion due to plastic deformation and subsequent generation of excess vacancies (16, 17). All of the above models have been criticized by Hu in a recent review (18), and so ad...

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Localized Enhanced Diffusion in NPN Silicon Structures

Cited by 33 publications

References 8 publications

Studies of the Push‐Out Effect in Silicon: I . Comparison of Sequential Boron‐Phosphorus and Gallium‐Phosphorus Diffusions

Studies of the Push‐Out Effect in Silicon: I . Comparison of Sequential Boron‐Phosphorus and Gallium‐Phosphorus Diffusions

Reply to ``Discussion on `Approximate Theory of Emitter-Push Effect' ''

A Quantitative Model for the Diffusion of Phosphorus in Silicon and the Emitter Dip Effect

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