Oxidation of silicon by a low-energy ion beam: Experiment and model

Todorov, S. S.; Fossum, E. R.

doi:10.1063/1.99313

Cited by 37 publications

(5 citation statements)

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“…Results of depth profiling experiments were not taken into account. It was claimed that there is good agreement with results of the I-S model of beam induced oxidation (Todorov & Fossum 1988). However, a closer look at the simulated oxide profiles shows that there is complete disagreement in such important details as the width of the interface.…”

Section: O D Ellin G O F Bom B Ard M En T Ind Uced Ox Id a Tio N And Surface M Ovem En Tmentioning

confidence: 84%

“…This is equivalent to the idea that all the implanted oxygen immediately reacts with sil icon to form S i02, an assumption often made in modelling beam induced oxidation oxygen energy / keV atom 1 10"' 1 10 102 (W ittm aack 1996a, 6); Vc92 (V ancauw enberghe 1992); Vv94 (V andervorst et al 1994); D90 (Dowsett et al 1994); H81 (Hayashi et al 1981). (Todorov & Fossum 1988). In either case it suffices to know F?si and i?si02> and to consider Qox a short-form term for a difference in volume:…”

Section: O D Ellin G O F Bom B Ard M En T Ind Uced Ox Id a Tio N And Surface M Ovem En Tmentioning

confidence: 99%

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Transient phenomena and impurity relocation in SIMS depth profiling using oxygen bombardment: pursuing the physics to interpret the data

1996

Phil. Trans. R. Soc. Lond. A

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High detection sensitivity in bulk analysis or depth profiling by secondary ion mass spectrom etry (SIMS) can only be achieved, for positively charged ions, if the near surface regions of the sputter eroded sample are fully oxidized. Using oxygen prim ary ions, a stationary oxidation state is established after some tim e of bom bardm ent during which period the sputtering yield decreases and the ionization probability increases. The physical and chemical processes occurring during the transient period are reviewed w ith emphasis on the results for im purity analysis in silicon, i.e. the m atrix m aterial th a t has been studied most thoroughly in the past. The transient de crease in sputtering yield gives rise to a depth scale offset and an associated apparent shift of im purity profiles towards the surface. The effect is largest at normal beam incidence, ca. 1 nm/keVXOf), in which case silicon is fully oxidized. The transition depth, i.e. the depth sputtered before achieving a stable ion yield is about twice as large and increases as the im pact angle is turned away from normal. The shift and the depth scale offset can be measured safely using thin (delta) layers of isotopically pure tracers, for example 30Si in 28Si. Boron delta layers can serve as secondary standards because this im purity behaves almost the same as the host silicon atoms. The profile shift observed w ith other common dopants may contain contributions due to unidirectional relocation, often driven by segregation away from the surface. At O j energies below about 0.7 keV the transition depths fall below the thickness of typical native oxides, so th a t the transient changes in sputtering yield and ionization probability can disappear. The transient phenomena may be described by a simple sputtering-oxidation model th a t connects the depth scale offset to other observable param eters like the initial and final sputtering yield, the transition fluence and the oxide thickness. I n tr o d u c tio nOver the past 20 years secondary ion mass spectrom etry (SIMS) has been used quite successfully for depth profiling im purity distributions in solids. Most of the previous work has been done on semiconductor samples which constitute the m ajor challenge to the SIMS technique because of the need for high sensitivity in combination with high precision (Wilson et al. 1989). The excellent sensitivity reported for many ele ments is based on two characteristic features of SIMS: first, the absence of an inherent

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Section: O D Ellin G O F Bom B Ard M En T Ind Uced Ox Id a Tio N And Surface M Ovem En Tmentioning

confidence: 84%

Section: O D Ellin G O F Bom B Ard M En T Ind Uced Ox Id a Tio N And Surface M Ovem En Tmentioning

confidence: 99%

Transient phenomena and impurity relocation in SIMS depth profiling using oxygen bombardment: pursuing the physics to interpret the data

1996

Phil. Trans. R. Soc. Lond. A

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“…In other words, layer-by-layer oxidation did not occur. Second, the atomic oxygen or oxygen ions in the plasma may have impinged on the Si surface, so that Si atoms were sputtered [17][18][19].…”

Section: Resultsmentioning

confidence: 99%

Ultrathin oxide film formation using radical oxygen in a UHV system

1999

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Radical oxidation at thickness of under 2.0 nm in an ultrahigh vacuum (UHV) system with an electron cyclotron resonance (ECR) plasma has been studied. The interface roughness and oxide density were evaluated by atomic force microscopy (AFM) and grazing incidence xray reflectrometry, respectively. We found the oxide thickness could be easily controlled at Tsub = 750'C when using radical oxygen at 5.0x10 3 Torr. The interface roughness at a thickness of 1.8 nm, measured by the root mean square (RMS), was 0.11 nm. The density of the radical oxide fell as the oxide thickness decreased, especially at less than 2.0 nm. However, the density of the radical oxide annealed in molecular oxygen at 5x10-3 Torr and TSUb = 750'C increased, without the oxide thickness increasing. We think that the first insertion of an oxygen atom into the first Si layer has a much higher energy barrier than that into a SiO. layer. The radical oxygen can pass through this higher energy barrier, and thus oxygen molecules fill the oxide layers.This mechanism means that we can control the oxide thickness and density separately at thickness of less than 2.0 nm through the radical oxidation time and the annealing time in molecular oxygen. We expect low-pressure radical oxidation to be the most suitable process for future ultrathin gate oxidation.

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“…It may be assumed that a competition between incorporation and removal mechanisms insures the self-limiting growth of the C, F-overlayer. It is known from implantation-sputtering models that the initially broad interface becomes more sharp as the steady state of the topmost layer is reached [29]. However the silicon nearsurface was modified up to a critical dose D2, as demonstrated both by ellipsometry and contact electrical evaluation of as-cleaned samples.…”

Section: Discussionmentioning

confidence: 96%