Polysilicon emitters for bipolar transistors: a review and re-evaluation of theory and experiment

Post, Ian; Ashburn, P.; Wolstenholme, G.R.

doi:10.1109/16.141239

Cited by 104 publications

(47 citation statements)

References 62 publications

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“…In polysilicon emitters, the interfacial layer has a strong effect on the current gain [9]. It is therefore important to understand how the interfacial oxide thickness influences the base current increase obtained when germanium is introduced into the polysilicon emitter.…”

Section: Discussionmentioning

confidence: 99%

“…In practice, this could be achieved using an ex-situ HF etch in combination with polySiGe deposition in a cluster tool [15]. Even bigger effects could probably be achieved by breaking up the interfacial layer using an interface anneal prior to polySiGe deposition [9] or by epitaxially regrowing the polySiGe during the emitter anneal.…”

Section: Discussionmentioning

confidence: 99%

“…A theoretical expression is derived for the base current of a polySiGe emitter, and a comparison made with measured values on silicon bipolar transistors containing different amounts of germanium in the polysilicon. The competing mechanisms in polySiGe emitters of reduced gain from Ge incorporation and increased gain from the interfacial layer [9] are investigated.…”

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confidence: 99%

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Polycrystalline silicon-germanium emitters for gain control, with application to SiGe HBTs

Kunz

Groot

Hall

et al. 2003

IEEE Trans. Electron Devices

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Abstract-This paper investigates germanium incorporation into polysilicon emitters for gain control in SiGe heterojunction bipolar transistors. A theory for the base current of a polySiGe emitter is developed, which combines the effects of the polySiGe grains, the grain boundaries and the interfacial layer at the polySiGe/Si interface into an expression for the effective surface recombination velocity of a polySiGe emitter. Silicon bipolar transistors are fabricated with 0, 10 and 19% Ge in the polySiGe emitter and the variation of base current with Ge content is characterized. The measured base current for a polySiGe emitter increases by a factor of 3.2 for 10% Ge and 4.0 for 19% Ge compared with a control transistor containing no germanium. These values are in good agreement with the theoretical predictions. The competing mechanisms of base current increase by Ge incorporation into the polysilicon and base current decrease due to an interfacial oxide layer are investigated.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

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Polycrystalline silicon-germanium emitters for gain control, with application to SiGe HBTs

Kunz

Groot

Hall

et al. 2003

IEEE Trans. Electron Devices

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“…P OLYSILICON emitter contacts [1] have become a vital part of today's bipolar and BiCMOS technologies because they provide a means of realizing an exceptionally shallow Manuscript received June 24, 1999; revised August 17, 2000. This work was supported by the EPSRC through the award of a research contract and the Universiti Sains Malaysia through the award of a studentship.…”

Section: Introductionmentioning

confidence: 99%

Impact of ex-situ and in-situ cleans on the performance of bipolar transistors with low thermal budget in-situ phosphorus-doped polysilicon emitter contacts

Rahim

Marsh

Ashburn

et al. 2001

IEEE Trans. Electron Devices

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Abstract-This paper investigates the effects of an in-situ hydrogen bake and an ex-situ hydroflouric acid (HF) etch prior to polysilicon deposition on the electrical characteristics of bipolar transistors fabricated with low thermal budget in-situ phosphorusdoped polysilicon emitter contacts. Emitter contact deposition in a UHV-compatible low pressure chemical vapor deposition (LPCVD) cluster tool is also compared with deposition in a LPCVD furnace. Transmission electron microscopy (TEM) and secondary ion mass spectroscopy (SIMS) are used to characterize the emitter contact material and the interface structure and a comparison is made with Gummel plots and emitter resistances on bipolar transistors. The SIMS results show that an in-situ hydrogen bake in a cluster tool gives an extremely low oxygen dose at the interface of 6.3 10 13 cm 2 , compared with 7.7 10 14 and 2.9 10 15 cm 2 for an ex-situ HF etch and deposition in a cluster tool or a LPCVD furnace, respectively. TEM shows that the in-situ hydrogen bake results in single-crystal silicon with a high density of defects, including dislocations and twins. The ex-situ HF etch gives polycrystalline silicon for deposition in both a cluster tool and a LPCVD furnace. The single-crystal silicon emitter contact has an extremely low emitter resistance of 21 m 2 in spite of the high defect density and the light emitter anneal of 30 s at 900 C. This compares with emitter resistances of 151 and 260 m 2 for the polycrystalline silicon contacts produced using an ex-situ HF etch and deposition in a cluster tool or a LPCVD furnace, respectively. These values of emitter resistance correlate well with the interface oxygen doses and the structure of the interfacial oxide layer. The high defect density in the single-crystal silicon is considered to be due to the high concentration of phosphorus ( 5 10 19 cm 3 ) in the as-deposited layers.Index Terms-Bipolar transistor, cluster tool, in-situ doped polysilicon, polycrystalline silicon, polysilicon, polysilicon emitter.

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“…For many years, polycrystalline silicon has been a major contributor to the success of silicon integrated-circuit technology in applications such as gates for metal-oxidesemiconductor ͑MOS͒ transistors, 1 polycrystalline emitters for bipolar transistors, 2 and thin-film transistors for flat-panel displays. 3 More recently, considerable interest has been shown in polycrystalline SiGe films [4][5][6][7] because of lower growth temperatures, increased dopant activation, and the ability to tailor the MOS work function by adjusting the Ge concentration.…”

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confidence: 99%

Electrical properties of in situ phosphorus- and boron-doped polycrystalline SiGeC films

Anteney

Parker

Ashburn

et al. 2000

Applied Physics Letters

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The sheet resistance, effective carrier concentration, and Hall mobility of in situ boron-and phosphorus-doped polycrystalline Si 0.82Ϫy Ge 0.18 C y films are presented for carbon contents between 0% and 4%. Phosphorus and boron doping levels of 4ϫ10 19 and 2ϫ10 20 cm Ϫ3 were achieved for the n-and p-type layers, respectively, and remained largely unaffected by carbon content. The phosphorus-doped films showed a dramatic increase in sheet resistivity and a corresponding drop in effective carrier concentration and Hall mobility. In contrast, the boron-doped films showed only a minor increase in resistivity. This is attributed to interstitial carbon increasing the defect density and also shifting the defect energy levels at the grain boundaries towards the valence band. This causes an increase in the grain-boundary energy barrier in n-type layers, but leaves the p-type layers largely unaffected.

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Polysilicon emitters for bipolar transistors: a review and re-evaluation of theory and experiment

Cited by 104 publications

References 62 publications

Polycrystalline silicon-germanium emitters for gain control, with application to SiGe HBTs

Polycrystalline silicon-germanium emitters for gain control, with application to SiGe HBTs

Impact of ex-situ and in-situ cleans on the performance of bipolar transistors with low thermal budget in-situ phosphorus-doped polysilicon emitter contacts

Electrical properties of in situ phosphorus- and boron-doped polycrystalline SiGeC films

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