Improved base current ideality in polysilicon emitter bipolar transistors due to fast fluorine diffusion through oxide

Schiz, J.; Ashburn, P.

doi:10.1049/el:19990479

Cited by 3 publications

(5 citation statements)

References 6 publications

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“…are lower than those of nonfluorinated devices. This improvement in I B due to the reduced nonideal base current component was reported for a larger number of samples in [12], [13] than studied here, and was attributed to suppression of recombination in the BE junction depletion regions at the oxide/silicon interface [9]- [14]. This suppression of IB by fluorine incorporation leads to improved gain, as shown in Fig.…”

Section: Device and Experimental Detailssupporting

confidence: 75%

“…The devices studied in this paper are self-aligned NPN BJTs with polysilicon emitters, fabricated in a simple conventional procedure [9], [12], [13]. The base and low-doped emitter (LDE) were produced by implanting boron and phosphorus, respectively, into (100) Czochralski n-on-n + epitaxial silicon wafers through an 80 nm screen oxide formed by a thermal oxidation in dry O2 at 1100 C. The phosphorus was implanted through an emitter window (EW) in photoresist.…”

Section: Device and Experimental Detailsmentioning

confidence: 99%

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Hot-carrier stressing of NPN polysilicon emitter bipolar transistors incorporating fluorine

Sheng

McKinnon

McAlister

et al. 2003

IEEE Trans. Electron Devices

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Abstract-The effects of fluorine on the hot-carrier induced degradation in low-thermal-budget polysilicon-emitter NPN bipolar transistors have been examined. Forward Gummel plots, base-emitter (BE) diode characteristics, and stress currents were measured during reverse BE bias stress. Fluorinated devices behave similarly under stress to nonfluorinated devices retaining the initial improvement observed in the forward-bias base current, which is due to suppression of recombination in the BE junction depletion regions at the oxide/silicon interface. The benefits of fluorination, and particularly the reduction in base current in fluorinated devices, appear to be robust-that is, there is no evidence that the defects passivated by fluorine are reactivated during stressing, or that fluorination introduces additional defects that are activated under stressing.

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Section: Device and Experimental Detailssupporting

confidence: 75%

Section: Device and Experimental Detailsmentioning

confidence: 99%

Hot-carrier stressing of NPN polysilicon emitter bipolar transistors incorporating fluorine

Sheng

McKinnon

McAlister

et al. 2003

IEEE Trans. Electron Devices

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“…The effect of the F implant on the base current could then be explained by passivation of the interface states by the F, as has been reported previously [15]. This passivation is likely to have occurred by F diffusion through the polysilicon and deposited oxide where the polysilicon overlaps onto the deposited oxide [22]. This is possible because F readily diffuses through polysilicon [23] and silicon dioxide [24].…”

Section: B Base Current Noisementioning

confidence: 57%

The influence of BF/sub 2/ and F implants on the 1/f noise in SiGe HBTs with a self-aligned link base

Lukyanchikova

Garbar

Petrichuk

et al. 2001

IEEE Trans. Electron Devices

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A study is made of 1 noise in SiGe heterojunction bipolar transistors (HBTs) fabricated using selective growth (SEG) of the Si collector and nonselective growth (NSEG) of the SiGe base and Si emitter cap. The transistors incorporate a self-aligned link base formed by BF 2 implantation into the field oxide below the p + polysilicon extrinsic base. The influence of this BF 2 implant on the 1 noise is compared with that of a F implant into the polysilicon emitter. Increased base current noise S IB and base current are seen in transistors annealed at 975 C, compared with transistors annealed at 950 or 900 C. At a constant collector current, both the BF 2 and F implants reduce S IB , whereas at a constant base current, only the BF 2 implant reduces S IB. This result indicates that the BF 2 implant decreases the intensity of the base current noise source whereas the F implant decreases the base current. The proposed explanation for the increased 1 noise is degradation of the surface oxide by viscous flow at 975 C under the influence of stress introduced during selective Si epitaxy. The influence of the BF 2 implant on the noise is explained by the relief of the stress and hence the prevention of viscous oxide flow.

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“…Fluorine has additional benefits in polysilicon emitter bipolar transistors, including reduced 1/ f noise [6] and improved base current ideality [5]. The improved 1/ f noise occurs because the fluorine breaks up the interfacial oxide layer, which is a source of noise in polysilicon emitters.…”

Section: Effect Of Fluorine In Polysilicon Emittersmentioning

confidence: 99%

“…In bipolar technologies, a BF + 2 implant was also used to create p-n-p polysilicon emitters and this led to a study of the behaviour of fluorine in polysilicon emitters [4]. This work showed that fluorine influenced a number of key bipolar transistor parameters, including gain [4], base current [5] and 1/ f noise [6,7]. More recently, research has focussed on the effect of fluorine on boron diffusion and it has been shown that fluorine suppresses boron transient enhanced diffusion [8,9] and increases boron activation in silicon [8].…”

Section: Introductionmentioning

confidence: 99%

Properties and benefits of fluorine in silicon and silicon-germanium devices

Ashbur,

A. W. El Mubarek

2007

JTIT

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This paper reviews the behaviour of fluorine in silicon and silicon-germanium devices. Fluorine is shown to have many beneficial effects in polysilicon emitter bipolar transistors, including higher values of gain, lower emitter resistance, lower 1/f noise and more ideal base characteristics. These results are explained by passivation of trapping states at the polysilicon/silicon interface and accelerated break-up of the interfacial oxide layer. Fluorine is also shown to be extremely effective at suppressing the diffusion of boron, completely suppressing boron transient enhanced diffusion and significantly reducing boron thermal diffusion. The boron thermal diffusion suppression correlates with the appearance of a fluorine peak on the SIMS profile at approximately half the projected range of the fluorine implant, which is attributed to vacancy- fluorine clusters. When applied to bipolar technology, fluorine implantation leads to a record fT of 110 GHz in a silicon bipolar transistor.

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Improved base current ideality in polysilicon emitter bipolar transistors due to fast fluorine diffusion through oxide

Cited by 3 publications

References 6 publications

Hot-carrier stressing of NPN polysilicon emitter bipolar transistors incorporating fluorine

Hot-carrier stressing of NPN polysilicon emitter bipolar transistors incorporating fluorine

The influence of BF/sub 2/ and F implants on the 1/f noise in SiGe HBTs with a self-aligned link base

Properties and benefits of fluorine in silicon and silicon-germanium devices

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