The thermal stability of SiGe films deposited by ultrahigh-vacuum chemical vapor deposition

Stiffler, S. R.; Comfort, J.H.; Stanis, C.; Harame, D.L.; Fresart, E. de; Meyerson, B.S.

doi:10.1063/1.349551

Cited by 43 publications

(16 citation statements)

References 32 publications

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“…1. Stiffler et al's [6] stability curve shown in the same figure is an empirical result for the critical thickness in strained UHVICVD SiGe epitaxial films. For any given effective thickness of the epitaxial SiGe film, the film will be unconditionally stable (defect free) if the amount of Ge introduced into the film is below the critical limit (lower left region of the figure) and for Ge content above this critical limit a metastable film will result.…”

Section: Resultsmentioning

confidence: 72%

Optimization of Early Voltage for Cooled SiGe HBT Precision Current Sources

1996

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Abstract:The influence of Ge profile shape on the temperature characteristics of two key analog transistor parameters, Early voltage (VA) and current gain-Early voltage product (PVA), in SiGe HBTs have been studied over the temperature range of 300K-77K using SCORPIO, a transistor simulation tool calibrated to measured data [I]. A new version of SPICE that accounts for the temperature dependence of V, was used to model the various SiGe HBTs simulated and thereby evaluate the cryogenic performance of SiGe HBT precision current sources, which are strongly influenced by the variations in both P and VA. Results clearly indicate that the cryogenic performance of these SiGe current sources can be significantly improved by using a graded Ge profile instead of a constant Ge profile in the base region of the HBT.

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Section: Resultsmentioning

confidence: 72%

Optimization of Early Voltage for Cooled SiGe HBT Precision Current Sources

1996

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“…4 illustrates the SiGe profile design tradeoffs. The solid profile and the dash profile have the same integrated Ge content, the upper limit of which is set by the SiGe film stability constraint [18]. The dashed profile has a larger Ge content and a higher Ge gradient in the base, and therefore higher and , and hence lower noise.…”

Section: Sige Profile Designmentioning

confidence: 99%

“…5 shows two such low-noise Ge profiles (LN1 and LN2) which maintain the stability, the peak and peak of the SiGe control profile, but have significantly lower in simulation (by 0.2 dB). All of the SiGe profiles are unconditionally stable to defect generation [18], [] by design, as shown in Fig. 6.…”

Section: Sige Profile Designmentioning

confidence: 99%

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Noise modeling and SiGe profile design tradeoffs for RF applications [HBTs]

Niu

Zhang²,

Cressler³

et al. 2000

IEEE Trans. Electron Devices

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This paper investigates SiGe profile design tradeoffs for low-noise RF applications at a given technology generation (i.e., fixed minimum feature size and thermal cycle). An intuitive model relating structural parameters and biases to noise parameters is used to identify the noise limiting factors in a given technology. The noise performance can be improved by pushing more Ge into the base and creating a larger Ge gradient in the base. To maintain the SiGe film stability, the retrograding of the Ge into the collector has to be reduced, leading to a stronger roll-off at high injection. Two low-noise profiles were designed and fabricated explicitly for improving minimum noise figure () without sacrificing gain, linearity, frequency response, or the stability of the SiGe strained layer. A 0.2 dB was achieved at 2.0 GHz with an associated gain () of 13 dB.

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“…Even though the complete expression is used in our calculations, a simplified version accounting only for the dominant terms can be expressed as (11) This formulation helps in determining which parameters are controlling the noise factor. Generally speaking, the presence of Ge reduces the noise factor by decreasing , decreasing (through , and allowing nearly independent control of is given by when is set to the optimum source resistance is given by (12) where the optimum source reactance is given by (13) and (14) Accounting only for the dominant terms, these equations simplify to (15) …”

Section: Noise Modelmentioning

confidence: 99%

Base-profile optimization for minimum noise figure in advanced UHV/CVD SiGe HBT's

Ansley

Cressler

Richey³

1998

IEEE Trans. Microwave Theory Techn.

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We investigate the base-profile design issues associated with optimizing ultrahigh vacuum/chemical vapor deposition (UHV/CVD) silicon-germanium (SiGe) heterojuction bipolar transistors (HBT's) for minimum broad-band noise. Using the simulator for cryogenic research and SiGe bipolar device optimization (SCORPIO), the impact of Ge profile, base doping level, and base thickness on minimum noise figure (NFmin) are quantitatively examined across the 055 C-125 C temperature range.We introduce a novel Ge profile for optimum NFmin, which allows independent control of current gain () and achieves maximum fT while maintaining thermodynamic stability. Simulations show that this profile can achieve a of 200, a peak fT > 50 GHz, a peak fmax > 60 GHz, and an NFmin < 0.5 dB at 2 GHz and <1 dB at 10 GHz using a conservative base width of 90 nm.We predict that a 45-nm base-width/0.5-m emitter-width device with a thermodynamically stable flat Ge profile, manufacturable using an UHV/CVD growth technique, should be able to achieve an NF min < 0.4 dB at 2 GHz and 0.8 dB at 10 GHz along with a of 300, a peak f T > 70 GHz, and a peak f max > 90 GHz.These 300-K performance values improve as the temperature is reduced.

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The thermal stability of SiGe films deposited by ultrahigh-vacuum chemical vapor deposition

Cited by 43 publications

References 32 publications

Optimization of Early Voltage for Cooled SiGe HBT Precision Current Sources

Optimization of Early Voltage for Cooled SiGe HBT Precision Current Sources

Noise modeling and SiGe profile design tradeoffs for RF applications [HBTs]

Base-profile optimization for minimum noise figure in advanced UHV/CVD SiGe HBT's

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