Now showing 1 - 3 of 3
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    Publication
    Extraction of True Finger Temperature from Measured Data in Multifinger Bipolar Transistors
    (01-03-2021)
    Gupta, Aakashdeep
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    Nidhin, K.
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    Balanethiram, Suresh
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    D'Esposito, Rosario
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    Fregonese, Sebastien
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    Zimmer, Thomas
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    In this brief, we propose a step-by-step strategy to accurately estimate the finger temperature in a silicon-based multifinger bipolar transistor structure from conventional measurements. First we extract the nearly zero-power self-heating resistances (Rth,ii (Ta)) and thermal coupling factors (cij (Ta)) at a given ambient temperature. Now, by applying the superposition principle on these variables at nearly zero-power, where the linearity of the heat diffusion equation is preserved, we estimate an effective thermal resistance (Rth,i (Ta)) and the corresponding revised finger temperature Ti (Ta). Finally, the Kirchhoff's transformation on Ti (Ta) yields the true temperature at each finger (Ti (Ta,Pd)). The proposed extraction technique automatically includes the effects of back-end-of-line metal layers and different types of trenches present within the transistor structure. The technique is first validated against 3-D TCAD simulation results of bipolar transistors with different emitter dimensions and then applied on actual measured data obtained from the state-of-the-art multifinger SiGe HBT from STMicroelectronics B5T technology. It is observed that the superposition of raw measured data at around 40 mW power underestimates the true finger temperature by around 10%.
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    Publication
    Optimizing Finger Spacing in Multifinger Bipolar Transistors for Minimal Electrothermal Coupling
    (01-12-2022)
    Gupta, Aakashdeep
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    Nidhin, K.
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    Balanethiram, Suresh
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    Yadav, Shon
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    Fregonese, Sebastien
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    Zimmer, Thomas
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    We present a compact modeling framework to optimize finger spacing for improving the thermal stability in multifinger bipolar transistors with shallow-trench isolation. First, we present an accurate physics-based model for total junction temperature in all the fingers of a transistor. Other than validating the model with 3-D TCAD simulations and measured data, we demonstrate its efficacy to achieve finger spacing optimization with the aid of an iterative algorithm. Since the proposed technique is scalable from the viewpoint of the number of fingers within a transistor and their geometries, the proposed framework is found to work seamlessly for various emitter finger numbers.
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    Publication
    An Efficient Thermal Model for Multifinger SiGe HBTs under Real Operating Condition
    (01-11-2020)
    Nidhin, K.
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    Pande, Shubham
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    Yadav, Shon
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    Balanethiram, Suresh
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    Nair, Deleep R.
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    Fregonese, Sebastien
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    Zimmer, Thomas
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    In this work, we present a simple analytical model for electrothermal heating in multifinger bipolar transistors under realistic operating condition where all fingers are heating simultaneously. The proposed model intuitively incorporates the effect of thermal coupling among the neighboring fingers in the framework of self-heating bringing down the overall model complexity. Compared to the traditional thermal modeling approach for an n-finger transistor where the number of circuit nodes increases as n2, our model requires only n-number of nodes. The proposed model is scalable for any number of fingers and with different emitter geometries. The model is validated with 3-D thermal simulations and measured data from STMicroelectronics B4T technology. The Verilog-A implemented model simulates 40% faster than the conventional model in a transient simulation of a five-finger transistor.