A Back-Wafer Contacted Silicon-On-Glass Integrated Bipolar Process—Part II: A Novel Analysis of Thermal Breakdown

Abstract

Abstract-Analytical expressions for the electrothermal parameters governing thermal instability in bipolar transistors, i.e., thermal resistance TH , critical temperature crit and critical current C crit , are established and verified by measurements on silicon-on-glass bipolar NPNs. A minimum junction temperature increase above ambient due to selfheating that can cause thermal breakdown is identified and verified to be as low as 10-20 C.The influence of internal and external series resistances and the thermal resistance explicitly included in the expressions for crit and C crit becomes clear. The use of the derived expressions for determining the safe operating area of a device and for extracting the thermal resistance is demonstrated.

Scaling influence on the thermal behavior of toward-THz SiGe:C HBTs

“…As a result, the V BE -T B curve coincides with the V BEj -T j one, and ϕ can be obtained from its slope. By repeating the extraction procedure for various I E values, it was found that ϕ logarithmically depends on I E (almost equal to the II-free I C ), as already found for GaAs [11] and Si [12] bipolar transistors, as well as for SiGe:C devices fabricated by STMicroelectronics [8]. This dependence can be described by the following relationship:…”

“…Parameter ϕ 0 -an expression of which as a function of device parameters can be derived from the analysis developed in [12] -was determined by fitting (4) with the experimental ϕ vs. I E data.…”

Extraction and modeling of self-heating and mutual thermal coupling impedance of bipolar transistors

“…From the characteristics at the collector currents of interest, the base-emitter voltage temperature coefficient (4) can be extracted. It is demonstrated in [7] that the coefficient is temperature independent and therefore the measured changes in the base-emitter voltage divided by will give the temperature change with respect to ambient.…”

“…First, RF bipolar transistors operate at very large current densities in order to push the high-frequency performance to the limits [1]. Second, there is a positive feedback between the collector current and temperature of a bipolar transistor that can induce thermal instabilities [2]- [7]. Third, reduction of the parasitic capacitances of the active devices and increase in the level of integration in RF systems is achieved by decreasing the parasitic coupling to the Si substrate.…”

“…It is, therefore, very important to accurately describe electrothermal feedback within a single device, and equally important to understand and describe electrothermal coupling within a circuit composed of such devices. Various dc measurement techniques for extraction of the self-heating thermal resistance are proposed in the literature [7], [16]- [19]. When steady-state thermal models are utilized for characterization of RF devices and circuits, the temperature instantaneously follows the power dissipation signal, and dynamic thermal behavior is disregarded.…”