Julia Krause

Physical and Electrical Performance Limits of High-Speed Si GeC HBTs—Part II: Lateral Scaling

The overall purpose of this paper is the prediction of the ultimate electrical high-frequency performance potential for SiGeC HBTs under the constraints of practical applications. This goal is achieved by utilizing advanced device simulation tools with parameters calibrated to experimental results of most advanced existing technologies. In addition, detailed electrostatic and electrothermal simulations are performed for determining the parasitic capacitances, temperature increase, and safe operating area of aggressively scaled devices. The important figures of merit are then determined from circuit simulation employing an accurate compact model incorporating all relevant physical effects. Based on the vertical profile found in Part I, this paper focuses on achieving a balanced device design by lateral scaling. It is shown that the peak values of (fT, fmax) around (1, 1.5) THz may be achievable. Such a performance limit provides still significant headroom for further developing existing processes and makes SiGeC HBTs well-suitable for highly integrated millimeter-wave applications operating within the low-end of the terahertz gap.

HICUM/2 v2.3 parameter extraction for advanced SiGe-heterojunction bipolar transistors

This paper presents extraction methodologies for advanced SiGe heterojunction bipolar transistors (HBTs). Demonstrated methods focus on extracting the transfer current related parameters over a large temperature range for the new version 2.3 of the compact HBT model HICUM Level 2. Also shown are the limitations of existing extraction methods. Results for DC and AC characteristics are shown for different temperatures.

Compact Layout and Bias-Dependent Base-Resistance Modeling for Advanced SiGe HBTs

In this paper, an improved and extended set of physics-based analytical equations for describing the external and internal base resistance of silicon-germanium HBTs as a function of geometry (layout) is presented. The investigated layouts include single- and double-base contacts not only in parallel but also perpendicular to the emitter finger. In addition, via and slot base contacts, a large range of link to internal-base-sheet-resistance ratio, and changes in external base layout dimensions are covered. The new equations are verified using quasi-3-D device simulation and are demonstrated to be applicable to all practically useful emitter aspect ratios.

SiGe HBT modeling for mm-wave circuit design

An overview on the compact modeling activities within the DOTSEVEN project is given. Issues such as geometry scaling, substrate coupling and thermal effects as well as HICUM Level 2 features enabling the accurate modeling of the linear and non-linear characteristics of the latest generation of SiGe HBTs are discussed. Furthermore, experimental results for the most important DC and small-signal characteristics as well as selected examples for non-linear modeling of the most advanced SiGe HBTs from two different technologies are presented. Model verification issues related to limited on-wafer high-frequency measurement capability and the accurate calibration at multi-hundred GHz are briefly touched.

On the Feasibility of 500 GHz Silicon-Germanium HBTs

A procedure for rapid TCAD based evaluation of device design alternatives is presented. It employs 1D device simulation in combination with a physics-based compact model and a corre- sponding model generator. This enables to provide libraries with geometry scalable models for mm-wave circuit optimization. Based on an experimentally calibrated baseline the procedure is applied to demonstrate the feasibility of SiGe HBTs with (f T ,f max ) = (420, 520) GHz at realistic vertical and lateral dimen- sions. The proposed method is suitable for improving the existing ITRS 2007 SiGe HBT roadmap towards emerging mm-wave applications. Keywords-Device simulation, SiGe heterojunction bipolar tran- sistors, HICUM, Device scaling

Methods for Determining the Emitter Resistance in SiGe HBTs: A Review and an Evaluation Across Technology Generations

For the experimental determination of the emitter resistance of bipolar junction transistors and HBTs, many methods exist in the literature, which yield quite different results though. In this paper, the most widely used methods are reviewed and applied to SiGe HBTs of different technologies and generations, including different device types (i.e., high-speed and high-voltage transistors). First, the accuracy of the methods is evaluated based on simulated data using a compact model. Explanations for causes of observed inaccuracy or failure are given and discussed. Second, suitable methods are applied to experimental data. In both cases, the results are compared for a large variety of device sizes. This paper and its results provide insight into each methods accuracy; its application limits with respect to a technology, device size, and operating range; as well as its requirements in terms of equipment and extraction effort. A guideline for extracting the emitter resistance is also given.

An evaluation of extraction methods for the emitter resistance for InP DHBTs

The emitter series resistance is a very important parameter for bipolar transistors since it can have a significant impact on both the DC and high-frequency characteristics of transistors. Its accurate determination is quite difficult due to the complicated emitter material stack and the lack of suitable test structures. Thus, extraction methods that rely on transistor terminal characteristics must be used instead. In this paper, the accuracy of several widely used extraction methods for the emitter resistance has been investigated for three different type I InP DHBT technologies by applying the methods to both measured and simulated data. Since for the latter the emitter resistance is exactly known, it allows a reliable evaluation of the accuracy and the applicability of a method.

SiGeC and InP HBT Compact Modeling for mm-Wave and THz Applications

An overview on compact transistor modeling for mm-wave HBT technologies is provided. Using HICUM as a vehicle, a comparison to experimental DC, AC and large-signal data is performed. Selected examples are shown for advanced SiGeC and InP HBTs with operating frequencies (fT, fmax) of (300, 500) GHz and (350, 450) GHz, respectively. Good agreement between model and measurements is obtained for all characteristics

Generating Image Descriptions for SmartArts

Visual information such as SmartArts are often used in presentations and lectures. SmartArts are visual information containing some text and graphical elements. They have to be described verbally to become accessible for visually impaired and blind people. But a manual image description is often not provided or misses information about the pictorial part of SmartArt diagrams. We present a PowerPoint Add-In to create image descriptions semiautomatically. Both a short description and a long description containing details are generated. The author can adjust the generation by modifying a template. In a user evaluation the quality of manually and semi-automatic transcribed images were tested.