Hernan Rueda

Development of a Cost-Effective, Selective-Epi, SiGe:C HBT Module for 77GHz Automotive Radar

The development of a selective-epi, SiGe:C HBT module for 77GHz automotive radar applications is described. A cutoff frequency (fT ) of 185GHz, in conjunction with a maximum oscillation frequency of 260GHz has been achieved through the implementation of a self-aligned selective-epi base structure and a simple, cost-effective collector construction without buried layer or deep trench isolation

A half-kW capable 28-V LDMOS RF power transistor in a small-footprint package

This paper presents a half-kW capable 28-V LDMOS single-ended RF power transistor designed in an air cavity ceramic package for 2.1 GHz applications. Compared to other existing products in the market with similar power levels, this transistor has its package size reduced by ~30% and demonstrates to date the highest power density per unit area in industry. The transistor has been designed using the latest generation of Freescales Airfast™ 28-V LDMOS technology. The novel gate engineering applied in this generation enables 2 dB higher gain than its precedent while retaining excellent efficiency, linearity and power density. A Class-AB power amplifier is designed with the transistor for optimized output power and gain flatness in the 2.11-2.17 GHz band. It delivers 426 watts of P3dB power with 18.3 dB maximum gain.

Fast physical models for Si LDMOS power transistor characterization

A new quasi-two-dimensional (Q2D) model is described for microwave laterally diffused MOS (LDMOS) power transistors. A set of one-dimensional energy transport equations are solved across a two-dimensional cross-section in a “current-driven” form. This process-oriented nonlinear model accounts for thermal effects, avalanche breakdown and gate conduction. It accurately predicts DC and microwave characteristics as demonstrated by comparison with measured DC characteristics, transconductance, forward gain, S21, and large-signal gate and drain charges for a LDMOS transistor. The model is fast, taking less than 30 ms to extract a 50 point DC IDS-VDS characteristic and less than 5 ms to produce S-parameters at a single frequency.

A Quasi-Two-Dimensional Model for High-Power RF LDMOS Transistors

A new quasi-2-D model for laterally diffused metal-oxide-semiconductor radio-frequency power transistors is described in this paper. We model the intrinsic transistor as a series laterally diffused p-channel and n-type drift region network, where the regional boundary is treated as a reverse-biased p+-n diode. A single set of 1-D energy transport equations is solved across a 2-D cross section in a “current-driven” form, and specific device features are modeled without having to solve regional boundary node potentials using numerical iteration procedures within the model itself. This fast process-oriented nonlinear physical model is scalable over a wide range of device widths and accurately models direct-current and microwave characteristics.

Device physics and EM simulation based modeling methodology for LDMOS RF power transistors

In this paper, process, device, and electromagnetic simulations are combined to produce a distributed nonlinear model for an LDMOS RF power transistor. The simulation challenges are handled by using multiple simulators, each with a suitable role in the modeling process. Semiconductor fabrication and device operation are performed through the process and device technology computer aided design (TCAD) tool. The outcome from the TCAD simulations are used to generate a nonlinear compact model for a small section of the device. To form the complete transistor model, many small sections of the compact model are connected by a large-scale interconnect network, which is modeled based on electromagnetic (EM) simulations. For convenient use in circuit simulator, the distributed nonlinear model is implemented by a script-generated comprehensive netlist. It is demonstrated that this purely simulation-based model can accurately predict device behavior under DC, small-signal, and large-signal tests, and is useful for first-pass computer-aided design before wafer fabrication.

Substrate optimization for accurate EM simulation

This paper presents an optimization-based technique to develop silicon substrate for accurate and efficient electromagnetic (EM) simulations. The proposed method simplifies the highly nonlinear substrate doping profile into a few regions with effective conductivities. The accuracy of the optimized substrate is validated against measurement data for two spiral inductors. This simplified substrate enables fast and accurate EM simulations. The optimization procedure can be applied to either measurement-based or process simulation-based substrate development, and has a potential to enable EM model creation even before wafer fabrication.

Process-orientated physics-based modeling of microwave power transistors: Small- and large-signal characterization

The coupling between charge transport, heat and energy flow required to model high frequency power devices is developed in the context of a computationally efficient physics-based model, which has been successfully applied to microwave laterally diffused MOS transistors. The accurate prediction of small- and large-signal microwave characteristics, and the physical insight gained, can be used in the process-orientated optimization and process sensitivity analysis of LDMOS power FETs. The charge-based model is well-suited to non-linear CAD implementation for applications such as power amplifier design.