Modeling of non-linear large-signal dynamic effects in SiGe heterojunction bipolar transistors

超高速硅锗（SiGe）异质结双极晶体管（HBT）工艺技术的可用性已经促使人们对利用毫米波和THz频谱用于电子应用的兴趣迅速增加。集成电路的设计和优化，在这样的高频率需要准确的紧凑型（即集总）模型的HBT与几百GHz的截止频率。遗憾的是，由于缺乏足够的测量设备，现有紧凑型模型的大信号（LS）行为无法在67 GHz以上进行验证。数值器件仿真（所谓的TCAD）已经表明，在高频LS开关操作期间，特别是当进入高电流区域时，在该区域中的峰值的紧凑模型的错误。这些误差主要是由晶体管内垂直和横向维度上的移动的电荷分布的分布特征（即非准静态（NQS）效应）引起的，而在当前的紧凑模型中没有充分考虑到这一点。在第一阶段的研究中，我们从TCAD和晶体管理论出发，对垂直和横向的NQS效应有了一个基于物理的理解。基于一维（1D）输运和连续性方程的封闭形式解，建立了用于评估简化对分析电荷建模的影响的参考。此外，二维（2D）HBT结构的LS操作的调查显示，捕获横向NQS效应与集总模式的有前途的结果。最后，LS测量揭示了迄今无法解释的三次谐波失真行为。拟议的第二个项目阶段解决观察到的问题如下：（i）从1D晶体管理论中推导出垂直NQS效应的基于物理的公式，特别强调对高电流区域进行更准确的建模。(ii)将1D晶体管理论扩展到2D晶体管理论，以实现具有转移电流的紧凑内部基极阻抗的完全一致的定义，并推导出集总晶体管模型中与横向NQS效应相关的电荷分配因子的基于物理的电流相关公式。(iii)模型应用到先进的SiGe HBT结构和LS模型的验证与混合模式器件的模拟和测量，不仅使用负载牵引，但也是一种新的无源输出滤波器为基础的方法，以获得高达325 GHz的谐波幅度。拟议的工作，细分为明确定义的工作包，还包括设计和制造的测试结构和他们的实验晶圆表征高达325 GHz。

The availability of ultra-high-speed silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) process technology has spurred rapidly increasing interest in utilizing the millimeter-wave and THz frequency spectrum for electronic applications. Integrated circuit design and optimization at such high frequencies requires accurate compact (i.e. lumped) models for HBTs with cut-off frequencies of several hundred GHz. Unfortunately, the large-signal (LS) behavior of existing compact models cannot be verified beyond 67 GHz due to the lack of adequate measurement equipment. Numerical device simulation (so-called TCAD) has indicated significant compact model errors during LS switching operation at high frequencies, especially when entering the high-current region where the transconductance peaks. These errors are caused mainly by the distributed character (i.e. non-quasi-static (NQS) effects) of the mobile charge distribution within the transistor in both vertical and lateral dimension, which is not adequately taken into account in present compact models. In the first phase of this project, a physics-based understanding of the NQS effects in vertical and lateral direction has been obtained from TCAD and transistor theory. Based on a closed-form solution of the one-dimensional (1D) transport and continuity equation, a reference for evaluating the impact of simplifications for analytical charge modeling has been established. Furthermore, investigations of the LS operation of two-dimensional (2D) HBT structures show promising results for capturing lateral NQS effects with a lumped mode. Finally, LS measurements revealed so far unexplained third-harmonic distortion behavior. The proposed second project phase addresses the observed problems as follows: (i) Derivation of a physics-based formulation for vertical NQS effects from 1D transistor theory with special emphasis on a more accurate modeling of the high-current region. (ii) Extension of 1D to 2D transistor theory for enabling a fully consistent definition of a compact internal base impedance with the transfer current and the derivation of a physics-based current dependent formulation of the lateral NQS effect related charge partitioning factor in a lumped transistor model. (iii) Model application to advanced SiGe HBT structures and verification of the LS model with both mixed-mode device simulation and measurements using not only load-pull but also a novel passive output filter based approach for obtaining the amplitudes of harmonics up to 325 GHz. The proposed work, subdivided into clearly defined work packages, also includes the design and fabrication of test structures and their experimental on-wafer characterization up to 325 GHz.