Johannes Josephus Theodorus Marinus Donkers

A Novel Fully Self-Aligned SiGe:C HBT Architecture Featuring a Single-Step Epitaxial Collector-Base Process

In this paper we describe a novel fully self-aligned HBT architecture, which enables a maximum reduction of device parasitics. TCAD simulations show that this architecture is capable of achieving fT/fmax values of 295/425 GHz for an effective emitter area of 0.13times5 mum2. In this new process approach, which is fully CMOS compatible, the collector and base are grown in a single-step non-selective epitaxial process on top of pre-defined bipolar areas. This provides new opportunities for collector-base profile engineering. The collector drift region and the extrinsic base are made self-aligned to the emitter by means of a dry etch that removes all polycrystalline material. The remaining epitaxial pedestal defines the intrinsic device and makes deep trench isolation redundant. We describe the major features of the integration scheme and show measured fT/fmax values of 300/220 GHz on the first fabricated devices with an effective emitter area of 0.13times5 mum2.

Layout and spacer optimization for high-frequency low-noise performance in HBT's

In this work we study improvements of the high-frequency noise performance of HBT devices by means of layout and spacer optimization. Using an equivalent circuit, we identify the dominant noise sources and demonstrate that the reduction of the base-resistance induced thermal noise by means of dotted emitters in combination with lowering the edge contribution of the base-emitter capacitance (e.g. by emitter-base spacer optimization) translates into better noise performance.

A Novel Isolation Scheme featuring Cavities in the Collector for a High-Speed 0.13μm SiGe:C BiCMOS Technology

A novel isolation scheme is presented in this work, which uses oxide filled cavities in the collector to separate the extrinsic base and collector regions. When incorporated in our 0.13μm SiGe:C BiCMOS technology, a further improvement of the device RF performance is obtained, yielding devices with fT/fmax values of 210/290GHz and 255/210GHz.

Experimental proof of current bifurcation and mutual heating in bipolar transistor arrays

We present experimental proof of the electro-thermal bifurcation and mutual heating in bipolar transistor arrays using photon emission microscopy. With this technique, no electrical probing of each individual transistor in the array is needed but optical measurements allow accurate determination of the electro-thermal effects. For identically processed transistors in an array, we show that current bifurcation and mutual heating can be observed as sequentially optical switching of each transistor. Such optical and electrical switching effect can be explained and described using the individual transistor critical collector current theory after including mutual heating.