Abstract-Three-Dimensional Terahertz Tomography With Transistor-Based Signal Source and Detector Circuits Operating Near 300 GHz

Jungsoo Kim,  Daekeun Yoon,   Jongwon Yun,  Kiryong Song,   Mehmet Kaynak, Bernd Tillack,   Jae-Sung Rieh

https://ieeexplore.ieee.org/document/8399538/

In this paper, three-dimensional (3-D) terahertz (THz) tomography was demonstrated with a signal source and imagers based on transistor circuits fabricated with standard semiconductor technologies. For the signal source, a 300-GHz oscillator based on InP HBT technology was employed. For detection, two types of imagers operating near 300 GHz were employed, one direct and the other heterodyne, both realized with SiGe HBT technology. With a set of 2-D images taken from different angles, sinograms and tomograms were obtained, which led to a successful reconstruction of 3-D images of the target object based on the filtered back-projection algorithm. A systematic comparison was made for the direct imager and the heterodyne imager, for which the signal input power and the video bandwidth were varied for both imagers. The results revealed that the heterodyne imager shows a better sensitivity than the direct imager. However, a similar dynamic range of around 30 dB was achieved for both imagers because of a saturation observed for the heterodyne imager when the input power exceeds the threshold. The video bandwidth did not affect the image quality significantly for the bandwidth variation over four orders of magnitude for both imagers.

Abstract-300-GHz Direct and Heterodyne Active Imagers Based on 0.13-μm SiGe HBT Technology

Daekeun Yoon, Jungsoo Kim,   Jongwon Yun, Mehmet Kaynak,  Bernd Tillack, Jae-Sung Rieh,

http://ieeexplore.ieee.org/document/7962297/

300-GHz direct and heterodyne imagers based on a 0.13-μm SiGe HBT technology were developed for active imaging applications in this work. The direct imager, which is based on the square-law principle, shows a maximum responsivity of 6121 V/W and a minimum noise equivalent power (NEP) of 21.2 pW/Hz1/2 at 315 GHz. The heterodyne imager, which consists of a mixer, a local oscillator, an IF amplifier, and an IF detector, exhibits a maximum responsivity of 322 kV/W and a minimum NEP of 3.9 pW/Hz1/2 at 300 GHz. Total dc power consumption of the direct imager is 0.6 mW, while the heterodyne imager consumes 21 mW. The chip areas of the direct and heterodyne imagers including the on-chip antenna are 460 × 410 and 610 × 610 μm2, respectively. To compare the performance of the two types of imagers for imaging applications, images from both imagers were acquired and compared with various output power levels of the signal source. It was demonstrated that the heterodyne imager shows much better image quality, especially when the signal source power is not sufficiently high.

Cream of the Crop: Sandwich Chips Combining the Best of Two Technologies

                          Wafer with "sandwich chips". (Credit: FBH/Immerz)
http://www.sciencedaily.com/releases/2012/12/121218081744.htm
Dec. 18, 2012 — Two Leibniz institutes broke new technological ground and successfully combined their -- up to now separate -- technology worlds. Due to their high performance the novel chips developed within the HiTeK project promises to open up new applications


Wolfgang Heinrich and Bernd Tillack are convinced of holding the key to faster and more powerful terahertz chips. The two scientists and their teams come from the Berlin-based Ferdinand-Braun-Institut (FBH) and from the IHP-Leibniz-Institut für innovative Mikroelektronik in Frankfurt/Oder -- and thus from two different technology worlds. FBH is one of the leading institutes in developing III-V semiconductors, while IHP is specialized in silicon-based systems and circuits. Both Leibniz institutes joined forces within the HiTeK project to combine the advantages of silicon-based CMOS (Complementary Metal Oxide Semiconductor) circuits from the IHP with those of indium-phosphide circuits from the FBH. The partners now accomplished an important step within the project by successfully integrating both circuits on a semiconductor wafer, with measurement results demonstrating their high performance. With the integration on one chip, new ambitious applications in the THz range are within reach such as high-resolution imaging systems for medical and security technology as well as ultra-broadband mobile communication applications.
For such applications high output powers along with faster computer processors are needed offering enhanced computer operation per second. In order to achieve this, circuits on the chips have to become smaller -- the key reason which boosts miniaturization in semiconductor industry. If the frequency range around 100 gigahertz and beyond is to be covered, however, the breakdown voltage in the CMOS switching circuits decreases significantly. Accordingly, the available output power of the chips declines, which implies that the capability to generate sufficiently strong signals to establish a radio link and to detect material defects becomes insufficient. To find a solution for this problem, IHP conducts research on bipolar CMOS based on silicon-germanium enhancing the breakdown voltages at high speed compared to pure CMOS. By combining a standard CMOS circuit with a second indium-phosphide circuit promises further improvement. Both circuits are realized "sandwich-like" on top of each other. Where the traditional silicon-based CMOS technology reaches its limits, this novel material combination delivers the desired properties: high output powers at high frequencies. The sandwich chips allow to keep benefiting from the high level of production routine and integration of CMOS circuits -- particularly regarding the fact that 95 % of all digital and analogue-digital circuits base on this technology.
"It was particularly challenging to make both technologies compatible at the interfaces," underlines Wolfgang Heinrich from the FBH. To achieve this, the whole development environment of both processes as, for example, the software for the circuit layout had to be merged in a first step. Subsequently, both layers had to be dimensioned so that they reach the essential good transmission properties for frequencies around 200 gigahertz. Precision work was also highly demanded to adjust the circuits precisely to each other with an accuracy of less than 10 micrometers. Heinrich is especially proud of the friction-less cooperation: "We managed to align both technology worlds so smoothly that the circuits deliver fully the specified high-frequency performance. This also demonstrates what added value can be created by bundling the competencies of two institutes like IHP and FBH."
The next steps are now to further stabilize the process and to optimize the circuits. A follow-up project has already been granted. This way, the potential of the hybrid chips shall be exploited fully to reach the borders of what is feasible -- thus setting the stage for the novel sandwich circuits to be integrated in sophisticated applications soon