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Cleanroom of the ZHO
View on the cleanroom building of ZHO

The Solid-State Electronics Department and the Department of Optoelectronics share a cleanroom with an area of more than 470m. Special air conditioners move about 230.000m/h air to keep the extraordinary climatic environment on a constant level inside the laboratory. In this absolute clean surrounding and under controlled climatic condition, the Solid-State-Department does research on semiconducting layers, microwave-circuits and devices down to nanosize structures.

Epitaxial Growth of Semiconductor-Heterostructures
MOVPE Reactor of a MOVPE

For the growth of semiconductor layers on Indium-Phosphide substrates, the Metal Organic Vapor Phase Epitaxy (MOVPE) and the Molecular Beam Epitaxy (MBE) are used in the clean room. Both processes are capable for homogeneous growing of very thin (nano-size) and complex layers on III-V semiconductors. These layers are the basic component for all following processes in the technology. The quality of the layer influences and predefines the electrical capabilities and characteristics of active and passive devices.

Devices and Circuits
Electron Beam Lithography
Electron beam lithography
in cleanroom

Based on the layer system, grown by the epitaxy, the wafer is being processed in the technology. To transfer certain structures to the semiconductor surface, two different lithography procedures are available. With the common optical lithography, photoresist on top of the whole wafer is exposed by using a special light source and special glas masks which contain the structure information. This technique is suitable for structures down to one micrometer. For sub-micron structures and prototypes, a special electron beam lithography is used. A software controlled electron beam writes the structure information directly into the fotoresist. Furthermore, all wafer cycle through different wet chemical etching and metal and dielectric deposition processes until devices and circuits are completed.

Measurement and Characterization
measurement station Student assistant at the measurement station

To investigate and characterize devices and circuits produced in the technology, extensive measurement equipment for large- and small-signal analysis is available. All devices and circuits are being measured and characterized from DC up to high frequencies (50GHz). Additional measurements like noise-figure measurements and transient measurements are also available for characterization. The Department has developed a special temperature measurement setup, that allows DC and RF measurements in very low temperature environment on-wafer.

Device Simulation and Circuit Design
Circuit Layout
Circuit Design
and Layout

Parallel to the technological work, physical device models have been created and are permanently modified and improved. The theoretical results of these models are compared with the measured parameters of real devices to create reliable and scalable tools for the description of new devices. Purpose is the optimization of existing devices for special applications. Furthermore processes have been developed that allow the frequency- dependend modelling of devices with equivalent circuits to achieve information about their intrinsic behaviour. These information allow to draw conclusions from the device about technological processes. The knowledge about these devices allow for the creation of simple models that are used for simulation of complex microwave circuits. Finally these developed and optimized circuits are again realized in the technology and measured in the laboratory.

Nanotechnology

A new and young field of activity of the Solid-State Electronics Department is the Nanotechnology. In this project, the work is focussed on nanoparticles (Nanobricks). These nanoparticles consist only of few atoms and have promising electrical behaviour and characteristics that makes them suitable for the application in active devices.

More...

For more information about research refer to the project presentation page.


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