Fast Broadband Scanning Microwave Microscopy (FABSMM)

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Scanning Microwave Microscopy (SMM) is a multimodal system that combines Scanning Probe Microscopy (SPM) with microwave measurement technology. Emitting electromagnetic waves from a scanning probe tip makes it possible to measure electromagnetic properties of a nanoscale sample, in addition to its topography. Broadband SMM (BSMM) is a promising solution for the extensive electrical analysis of materials, and is the focus of this work. In one scan, the electromagnetic spectral response of a sample can be captured. The technique also permits non-destructive detection of structures hundreds of nanometers below a specimen’s surface. The doping concentration of semiconductors can also be determined.However, current BSMM technology is faced with to two major challenges:1) Slow scanning speeds can limit spatial resolution at the nanoscale due to the time dependency of thermal drift and vibrations. Accurate analysis of biological or moving specimens is therefore not been achieved. 2) BSMM produces a large amount of measurement data: SPM topography data, as well as two "data cubes" representing the amplitude and phase of the complex scattering parameter, S11. The large amount of correlated data is therefore difficult to process and interpret. The approach proposed in this project will optimize these issues using two different strategies. First, improved scanning methods will be applied in combination with reconstruction algorithms. This will reduce the amount of data to be processed and accelerate the scan process. The best combination of scanning techniques and reconstruction algorithms will be determined by comparing their measurement speed and reconstruction quality. Second, a preliminary investigation is undertaken on the sample in order to identifying which frequencies are most relevant, and which can be neglected. In the end, both strategies will be used simultaneously to increase the speed of sample characterization, along with a reduction in measurement data and simpler data processing.A commercially available electronic memory device from Bruker is used as a test substrate in this project. The electromagnetic spectral response of this substrate showed very strong reactions to the pn-junctions of the measured transistors, in preliminary investigations. This will be further examined during the project runtime. Both proposed strategies will be applied and evaluated during the project on this test substrate. Thus, the implementation of this project will provide new insights into doped semiconductors with the use of BSMM. In addition, the strategies developed in this project will broaden the application area of BSMM technology, as the amount of measured data and the measuring speed, is decreased and increased, respectively.The proposed method is based on previous DFG-ANR project work, where a single-frequency SMM was integrated into the chamber of a scanning electron microscope to investigate Atto-Farad large capacitors and memories.