Entwicklung einer leistungsfähigen Detektions-Elektronik für die Multispitzen-Rastersondenmikroskopie zur Fehleranalyse an integrierten Schaltungen

摘要

This thesis deals with the development and construction of a detection electronics which is mainly used in atomic force microscopy. The electronics have been realized by using a field-programmable gate array (FPGA). A detection method in atomic force microscopy is the frequency modulation method, which is usually implemented by a phase-locked loop. In this work, the phase detection is implemented using a Hilbert filter. This allows a very high detection bandwidth in excess of tens of kilohertz. The implementation of the phase determination is amplitude-independent, which is not the case with the usually used lock-in method. The electronics is used in the operation with a needle sensor and tested for samples from the semiconductor industry. By realizing a sampling rate of 100 MHz, sensors for the AFM can be operated at a eigenfrequency up to several megahertz. The detection electronics fulfills with its high bandwidth an essential requirement for an application in failure analysis of integrated circuits. There a short time is required for scanning relatively large areas (> 10 μm). Thus, the position of individual SRAM cells or the position of the transistors can be determined so that they can be contacted electrically. For that purpose, multiple tips of a multiprobe scanning force microscope are needed. Therefore, the electronics was constructed modular and is designed for operations of up to ten tips. The detection electronics is also suitable for the imaging of atomic structures with a detection bandwidth of about hundred hertz. In this case, the frequency resolution is 2 mHz. The noise spectral density of the frequency shift signal caused by the electronics is 5 · 10−5 Hz/sqrt(Hz). With regard to the noise, it has been shown, that it is only limited by the thermal noise and the detector noise of the amplifier and not by the developed detection electronics.