US20100170016A1

US20100170016A1 - Raster near field microscopy in the microwave and terahertz ranges with a signal processing device intergrated in the measuring tip

Info

Publication number: US20100170016A1
Application number: US11/817,360
Authority: US
Inventors: Meinhard Schilling; Andre Kaestner; Felix Stewing
Original assignee: KUKA Schweissanlagen GmbH
Current assignee: Technische Universitaet Braunschweig; KUKA Systems GmbH
Priority date: 2005-03-09
Filing date: 2005-03-16
Publication date: 2010-07-01
Also published as: RU2007135813A; US8365396B2; EP1858750B1; KR20070114206A; DE502006003448D1; DE202005003913U1; EP1858750A1; WO2006094631A1; ATE428622T1; PL1858750T3; ES2324681T3; US20080189939A1

Abstract

An imaging microwave probe (1) with at least one measuring tip (5) on a measuring arm (2), whereby at least one of the measuring lips (5) has an antenna (6) for the detection or emission of electromagnetic signals and the measuring tip is significantly smaller in the near field than the wavelength of the electromagnetic signals, a positioning device for positioning of an object (3) for measuring relative to the measuring tip (5) in at least one spatial dimension (X, Y, Z), with a signal processing device (7) in electrical connection to the antenna (6) for conversion of the sensor signal from the antenna to a measured signal with a reduced frequency suitable for analysis or for conversion of a coupling signal with reduced frequency into a signal for transmission from the antenna (6) are described. The signal processing device (7) is integrated on the measuring tip (5) adjacent to the antenna (6) and a measured/coupling signal path (8) for the measured and/or coupling signal running from the signal processing device (7) to a measuring unit (9) arranged at a separation from the measuring tip at a frequency selected such that the measured and/or coupling signal is provided in the measuring region without significant distortion.

Description

The invention relates to an imaging microwave probe with at least one measuring tip on a measuring arm, wherein at least one of the measuring tips carries an antenna for detecting or emitting electromagnetic signals and the measuring tip is much smaller in the near field than the wavelength of the electromagnetic signals, with a positioning device for positioning an object to be measured relative to the measuring tip in at least one measuring plane, with a signal-processing device connected electrically to the antenna, for converting the sensor signal of the antenna into a measuring signal with a reduced frequency suitable for evaluation or for converting a coupling signal with reduced frequency into a signal to be emitted by the antenna.
From DE 101 85 096 A1, a SQUID microscope for room-temperature probes is described in which a closed conductor track with a Josephson junction is guided over an edge of a substrate. This makes it possible to reduce the distance between the probe and the microscope tip by means of the SQUID.
Furthermore, from DE 195 20 457 C2, a scanning force microscope with a measuring sensor is known which has a tunnel contact at the end of a lever arm. The tunnel contact can be constructed, for example, as Josephson tunnel contact.
Furthermore, optical near field microscopes, also called SNOM, are known, for example from U.S. Pat. No. 6,545,276 B1 and JP 2004 132711, in which a sample is illuminated with a measuring tip which is narrower than the wavelength of the emitted light. Analysis is carried out by means of an optical verification system.
From U.S. Pat. No. 5,821,410 and U.S. Pat. No. 5,900,618, microwave near field microscopes are known in which microwave power transmitted from a microwave generator to a measuring tip, arranged remotely from it, via a line and the reflected wave is evaluated.
In JP 4264745, a non-imaging microwave probe is described in which microwave power is coupled out via an antenna to a circuit to be examined and microwave power reflected from the circuit is picked up by the antenna.
The problem of the conventional probes consists in that, due to the line-connected transportation of the maximum-frequency measuring signal from the measuring tip to an evaluating unit arranged remotely therefrom, or of a maximum-frequency transmitting signal from a transmitter arranged remotely from the measuring tip to the measuring tip, the signals are greatly influenced by the lines and the measuring environment. The problem occurs, for example, in the examination of electromagnetic signals up into the terahertz range in circuits, microchips and other samples.
It is, therefore, the object of the invention to create an improved imaging microwave probe which can also be used for analyzing electromagnetic signals with extremely high frequency up into the terahertz range.
According to the invention, the object is achieved by means of the generic imaging microwave probe in that the signal processing device is integrated adjoining the antenna on the measuring tip and a measuring/coupling signal transmission link for the measuring and/or coupling signal extends from the signal processing device to a measuring unit arranged remotely from the measuring tip, with a frequency which is selected in such a manner that the measuring and/or coupling signal can be transported through the measuring environment without significant disturbance.
Due to the fact that the signal processing device is integrated on the measuring tip and during the detection, the conversion of the detected electromagnetic signal into a measuring signal by the signal processing device is carried out directly on the measuring tip adjoining the antenna, electromagnetic signals of extremely high frequency can also be detected with a spatial resolution into the nanometer range in the near field, since the signal coupled out is transmitted with reduced frequency to an external measuring unit. Correspondingly, the electromagnetic signal with high to extremely high frequency is generated during the emission directly in the measuring tip by the signal processing device which is only driven by a coupling signal with reduced frequency. This avoids negative influences of the measuring environment by attenuation and crosstalk.
Due to the imaging characteristic of the probe, it is now possible to determine equivalent circuits of complex integrated circuits, to find defects in implemented circuits and also check model calculations for the three-dimensional radiation of signals.
The electromagnetic signals are preferably in the frequency range from 3 GHz to 300 THz. It is particularly preferred if the frequency range begins at at least 110 GHz. The upper limit of the frequency range is preferably 30 THz at a maximum and particularly preferably 3 THz at a maximum.
The signal processing device and the associated at least one antenna are preferably integrated on an area of 1 mm²at a maximum. Due to these small patterns, the object can be examined in dependence on the frequency of the electromagnetic signals used, with a high resolution, for example of less than 10 μm at frequencies in the THz range from 110 GHz to 30 THz.
At least one of the antennas is preferably provided as measurement pick-up tip for extracting electromagnetic signals from the object to be examined. In this arrangement, the at least one associated signal processing device should be constructed as receiver for receiving electromagnetic signals and connected electrically to the at least one antenna for extracting electromagnetic signals from the object to be examined.
Optionally or additionally, at least one of the antennas can be provided for coupling electromagnetic signals into the object to be examined. The measurement is then carried out in the object to be measured itself. In this arrangement, the associated signal processing devices should be constructed as transmitters for generating electromagnetic signals and connected electrically to this at least one antenna for coupling the electromagnetic signals generated into the object to be examined.
For constructing a transmitter or receiver, the signal processing devices preferably have signal amplifiers and/or an oscillator and/or a modulation device and/or a matching circuit.
It is particularly advantageous if the measurement pick-up tips are constructed to be directionally sensitive for detecting in each case one field component of the electrical or magnetic field in the near field of the object so that a vector sensor can be implemented by means of at least two and preferably three directionally sensitive measurement pick-up tips.
It is advantageous if the signal processing devices have means for influencing and/or detecting the phase of the signal emitted or detected. This can be done, for example, by means of a detunable inductance or capacitance. This makes it possible, for example, to carry out a vectorial network analysis.
The signal processing device can have a selectable reference oscillator and a mixer electrically connected to the reference oscillator, in order to place the signal to be emitted or to be detected into reference with respect to a temporal reference signal of the reference oscillator with regard to the amplitude and/or phase of the signal. The mixer is used for down-converting the electromagnetic signal into the measuring signal with reduced frequency or for up-converting the coupling signal with reduced frequency into the electromagnetic signal.
The microwave probe described above can be used, for example, for reflection measurement, emission measurement, absorption measurement or transmission measurement. In the reflection measurement, for example, the signal detected by the antenna can thus be measured with regard to amplitude, phase and frequency spectrum after microwave power has been coupled into the object to be measured.
The signal processing device is preferably constructed for the frequency-selective coupling-in and/or -out of the electromagnetic signals. The object to be measured can thus be scanned with spatial and frequency resolution in a defined frequency spectrum with specified frequency intervals. However, it is particularly advantageous if the signal processing device is constructed for the time-dependent extraction of electromagnetic signals from the object and a transformation of the extracted signals into the frequency domain for detecting the frequency dependence of the signals is provided. Thus, an entire frequency band can be scanned in one step without losing the frequency information.
The electromagnetic signals can be coupled-in and/or -out with the antenna essentially capacitively, inductively or resistively. Since the other components are always also contained in the coupling-out, i.e. inductive and resistive components are also present in the capacitive coupling-out, the term “essentially” is intended to clarify that the major component is intended to have the main importance.
It is particularly advantageous if the antenna has at least one Josephson junction. The Josephson junction can be used at the same time for the signal processing device. This provides for particularly small integration with high resolution and measuring accuracy. The measurement pick-up tip has preferably a Josephson junction in a control circuit in compensation mode, the microwave probe being constructed for determining other measuring quantities, for example temperature, magnetic field, topography of the object, distance between object and measuring tip, from the control signals of the signal processing device. This makes use of the fact that the behavior of the control loop for the Josephson junction contains, for example, temperature information which can be extracted by the signal processing device and/or measurement evaluation circuit by evaluating the electrical behavior of the control loop.
However, at least one measurement pick-up for detecting other measuring quantities, for example temperature, magnetic field, topography of the object, distance between object and measuring tip, can also be integrated in the measuring tip. The measuring quantities picked up by the measuring pick up can then be utilized for controlling the microwave probe and for measurement data analysis.
Disturbances of the measuring environment and possibly of the measuring signal can be reduced if the measuring tip and possibly the measuring arm has/have shielding for interfering electrical and magnetic fields.
It is advantageous if the measuring tip has a cooler for cooling the antenna. Optionally or additionally, a cooler can also be provided for cooling the object. An electrical microcooler or a cooler with liquid coolant can be used as cooler. Furthermore, a heating element can be provided optionally or preferably in addition to the cooler in the measuring tip, for heating the antenna and/or a heating element can be provided for heating the object. The electrical microcooler or the heating element can have, for example, a Peltier element. This makes it possible to enforce directional heat flows.
The measuring/coupling signal transmission link can be constructed to be line-connected, for example as electrical line or optical waveguide, or non-line-connected, for example as radio transmission link, for transmitting the measuring and/or coupling signal and/or the reference signal of the reference oscillator.
To control the microwave probe, it is advantageous if it is constructed for generating a relative mechanical vibration between the object to be measured and the measuring tip for the approach of object and measuring tip and detection of the distance between object and measuring tip in dependence on the damping of the vibration.
However, the measuring tip can also approach the object by determining the distance between object and measuring tip from the detected or emitted electromagnetic signals of the associated signal processing device from which control signals are generated for moving the measuring tip towards the object.

In the text which follows, the invention will be explained in greater detail by way of example with reference to the attached drawings, in which:

FIG. 1 shows a diagrammatic cross-sectional view of the imaging microwave scanning microscope with sensor and detector circuit integrated into the measuring tip;

FIG. 2 shows a diagrammatic sectional view of the measuring tip of the microwave scanning microscope from FIG. 1;

FIG. 3 shows a diagram of a signal processing device operating as transmitter;

FIG. 4 shows a block diagram of a signal processing device operating as receiver.

FIG. 1 shows a sketch of an imaging microwave probe 1 with a measuring arm 2. The measuring arm 2 extends in the direction of an object 3 to be measured which is carried by a displaceably supported holder 4 with positioning device for displacing the object 3 in the three cartesian spatial dimensions, that is to say the X, Y and Z direction. At the end of the measuring arm 2 directed towards the object 3, a measuring tip 5 is provided which has an antenna 6 for the essentially capacitive, inductive or resistive coupling-in or -out of electromagnetic signals with a frequency up into the terahertz range, i.e. a frequency range from 3 GHz to 300 THz and preferably 110 GHz to 30 THz.
Immediately adjoining the antenna 6, a signal processing device 7 is integrated in the measuring tip and electrically connected to an associated antenna 6. For the case of the antenna 6 being provided as measurement pick-up tip for extracting electromagnetic signals from the object 3, the signal processing device 7 is constructed as receiver for down-converting the extracted signal with high or extremely high frequency to a measuring signal with reduced frequency. In the case where the measuring tip 5 is provided for the emission of electromagnetic signals into the object 3, the signal processing device 7 is constructed as transmitter in order to convert a coupling signal up to a higher frequency of the electromagnetic signal. The measuring and/or coupling signal is transmitted between the measuring device 9 and the signal processing device 7 via a line-connected or non-line-connected measuring/coupling signal transmission link 8. The transmission can take place, for example, by means of an electrical or optical measuring line which is conducted on the measuring arm 2 along to a measuring unit 9. Optionally, radio transmission of the measuring/coupling signal is also possible, wherein an additional radio transmitter/receiver is integrated onto the measuring tip 5 for radio data communication, for example in accordance with the Bluetooth standard, with the signal processing device 7.
Reducing the frequency of the measuring and coupling signal and integrating the transmitter/receiver directly on the measuring tip 5 prevents crosstalk of the measuring or coupling signal into the measuring environment and ensures a largely interference-free forwarding of the measuring and coupling signal between the measuring tip 5 and the measuring unit 9, arranged remotely therefrom.
The measuring or coupling signal can be oscillation, e.g. a sinusoidal or rectangular oscillation with defined frequency, a pulse signal with specified pulse width and pulse frequency, a CW (continuous wave) signal or the like. Mixed operation with a change in frequency, e.g. during the pulses, is also possible.
For a first measuring method (1), extremely-high frequency microwave power can be extracted with the imaging microwave probe 1 from the object 3 with a spatial resolution into the nanometer range in the near field and, due to the conversion of the extracted electromagnetic signal with a frequency in the THz range into a measuring signal with reduced frequency by the signal processing device 7 arranged immediately adjoining the antenna 6 in the measuring tip 5, can be transmitted to the measuring unit 9 without the conventional problems of attenuation and crosstalk at the relatively long measuring/coupling signal transmission link 8.
In a second measuring method (2), microwave power is first coupled into the object 3 from the antenna 6 and the resultant signal is measured with the aid of this or another antenna 6, the associated signal processing device 7 and the measuring unit 9. For this purpose, a coupling signal is conducted from the measuring unit 9 to the signal processing device 7 and is converted there into the electromagnetic signal to be emitted with high or extremely high frequency. The resultant signal is then detected by this or another antenna 6 of the microwave probe 1 as in method (1). Due to the attenuation and phase determined, it is then possible, for example, to determine the impedance.
In a third method (3), microwave power is coupled into the object 3 from the antenna 6. The microwave power is then measured in the object 3 itself, for example by measuring the electrical behavior at the connections of an integrated circuit. For coupling-in the microwave power, an electromagnetic signal, the frequency, amplitude and phase of which is determined by a coupling signal input by the measuring unit 9, is emitted from the antenna 6 as in method (2). The coupling signal is again converted into the electromagnetic signal with high or extremely high frequency with the aid of the signal processing device 7.
As an alternative or additionally to the displaceable holder 4, the positioning device can also be coupled to the measuring arm 2 in order to displace the latter in at least one measuring plane. The positionability of the object 3, to be measured, relative to the measuring tip in all three spatial dimensions X, Y, Z, makes it possible to pick up three-dimensional radiation distributions in the space around and above the object 3.
The detection of the electromagnetic signals by means of the antenna 5 preferably takes place with spectral resolution, that is to say frequency-selectively. For this purpose, a mixer of the signal processing device 7 is driven with respect to a reference signal input from a reference oscillator. The signal to be detected or to be emitted is then in reference to the temporal reference signal with regard to the amplitude and/or phase of the high-frequency signal.
FIG. 2 shows a section of a measuring tip 5 with at least one Josephson junction 10 which forms the antenna 6 and possibly a part of the signal processing device 7. The Josephson junction 10 is located on an interface between two crystal halves of the measuring tip 5. The size of the antenna 6 is about 1 μm×1 μm. The signal processing device 7 is then integrated immediately adjoining thereto at a distance in the μm range preferably 1 to 100 μm from the antenna 6 on the measuring tip 5.
FIG. 3 shows a block diagram of a signal processing device 7 constructed as transmitter. At the input of the signal processing device 7, a matching circuit 11 is provided for matching the signal level of the coupling signal and/or the impedance of the measuring/coupling signal transmission link 8 to the signal processing device 7. The matching circuit 11 is connected to a mixer 12 in order to convert the coupling signal up to a higher frequency, preferably in the abovementioned Terahertz frequency range. For this purpose, the mixer is driven by an oscillator 13 which can be integrated on the measuring tip 5 as part of the signal processing device 7. However, it is also conceivable to supply the oscillator signal to the measuring tip from the outside as reference signal, for example by means of a modulated laser beam. The up converted electromagnetic signal is supplied to the antenna 6 amplified via an amplifier 14 and a matching circuit 15.
FIG. 4 shows a block diagram of a signal processing device 7 constructed as receiver. An amplifier 16 for amplifying the detected electromagnetic signal is provided at the input of the signal processing device 7, which is electrically connected to the antenna 6. The amplifier 16 is connected to a mixer 17 in order to down convert the amplified detected signal, preferably in the abovementioned Terahertz frequency range, to a reduced frequency to such an extent that crosstalk in the measuring environment due to the down converted measuring signal is prevented and the measuring signal can be forwarded to an external measuring unit 9 for further signal evaluation. For this purpose, the mixer 17 is driven by an oscillator 18 which can be integrated on the measuring tip 5 as part of the signal processing device 7. However, it is also conceivable to supply the oscillator signal to the measuring tip from the outside as reference signal, for example by means of a modulated laser beam. The down converted electromagnetic signal is conducted as measuring signal via a filter 19 to the external measuring unit 9.
However, the signal processing device 7 can also optionally or additionally have an analog/digital converter in order to convert the detected or emitted electromagnetic signal into a digital measuring signal.
In this manner, the imaging microwave probe 1 can be used, for example, for 3-D microwave spectroscopy. It is also possible to use a Hilbert transformation for spectroscopy in a familiar manner.
In particular, knowledge of the chip structure (topography) provides for spatially resolved verification of highly integrated circuits which are operated with high and extremely high frequencies.
The approach of the measuring tip 5 to the object can be controlled with the aid of the detected measuring signals, particularly by evaluation of the attenuation as distance signal. In a manner known per se, a vibration can be imparted to the object 3 and/or the measuring tip 5, the approach of object 3 and measuring tip 5 being controlled in dependence on the observed damping of the vibration. However, an optical measurement of the distance during the approach of object 3 and measuring tip 5 by interference measurement is also conceivable.
In the examination of the object 3, other measuring quantities apart from the electromagnetic signals can also be coupled into the object 3 and/or extracted, such as, e.g. magnetic fields, heat radiation etc. During this process, the reaction of the object 3 to the measuring quantities coupled in is measured and evaluated.

Claims

1. An imaging microwave probe (1) with at least one measuring tip (5) on a measuring arm (2), wherein at least one of the measuring tips (5) carries an antenna (6) for detecting or emitting electromagnetic signals and the measuring tip is much smaller in the near field than the wavelength of the electromagnetic signals, with a positioning device for positioning an object (3) to be measured relative to the measuring tip (5) in at least one spatial dimension (X, Y, Z), with a signal processing device (7), electrically connected to the antenna (6), for converting the sensor signal of the antenna (6) into a measuring signal with a reduced frequency suitable for evaluation or for converting a coupling signal with reduced frequency into a signal to be emitted by the antenna (6), characterized in that the signal processing device (7) is integrated adjoining the antenna (6) on the measuring tip (5) and a measuring/coupling signal-transmission link (8) for the measuring and/or coupling signal extends from the signal processing device (7) to a measuring unit (9), arranged remotely from the measuring tip (5), with a frequency which is selected in such a manner that the measuring and/or coupling signal can be transported through the measuring environment without significant disturbance.

2. The imaging microwave probe (1) as claimed in claim 1, characterized in that the electromagnetic signals are in the frequency range from 3 GHz to 300 THz.

3. The imaging microwave probe (1) as claimed in claim 2, characterized in that the electromagnetic signals have a frequency of at least 110 GHz.

4. The imaging microwave probe (1) as claimed in claim 2, characterized in that the electromagnetic signals have a frequency of 30 THz at a maximum or 3 THz at a maximum.

5. The imaging microwave probe (1) as claimed in claim 1, characterized in that the signal processing device (7) and the at least one associated antenna (6) are integrated on an area of 1 mm²at a maximum.

6. The imaging microwave probe (1) as claimed in claim 1, characterized in that at least one antenna (6) is constructed as measurement pick-up tip for extracting electromagnetic signals from the object (3) to be examined.

7. The imaging microwave probe (1) as claimed in claim 6, characterized in that measurement pick-up tips are constructed to be directionally sensitive for detecting in each case one field component of the electrical or magnetic field in the near field of the object (3).

8. The imaging microwave probe (1) as claimed in claim 1, characterized in that at least one antenna (6) is constructed for coupling electromagnetic signals into the object (3) to be examined.

9. The imaging microwave probe (1) as claimed in claim 1, characterized in that at least one of the signal processing devices (7) is constructed as transmitter for generating electromagnetic signals and is electrically connected to at least one antenna (6) for coupling the electromagnetic signals generated into the object (3) to be examined.

10. The imaging microwave probe (1) as claimed in claim 1, characterized in that at least one of the signal processing devices (7) is constructed as receiver for receiving electromagnetic signals and is electrically connected to at least one antenna (6) for extracting electromagnetic signals from the object (3) to be examined.

11. The imaging microwave probe (1) as claimed in claim 1, characterized in that the signal processing devices (7) have signal amplifiers (16) and/or an oscillator (13, 18) and/or a modulation device (12, 17) and/or a matching circuit (11, 15, 19).

12. The imaging microwave probe (1) as claimed in claim 1, characterized in that the signal processing devices (7) have means for influencing and/or detecting the phase of the emitted or detected signal.

13. The imaging microwave probe (1) as claimed in claim 1, characterized in that the signal processing device (7) has a selectable reference oscillator and a mixer electrically connected to the reference oscillator, in order to place the signal to be emitted or to be detected in reference with respect to a temporal reference signal of the reference oscillator with regard to the amplitude and/or phase of the signal.

14. The imaging microwave probe (1) as claimed in claim 1, characterized in that the microwave probe (1) is constructed for reflection measurement, emission measurement, absorption measurement or transmission measurement.

15. The imaging microwave probe (1) as claimed in claim 1, characterized in that the signal processing device (7) is constructed for frequency-selective coupling-in and/or -out of the electromagnetic signals.

16. The imaging microwave probe (1) as claimed in claim 1, characterized in that the signal processing device (7) is constructed for the time-dependent extraction of electromagnetic signals from the object (3) and a transformation of the extracted signals into the frequency domain for detecting the frequency dependence of the signals is provided.

17. The imaging microwave probe (1) as claimed in claim 1, characterized in that the antenna (6) is constructed for the essentially capacitive, inductive or resistive coupling-in and/or -out of the electromagnetic signals.

18. The imaging microwave probe (1) as claimed in claim 1, characterized in that the antenna (6) has at least one Josephson junction (10).

19. The imaging microwave probe (1) as claimed in claim 18, characterized in that the antenna (6) has a Josephson junction (10) in a control circuit in compensation mode, and the microwave probe (1) is constructed for determining other measuring quantities, for example temperature, magnetic field, topography of the object (3), distance between object (3) and measuring tip (5), from the control signals of the signal processing device (7).

20. The imaging microwave probe (1) as claimed in claim 1, characterized in that at least one measurement pick-up for detecting other measuring quantities, for example temperature, magnetic field, topography of the object (3), distance between object (3) and measuring tip (5), is integrated in the measuring tip (5).

21. The imaging microwave probe (1) as claimed in claim 1, characterized in that the measuring tip (5) and the measuring arm (2) have shielding for interfering electrical and magnetic fields.

22. The imaging microwave probe (1) as claimed in claim 1, characterized in that a cooler is provided for cooling the antenna (6) in the measuring tip (5) and/or a cooler is provided for cooling the object (3).

23. The imaging microwave probe (1) as claimed in claim 1, characterized in that a heating element for heating the antenna (6) in the measuring tip (5) and/or a heating element for heating the object (3) is provided.

24. The imaging microwave probe (1) as claimed in claim 1, characterized in that the measuring-signal transmission link (8) is constructed to be line-connected or non-line-connected for transmitting the measuring and/or coupling signal and/or the reference signal of the reference oscillator.

25. The imaging microwave probe (1) as claimed in claim 1, characterized in that the microwave probe (1) is constructed for generating a relative mechanical vibration between the object (3) to be measured and the measuring tip (5), for the approach of object (3) and measuring tip (5) and for the detection of the distance between object (3) and measuring tip (5) in dependence on the damping of the vibration.

26. The imaging microwave probe (1) as claimed in claim 1, characterized in that the microwave probe (1) is constructed from the detected or emitted electromagnetic signals of the associated signal processing device (7) for determining the distance between object (3) and measuring tip (5) and control signals for the approach of the measuring tip (5) to the object (3).

27. A method for examining objects (3) by means of an imaging microwave probe (1) as claimed in claim 1, characterized by evaluation of the detected actual signals in conjunction with predetermined nominal signals and representation of the deviations between the detected actual signals and the predetermined nominal signals.

28. The method as claimed in claim 27, characterized by determination of the nominal signals by means of simulation calculations on the basis of known models or of models determined by examination, of the object (3) to be examined.

29. The method as claimed in claim 27, characterized by modeling the object (3) to be examined with the aid of a scalar or vectorial network analysis, wherein a multiplicity of spatially-resolved concentrated equivalent circuits is determined and superimposed.

30. The method as claimed in claim 27, characterized by evaluation of the detected signals with the aid of a quantitative microscopy of the impedances by means of spatially-resolved determination of the electrical and/or magnetic behavior of the object (3), for example for the determination of material properties.

31. The method as claimed in claim 27, characterized by additionally coupling laser light onto the measuring tip (5) for coupling in energy and/or reference signals and/or coupling in laser light onto the object (3) for reflection or transmission measurement.

32. The method as claimed in claim 27 for examining integrated microelectronic circuits.