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

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.

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 mm 2  at 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.