Quantitative high frequency-electric force microscope testing of monolithic microwave integrated circuits at 20 GHz

Recently, a High Frequency-Electric Force Microscope (HF-EFM) test system has been successfully used for contactless testing of internal electric signals in Monolithic Microwave Integrated Circuits (MMIC). Measurements up to operating frequencies of 110 GHz have been demonstrated. The underlying measurement principle is the heterodyne mixing technique which transforms HF-signals in a lower frequency range, where the detected signal can be easily processed further on. Different ways exist to realize the heterodyne mixing technique in an EFM. The normally used way, the so-called conventional mixing technique (CMT), generates the low frequency signal by mixing the to be measured MMIC internal test point signal with a second HF-signal of a slightly different frequency which is applied to the probe. However, this way of generating the low frequency signal excludes up to now a quantitative measurement of a high frequency test point signal. In this paper an alternative mixing technique, the so-called amplitude modulation technique (AMT), is introduced in order to overcome the disadvantages of the CMT and, additionally, simplify the experimental set up. Quantitative high frequency measurements at 20 GHz demonstrate the efficiency of this new technique.