Picoseconds measurement of internal waveforms in integrated circuits using sampling force probing. I. Principle and demonstration

The ability to provide high frequency measurements internal to integrated circuits can be crucial to the design and failure analysis of microelectronics. As integrated circuits density and operating speed increase, obtaining information on their internal operation becomes extremely difficult using conventional contact probing methods. This paper proposes a non-contact probing technique based on pulse sampling electrostatic force microscopy for the measurement of high frequency signals at internal points in integrated circuits. Internal circuit voltages are determined by sensing the local electrostatic force on a miniature probe cantilever that is closely positioned above the circuit test point. The bandwidth of force measurement, using direct methods, is typically limited by the mechanical frequency response of the used probes. To overcome these limitations, pulse sampling methods have been proposed, which employ modulated high bandwidth sampling pulse approach. The temporal resolution of these pulse sampling methods is limited by the pulse width. Recently, a pulse width modulation approach has been presented and provides a resolution independent of the sampling pulse width. This work presents a high frequency measurement technique based on the pulse width modulation approach that utilizes a square wave modulation method. The proposed technique simplifies the implementation of the pulse width modulation approach at high frequencies and further enhances its resolution