Ultra-low frequency laser voltage imaging of mixed-signal designs
Ultra-low frequency laser voltage imaging of mixed-signal designs
Wednesday, November 8, 2017: 8:25 AM
Ballroom A (Pasadena Convention Center)
Summary:
During the last years laser reflectance modulation measurements (i.e. LVI, CW-SIP etc.) have become indispensable tools for analysis of logic circuits at frequencies in the megahertz range. In this paper we present a method to extend the usefulness of these methods to mixed signal circuits driven at ultra-low frequencies in the kilohertz range. We show that by toggling the main power-supply, information of the electric behavior can be easily obtained from analog structures, removing the need for tester-based stimulation. This method proved especially fruitful for the debugging of chip start-up failures. We demonstrate this on a case where a defect in the analog chip part shuts down the digital part of the chip, thus preventing methods such as the read-out of error registers or the use of scan chains. Conventional methods like photon emission microscopy and thermal laser stimulation were not successful at finding the problem. Laser-voltage imaging (LVI) of the analog circuit at key locations while toggling the chip power supply in the kilohertz range led directly to the failing net.
During the last years laser reflectance modulation measurements (i.e. LVI, CW-SIP etc.) have become indispensable tools for analysis of logic circuits at frequencies in the megahertz range. In this paper we present a method to extend the usefulness of these methods to mixed signal circuits driven at ultra-low frequencies in the kilohertz range. We show that by toggling the main power-supply, information of the electric behavior can be easily obtained from analog structures, removing the need for tester-based stimulation. This method proved especially fruitful for the debugging of chip start-up failures. We demonstrate this on a case where a defect in the analog chip part shuts down the digital part of the chip, thus preventing methods such as the read-out of error registers or the use of scan chains. Conventional methods like photon emission microscopy and thermal laser stimulation were not successful at finding the problem. Laser-voltage imaging (LVI) of the analog circuit at key locations while toggling the chip power supply in the kilohertz range led directly to the failing net.