LVI detection on passive structure in advance CMOS technology: New opportunities for device analysis

For very deep submicron technologies, 45 nm and below, Photoemission microscopy suffers from decreasing signal strength due to lower voltages. Laser Voltage Imaging (LVI) technique, introduced in 2009, allows mapping frequency through the backside of integrated circuit. For 1340 nm laser wavelength, the measured reflected signal is related to charge carrier density modulation. This signal is measured on active areas at transistor level. In this paper we discuss about the LVI (Laser Voltage Imaging) signal observed on passive structures such as copper and polysilicon resistors. We describe the way to use the LVI technique, usually dedicated to frequency mapping of digital active parts, for the location of resistive leakage. The origin of this signal is investigated including charge carrier density variations and thermo reflectance effect. Experimental results on 45 nm technology are presented. We show that the ability to perform 'LVI' measurements on passive structures “open the door” for the characterization of deep submicron devices.