Advanced ASIC devices with multi-level metallization and high density DRAMs with lead-on-chip (LOC) packages are becoming more difficult to analyze using emission microscopy from the Front-side of the chip (Front-side EMS). In this paper, we have found that evaluation of the wavelength spectrum from the back-side of the chip (Back-side EMS) could be used as easily as Front-side EMS. We investigated the wavelength spectrum of light emitted from the backside of the chip and the front-side of the chip, and calculated a photon counting ratio of the Back-side EMS and Front-side EMS for several different failure mechanisms. The wavelength spectra also showed that all light emissions had a component of Infrared (IR) light with wavelength longer than 900nm. The minimum ratio in the various failure mechanisms is 40%. From these data, Back-side EMS can be applied to the analysis of various failure mechanisms. Although the thickness of silicon substrate using for the spectrum measurement is from 204um to 380um, the measured values are not affected by the thickness. Therefore, in the Back-side EMS, the light emission can be detected without strict control of chip thinning.