Ensuring advanced semiconductor device reliability using fa and submicron defect detection

INTRODUCTION Recent industry trends are placing increased requirements on the need to fully understand the thermal behavior of today’s advanced semiconductor devices to ensure long-term reliability. Due to the critical nature of applications such as 5G, automotive electronics, artificial intelligence (AI), cloud storage, and military electronic systems, they all demand higher performance while simultaneously placing increased requirements on longterm reliability. Device developments that achieve higher power levels and faster switching speeds with increased functionality are driving device features to submicron levels and increasing complexity. The resulting power densities and potential for higher operating temperatures, localized hot spots, and unanticipated time-dependent thermal anomalies are compounding the challenges of ensuring adequate reliability. Temperature has a direct impact on device mean-timeto-failure (MTTF). This can be assessed with the Arrhenius equation: MTTF = Ce−Ea/kT (Eq 1) where Ea is the activation energy, k is the Boltzmann constant and T is the absolute temperature. Figure 1, plotted for an activation energy of 1.84 eV, shows the relationship between temperature and projected MTTF for a typical advanced electronic device. In this case, a 20 degree increase in junction temperature lowers the projected MTTF by an order of magnitude. The higher power densities resulting from shrinking geometries in today’s advanced device structures can easily lead to such temperature increases. The key requirement with these devices is the ability to analyze thermal behavior on a scale consistent with their submicron geometries. While traditional thermal analysis techniques such as IR thermography and μ-Raman spectroscopy have been widely used for years, these techniques fall short due to resolution limitations incompatible with today’s advanced devices.[1,2] Relying on traditional thermal analysis techniques risks the possibility of missing important thermal anomalies or small defects that could lead to early device failure. This article describes a noninvasive thermal imaging approach based on the thermoreflectance principle. This technique can meet the spatial resolution requirements for advanced devices while also providing temporal resolution in the nanosecond range for analyzing timedependent thermal events.