New detection method of hot-carrier degradation using photon spectrum analysis of weak luminescence on CMOS VLSI

A method developed to find the weakest transistor against hot-carrier-induced degradation by counting photon emission of various wavelengths in an operating VLSI circuit is presented. The method's underlying principle is that high-energy photons emitted from the transistors are caused by hot-carrier effects. The spectral distribution of photon energy emitted from n-channel MOSFETs is studied, and is found to follow the Maxwell-Boltzmann distribution. Photon emission with about 200 nm wavelength strongly correlates with hot-carrier-induced degradation. This method was applied to the static random access memory in a microprocessor. Transistors which are estimated to be seriously degraded by hot-carrier effect were detected. This method improves the reliability of VLSI circuits without long-term testing.<
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