Leakage effects in metal-connected floating-gate circuits

Floating-gate circuits are useful in many analog applications, although controlling the charge stored on floating gates complicates such circuits. It has been observed that when floating poly gates are connected to metal layers, initial charge is eliminated during fabrication. This Brief presents an alternative to a previously published explanation for this effect. Experiments show that leakage through deposited inter-metal dielectrics is large enough at moderately elevated temperatures to significantly affect circuit operation. Simple modeling suggests that at temperatures typical of back-end integrated circuit processing, leakage would be large enough to rapidly discharge such floating gates.