Analysis of coupling noise between adjacent bit lines in megabit DRAMs

Different bit-line structures, bit-line materials, widths, spacings, and passivation materials were fabricated to analyze the effect of the coupling noise between adjacent bit lines in megabit DRAMs. Each component of total bit-line capacitance was measured to obtain the bit-line-to-bit-line capacitance and the other contributions to the total bit-line capacitance. Accelerated soft error tests were performed on each sample. The results suggest the existence of two types of noise effects. One is the READ-signal degradation just after the work-line rises. The other is the disturbance in sensing operation. The larger the ratio of the bit-line coupling capacitance to the other bit-line capacitance contributions the more serious both the noise effects are. These noise mechanisms can be explained by the charge conservation model and the simulation of sensing operation. A polycide bit-line structure is less susceptible to these noises than an Al bit line because its thickness and layer position.<
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