Decomposition of drain-current variation into gain-factor and threshold voltage variations

A predictable device models should correctly handle parameter variations. Good recognition of the variation of physical parameters, which are being the sources of current variations of modern devices, is thus significantly important. In this paper, we present a practical procedure for decomposing device current variation into physical parameter variations. Based on the I-V curve measurements, two variation components: threshold voltage variation and gain-factor variation are clearly separated. Cause of gain-factor variation is further discussed with measurement results of poly-Si resistor. The impact of the variation-sources on circuit performance is also evaluated using SRAM noise margin as an example.