| Summary: | 博士 === 國立清華大學 === 電子工程研究所 === 96 === The geometry effect on the flicker noise characteristics in 0.13-um single-finger and multi-finger RF MOSFETs are studied in this dissertation. First, by symmetrically extending the distance between the shallow-trench-isolation (STI) to the gate, both single-finger NMOS and PMOS presented obvious improvement on the noise characterization. As the distance increased from 0.6 um to 10 um, the average noise level reduced by more than one order of magnitude and the standard deviations improved from 5.95 dB to 1.79 dB for NMOS. To further identify the noise mechanism, the devices with asymmetrical STI-to-gate distances were also investigated. It was found that the distance in the source side has a much higher impact on the observed noise characteristics. The results suggested that the noise characterization were dominated by the STI stress induced traps for both NMOS and PMOS.
In addition, this study also reports the impact of STI on flicker noise characteristics in multi-finger RF NMOS. The drain noise current spectral density was measured in both triode and saturation regions for a more complete study. The devices with a relatively small finger width and a large finger number (W= 1 um/Nfinger= 40 and W= 5 um/Nfinger= 8) presented more pronounced G-R noise characteristics compared to those with W= 10 um/Nfinger= 4. Moreover, a wide noise level variation of more than one order of magnitude was associated with the more obvious G-R noise components. The observed trends can be explained by the non-uniform stress effect of STI and also the associated traps at the edge of the gate finger between STI and the active region. The activation energy of the traps extracted from various temperatures is in a range from EC-0.397 eV to EC-0.54 eV.
Finally, the detailed procedure of parameter extraction for BSIM4 flicker noise model was also proposed. The original BSIM4 model was revised by adding the current calibration function and noise variation model. The revised model presented a good agreement with the measured results. This study provides a way for circuit designers to predict the noise level in a more precise manner.
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