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Disusun oleh: Agustian Noor
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| bet | 50/57 | | Sana | 09.05.2021 | | Hajmi | 0.62 Mb. | | #14427 |
cv1.gif
Fig. 6.6.2 Low frequency (quasi-static) and high frequency capacitance of an MOS capacitor. Shown are, from top to bottom, the low frequency capacitance measured in the presence of ambient light (top curve), the low frequency capacitance measured in the dark, the high frequency capacitance measured in the presence of ambient light and the high frequency capacitance measured in the dark (bottom curve). All curves were measured from
left to right. The MOS parameters are Na = 4 x 1015 cm-3 and tox = 80 nm. The device area is 0.0007 cm2
The figure illustrates some of the issues when measuring the capacitance of an MOS capacitance. First of all one should measure the devices in the dark; the presence of light causes carrier generation in the capacitor which affects the measured capacitance. In addition one must avoid the deep depletion effects such as the initial linearly varying capacitance of the high frequency capacitance measured in the dark on the above figure (bottom curve). The larger the carrier lifetime, the slower the voltage is to be changed to avoid deep depletion.
The low frequency measured is compared to the theorical value in the figure below. The high frequency capacitance measured in the presence of light is also
shown on the figure. The figure illustrates the agreement between experiment and theory. A comparison of the experimental low (rather than high) frequency capacitance with theory is somewhat easier to carry out since the theoretical expression is easier to calculate while the low frequency measurement tends to be less sensitive to deep depletion effects.
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