An Al/ZrO2/IL/n-Si (IL: interface layer) MOS capacitor has been fabricated by metal organic decomposition of ZrO2 and thermal deposition Al. We have measured parallel capacitance (Cm) and parallel resistance (Rm) versus bias voltage curves (Cm, Rm–V) at different AC signal frequency (f), and Cm, Rm–f curves at different bias voltage. The curves of Cm, Rm–f measurements show obvious frequency dispersion in the range of 100 kHz–2 MHz. The energy band profile shows that a large voltage is applied on the ZrO2 layer and IL at accumulation, which suggests possible dielectric polarization processes by some traps in ZrO2 and IL. Cm, Rm–f data are used for frequency dispersion analysis. To exclude external frequency dispersion, we have extracted the parameters of C (real MOS capacitance), Rp (parallel resistance), CIL (IL capacitance), RIL (IL resistance) and Rs (Si resistance) in a five-element model by using a three-frequency method. We have analyzed intrinsic frequency dispersion of C, Rp, CIL, RIL and Rs by studying the dielectric characteristics and Si surface layer characteristics. At accumulation, the dispersion of C and Rp is attributed to dielectric polarization such as dipolar orientation and oxide traps. The serious dispersion of CIL and RIL are relative to other dielectric polarization, such as border traps and fixed oxide traps. The dispersion of Rs is mainly attributed to contact capacitance (Cc) and contact resistance (Rc). At depletion and inversion, the frequency dispersion of C, Rp, CIL, RIL, and Rs are mainly attributed to the depletion layer capacitance (CD). The interface trap capacitance (Cit) and interface trap resistance (Rit) are not dominant for the dispersion of C, Rp, CIL, RIL, and Rs.

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The three-frequency correction method is used to extract the model parameters in a five-element model which includes MOS capacitance C, parallel resistance R p , interface layer (IL) capacitance C i , IL resistance R i , and series resistance R s . A method for the error analysis of these model parameters has been developed, using error propagation of measured capacitance C m and resistance R m . We have applied this error analysis method to a 0.3 mm × 0.3 mm Al/ZrO 2 /IL/n-Si MOS capacitor with dielectric thickness 35.9 nm. Accumulation capacitances and their errors at various frequency combinations have been calculated to study suitable frequency selection. The errors in the three-frequency correction method depend on selection of the three frequencies ( f 1 >f 2 >f 3 ) and dissipation factor D m . For large differences between frequencies f 1 and f 3 ( f 3 /f 1 ∼0.05-0.2), the f 2 value should be equal to or a little larger than the average value ( f 3 + f 1 )/2 to ensure a small error (less than 4%) in spite of large D m ∼0.20-0.31 at f 1 =1.0-1.6 MHz. For three close f 1 and f 3 ( f 3 /f 1 ∼ 0.25-0.6), small ratios for f 2 /f 1 <∼2/3 and f 3 /f 2 <∼2/3 ( f 3 /f 1 <0.44), f 2 =( f 3 +f 1 )/2 and small D m less than ∼0.20 have been suggested to ensure error less than 4%. Considering the error and possible dispersion, the difference between f 1 and f 3 should be moderate, i.e. f 3 /f 1 =0.05∼0.44. For optimal frequency selection, we suggest f 3 /f 1 =∼0.10 and f 2 =( f 3 +f 1 )/2. The frequency selection is not critical for most MOS capacitors, e.g. this sample Al/ZrO 2 /IL/n-Si capacitor. The three-frequency correction method together with error analysis is effective in extracting accurate accumulation capacitance.

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