Improvement of Voltage Linearity and Leakage Current of MIM Capacitors With Atomic Layer Deposited Ti-Doped ZrO2 Insulators

MIM capacitors have been widely investigated as passive devices in integrated circuits. In this work, Ti-doped ZrO2 (ZTO) thin films prepared by plasma-enhanced atomic layer deposition (PEALD) are explored as the dielectrics of MIM capacitors. First, modulation of capacitance density and quadratic voltage coefficient of capacitance (
$\alpha {)}$
is achieved for the MIM capacitors by adjusting the ALD cycle ratio of TiO2/ZrO2 (Ti/Zr). The
$\alpha $
-value exhibits a decreasing trend with increasing the content of Ti, even down to a negative value. In terms of Ti/Zr=1/2, the capacitor shows a minimum
$\vert \alpha \vert $
value of 219 ppm/
$\text{V}^{{2}}$
, accompanied by a capacitance density of 11.64 fF/
$\mu \text{m}^{{2}}$
. Furthermore, an additional
$\text{O}_{{2}}$
plasma treatment (5 min) of the ZTO dielectric significantly reduces the leakage current by three orders of magnitude; meanwhile, the
$\alpha $
-value decreases by
$\sim $
42%. In a word, the optimized capacitor demonstrates good electrical properties including a capacitance density of 12.21 fF/
$\mu \text{m}^{{2}}$
,
$\alpha $
of 128 ppm/
$\text{V}^{{2}}$
, leakage current of
${7}.{85} \times {10} ^{-{7}}$
A/cm2 at 1 V, and temperature coefficient of capacitance (TCC) of 194 ppm/
$\text{V}^{{2}}$
. This is related to the passivation of oxygen vacancies in ZTO caused by
$\text{O}_{{2}}$
plasma treatment.