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

Abstract

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 ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha {)}$ </tex-math></inline-formula> is achieved for the MIM capacitors by adjusting the ALD cycle ratio of TiO2/ZrO2 (Ti/Zr). The <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> -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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert \alpha \vert $ </tex-math></inline-formula> value of 219 ppm/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{V}^{{2}}$ </tex-math></inline-formula> , accompanied by a capacitance density of 11.64 fF/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}^{{2}}$ </tex-math></inline-formula> . Furthermore, an additional <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{O}_{{2}}$ </tex-math></inline-formula> plasma treatment (5 min) of the ZTO dielectric significantly reduces the leakage current by three orders of magnitude; meanwhile, the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> -value decreases by <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim $ </tex-math></inline-formula> 42%. In a word, the optimized capacitor demonstrates good electrical properties including a capacitance density of 12.21 fF/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}^{{2}}$ </tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> of 128 ppm/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{V}^{{2}}$ </tex-math></inline-formula> , leakage current of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${7}.{85} \times {10} ^{-{7}}$ </tex-math></inline-formula> A/cm2 at 1 V, and temperature coefficient of capacitance (TCC) of 194 ppm/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{V}^{{2}}$ </tex-math></inline-formula> . This is related to the passivation of oxygen vacancies in ZTO caused by <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{O}_{{2}}$ </tex-math></inline-formula> plasma treatment.

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