Improved thermal stability of nitrogen annealed sputtered hafnium oxide thin films for VLSI technology

Abstract

Purpose

High‐dielectric thin films are considered as future dielectric for Si based advanced integrated circuit technology and also for the development of organic thin film transistors and micro sensors. The conventional dielectric SiO₂ is grown by thermal oxidation of silicon whereas the HfO₂ films are grown by both physical and chemical methods. Depending on film deposition technique, the film and interface characteristics are affected. The purpose of this paper is to investigate the effect of thermal annealing in oxygen and nitrogen ambient on the electrical properties of HfO₂‐based metal oxide semiconductor (MOS) capacitor and evaluate thermal stability of the characteristics.

Design/methodology/approach

HfO₂ films are deposited by rf sputtering and Al‐HfO₂‐Si MOS capacitor fabricated. The electrical I‐V and C‐V characteristics are measured and the effect of temperature in the range of 25‐200°C is evaluated for films annealed in oxygen and nitrogen.

Findings

It is found that thermal annealing in nitrogen reduces oxide trap density and improves the temperature stability compared to the film annealed in oxygen for MOS devices. From the conductance characteristics D_it oxide trap density in the film is estimated to be 2.1×10¹¹/cm² for nitrogen and 3.23×10¹¹/cm² for oxygen, which indicates the role of nitrogen in reducing oxide traps. The thermal activation energy of electron traps is found to be about 0.19 eV for nitrogen and 0.58 eV for oxygen annealed films in the temperature range of 25‐150°C.

Originality/value

The paper examines and compares the role and effect of thermal annealing in nitrogen ambient and oxygen ambient on the electrical properties of sputtered HfO₂ thin film for improved MOS device reliability.

Citation

Nahar, R.K. and Singh, V. (2010), "Improved thermal stability of nitrogen annealed sputtered hafnium oxide thin films for VLSI technology", Microelectronics International, Vol. 27 No. 2, pp. 93-97. https://doi.org/10.1108/13565361011034777