CMP 공정을 위한 텅스텐 막질의 산화 거동에 관한 연구

Abstract

Tungsten oxidation is used for the removal of hard tungsten film in tungsten chemical mechanical planarization (CMP). However, the inadequate methods for tungsten oxidation have been led to some problems. In this regard, it is required to develop new approaches for control of tungsten oxidation. In this dissertation, we firstly dealt with the dissolution problem induced by use of hydrogen peroxide for low oxidation of tungsten and secondly developed new methods to overcome the problems concerned with conventional Fenton reaction which used for high oxidation of tungsten. To control of the tungsten dissolution by using hydrogen peroxide, picolinic acid as dissolution inhibitor is used to form strong chemical bonding with oxidized tungsten surface. This treatment applied to tungsten topography CMP application, resulting in selective removal of tungsten topography. For the high oxidation of tungsten, the conventional Fenton reaction is widely used in tungsten CMP. However, the working pH range of conventional Fenton reaction is limited at acidic pH due to the ferric hydroxide sludge at above pH 4. In this regard, the heterogeneous Fenton reaction via Fe substituted silica nanoparticles (NPs) with hydrogen peroxide, the Fenton-like reaction via copper ions with hydrogen peroxide, and the heterogeneous Fenton-like reaction via CuO embedded silica NPs with hydrogen peroxide are developed. These methods led to a broad working pH range from acid to neutral. The experimental results and associated theoretical approaches demonstrate these new systems can be used to benefit in designing the tungsten CMP slurries with high performance of tungsten oxidation.