Yusuke Muraki

Evaluation of the Plasmaless Gaseous Etching Process

Introduction The precise control of the etching of various films on device surfaces is becoming increasingly important because slight changes in device structures can cause serious deterioration of their electrical properties. For example, a depression that is called a divot, in the CVD oxide of a shallow trench isolation (STI) results in increased leakage current, especially in advanced devices. The cause of the divot formation is considered to be the successive etching of the CVD oxide in the STI with hydrofluoric-based chemicals. The purpose of this successive etching is to remove the oxide on the device. The CVD oxide film has a poor structure, so the wet etch rate of the CVD oxide is greater than that of the thermal oxide. In this paper, we report a plasmaless, gaseous etching process technology that achieves a larger reduction of the etch rate of the CVD oxide than that of the conventional wet etching process. We discuss the mechanism of the reaction of this process and apply this technology to the STI formation process.

Mechanism of Plasma-Less Gaseous Etching Process for Damaged Oxides from the Ion Implantation Process

Recently, plasma-less gaseous etching processes have attracted attention for their interesting etching properties. Previously, we reported on the etching properties of theses processes for various kinds of oxides and revealed that they reduce the etch rate of the chemical-vapor-deposited (CVD) oxides more than the conventional wet etching process does [1]. Our results also revealed that depressions called divots in the CVD oxide of the shallow trench isolation (STI) became smaller in size by substituting a plasma-less gaseous etching process for the conventional wet etching process. In semiconductor manufacturing, many processes are used to remove oxides damaged during ion implantation or reactive ion etching on the device surface. Therefore, it is very important to understand the etching properties of plasma-less gaseous etching processes for damaged oxides as well as those for other kinds of oxides. In this report, we evaluate the etching properties of one particular plasma-less gaseous etching process for oxide films damaged during the ion implantation process under various conditions and discuss the mechanism of interesting etching properties for the damaged oxides.