Change in Surface Morphology of Si (100) Wafer after Oxidation with Atmospheric-Pressure Plasma

Abstract

Modern surface processing of semiconductors or oxide materials requires highly precise temporal control of each processing step. In addition, large wafers must be processed quickly for high throughput. We have developed a numerically controlled sacrificial oxidation method with atmospheric-pressure plasma using electrode arrays. In this method, we oxidized the surface of a wafer with atmospheric-pressure plasma applied precisely by an electrode array, and then dipped the wafer in HF solution to remove the surface oxide layer. The plasma process time can be controlled independently at each electrode area. The oxidation rate and surface profile of the treated wafer are crucial for precision processing. We investigated the oxidation rate of atmospheric-pressure plasma oxidation by spectroscopic ellipsometry and examined the surface morphologies of untreated and treated wafers by atomic force microscopy. The surface profile smoothness correlated with the plasma oxidation time and electrode voltage during oxidation. The surface roughness tended to increase when the sample was oxidized for longer times with higher electrode voltage. This correlation between surface roughness and oxidation time resembled the results of Si/SiO2 interfacial roughness in the case of thermal oxidation. In the plasma sacrificial oxidation process, the increase of surface roughness at the Si/SiO2 interface by plasma oxidation must be considered.