Surface Charge and Interface State Density on Silicon Substrates after Ozone Based Wet-Chemical Oxidation and Hydrogen-Termination

Abstract:

For more than 20 years, the application of ozone dissolved in pure deionised water (DIW-O₃) has been investigated for wafer-cleaning and resist stripping applications in the semiconductor industry [, , ]. To reduce chemical consumption and disposal costs as well as to improve cleaning efficiency, DIW-O₃ is used in semiconductor wet cleaning processes as an alternative to traditional sulphuric acid peroxide (H₂SO₄/H₂O₂) [] and RCA [] cleans. Silicon solar cell fabrication includes multiple wet cleaning steps involving large amounts of chemicals. In Si substrate manufacturing the wet-chemical oxidation of substrate surface is used mainly for three purposes: (i) the removal of surface contamination and surface micro-roughness by different cleaning and smoothing procedures in H₂O₂ containing solutions (RCA I and RCA II) [5], in H₂SO₄/H₂O₂ [4], (ii) the preparation of hydrophilic surfaces for subsequent layer deposition [,] and (iii) the fabrication of thin oxide layers []. Chemical consumption could be reduced by replacing some of these chemicals with a mixture of pure deionised water with dissolved ozone for cleaning and surface conditioning. The kinetics of wet-chemical oxidation in DIW-O₃ were recently investigated by ellipsometrical measurements of oxide thicknesses (ox>) [3,6,7], by SPV-measurements [7,], by contact angle measurements as well as by quasi-steady-state photo conductance (QSSPC) measurements [7].