Cleaning of Si Surfaces by Lamp Illumination

Abstract

Abstract: Cleaning of silicon surfaces using lamp illumination in ambient air at atmospheric pressure (ROST process) was investigated. It is demonstrated that an increase of wafer temperature up to 300 o C by white light illumination for 30 seconds issufficient to remove most volatile contaminants from the Si surface. Organic contaminants originating from wafer storage and handling ambient as well as from IPA drying are easily removed by ROST. This process is very effective in suppressing uncontrolled variation of the apparent thickness of ultra-thin oxide resulting from organic contamination. Furthermore, the process is effective in removing pseudo-volatile contamination such as sulfuric acid but not non-volatile contaminants such as salts and metallic ions. In general, the efficiency of lamp cleaning decreases for contamination deposited during long wafer storage times. Introduction The concept of Si surface cleaning using lamp illumination in ambient air at atmospheric pressure was explored and preliminary results were presented in our earlier reports [1,2]. The technique is implemented using Rapid Optical Surface Treatment (ROST) apparatus [3]. The ROST uses brief illumination with halogen lamps in an ambient air to restore the chemical state of the Si surface. The main goal of lamp cleaning is to remove volatile contaminants accumulated on the Si surface during wafer processing, handling in the clean room as well as during wafer shipping and storage in plastic containers. Moreover, the ROST process is further explored in this study as a method for removing organic compounds remaining on the Si surface after IPA (isopropyl alcohol) drying. In this work we also investigated the effectiveness of ROST in reducing the surface concentration of elemental contaminants of Si surfaces found in process environment such as metallic ions, sulfur and chlorine. The introduction of the ROST technology is a result of the effort to develop inexpensive and efficient gas-phase methods of controlling surface organics andother volatile contaminants. In this experiment several new aspects of ROST cleaning are considered.