A novel XPS system for integration into advanced semiconductor equipment for in-line process control

A novel XPS system was developed and used for in-line control of silicon wafer cleaning. Unlike the conventional XPS systems where the electron energy analyzer and x-ray source are mounted on separate vacuum flanges, a compact single flange system was designed. The system consists of a quasi-conical two-stage electron energy analyzer with a coaxially placed x-ray source. This design provides a compact, low cost solution for the integration of the system into an analytical module and allows measurements on silicon wafers. Power supplies and control components like for conventional CMA systems are used. The control software provides measurement control, measurement data evaluation, and communication with a module controller. The XPS module was attached to a gate oxide cluster tool for process optimization in the cleaning/oxidation sequence. Measurements of F, C, and O contaminations on the cleaned wafer surface and on regrown oxides (<0.5 nm) have been performed and used for optimizing t he cleaning procedure. The sensitivity of the XPS measurements up to 0.01 monolayer and a measurement time in order of some minutes, which are sufficient for control of cleaning processes, could be achieved.