METHOD AND APPARATUS FOR DETECTING ENDPOINT OF LAYER REMOVAL PROCESS

摘要

PURPOSE: A method and an apparatus for detecting the endpoint of a process for removal of a target layer overlying a stopping layer are provided for in-situ endpoint detection with high detection sensitivity and extremely fast response time. CONSTITUTION: In a detection of the endpoint for removal of a target layer overlying a stopping layer, a chemical reaction product is selectively generated from at least one of the target layer and the stopping layer, and the chemical reaction product is then converted into a separate product. Subsequently, the separate product is exposed to an ionizing radiation, and an ionizing current generated by the radiation is then monitored as the target layer is removed. The change of the ionizing current indicates the endpoint of a layer removal process by corresponding to the density variation of the separate product. Preferably, the chemical reaction product may be ammonia extracted from polishing slurry by an extractor(200) when a silicon dioxide layer is removed from a silicon nitride layer by chemical-mechanical polishing. The ammonia(420) is converted into ammonium chloride by reaction with hydrogen chloride(430). The ammonium chloride contained in a carrier gas is pumped by a detector(400), and the density variation of the ammonium chloride is detected by monitoring the change of the ionizing current.