Method for monitoring a semiconductor fabrication process for processing a substrate

A method for monitoring a plasma process, which comprises:

• using a first model to determine an end point of a first plasma process that is performed in a plasma;
• defining the first model with an algorithm, with a termination criterion, and with at least one predetermined measurement quantity that can be determined during the first plasma process and that is based on an intensity of at least one predetermined emission wavelength of the plasma;
• configuring the algorithm such that when the algorithm is applied to the predetermined measurement quantity that is determined, the algorithm provides a decision quantity which, upon comparison with the termination criterion, serves for determining the end point of the first plasma process;
• performing the first plasma process by using a plasma-excited gas in a plasma chamber, by introducing a substrate, which will be treated, into the plasma chamber, and by allowing the substrate to interact with the plasma-excited gas in the plasma chamber;
• during the first plasma process, determining the predetermined measurement quantity for the first model to thereby obtain a measured quantity;
• applying the algorithm of the first model to the measured quantity and determining the decision quantity;
• comparing the decision quantity with the termination criterion prescribed by the first model and terminating the first plasma process when the termination criterion is met;
• using a second model for comparatively determining the end point of the first plasma process;
• defining the second model with an algorithm, with a termination criterion, and with at least one predetermined measurement quantity that can be determined during the first plasma process and that is based on an intensity of at least one predetermined emission wavelength of the plasma;
• using an additional monitoring function for continuously assessing the first model and the second model;
• if the end point that was determined with the second model has a higher significance than the end point that was determined with the first model, then using the second model to determine an end point of a second plasma process succeeding the first plasma process;
• measuring intensities of a plurality of emission wavelengths of the plasma during the first plasma process;
• using the intensities of the plurality of the emission wavelengths as measurement quantities and continuously storing the measurement quantities in a data processing system;
• also using the data processing system for identifying the end point of the first plasma etching process;
• performing the first plasma process as a plasma etching process and providing the plasma-excited gas as a dry etching gas that etches at least parts of the substrate;
• providing the substrate with an insulating layer;
• and
• etching contact holes using the plasma etching process.