Abstract: The current invention provides a method for analyzing process variations that occur during integrated circuit fabrication. Critical dimension data is collected for each layer of the integrated circuit fabrication process for a period of time and a shift indicator that indicates variation in the critical dimension data for each layer of the integrated circuit fabrication process is calculated. A machine drift significance indicator is also calculated for each machine used in each layer of the integrated circuit fabrication process, and a maximum shift of mean value for each layer of the integrated circuit fabrication process is defined. The shift indicator, the maximum shift of mean value and the machine drift significance indicator are used to determine at least one likely cause of variation in critical dimension for each layer of the integrated circuit fabrication process.

Abstract: The present invention provides a method for forming a contact opening having a rounded corner. Because the corner of the formed contact opening is rounded, a conductive material that is free of voids can be formed within the contact opening. In the present invention, a dielectric layer and a patterned photoresist layer are sequentially formed on a substrate. An isotropic etching process and a main etching process are performed to form a contact opening in the dielectric layer. A photoresist descum process is performed to remove a portion of the photoresist layer. Then, a soft etching process is performed to form a rounded corner on the top of the contact opening. The contact opening can be substantially filled with a conductive layer.