High Precision CD Matching Monitoring Technology using Profile Gradient Method for the 32 nm Technology Generation

摘要

Measurement uncertainty requirement 0.37 nm has been set for the Critical Dimension (CD) metrology tool in 32 nm technology generation, according to the ITRS. The continual development in the fundamental performance of Critical Dimension Scanning Electron Microscope (CD-SEM) is essential, as in the past, and for this generation, a highly precise tool management technology that monitors and corrects the tool-to-tool CD matching will also be indispensable. The potential factor that strongly influences tool-to-tool matching is the slight difference in the electron beam resolution, and its determination by visual confirmation is not possible from the SEM images. Thus, a method for quantitative evaluation of the resolution variation was investigated and Profile Gradient (PG) method was developed. In its development, considerations were given to its sensitivity against CD variation and its data sampling efficiency to achieve a sufficient precision, speed and practicality for a monitoring function that would be applicable to mass semiconductor production line. The evaluation of image sharpness difference was confirmed using this method. Furthermore, regarding the CD matching management requirements, this method has high sensitivity against CD variation and is anticipated as a realistic monitoring method that is more practical than monitoring the actual CD variation in mass semiconductor production line.