Mid-Infrared Ellipsometry for High Aspect Ratio Semiconductor Process Control Applications

Optical critical dimension metrology (OCD) has been a critical process control tool in the semiconductor industry for many years. Traditional OCD measurement platforms operate within the ultraviolet to near infrared spectral range and combine Mueller Matrix spectroscopic ellipsometry spectra with RCWA simulations of complex 3-dimensional models to effectively measure subwavelength geometrical properties. In recent years‚ challenges regarding sensitivity and parameter correlation performance metrics have reduced the efficacy of the technique‚ specifically for some key VNAND technology applications with high aspect ratio structures. This situation has been remedied through the development of a spectroscopic ellipsometer which operates in the mid-infrared part of the electromagnetic spectrum. In both the lab and the field‚ it has been proven to outperform the existing OCD technologies for a number of those important applications.

In this talk‚ we shall describe the theoretical considerations that led to the change of spectral range on this unique OCD platform. We will also show a performance comparison of the two classes of OCD systems on the already explored high aspect ratio applications as well as simulations showing performance estimates as VNAND technology continues to evolve.Finally‚ a description of the technology roadmap for the product line will be described.