Optical Metrology and Inspection Challenges for Memory Devices
The design rule and structure of semiconductor memory devices have been shrinking and becoming three-dimensional as well as more and more complex, respectively. Due to these things, devices may be attacked by tiny sized surface and subsurface defects. To reduce learning cycles and improve yield in this environment and in a short time, it is needed to enhance the capture rate of the small and buried defects, and/or measure tiny wrong structures at a right process step using optical in-line MI tools. However, to detect or measure them, in some cases, short wavelength of light is not enough. If device materials and structures are composed of subwavelength metal and dielectric repeating patterns or stacks, it may be needed to use longer wavelengths of light to obtain a resonance condition instead of shorter wavelengths. In this presentation, to overcome some optical MI challenges, nanophotonic methods are discussed using a broadband light source.