Defect metrology challenges at the 11-nm node and beyond

Abstract

Rapid, inline inspection of wafers and reticles for minimum pitch defects is expected to be a significant technical challenge at the 11nm node. With the possible future adoption of EUV lithography, increasingly exotic materials and complex device architectures, projecting end user requirements is a difficult feat 4 to 5 years out. The present work progresses through projections of these requirements and surveys the various options available to the industry, supported by microscopy simulations. The main conclusion is that the industry needs to support pathfinding projects to develop super-resolution techniques, wavelength scaling and highly multiplexed, high defect contrast ebeam inspection.

Optical volumetric inspection of sub-20nm patterned defects with wafer noise

“…Although optical focus-resolved three-dimensional volumetric defect detection has been described in-depth elsewhere [2][3], it is important to reiterate the required steps to better explain the results presented. A schematic of the process is shown as Fig.1 using a simulation example.…”

“…Two examples of volumetrically processed through focus differential images from Ref. [2]. The defect volumes can be visualized after thresholding, colored green online.…”

“….1 ri A Wafer noise is observed as scattering from the sample of interest due to its physical variations such as line edge roughness (LER) and line width roughness (LWR), as well as possible materials variation [2,5]. In many ways, the optical scattering behavior of wafer noise should mimic that of patterned defects.…”

“…The ITRS also reports that there are currently no known solutions for achieving desired processing speeds and capture rates [1]. In addition, it can be shown that as dimensions decrease, killer defects will eventually scatter light [2] as Mie scatterers, having intensities effectively proportional to d 6 /λ 4 (where d is the diameter of the scatter and λ is the wavelength of light) exacerbating the ongoing challenge of maintaining a sufficient signal-to-noise ratio (SNR).…”

The limits and extensibility of optical patterned defect inspection

“…Optical techniques have and continue to play an essential role in patterned wafer defect inspection [1,2]. Although brightfield and darkfield optical tools are widely used to support semiconductor manufacturing, as design rules shrink, wave properties, light interaction, and noise will tend to push these tools beyond their current capabilities.…”