Chemical Mechanical Planarization (CMP), a key enabler in semiconductor device scaling, is a process used to flatten a wafer surface using a combination of mechanical forces and chemical reactions that remove material from the top layers of the wafer. This planarization is critical for improving device performance and production yield.

For example, wafer planarity is required to make copper interconnects uniform in size across the wafer, and is needed for subsequent processing steps such as photolithography.

Industry Challenges

For the CMP process, maintaining good uniformity across the wafer and wafer-to-wafer is a tough yet critical challenge. In order to ensure consistent uniformity and to control the process adequately, a high-sampling rate and accurate measurements are required.

With emerging trends such as vertical and 3D devices, advanced patterning, and new materials, planarity requirements are becoming increasingly tight. As a result, there is a growing need to measure wafers at CMP steps using a metrology system with high throughput and excellent precision. Furthermore, due to a divergence of behavior between unpatterned and patterned regions of the die, a need to measure patterned regions, which better correlate to electrical performance, has become more prominent.

Nova’s Solutions

Nova is the industry leader in CMP process control. As an integral part of the production process, Nova’s integrated metrology solutions deliver the highest standards of throughput, reliability, and tool-to-tool matching.

Our in-line optical metrology technologies offer a wide range of unpatterned and patterned application solutions for current and next-generation CMP challenges.  Our Integrated Metrology (IM) solutions enable the wafer-to-wafer and within-wafer feedforward (FF) and feedback (FB) control needed for CMP across a broad application space including oxide, copper, polysilicon, and tungsten CMP. We also offer stand-alone scatterometry platforms that offer high performance solutions with maximum application flexibility.

By maximizing the extraction of information from optical spectra, our NovaFit solutions can be used to extend our optical metrology capabilities by minimizing the effects of structural complexity and providing a direct link to reference metrology. For Back End of Line (BEOL) copper CMP applications, such a direct link can be established between the post-CMP optical measurement and electrical test measurements, enabling an early prediction of device performance with a high degree of accuracy. This predictive capability complements our model-based scatterometry technology, which provides the dimensional metrology information needed to control the CMP process.