Metrology Systems for High Aspect Ratio Structures
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Solution Overview
Problem
Current metrology techniques face challenges in measuring high aspect ratio and large lateral dimension structures due to low signal-to-noise ratios, limited light penetration, and inability to provide detailed profiles, especially for structures with micron-scale depths and dimensions, leading to inefficiencies in semiconductor device manufacturing.
Innovation Solution
A system and method utilizing a combination of ultraviolet (UV), visible, and infrared (IR) light to determine characteristics of high aspect ratio and large lateral dimension structures, employing a laser-driven plasma source to enhance light levels and penetration, and a multi-zone optical filter to control spectral output, allowing for precise measurement of complex 3D structures with improved signal-to-noise ratios and small spot size capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If optical metrology techniques operate off-axis near the critical angle to measure high aspect ratio structures, then measurement capability is improved, but signal-to-noise ratio deteriorates due to very small fraction of interrogating light reaching the feature bottom
Solution Approach 1:
The patent changes the wavelength parameter of the interrogating light to mid-infrared range (3-20 micrometers), which fundamentally alters the interaction between light and the HAR structure. This wavelength change enables deeper light penetration and significantly improves signal-to-noise ratio while maintaining measurement capability through extended wavelength range spectroscopy
Solution Approach 2:
The patent extends the optical measurement into a new dimensional space by utilizing mid-infrared wavelengths that are not traditionally used for semiconductor metrology. This dimensional extension in the electromagnetic spectrum allows light to penetrate deeper into high aspect ratio structures and provides access to vibrational modes of materials that are invisible at shorter wavelengths
2Area of stationary object
If optical CD metrology is used for large lateral dimension structures with micron scale pitch, then measurement coverage is improved, but measurement accuracy deteriorates due to multiple diffraction orders contaminating zeroth order diffraction measurements
Solution Approach 1:
The patent changes the wavelength parameter to mid-infrared range, which fundamentally alters the diffraction behavior. At these longer wavelengths, the diffraction angles for higher orders become larger and can be more easily separated from the zeroth order, or the higher orders may fall outside the detection angle range, effectively eliminating contamination while maintaining coverage of large lateral dimension structures
3Measurement precision
If shorter wavelength light is used to improve resolution of structure details, then measurement resolution is improved, but light penetration into high aspect ratio structures deteriorates
Solution Approach 1:
The patent inverts the traditional approach by using longer wavelengths (mid-infrared) instead of shorter wavelengths. This inversion counterintuitively improves both resolution and penetration depth simultaneously, because the longer wavelengths excite vibrational modes that provide strong spectral signatures while experiencing less scattering and absorption in the HAR structures
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate and high-throughput metrology of complex semiconductor structures by increasing light penetration and signal levels, providing detailed dimensional information and composition analysis, and overcoming limitations of existing techniques in measuring structures with high aspect ratios and large lateral dimensions.
Implementation Method 1
employing a laser-driven plasma source to enhance light levels and penetration
Implementation Method 2
a multi-zone optical filter to control spectral output
Implementation Method 3
detection subsystem configured to generate output responsive to light from the one or more structures due to the light directed to the one or more structures
Data Source
AI summary
Various metrology systems and methods for high aspect ratio and large lateral dimension structures are provided. One method includes directing light to one or more structures formed on a wafer. The light includes ultraviolet light, visible light, and infrared light. The one or more structures include at least one high aspect ratio structure or at least one large lateral dimension structure. The method also includes generating output responsive to light from the one or more structures due to the light directed to the one or more structures. In addition, the method includes determining one or more characteristics of the one or more structures using the output.