Extending Lateral Resolution of Optical Profiling Beyond the - Bruker
Transcript of Extending Lateral Resolution of Optical Profiling Beyond the - Bruker
Extending Lateral Resolution of Optical Profiling Beyond the Optical Diffraction Limit
Dr. Erik Novak
Director of Technology Development
Bruker Nano Surfaces Division-- Stylus and Optical Metrology Unit
• Lateral Resolution of Microscopes
– Basics of resolution
– Methods of increasing lateral resolution
• Bruker’s ContourGT 3D Microscope
– Principle of Operation
– Enabling Technologies for resolution enhancement
• AcuityXR Measurement Mode
– How the measurement is made
– Visualization of fine features
– Improved metrology on narrow linewidths
• Conclusions
June 16, 2011 Slide 2© Copyright 2011, Bruker Inc. All Rights Reserved
Bruker Nano Surfaces Division-- Stylus and Optical Metrology Unit
Optical Systems All Blur The Objects They Image
• Two Fine Lines Become Blurred Together
• Width of the blurred image is given by
– This criteria means the first zero of one feature corresponds to the maximum of the neighboring feature
– Optical resolution improved by moving to smaller wavelengths
– Optical resolution improved by collecting more light with lenses
June 16, 2011 Slide 3© Copyright 2011, Bruker Inc. All Rights Reserved
ObjectOpticalSystem
Image
δ = 0.61λ / NA
Bruker Nano Surfaces Division-- Stylus and Optical Metrology Unit
Two Cases Will Ultimately Limit Resolution
• Detector-limited resolution
– Not enough pixels to resolve a feature
– Typical for lower magnifications (<20X)
• Optical (Diffraction) Limited Resolution
– Blur of the system limits ability to resolve a feature
– Typical for high magnification (>20X)
June 16, 2011 Slide 4© Copyright 2011, Bruker Inc. All Rights Reserved
Bruker Nano Surfaces Division-- Stylus and Optical Metrology Unit
Several Methods Increase Lateral Resolution for Detector Limited Systems
• Move to higher pixel cameras
– Slows down acquisition
– Not possible in most situations
• Combine multiple images together
– Translate object with respect to imaging system
– Determine amount translated between images and recombine
• Either case can result in superior images
June 16, 2011 Slide 5© Copyright 2011, Bruker Inc. All Rights Reserved
Bruker Nano Surfaces Division-- Stylus and Optical Metrology Unit
Diffraction Limited Resolution Presents Greater Challenges
• Fluorescent Systems Can Improve Resolution by only lighting one pixel at a time
– Technique can take hours/days to image a sample
– Only appropriate for 2D, biological data
– Zeiss has implemented this commercially with good results
June 16, 2011 Slide 6© Copyright 2011, Bruker Inc. All Rights Reserved
Bruker Nano Surfaces Division-- Stylus and Optical Metrology Unit
If the Blurring Function is Perfectly Known The Effect Can Be Removed
• Some success has been shown by changing the illumination to add additional data
– Inappropriate for general optical systems due to noise and the complexity of the structured illumination
– 100nm holes modeled here
• More common techniques are to iterate results to guess the optical blur
– Practical results have limited success due to noise and image complexity
June 16, 2011 Slide 7© Copyright 2011, Bruker Inc. All Rights Reserved
Bruker Nano Surfaces Division-- Stylus and Optical Metrology Unit
Bruker’s ContourGT 3D MicroscopesProduce 3D Images of Objects
• Microscope with specialized objectives to gain information about sample height• Scan the optics so all of the object in the field of view passes through focus• Analyze the focus scan to determine height information
June 16, 2011 Slide 8© Copyright 2011, Bruker Inc. All Rights Reserved
Bruker Nano Surfaces Division-- Stylus and Optical Metrology Unit
Bruker’s ContourGT 3D Microscopes Contain Design Feature for Enhancing Lateral Resolution
• Ultra-low noise CCD Camera
– Can achieve repeatable height maps results to below 0.01nm
• Most Stable mechanical design– Repeatable, small motions from vibration/acoustics
• Precise Focus Scan
– PZT or 0.1nm resolution stepper motor for the focus scan
• High Quality XY staging with 0.5 µm encoders
• Parfocal/Parcentric objectives for easy magnification changes
• Advanced, 64 bit software for maximum computing power
June 16, 2011 Slide 9© Copyright 2011, Bruker Inc. All Rights Reserved
Bruker Nano Surfaces Division-- Stylus and Optical Metrology Unit
AcuityXR Enhances Lateral Resolution at All Magnifications
• AcuityXR Measurements:
– Operate on measurements using phase information from the sample (PSI or HDVSI modes)
– Scan the object multiple times (at least 10)
– Combine the information from those multiple height maps
– Use advanced modeling of the optical system with the combined height map information to improve resolution
• Works for both detector limited and diffraction limited measurements
– Provides a final image with twice the pixel count provided by the camera
June 16, 2011 Slide 10© Copyright 2011, Bruker Inc. All Rights Reserved
Bruker Nano Surfaces Division-- Stylus and Optical Metrology Unit
AcuityXR Can Enhance Many Measurements
• AcuityXR Measurements are appropriate for:
– Smooth and flat samples (mirrors, wafers, polymers, thin film solar or batteries)– Smooth and curved samples (medical implants, lenses)– Smooth and stepped samples (MEMS devices, etched semiconductors…)
• AcuityXR is Not Appropriate for some samples:
– Samples with Roughness >10nm (paper, cloth, unpolished wafers, silicon solar)– Samples with large areas of missing data (PSS wafers, metal with drilled holes…)June 16, 2011 Slide 11© Copyright 2011, Bruker Inc. All Rights Reserved
Bruker Nano Surfaces Division-- Stylus and Optical Metrology Unit
AcuityXR Improves Results at Low Magnifications
• 5X Measurement of Semiconductor Wafer
June 16, 2011 Slide 12© Copyright 2011, Bruker Inc. All Rights Reserved
Bruker Nano Surfaces Division-- Stylus and Optical Metrology Unit
AcuityXR Improves Results at Low Magnifications
• 5X Measurement of Semiconductor Wafer
June 16, 2011 Slide 13© Copyright 2011, Bruker Inc. All Rights Reserved
Bruker Nano Surfaces Division-- Stylus and Optical Metrology Unit
Cleaner Edges and Finer Detail Possible on MEMS Devices
• 10X (pixel limited) magnification was used
• Superior metrology on widths, heights, area, volume is achievable
June 16, 2011 Slide 14© Copyright 2011, Bruker Inc. All Rights Reserved
Bruker Nano Surfaces Division-- Stylus and Optical Metrology Unit
June 16, 2011 15
Standard Resolution Resonator Ridges Are Highly Pixelated
© Copyright 2011, Bruker Inc. All Rights Reserved
Bruker Nano Surfaces Division-- Stylus and Optical Metrology Unit
June 16, 2011 16
AcuityXR Resolution Resonator Ridges are Sharp
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Bruker Nano Surfaces Division-- Stylus and Optical Metrology Unit
At High Magnifications 130nm Lines Can Be Distinguished
• Bruker’s 115X objective used
• Detection is 3 times higher than the diffraction limit
June 16, 2011 Slide 17© Copyright 2011, Bruker Inc. All Rights Reserved
150nm lines with 150nm spacing
130nm lines with 130nm spacing
Bruker Nano Surfaces Division-- Stylus and Optical Metrology Unit
June 16, 2011 18
Grating, Textured Bumps, and 250nm linewidth with PSI (left) and AcuityXR (right)
• 200nm grating
• 5 µm semiconductor features
• 150nm line pair
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Bruker Nano Surfaces Division-- Stylus and Optical Metrology Unit
AcuityXR Enhances Narrow Features
June 16, 2011 Slide 19© Copyright 2011, Bruker Inc. All Rights Reserved
Bruker Nano Surfaces Division-- Stylus and Optical Metrology Unit
June 16, 2011 20
AcuityXR Visually Sharpens Images
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Bruker Nano Surfaces Division-- Stylus and Optical Metrology Unit
June 16, 2011 21
AcuityXR Visually Sharpens Images
© Copyright 2011, Bruker Inc. All Rights Reserved
Bruker Nano Surfaces Division-- Stylus and Optical Metrology Unit
Greater Detail on Polymer Films is Evident
June 16, 2011 Slide 22© Copyright 2011, Bruker Inc. All Rights Reserved
Feature height is 90nm, width about 8 µm
Bruker Nano Surfaces Division-- Stylus and Optical Metrology Unit
AcuityXR Improves Metrology of Narrow Features
• Vision64 Image Segmentation Used to Characterize Linewidths of 350nm Features
June 16, 2011 Slide 23Bruker NSB Stylus and Optical Unit R&D Status Update 08OCT10 V1.4
© Copyright 2011, Bruker Inc. All Rights Reserved
Bruker Nano Surfaces Division-- Stylus and Optical Metrology Unit
June 16, 2011 Slide 24Bruker NSB Stylus and Optical Unit R&D Status Update 08OCT10 V1.4
© Copyright 2011, Bruker Inc. All Rights Reserved
Standard Contour Image Shows Rounded, Blurred Features
Bruker Nano Surfaces Division-- Stylus and Optical Metrology Unit
June 16, 2011 Slide 25Bruker NSB Stylus and Optical Unit R&D Status Update 08OCT10 V1.4
© Copyright 2011, Bruker Inc. All Rights Reserved
AcuityXR Contour Image Shows Sharp, Distinct Lines
Bruker Nano Surfaces Division-- Stylus and Optical Metrology Unit
June 16, 2011 Slide 26Bruker NSB Stylus and Optical Unit R&D Status Update 08OCT10 V1.4
Multi-Region Analysis
© Copyright 2011, Bruker Inc. All Rights Reserved
Bruker Nano Surfaces Division-- Stylus and Optical Metrology Unit
June 16, 2011 Slide 27Bruker NSB Stylus and Optical Unit R&D Status Update 08OCT10 V1.4
Standard Deviations of Results Improves Significantly
Line Width
(nm)
Volume
(um^3)
Standard Measurement
35.1631 0.0051
AcuityXR 5.2725
(6.6 times lower)
0.0014
(3.6 times lower)
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Bruker Nano Surfaces Division-- Stylus and Optical Metrology Unit
June 16, 2011 Slide 28Bruker NSB Stylus and Optical Unit R&D Status Update 08OCT10 V1.4
© Copyright 2011, Bruker Inc. All Rights Reserved
Lateral Resolution Can Be Enhanced Using AcuityXR
• Bruker’s ContourGT 3D microscopes are designed to support AcuityXR
• Multiple measurements are made on smooth samples
• Results are combined intelligently to improve resolution even when limited by diffraction
• Features down to 130nm can be imaged
• Measurement repeatability of fine features is significantly improved
Bruker Nano Surfaces Division-- Stylus and Optical Metrology Unit
16.06.2011 29
AcuityXR is Available On Various Models
Increasing Functionality and Automation
GT-K1 GT-X8GT-X3GT-K0
NPFlex Dektak D150SP9900
VCM Confocal Microscope
Bruker Nano Surfaces Division-- Stylus and Optical Metrology Unit
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June 16, 2011 Slide 30Bruker NSB Stylus and Optical Unit R&D Status Update 08OCT10 V1.4