Scanning Probe Microscopy Subsurface Imaging
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Solution Overview
Problem
Current imaging technologies, such as standard atomic force microscopy, are unable to effectively detect nanometer-scale semiconductor structures buried beneath hard or dense layers, lacking the necessary resolution and non-destructive capabilities for subsurface inspection in semiconductor device production.
Innovation Solution
A method utilizing a cantilever-based scanning probe microscopy system with high-frequency vibrational input signals (10 MHz to 10 GHz) and amplitude modulation, allowing for non-destructive detection of subsurface structures by sensing the additional force induced by indentation, which is sensitive to nanometer-scale features beneath surface layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If standard atomic force microscopy methods are used to image surface features, then surface topography can be measured, but subsurface structures buried underneath hard material layers cannot be detected
Solution Approach 1:
The patent applies high-frequency mechanical vibrations (10 MHz to 10 GHz) to the probe tip to induce resonant oscillations. These vibrations enable the probe to sense subsurface structures through elastic wave propagation and impedance changes, allowing detection of buried semiconductor features that are invisible to conventional static AFM methods.
Solution Approach 2:
The patent changes the operating parameters of the AFM system by using dynamic vibrational modes instead of static contact mode. By modulating the probe tip vibration frequency and amplitude, and by detecting resonance frequency shifts and quality factor changes, the system gains sensitivity to subsurface mechanical properties and buried structures.
2Adaptability or versatility
If high energy electron beams are used in transmission electron microscopy to image subsurface structures, then subsurface imaging capability is achieved, but the devices are damaged
Solution Approach 1:
The patent replaces the high-energy electron beam mechanism with a mechanical vibration-based sensing mechanism. The AFM probe uses mechanical oscillations and force sensing to image subsurface structures, eliminating the ionizing radiation and high-energy particle damage inherent in electron microscopy while maintaining subsurface imaging capability.
Solution Approach 2:
The patent employs a non-destructive sensing mechanism where the probe tip itself serves as both the excitation source and the sensor. The probe's own vibrations are used to probe subsurface structures, and the same probe detects the response, providing self-contained, damage-free measurement.
3Measurement precision
If the probe tip is in contact with the surface to sense vibrations, then motion of the probe tip can be detected, but the detection is limited to surface features only
Solution Approach 1:
By applying high-frequency vibrations to the probe tip and analyzing the resonant response, the system can detect elastic waves that propagate from subsurface structures back to the surface. The vibration-based mechanism allows energy to penetrate deeper into the sample, enabling detection at depths of hundreds of nanometers beyond the surface.
Solution Approach 2:
The patent transitions from two-dimensional surface imaging to three-dimensional subsurface imaging by utilizing the depth dimension through elastic wave propagation. The vibrational technique allows information from different depths to be encoded in the frequency and amplitude response of the probe, enabling depth-resolved imaging capability.
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 high-resolution imaging of buried semiconductor structures with depth sensitivity up to hundreds of nanometers and hardness resolution down to 0.1%, suitable for detecting features as small as 0.1 nanometers, and applicable to both soft and hard material layers, facilitating non-destructive inspection during semiconductor device manufacturing.
Implementation Method 1
applying, using a transducer, a vibrational input signal to the sample
Implementation Method 2
sensing, while the probe tip is in contact with the surface, an output signal indicative of motion of the probe tip due to vibrations at the surface induced by the vibrational input signal
Data Source
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AI summary
The present document relates to a method of detecting structures on or below the surface of a sample using a probe including a cantilever and a probe tip, the cantilever being characterized by one ore more normal modes of resonance including a fundamental resonance frequency, the method including: applying, using a transducer, a vibrational input signal to the sample; sensing, while the probe tip is in contact with the surface, an output signal indicative of motion of the probe tip due to vibrations at the surface induced by the vibrational input signal; wherein the vibrational input signal comprises at least a first signal component having a frequency within a range of 10 to 100 megahertz; and wherein the vibrational input signal is amplitude modulated using at least a second signal component having a modulation frequency below 5 megahertz. The present document further relates to a scanning probe microscopy method.