High-Bandwidth SPM Scanner with Movable Objective Lens
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Solution Overview
Problem
Conventional scanning probe microscopes (SPMs) face limitations in achieving high-resolution scans at high scan rates due to low fundamental resonant frequencies and the inability to focus and target a sensing light beam effectively, leading to compromised image quality and scan speed.
Innovation Solution
An integrated optical microscope with a scan head that includes a vertically movable objective to focus sensing light on the probe, allowing for high-resolution imaging and rapid scanning, along with a stiff and lightweight scanner with a high fundamental resonant frequency, enabling the use of smaller cantilevers and focused beam spots.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional SPM scanners are used, then sub-angstrom resolution can be achieved, but scan rates are limited to less than 30 Hz
Solution Approach 1:
The scanner is divided into three independent piezoelectric actuators (X, Y, Z scanners) that operate separately, allowing each to be optimized for specific functions. This segmentation enables the system to achieve both high resolution through precise Z-scanner control and high scan rates through independent X-Y scanner operation.
Solution Approach 2:
The invention changes the fundamental resonant frequency parameter of the scanner from conventional low values to greater than 1 kHz. This is achieved by redesigning the scanner structure with optimized piezoelectric actuator configurations and control parameters, enabling the system to operate at scan rates exceeding 50 Hz while maintaining sub-angstrom resolution.
2Area of stationary object
If larger scan areas are covered, then more sample information is obtained, but scan time increases to several minutes
Solution Approach 1:
The system performs preliminary positioning and focusing using the high-speed X-Y scanner before detailed scanning. The ability to rapidly reposition the probe over large areas (millimeter-scale samples) before initiating high-resolution scanning reduces total scan time while maintaining comprehensive sample coverage.
Solution Approach 2:
The scanner operates dynamically at frequencies greater than 1 kHz, allowing rapid scanning across large sample areas. The high fundamental resonant frequency enables the system to cover millimeter-scale samples in seconds rather than minutes, while the independent Z-scanner maintains resolution through precise vertical control.
3Object-affected harmful factors
If tracking force is reduced to minimize damage, then tip and sample integrity is maintained, but scan speed decreases
Solution Approach 1:
The system employs feedback control through the independent Z-scanner that responds to cantilever deflection signals. This feedback mechanism maintains low tracking forces by dynamically adjusting the Z-position to follow sample topography, while the high-speed X-Y scanner continues rapid horizontal scanning, achieving both force minimization and high scan rates.
Solution Approach 2:
By separating the scanning functions into independent X-Y and Z scanners, the system can optimize each for its specific role. The X-Y scanner operates at high speed with minimal vertical force, while the Z scanner handles fine force adjustments through feedback, enabling simultaneous high scan rates and low tracking forces.
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 at rapid scan rates, with scan rates exceeding 50 Hz and force control bandwidths up to 15 kHz, while maintaining high image quality and allowing for the scanning of larger samples without compromising resolution.
Implementation Method 1
Because of their resolution and versatility, AFMs are important measurement devices in many diverse fields ranging from semiconductor manufacturing to biological research by using piezoelectric scanners
Implementation Method 2
the deflection of the cantilever in response to the probe tip's interaction with the sample is measured with an extremely sensitive deflection detector, often an optical lever system
Implementation Method 3
An integrated optical microscope with a scan head that includes a vertically movable objective to focus sensing light on the probe
Data Source
Figure 1
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Figure 3A
AI summary
A high-bandwidth SPM tip scanner includes an objective (34) that is vertically movable within the scan head to increase the depth of focus for the sensing light beam. Movable optics permit targeting of the sensing light beam on the SPM's probe (12) and permit the sensing light beam to track the probe during scanning. The targeting and tracking permit the impingement of a small sensing light beam spot on the probe (12) under direct visual inspection of focused illumination beam of an optical microscope (32) integrated into the SPM (10) and, as a result, permits the use of a relatively small cantilever with a commensurately small resonant frequency. A high-bandwidth tip scanner constructed in this fashion has a fundamental resonant frequency greater than greater than 500 Hz and a sensing light beam spot minor diameter of less than 10 µm.