AFM Probe Circular Vibration for 3D Slope Measurement
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Solution Overview
Problem
Traditional atomic force microscopy (AFM) technologies face limitations in accurately measuring surface slopes and are sensitive to electrostatic forces and environmental drift, leading to sidewall-chattering and reduced precision in 3D pattern measurement.
Innovation Solution
The method involves vibrating the AFM probe in a circular motion around axes perpendicular and parallel to the scan direction, using dual oscillating units with a 90° phase difference and frequencies between 100 kHz to 1 MHz, to detect and control the probe's motion, acquiring surface information, and modifying the probe's movement path using a feed forward algorithm to follow the surface tangent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional PID control is used for 3D surface measurement, then measurement capability is provided, but sidewall-chattering occurs and measurement precision deteriorates
Solution Approach 1:
The probe is vibrated in two directions (scan direction and height direction) at frequencies between 100 kHz to 1 MHz to enable detection of surface position and slope through motion variation, avoiding the sidewall-chattering problem associated with traditional PID control while maintaining measurement capability
Solution Approach 2:
The probe performs periodic circular motion by combining vibrations in the scan direction and height direction with a phase difference of about 90 degrees, allowing continuous surface scanning without the instability and chattering caused by traditional feedback control methods
2Ease of operation
If raster scanning with single-direction dithering is used, then basic surface measurement is achieved, but slope detection capability is lost and control complexity increases
Solution Approach 1:
The probe vibrates in two perpendicular directions (scan direction and height direction) simultaneously, adding a dimensional aspect to the measurement that enables both position and slope detection in a single scan, eliminating the need for complex post-processing or additional control mechanisms
Solution Approach 2:
The dual-directional vibration system simultaneously performs multiple functions: detecting surface position, measuring surface slope, and navigating complex 3D terrains, replacing the need for separate detection mechanisms and simplifying the overall control system
3Measurement precision
If the probe approaches the sample surface for high-resolution measurement, then measurement precision improves, but sensitivity to electrostatic force increases
Solution Approach 1:
The high-frequency vibration of the probe (100 kHz to 1 MHz) enables measurement at optimized distances from the surface, reducing the impact of long-range electrostatic forces while maintaining sufficient resolution through detection of vibration motion variations
Solution Approach 2:
The probe vibrates before making contact with the surface, allowing detection of surface properties through motion variation in the vibration signal, thereby avoiding the need to maintain extremely close proximity that would amplify electrostatic force sensitivity
4Reliability
If environmental conditions vary, then external forces change, but drift variation increases and measurement stability deteriorates
Solution Approach 1:
The system detects variations in the probe's vibration motion caused by surface interaction forces and uses this information to control and adjust the probe position, providing real-time feedback that compensates for environmental drift and maintains measurement stability
Solution Approach 2:
The probe's own vibration motion serves as the detection signal, with surface properties extracted from variations in frequency, amplitude, or phase of the vibration, eliminating the need for separate reference measurements and enabling self-compensation for environmental variations
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
This approach enhances measurement accuracy and stability by allowing simultaneous detection of surface position and slope within a single vibration cycle, reducing probe abrasion and feedback control needs, while minimizing the impact of external forces and environmental variations.
Implementation Method 1
a first oscillating unit that makes a vibration in the scan direction of the probe, and a second oscillating unit that makes a vibration in the height direction of the sample
Implementation Method 2
the vibrations that are made by the first oscillating unit and the second oscillating unit may have a same frequency and amplitude, wherein the vibrations mutually have a phase difference of about 90°
Implementation Method 3
When the probe approaches the sample surface, attracting or pushing force (attractive or repulsive force) acts according to the gap between an atom at the tip of the probe and an atom on the sample surface
Implementation Method 4
the feed forward algorithm may include using measurement information on the surface of the sample to modify the movement path to allow a direction of movement of the probe to follow a direction of tangent line of the surface of the sample at each measurement point
Data Source
AI summary
Provided is a measuring method for an atomic force microscope that scans a surface of a sample with a probe to measure a surface property of the sample, the measuring method including detecting a motion of the probe while vibrating the probe on the surface of the sample, acquiring surface information on the sample by using a variation in the motion of the probe, and controlling the probe by using the surface information on the sample. The surface information on the sample may include a position and a slope of the surface. The vibrating of the probe on the surface of the sample may include performing a circular motion by the probe around axes perpendicular to a scan direction of the probe and to a height direction of the sample.