Wafer Particle Detection Using Radial Laser Intensity Grading
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Solution Overview
Problem
Current methods for measuring particles on a wafer surface, such as visual inspection and particle counter devices, struggle to detect particles of nanometer size and have reduced reproducibility due to varying linear velocities across the wafer surface during rotation, making it difficult to detect particles in outer regions.
Innovation Solution
An apparatus and method that divides the wafer surface into regions with varying laser output intensities, with increased output in the second and third regions farther from the center, allowing for even detection of particles across the entire surface by adjusting the laser output based on distance from the center.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a laser is irradiated on a rotating wafer surface at constant speed, then the measurement process is simple, but particles in outer regions are harder to detect due to shorter exposure time
Solution Approach 1:
The patent applies local quality by varying the laser output intensity according to the radial position on the wafer surface. The laser output is increased in outer regions where the linear velocity is higher, creating a position-dependent quality adjustment that compensates for the shorter exposure time at the periphery while maintaining simple constant-speed rotation operation.
2Measurement precision
If the laser output is increased in outer regions, then particle detection in those regions improves, but the laser system becomes more complex
Solution Approach 1:
The patent implements parameter changes by dynamically adjusting the laser output intensity parameter based on the radial position. The controller modifies the laser power parameter in proportion to the linear velocity at each position, creating a graded intensity distribution that improves detection precision without requiring complex mechanical adjustments to the laser system itself.
3Device complexity
If visual inspection with halogen lamp is used, then the equipment is simple, but particles of nanometer size cannot be observed
Solution Approach 1:
The patent replaces the conventional halogen lamp-based visual inspection system with a laser-based detection system. This substitution enables nanometer-scale particle detection through the coherent and monochromatic properties of laser light, which provide superior resolution and detection sensitivity compared to broadband halogen illumination.
4Measurement precision
If optical microscope magnification is increased to detect finer particles, then detection precision improves, but measurement time increases and reproducibility decreases
Solution Approach 1:
The patent replaces the optical microscope system with a laser-based detection system that scans the wafer surface. This substitution eliminates the need for high magnification lenses, maintains a large measurable area, and achieves fast scanning speeds with high reproducibility by using the coherent properties of laser light to detect particles without mechanical magnification.
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 enables more accurate and reproducible detection of particles and defects on the wafer surface, particularly in the outer regions, by ensuring consistent exposure to the laser, thereby improving detection efficiency and reducing the difficulty in identifying particles in edge regions.
Implementation Method 1
irradiating a laser in a first region of a center of a surface of the rotating wafer
Implementation Method 2
measuring a laser reflected from the first to third regions of the wafer
Data Source
AI summary
An embodiment provides a method for measuring particles on a wafer surface, the method including: disposing and rotating a wafer on a stage; irradiating a laser in a first region of a center of a surface of the rotating wafer, a second region between the first region and a third region, and the third region at an edge thereof; and measuring a laser reflected from the first to third regions of the wafer, wherein a second output of the laser irradiated in the second region is larger than a first output of the laser irradiated in the first region and a third output of the laser irradiated in the third region is larger than the second output of the laser irradiated in the second region.