Wafer Micro Roughness Measurement via Light Scattering
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for measuring micro roughness on semiconductor wafers, such as using atomic force microscopes, are time-consuming and do not account for variations in material and film thickness, which affect light scattering intensity and require calibration to match results with different measurement principles.
Innovation Solution
A surface shape measurement apparatus using a light scattering method that rotates and translates wafers at high speed, estimating micro roughness from total signals and signal ratios, and includes a calibration function to correct optical detection results using a similar sample, allowing for high-throughput measurement of entire wafer surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If atomic force microscope (AFM) is used for height measurement to obtain accurate micro roughness data, then measurement precision is improved, but measurement time increases significantly
Solution Approach 1:
The patent replaces the mechanical contact-based AFM measurement system with an optical light scattering measurement system. The light scattering apparatus uses optical fields instead of mechanical probes to measure micro roughness, enabling non-contact, high-speed measurement while maintaining measurement capability. This substitution resolves the contradiction by eliminating the time-consuming mechanical scanning process while preserving the ability to obtain micro roughness data.
Solution Approach 2:
The patent changes the measurement parameter approach by measuring light scattering intensity and its variations instead of directly measuring height profiles. By detecting changes in light scattering properties (intensity, angular distribution) caused by surface micro roughness, the system obtains measurement data through optical parameter changes rather than mechanical displacement, achieving both speed and accuracy.
2Productivity
If light scattering method is used for high speed measurement, then productivity is improved, but measurement precision deteriorates due to inability to account for material and film thickness variations
Solution Approach 1:
The patent implements a feedback mechanism where the measured light scattering intensity is used to determine film thickness, and this determined film thickness information is fed back to correct the micro roughness calculation. The system continuously adjusts the measurement interpretation based on the actual film conditions, ensuring accurate micro roughness values even when material or film thickness varies, thus maintaining precision while achieving high throughput.
Solution Approach 2:
The patent performs preliminary determination of film thickness from the light scattering intensity before using this information to correct the micro roughness measurement. By establishing the film thickness condition in advance, the system can apply the appropriate correction factors to the roughness calculation, ensuring accuracy is maintained throughout the high-speed measurement process without requiring repeated measurements.
3Measurement precision
If calibration is performed to match optical measurement results with AFM results, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent uses parameter changes in the correction coefficient to account for different material types and film thickness conditions. Instead of creating complex calibration procedures for each condition, the system adjusts the correction coefficient based on the detected film thickness and material properties, simplifying the calibration process while maintaining measurement precision across varying conditions.
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 rapid acquisition of necessary information for wafer process management by estimating micro roughness and surface roughness quickly and accurately, correcting optical measurements to align with atomic force microscope results.
Implementation Method 1
measuring a surface shape using a light scattering method
Data Source
AI summary
The invention discloses a technique that estimates micro roughness from a total sum of detection signals from plural detection systems and signal ratios, using a light scattering method. The technique rotates and translates a wafer at high speed to measure the entire surface of the wafer with high throughput. The relationship between the micro roughness and the intensity of scattered light varies according to a material of the wafer and a film thickness thereof. Moreover, calibration of an apparatus is also necessary. Thus, for instance, the invention provides a technique that has a function of correcting an optically acquired detection result using a sample which is substantially the same as a measurement target and makes the optically acquired detection result come close to a result measured by an apparatus, such as an AFM, using a different measurement principle.