Dark-Field Inspection Calibration Using Chemical Microroughness
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Solution Overview
Problem
Current dark-field inspection apparatuses face challenges in accurately calibrating their haze measuring function due to the need for submicroscopic microroughness on calibration wafers, leading to variations in measurement capability among apparatuses and difficulties in ensuring measurement accuracy over time.
Innovation Solution
A reference wafer with submicroscopic microroughness is created using a chemical solution, calibrated using a scanning-type probe microscope, and measured with an atomic-level microscope to simulate and adjust the haze, ensuring accurate calibration of the dark-field inspection apparatus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If local etching with active-species gas is used to form microroughness on the reference wafer, then microroughness can be formed on the wafer surface, but the microroughness formation accuracy and uniformity are insufficient for high-precision calibration
Solution Approach 1:
The patent replaces the mechanical/physical local etching process with a chemical solution-based microroughness formation process. The chemical solution uniformly treats the wafer surface to create consistent microroughness patterns, eliminating the complexity and inaccuracy associated with local etching methods while achieving the required submicroscopic roughness for calibration.
Solution Approach 2:
The patent changes the fundamental parameter of microroughness formation from gas-phase etching to liquid-phase chemical treatment. By using chemical solutions with controlled composition and concentration, the process achieves precise and uniform microroughness formation across the wafer surface, improving manufacturing precision while simplifying the overall process.
2Measurement precision
If a reference wafer with submicroscopic microroughness is used for calibration, then measurement precision of the dark-field inspection apparatus can be improved, but measurement variability among different apparatuses persists
Solution Approach 1:
The patent creates a universal reference wafer standard that can be used across multiple dark-field inspection apparatuses. The chemically-formed microroughness provides a consistent, reproducible calibration target that ensures measurement capability consistency across different devices, enabling inter-apparatus comparability and reducing measurement variability.
Solution Approach 2:
The patent uses scanning-type probe microscope measurement data of the reference wafer's actual surface topology to simulate and generate expected haze values. This copying approach allows the creation of a standardized reference model that can be replicated across different apparatuses, ensuring consistent calibration benchmarks.
3Ease of operation
If conventional calibration methods are used, then calibration can be performed, but the ability to detect and adjust changes in measurement capability over time is insufficient
Solution Approach 1:
The patent implements a feedback mechanism where the reference wafer's actual surface topology, measured by scanning-type probe microscope, is used to simulate expected haze values. These simulated values are compared with actual measurement results, and the difference feeds back into the calibration process to adjust and correct measurement capability drift over time, ensuring long-term reliability.
Solution Approach 2:
The patent performs preliminary measurement of the reference wafer's surface topology using scanning-type probe microscope before conducting haze measurements. This preliminary action establishes a baseline and expected value framework that enables detection and correction of measurement capability changes, improving long-term stability while maintaining operational simplicity.
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 allows for the production of reference wafers with precise submicroscopic roughness, reducing measurement variability among dark-field inspection apparatuses and enabling detection and adjustment of changes in measurement capability over time, ensuring accurate microscopic area measurements.
Implementation Method 1
microroughness is formed in a chemical reaction using a chemical solution
Implementation Method 2
measuring a roughness degree of the microroughness on the surface of the reference wafer with a scanning-type probe microscope
Implementation Method 3
light is scattered in directions around the whole circumference due to roughness (asperities) of a surface of the wafer. By receiving scattered light, an average value of roughness degrees of haze can be calculated
Data Source
AI summary
A system and method for determining measurement results of a dark-field inspection apparatus up to a microscopic area. A dark-field inspection apparatus is calibrated using a reference wafer having microroughness of an irregular asperity pattern accurately formed on a surface, and the microroughness of the surface having an ensured microroughness degree. This microroughness is measured by using an AFM, and an expected haze value is obtained based on the measured value. Then, haze of the surface of the reference wafer is measured by the dark-field inspection apparatus to be inspected to obtain an actually-measured haze value, and a difference between the expected haze value and the actually-measured haze value is obtained. Based on this difference, a haze measurement parameter of the dark-field inspection apparatus is adjusted so that the actually-measured haze value and the expected haze value match each other.