Polarization Control for Pattern Defect Inspection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional pattern inspection apparatuses face difficulties in detecting defects in repetitive patterns smaller than the resolution limit of the inspection light due to polarization state disturbances caused by mirrors in the optical path, making it challenging to distinguish between pattern defects and mirror-induced disturbances.
Innovation Solution
The apparatus employs a configuration with a first and second half-wave plate, a mirror, and an objective lens to control the polarization state of ultraviolet light, ensuring that the illumination light does not introduce polarization state disturbances when reflecting off the mirror, allowing for accurate detection of pattern defects by rotating the polarization direction of the light relative to the periodic direction of the repetitive pattern.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a mirror is used in the optical path to illuminate the repetitive pattern, then the illumination can be achieved, but polarization state disturbance occurs making it difficult to distinguish pattern defects from mirror-induced disturbances
Solution Approach 1:
A half-wave plate is introduced as an intermediary optical element between the light source and the sample. This half-wave plate rotates the polarization direction of the incident light by 90 degrees, transforming the polarization state before it reaches the mirror. This intermediary component modifies the optical path to eliminate the harmful polarization disturbance caused by the mirror while preserving the illumination function.
2Measurement precision
If the polarization angle of illumination light is adjusted to be perpendicular to the longitudinal direction of line pattern to avoid polarization disturbance, then defect detection is improved, but mirror reflection still causes polarization state disturbance
Solution Approach 1:
The invention changes the polarization parameter of the incident light by 90 degrees using a half-wave plate. By rotating the polarization direction to be perpendicular to the original direction, the light reflects off the mirror without experiencing polarization disturbance. This parameter transformation eliminates the harmful effect while maintaining the ability to detect pattern defects through polarization state changes in the reflected light.
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 configuration enables the detection of pattern defects even when the pattern size is below the resolution limit, effectively differentiating between defects and mirror-induced disturbances, thereby improving the accuracy of defect inspection in nanoimprint technology.
Implementation Method 1
a first half-wave plate configured to receive an ultraviolet light linearly polarized in a first electric field oscillation direction, and output a linearly polarized light polarized in a second electric field oscillation direction obtained by rotating the first electric field oscillation direction of the ultraviolet light by an integer multiple of 90°
Implementation Method 2
a mirror configured to reflect the linearly polarized light polarized in the second electric field oscillation direction, and output a linearly polarized light polarized in a third electric field oscillation direction parallel or orthogonal to the second electric field oscillation direction
Implementation Method 3
a second half-wave plate configured to convert the linearly polarized light polarized in the third electric field oscillation direction, which has been reflected, to a linearly polarized light polarized in a fourth electric field oscillation direction by rotating the linearly polarized light polarized in the third electric field oscillation direction by an angle different from an integer multiple of 90°
Implementation Method 4
an objective lens configured to make the linearly polarized light rotated in the fourth electric field oscillation direction by the second half-wave plate illuminate the repetitive pattern formed on the substrate
Data Source
AI summary
A pattern inspection apparatus includes a first half-wave plate to receive an ultraviolet light linearly polarized in a first electric field oscillation direction, and output a linearly polarized light polarized in a second electric field oscillation direction obtained by rotating by an integer multiple of 90°, a mirror to reflect the linearly polarized light polarized in the second electric field oscillation direction, and output a linearly polarized light polarized in a third electric field oscillation direction parallel or orthogonal to the second electric field oscillation direction, a second half-wave plate to convert the linearly polarized light polarized in the third electric field oscillation direction, which has been reflected, to a linearly polarized light polarized in a fourth electric field oscillation direction by rotating by an angle different from an integer multiple of 90°.