Polarized Light Surface Inspection for Semiconductor Patterns
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Solution Overview
Problem
Current methods for inspecting patterns on semiconductor wafers and liquid crystal substrates using scanning electron microscopes are time-consuming and prone to overlooking defects, especially due to the high magnification and repeated electron beam irradiation, which can lead to pattern damage and delayed feedback in correcting exposure or etching apparatus issues.
Innovation Solution
A surface inspection apparatus utilizing linearly polarized light to illuminate patterns on substrates, with the plane of vibration of the light oblique to the pattern direction, extracting perpendicular polarization components from specularly reflected light to form images and determine pattern forming conditions based on light intensity differences, allowing for rapid quality assessment and process condition specification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If scanning electron microscope is used to measure pattern sectional form by repeated electron beam irradiation, then measurement precision is improved, but inspection time becomes excessively long
Solution Approach 1:
The patent replaces the mechanical scanning electron microscope system with an optical observation system using reflected light microscopy. This substitution maintains measurement capability while dramatically reducing inspection time, as optical systems can capture entire wafer surfaces simultaneously rather than scanning point-by-point with electron beams.
Solution Approach 2:
The patent performs optical observation of pattern forms before conducting actual production exposure. This preliminary inspection allows detection of exposure apparatus troubles and pattern formation issues in advance, preventing wasted production time and enabling proactive maintenance or process adjustments.
2Measurement precision
If high observation magnification is used to inspect pattern details, then measurement precision is improved, but the area of substrate that can be inspected is reduced
Solution Approach 1:
The patent transitions from two-dimensional point-by-point electron beam scanning to three-dimensional optical field observation. By using optical systems with appropriate magnification and field of view, the entire wafer surface can be observed simultaneously, capturing all pattern forms across the substrate area in a single inspection pass.
3Measurement precision
If electron beams are applied to resist patterns for observation, then measurement precision is improved, but pattern damage occurs due to charging and discharge
Solution Approach 1:
The patent replaces the electron beam system with an optical reflection light system. This substitution eliminates the charging effect that occurs when electron beams irradiate resist patterns, as photons do not accumulate charge in the resist material. The optical system provides sufficient contrast and detail for pattern form assessment without causing damage.
Solution Approach 2:
The patent acknowledges that electron beam charging causes pattern damage, but converts this harmful effect into a beneficial diagnostic tool. By observing patterns optically before exposure, the system detects exposure apparatus troubles early, preventing worse damage during actual production. The potential harm from electron beams is avoided entirely by using optical methods for preliminary inspection.
4Loss of time
If multiple patterns are sampled for inspection due to wafer area limitations, then inspection time is reduced, but defect detection reliability is lowered
Solution Approach 1:
The patent uses optical systems with large field of view to observe the entire wafer surface simultaneously, transitioning from sampling a few points to comprehensive area inspection. This allows all pattern forms across the wafer to be captured in one inspection cycle, ensuring no defects are overlooked while maintaining efficient inspection timing.
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 quick judgment of pattern quality and specification of process conditions, reducing inspection time and preventing pattern damage, while providing swift feedback for correcting exposure or etching apparatus issues.
Implementation Method 1
an illumination means for illuminating a pattern which is formed through a predetermined pattern forming process containing a process of exposure of a resist layer formed on a subject substrate to have a periodicity with a linearly polarized light
Implementation Method 2
an extraction means for extracting a polarization component having a plane of vibration perpendicular to said plane of vibration of the linear polarization out of specularly reflected light from said pattern
Data Source
AI summary
A surface inspection apparatus includes an illumination means for illuminating a pattern formed through a predetermined pattern forming process containing a process of exposure of a resist layer formed on a substrate having a periodicity with a linearly polarized light, a setting means for setting a direction of the substrate such that a plane of vibration of the linear polarization and a direction of repetition of the pattern are obliquely to each other, an extraction means for extracting a polarization component having a plane of vibration perpendicular to that of the linear polarization out of specularly reflected light from the pattern, and an image forming means for forming an image of the surface of the substrate based on the extracted light. A pattern forming condition in the pattern forming process is specified based on the light intensity of the image of the surface of the substrate formed by the image forming means.