Surface Inspection Apparatus Using Polarization Correction
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Solution Overview
Problem
Existing surface inspection apparatuses struggle to inspect patterns with extremely small repetition pitches without reducing the wavelength of illuminating light, limiting the types of light sources and materials that can be used, and increasing costs.
Innovation Solution
A surface inspection apparatus that uses a light source unit emitting linearly polarized light, an optical member, a light-receiving unit, and polarization correcting members to correct polarization disruptions, allowing for reliable inspection of patterns with small pitch without reducing the light wavelength, using inexpensive light sources and materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the wavelength of the illuminating light is reduced to inspect patterns with extremely small pitch, then the measurement precision is improved, but the device complexity and cost increase due to limited light source types and expensive optical materials
Solution Approach 1:
The patent changes the polarization state parameter of the illuminating light from unpolarized or circularly polarized to linearly polarized light. This parameter change enables the use of longer wavelengths while maintaining inspection precision for small-pitch patterns, thereby avoiding the need for expensive short-wavelength light sources and complex optical systems
Solution Approach 2:
The patent introduces a polarization correcting member as an intermediary component in the optical path. This member corrects polarization disruptions caused by optical members, enabling the system to maintain effective linear polarization throughout the inspection process without requiring expensive specialized optical materials or complex alignment mechanisms
2Measurement precision
If the wavelength of the illuminating light is reduced to inspect patterns with extremely small pitch, then the measurement precision is improved, but the cost increases due to expensive light sources and optical materials
Solution Approach 1:
The patent changes the polarization state parameter of the illuminating light from unpolarized or circularly polarized to linearly polarized light. This parameter change enables the use of longer wavelengths while maintaining inspection precision for small-pitch patterns, thereby avoiding the need for expensive short-wavelength light sources and complex optical systems
Solution Approach 2:
The patent employs standard, inexpensive optical materials and light sources that would normally be insufficient for small-pitch inspection, but become effective when combined with the polarization correction mechanism. This replaces the need for expensive specialized optical components while achieving the same inspection capability
3Ease of operation
If optical members are used to guide light flux, then the light path is controlled, but polarization disruption occurs that reduces inspection reliability
Solution Approach 1:
The patent introduces a polarization correcting member as an intermediary component in the optical path. This member corrects polarization disruptions caused by optical members, enabling the system to maintain effective linear polarization throughout the inspection process without requiring expensive specialized optical materials or complex alignment mechanisms
Solution Approach 2:
The patent implements a feedback mechanism where the polarization state of light is continuously monitored and corrected by the polarization correcting member. This feedback loop ensures that polarization disruptions are compensated in real-time, maintaining inspection reliability while allowing flexible light path control through standard optical components
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 reliable inspection of patterns with small repetition pitches using inexpensive light sources and materials, maintaining high sensitivity and efficiency while simplifying the apparatus structure and reducing preparation time.
Implementation Method 1
a light source unit that emits a divergent light flux of predetermined linearly polarized light
Implementation Method 2
an optical member that allows the divergent light flux of the predetermined linearly polarized light to enter therein with a principle ray of the divergent light flux achieving a predetermined angle of incidence
Implementation Method 3
at least one polarization correcting member disposed within a light path extending between the light source unit and the light-receiving unit, which corrects a disruption of a polarization plane attributable to the optical member
Implementation Method 4
a light-receiving unit that receives linearly polarized light in a light flux from the test substrate, which is polarized along a direction perpendicular to a polarization direction of the predetermined linearly polarized light
Data Source
AI summary
A surface inspection apparatus includes: a light source unit that emits a divergent light flux of predetermined linearly polarized light to be used to illuminate a test substrate; a first optical member that allows the divergent light flux of the predetermined linearly polarized light to enter therein with a predetermined angle of incidence and then guides a light flux to the test substrate; a second optical member that allows a light flux from the test substrate to enter therein, emits a convergent light flux thereof with a predetermined angle of emergence and forms an image at a specific surface; an extraction unit that extracts linearly polarized light in the convergent light flux from the second optical member, which is perpendicular to the predetermined linearly polarized light; a light-receiving unit that receives an image of the test substrate formed via the second optical member and the extraction unit; and at least one polarization correcting member disposed within a light path extending between the light source unit and the light-receiving unit, which corrects a disruption of a polarization plane attributable to the first optical member and the second optical member.