Ring Aperture Lighting Device for Semiconductor Inspection Speckle Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional inspection apparatuses for semiconductor wafers using high fps cameras face challenges in reducing inspection time due to the low luminance of halogen lamps and LEDs, resulting in high shot noise and poor image quality with significant speckle and interference patterns.
Innovation Solution
A lighting device with a ring-shaped aperture and diaphragm configuration that shields the central portion of the illumination light, using a laser as the light source, and an optical diffuser to create a ring-shaped illumination beam, which minimizes central reflection and flared light, thereby reducing speckles and interference patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If halogen lamp or LED is used as light source, then the device complexity is low, but the illumination intensity is insufficient resulting in high shot noise
Solution Approach 1:
The patent introduces a ring-shaped aperture as an intermediary optical element between the light source and the specimen. This aperture shields the central portion of the illumination light and transmits only the peripheral portion, creating a ring-shaped illumination beam. This mediator modifies the light distribution to reduce speckle and interference patterns while maintaining adequate illumination intensity for high fps camera operation.
2Reliability
If conventional illumination is used, then the device complexity is low, but speckle and interference patterns occur reducing image quality
Solution Approach 1:
The patent extracts or removes the harmful central portion of the illumination light by using a ring-shaped aperture that shields the center and transmits only the peripheral light. This extraction of the problematic central beam eliminates the source of speckle and interference patterns while retaining the useful peripheral illumination for high quality imaging.
Solution Approach 2:
The patent applies different quality characteristics to different parts of the illumination beam. The central portion is shielded to eliminate speckle and interference, while the peripheral portion is transmitted to provide illumination. This local differentiation of light quality (blocked vs. transmitted) resolves the contradiction between image quality and device complexity.
3Productivity
If high fps camera is used, then the productivity is improved, but the illumination intensity requirement increases causing shot noise
Solution Approach 1:
The patent changes the spatial distribution parameter of the illumination light by using a ring-shaped aperture to create a ring-shaped beam profile. This parameter change in light distribution (from uniform to ring-shaped) allows the peripheral light to provide sufficient intensity for high fps camera operation while the blocked central portion prevents speckle and interference patterns.
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 enhances image quality by reducing speckles and interference patterns, improving inspection accuracy and efficiency, and can be retrofitted into existing systems at a low cost.
Implementation Method 1
a ring-shaped aperture disposed along the optical path such that a central portion of the illumination light is shielded and the illumination light transmitted through the aperture has a ring-shaped cross section
Implementation Method 2
an object lens positioned downstream of the ring-shaped aperture along the optical path so as to focus the illumination light having the ring-shaped cross section on a focal plane
Data Source
AI summary
A lighting device includes a light source generating a beam of illumination light, a ring-shaped aperture shielding a central portion of the illumination light and transforming the beam of illumination light into ring-shaped illumination light, and an object lens focusing the ring-shaped illumination light such that a specimen can be illuminated with the ring-shaped illumination light. An inspection apparatus including the light device also has a beam splitter and an image sensor picking up light reflected and/or diffracted from the specimen through the beam splitter. Because a central portion of the illumination light is shielded, lens flare of light transmitted by the beam splitter and the object lens is prevented thereby preventing speckles in the image produced by the image sensor.