Wafer Image Inspection via Split Optical Element TSOM
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Solution Overview
Problem
Conventional wafer inspection apparatuses face challenges in efficiently inspecting three-dimensional fine patterns on semiconductor wafers due to limitations in optical microscopy and the need for time-consuming through-focus scanning, which is costly and inefficient.
Innovation Solution
A wafer image inspection apparatus that splits the image beam to obtain multiple images at different focal positions simultaneously using a split optical element and focusing optical system, enabling through-focus scan optical microscopy (TSOM) for rapid defect detection in three-dimensional patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single image pick-up element is used to photograph the wafer, then the device complexity is reduced, but the time taken to inspect the entire wafer becomes very long
Solution Approach 1:
The patent divides the single image pick-up element into multiple unit image pick-up elements arranged in a matrix formation, creating a focal plane array. This segmentation allows simultaneous capture of multiple wafer areas, dramatically increasing inspection speed while maintaining manageable device complexity through modular architecture
Solution Approach 2:
The patent transitions from a single-point imaging approach to a two-dimensional array of image pick-up elements, adding spatial dimensionality to the inspection process. This dimensional expansion enables parallel inspection of multiple wafer regions simultaneously, resolving the contradiction between device simplicity and inspection productivity
2Productivity
If a high-capacity image pick-up element is used to increase wafer coverage area, then the inspection time is reduced, but the time taken by the computer system to analyze the image increases
Solution Approach 1:
By segmenting the imaging function into multiple independent unit image pick-up elements, the patent enables parallel processing of image data from different wafer areas. Each unit element can be analyzed independently by the computer system, reducing the total analysis time compared to processing a single large image from a high-capacity element
Solution Approach 2:
The patent enables continuous inspection by capturing multiple images at different focal positions simultaneously using the focal plane array, allowing the computer system to process images in parallel without interruption, thereby maintaining continuous productive action throughout the inspection process
3Area of moving object
If multiple unit image pick-up elements are disposed closely to form a focal plane array, then the wafer area that can be photographed once is increased, but it becomes practically difficult to install lead wires and dispose elements closely
Solution Approach 1:
The patent implements a nested structure where multiple unit image pick-up elements are arranged in a compact matrix formation within the focal plane. This nesting approach maximizes the wafer coverage area while maintaining a compact overall structure that is feasible to manufacture and install, resolving the contradiction between coverage area and manufacturing ease
Solution Approach 2:
The patent introduces an optical element (beam splitter or prism) as an intermediary to divide the wafer area into multiple regions that can be simultaneously captured by different unit image pick-up elements. This intermediary component enables the focal plane array to achieve extended wafer coverage without requiring the image pick-up elements to be disposed closer than practical installation limits
4Device complexity
If conventional optical microscopy is used to inspect three-dimensional fine patterns, then the device complexity is kept low, but the measurement precision is insufficient for accurate three-dimensional inspection
Solution Approach 1:
The patent segments the inspection process into multiple image captures at different focal positions, with each image captured by a unit image pick-up element in the focal plane array. This segmentation enables comprehensive three-dimensional inspection by combining multiple focused images, achieving high measurement precision while maintaining relatively simple optical components
Solution Approach 2:
The patent adds the focal position dimension to conventional two-dimensional optical microscopy by capturing images at multiple z-heights simultaneously using the focal plane array. This dimensional extension enables accurate three-dimensional pattern inspection without requiring complex optical systems, as the depth information is obtained through spatial separation of focal planes
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 rapid and cost-effective three-dimensional inspection of semiconductor wafers by processing multiple images at different focal positions, improving defect detection efficiency and reducing inspection time.
Implementation Method 1
Reflected light from the field of view passes through the lens unit
Implementation Method 2
an image of the photographing area (object area) of the wafer is focused on the pixel unit of an image pick-up element
Implementation Method 3
an image beam for a part to be inspected is split and a plurality of images having different focal positions is obtained at the same time
Data Source
AI summary
ProA wafer image inspection apparatus for inspecting defects of a semiconductor wafer comprises: a lighting portion for generating light; a lens portion for obtaining a wafer image, which is reflected after the light has been reflected onto a wafer to be inspected, and delivering the wafer image by lighting same in one direction; a dividing optical element for dividing the wafer image delivered from the lens portion; an image detection portion comprising a plurality of image-capturing elements, which are installed so that images which have passed through the lens portion and the dividing optical element are respectively formed on different focus positions; and an image processing portion for combining the images on different focus positions captured by the plurality of image pick-up elements to form a TSOM image, and comparing the TSOM image with a TSOM image of a normal semiconductor apparatus part to determine whether an object is defective.