Wafer Inspection Using Diffusion Plate and Wavelength Selection
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Solution Overview
Problem
Existing methods for inspecting modified layers in wafers are costly and struggle with low contrast, making it difficult to determine proper layer formation, especially for smaller devices on larger wafers.
Innovation Solution
An inspecting apparatus with a light applying unit using a white light source, diffraction grating, and a pinhole mask to select a specific wavelength, combined with a diffusion plate and camera, which enhances image contrast and detects surface irregularities without increasing the diameter of the condensing lens.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the diameter of a condensing lens is increased to handle larger wafers, then the inspection coverage is improved, but the apparatus cost increases
Solution Approach 1:
A diffusion plate is introduced as an intermediary component between the light source and the wafer. This diffusion plate scatters light to create uniform illumination across the entire wafer surface without requiring a large condensing lens, thereby achieving full wafer coverage while keeping the apparatus cost low
Solution Approach 2:
The patent replaces the traditional optical condensing lens system with a diffusion-based illumination approach. Instead of using a large mechanical optical component (condensing lens) to achieve wide coverage, a diffusion plate creates uniform light distribution through light scattering, eliminating the need for expensive large-diameter lenses
2Quantity of substance
If the devices formed in wafers are made smaller, then the integration density is improved, but the contrast of modified layers in the projected image deteriorates
Solution Approach 1:
The patent changes the wavelength parameter of the light source to match the scale of smaller device features. By using shorter wavelengths (e.g., blue or UV light), the illumination resolves finer details and maintains contrast for smaller modified layers, enabling detection of sub-10micron features while preserving image quality
Solution Approach 2:
The patent applies localized optimization by selecting specific wavelength ranges that are most effective for detecting modified layers in smaller devices. The light source is tuned to provide optimal contrast for the specific size and depth characteristics of modern small-scale device modifications, rather than using broad-spectrum white 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
The apparatus provides clear image contrast for reliable detection of modified layers, reducing costs and improving inspection accuracy for wafers of various sizes.
Implementation Method 1
a diffraction grating for diffracting white light emitted by the white light source
Implementation Method 2
a pinhole mask for selecting the light of the particular wavelength from the plurality of lights of different wavelengths from the diffraction grating
Implementation Method 3
a diffusion plate disposed between the table and the camera
Data Source
AI summary
An inspecting apparatus includes a table for supporting a workpiece thereon, a light applying unit for applying light to the workpiece supported on the table, and a light detector for detecting light reflected from the workpiece. The light detector includes a camera and a diffusion plate disposed between the table and the camera.