Slit-Image Height Measurement for Transparent Specimen Top Surfaces
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Solution Overview
Problem
In electron beam lithography, accurately measuring the height of a transparent material's top surface is challenging due to the inability to distinguish between slit images reflected by the top and back surfaces, leading to inaccurate height determination.
Innovation Solution
A height measuring device that emits light obliquely and forms a slit image on the specimen, using an imaging element to detect reflected light and an arithmetic unit to identify and determine the slit image from the top surface based on its position, preventing misidentification with the back surface image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If light is emitted obliquely to form a slit image on the specimen for height measurement, then measurement capability is enabled, but for transparent materials multiple slit images (top surface and back surface reflections) are detected making accurate measurement difficult
Solution Approach 1:
The patent segments the detection task by separately identifying slit images from different surfaces (top surface vs. back surface) based on their positional differences on the detection surface. The arithmetic unit processes multiple detected slit images by distinguishing their origins through position analysis, enabling separate measurement of each surface's contribution.
Solution Approach 2:
The patent utilizes the spatial dimension on the detection surface to differentiate between reflections from the top surface and back surface. By analyzing the position of slit images in the detection plane, the system can identify which image corresponds to which surface, converting a one-dimensional height measurement problem into a two-dimensional position analysis problem.
2Measurement precision
If the position of the slit image is used to determine height, then height information can be obtained, but misidentification of the slit image source (top vs. back surface) leads to measurement errors
Solution Approach 1:
The arithmetic unit implements a feedback mechanism by detecting multiple slit images, analyzing their positions, and using this information to identify which image corresponds to the top surface reflection. The system continuously monitors and adjusts its identification based on the detected positions, ensuring reliable height measurement even when multiple reflections are present.
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 accurate measurement of the top surface height by clearly distinguishing the slit image from the top surface, preventing errors caused by back surface reflections and improving measurement precision.
Implementation Method 1
a light source that emits light in a direction oblique to a top surface of a specimen
Implementation Method 2
an imaging element that detects reflected light reflected by the specimen
Data Source
AI summary
A height measuring device includes a light source that emits light in a direction oblique to a top surface of a specimen, a slit that shapes the light from the light source to form a slit image on the specimen, an imaging element that detects reflected light reflected by the specimen, and an arithmetic unit. The arithmetic unit: identifies a slit image of the reflected light reflected by the top surface of the specimen from among a plurality of slit images based on respective positions of the plurality of slit images on a detection surface of the imaging element; and determines the height of the top surface of the specimen based on the position of the slit image of the reflected light reflected by the top surface of the specimen on the detection surface.