Semiconductor Overlay Measurement With Polarized Self-Interference Imaging
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Solution Overview
Problem
Existing semiconductor measurement devices using ellipsometry struggle to accurately measure overlays due to variations in structure sizes and gaps within the same semiconductor chip, leading to inaccurate measurements.
Innovation Solution
A semiconductor measurement apparatus is developed, comprising an illumination apparatus with a light source and polarizer, an optical assembly with an objective lens and beam splitter, and a controller. This apparatus allows for the determination of alignment states in both semiconductor chip regions and separation regions by analyzing images from first and second sensors, which include image sensors and self-interference generators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If ellipsometry is used to measure overlay by irradiating light at a fixed azimuthal angle and incidence angle, then the measurement process is simple, but measurement precision deteriorates due to overlay variation across different regions of the semiconductor chip
Solution Approach 1:
The measurement process is segmented into multiple azimuthal angle measurements (e.g., 0°, 90°, 180°, 270°) to capture overlay information from different directions. This segmentation allows the system to overcome the limitation of fixed-angle measurement and achieve comprehensive overlay assessment across varying chip regions.
Solution Approach 2:
The measurement approach transitions from a single fixed angle to multi-dimensional angular sampling by varying the azimuthal angle. This dimensional expansion enables the system to capture spatial variations in overlay across different chip regions, transforming a one-dimensional measurement into a multi-dimensional characterization.
2Measurement precision
If multiple sensors and self-interference generators are added to measure overlay in both chip regions and separation regions, then measurement precision improves, but device complexity increases
Solution Approach 1:
The first sensor is designed to perform multiple functions: it measures overlay in semiconductor chip regions and separation regions by capturing images at different azimuthal angles. This multi-functionality reduces the need for separate dedicated sensors for each measurement task, thereby controlling device complexity while maintaining high measurement precision.
Solution Approach 2:
The self-interference generator creates interference patterns using the light reflected from the sample itself, eliminating the need for separate reference beams or additional complex optical components. This self-service approach achieves precise overlay measurement without proportionally increasing device complexity.
3Device complexity
If overlay measurement is performed only in separation regions, then device complexity remains low, but measurement precision deteriorates because overlay varies across different chip regions
Solution Approach 1:
The measurement system dynamically adapts its measurement locations based on the sample structure. It automatically switches between measuring chip regions and separation regions by adjusting the illumination and detection angles, enabling comprehensive overlay assessment without requiring complex manual reconfiguration.
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 enables accurate measurement of overlays in both semiconductor chip regions and separation regions, improving the yield of semiconductor processes by directly determining the alignment state of patterns formed in the chip regions and adjusting process variables accordingly.
Implementation Method 1
light reflected from the sample
Implementation Method 2
a polarizer disposed on a propagation path of light output from the light source
Implementation Method 3
a self-interference generator disposed in a path along which light is incident on the first image sensor
Data Source
AI summary
A semiconductor measurement device may include an illumination apparatus having a polarizer on a propagation path of light output from a light source; an optical assembly including an objective lens configured to allow light passing through the polarizer to be incident on a sample and a beam splitter configured to transmit light reflected from the sample to first and second sensors; and a controller. The controller may be configured to determine an alignment state of patterns in a first region of the sample using a first original image output by the first sensor and an alignment state of patterns in a second region of the sample using a second original image output by the second sensor. The first sensor includes a first image sensor and a self-interference generator in a path along which light is incident on the first image sensor. The second sensor includes a second image sensor.