Layer Thickness Measurement Using Array Detector Stripes
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Solution Overview
Problem
Current methods for determining the thickness of layers in sample stacks, such as SOI wafers, are limited by their accuracy, speed, and lateral resolution, particularly when considering the influence of multiple layers, and often require extensive spectral evaluation that is time-consuming and costly.
Innovation Solution
An assembly and method utilizing an array detector with parallel stripes, where each section detects light in a specific wavelength range, and the sample stack is moved to ensure each point is measured across multiple wavelength ranges, allowing for simultaneous and accurate determination of layer thickness with high speed and sub-micron resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ellipsometric measurements are used to determine layer thickness, then measurement accuracy is improved, but measurement time increases significantly and spatial resolution is restricted
Solution Approach 1:
The optical spectrum is segmented into multiple wavelength ranges, with each range detected by a dedicated detector element or group of elements. This allows simultaneous measurement at multiple wavelengths without requiring sequential scanning, thereby maintaining high measurement accuracy while significantly improving measurement speed and productivity.
Solution Approach 2:
The invention transitions from sequential spectral measurement (one dimension in time) to parallel spectral measurement (adding spatial dimension through array detectors). By using multiple detector elements that simultaneously capture different wavelength ranges, the system achieves both high accuracy and high speed measurement.
2Measurement precision
If spectral reflectometry with many wavelength data points is used, then measurement accuracy is improved, but measurement speed decreases making it unsuitable for high speed mapping
Solution Approach 1:
The spectral range is divided into multiple segments, each detected simultaneously by different detector elements. This segmentation approach captures sufficient spectral information for accurate thickness measurement while reducing the total measurement time by eliminating sequential scanning requirements.
Solution Approach 2:
Multiple wavelength measurements that would traditionally be taken sequentially are merged into a single simultaneous measurement event using array detectors. This combining of measurements across the spectral range achieves high accuracy without the time penalty of sequential acquisition.
3Device complexity
If conventional optical methods are used for layer thickness measurement, then equipment complexity is reduced, but the ability to account for multiple layer influences and achieve high lateral resolution is limited
Solution Approach 1:
The detector array is segmented into multiple elements or groups, each responsible for detecting specific wavelength ranges. This segmentation enables simultaneous multi-wavelength measurement with high lateral resolution while maintaining relatively simple optical hardware without requiring complex sequential scanning mechanisms.
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 approach enables accurate and efficient measurement of layer thickness with high speed and sub-micron lateral resolution, reducing the need for time-consuming methods like ellipsometry and spectral reflectometry, and effectively accounts for the influence of multiple layers.
Implementation Method 1
detecting the intensity of light reflected by the sample stack of layers
Implementation Method 2
The intensity of light reflected by the sample stack of layers in defined wavelength ranges
Data Source
AI summary
A method and assembly for determining the thickness of layers of a sample stack influencing the intensity of reflected light from a light source. The thickness is determined from the intensity detected by an array detector with a plurality of detector elements in lines and columns. The detector comprises a plurality of sections in the form of parallel stripes, the stripes detecting the light reflected by the sample stack of layers simultaneously. Light of one selected wavelength range only is detected by each of the plurality of sections of the detector. The image of the sample stack on the detector or of the parallel stripes is moved in a direction perpendicular to the longitudinal direction of the parallel stripes such that each point of the sample stack is detected at least once in each of the different wavelength ranges.