SEM Grayscale Inspection of Cell Etch Redeposition
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Solution Overview
Problem
The dry etching process in semiconductor manufacturing, particularly for forming magnetic tunnel junctions (MTJs), is uncontrollable, leading to redeposition of etched material on sidewalls which increases leakage and degrades yields, and existing inspection methods are either insensitive or destructive, limiting throughput and accuracy.
Innovation Solution
A non-destructive inspection method using grayscale images captured in situ with a SEM to assess etch redeposition on sidewalls, where image processing identifies region-of-interest pixels and scores redeposition based on gray levels, allowing for reliable and efficient evaluation of redeposition amounts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If destructive inspection methods are used to assess etch redeposition, then measurement precision is improved, but productivity decreases and manufacturing costs increase
Solution Approach 1:
The patent uses grayscale imaging to create a visual copy of the etched cell sidewalls, allowing inspection of redeposition without physically altering or destroying the sample. This optical copying approach enables repeated measurements and maintains sample integrity while providing sufficient measurement precision for quality control
Solution Approach 2:
The patent replaces mechanical or chemical destructive analysis methods with an optical imaging system. By using grayscale images captured in situ, the system substitutes physical sample preparation and destruction with non-contact optical detection, thereby maintaining measurement capability while eliminating productivity losses and additional manufacturing costs
2Device complexity
If existing inspection methods are used, then device complexity is reduced, but measurement precision and reliability deteriorate
Solution Approach 1:
The patent introduces grayscale imaging as an intermediary between the etching process and final quality assessment. This intermediate optical measurement step provides detailed information about redeposition that direct visual inspection cannot detect, improving measurement precision while adding only moderate system complexity through integration with existing semiconductor manufacturing equipment
Solution Approach 2:
The patent utilizes gray level parameters from grayscale images to quantify redeposition amounts. By analyzing variations in gray levels corresponding to different material densities and compositions on sidewalls, the system achieves high measurement precision through quantitative image analysis without requiring complex additional hardware
3Device complexity
If manual inspection methods are used, then device complexity is reduced, but loss of time increases and productivity decreases
Solution Approach 1:
The patent implements an automated image capture and analysis system that performs inspection without human intervention. The grayscale imaging and subsequent processing automatically identify and quantify redeposition, eliminating the time-consuming manual inspection process while the added automation complexity is offset by the elimination of human labor and increased throughput
4Productivity
If non-destructive inspection is used, then productivity is improved and manufacturing costs decrease, but measurement precision and detection sensitivity worsen
Solution Approach 1:
The patent creates detailed grayscale image copies of the etched structures that preserve all visual information about redeposition. This optical copying method maintains detection sensitivity by capturing subtle variations in material appearance while enabling rapid, non-destructive inspection of multiple wafers, thereby improving productivity without sacrificing measurement precision
Solution Approach 2:
The patent exploits gray level variations in the optical image to detect and quantify redeposition. Different amounts and types of redeposition manifest as distinct gray level patterns, allowing the system to maintain high detection sensitivity and measurement precision through optical contrast analysis while performing rapid non-destructive inspection
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 method enables high-sensitivity, non-destructive assessment of etch redeposition across a large number of cells, reducing manufacturing costs and increasing throughput by identifying problematic redeposition quickly and accurately, thus improving yield and workflow efficiency.
Implementation Method 1
a grayscale image of a plurality of cells on a wafer is captured, wherein the grayscale image provides a top down view and is captured in situ after etching to form the cells
Data Source
AI summary
Various embodiments of the present disclosure are directed towards a method for non-destructive inspection of cell etch redeposition. In some embodiments of the method, a grayscale image of a plurality of cells on a wafer is captured. The grayscale image provides a top down view of the cells and, in some embodiments, is captured in situ after etching to form the cells. The cells are identified in the grayscale image to determine non-region of interest (non-ROI) pixels corresponding to the cells. The non-ROI pixels are subtracted from the grayscale image to determine ROI pixels. The ROI pixels are remaining pixels after the subtracting and correspond to material on sidewalls of, and in recesses between, the cells. An amount of etch redeposition on the sidewalls and in the recesses is then scored based on gray levels of the ROI pixels. Further, the wafer is processed based on the score.