Wafer Grayscale Inspection for Cell Etch Redeposition Scoring
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The dry etching process used in semiconductor manufacturing for forming magnetic tunnel junctions (MTJs) is uncontrollable, leading to redeposition of etched material on sidewalls, which increases leakage current and degrades yields.
Innovation Solution
A method for non-destructive inspection of cell etch redeposition using grayscale imaging and image processing to quantify redeposition on sidewalls, allowing for real-time assessment and decision-making on whether to rework the wafer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If dry etching is performed to form MTJs, then material is removed by ion bombardment, but etched material redeposits on sidewalls increasing leakage current
Solution Approach 1:
A cap layer is deposited over the MTJ structure before the etch process. This preliminary action creates a protective barrier that prevents etched material from redepositing on the sidewalls of the MTJ cells during the etching process, thereby eliminating the leakage current problem while maintaining etch precision
Solution Approach 2:
The cap layer acts as an intermediary protective layer between the etch process and the MTJ structure. It absorbs the harmful redeposition effects and can be selectively removed later, allowing the main structure to remain unaffected by the harmful redeposition
2Measurement precision
If traditional inspection methods are used, then redeposition can be detected, but the process is destructive and time-consuming
Solution Approach 1:
The patent replaces destructive mechanical cross-sectioning methods with non-destructive optical imaging techniques. Grayscale images are captured from the wafer surface, and image processing algorithms automatically analyze these images to detect redeposition, eliminating the need for time-consuming and destructive physical sectioning while maintaining detection accuracy
Solution Approach 2:
Instead of physically sectioning and examining the actual structure, the patent creates optical copies (grayscale images) of the wafer surface and analyzes these copies through image processing. This allows rapid inspection without touching or damaging the original sample, significantly reducing inspection time
3Reliability
If manual inspection of cross sections is performed, then redeposition can be assessed, but the wafer is destroyed and throughput is low
Solution Approach 1:
The patent replaces manual mechanical cross-sectioning and microscopy with automated optical imaging and computer-based image analysis. This substitution maintains reliable detection of redeposition while enabling rapid processing of multiple wafers, thereby increasing throughput without sacrificing assessment reliability
Solution Approach 2:
The system performs self-assessment through automated image capture and processing. The grayscale images are automatically analyzed by processing algorithms that identify redeposition patterns, eliminating the need for manual inspection and enabling the system to assess itself rapidly and reliably
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.