Optical Modulator Yield via Mask Width Prediction
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Solution Overview
Problem
The manufacturing of semiconductor Mach-Zehnder-type optical modulators with multi-mode interference (MMI) waveguides faces challenges in accurately determining optical characteristics during fabrication, leading to low yield and increased costs due to the complexity of processing and the difficulty in managing the optimum MMI waveguide width, which affects the optical characteristics.
Innovation Solution
A method that includes measuring the mask width for waveguide fabrication, using machine learning to predict and determine the quality of optical characteristics, and refabricating the mask when deviations from the target width are detected, allowing for early quality assessment and process correction during manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If optical characteristics are evaluated only after completion of all fabrication processes, then manufacturing cost increases due to processing of non-defective products, but inspection during fabrication processes requires complex real-time measurement systems
Solution Approach 1:
The patent applies preliminary action by measuring the mask width before waveguide fabrication to predict optical characteristics in advance. This allows identification of potentially defective products before completing all fabrication processes, enabling early termination of processing for defective wafers and avoiding the high costs of processing and inspecting non-defective products. The key is performing the critical measurement (mask width) at the earliest possible stage in the fabrication process.
Solution Approach 2:
The patent extracts the critical quality-determining parameter (mask width) from the complex fabrication process and makes it the sole focus of inspection. Instead of attempting to measure or evaluate all optical characteristics during fabrication, the invention isolates and measures only the mask width parameter, which has been identified as the key factor determining optical performance. This simplifies the inspection system while still enabling effective quality prediction.
2Productivity
If mask width measurement and quality determination are performed during fabrication processes, then yield improves by identifying defective products early, but manufacturing process complexity increases
Solution Approach 1:
The patent replaces complex optical measurement and evaluation systems with a simpler mechanical/dimensional measurement approach. Instead of performing complex optical characteristic measurements during fabrication, the invention uses straightforward mask width dimensional measurement combined with pre-established correlation data to predict optical performance. This substitution dramatically simplifies the inspection system while maintaining effective quality control.
Solution Approach 2:
The patent performs the quality-determining measurement (mask width) in advance, before completing the waveguide fabrication process. By measuring the mask width immediately after mask formation and using pre-collected correlation data between mask width and optical characteristics, the system can predict final optical performance early in the process, enabling timely identification of defective wafers and improvement of manufacturing yield.
3Reliability
If the optimum MMI waveguide width is not accurately managed, then optical characteristics deteriorate, but maintaining strict width control increases manufacturing difficulty
Solution Approach 1:
The patent implements feedback by measuring the actual mask width, comparing it against target specifications, and using this information to predict optical characteristics. The system establishes correlation between measured mask width values and expected optical performance based on pre-collected data, providing feedback that enables quality determination without requiring extremely tight manufacturing control. This feedback mechanism allows for effective quality management even with normal manufacturing variations.
Solution Approach 2:
The patent changes the control parameter from final waveguide dimensions to mask width, which is easier to measure and control at an earlier stage in the fabrication process. By focusing control efforts on the mask width parameter rather than the final complex waveguide geometry, the system simplifies manufacturing while ensuring optical characteristic quality. The approach leverages the fact that mask width directly determines subsequent waveguide dimensions through the fabrication process.
Data Source
AI summary
Provided is an optical modulator manufacturing method capable of determining the quality of an optical modulator having MMI waveguides and realizing improvement in yield during manufacturing. Here, in waveguide fabrication processes, hard mask material deposition, soft mask material application, exposure, and hard mask fabrication are executed, and then in hard mask width length measurement, the hard mask width for fabricating the MMI waveguide is measured at one or more locations. In hard mask width quality determination based on machine learning results, the quality of optical characteristics of the chip is predicted and determined in advance, based on sample data created in advance by analyzing a relationship between the hard mask width and optical characteristics of the optical modulator, depending on whether the hard mask width is present in a permissible range of the sample data. Depending on the result of the above-mentioned determination.