Plasma Etch Endpoint Detection Using Differential Emission Waveforms
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Solution Overview
Problem
Existing plasma processing methods struggle to accurately detect the remaining film thickness of semiconductor wafers with varying base film thickness, mask film thickness, and fine shape variations, leading to inaccuracies in film thickness estimation and end point determination during etching processes.
Innovation Solution
A plasma processing apparatus and method that utilize a vacuum processing chamber, light emission detection, and a database of differential waveform patterns to calculate and determine the film thickness by weighting the differences between actual and stored patterns, allowing for precise end point determination even with multiple variations in the wafer surface shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a database of interference spectrum patterns with different base film thicknesses is used for end point determination, then the accuracy of film thickness estimation is improved, but the complexity of database preparation and synthesis increases when multiple variations (base film thickness, mask film thickness, mask width, fine shape) occur simultaneously
Solution Approach 1:
The patent segments the database preparation process by creating separate databases for different parameter variations (base film thickness, mask film thickness, mask width, fine shape) and then synthesizing them through weighted combination. This allows systematic handling of multiple variations without requiring an exponentially large comprehensive database.
Solution Approach 2:
The patent changes the approach from preparing databases for every possible combination of parameters to preparing databases for individual parameter variations and then mathematically combining them using weighted averages based on the degree of match between actual and database patterns. This reduces database complexity while maintaining accuracy.
2Adaptability or versatility
If multiple databases are synthesized to account for various film thickness variations, then the adaptability to different wafer conditions is improved, but the calculation complexity and processing time increase
Solution Approach 1:
The patent introduces dynamic weighting factors that adjust the contribution of each database based on the degree of match between the actual interference spectrum and database patterns. This allows the system to adaptively select the most relevant databases for each measurement, reducing unnecessary calculation complexity while maintaining high adaptability.
Solution Approach 2:
The patent creates simplified representations of complex wafer variations by preparing databases for individual parameter variations and then mathematically copying/combining them through weighted averaging. This approach captures the essential effects of multiple variations without requiring exhaustive databases for every possible combination.
3Adaptability or versatility
If the fine shape of semiconductor wafer surface varies (thick or thin base film, thick or thin mask film), then the measurement conditions become more diverse, but the ability to achieve highly accurate film thickness estimation deteriorates without comprehensive database coverage
Solution Approach 1:
The patent performs preliminary preparation of databases for each parameter variation (base film thickness, mask film thickness, etc.) before actual measurements. These pre-prepared databases serve as reference patterns that can be quickly compared against actual measurements, enabling accurate estimation without requiring comprehensive real-time database generation.
Solution Approach 2:
The patent uses feedback from the degree of match between actual interference spectra and database patterns to dynamically adjust the weighting factors. This feedback mechanism ensures that databases most closely matching the actual wafer conditions contribute more to the final estimation, maintaining high accuracy across diverse measurement conditions.
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
Enables highly accurate film thickness estimation and end point determination, improving manufacturing yield by accounting for variations in base film thickness, mask film thickness, and fine shape on semiconductor wafers.
Implementation Method 1
processing gas introduced into a vacuum processing chamber is converted into plasma containing ions and radicals
Implementation Method 2
an emission intensity of a specific wavelength in plasma light changes as etching of a specific film progresses
Data Source
AI summary
A plasma processing method to detect and process a thickness of the processing target film with high accuracy when a fine shape of the semiconductor wafer surface varies, including detecting a state of a processing target film of a processing target material that is processed inside a vacuum processing chamber; detecting light emission of the plasma; obtaining a differential waveform data of the light emission of the plasma; storing a plurality of pieces of differential waveform pattern data in advance; calculating an estimated value of the film thickness of the processing target film processed on the processing target material by weighting based on differences between the differential waveform data obtained and the plurality of pieces of differential waveform pattern data stored; and determining an end point of processing using the plasma based on the estimated value of the film thickness of the processing target film calculated.