Plasma Emission Endpoint Detection for Accurate Film Thickness
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Solution Overview
Problem
Existing plasma processing methods for semiconductor wafers struggle to accurately detect the etching end point and film thickness due to variations in base film thickness, mask film thickness, and fine shape of the wafer surface, leading to inaccuracies in film thickness estimation.
Innovation Solution
A plasma processing apparatus and method that utilizes a light emission detection unit, differential waveform data analysis, and a database of differential waveform patterns to calculate the estimated film thickness and determine the etching end point, even under varying conditions, by weighting the differential waveform data based on similarities with stored patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a database of interference spectrum patterns with different base film thicknesses is used for film thickness estimation, then the accuracy is improved for varying base film thickness, but the method cannot handle variations in mask film thickness and mask width
Solution Approach 1:
The patent segments the film structure into multiple distinct layers (base film, processing target film, mask film) and creates separate database patterns for each combination of layer thicknesses. This segmentation allows the system to independently account for variations in each layer rather than treating the structure as a whole, thereby resolving the contradiction between accurate measurement and adaptability to various structural variations.
Solution Approach 2:
The patent applies local quality by creating specific database patterns tailored to local variations in film thickness and mask dimensions. Instead of using a single generic database, the system generates multiple databases with different base film thicknesses, processing target film thicknesses, and mask film thicknesses, allowing the measurement system to adapt to the specific local conditions of each wafer being processed.
2Measurement precision
If multiple databases with different base film thicknesses are prepared and synthesized, then the film thickness estimation accuracy is improved, but the complexity of database preparation and synthesis increases
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing interference spectrum patterns for various film thickness combinations in databases before actual processing. The system prepares multiple databases with different base film thicknesses, processing target film thicknesses, and mask film thicknesses in advance, so that during production the system can directly query and synthesize the appropriate database without performing complex real-time calculations, thus improving measurement precision while managing complexity through advance preparation.
3Productivity
If the etching process is stopped at the detected end point, then the processing time is reduced, but the accuracy of achieving the desired film thickness and etching depth deteriorates due to variations in wafer fine shape
Solution Approach 1:
The patent implements feedback by continuously monitoring the interference spectrum during the etching process and comparing it against pre-prepared databases. The system calculates the film thickness at each time point based on the monitored spectrum and adjusts the etching process accordingly, allowing the process to be stopped at the precise end point that achieves the desired film thickness and etching depth even when there are variations in wafer fine shape, thus maintaining manufacturing precision while optimizing productivity.
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 highly accurate film thickness estimation and end point determination, improving manufacturing yield by accounting for structural variations in the semiconductor wafers.
Implementation Method 1
a light emission detection unit configured to detect light emission of the plasma generated inside the vacuum processing chamber
Implementation Method 2
processing gas introduced into a vacuum processing chamber is converted into plasma containing ions and radicals, and the ions and radicals are reacted with the layers formed on the surface of the semiconductor wafer, thereby performing an etching process
Data Source
AI summary
Provided is a processing state detection unit includes: a light emission detection unit configured to detect light emission of the plasma; a calculation unit configured to obtain a differential waveform data of the light emission of the plasma; a database unit that stores a plurality of pieces of differential waveform pattern data in advance; a film thickness calculation unit configured to calculate 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 by the calculation unit and the plurality of pieces of differential waveform pattern data stored in the database unit; and an end point determination unit configured to determine an end point of processing using the plasma based on the estimated value of the film thickness of the processing target film calculated by the film thickness calculation unit.