Plasma Etch Endpoint Detection Using Multi-Wavelength Wafer Reflection
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Solution Overview
Problem
Existing plasma etching technologies struggle to accurately measure residual film thickness and processing depth due to variations in film structure, detection position, selection ratio of etching targets, and fluctuations in light sources, leading to reduced accuracy in determining the end of the etching process.
Innovation Solution
A plasma processing apparatus and method that utilizes a receiver to detect light with multiple wavelengths from the wafer surface at predetermined times, comparing the intensity data with pre-acquired comparative data to select similar film structures, enabling accurate detection of residual film thickness and processing depth by quantifying similarity and minimizing deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single database of reflected light patterns is used for film thickness measurement, then the measurement process is simple, but the measurement accuracy decreases when device structures vary between wafers
Solution Approach 1:
The patent segments the single database into multiple databases, each corresponding to a specific device structure type. The system divides the database management into structured categories (first database for initial patterns, second database for updated patterns) and selects appropriate databases based on detected device structure types, thereby maintaining measurement accuracy across varying wafer structures while keeping each individual database manageable in size and complexity
Solution Approach 2:
The system performs preliminary actions by pre-acquiring and storing reflected light patterns for multiple device structure types in separate databases before actual measurement. The management device detects the device structure type in advance and selects the corresponding pre-prepared database, avoiding the need to handle all possible structure variations in a single database and ensuring accurate measurements are ready when needed
2Adaptability or versatility
If reflected light patterns from multiple device structures are combined in one database, then comprehensive coverage is achieved, but the reflected light patterns do not match and measurement accuracy is lost
Solution Approach 1:
The patent applies segmentation by creating separate databases for different device structure types rather than combining all structures in one database. Each database contains reflected light patterns specific to its designated structure type, ensuring that patterns within each database are compatible and can be accurately matched during measurement, while the system as a whole maintains versatility by supporting multiple structure-specific databases
Solution Approach 2:
The system changes the parameter of database selection based on the detected device structure type. By identifying the specific device structure type first and then selecting the corresponding database, the system adapts the measurement process to match the appropriate reflected light patterns, ensuring high accuracy for each specific structure type while maintaining comprehensive coverage across multiple types
3Device complexity
If plasma light is used as the light source, then the system is simple, but light amount fluctuation reduces measurement accuracy
Solution Approach 1:
The patent introduces an intermediary element - a light amount correction value - that mediates between the plasma light source and the reflected light measurement. The system acquires light amount correction values that compensate for plasma light fluctuations and applies these corrections to the measured reflected light patterns, thereby maintaining measurement accuracy despite using the simple plasma light source without requiring an external stable light source
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
The apparatus achieves high-accuracy detection of residual film thickness and processing depth by correlating light intensity patterns with pre-acquired data, effectively addressing variations in film structure and light source fluctuations.
Implementation Method 1
a process monitor configured to measure reflected light from a wafer during the processing
Implementation Method 2
a high-frequency electric field generated by a high-frequency power supplied from a high-frequency power source is supplied to the processing chamber, atoms or molecules of the introduced gas are excited to be ionized or dissociated into plasma
Implementation Method 3
anisotropic or isotropic etching for the film layer of the processing target is performed due to a physical reaction such as sputtering by charged particles such as ions in the plasma
Data Source
AI summary
A plasma processing apparatus and method in which light with a plurality of wavelengths from a surface of a wafer at a plurality of predetermined times during processing for the wafer as the processing target is received, and when a processing amount is detected by using a result acquired by comparing data indicating intensities of the received light with the plurality of wavelengths with comparative data acquired in advance and indicating intensities of the light with the plurality of wavelengths, a similarity in wafers is quantified based on the data indicating the intensities of the light with the plurality of wavelengths of light, and the processing amount is detected by comparing at least one piece of data selected according to the quantified similarity with the data indicating the intensities of the light with the plurality of wavelengths acquired during the processing for the plurality of wafers.