Raman Spectroscopy for Buried Lateral Etch Depth Measurement
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Solution Overview
Problem
Current metrology techniques, such as CD-SEM and OCD, are inadequate for accurately measuring buried information and lateral cavity etch depth in semiconductor processing due to their limitations in sensitivity and reliance on complex models, especially at technology nodes below 10 nm.
Innovation Solution
A spectroscopic measurement method that directs an energy beam at a microstructure with a recessed sidewall, capturing and processing a spectroscopic response to derive a parameter representative of the lateral recess depth, using a previously established one-on-one relation to determine the depth, allowing for non-invasive and in-line measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If CD-SEM or OCD is used for measuring lateral recess depth, then measurement can be performed, but measurement precision deteriorates due to inability to sensitively detect buried information
Solution Approach 1:
The patent uses Raman spectroscopy as an intermediary technique to indirectly measure the lateral recess depth of buried structures. Instead of directly imaging the buried recess with electron or optical microscopy, the method uses laser-induced Raman scattering to detect material composition changes that correlate with recess depth, providing precise measurement without direct visual detection of the buried feature.
Solution Approach 2:
The patent replaces the mechanical/electronic scanning systems of CD-SEM with a non-contact optical spectroscopic system. By using laser illumination and Raman scattering detection, the method substitutes the electron beam-based mechanical scanning approach with an optical field-based measurement system that can penetrate and sense buried structures more effectively.
2Measurement precision
If OCD with complex models is used for measuring buried information, then measurement can be performed, but device complexity increases due to correlated geometrical parameters
Solution Approach 1:
The patent extracts the specific measurement information needed (lateral recess depth) by focusing Raman spectroscopy on detecting the composition and thickness of the first layer material. Instead of using complex models that must account for multiple correlated geometrical parameters of the entire stack, the method extracts the specific parameter of interest through material-specific Raman signal analysis, simplifying the measurement approach.
Solution Approach 2:
The patent changes the measurement parameter from direct geometric imaging (CD-SEM, OCD) to spectroscopic signal analysis. By measuring Raman peak positions, intensities, and widths that are sensitive to material composition and layer thickness, the method transforms the measurement problem from complex geometric parameter fitting to simpler spectroscopic parameter analysis with direct correlation to recess depth.
3Measurement precision
If conventional metrology methods are used for measuring lateral depth, then measurement can be performed, but productivity decreases due to measurement time and invasiveness
Solution Approach 1:
The patent enables continuous, non-invasive measurement of lateral recess depth during the etching process by using Raman spectroscopy. The laser-based measurement can be performed rapidly without stopping the manufacturing process or damaging the sample, allowing for real-time monitoring and immediate feedback to control the etching depth, thereby maintaining high productivity while ensuring measurement precision.
Solution Approach 2:
The patent performs preliminary characterization of the material stack using Raman spectroscopy before and during the etching process. By establishing the initial Raman spectral fingerprint of the structure and monitoring changes in real-time, the method enables predictive control of the etching process, allowing for precise depth control without requiring post-process measurement and correction cycles.
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 precise and fast measurement of lateral recess depth in semiconductor processing, overcoming the limitations of existing techniques by providing a direct and accurate method for monitoring etch depth during the etch process, suitable for in-line verification in semiconductor manufacturing.
Implementation Method 1
directing an energy beam at the structure, measuring a spectroscopic response generated by the interaction between the incident beam and the structure
Data Source
Figure 1a~1d
Figure 2~3
Figure 4
AI summary
The method of the invention applies a spectroscopic measurement for determining a lateral recess depth in the sidewall (11) of a microstructure (1). The structure is formed on a larger substrate (10) with the sidewall in an upright position relative to the substrate, and the recess extends essentially parallel to the substrate. The recess may be an etch depth obtained by etching a first layer (3) relative to two adjacent layers (4), the layers oriented parallel to the substrate, the etch process progressing inward from the sidewall (11). According to the method of the invention, an energy beam is directed at the structure (1). The incident beam falling on the structure generates a spectroscopic response captured and processed respectively by a detector and a processing unit. The response comprises one or more peaks related to the material or materials of the substrate (10) and the structure (1). According to the invention, a parameter is derived from said one or more peaks, that is representative of the lateral recess depth, said parameter having a previously established one-on-one relation to said depth. From the measured parameter, the depth is derived, using the previously established relation.