Metrology Parameter Selection for Wafer Alignment Mark Deformation
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Solution Overview
Problem
Semiconductor manufacturing processes like etching cause alignment mark deformation, leading to overlay errors in subsequent layers due to wafer scaling 'fingerprints' and alignment mark position displacements, which existing alignment systems struggle to distinguish and correct effectively.
Innovation Solution
A method to determine an optimal operational parameter setting for a metrology system by obtaining and correcting data from measurements of metrology marks on substrates, selecting a color least sensitive to alignment mark deformation, and using this setting to improve alignment accuracy and reduce overlay errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional alignment systems measure alignment marks after etching, then alignment mark positions can be obtained, but measurement precision deteriorates due to alignment mark deformation causing overlay errors
Solution Approach 1:
The patent performs alignment mark measurements before etching processes that cause deformation. By measuring alignment marks on substrates before they undergo etching, the system captures accurate positions without the degradation caused by subsequent processing. This preliminary measurement approach ensures that alignment data reflects the true mark positions without deformation artifacts.
Solution Approach 2:
The patent extracts and corrects for wafer warp effects separately from alignment mark positions. By measuring wafer warp independently and removing its contribution from the alignment measurements, the system isolates the true alignment mark positions from artifacts caused by wafer deformation, thereby improving measurement precision and reliability.
2Ease of operation
If alignment measurements are performed on deformed marks, then measurement process is simple, but manufacturing precision deteriorates due to overlay errors in subsequent layers
Solution Approach 1:
The system performs alignment measurements before etching-induced deformation occurs. By capturing alignment data in the undeformed state, the system maintains measurement simplicity while ensuring that the recorded positions are accurate representations of the intended alignment marks, thereby preventing overlay errors in subsequent processing layers.
Solution Approach 2:
The patent implements a feedback mechanism where alignment measurements taken before etching are used to guide subsequent processing steps. This feedback loop ensures that alignment information captured in the undeformed state is applied to correct for any deviations, maintaining manufacturing precision throughout the process sequence.
3Measurement precision
If multiple operational parameter settings are tested to find optimal alignment color, then measurement precision improves, but loss of time increases due to multiple measurements required
Solution Approach 1:
The patent determines the optimal alignment color and operational parameters in advance, before production measurements are taken. By pre-optimizing the measurement parameters using test substrates and analyzing the results to identify the best color and settings, the system establishes a fixed optimal configuration that can be applied to all subsequent measurements without requiring repeated optimization cycles, thereby reducing time loss while maintaining high precision.
Data Source
AI summary
A method of determining an optimal operational parameter setting of a metrology system is described. Free-form substrate shape measurements are performed. A model is applied, transforming the measured warp to modeled warp scaling values. Substrates are clamped to a chuck, causing substrate deformation. Alignment marks of the substrates are measured using an alignment system with four alignment measurement colors. Scaling values thus obtained are corrected with the modeled warp scaling values to determine corrected scaling values. An optimal alignment measurement color is determined, based on the corrected scaling values. Optionally, scaling values are selected that were measured using the optimal alignment measurement color and a substrate grid is determined using the selected scaling values. A substrate may be exposed using the determined substrate grid to correct exposure of the substrate.