Electroless Deposition for Metal Contamination Detection
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Solution Overview
Problem
Current metrology tools are inadequate for detecting metal contamination, organic residue, and incomplete via etch on patterned wafers, particularly as they fail to distinguish surface metal contamination from metal beneath the surface and often miss residues at the bottom of vias or trenches.
Innovation Solution
Electroless deposition is used as a metrology tool to selectively deposit a metallic material on contamination sites and via features, amplifying their visibility under critical dimension scanning electron microscopy (CD-SEM) for detection, while preventing deposition in areas with blockages like organic residues or incomplete etches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If TXRF is used to detect metal contamination, then signal information from metal is obtained, but precise information on the source of the signal is not provided
Solution Approach 1:
The patent uses electroless deposition as an intermediary step between contamination presence and detection. The deposition process selectively deposits metal only where contamination exists, creating a visible marker that preserves the location information while allowing detection by standard microscopy tools.
Solution Approach 2:
The electroless deposition process creates visible metal deposits that change the appearance of contaminated areas. This visual change allows contamination locations to be distinguished from clean areas using standard optical or electron microscopy, thereby preserving spatial information that would otherwise be lost.
2Illumination intensity
If top-down SEM is used to examine wafer, then surface structure is visible, but small metal contamination and residues at bottom of via are not detectable
Solution Approach 1:
The electroless deposition is performed as a preliminary action before final inspection. By depositing metal selectively on contaminated areas beforehand, the inspection process becomes much more sensitive to small contaminants, as they now have enhanced contrast and visibility in the SEM images.
Solution Approach 2:
The patent changes the physical state and distribution of metal contaminants by converting them into larger, more visible deposited metal structures. This parameter change from atomic/molecular scale contamination to micrometer-scale deposits dramatically improves detection sensitivity while maintaining compatibility with top-down SEM.
3Measurement precision
If electroless deposition is used to highlight contamination, then contamination locations become visible under CD-SEM, but additional process steps are required
Solution Approach 1:
The electroless deposition process serves multiple functions: it acts as both a contamination highlighting mechanism and a potential seed layer formation step in the dual-damascene process. This multi-functionality reduces the need for separate dedicated metrology steps, thereby offsetting the added complexity with process integration benefits.
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 method effectively highlights and detects metal contamination and incomplete via etches, enabling precise identification of issues that would otherwise be undetectable, thereby improving yield and reliability in semiconductor manufacturing.
Implementation Method 1
applying an electroless deposition solution to the substrate, the applied electroless deposition solution being configured for selectively depositing a metallic material over the exposed metallic feature and on metallic contaminants on exposed surfaces of the substrate
Implementation Method 2
the metallic contaminants define nucleation sites for the selective deposition of the metallic material, wherein the selective deposition of the metallic material on the metallic contaminants provides for an amplification in size of the metallic contaminants so as to become detectable by the inspection operation
Data Source
AI summary
A method for detecting contamination on a patterned substrate includes: performing a via etch operation on a substrate, wherein the via etch operation is configured to define a via feature on the substrate and expose an etch-stop layer at a bottom of the via feature; performing an etch-stop removal operation on the substrate, wherein the etch-stop removal operation is configured for removing the etch-stop layer at the bottom of the via feature to expose a metallic feature underlying the etch-stop layer; applying an electroless deposition solution to the substrate, the applied electroless deposition solution configured for selectively depositing a metallic material over the exposed metallic feature and on metallic contaminants on exposed surfaces of the substrate, the metallic contaminants being generated from the metallic feature during the etch-stop removal operation; performing an inspection operation on the substrate to identify the metallic contaminants that have been deposited with the metallic material.