Wafer Contamination Source Identification Using Light Scattering and SIMS
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Solution Overview
Problem
Existing methods for identifying contamination on semiconductor wafers provide limited information on the cause of defects, especially for non-organic contaminants, and lack sufficient chemical composition accuracy.
Innovation Solution
A method combining light scattering measurement with secondary ion mass spectrometry (SIMS) to identify surface defects and determine their chemical composition, allowing identification of the process step where foreign materials are introduced.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If light scattering measurement is used to inspect wafer surface defects, then the position and size of defects can be identified, but the chemical composition and origin of contamination cannot be determined
Solution Approach 1:
The patent combines light scattering measurement with secondary ion mass spectrometry (SIMS) to create an integrated inspection system. The light scattering measurement identifies defect positions and sizes, while SIMS provides detailed chemical composition analysis of the same defects, eliminating information loss by merging two complementary measurement techniques into a unified workflow
2Measurement precision
If SEM-EDX analysis is used to identify contamination chemistry, then the main element of impurity can be identified, but the origin and specific source of contamination remains unknown
Solution Approach 1:
The patent transitions from EDX (energy-dispersive X-ray spectroscopy) to SIMS (secondary ion mass spectrometry), changing the analytical parameter from elemental detection to molecular and isotopic detection. SIMS provides mass spectral information including isotopic ratios and molecular fragments that are characteristic of specific materials and processes, enabling identification of contamination sources that EDX cannot distinguish
3Ease of operation
If standard analytical methods are used for surface defect analysis, then optical and electronic properties can be characterized, but sufficient chemical composition accuracy for source identification cannot be achieved
Solution Approach 1:
The patent introduces SIMS as an intermediary analytical technique between the initial light scattering detection and the final contamination source identification. SIMS acts as a mediator that provides the missing chemical specificity, bridging the gap between easy-to-perform optical inspection and the need for high-precision chemical analysis to identify contamination sources
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
Accurately determines the chemical composition of surface defects, enabling the identification of the source of contamination and facilitating process adjustments to prevent future contamination.
Implementation Method 1
identifying the positions and sizes of surface defects on the at least one selected wafer of semiconductor material by means of light scattering measurement
Implementation Method 2
determining the chemical composition of at least a portion of the selected at least one surface defect by means of secondary ion mass spectrometry (SIMS)
Data Source
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AI summary
A method for identifying the cause of contamination in wafers of semiconductor material, comprising the following steps: (i) selecting at least one wafer of semiconductor material; (ii) identifying the positions and sizes of surface defects on the at least one selected wafer of semiconductor material by means of light scattering measurement; (iii) selecting at least one of the surface defects identified in step (ii) and determining the chemical composition of at least a portion of the selected at least one surface defect by means of secondary ion mass spectrometry; and (iv) identifying a process step in the used manufacturing process of the wafers of semiconductor material in which a material, an auxiliary substance, or an impurity comprising a foreign material with the determined chemical composition occurs.