Buried Defect Detection in Microscopic Metal Features
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Solution Overview
Problem
Detecting voids and buried defects in microscopic metal features, particularly those less than a micron in width, is challenging due to their hidden nature, and existing techniques like electrical probing and traditional electron beam imaging are inadequate for early detection in semiconductor manufacturing.
Innovation Solution
An electron beam imaging apparatus is configured to impinge charged particles with high landing energy, filter out secondary electrons, and detect backscattered electrons to create images for comparison with reference features, enabling the detection and classification of buried defects in microscopic metal features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional electron beam imaging is used, then surface features can be visualized, but buried defects in microscopic metal features cannot be detected
Solution Approach 1:
The patent transitions from surface-only imaging to depth-resolved imaging by varying the energy of incident electrons. By adjusting electron beam energy, the imaging system penetrates to different depths within the metal feature, enabling detection of buried defects at various subsurface levels that are invisible to conventional surface imaging methods
Solution Approach 2:
The patent changes the energy parameter of the incident electron beam to control penetration depth. By systematically varying electron energy, the system can probe different depths within the metal feature, transforming a surface-limited technique into a depth-resolved detection method capable of identifying buried defects
2Reliability
If electrical probing is used for defect detection, then conductive defects can be identified, but detection must wait until after metal layer formation, reducing early detection capability
Solution Approach 1:
The patent performs imaging and defect detection before metal layer formation is complete, using low-energy electron beams that can detect defects in exposed metal features. This preliminary detection allows identification of issues while the structure is still accessible, enabling early intervention before subsequent processing steps obscure the defects
3Length of stationary object
If high energy electron beams are used to reach buried defects, then deeper detection is possible, but secondary electron noise increases
Solution Approach 1:
The patent extracts or filters out secondary electrons from the detected signal using energy discrimination techniques. By separating secondary electrons (which have low energy and cause noise) from backscattered electrons (which carry useful depth information), the system eliminates the harmful noise while preserving the useful signal from deeper regions
Solution Approach 2:
The patent introduces an energy filter as an intermediary component between the sample and detector. This filter acts as a mediator that selectively transmits electrons based on their energy, allowing backscattered electrons from deep regions to pass through while blocking low-energy secondary electrons that would otherwise contaminate the signal
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 allows for the early detection of yield-reducing defects in metal plugs and lines during semiconductor manufacturing, enabling manufacturers to identify issues before the end of the fabrication process, thereby improving production efficiency and reducing defects.
Implementation Method 1
An imaging apparatus is configured to impinge charged particles with a landing energy such that the charged particles, on average, reach a depth within the target microscopic metal feature
Implementation Method 2
The imaging apparatus is then operated to collect the backscattered electrons emitted from the target microscopic metal feature due to impingement of the charged particles
Data Source
AI summary
One embodiment relates to a method of detecting a buried defect in a target microscopic metal feature. An imaging apparatus is configured to impinge charged particles with a landing energy such that the charged particles, on average, reach a depth within the target microscopic metal feature. In addition, the imaging apparatus is configured to filter out secondary electrons and detect backscattered electrons. The imaging apparatus is then operated to collect the backscattered electrons emitted from the target microscopic metal feature due to impingement of the charged particles. A backscattered electron (BSE) image of the target microscopic metal feature is compared with the BSE image of a reference microscopic metal feature to detect and classify the buried defect. Other embodiments, aspects and features are also disclosed.