Energy Filtering SEM for Sub-Surface Defect Detection
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Solution Overview
Problem
Traditional scanning electron microscopes are unable to image or detect defects positioned below a protective layer due to the short mean free path of electrons, which limits their ability to inspect sub-surface layers in integrated circuits.
Innovation Solution
A method and system that utilizes energy filtering in a scanning electron microscope to selectively reject low-energy electrons, allowing high-energy electrons to convey information from beneath the protective layer, enabling the detection of hidden defects by defining an energy band responsive to the characteristics of the opaque and scanning electron microscope, and using a spectrometer to generate images from electrons within this energy band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective layer is deposited over copper layers, then oxidation protection and manufacturing process reliability are improved, but the ability to detect defects below the protective layer using traditional SEM deteriorates
Solution Approach 1:
The patent changes the energy parameter of electrons by applying a retarding potential field that filters electrons based on their energy levels. Low-energy electrons (from the protective layer surface) are rejected, while high-energy electrons (from deeper sub-surface layers) are transmitted to the detector, enabling defect detection beneath the protective layer
Solution Approach 2:
The patent introduces an energy filtering mechanism as an intermediary between the electron beam and the detector. This filtering system selectively transmits electrons based on their energy, acting as a mediator that allows information from deep layers to reach the detector while blocking surface-level interference
2Measurement precision
If traditional SEM is used for high resolution surface measurement, then surface feature measurement precision is improved, but the depth of information volume and ability to image sub-surface layers deteriorates
Solution Approach 1:
The patent modifies the energy parameter of the electron beam and applies energy filtering to change which electrons reach the detector. By selecting for high-energy electrons that originate from deeper regions, the system extends the effective depth of the information volume while preserving measurement precision through controlled energy selection
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 the imaging of sub-surface layers and detection of hidden defects by filtering out low-energy electrons, effectively overcoming the limitations of traditional SEMs in inspecting defects beneath protective layers, thereby improving defect detection capabilities in integrated circuit manufacturing.
Implementation Method 1
A method and system that utilizes energy filtering in a scanning electron microscope to selectively reject low-energy electrons, allowing high-energy electrons to convey information from beneath the protective layer
Implementation Method 2
The electron beam spot interacts with the surface and with a certain volume that is positioned near to the surface
Data Source
AI summary
A method for detecting hidden defects and patterns, the method includes: receiving an object that comprises an opaque layer positioned above an intermediate layer; defining an energy band in response to at least one characteristic of the opaque layer and at least one characteristic of a scanning electron microscope; illuminating the object with a primary electron beam; and generating images from electrons that arrive to a spectrometer having an energy within the energy band. A scanning electron microscope that includes a stage for supporting an object that comprises an opaque layer positioned above an intermediate layer; a controller, adapted to receive or define an energy band in response to at least one characteristic of the opaque layer and at least one characteristic of a scanning electron microscope; illumination optics adapted to illuminate the object with a primary electron beam; an electron spectrometer, controlled by the controller such as to selectively reject electrons in response to the defined energy band; and a processor, coupled to the spectrometer, adapted to generate images from detection signals provided by the spectrometer.