Helium Ion Microscope for 3D Substrate Inspection
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Solution Overview
Problem
Current microelectronic substrate inspection technologies face limitations in detecting fine patterns with high precision due to optical diffraction, and electron beam inspection equipment can cause sample damage and contamination, while providing only 2D information.
Innovation Solution
The use of a helium ion microscope (HIM) for microelectronic substrate inspection, which includes a helium gas container, helium ion generator, wafer stage, secondary electron detector, and cooling device, allows for the measurement of step heights by irradiating helium ions and detecting secondary electrons, enabling 3D stereoscopic information capture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If optical inspection equipment is used to detect fine patterns, then the inspection process is simple and fast, but the detection capability is limited due to optical diffraction
Solution Approach 1:
The patent replaces the optical inspection system with a helium ion microscope system. Instead of using photons for imaging, the system uses helium ions to irradiate the substrate and detect secondary electrons, thereby substituting an optical system with a particle-based system that overcomes diffraction limits and achieves higher resolution for fine pattern inspection
2Measurement precision
If electron beam inspection equipment is used to achieve high resolution, then the spatial resolution reaches several nanometers, but the sample may be damaged or contaminated and only 2D information is obtained
Solution Approach 1:
The patent changes the fundamental parameter of the inspection beam from electrons to helium ions. Helium ions have a larger mass than electrons, which reduces charging effects on the sample. The system uses lower acceleration voltages (e.g., 30-100 kV) compared to electron microscopes, further reducing sample damage while maintaining high spatial resolution capabilities
3Measurement precision
If electron beam inspection equipment is used, then high spatial resolution is achieved, but only 2D planar information is obtained due to small depth of focus
Solution Approach 1:
The patent introduces the depth dimension to the inspection process by utilizing the large depth of focus inherent in helium ion microscopy. The system captures images at different focal depths and combines them to reconstruct 3D topographic information of the substrate surface, thereby transitioning from 2D planar imaging to 3D stereoscopic imaging while maintaining high spatial resolution
4Measurement precision
If a helium ion generator is used for high precision inspection, then 3D measurement capability is achieved, but the device complexity increases due to cooling requirements
Solution Approach 1:
The patent employs a liquid nitrogen cooling system with a dewar container to maintain the helium ion generator at cryogenic temperatures. The system uses gas-phase nitrogen circulation and phase change (liquid to gas) for cooling, leveraging pneumatic and thermodynamic principles to manage the thermal load of the ion generator while enabling precise 3D measurements
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 approach provides accurate 3D measurement of step heights with high precision and reduced risk of sample damage, offering improved detection capabilities compared to traditional methods.
Implementation Method 1
a helium ion generator which may be disposed in the gas container and is configured to convert the helium gas into helium ions
Implementation Method 2
a cooling device which is configured to cool, for example to continuously cool, the helium ion generator by vaporizing the liquid nitrogen received from the liquid nitrogen dewar into second gaseous nitrogen
Implementation Method 3
a secondary electron detector which is disposed adjacent and, in some embodiments above, the wafer stage, and is configured to detect electrons generated from the substrate
Data Source
AI summary
Microelectronic substrate inspection equipment includes a gas container which contains helium gas, a helium ion generator which is disposed in the gas container and converts the helium gas into helium ions and a wafer stage which is disposed under the gas container and on which a substrate to be inspected is placed. The equipment further includes a secondary electron detector which is disposed above the wafer stage and detects electrons generated from the substrate, a compressor which receives first gaseous nitrogen from a continuous nitrogen supply device and compresses the received first gaseous nitrogen into liquid nitrogen, a liquid nitrogen dewar which is connected to the compressor and stores the liquid nitrogen, and a cooling device that is coupled to the helium ion generator. The cooling device is disposed on the gas container, and cools the helium ion generator by vaporizing the liquid nitrogen received from the liquid nitrogen dewar into second gaseous nitrogen. Related methods are also disclosed.