SEM Imaging With Ice-Layer Cleaning for Surface Contamination Removal
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Solution Overview
Problem
Scanning electron microscopes face challenges in achieving a clean sample surface for imaging, as existing methods are inefficient in removing contamination and can lead to prolonged cleaning times and residual contamination.
Innovation Solution
A method involving the formation of a thin ice layer on the sample surface by adding water and cooling it below -10°C, followed by an electron cleaning scan to remove contamination, allowing for efficient cleaning within a specific energy and dwell time range, and subsequent imaging with higher energy electrons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional cleaning methods are used, then cleaning effectiveness is limited, but cleaning time is prolonged and residual contamination remains
Solution Approach 1:
The patent utilizes phase transitions of water (liquid to solid ice) to create an ice layer on the sample surface. This ice layer serves as a temporary medium that binds contamination, which is then removed through electron beam irradiation. The phase transition enables effective contamination removal without prolonged cleaning time.
Solution Approach 2:
The ice layer acts as an intermediary substance between the sample surface and the electron beam. It binds hydrocarbon contamination and facilitates its removal through electron irradiation, providing a more effective cleaning mechanism than direct electron beam cleaning without ice.
2Reliability
If a thick ice layer is used for cleaning, then contamination binding is improved, but cleaning time increases and measurement time is lost
Solution Approach 1:
The patent applies partial action by using a thin ice layer (1-10 nm) rather than a thick ice layer. This thin layer is sufficient to bind contamination effectively while being removed quickly by electron beam irradiation, thus maintaining high productivity and minimizing measurement time loss.
Solution Approach 2:
The patent optimizes the ice layer thickness parameter to a specific range (1-10 nm). This parameter change ensures that the ice layer is thin enough for rapid removal by electron beam but thick enough to effectively bind contamination, resolving the contradiction between cleaning effectiveness and measurement time.
3Object-generated harmful factors
If sample cooling is applied, then carbon migration is inhibited, but system complexity increases
Solution Approach 1:
The patent replaces complex mechanical cooling systems with a simpler approach: introducing water vapor into the vacuum chamber and utilizing the electron beam's own energy to freeze the water on the sample surface. This substitution reduces system complexity while achieving the same effect of inhibiting carbon migration.
Solution Approach 2:
The electron beam serves a dual function: it cleans the contamination and simultaneously provides the energy needed to freeze water vapor into an ice layer on the sample. This self-service approach eliminates the need for separate cooling systems, reducing device complexity.
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 binds and removes contamination, inhibiting carbon migration and achieving a clean surface with minimal measurement time, providing better cleaning results than traditional methods.
Implementation Method 1
adding water to the vacuum chamber such that the water is precipitated as an H2O layer on the sample in the region of the imaging field
Implementation Method 2
cooling the sample in the vacuum chamber to a temperature below −10° C.
Implementation Method 3
performing a sample cleaning operation with the aid of at least one electron cleaning scan within a cleaning field within which the imaging field lies, with removal of the H2O layer during the cleaning scan
Implementation Method 4
Sample cooling has the desirable secondary effect of inhibiting or completely preventing migration of carbon contamination
Data Source
AI summary
In the context of imaging with a scanning electron microscope, a sample to be imaged is first positioned in a vacuum chamber of the scanning electron microscope (SEM), such that an imaging field of the SEM arrives at a section of the sample to be imaged. Water is added to the vacuum chamber, such that the water is precipitated as an H2O layer on the sample in the region of the imaging field. The sample in the vacuum chamber is then cooled to a temperature below −10° C. Then a sample cleaning operation is performed with the aid of at least one electron cleaning scan within a cleaning field within which the imaging field lies. The H2O layer is removed during the cleaning scan. Then the imaging field is imaged with the aid of an electron imaging scan after the at least one cleaning scan has ended. The result is an imaging method in which a sample surface of the sample to be imaged in the imaging of an imaging field is reliably clean.