Gas Venting Control for Particle Contamination in Vacuum Systems
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Solution Overview
Problem
Current methods for transitioning a sample from a vacuum to atmospheric environment in charged particle beam imaging systems often result in uncontrollable particle contamination due to rapid gas venting, which deforms or lifts particles off the sample surface, and are irreproducible due to mechanical valve adjustments.
Innovation Solution
A method involving a gas venting process with a first gas flow rate increasing at a differential incremental rate until a saturation pressure is reached, followed by a second gas flow rate equal to or higher than the first, ensuring controlled pressure transitions without particle contamination, utilizing a gas supply assembly with a proportional control valve and pressure gauge for precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If rapid gas venting is used to transition from vacuum to atmospheric environment, then the pressure transition speed is improved, but particle contamination on the sample surface increases due to deformation and lifting of particles
Solution Approach 1:
The gas venting process is divided into multiple stages with different flow rates. The first stage uses a lower flow rate to prevent particle contamination, while the second stage uses a higher flow rate to complete the pressure transition efficiently. This segmentation of the venting process resolves the contradiction between speed and particle contamination control.
Solution Approach 2:
The gas flow rate is dynamically adjusted during the venting process rather than maintaining a constant rate. The system transitions from a first flow rate to a second flow rate based on the pressure level reached, allowing optimal control at different stages of the pressure transition to prevent particle contamination while maintaining efficiency.
2Device complexity
If mechanical valve adjustments are used to control gas flow rate, then the device complexity is reduced, but the reproducibility of the gas venting process deteriorates
Solution Approach 1:
The system incorporates pressure detection and control mechanisms that provide feedback to regulate the gas flow rate. This feedback control ensures that the gas venting process follows a predetermined profile with specific flow rates at different pressure stages, improving reproducibility while maintaining acceptable device complexity through automated control.
Solution Approach 2:
The patent replaces manual mechanical valve adjustments with an automated control system that uses pressure sensors and electronic control to regulate gas flow. This substitution eliminates the irreproducible nature of manual adjustments while maintaining reasonable device complexity through integrated sensor and controller components.
3Productivity
If a single high gas flow rate is used throughout the venting process, then the productivity is improved, but particle contamination increases due to strong gas stream effects on the sample surface
Solution Approach 1:
The venting process is segmented into two distinct phases: an initial phase with lower gas flow rate to protect the sample from particle contamination, and a final phase with higher gas flow rate to complete the pressure transition efficiently. This segmentation allows the system to achieve both productivity and particle protection.
Solution Approach 2:
The system performs preliminary gas venting at a controlled lower flow rate before increasing to the higher flow rate. This preliminary action prepares the environment by gradually introducing gas and establishing stable pressure conditions before the higher flow rate is applied, preventing particle contamination while maintaining overall process efficiency.
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 a reproducible and efficient method to control particle contamination, ensuring consistent results by maintaining stable gas flow rates and pressures, suitable for advanced semiconductor pattern fabrication.
Implementation Method 1
a proportional control valve for controlling a flow rate of the gas being vented into the closed space
Implementation Method 2
a pressure gauge for measuring a pressure inside the closed space
Implementation Method 3
the flow rate of the gas increases at a substantially differential incremental rate for a certain period of time before the saturation pressure is reached
Data Source
AI summary
A method for venting a gas into a closed space is disclosed. At the beginning of the venting process the flow rate of the venting gas starts from zero and then increases at a substantially differential incremental rate for at least a certain period of time. When a predefined saturation pressure inside the closed space is reached, the flow rate of the venting gas is maintained or increased to speed up the venting process.