Diffuser Membrane Venting for Vacuum Chamber Particle Control
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Solution Overview
Problem
Current diffuser membranes in vacuum chambers experience significant variations in gas velocity and mass flow during vent-up, leading to particle re-distribution onto sensitive substrates, which complicates achieving both rapid venting and low particle contamination.
Innovation Solution
Tighter, more restrictive diffuser membranes with smaller pore sizes and higher permeability resistance are used to maintain laminar flow and minimize gas mass flow variation during vent-up, allowing higher inlet pressures and reducing stress on the membrane, thus controlling gas velocity and mass flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a standard screen or open porous material like a frit is used to increase gas flowrate for rapid venting, then vent-up time is reduced, but gas velocity at the chamber entrance becomes high and non-uniform, resulting in disturbance of unwanted particles
Solution Approach 1:
The patent employs a porous diffuser membrane with specifically controlled pore size and distribution to achieve uniform gas flow across the chamber entrance. The porous structure allows the membrane to resist gas flow sufficiently to maintain low velocities while still permitting rapid venting, thereby preventing particle disturbance while achieving fast pressure equalization.
Solution Approach 2:
The patent changes the physical parameters of the diffuser membrane, specifically using a porous membrane with controlled pore size, thickness, and material properties to optimize the balance between gas flow resistance and uniformity. By adjusting these parameters, the system achieves both rapid venting and particle-free flow conditions.
2Object-affected harmful factors
If a tighter, more restrictive diffuser membrane with smaller pore sizes is used to maintain laminar flow and minimize gas mass flow variation, then particle re-distribution is reduced, but gas flow resistance increases
Solution Approach 1:
The patent uses a porous diffuser membrane with optimized pore structure that provides sufficient gas flow resistance to maintain laminar flow and prevent particle re-distribution, while the controlled porosity ensures the resistance is not excessive. The porous material properties are specifically selected to balance particle control with acceptable venting performance.
3Object-affected harmful factors
If membrane diffusers with ultra fine filtration membranes are used to achieve low downstream gas velocities, then particle disturbance is minimized, but the diffusers provide little resistance to gas flow into the chamber
Solution Approach 1:
The patent employs a porous diffuser membrane that provides both ultra-fine filtration capability and sufficient gas flow resistance. The porous structure with controlled pore size and distribution allows the membrane to filter particles effectively while maintaining the pressure differential needed for adequate gas flow control during venting operations.
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 enables faster vent-up times with reduced gas mass flow variability, minimizing particle re-distribution and maintaining substrate cleanliness, even at higher pressures, by establishing a consistent differential pressure across the diffuser membrane.
Implementation Method 1
maintain laminar flow and minimize gas mass flow variation during vent-up
Implementation Method 2
Gas diffusers with ultra fine filtration membranes solved these issues
Implementation Method 3
Tighter, more restrictive diffuser membranes with smaller pore sizes and higher permeability resistance
Implementation Method 4
diffuser membranes with ultra fine filtration membranes
Data Source
AI summary
An apparatus and method for maintaining low gas velocity variation across a diffuser membrane during the vent-up of a vacuum chamber is disclosed. The diffuser membrane permeability and the pressure conditions across the membrane are chosen to minimize variation in gas flow velocity through the membrane during the vent-up cycle. This reduces re-distribution of particles from a vacuum chamber onto sensitive substrates in the vacuum chamber during vent-up from sub-atmospheric pressure to atmospheric pressure.