Cryopump Drain and Vent Pressure Control
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Solution Overview
Problem
Current cryopump regeneration methods are inefficient in rapidly melting and removing large quantities of cryodeposits, leading to prolonged recovery times and pressure spikes due to uncontrolled evaporation when cryogen melts onto the vacuum housing.
Innovation Solution
The method involves containing melted cryogen within the warm cryopanel and using a purge gas that condenses on the cryodeposit, such as argon, to control pressure and facilitate rapid melting and venting, preventing liquid from contacting the vacuum housing and thus managing heat transfer and evaporation rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the cryopump is warmed up to melt cryodeposits for regeneration, then the cryodeposits are removed, but pressure spikes occur due to uncontrolled evaporation
Solution Approach 1:
A condenser is introduced as an intermediary component between the melt zone and the vacuum environment. The condenser captures and condenses evaporating cryogen vapors, preventing them from creating pressure spikes while allowing controlled removal of melted deposits through the drain hole.
Solution Approach 2:
The system uses pressure sensing feedback to control the heating process. When pressure approaches a predetermined threshold during warming, the heating element automatically reduces or stops heating, preventing uncontrolled pressure buildup while maintaining efficient regeneration when pressure is acceptable.
2Quantity of substance
If the cryopump uses a large capacity to store 3000 SL of Ar, then the pump can handle sputtering loads, but the regeneration time is prolonged due to the large amount of cryogen to remove
Solution Approach 1:
The system extracts heat efficiently from the large volume of cryogen using a heating element positioned in direct contact with the melt zone. By concentrating heating power where the cryodeposits are thickest and most numerous, the system accelerates melting of large quantities of Ar without requiring proportional increases in overall system size.
Solution Approach 2:
The condenser acts as a mediator that handles the large volume of evaporating cryogen efficiently. It condenses vapors back to liquid form, allowing continuous processing of large cryogen quantities without pressure buildup, thereby enabling faster regeneration of pumps with large storage capacities.
3Volume of moving object
If the cryopump is oriented with inlet facing up or sideways, then it is more compact for mounting, but melted cryogen flows in unpredictable directions
Solution Approach 1:
The condenser serves as a mediator that captures cryogen vapors regardless of their direction of travel. This allows the pump to be mounted in compact orientations (inlet up or sideways) while the condenser ensures that evaporating cryogen is consistently captured and condensed, preventing drainage issues from unpredictable flow directions.
Solution Approach 2:
The system addresses the drainage problem by moving from relying on gravitational flow in a specific direction to using vapor-phase capture in three-dimensional space. The condenser captures cryogen vapors from all directions, making the system insensitive to pump orientation while maintaining compact mounting options.
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 significantly reduces regeneration time by controlling the evaporation rate and pressure, allowing for faster cryopump recovery and preventing pressure spikes, thereby enhancing throughput in semiconductor manufacturing.
Implementation Method 1
using a purge gas that condenses on the cryodeposit, such as argon
Implementation Method 2
the evaporation rate and pressure, allowing for faster cryopump recovery
Data Source
AI summary
A means of rapidly melting a large quantity of type II cryogen in a cryopump that is configured to contain the liquid in the warm cryopanel with the inlet to the cryopump facing up or sideways, and venting the liquid and gas in a controlled way. Rapid melting is preferably accomplished by flowing a purge gas that will condense on the cryodeposit. By not allowing the liquid to drain onto the vacuum housing the evaporation rate is limited and the maximum pressure in the cryopump can be controlled by the purge gas flow rate.