Organic Solvent Purifier with Ion-Exchange Resin and PTFE Membrane
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Solution Overview
Problem
Current IPA purifiers in semiconductor manufacturing fail to provide high enough purity for wafer spray processes, leading to metal contamination and reduced semiconductor device performance due to limitations in ion-exchange capacity and residue issues with existing microporous filters.
Innovation Solution
A point-of-use purifier system utilizing a housing with ion-exchange resin and a filtration member comprising microporous membranes with a neutral surface and PTFE membranes, designed to remove metal species like chromium from isopropanol in a single pass, reducing non-volatile residue and improving solvent purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a standard surface-modified microporous membrane is used for IPA purification, then the filter can be cleaned with IPA and works for low and high temperature applications, but the ion-exchange capacity is very low and cannot adequately handle severe metal contamination
Solution Approach 1:
The patent combines microporous membrane filtration with ion-exchange resin in a single integrated filter assembly. The microporous membrane provides physical filtration while the ion-exchange resin captures metal ions through ion exchange reactions, creating a composite system that addresses both filtration and ion removal needs that neither component could achieve alone
Solution Approach 2:
The patent merges two separate purification functions (microporous filtration and ion-exchange) into one integrated filter assembly. The filter assembly contains both microporous membrane material and ion-exchange resin in close proximity, allowing the IPA to undergo both filtration and ion-exchange processes in a single pass through the device
2Reliability
If sulfonic acid functionality is used in ion-exchange media for metal removal, then high removal of metals is achieved, but the functionality breaks down and sheds over time causing non-volatile residue and sulfonic acid ions to deposit on wafers
Solution Approach 1:
The patent changes the chemical parameters of the ion-exchange material by selecting alternative functional groups (such as carboxylic acid or phenolic groups) that have different stability characteristics compared to sulfonic acid groups. These alternative groups maintain ion-exchange capability while resisting breakdown and shedding under the operating conditions of IPA purification
Solution Approach 2:
The patent employs a disposable filter assembly design where the entire filter unit, including the ion-exchange media, is replaced periodically rather than attempting to regenerate or maintain it indefinitely. This approach ensures that any potential degradation products are eliminated with each new filter installation, preventing residue buildup on wafers while maintaining high metal removal efficiency throughout the filter's service life
3Ease of operation
If IPA is transferred through stainless steel lines in the fab, then the solvent can be delivered to tools, but the IPA picks up iron, nickel and other trace metals from the stainless steel which are then deposited on wafers
Solution Approach 1:
The patent extracts and removes trace metals from the IPA solvent using the ion-exchange resin component of the filter assembly. The ion-exchange resin selectively binds metal ions (such as iron and nickel) from the IPA stream, extracting them out of the solvent before it reaches the wafer processing tools, thereby preventing contamination while maintaining solvent delivery capability
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
The system achieves greater than 85% chromium removal from isopropanol solutions in a single pass, enhancing semiconductor device performance and process yield by providing higher purity solvents and minimizing metal contamination.
Implementation Method 1
A volume of ion-exchange resin is disposed within the housing downstream of the fluid inlet. The ion-exchange resin is adapted to remove metal species from the organic solvent.
Implementation Method 2
A pleated filtration member is disposed concentrically around the longitudinal axis within the cylindrical housing and downstream of the volume of ion-exchange resin. The pleated filtration member comprises at least one microporous membrane having a substantially neutral surface and adapted to remove chromium from the organic solvent.
Implementation Method 3
The filtration member comprises at least one microporous membrane having a substantially neutral surface and a microporous PTFE membrane downstream of the at least one microporous membrane.
Data Source
AI summary
A purifier for removing metal, such as chromium, from an organic solvent is disclosed. The purifier comprises a housing having a fluid inlet and a fluid outlet in fluid communication with the fluid inlet; a volume of ion-exchange resin disposed within the housing downstream of the fluid inlet; and a filtration member downstream of the volume of ion-exchange resin, the filtration member comprising at least one microporous membrane having a substantially neutral surface and a microporous polytetrafluoroethylene membrane downstream of the at least one microporous membrane. A method for removing metal, including chromium, from an organic solvent using a purifier of the invention is also disclosed.