Substrate Drying Humidity Control to Prevent Dew Condensation
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Solution Overview
Problem
High humidity in processing containers during substrate drying can lead to dew condensation, causing watermark formation and pattern collapse on semiconductor wafers due to surface tension effects from droplets.
Innovation Solution
A liquid processing method that involves supplying a processing liquid to a substrate, followed by a low humidity gas to lower the container humidity, and initiating the drying process only when the humidity reaches a preset target value, using a substrate processing apparatus with a humidity measurement unit and controller to manage the drying timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If drying process is performed in high humidity environment, then drying speed is improved, but dew condensation occurs causing watermark formation and pattern collapse
Solution Approach 1:
The patent applies preliminary action by reducing the humidity inside the processing container before the drying process begins. The humidity control unit lowers the container humidity to a predetermined value or less before the drying liquid is supplied to the substrate, preventing dew condensation from occurring during subsequent drying operations.
Solution Approach 2:
The patent implements feedback control through the humidity control unit that continuously monitors and adjusts the humidity inside the processing container. By measuring the actual humidity levels and comparing them to target values, the system dynamically controls the drying environment to prevent dew condensation while maintaining optimal drying conditions.
2Device complexity
If humidity inside processing container is not controlled, then process simplicity is maintained, but substrate surface integrity deteriorates due to watermark and pattern collapse
Solution Approach 1:
The processing apparatus integrates multiple functions into a unified system. The humidity control unit combines gas supply, exhaust, and humidity measurement capabilities into a single integrated subsystem that manages container humidity automatically, maintaining substrate surface integrity without significantly increasing overall system complexity.
3Loss of time
If drying process starts immediately after liquid processing, then processing time is reduced, but dew condensation occurs on substrate surface
Solution Approach 1:
The system performs preliminary humidity reduction in the processing container immediately after liquid processing completes but before the drying process begins. This preliminary action prepares the container environment in advance, allowing the drying process to start promptly while ensuring dew condensation-free conditions are already established.
Solution Approach 2:
The humidity control unit operates continuously during the transition from liquid processing to drying. By maintaining continuous humidity control throughout the process sequence, the system ensures uninterrupted protection against dew condensation while minimizing idle time between processing stages.
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 prevents pattern collapse and watermark formation by ensuring the substrate is dried under controlled humidity conditions, maintaining the integrity of the processed wafer surface.
Implementation Method 1
a low humidity gas supplying process of supplying a low humidity gas for lowering a humidity inside the processing container, into the processing container during a time period when the processing liquid is supplied to the substrate
Implementation Method 2
drying the substrate is performed by supplying a highly volatile drying liquid such as, for example, isopropyl alcohol (IPA) to the rotating substrate to replace the liquid remaining on the surface of the substrate with the drying liquid
Implementation Method 3
when the humidity inside the processing container where the liquid processing is performed is high, a dew condensation may occur on the dried surface of the wafer
Data Source
AI summary
In drying a substrate disposed inside a processing container after performing a liquid processing on the substrate, a low humidity gas for lowering a humidity inside the processing container is supplied during a time period when a processing liquid is supplied to the center portion of the substrate, and the processing liquid supplied to the center portion of the substrate is stopped after a humidity measurement value obtained by measuring the humidity inside the processing container becomes equal to or less than a preset humidity target value.