Substrate Drying via Gas-Induced Dry Region and Percolation Inhibitor
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Solution Overview
Problem
In photolithography processes, the high surface tension of cleaning liquids causes resist pattern collapse and changes in Critical Dimension (CD) due to capillary phenomena, and low-surface-tension liquids with surfactants can swell the resist, further altering the patterns.
Innovation Solution
A substrate processing method involving a low-surface-tension replacing liquid with a percolation inhibitor is used to replace the cleaning liquid, combined with a gas supply to form a dry region on the substrate, preventing liquid from percolating into resist patterns and minimizing pattern collapse and CD changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pure water is used as a cleaning liquid, then the cleaning effect is achieved, but the resist pattern collapses due to high surface tension and capillary phenomenon
Solution Approach 1:
The patent changes the surface tension parameter of the cleaning liquid by adding surfactants, reducing it from high (pure water) to low (with surfactant). This parameter change prevents capillary phenomenon and pattern collapse while maintaining cleaning effectiveness.
Solution Approach 2:
The cleaning liquid is formulated as a composite material containing multiple components: water, surfactants (for low surface tension), and percolation inhibitors. This composite structure achieves both low surface tension for pattern protection and prevents liquid penetration into resist walls.
2Productivity
If a gas is supplied to the central region of a rotating substrate to form a dry region, then the substrate can be dried by enlarging the hole, but this method cannot suppress pattern collapse and CD change caused by liquid percolation
Solution Approach 1:
The patent applies preliminary action by using the gas flow to create a dry region in the central area before the liquid replacement and drying processes complete. This preliminary drying prevents liquid from remaining in the central region, thereby preventing pattern collapse and CD changes that would occur during subsequent drying stages.
Solution Approach 2:
The gas supply creates a localized dry region with different properties from the surrounding wet areas. This local quality change (dry vs. wet) allows selective drying of the central region first, preventing liquid-related damage to patterns in that critical area.
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 suppresses resist pattern collapse and maintains pattern integrity by preventing liquid percolation and ensuring uniform drying, thereby preserving the line width and enhancing semiconductor product throughput.
Implementation Method 1
supplying a gas to a central region of a rotating substrate, and the substrate is dried by enlarging the hole
Implementation Method 2
the cleaning liquid on the surface of the wafer is removed by rotating the wafer
Implementation Method 3
a liquid relatively low in surface tension (referred to as a 'low-surface-tension liquid') containing a surfactant is supplied to a wafer
Implementation Method 4
This may occur due to the capillary phenomenon generated in removing a cleaning liquid between the resist patterns
Data Source
AI summary
There is provided a substrate processing method including: supplying a developing liquid to a surface of an exposed substrate to form a resist pattern; supplying a cleaning liquid to the surface of the substrate to remove a residue generated in the developing step from the substrate; supplying a replacing liquid to the surface of the substrate to replace the cleaning liquid existing on the substrate with the replacing liquid, the replacing liquid having a surface tension of 50 mN/m or less and containing a percolation inhibitor for restraining the replacing liquid from percolating into a resist wall portion constituting the resist pattern; and forming a dry region by supplying a gas to a central portion of the substrate while rotating the substrate so as to dry the surface of the substrate by expanding the dry region to a peripheral edge portion of the substrate with a centrifugal force.