Edge Bead Removal Using Strong Base and Vacuum
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Solution Overview
Problem
Existing methods for removing edge beads during photolithographic processing are unsatisfactory, as they often transfer the edge bead from one location to another rather than effectively removing it, particularly when using organic solvents.
Innovation Solution
A strongly basic solution with a pH of at least 14, comprising potassium hydroxide or tetramethyl ammonium hydroxide, is applied to the edge bead while simultaneously using a vacuum to dissolve and remove the photoresist coating, ensuring effective decomposition and removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If organic solvent is used to dissolve photoresist at the edge of the substrate, then the edge bead is dissolved, but the photoresist comes out of solution as the solvent evaporates and the edge bead is transferred to another location
Solution Approach 1:
The patent changes the chemical parameter of the solvent from organic solvent to aqueous base solution with pH of at least 14. This fundamental parameter change transforms the dissolution mechanism, allowing complete removal of photoresist without transfer, as the basic solution chemically decomposes the photoresist rather than merely dissolving it temporarily.
Solution Approach 2:
The patent replaces the physical dissolution mechanism of organic solvents with a chemical decomposition mechanism using strong base solutions. This substitution eliminates the evaporation-induced transfer problem by using a different chemical approach that permanently removes the photoresist through decomposition rather than temporary dissolution.
2Manufacturing precision
If strong base solution is applied to dissolve photoresist, then the edge bead is effectively removed, but the process requires precise control of base solution application and removal
Solution Approach 1:
The patent introduces a vacuum system as an intermediary mechanism to control the removal of the base solution. The vacuum applied at the periphery of the substrate creates a controlled flow path that draws the base solution and dissolved photoresist away from the center, enabling precise control without complex manual operations.
Solution Approach 2:
The patent utilizes vacuum pressure differential to control the flow and removal of the base solution. By applying vacuum at the periphery, a pressure gradient is created that automatically directs the solution flow, simplifying the control mechanism while ensuring complete removal of the edge bead.
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 method achieves a clean edge with a uniformly distributed coating by chemically decomposing the photoresist, preventing re-deposition and ensuring a satisfactory edge profile.
Implementation Method 1
utilization of strongly basic solutions to remove edge beads during photolithographic processing
Implementation Method 2
A suction is applied to the peripheral region of the substrate to remove the basic solution and the dissolved coating material
Data Source
AI summary
Some embodiments include methods for removing an edge bead after a photoresist application. Basic solution may be applied to the edge bead and removed with a vacuum, with the basic solution having a pH of at least about 14. Some embodiments include methods of profiling coatings along peripheral regions of substrates. A nozzle may be positioned above a peripheral region and oriented to direct a basic solution downwardly toward the peripheral region. A suction port may be positioned laterally outward of the peripheral region. Basic solution may be ejected from the nozzle toward the peripheral region, with the basic solution having a pH of at least about 14 and dissolving coating along the peripheral region. A vacuum may be provided within the suction port to pull the basic solution and the dissolved coating from the peripheral region.