Substrate Holder Cavity Flow for Negative Photoresist Stripping
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Solution Overview
Problem
Negative photoresists are difficult to remove from substrates due to their tendency to swell and partially dissolve over a long duration, especially in complex geometries like SnAg mushroom plating and high-pitch features, which complicates the removal process in semiconductor fabrication.
Innovation Solution
A method and apparatus for removing photoresist material using a substrate holder with a flow distributor that creates a cavity for a stripping solution to flow over the substrate, ensuring complete or substantial removal within a shorter time frame, typically less than 4 minutes, using DMSO- and/or TMAH-based solutions, and featuring a rotating substrate to enhance fluid dynamics and material removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional stripping methods are used for negative photoresist, then the photoresist can be removed, but the removal process takes a long duration and is inefficient
Solution Approach 1:
The patent employs hydraulic principles by using a flow distributor to deliver stripping solution under controlled flow rates (e.g., 20-40 LPM) through a cavity structure. The pressurized fluid flow dynamically interacts with the rotating substrate to enhance photoresist removal efficiency, reducing processing time from conventional extended durations to under 4 minutes while maintaining complete removal.
Solution Approach 2:
The substrate is rotated during the stripping process to create dynamic fluid-structure interaction. This rotation enhances the effectiveness of the stripping solution by continuously exposing fresh surfaces to the chemical agent and preventing localized saturation, thereby significantly improving removal speed and completeness compared to static conventional methods.
2Manufacturing precision
If negative photoresist is used for WLP processes, then good adhesion and vertical profiles are achieved, but the photoresist becomes difficult to remove
Solution Approach 1:
The flow distributor system delivers stripping solution at optimized flow rates and pressures through a cavity structure, ensuring thorough penetration and contact with the negative photoresist material. This hydraulic approach overcomes the inherent resistance of negative photoresist to removal while preserving the high-quality vertical profiles and adhesion properties achieved during fabrication.
Solution Approach 2:
Substrate rotation creates dynamic conditions that enhance the penetration and distribution of stripping solution across the photoresist surface. This mechanical motion ensures complete removal of negative photoresist from complex geometries including deep features and high-pitch structures, overcoming the removal difficulties while maintaining manufacturing precision.
3Productivity
If the cavity dimension is small (2-10 mm), then the stripping solution flows efficiently over the substrate, but the fluid dynamics are more challenging to control
Solution Approach 1:
The substrate rotation mechanism provides dynamic control over fluid-structure interaction within the compact cavity. By adjusting rotation speed, the system optimizes the flow patterns and shear forces acting on the photoresist, enabling efficient stripping solution circulation through the 2-10 mm cavity while maintaining controllable and repeatable process conditions.
Solution Approach 2:
The system controls multiple parameters including flow rate (20-40 LPM), cavity dimension (2-10 mm), and substrate rotation speed to optimize the fluid dynamics within the compact cavity. By carefully balancing these parameters, the invention achieves efficient stripping solution flow and complete photoresist removal without requiring overly complex control systems.
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 and apparatus facilitate faster and more efficient removal of negative photoresist material from substrates with complex features, improving processing time and effectiveness compared to conventional methods.
Implementation Method 1
negative photoresists are quite difficult to remove... the material removed is a negative photoresist material... flowing stripping solution from the one or more inlets, through the internal manifold, into the cavity over the face of the substrate... to thereby remove from the substrate at least some of the material for removal
Data Source
AI summary
The embodiments disclosed herein pertain to novel methods and apparatus for removing material from a substrate. In certain embodiments, the method and apparatus are used to remove negative photoresist, though the disclosed techniques may be implemented to remove a variety of materials. In practicing the disclosed embodiments, a stripping solution may be introduced from an inlet to an internal manifold, sometimes referred to as a cross flow manifold. The solution flows laterally through a relatively narrow cavity between the substrate and the base plate. Fluid exits the narrow cavity at an outlet, which is positioned on the other side of the substrate, opposite the inlet and internal manifold. The substrate spins while in contact with the stripping solution to achieve a more uniform flow over the face of the substrate. In some embodiments, the base plate includes protuberances which operate to increase the flow rate (and thereby increase the local Re) near the face of the substrate.