Electrorheological Fluid Particle Removal for Semiconductor Substrates
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Solution Overview
Problem
Conventional surface cleaning methods for semiconductor devices are inadequate in removing small residual particles without damaging sensitive structures or altering critical dimensions, as they often apply forces in all directions and can dissolve or damage the substrate materials.
Innovation Solution
The use of electrorheological (ER) fluids that change viscosity in response to an external electric field, allowing for minimal force particle removal from semiconductor substrates without damaging fragile structures, utilizing ER particles and a base liquid that are compatible with the substrate materials and stable over a wide temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional cleaning solutions (RCA clean, acoustic energy, high-pressure spraying) are used to remove particles, then particle removal capability is improved, but substrate structures are damaged or critical dimensions are altered
Solution Approach 1:
The patent applies electrorheological fluids that change their viscosity parameter in response to an external electric field. When the electric field is applied, the fluid transitions from a low-viscosity state to a high-viscosity state, enabling it to lift and remove particles. When the field is removed, the fluid returns to low viscosity for easy handling and rinsing. This dynamic parameter change allows effective particle removal without the need for high mechanical forces that would damage substrate structures.
Solution Approach 2:
The patent replaces conventional mechanical cleaning methods (acoustic energy, high-pressure spraying, mechanical scrubbing) with an electro-rheological-based cleaning mechanism. Instead of applying mechanical forces in all directions that can damage structures, the ER fluid uses electric field-induced viscosity changes to selectively lift particles through electrostatic forces, thereby substituting mechanical action with an electrical field-based mechanism that is more controllable and less damaging.
2Productivity
If high forces are applied to remove entrenched particles, then particle removal is improved, but substrate materials are damaged or dissolved
Solution Approach 1:
The electrorheological fluid's viscosity parameter is dynamically changed using an external electric field. In the low-viscosity state (no electric field), the fluid can be easily applied and does not exert excessive force on the substrate. When the electric field is applied, the viscosity increases dramatically, enabling the fluid to generate sufficient lifting force to remove entrenched particles. This controlled parameter change ensures that high forces are only applied when needed for particle removal, not during application or rinsing, thereby protecting substrate material integrity.
Solution Approach 2:
The cleaning system uses a dynamic ER fluid whose viscosity can be rapidly switched between low and high states in response to electric field application. This dynamic behavior allows the system to adapt the force applied to particles in real-time: low force during application to avoid substrate damage, high force during cleaning to remove particles, and low force during rinsing for easy removal. This dynamic control resolves the contradiction between needing high force for particle removal and maintaining substrate integrity.
3Object-affected harmful factors
If electrorheological fluids are used for particle removal, then substrate structure integrity is preserved, but fluid handling complexity increases
Solution Approach 1:
The patent replaces complex mechanical handling systems with a simpler electric field-based control mechanism. Instead of requiring complex mechanical devices to control fluid viscosity and application forces, the system uses electrical fields to trigger viscosity changes in the ER fluid. This substitution of mechanical control with electrical control simplifies the overall system architecture while maintaining the benefit of preserved substrate structure integrity.
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
Effectively removes residual particles with reduced shear force, preserving the integrity of substrate features and structures, while maintaining a low viscosity in the absence of an electric field for easy handling and application.
Implementation Method 1
electrorheological (ER) fluids that change viscosity in response to an external electric field
Data Source
AI summary
Methods and apparatus for cleaning a substrate (e.g., wafer) in the fabrication of semiconductor devices utilizing electrorheological (ER) and magnetorheological (MR) fluids to remove contaminant residual particles from a surface of the substrate are provided.