Micro-Fast Discharge Polishing for Surface Flatness
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Solution Overview
Problem
Current surface polishing methods in the semiconductor industry, such as chemical mechanical planarization (CMP), are limited in utility and generate new surface errors, while other methods like mechanical polishing and ion beam bombardment are time-consuming and not suitable for high-throughput production environments, necessitating an improved polishing technique that provides high accuracy and throughput.
Innovation Solution
A method utilizing a micro-fast discharge system where a needle-type electrode with a sharp tip generates localized electrical discharges in a gas chamber, controlled by a discharge circuit to produce short pulses, allowing for precise polishing of surface undulations with nanosecond pulse duration, capable of handling both flat and curved surfaces with high accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If chemical mechanical planarization (CMP) is used for surface polishing, then surface flatness can be improved, but new surface errors are generated and the method is limited to micrometer-level precision
Solution Approach 1:
The patent replaces the mechanical and chemical processes of CMP with an electrical discharge system. A needle electrode generates localized electrical discharges in a dielectric fluid, creating micro-plasma bursts that remove material through electro-erosion rather than mechanical abrasion or chemical reaction, thereby avoiding the generation of new surface errors associated with CMP
Solution Approach 2:
The patent applies polishing energy locally rather than globally. The needle electrode concentrates electrical discharge energy at specific surface locations where peaks or undulations exist, allowing selective removal of high spots without affecting the entire wafer surface uniformly, thus preventing the generation of global bow and other systematic surface errors
2Manufacturing precision
If mechanical polishing or ion beam bombardment methods are used, then surface precision can be improved, but the process becomes time-consuming and unsuitable for high-throughput production
Solution Approach 1:
The patent employs periodic electrical discharges at high frequency to achieve rapid material removal. The pulsed nature of the electrical discharge allows for continuous processing without the time-consuming sequential operations required by mechanical polishing or ion beam methods, enabling high-throughput production while maintaining nanometer-level precision
Solution Approach 2:
The patent changes the fundamental parameter of material removal from mechanical force or ion bombardment to electrical discharge energy. By controlling voltage, current, and pulse duration of the electrical discharge, the process achieves both high precision and high speed, overcoming the throughput limitation of conventional methods
3Manufacturing precision
If global polishing techniques like CMP are applied to entire wafers, then overall surface flatness is improved, but new systematic errors such as global bow are generated
Solution Approach 1:
The patent implements localized polishing by positioning a needle electrode to target specific surface peaks and undulations. Rather than applying uniform polishing pressure across the entire wafer as in CMP, the electrical discharge is concentrated at discrete locations where material removal is needed, eliminating the generation of global bow while achieving the required overall flatness
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 approach enables high-accuracy surface polishing within nanometer-scale precision, localized both temporally and spatially, with the ability to handle a wide range of materials, and is scalable for large-scale production, overcoming the limitations of existing methods by providing precise control over surface flatness and roughness.
Implementation Method 1
triggering an electrical breakdown of the discharging medium whereby the electrical breakdown results in a discharging pulse that polishes the surface
Implementation Method 2
utilizing a micro-fast discharge system where a needle-type electrode with a sharp tip generates localized electrical discharges in a gas chamber, controlled by a discharge circuit to produce short pulses
Data Source
AI summary
A method of polishing a surface of an object disposed within a gas chamber is provided. The method includes filling the gas chamber with a discharging medium to a predefined pressure, applying a voltage between an electrode and the surface, calibrating a height of the electrode relative to the surface so as to establish electrical breakdown threshold criteria, and scanning the electrode with respect to the surface so as to sequentially position the electrode over a plurality of locations on the surface, each location characterized by a surface error. When a respective location in the plurality of locations has a surface error that meets the electrical breakdown threshold criteria, electrical breakdown occurs, whereby the electrical breakdown results in a discharging pulse that polishes the surface.