Magnetorheological Polishing Pad for Controlled SiC Wafer CMP
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Solution Overview
Problem
Current chemical mechanical polishing (CMP) methods for SiC wafers face issues such as waste of polishing liquid, uncontrollable chemical mechanical effects, and corrosion of equipment and polishing pads due to highly oxidative polishing liquids.
Innovation Solution
A magnetorheological elastic metal contact corrosion polishing pad is developed, which uses an external magnetic field to control the hardness of the polishing pad and balance chemical corrosion and mechanical removal on SiC wafers, thereby achieving efficient material removal and high-quality surface finishes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If highly corrosive polishing liquids (hydrofluoric acid, hydrogen peroxide, potassium hydroxide, potassium permanganate) are used to chemically etch the SiC wafer surface, then chemical etching effectiveness is improved, but equipment corrosion and polishing pad degradation occur, requiring regular maintenance and periodic replacement
Solution Approach 1:
The patent extracts the harmful strong acid and alkali polishing liquids from the system and replaces them with a magnetorheological elastic polishing pad containing metal powders and abrasive particles. The chemical etching function is transferred to metal particles that generate localized corrosion currents through contact with the SiC wafer surface, eliminating the need for highly corrosive bulk polishing liquids while maintaining effective chemical etching.
Solution Approach 2:
The patent introduces a magnetorheological elastic polishing pad as an intermediary between the polishing mechanism and the SiC wafer surface. This pad contains metal powders (Al, Fe, Cu, Zn) that act as mediators to generate controlled corrosion currents through contact with the wafer, replacing the direct action of strong acid/alkali liquids and reducing overall corrosion to equipment and pads.
2Productivity
If metal powders are injected onto the polishing pad surface through polishing liquid, then metal contact corrosion can be achieved, but metal powders flow with the polishing liquid and become waste slurry, resulting in uncontrollable chemical mechanical effects
Solution Approach 1:
The patent creates a composite magnetorheological elastic polishing pad by embedding metal powders, abrasive particles, and magnetic particles within an elastic matrix material. This composite structure prevents metal powders from flowing away with polishing liquid, as they are firmly held within the elastic matrix. The composite design enables controlled metal contact corrosion while eliminating metal powder waste and improving chemical mechanical polishing effectiveness.
Solution Approach 2:
The patent utilizes the magnetorheological property of the elastic polishing pad, which allows the pad's mechanical properties (such as hardness and elasticity) to be dynamically adjusted by applying an external magnetic field. This dynamic control enables optimization of the contact pressure and chemical mechanical effects between metal particles and the SiC wafer surface, improving material removal capability while preventing metal powder loss.
3Ease of operation
If magnetorheological elastic pad with magnetic particles is used to control mechanical removal process, then mechanical controllability is improved, but strong oxidative action from hydrogen peroxide and hydroxyl radicals causes corrosion of polishing liquid, equipment, and polishing pads
Solution Approach 1:
The patent changes the chemical composition parameters of the polishing system by replacing hydrogen peroxide-based oxidative polishing liquids with an electrolyte solution (such as sodium sulfate or potassium chloride). This parameter change eliminates the source of strong oxidative corrosion while maintaining the magnetorheological elastic polishing pad's mechanical controllability through magnetic field application. The electrolyte solution supports metal contact corrosion without generating harmful hydroxyl radicals.
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 magnetorheological elastic metal contact corrosion polishing pad effectively controls chemical and mechanical actions, reducing waste and equipment corrosion, while achieving high material removal rates and low surface roughness, thus enhancing the efficiency and quality of SiC wafer polishing.
Implementation Method 1
a magnetorheological elastic pad for semiconductor wafer CMP and its application... magnetic particles (CIP@Fe3O4) can undergo a Fenton reaction under an action of hydrogen peroxide polishing liquid
Implementation Method 2
Metallic contact corrosion can generate corrosion currents on the surfaces of metal and contact materials, leading to the formation of highly oxidative holes that corrode the workpiece surface
Implementation Method 3
mechanical material removal through the relative motion between the polishing pad, abrasive, and the wafer
Implementation Method 4
The electrolyte solution is non-corrosive, the solution is between the SiC wafer and the magnetorheological elastic metal contact corrosion polishing pad
Data Source
AI summary
A method for chemical mechanical polishing of a SiC wafer based on a magnetorheological elastic metal contact corrosion polishing pad, including following steps of: attaching a magnetorheological elastic metal contact corrosion polishing pad to a polishing disk adding an electrolyte solution onto the magnetorheological elastic metal contact corrosion polishing pad; wherein the electrolyte solution is non-corrosive, the electrolyte solution is added between the SiC wafer and the magnetorheological elastic metal contact corrosion polishing pad; applying a polishing magnetic field to the magnetorheological elastic metal contact corrosion polishing pad to control the contact state of the abrasive and metal powders on the SiC wafer; to achieve a control over a chemical reaction intensity of the metal powders on a SiC wafer surface in the electrolyte solution, and to achieve a mechanical removal of materials from the SiC wafer surface via the abrasive.