Polishing Composition for Semiconductor Wafer LPD Reduction
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Solution Overview
Problem
Current polishing compositions for semiconductor wafers are ineffective in reducing light point defects (LPDs) smaller than 0.065 μm, which are caused by scars during the polishing process and cannot be removed by finish polishing or washing.
Innovation Solution
A polishing composition containing a water-soluble polymer such as polyvinylpyrrolidone and an alkali, along with abrasive grains, is used to form a hydrophilic film on the wafer surface, dispersing vertical forces and reducing defects during preliminary polishing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional polishing compositions are used for finish polishing, then the polishing process can be completed, but the number of LPDs smaller than 0.065 μm cannot be reduced
Solution Approach 1:
The patent changes the chemical parameters of the polishing composition by introducing specific water-soluble polymers (polyvinylpyrrolidone with molecular weight 10,000-1,000,000 and poly(N-vinylformamide)) and controlling the alkali content (0.1-10 g/L), which fundamentally alters how the composition interacts with the wafer surface during polishing, enabling reduction of previously unavoidable LPDs
Solution Approach 2:
The patent creates a composite polishing composition by combining water-soluble polymers with specific molecular weights, alkalis, and abrasive particles. This composite structure allows the polymer to form a protective film while the abrasive particles perform material removal, achieving both defect reduction and effective polishing
2Manufacturing precision
If washing technique is improved to remove particles, then large LPDs (0.12 μm or larger) are reduced, but small LPDs (>0.065 μm) caused by scars remain
Solution Approach 1:
The patent applies preliminary action by modifying the polishing process itself to prevent scar formation. The water-soluble polymer forms a protective film on the wafer surface during preliminary polishing, preventing the formation of scars that would later become small LPDs, thereby eliminating the need for subsequent removal steps
3Manufacturing precision
If polyvinylpyrrolidone is used to form hydrophilic film, then LPDs are reduced, but polishing rate must be maintained
Solution Approach 1:
The patent carefully controls the molecular weight parameter of polyvinylpyrrolidone (10,000-1,000,000) and the concentration of alkali (0.1-10 g/L) to optimize the balance between film-forming capability and polishing rate. This parameter optimization ensures that the hydrophilic film provides sufficient protection against LPDs while allowing the abrasive particles to maintain effective material removal speed
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 composition effectively reduces the number of LPDs attributable to the polishing process while maintaining a suitable polishing rate and preventing surface roughness, with polyvinylpyrrolidone being particularly effective in forming a sufficient hydrophilic film to prevent defects.
Implementation Method 1
forming a hydrophilic film on the wafer surface, dispersing vertical forces
Implementation Method 2
polishing a surface of a semiconductor wafer using the polishing composition
Data Source
AI summary
A polishing composition contains at least one water soluble polymer selected from the group consisting of polyvinylpyrrolidone and poly(N-vinylformamide), and an alkali, and preferably further contains at least one of a chelating agent and an abrasive grain. The water soluble polymer preferably has a weight average molecular weight of 6,000 to 4,000,000. The polishing composition is mainly used in polishing of the surfaces of semiconductor wafers such as silicon wafers, especially used in preliminary polishing of the surfaces of such wafers.