Acidic CMP Slurry Selective Silicon Nitride Polishing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional chemical-mechanical polishing (CMP) compositions for semiconductor substrates exhibit inadequate polishing rates and selectivity for silicon nitride, leading to poor manufacturing yields and high scratch defects due to high abrasive concentrations.
Innovation Solution
An acidic aqueous polishing composition containing particulate ceria abrasive, non-polymeric unsaturated nitrogen heterocycle compounds, cationic polymers, and polyoxyalkylene polymers is used, with a pH range of 2 to 6, to selectively remove silicon nitride while minimizing polysilicon and silicon oxide removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional CMP compositions use high abrasive concentrations to increase polishing rate, then polishing speed improves, but scratch defects increase and manufacturing yield decreases
Solution Approach 1:
The invention changes the chemical parameters of the polishing composition by using acidic pH (2-6) and specific additive concentrations instead of relying on high abrasive concentrations. This allows achieving high polishing rates through chemical enhancement rather than mechanical abrasion intensity, thereby avoiding scratch defects caused by excessive abrasive particles.
Solution Approach 2:
The invention uses a composite polishing composition containing ceria abrasive particles combined with specific additives (polymer, sulfur compound, and/or carboxylic acid) in optimized concentrations. This composite formulation enhances polishing efficiency chemically, allowing reduced abrasive concentration while maintaining or improving polishing rate, thus reducing scratch defects.
2Productivity
If conventional CMP compositions use high abrasive concentrations to achieve adequate polishing rates, then material removal speed increases, but selectivity for silicon nitride decreases
Solution Approach 1:
The invention achieves high silicon nitride selectivity by optimizing the chemical composition parameters: acidic pH (2-6), specific ceria concentration (0.01-5 wt%), and controlled amounts of polymer (10-1000 ppm), sulfur compounds (10-1000 ppm), and carboxylic acids (10-1000 ppm). These parameter optimizations enable selective silicon nitride removal without requiring high abrasive concentrations that would compromise selectivity.
Solution Approach 2:
The composite polishing composition combines ceria abrasive with specific chemical additives (polymer, sulfur compound, and/or carboxylic acid) in optimized ratios. This composite formulation enhances the chemical reactivity toward silicon nitride specifically, achieving high removal rates with improved selectivity over silicon oxide and polysilicon, without needing excessive abrasive concentrations.
3Productivity
If conventional CMP compositions increase polishing aggressiveness to improve removal rates, then productivity increases, but control over selective removal of different materials decreases
Solution Approach 1:
The invention provides independent control over polishing aggressiveness and selectivity through separate parameter adjustments: pH level (2-6), ceria concentration (0.01-5 wt%), polymer content (10-1000 ppm), sulfur compound content (10-1000 ppm), and carboxylic acid content (10-1000 ppm). This multi-parameter control system allows optimizing removal rates for different materials (silicon nitride, silicon oxide, polysilicon) independently, enabling precise control over selective removal while maintaining high productivity.
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 achieves high silicon nitride removal rates with low polysilicon and adjustable silicon oxide removal rates, reducing scratch defects and enhancing manufacturing efficiency.
Implementation Method 1
The relative movement of the pad and substrate serves to abrade the surface of the substrate to remove a portion of the material from the substrate surface
Implementation Method 2
The carrier assembly provides a controllable pressure to the substrate, urging the substrate against the polishing pad
Implementation Method 3
The polishing of the substrate surface typically is further aided by the chemical activity of the polishing composition (e.g., by oxidizing agents, acids, bases, or other additives present in the CMP composition)
Implementation Method 4
An acidic aqueous polishing composition containing particulate ceria abrasive, non-polymeric unsaturated nitrogen heterocycle compounds, cationic polymers, and polyoxyalkylene polymers is used, with a pH range of 2 to 6
Data Source
Figure 1
AI summary
The present invention provides an acidic aqueous polishing composition suitable for polishing a silicon nitride-containing substrate in a chemical-mechanical polishing (CMP) process. The composition, at point of use, preferably comprises 0.01 to 2 percent by weight of at least one particulate ceria abrasive, 10 to 1000 ppm of at least one non-polymeric unsaturated nitrogen heterocycle compound, 0 to 1000 ppm of at least one cationic polymer, optionally, 0 to 2000 ppm of at least one polyoxyalkylene polymer, and an aqueous carrier therefor. The cationic polymer preferably is selected from a poly(vinylpyridine) polymer, a quaternary ammonium-substituted acrylate polymer, a quaternary ammonium-substituted methacrylate polymer, or a combination thereof. Methods of polishing substrates and of selectively removing silicon nitride from a substrate in preference to removal of polysilicon using the compositions are also provided.