Characteristics and Selection Guide for CMP Wafer Polishing Slurry

In the global planarization stage of wafer manufacturing, Chemical Mechanical Polishing (CMP) is a critical process. As a core consumable, CMP polishing slurry directly determines key wafer surface metrics such as flatness and defect rate, impacting the final chip performance and yield. Based on the core advantages and selection criteria of CMP polishing slurries, Jizhi Electronics provides practical reference for semiconductor manufacturing enterprises.

I. Four Core Characteristics of CMP Polishing Slurry

CMP polishing slurry is formulated from components like abrasives, oxidizers, and chelating agents, requiring a balance between “chemical corrosion” and “mechanical grinding.” Its core characteristics can be summarized as follows:

1. Precise and Controllable Chemical-Mechanical Synergy
   During polishing, the oxidizer first oxidizes the wafer surface material into easily removable oxides. The chelating agent then forms soluble complexes with these oxides, which are subsequently stripped away by abrasive grinding. High-quality polishing slurry achieves a balance where the “corrosion rate ≈ grinding rate,” avoiding issues like surface dimples or low removal efficiency.

2. Low Defects + High Surface Quality

   • Advanced process nodes impose extremely high requirements on wafer surface defects (scratches, residues, etc.). Polishing slurry minimizes mechanical damage and improves residue cleanability by employing soft abrasives (e.g., organic silica sol) and optimizing surfactant formulas, ensuring surface roughness meets specifications (Ra can be <0.1nm in the fine polishing stage).

3. Flexible Adjustment of Removal Rate and Selectivity
   Different polishing stages have varying needs: silicon substrate polishing requires a high removal rate (to quickly eliminate wafer warpage), while metal/dielectric layer polishing requires high selectivity (e.g., Cu/SiO2 selectivity >10:1 to avoid “dishing”). By adjusting oxidizer concentration and pH value, the slurry can be precisely matched to different process requirements.

4. Stable Compatibility and Assurance
   The slurry meets the semiconductor industry’s environmental requirements, being free of heavy metals and volatile organic compounds with low irritancy. It also possesses excellent batch-to-batch stability (removal rate deviation between batches <5%), preventing yield fluctuations in mass production due to consumable variability.

II. Selecting the Right Polishing Slurry by Process Stage

Different wafer processing stages have significantly different requirements for polishing slurry. Targeted selection is key:

1. Silicon Substrate Polishing (Rough + Fine)

   • Requirements: High removal rate for rough polishing; low roughness and no damage for fine polishing.

   • Recommended Types: Alkaline SiO2 abrasive slurry for rough polishing; soft organic silica sol slurry for fine polishing.

   • Application Scenarios: Final polishing of 8/12-inch silicon wafers, laying the foundation for subsequent photolithography and thin-film deposition.

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2. Dielectric Layer Polishing (SiO2/Si3N4)

   • Requirements: High removal rate, low defects, and high selectivity relative to metal layers.

   • Recommended Types: Alkaline colloidal SiO2 polishing slurry; for low-k dielectric polishing, choose slurries with low-hardness abrasives and a weakly alkaline system.

   • Application Scenarios: Planarization for Shallow Trench Isolation (STI) and Inter-Layer Dielectric (ILD).

3. Metal Layer Polishing (Cu/W)

   • Requirements: High metal removal rate, high selectivity, low residue.

   • Recommended Types: Acidic SiO2 abrasive slurry for Cu polishing; acidic Al2O3 abrasive slurry for W polishing.

   • Application Scenarios: Polishing of metal interconnect lines, contact holes/vias.

4. Special Polishing for Advanced Nodes (7nm and below)

   • Requirements: Ultra-low defects, atomic-level flatness, compatibility with extremely thin films.

   • Recommended Types: Atomic layer polishing slurry, abrasive-free polishing slurry.

   • Application Scenarios: Polishing of critical layers for advanced logic chips and 3D NAND memory chips.

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III. 3 Tips for Wafer Polishing Slurry Selection

1. Match Process Node and Wafer Size: For advanced nodes (e.g., 5nm), choose high-purity, fine-particle-size slurries. For 12-inch wafers, pay attention to uniform coverage to avoid edge effects.

2. Balance Cost and Supply Chain: For mass production, flexibly combine cost-effective domestic slurries for rough polishing with imported or high-end domestic CMP slurries for fine polishing (current domestic alternatives for fine polishing slurry perform on par with international brands). Also, ensure stable supplier capacity.

3. Customization for Special Processes: For polishing wide-bandgap semiconductors like SiC/GaN, collaborate with suppliers for custom formulations (e.g., high-hardness diamond abrasive slurry for SiC polishing).

As a company focused on the semiconductor field, Jizhi Electronics deeply understands the critical impact of CMP polishing slurry on wafer manufacturing yield. Leveraging our profound insight into industry processes, we can provide customers with customized services such as polishing slurry selection consultation and process adaptation testing. We aim to help semiconductor enterprises accurately match their needs, optimize production efficiency, and progress steadily on the path of advanced manufacturing.