Wet Etching Equipment vs. Wet Cleaning Equipment: A Distinction in Positioning Between Core Patterning Processes and Comprehensive Process-Flow Support

In the semiconductor manufacturing process, wet etching equipment and wet cleaning equipment play distinctly different roles. The former is used in the pattern-transfer stage following lithography to fabricate the core structural features of devices, while the latter is employed throughout the entire wafer fabrication flow as a fundamental enabling process. As process nodes advance toward more sophisticated technologies, the differences in application scenarios and performance requirements between the two further widen. This paper reviews their typical applications and node-specific adaptation characteristics.

I. Typical Application Scenarios and Node Compatibility of Wet Etching Equipment

Wet etching is primarily used in the pattern-transfer stage following lithography to fabricate the core structures of devices:

• Patterned dielectric layers: etching silicon dioxide and silicon nitride to form isolation trenches and contact holes. This process requires high selectivity and excellent etch uniformity to prevent damage to the underlying silicon or the mask.
• Polycrystalline silicon gate fabrication: requires strict control of etch depth and sidewall verticality, with extremely high demands on etch-rate stability and lateral undercut.
• Metal wiring fabrication: Etching aluminum and copper to form interconnects requires precise control of pattern accuracy to prevent short circuits or open circuits.
• Silicon etching: Used to form structures such as shallow-trench isolation and silicon vias, with stringent requirements for etch uniformity and reliable endpoint detection.

Process-node adaptation: Because wet etching is isotropic and suffers from lateral undercut, it is primarily suited for mature processes at 14 nm and above. In advanced nodes, dry etching is predominantly used for critical structures; however, wet etching still finds applications in non-critical structures and certain specialized processes. At mature nodes, the tolerances for etch rate and selectivity are somewhat looser, but yield requirements must still be met.

II. Typical Application Scenarios and Node Adaptation for Wet Cleaning Machines

Wet cleaning is employed throughout the entire wafer fabrication process and serves as a fundamental, mission-critical process. The cleanliness requirements for each process step have continuously tightened with advancing technology nodes:

• Wafer pre-treatment: removal of as-manufactured contaminants. Particle removal efficiency must exceed 99%, and metal residue levels must be below specified thresholds.
• Pre-lithography cleaning: removes the native oxide layer and enhances photoresist adhesion. This process is highly sensitive to surface roughness and organic residue levels; otherwise, lithographic resolution will be compromised.
• Post-lithography cleaning: removal of residual photoresist and developer residues. Surface defects, such as scratches, must be avoided.
• Post-etch/ deposition cleaning: removal of chemical byproducts and particulates. The requirements for metal residue levels and particle removal efficiency are the most stringent, as they directly affect device leakage current and breakdown risk.
• Pre-encapsulation cleaning: Ensures the reliability of the encapsulation bond. Key control parameters include organic residue levels and surface defect density.

Process-node adaptation: Whether using mature or advanced process technologies, cleaning is an indispensable step. As feature sizes shrink to 7 nm and below, the requirements for particle removal efficiency (must exceed 99.99%), metal residue levels (must be reduced to sub-ppb levels), and surface defect density (approaching zero defects) are increasing exponentially, further underscoring the critical importance of cleaning processes. Consequently, equipment has evolved from batch-type systems to single-wafer, high-precision cleaning platforms.

Conclusion

Wet etching equipment is used in the core patterning process to transfer patterns at specific process nodes, and its applications are relatively concentrated; wet cleaning equipment, on the other hand, serves as a process-wide enabler, ubiquitous throughout the entire flow and subject to increasingly stringent requirements as process technology advances. Accurately distinguishing the application scenarios and node compatibility of these two types of equipment helps to allocate equipment resources rationally in production line configuration and to establish scientific evaluation criteria tailored to different process steps.

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