The Art and Science of Wet Wafer-Cleaning Technology

While it might not receive as much attention as extreme ultraviolet (EUV) lithography, wet wafer cleaning and surface preparation remains one of the most critical processes in semiconductor manufacturing. Device reliability, yield and long-term performance are all directly linked to wafer cleanliness as devices pass through hundreds of process steps including deposition, implantation, polishing, etching, patterning, and interconnect process steps.

Even a single particle or trace contaminant can create a killer defect that ultimately leads to device failure. As semiconductor devices continue to scale and expand into AI, high-performance computing (HPC), automotive, communications and industrial applications, the margin for error continues to shrink. Consequently, wafer cleaning has become an increasingly important contributor to both manufacturing yield and device reliability.

At the same time, conventional cleaning approaches are often insufficient for today’s complex device architectures. Advanced structures—including FinFETs, 3D NAND, gate-all-around (GAA) transistors, through-silicon vias (TSVs) and other advanced packaging features—require cleaning processes that remove particles and residues without damaging increasingly delicate structures. Rather than being treated as a supporting process, wet cleaning has become an integral part of advanced semiconductor manufacturing.

With that in mind, let’s look at how wet wafer-cleaning technology has evolved from an “empirical art” to a “precise science” and how modern single-wafer cleaning solutions enable manufacturing of today’s most advanced semiconductor devices.

How Many Cleaning Steps Are There?

As technology nodes have continued to shrink and device architectures have become more three-dimensional, the number of cleaning steps has increased dramatically.

While 45nm manufacturing required roughly 150–200 cleaning operations throughout the process flow, advanced logic and memory devices (10nm and below) require more than 800 cleaning and surface preparation steps, including:

Photoresist strip
Post-etch cleaning
Post CMP cleaning
Implant strip
Lateral interlayer wet etch for 3D-NAND and GAA
General wafer cleaning
Particle and residue removal
Backside cleaning for advanced lithography
Surface preparation prior to deposition and other critical process steps

Although EUV lithography has reduced the number of multiple-patterning steps, today’s smaller feature sizes, higher aspect ratio structures and increasingly sensitive materials place even greater demands on cleaning technology. Success depends not only on removing contaminants, but on preparing wafer surfaces without introducing damage or variability.

Wet Wafer-Cleaning Technologies Evolve

For decades, different wet wafer-cleaning technology approaches have been used to remove unwanted particles, contaminants and metallics from the wafer surface, preparing it for the next step in the process. In their book, Handbook of Silicon-Wafer Cleaning Technology, co-editors Karen Reinhardt and Werner Kern state that “in the past, wafer cleaning and surface preparation were considered more of an art than a science.” But that has changed.

Wet Bench Approach

In the early days of semiconductor manufacturing, when wafers measured 77mm, 100mm, and technology nodes were well above 90nm, open wet bench batch processing provided sufficient throughput.

Batches of 25–50 wafers were immersed in cleaning chemistries to remove particles, metallic contaminants and residues. While effective for larger geometries, immersion processing became increasingly difficult to control as feature sizes shrank. Chemistry runoff could redeposit particles, and open processing environments presented additional contamination and safety concerns.

Today, wet bench processing is generally limited to selected mature applications where advanced feature cleaning is not required.

Batch Spray Cleaning

Batch spray processing represented the next step in wafer cleaning evolution. Spraying increased chemistry velocity, improving particle removal compared to immersion cleaning while providing a safer enclosed environment.

However, because multiple wafers are processed simultaneously, batch spray systems still face inherent limitations, including non-uniform chemistry access between closely spaced wafers and reduced cleaning effectiveness for increasingly complex device structures.

Single-Wafer Cleaning

Single-wafer processing has become the preferred approach for advanced semiconductor manufacturing on both 200mm and 300mm wafers.

Processing each wafer individually provides significantly greater control over chemistry delivery, process uniformity and repeatability. While single-wafer systems traditionally sacrificed some throughput compared to batch processing, advances in chamber design, automation and parallel processing have enabled manufacturers to achieve both high productivity and superior cleaning performance.

Single-wafer cleaning also provides the flexibility needed to optimize individual cleaning recipes for increasingly diverse process steps throughout advanced logic, memory and specialty semiconductor manufacturing.

Advanced Megasonic Cleaning

ACM Research has continued to advance single-wafer cleaning through several proprietary technologies that improve cleaning effectiveness while minimizing feature damage.

Its Space Alternated Phase Shift (SAPS™) megasonic technology precisely controls acoustic energy distribution to achieve highly uniform cleaning performance across the wafer surface. Timely Energized Bubble Oscillation (TEBO™) technology further stabilizes cavitation behavior, reducing the risk of pattern damage while effectively removing particles and residues from increasingly delicate structures.

Combined with ACM’s advanced single-wafer cleaning platform architecture, these technologies enable highly selective, low-damage cleaning for advanced device geometries, including high-aspect-ratio structures and other challenging applications found in today’s leading-edge semiconductor manufacturing.

As device complexity continues to increase, ACM has expanded its wet processing portfolio beyond cleaning to include a broad range of single-wafer wet processing technologies for cleaning, wet etching, photoresist stripping, bevel processing and electrochemical processes. These integrated platforms allow manufacturers to optimize multiple critical wet processing steps while maintaining high productivity and process control.

Future Proofing Wet Wafer Cleaning

Wet wafer cleaning has evolved from relatively simple batch immersion processing into a highly engineered science that plays a central role in advanced semiconductor manufacturing. As device architecture continues to become more complex, cleaning technologies must deliver exceptional particle and metallic removal efficiency while protecting increasingly delicate structures.

ACM Research has developed a portfolio of advanced single-wafer wet processing technologies aimed at helping manufacturers achieve the cleanliness, process uniformity and yield required for next-generation logic, memory and specialty semiconductor devices. These include its proprietary SAPS™ and TEBO™ megasonic innovations and Ultra C Tahoe advanced cleaning system, which combines the advantages of wet-bench and single-wafer SPM cleaning in a single tool. With these offerings in its arsenal, ACM is well positioned to enable chipmakers to continue bringing groundbreaking new devices to market.

To learn more about our advanced wet processing technologies, explore our technical resources.

Wet Wafer Cleaning FAQs

Wet wafer cleaning is one of the most critical processes in semiconductor manufacturing because device reliability, yield, and long-term performance are all directly linked to wafer cleanliness as wafers undergo hundreds of process steps. The stakes are high: even a single particle or trace contaminant can create a killer defect that ultimately leads to device failure. As semiconductor devices continue to scale and expand with the growth of AI, high-performance computing, automotive, communications, and industrial applications, the margin for error keeps shrinking — making cleaning an increasingly important contributor to both manufacturing yield and device reliability.

The number of cleaning steps has increased dramatically as technology nodes have shrunk and device architectures have become more three-dimensional. Repetitive cleaning is required between every lithography, etching, and deposition process to prevent microscopic contaminants from ruining the devices. Early 45nm manufacturing required roughly 150–200 cleaning steps throughout the process flow, while advanced logic and memory devices now require several hundred steps that include both cleaning and surface preparation—such as photoresist strip, post-etch cleaning, implant strip, particle and residue removal, backside cleaning, and pre-deposition surface prep. Even though EUV lithography has reduced multiple-patterning steps, today’s smaller feature sizes, higher aspect ratio structures, and more sensitive materials place even greater demands on cleaning technology.

Wet wafer cleaning has evolved from relatively simple batch immersion processing into a highly engineered science. In the early days, open wet-bench batch processing simultaneously immersed 25–50 wafers in cleaning chemistries and provided sufficient throughput for larger geometries, but the process became difficult to control as feature sizes shrank. Batch spray cleaning followed, increasing chemistry velocity and offering a safer enclosed environment, though it still faced non-uniform chemistry access between closely spaced wafers. Today, single-wafer processing has become the preferred approach for advanced manufacturing on both 200mm and 300mm wafers, providing significantly greater control over chemistry delivery, process uniformity, and repeatability.

SAPS™ and TEBO™ are two of ACM Research’s proprietary technologies that improve cleaning effectiveness while minimizing feature damage. Space Alternated Phase Shift (SAPS™) megasonic technology precisely controls acoustic energy distribution to achieve highly uniform cleaning performance across the wafer surface, while Timely Energized Bubble Oscillation (TEBO™) technology provides controlled cavitation without bubble implosion to reduce the risk of pattern damage while effectively removing particles from increasingly delicate structures. Combined with ACM’s advanced single-wafer cleaning platform architecture, these technologies enable highly selective, low-damage cleaning for advanced device geometries, including high-aspect-ratio structures. For example, the combination of TEBO-assisted cleaning with super critical CO2 drying prevents pattern damage while cleaning ultra-sensitive 3D transistor structures found in advanced logic devices.

Processing each wafer individually provides significantly greater control over chemistry delivery, process uniformity, and repeatability, achieving increased particle performance compared to batch approaches. Advanced device architectures, such as FinFETs, 3D NAND, gate-all-around (GAA) transistors, through-silicon vias (TSVs), and other advanced packaging features, require cleaning processes that remove particles and residues without damaging increasingly delicate structures. ACM Research has expanded its single-wafer wet processing portfolio beyond cleaning to include wet etching, photoresist stripping, bevel processing, and electrochemical processes, allowing manufacturers to optimize multiple critical wet processing steps while maintaining high productivity and process control.