Introduction to Wafer Cleaning Equipment

In the semiconductor manufacturing process, wafer cleaning is a critically important step. After undergoing multiple manufacturing stages, wafers often accumulate a large number of contaminants on their surfaces—contaminants composed of polymers, photoresists, etching residues, and other materials. These particles and impurities can severely affect the geometric features and electrical performance of chips in subsequent processing steps. As semiconductor process nodes continue to shrink, the size of these contaminants has gradually decreased to the nanometer scale, significantly increasing the difficulty of removal and leading to a corresponding rise in the number of residual particles on wafer surfaces. Meanwhile, the continuous reduction in feature sizes further complicates the cleaning process. Consequently, the importance of high-performance wafer cleaning equipment is becoming increasingly evident.

I. Cleaning Principles and Technical Approach

Semiconductor cleaning refers to a process that removes various contaminants adhering to the surface of silicon wafers without damaging the wafer’s surface or its underlying structure. Depending on the cleaning medium used, this process can be broadly categorized into two main technological approaches: wet cleaning and dry cleaning. Currently, wet cleaning dominates the market, accounting for approximately 85% of the overall market share, and is expected to remain the mainstream cleaning technology in the foreseeable future. In this method, liquid chemical agents are employed to oxidize, etch, or dissolve contaminants on the wafer’s surface. Wet cleaning methods can be further divided into brush-based cleaning and chemical cleaning.

Wet-process cleaning employs specific chemical solutions and deionized water tailored to different process requirements, enabling non-destructive cleaning of wafer surfaces to remove particles, native oxide layers, organic contaminants, metallic impurities, sacrificial layers, and residues from chemical-mechanical polishing. Brushing-type equipment relies on physical brushing as its core mechanism and can effectively remove particulates ranging in size from micrometers and larger. Chemical-cleaning equipment primarily includes immersion cleaning tanks, megasonic cleaning tanks, and rotary spray cleaners; the underlying processes of these devices largely derive from the classic RCA cleaning method and its derivative technologies.

Dry cleaning is a new cleaning technology that has emerged in recent years. It does not require the use of liquid solvents and achieves pollutant removal through gas-phase chemical reactions or physical ion bombardment. This technique offers advantages such as zero wastewater discharge and the ability to perform localized, selective cleaning. The main methods include thermal oxidation and plasma cleaning. However, this technology is still in the development stage, and in complex scenarios—such as cleaning 3D NAND stacked structures and copper interconnect processes—wet cleaning remains irreplaceable.

II. Mainstream Equipment and Key Technologies

In wet-process cleaning systems, based on equipment structure, cleaning machines can be categorized into tank-type cleaners, single-wafer cleaners, combined cleaners, and batch rotary spray cleaners. Among these, single-wafer cleaning equipment holds the largest market share and is widely used in both front-end and back-end processes of integrated circuits, covering multiple cleaning steps following film deposition, etching, ion implantation, polishing, and metal deposition. Single-wafer cleaning enables finer process control and improves uniformity both between wafers and within individual wafers, thereby helping to enhance product yield and avoiding the risk of cross-contamination that may arise from tank-type cleaning.

A single-chamber cleaning equipment typically consists of a main frame, a wafer handling system, a process chamber, a chemical solution supply and distribution system, and software control and electrical modules. Its core cleaning technology is based on rotary spray technology: a motor drives the wafer to rotate at high speed while simultaneously spraying cleaning fluid onto its surface. Centrifugal force ensures that the liquid spreads evenly across the wafer surface and quickly detaches from it.

Some key cleaning technologies are particularly important in advanced manufacturing processes: The high-temperature SPM cleaning process is primarily used to remove photoresist residues and their polymers left behind after etching and ion implantation; the back-side wafer cleaning process is designed to eliminate contaminants such as metals adhering to the back side of the wafer, which is crucial for protecting expensive equipment like lithography machines; nanospray cleaning technology uses high-pressure gas to atomize liquids into extremely fine droplets, which remove surface particles through impact forces; and megasonic cleaning technology leverages the cavitation and microstreaming effects generated by high-frequency sound waves in liquids, making it especially effective for removing small-sized particles and contaminants from inside structures with high aspect ratios.

III. Development History and Market Landscape

From a historical perspective, in the early days of semiconductor manufacturing in the 1950s, wafer cleaning primarily relied on simple physical scrubbing. In 1965, RCA developed the standard RCA cleaning method, marking the beginning of modern wet-process cleaning technology. In the early 1970s, the first immersion-type wet-cleaning equipment was introduced; subsequently, with the incorporation of technologies such as megasonic waves and rotary spray systems, cleaning performance and efficiency were continuously enhanced. After the 1990s, as copper interconnect processes became widespread and process dimensions continued to shrink, cleaning techniques kept evolving and improving. Since 2010, as process nodes have entered the 14nm and below range, dry-process cleaning has begun to be explored experimentally; however, wet-process cleaning still remains the dominant approach.

Cleaning is the process with the most steps in chip manufacturing, accounting for more than 30% of all manufacturing process steps. Investment in semiconductor cleaning equipment accounts for approximately 7% of the total investment in wafer fabrication equipment. As technology nodes continue to advance, the number and importance of cleaning processes will keep increasing. According to industry data, the global front-end cleaning equipment market size was about US$5.33 billion in 2024, with the Chinese mainland accounting for roughly US$2.27 billion, or 42.6% of the global market—a share that closely matches China’s overall global share in the semiconductor equipment market.

The global cleaning equipment market exhibits a highly concentrated competitive landscape, with four companies—Japan’s SCREEN, Tokyo Electron (TEL), U.S.-based Lam Research, and South Korea’s SEMES—accounting for approximately 86% of the global market share combined. As industry leader, SCREEN’s SU-series cleaners provide extensive coverage for advanced manufacturing processes; Tokyo Electron’s CELLESTA SCD series boasts significant advantages in the field of 3D NAND cleaning; and Lam Research’s EOS series incorporates plasma confinement and AI-driven process optimization technologies. Meanwhile, domestic Chinese companies such as Shengmei Semiconductor, North Huachuang, and ZhiChun Technology have made remarkable progress in recent years, achieving independent innovation in key technological areas including ultrasonic wave uniformity control, high-temperature sulfuric acid cleaning, and chemical recovery. Some of their equipment has already entered the international supply chain and secured bulk orders from leading domestic manufacturers.

IV. Future Trends and Challenges

In the future, the continuous miniaturization of integrated circuit manufacturing processes and the advancement of three-dimensional structures will be the key driving forces behind the development of cleaning equipment. On one hand, as feature sizes shrink, the tolerable size of contaminants becomes smaller, increasing the demand for cleaning and calling for further improvements in cleaning efficiency and precision. On the other hand, the number of layers in 3D NAND stacks is expected to exceed 500, and GAA FET structures incorporate multiple vertically stacked nanosheets. These complex three-dimensional architectures require cleaning solutions to effectively penetrate deep into tiny holes and achieve uniform cleaning without damaging the extremely fragile structures—posing entirely new challenges to equipment technology.

Environmental pressures are also driving innovation in cleaning technologies. Leading companies are significantly reducing chemical waste discharge and resource consumption during the production process by adopting technologies such as sulfuric acid recycling, efficient chemical recovery, and reduced ultra-pure water usage—thus complying with increasingly stringent environmental regulations. The industry anticipates that the global semiconductor equipment market will continue to grow, and the Chinese market will remain a key player. Domestic enterprises need to keep breaking through technological barriers in cutting-edge fields such as megasonic technology and dry-process cleaning, while leveraging supportive industrial policies to further accelerate the localization and substitution of high-end cleaning equipment.

Semiconductor cleaning equipment is a critical enabler for ensuring high yield and high performance in chip manufacturing, and its technological evolution closely mirrors the advancement of semiconductor fabrication processes. From mainstream wet-process cleaning to emerging dry-process technologies, and from the precise control offered by single-wafer equipment to innovative solutions designed to address three-dimensional structures, the cleaning equipment industry is steadily moving toward greater efficiency, higher precision, and enhanced environmental sustainability.

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