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is one of the most complex and precise processes in the world and requires an extremely clean environment, with ultrapure water (UPW) as a critical component across all steps in fabricating the wafers. UPW used in semiconductor manufacturing is up to 1,000 times cleaner than water used in other industries, such as pharmaceuticals and medical devices, making it some of the most pristine water on the planet.

With continued advancements in artificial intelligence, semi-autonomous and electric vehicles, and other technologies, demand for semiconductor chips has never been higher. , global sales reached $46.2 billion in February 2024, a 16.3% year-over-year increase.

Companies around the world need more and higher-performing semiconductors. Making them is no easy task and requires stringent process control and contamination monitoring of UPW.

One of the key parameters for monitoring UPW purity and process effectiveness is total organic carbon (TOC), which measures the concentration of organic contaminants. While organic carbon occurs in all natural water sources, it significantly impacts semiconductor manufacturing processes, leading to defects, reduced yield, and potentially even complete production shutdowns, . Monitoring organic contamination helps protect chip quality and provides an excellent control point for overall UPW process management. As semiconductor technology advances, with smaller feature sizes and more complex designs, the tolerance for TOC contamination becomes even tighter, making effective TOC control a top priority for semiconductor manufacturers.

In the semiconductor industry, the required TOC levels in UPW are typically in the low parts-per-billion (ppb) range, with some critical processes demanding TOC concentrations below one ppb. The updates on these limit values. The ultra-low levels are driven by the need to minimize defects and maintain high yields rather than by regulatory compliance, as in other industries.

Given the critical importance of TOC control in semiconductor manufacturing, manufacturers need to deeply understand the risks and challenges associated with TOC contamination and the most effective strategies and technologies for maintaining ultra-low TOC levels in their UPW systems.

Risks of not catching TOC

Semiconductor chips include molecular-level functions, so precision is crucial in monitoring contaminants like TOC. In advanced lithography processes, even trace levels of organic compounds can interfere with the chemical reactions involved in patterning the wafer surface, leading to defects and yield loss.

Organic nitrogen compounds (a specific type of organic compounds that are part of TOC) are ubiquitous in the environment and can enter UPW systems through various sources, including source water, chemical additives, and even airborne contaminants. These compounds exist in source water around the globe, and are especially prevalent where local agricultural and industrial activities are high. Nitrogen-containing organic compounds, such as urea, are particularly difficult to remove from UPW systems and can be challenging to detect using conventional TOC monitoring technologies. Presently, as more emphasis is placed on recycle and reclaim efforts in fab UPW systems, the effective control of urea and other so-called recalcitrant contaminants becomes even more critical as these concentrations can amplify in the system over time.

Traditional TOC monitoring technologies, such as those based on direct conductivity measurements, are often inadequate for detecting organic nitrogen compounds in UPW. These technologies often fail to respond to the presence of these contaminants, leading to false negatives and a false sense of security for semiconductor manufacturers. However, advanced TOC monitoring using membrane conductometric technology is a proven method to accurately measure organic nitrogen compounds and provide reliable TOC data for process control*.

In addition to adopting advanced TOC monitoring technologies, semiconductor manufacturers must implement best practices for preventing and removing organic nitrogen compounds from their UPW systems. This may include optimizing water purification processes, such as reverse osmosis and ion exchange, to effectively remove these contaminants and implementing strict materials selection and handling protocols to minimize the introduction of organic nitrogen compounds into the UPW system.

TOC Measurement False Positives

All natural waters contain dissolved salts in various concentrations which dissociate in water to form charged ions such as chlorides, bromides, fluorides,sulfites, sulfates, nitrites, and nitrates. -. Inorganic ions like these are also introduced into UPW by some process steps within semiconductor fabs and must be controlled to prevent resultant adverse processing effects and product yield loss. When using direct conductometric technology, the presence of these inorganic ionic contaminants can lead to false positive TOC measurements. The semipermeable membrane used in membrane conductometric devices effectively prevents these false TOC measurements, and thus offers superior TOC process control over direct conductometric devices.

Any false negative or false positive measurements from direct conductometric technology create a risk that manufacturers can¡¯t afford to take.

How 91´óÉñsolves TOC challenges

91´óÉñoffers a comprehensive range of solutions to help semiconductor manufacturers maintain ultra-low TOC levels in their UPW systems. With decades of experience serving the semiconductor industry, 91´óÉñhas developed deep expertise in UPW treatment and TOC monitoring, enabling our experts to provide customized solutions that meet the stringent requirements of advanced semiconductor manufacturing processes.

At the core of Veolia¡¯s TOC monitoring solutions for the semiconductor industry are the Sievers M9e and M500e TOC analyzers. These state-of-the-art analyzers utilize advanced membrane conductometric technology to provide accurate and reliable TOC measurements down to parts-per-trillion (ppt). The membrane-based design of the Sievers analyzers allows them to detect a wide range of organic contaminants, including critical organic nitrogen compounds like urea, ensuring that semiconductor manufacturers have a complete picture of their UPW quality.

By providing accurate and sensitive TOC measurements, Sievers analyzers enable semiconductor manufacturers to maintain tight control over their UPW quality and minimize the risk of process disruptions due to TOC contamination. Beyond providing advanced TOC monitoring equipment, 91´óÉñworks closely with semiconductor manufacturers to optimize their entire UPW treatment process for effective TOC control. Contact our experts today to learn how we can help solve the toughest challenges in removing TOC from the semiconductor manufacturing process.

*J. Rydzewski, ¡°Identification of Critical contaminants by applying an understanding of different TOC measuring technologies¡±. Instruments Presentation at the Executive Forum at Wafertech 2001, Portland OR, December 4-5 2001.