How TOC Monitoring Drives Higher Chip Yield in Semiconductor Fabrication

Understanding the Impact of Trace Organic Carbon in Device Fabrication

mins

21 Oct, 2025

Total Organic Carbon (TOC) measures all organic carbon compounds in water or process chemicals, serving as a sensitive indicator of organic contamination. In semiconductor fabrication, ultrapure water (UPW) must have extremely low TOC levels because even trace levels of organics can degrade wafer surfaces, promote microbial growth, and cause defects that reduce chip yield and increase costs.

Over recent decades, TOC specifications have tightened from parts-per-billion to parts-per-trillion, reflecting the sensitivity of smaller-featured devices to minute contamination. Therefore, organic, as well as ionic, impurities must be tightly controlled. Whereas continuous monitoring using resistivity sensors ensures the detection of ionic contaminants, TOC sensors are required to detect organics.

Most TOC analyzers operate by oxidizing organics to carbonic acid, which is then measured by a conductivity sensor in the analyzer. This technique allows precise, real-time TOC monitoring in semiconductor fabrication that traditional ionic methods can't provide.

The Role of TOC in Preventing Defects in Microelectronics Manufacturing

The bulk of organic contaminants come from raw water sources, which vary seasonally and by type. Surface waters typically have higher organic loads than groundwater or reclaimed water. Contamination may also arise within purification systems from ion exchange resin degradation, leaching of plastics, pump lubricants, seals, or process chemicals. Because organics support microbial growth, TOC also indicates biological contamination risk.

From Wafer to Water: How Does TOC Impact Semiconductor Quality?

Effective TOC control involves multiple purification stages: reverse osmosis, micro-filtration, ion exchange, adsorption, and UV photo-oxidation.

Continuous TOC monitoring throughout the water treatment and distribution system promptly identifies quality issues before they affect production, enabling rapid corrective actions. Therefore, in addition to the water system itself, TOC monitoring is vital during semiconductor manufacturing steps where UPW contacts wafers and chemicals.

Cleaning before photolithography

Organic contaminants can prevent proper adhesion of the photoresist layer, leading to defects in the patterning process. TOC monitoring helps verify that cleaning agents and rinse water are free from organic impurities.

Cleaning after etching or implantation

Residual organic materials and other contaminants can interfere with subsequent processing steps and degrade device performance. Monitoring TOC ensures these contaminants are effectively removed to prevent defects.

Chemical Mechanical Planarization

This polishing step uses a slurry of chemicals and abrasives to smooth wafer surfaces. Organic contaminants in the slurry can cause surface scratches or leave residues. TOC analysis confirms the cleanliness of slurry and chemicals to maintain wafer quality.

While other steps use different contamination controls, TOC monitoring in semiconductor fabrication remains essential wherever ultrapure water contact occurs, in order to avoid costly yield losses.

Inside Clean Rooms: How Does Water Make the World’s Chips?

Our virtual tour of a semiconductor fab highlights the critical role of UPW analytics in silicon wafer production. See how real-time monitoring of analytics such as resistivity, pH, and total organic carbon ensures the highest quality and yield by preventing wafer defects, maintaining ultra-clean conditions, and supporting compliance with stringent industry standards.

By continuously tracking TOC in real time, manufacturers can detect contamination sources that traditional ionic tests might miss. This proactive approach safeguards device integrity, reduces production risks, and enhances manufacturing reliability and efficiency, ultimately supporting the ongoing advancement of semiconductor technology.

Moreover, integrating TOC monitoring in semiconductor fabrication with other analytical methods can provide a comprehensive contamination control strategy, ensuring the highest standards in chip manufacturing are consistently met.