A “New” Method for Measuring 20nm Particles in Ultrapure Water
David Blackford Ph.D.
Fluid Measurement Technologies, Inc.
CT Associates, Inc.
The objective of the International Technology Roadmap for Semiconductors (ITRS) is “to ensure cost-effective advancements in the performance of the integrated circuit and the products that employ such devices, thereby continuing the health and success of the semiconductor industry”. However, the latest version of the Roadmap concludes that the current optical particle counting technology (counting particles >50 nanometers) is unable to detect particles at the critical size, defined as half the line width used to manufacture DRAM memory devices. The inability to count particle <50 nm poses a risk for semiconductor manufacturers where shrinking critical dimensions may lead to increased defect densities and increased yield loss. One of the purposes of the ITRS Roadmap is to encourage instrumentation vendors to develop better metrology as line widths continue to shrink. With this goal in mind the authors have developed a modified version of the Nonvolatile Residue Monitor (NRM) that is capable of distinguishing real particles from residue agglomerate particles. This paper describes the fundamentals for the technique and presents results from a “proof of concept” prototype. The prototype was used to measure 20nm particles as an ultra-filtration system was brought on line at semiconductor ultrapure water (UPW) system.
Ultrapure Water, January 2009.