Real Time Monitoring of NH₃ Concentration Using Diffusion Scrubber Sampling Technique and Result of Application to the Processing of Chemically Amplified Resists

Abstract

The application of chemically amplified resist is known to cause a problem in the accurate measurement of the concentration of basic gas species ( NH3, N-methylpyrrolidone (NMP)) in a clean room environment because it is sensitive to its environment. Among various methods of measurement, diffusion scrubber sampling method was selected and tested. The environmental sensitivity of a commercial chemically amplified resist, APEX-E, was also tested. For the concentration measurement, the method proved to be suitable for automation and good for measuring NH3 concentration as low as the sub ppb level (limit of detection ∼0.08 ppb). Some measurement results concerning various aspects of application are presented. Test results of the environmental stability of chemically amplified resists showed that NH3 concentration should be controlled to at least under 7.5 ppb for maintaining the process stability.

Sensitive Gas Analysis System on a Microchip and Application for On-Site Monitoring of NH3 in a Clean Room

“…Ion chromatographic, fluorescent, chemiluminescent, or chromogenic methods based on impinger or other concentration systems have been developed for NH 3 gas measurement. − Some systems are used for real applications with high reliability and sensitivity. However, continuous monitoring is usually difficult because it takes long time to concentrate the analyte molecules for sensitivity enhancement.…”

Hybrid Fluorometric Flow Analyzer for Ammonia

“…A recent review of ammonia sensing techniques is available. 7 Low-to subppbv NH 3 measurements are needed in semiconductor fabrication facilities to maintain device yield; [8][9][10][11] there is considerable interest in removing ammonia in clean rooms to levels as low as possible. 12 Higher levels of ammonia are of interest in large-scale animal operations because of hygiene, odor, and esthetic concerns.…”

“…A recent review of ammonia sensing techniques is available . Low- to sub-ppbv NH 3 measurements are needed in semiconductor fabrication facilities to maintain device yield; − there is considerable interest in removing ammonia in clean rooms to levels as low as possible .…”