A Real-Time Method for Monitoring Contaminants in Electronic Specialty Gases

US Patent 6748334

Objectives

• To provide high sensitivity detection of impurities (low ppb)
• To reduce the time response typically associated with FTIR (from minutes to seconds)
• To reduce the effects of spectrometer drift

Methodology

Spectra Stream

Spectra Stream Parameters

• W = Sampling Window Size (# sampling scans)
• b = Number of Backgrounds per sampling window

Instrument Parameters

• Bomem MB100
• DTGS Detector (0.4 cm/sec)
• 2 cm-1 instrument resolution
• Time Resolution 11 sec. per sample + background
• CIC Ranger Gas Cell (1.7 liters / 9.6 meters)
• Flow Rate 1slpm

CH4 Detection

CO2 Detection

CO Detection

Water Detection

Standard Error of Different Gases at Different Concentrations

Detection of 500 ppb of CO in N2

Detectionof 10 ppb of CO2 in N2

Spectra Stream Advantages for Process Control

• Early Detection of changes in impurity concentrations (seconds)
• Real Time monitoring of process gases
• Reduction of the interfering effects of spectrometer drift
• Assures reliable and controlled etching of semiconductors wafers