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Total Reflection X-ray Fluorescence (TXRF)

Total Reflection X-ray Fluorescence (TXRF) utilizes extremely low-angle X-ray excitation of a polished wafer surface to obtain the concentration of surface metallic contaminants. The incident angle of the x-ray beam (typically 0.05°) is below the critical angle for the substrate and limits excitation to the outermost surface of the sample (~ top 80Å, depending on the material). The fluorescence signal emitted from the sample is characteristic of the elemental contaminants present.

A highly surface-sensitive technique, TXRF is optimized for analyzing surface metal contamination on semiconductor wafers such as Si, SiC, GaAs or sapphire.

Ideal Uses
  • Metallic surface contamination on semiconductor wafers
Technical Specifications

Signal Detected: Fluorescent x-rays from wafer surface
Elements Detected: S-U
Detection Limits: 109 – 1012 at/cm2
Depth Resolution: 30 – 80 Å (Sampling Depth)
Imaging/Mapping: Optional
Lateral Resolution/Probe Size: ~10 mm

Strengths
  • Trace element analysis
  • Survey analysis
  • Quantitative
  • Non-destructive
  • Automated analysis
  • Whole wafer analysis (up to 300 mm)
  • Can analyze many substrates, e.g. Si, SiC, GaAs, InP, sapphire, glass
Limitations
  • Cannot detect low-Z elements (Li, Na, Al)
  • Polished surface required for best detection limits