Wafer surface contamination metrology with TXRF/VPD

Ultra-trace measurement of elemental surface contamination

TXRF-V450

TXRF analysis can gauge contamination in all fab processes, including cleaning, litho, etch, ashing, films, etc. The TXRF-V450 can measure elements from Na through U with a single-target, 3-beam X-ray system and a solid-state detector system.

The TXRF-V450 includes Rigaku's patented XYθ sample stage system, an in-vacuum wafer robotic transfer system, and new user-friendly windows software. All of these contribute to higher throughput, higher accuracy and precision, and easy routine operation.

Integrated VPD capability enables automatic VPD preparation of one wafer while a TXRF measurement is made on another wafer for the highest sensitivity and high throughput. VPD-TXRF eliminates the operator variability that may occur with ICP-MS, and VPD-TXRF can be completely controlled via factory automation. VPD recovery from selected areas, including the bevel area, is available.

Optional Sweeping TXRF software enables mapping of the contaminant distribution over the wafer surface to identify "hot spots" that can be automatically re-measured at higher precision.

Optional ZEE-TXRF capability overcomes the historical 15mm edge exclusion of original TXRF designs, enabling measurements to be made with zero edge exclusion.

Optional BAC-TXRF capability enables fully-automated front-side and back-side TXRF measurements of 450mm wafers with non-contacting wafer flipping.

Features

  • Accepts 450 mm and 300 mm wafers
  • Wide range of analytical elements (Na~U)
  • Light-element sensitivity (for Na, Mg, and Al)
  • Single target 3-beam method and XYθ stage are unique to Rigaku, enabling highly accurate ultra trace analysis over the entire wafer surface
  • Integrated, fully-automated VPD preparation for highest sensitivity
  • 1E7 atoms/cm² detection limits
  • Import measurement coordinates from defect inspection tools for follow-up analysis
  • Multitasking: simultaneous VPD and TXRF operation for highest throughput

TXRF-V450 specifications

  • Size of wafer: 450 mm and 300 mm
  • Rotating-anode X-ray source
  • Sample stage: XY θ stage
  • Solid-state detector
  • Oil-free electrical transformer
  • Three-beam excitation
  • Automatic optics alignment
  • Data import from external surface defect inspection tool
  • Integrated VPD capability

TXRF-V450 accessories

  • GEM-450 automation software for full factory automation
  • SP-TXRF capability enables mapping of the entire wafer surface
  • ZEE-TXRF capability enables measurements to zero edge exclusion
  • BAC-TXRF capability enables fully-automated front-side and back-side measurements
  • Wafer bevel VPD capability
  • Dual VPD scanning solutions
  • Inserts for VPD droplet collection in vials

TXRF-V450 applications

  • VPD-integrated TXRF for trace element analysis of Na~U
    • Applicable as an in-line contamination monitor
    • Detection of transition metals at the 10⁷ atoms/cm² level is possible (500 sec measurement)
  • Determination of the contaminant element spatial distribution (wafer mapping)
    • Contamination distribution is seen at a glance by individual element maps and overlapping element views
    • Average contamination is calculated over the entire wafer surface
    • High-precision measurements can be carried out automatically on contaminated spots found by whole-wafer surface screening
  • For routine analysis on particular points: Direct-TXRF of designated coordinates
    • Correct contamination levels are reported at all points on a wafer by avoiding diffraction interference
    • Detection of transition metals at the 10⁹ atoms/ cm² level is possible (500 sec measurement)
    • Using a high-power rotating-anode X-ray source, three-times higher throughput is achieved compared with a sealed-tube source
    • Light elements, transition metals, and heavy elements are measured seamlessly without switching between multiple X-ray tubes

Fully-automated, high-sensitivity analysis in fab

  • 10⁸ atoms/cm² level of Ca analysis in the cleaning process
  • 10¹⁰ atoms/cm² level of Na and Al analysis in the cleaning process
  • 10⁸ atoms/cm² level of transition metal analysis in the diffusion process
  • 10⁸ atoms/cm² level of Ni contamination analysis in post-cleaning of oxidization

Entire surface mapping of 450mm wafer with high throughput

  • Entire surface mapping in LPCVD (10¹⁰ atoms/cm² level)
  • Entire surface mapping of contamination in ion implantation
  • Entire mapping in RIE process (10¹⁰ atoms/cm² level)
  • Entire mapping in transferred wafer of manufacturing tool (10¹⁰ atoms/cm²)
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