Low Energy X-ray Emission Spectrometry, LEXES Analysis

Low Energy X-ray Emission Spectrometry (LEXES), is a near surface analytical technique that utilizes a low energy electron beam as an excitation source. Atoms that are excited by the electron beam relax under the emission of characteristic x-rays. Similarly to EDS, LEXES analysis measures the energy of the emitted x-rays, which are characteristic of Low Energy X-ray Emission Spectrometry, LEXESelements present in the near-surface region of a sample. The use of Wavelength Dispersive Spectrometers (WDS) increases the sensitivity of the technique and improves energy resolution, removing most interferences.

The electron beam current can be very tightly controlled, allowing for very high precision measurements. Dopant concentrations, film composition, and/or film thickness can be mapped across wafers or LEXES Analysis, Low Energy X-ray Emission Spectrometrycompared between wafers with precisions of 1% or better. By using reference standards measurement accuracies of better than 5% can be obtained. Adjusting the energy of the incident electron beam allows layers as thin as 10Å or as thick as 1µm to be analyzed. Finally, the LEXES electron beam can be focused into an area as small as 10µm, allowing small areas to be analyzed.

Main Applications

  • High precision measurement and full wafer mapping of dopant dose, thin film composition, thickness, and impurities
  • High precision ion implant dose measurement for tool or process matching
  • Measuring ion implant uniformity across wafers
  • Determining thin film composition
  • Measuring film uniformity across wafers
  • Measuring impurity levels in thin films

Signal Detected: Characteristic x-rays

Elements Detected: B-U

Detection Limits: 5e13 atoms/cm2, 0.01at%

Depth Resolution: N/A, no depth profile generated

Imaging/Mapping: Yes

Ultimate Lateral Resolution: ~10µm

  • Non-destructive
    • Whole wafer analysis (up to 300mm) as well as wafer pieces and small samples
    • Mapping of full wafers
  • Measurement precision typically <1%
  • Measurement accuracy typically <5%
  • No sample preparation requirements
  • Can analyze areas as small as 30µm
  • Maximum analysis depth of ~1µm
  • Maximum total sample thickness of ~2mm
  • Can have problems with insulating samples
  • Compound Semiconductor
  • Data Storage
  • Defense
  • Displays
  • Electronics
  • Photonics
  • Semiconductor
  • Photovoltaics
  • Telecommunication
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