Low Energy X-ray Emission Spectrometry (LEXES)

Low Energy X-ray Emission Spectrometry (LEXES), is a near surface analytical technique that utilizes a high-energy electron beam as an excitation source. Atoms that are excited by the electron beam relax under the emission of characteristic x-rays. Similar to EDS, LEXES measures the energy of the emitted x-rays, which are characteristic of elements present in the near-surface region of a sample. The use of Wavelength Dispersive Spectrometers (WDS) increases the sensitivity of the technique as well is improves energy resolution, removing almost all 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 compared 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 10 Angstroms or as thick as 1um to be analyzed. Finally, the LEXES electron beam can be focused into an area as small as 10um, allowing small areas to be analyzed.

Main Applications

• High precision measurement and full wafer mapping of dopant dose, thin film composition, thickness, and impurities

Ideal Uses for LEXES Analysis		Relevant Industries
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		Compound Semiconductor Data Storage Defense Displays Electronics Photonics Semiconductor Solar Photovoltaics Telecommunication
Strengths of LEXES Analysis		Limitations of LEXES Analysis
Non-destructive Whole wafer analysis (200 and 300 mm) 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 sample thickness of ~2mm Can have problems with insulating samples

Application Notes