SIMS-22 International Conference presentations

PCOR-SIMS^SM Analyses of Compound Semiconductors, T. Buyuklimanli

Demand for compound semiconductors (especially III-V materials) has rapidly grown in recent years due to needs for faster transistors with more power, as well as the increased use of lasers in optical networking and sensors. These epitaxially grown materials are almost always complex in layer structure, with varying alloy composition and thin dopant layers. For device performance quality checks, it is essential to have low detection limits for impurities, correct dopant distribution determination and highly accurate concentration calibration. Dopant layer thickness, especially across varying matrix composition, is often also measured by SIMS. However, these needs are challenged by “matrix effects” in these complex multi-layered structures. Therefore, a SIMS method which minimizes these artifacts is important for obtaining reliable results throughout the structure of interest. PCOR-SIMSSM is a point-by-point data correction algorithm, which uses the alloy composition at a given data point for proper calibration of SIMS intensities. This minimizes matrix effects therefore, layer thicknesses and elemental concentrations, most importantly across graded compositions, are determined with much less scope for error.

Current HEMT and VCSEL devices have dopants and layers which are <10nm thick. Therefore, the depth resolution of the SIMS profile has to be sufficient to detect small variations in these layers. With the use of low primary ion beam energy, layers as thin as 1nm can be successfully analyzed to study small changes in growth conditions.