M09100 - SEMI M91 - Test Method for Determination of Threading Screw Dislocation Density in 4H-SIC by X-Ray Topography

Threading screw dislocations (TSDs) are detrimental to several types of electronic devices manufactured from 4H-SiC.Most TSDs are transferred from a substrate into an epitaxial layer and may cause pits in the epi layer, which can be problematic for certain processing steps.The density and distribution of TSDs is a critical parameter for evaluating the wafer quality and for failure analysis of errant device structures. X-ray topography (XRT) is able to accomplish this task. This Test Method provides information on the measurement procedure and can be used for acceptance testing.This Test Method covers the determination of TSD density on round test slices and commercial 4H-SiC wafers using XRT for identification and registration of TSDs.The TSD density is used as a measure for the crystallographic perfection of a crystal.This Test Method describes the requirements of the sample quality and the procedure to obtain a topogram suitable for TSD identification.This Test Method is applicable to material with TSD densities up to 5000 cm−2. The resistivity, conductivity type and polarity of the analyzed side of the material is irrelevant.Referenced SEMI Standards (purchase separately)SEMI M20 — Practice for Establishing a Wafer Coordinate SystemSEMI M52 — Guide for Specifying Scanning Surface Inspection Systems for Silicon Wafers for the 130 nm to 11 nm Technology GenerationsSEMI M55 — Specification for Polished Monocrystalline Silicon Carbide WafersSEMI M59 — Terminology for Silicon TechnologyRevision HistorySEMI M91-0622 (first published)