X-ray diffraction (XRD) characterization methods for sigma=3 twin defects in cubic semiconductor (100) wafers
Inventors
Park, Yeonjoon • Kim, Hyun Jung • SKUZA, Jonathan R. • Lee, Kunik • King, Glen C. • Choi, Sang Hyouk
Assignees
National Aeronautics and Space Administration NASA
Publication Number
US-9835570-B2
Publication Date
2017-12-05
Expiration Date
2034-09-12
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Abstract
An X-ray defraction (XRD) characterization method for sigma=3 twin defects in cubic semiconductor (100) wafers includes a concentration measurement method and a wafer mapping method for any cubic tetrahedral semiconductor wafers including GaAs (100) wafers and Si (100) wafers. The methods use the cubic semiconductor's (004) pole figure in order to detect sigma=3/{111} twin defects. The XRD methods are applicable to any (100) wafers of tetrahedral cubic semiconductors in the diamond structure (Si, Ge, C) and cubic zinc-blend structure (InP, InGaAs, CdTe, ZnSe, and so on) with various growth methods such as Liquid Encapsulated Czochralski (LEC) growth, Molecular Beam Epitaxy (MBE), Organometallic Vapor Phase Epitaxy (OMVPE), Czochralski growth and Metal Organic Chemical Vapor Deposition (MOCVD) growth.
Core Innovation
The invention comprises non-destructive X-ray diffraction (XRD) characterization methods for detecting and measuring sigma=3/{111} twin defects in cubic semiconductor (100) wafers. The methods include a concentration measurement process that provides a quality factor ratio quantitatively describing the concentration of these twin defects, and a wafer mapping process that spatially maps the defects within the wafer. These methods utilize the cubic semiconductor's (004) pole figure to detect sigma=3/{111} twin defects across various materials including GaAs (100) and Si (100) wafers.
The problem addressed by the invention arises from the presence of sigma=3 twin defects on {111} planes, common crystal structure defects in cubic semiconductors which can adversely affect the performance of electronic devices. Existing defect measurement techniques such as transmission electron microscopy (TEM) or etch-pit density test are destructive and render wafers unusable after testing. Hence, there is a need for non-destructive characterization methods that can be applied at wafer scale and integrated into commercial wafer fabrication processes for real-time quality control.
The methods according to the invention are applicable broadly to cubic tetrahedral semiconductor wafers with diamond structures (e.g., Si, Ge, C) and cubic zinc-blende structures (e.g., InP, InGaAs, CdTe, ZnSe), grown by various methods such as Liquid Encapsulated Czochralski (LEC) growth, Molecular Beam Epitaxy (MBE), Organometallic Vapor Phase Epitaxy (OMVPE), Czochralski growth, and Metal Organic Chemical Vapor Deposition (MOCVD). The invention provides a quality factor derived from the intensity ratio between sigma=3/{111} twin defect peaks and the original cubic crystal's (004) peak, independent of instrumental parameters and suitable for process feedback to reduce defects.
Claims Coverage
The patent includes two independent claims covering main inventive features related to characterization and mapping of sigma=3 twin defects using XRD methods.
Quality factor determination for sigma=3 twin defects
A method of characterizing sigma=3 twin defects by measuring magnitude of the (004) intensity peak and at least one twin defect intensity peak using XRD, and determining a quality factor ratio by dividing the twin defect intensity peak magnitude by the (004) peak magnitude.
XRD mapping of sigma=3/{111} twin defects on semiconductor (100) specimens
A method for mapping the twin defects involving determining a tilt angle at which twin defect peaks occur, aligning detector and sample angles accordingly, moving the specimen in a plane relative to the detector, measuring diffracted beam intensity corresponding to defect density, and forming a map showing the spatial distribution of twin defect intensity.
The claims cover inventive features providing quantitative measurement of sigma=3 twin defects via a quality factor ratio from XRD intensity data and spatial mapping of twin defects on (100) wafers using aligned XRD scanning for defect density distribution visualization.
Stated Advantages
The methods are non-destructive, enabling preservation of wafer integrity during defect measurement.
The quality factor ratio is independent of X-ray intensity, slit size, and detector sensitivity, providing consistent wafer quality evaluation.
The methods provide rapid, quantitative pass/fail testing suitable for integration in commercial wafer fabrication for real-time process control.
Wafer mapping enables visualization of spatial distribution and propagation of twin defects within wafers and ingots, aiding in process optimization to reduce defect density.
Documented Applications
Characterization of sigma=3/{111} twin defects in monocrystalline GaAs (100) wafers grown by Vertical Gradient Freeze (VGF) process.
Detection and mapping of sigma=3/{111} twin defects in Silicon (100) wafers fabricated by the Czochralski growth method.
Application to various cubic tetrahedral semiconductor (100) wafers including materials in diamond and cubic zinc-blende crystal structures.
Use in commercial wafer fabrication processes for quality control and process feedback to reduce defect formation during semiconductor wafer production.
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