Bismuth incorporation and lattice contraction in GaSbBi and InSbBi
III–V-Bi compounds have received considerable attention recently due to a number of interesting material properties. For example, adding a small amount of Bi atoms in conventional III–Vs leads to a large bandgap reduction that occurs predominately in the valence band, about 88 meV/%Bi in GaAsBi. The Bi incorporation affects only the valence band structures and has little influence on electrons. Compared with dilute nitrides, the electron mobility of dilute GaAsBi is much less affected and photoluminescence intensity increases with the Bi incorporation. Dilute GaAsBi also introduces a large spin-orbit split and it has been suggested to use this property to suppress Auger recombination for 1.55 µm lasers on GaAs [1]. So far most experimental studies have been focused on growth of GaAsBi [2], but very little on GaSbBi and InSbBi. Here we report growth of dilute GaSbBi and InSbBi using molecular beam epitaxy (MBE). We have optimized growth conditions aiming at achieving maximum Bi incorporation. Surprisingly X-ray diffraction (XRD) revealed lattice contraction in GaSbBi and InSbBi although Bi atoms have a large atomic radius.
X-Ray Diffraction Measurements on Lattice Mismatch of InTlAs Grown on InAs Substrates
InTlAs layers were grown by molecular-beam epitaxy on InAs(001) substrates, and their lattice mismatch to the substrate was characterized by X-ray diffraction measurements. In each X-ray rocking curve, a distinct peak of InTlAs was observed at a higher diffraction angle than the substrate peak, indicating a smaller lattice constant of InTlAs than InAs. The lattice mismatch, δ=(aepi-asub)/asub, was estimated to be -0.08% for a sample whose thallium composition x of In1-xTlxAs was determined to be 0.12(±0.02)% by Rutherford backscattering spectrometry.
Bevel RIE application to reduce defectivity in copper BEOL processing
Bevel etch used during wafer fabrication for semiconductor devices is discussed. In this case, the bevel etch process was utilized in middle of the line processing (MOL) to reduce back end of line (BEOL) defectivity. Tungsten and titanium nitride films, from the formation of contacts to the transistors, extend into the bevel region of the wafer and have been shown to initiate arcing. This can spread foreign material defects on the front side of the wafer in various BEOL post processing steps including subsequent reactive ion etching, SEM metrology and film depositions. The bevel etch tool confines a plasma etch to the outer edge of the front side of the wafer (which can be individually adjusted) and can remove dielectric, organic and Ti/TiN/W films using a fluorine based chemistry.