Jeffrey Klatt

Two-dimensional lattice-mismatched heteroepitaxy of germanium on silicon beyond the critical thickness by introducing a surfactant

Smooth germanium films have been grown on Si(100) surfaces in a two‐dimensional fashion by using antimony as a surfactant. Different ways of depositing the surfactant (at the interface between substrate and growing film, after the deposition of a thin Ge layer, and by coevaporation) have been investigated. The grown films, investigated by high‐resolution electron microscopy and reflection high‐energy electron diffraction, show that the surfactant does not act at the interface. A kinetical approach for the description of surfactant behavior in the growing front is necessary.

Suppressing of island formation in surfactant‐controlled solid phase epitaxy of germanium on Si(100)

Smooth epitaxial 10 and 30 nm germanium layers have been grown on Si(100) by surfactant‐controlled solid phase epitaxy. The layers were characterized by reflection high energy electron diffraction, transmission electron microscopy, and x‐ray photoelectron spectroscopy. By depositing one monolayer antimony on top of the amorphous germanium layer it was possible to crystallize the germanium directly into a smooth epitaxial structure without any island formation. The obtained low‐defect layers are relaxed.

Surfactant-mediated growth of germanium on Si(100) by MBE and SPE

Abstract Germanium layers of 10 and 30 nm thickness have been grown on Si(100) with and without antimony as a surfactant by molecular beam epitaxy (MBE) and solid phase epitaxy (SPE) and investigated in situ by RHEED and XPS and ex situ by TEM and XRD. Without a surfactant germanium growth proceed in a typical Stranski-Krastanov mode. The system is minimizing its built-in strain energy by undergoing strain relaxation through a clustering mechanism (islanding). In all surfactant-mediated growth processes it was possible to obtain smooth layers without island formation. The influence of different ways for introducing the surfactant layer (at the interface between substrate and growing film, in the growing film below or above the critical Stranski-Krastanov thickness, or on top of the grown Ge film) will be presented. Especially in surfactant-controlled SPE, the smooth epitaxial germanium layer was obtained by passing through an island formation stage. These islands formed below 400°C are of different structure than the ones formed without a surfactant. Possible mechanism for the “smoothing out” of islands developed in the beginning stage of surfactant-controlled SPE will be discussed. The island formation stage can be completely suppressed by depositing the surfactant on top of the amorphous Ge layer before increasing the temperature.

Van der Waals epitaxy of thick Sb, Ge, and Ge/Sb films on mica

We attempt to grow 20‐nm‐thick layers of Sb and Ge as well as periods of (20 nm Sb/20 nm Ge) layers on muscovite (a special form of mica) by van der Waals epitaxy under different growth conditions. The growth process was in situ investigated by reflection high‐energy electron diffraction and Auger electron spectroscopy. Epitaxial Sb layers could be obtained even at cold substrates (mica or polycrystalline Ge layers). It was not possible to grow monocrystalline Ge layers by van der Waals epitaxy. Only a formation of oriented Ge grains could be observed at higher temperatures.

Boron‐controlled solid phase epitaxy of germanium on silicon: A new nonsegregating surfactant

10‐nm‐thick germanium layers have been grown on Si(100) with boron as a surfactant with three different growth procedures, and investigated with reflection high‐energy electron diffraction, transmission electron microscopy, and secondary ion mass spectroscopy. We obtained smooth and completely closed epitaxial germanium layers only by depositing the boron on top of the amorphous germanium layer followed by a post‐annealing step. The surface energy anisotropy of the germanium will be affected by the presence of boron in this equilibrium process. The islanding observed in all other growth processes can be understood by taking into account that boron is a typical nonsegregating material in Ge below 600 °C and a surfactant acts mainly due to its presence in the growing front.

Developing a High Volume Manufacturing Wet Clean Process to Remove BF2 Implant Induced Molybdenum Contamination

This work details the investigation of potential problems in Complimentary BiCMOS technology, especially PNP transistors arrays. Optical examination of the wafer revealed defects in the P Buried Layer (PBL) areas of the die. Electrical testing correlated these PBL defects to PNP array current leakage. As the PBL module is completed very early on in the process, we devised a shortloop (SL) to reproduce these defects and identify the root cause of current leakage.

Developing a high volume manufacturing method to eliminate P Buried Layer implant defects

Atomic Force Microscopy, Deep Level Transient Spectroscopy and Secondary Ion Mass Spectroscopy were used to study defects created in the P Buried Layer while using a BF2 implant. The P Buried Layer defects were traced to the unintentional co-implantation of Mo along with the BF2 implant. Using a Tungsten source, instead of a Molybdenum source for the BF2 implant, reduced but did not eliminate these defects. A novel, high volume processing method was developed to produce metal contamination-free buried layers and verified by deep level transient spectroscopy spectra.