Scott K. Stanley

Core-Shell Germanium–Silicon Nanocrystal Floating Gate for Nonvolatile Memory Applications

We have fabricated germanium-silicon (Si/HfSiOx) core-shell nanocrystal (NC) structures to work as charge storage nodes in NC flash memories. This core shell NC structure was made by doing silane annealing treatment before and after Ge NC deposition. This silicon(Si/HfSiOx) shell layer can separate the Ge NC from HfO2 and ambient oxidants in the following process, and reduces low-quality GeOx, HfGeOx to metallic Ge. Thus, a more robust interface with low trap density between the high-kappa dielectric and the NCs was achieved, which helps suppress the charges loss due to trap-assisted tunneling of electrons and results in better device performance.

Ge interactions on HfO2 surfaces and kinetically driven patterning of Ge nanocrystals on HfO2

Germanium interactions are studied on HfO2 surfaces, which are prepared through physical vapor deposition (PVD) and by atomic layer deposition. X-ray photoelectron spectroscopy and temperature-programed desorption are used to follow the reactions of germanium on HfO2. Germanium chemical vapor deposition at 870 K on HfO2 produces a GeOx adhesion layer, followed by growth of semiconducting Ge0. PVD of 0.7 ML Ge (accomplished by thermally cracking GeH4 over a hot filament) also produces an initial GeOx layer, which is stable up to 800 K. PVD above 2.0 ML deposits semiconducting Ge0. Temperature programed desorption experiments of ∼1.0ML Ge from HfO2 at 400–1100 K show GeH4 desorption below 600 K and GeO desorption above 850 K. These results are compared to Ge on SiO2 where GeO desorption is seen at 550 K. Exploiting the different reactivity of Ge on HfO2 and SiO2 allows a kinetically driven patterning scheme for high-density Ge nanoparticle growth on HfO2 surfaces that is demonstrated.

Growth of high-density Si nanoparticles on Si3N4 and SiO2 thin films by hot-wire chemical vapor deposition

High-density (>1×1012 cm−2) Si nanoparticles have been successfully grown on Si3N4 and SiO2 thin films by hot-wire chemical vapor deposition (HW-CVD) using disilane, in which Si atoms are generated on a heated tungsten filament and, after desorbing, impinge on the substrate. The highest density, 1.1×1012 cm−2 as measured by scanning electron microscopy (SEM) and 2.1×1012 cm−2 by scanning tunneling microscopy, is achieved by depositing 1.8 monolayer Si on Si3N4 at 600 °C and a disilane pressure of 1.2×10−6 Torr. The corresponding Si nanoparticles have an average size of about 5 nm. Different densities are reported because scanning tunneling microscopy imaged Si nanoparticles of ∼4 nm, beyond the resolution of SEM. At temperatures above 600 °C, parallel thermal chemical vapor deposition (CVD) during HW-CVD becomes important. Parallel thermal CVD broadens the size distribution of Si nanoparticles and causes coalescence of neighboring nanoparticles, leading to a decrease of nanoparticle density. High densitie...

Directed nucleation of ordered nanoparticle arrays on amorphous surfaces

Germanium nanoparticle nucleation was studied in organized arrays on HfO2 using a SiO2 thin film mask with ∼20–24nm pores and a 6×1010cm−2 pore density. Poly(styrene-b-methyl methacrylate) diblock copolymer was employed to pattern the SiO2 film. Hot wire chemical vapor deposition at 800K produced Ge nanoparticles using 6–19 monolayer Ge exposures. By seeding adatoms on HfO2 at room temperature before growth, nanoparticle density is approximately one particle per pore.

Core-shell germanium-silicon nanoparticle structure for high κ nonvolatile memory applications

This paper presents a new germanium-silicon core-shell nanoparticle structure for nonvolatile memory applications. This core-shell can help to passivate Ge dots from oxidation, create more favorable interface between nanoparticle and high K dielectric materials and improve device performance.