The chemical structure of the SiO2/Si interface as determined by high resolution XPS - Suboxide distributions and the formation of electrically active interface states
Explore the source record for details and available documents.
Grunthaner, F. J.↗
Engineering topics
Hecht, M. H.
Publications and source records attributed to Hecht, M. H..
Soft X-ray photoemission with the SSX-100 spectrometer
Photoemission and SEXAFS experiments were conducted using a double crystal monochromator at the Stanford Synchrotron Radiation Laboratory. Photoelectrons were detected using a Surface Science Laboratories SSX-100 electron analyzer, which employs a magnetic/electrostatic lens, hemispherical geometry, and a two-dimensional position-sensitive detector. In the kinetic energy range of interest (1000-2000 eV), a significant improvement in count rate was observed over a single channel cylindrical mirror analyzer system. Ten second scans of the KLL silicon Auger peak manifold were recorded at a large number of photon energies for subsequent determination of SEXAFS spectra.
Hecht, M. H.↗
A novel X-ray photoelectron spectroscopy study of the Al/SiO2 interface
The nondestructive measurement of the chemical and physical characteristics of the interface between bulk SiO2 and thick aluminum films is reported. Both X-ray phototelectron spectroscopy (XPS) and electrical measurements of unannealed, resistively evaporated Al films on thermal SiO2 indicate an atomically abrupt interface. Post metallization annealing at 450 C induces reduction of the SiO2 by the aluminum, at a rate consistent with the bulk reaction rate. The XPS measurement is performed from the SiO2 side after the removal of the Si substrate with XeF2 gas and thinning of the SiO2 layer with HF:ETOH. This represents a powerful new approach to the study of metal-insulator and related interfaces.
Hecht, M. H.↗
Studies of the Si/SiO2 interface using synchrotron radiation
Synchrotron radiation photoemission spectroscopy (SRPS) in the 1-4 KeV photon energy range is a useful tool for interface characterization. Results are presented of a series of studies of the near-interface region of Si/SiO2 which confirm that a bond strain gradient exists in the oxide as a result of lattice mismatch. These experiments include measurement of photoemission lineshape changes as a function of photon energy, corresponding changes in the electron escape depth near the interface, and surface extended X-ray absorption fine structure (SEXAFS) measurements directly indicating the shortening of the Si-Si second nearest neighbor distance in the near-interface region of the oxide.
Hecht, M. H.↗
Electron escape depth variation in thin SiO2 films measured with variable photon energy
A double crystal monochromator at the Stanford Synchrotron Radiation Laboratory is used to study the Si/SiO2 interface, using photon energies of hv = 1950-3700 eV. This photon energy range allows interfaces to be observed through oxide layers 50 A thick or more. Variations in electron escape depth and/or oxide density as a function of distance from the interface are observed over the entire kinetic energy range (100-3600 eV). These differences are attributed to a strained oxide layer near the interface.
Hecht, M. H.↗
X-ray photoelectron spectroscopy study of the chemical structure of thermally nitrided SiO2
X-ray photoelectron spectroscopy has been used to study the composition of 100-A thermally grown SiO2 films that have been thermally nitrided in ammonia. The SiO(x)N(y)/Si interface was studied both by chemical depth profiling of the oxynitride and by removal of the Si substrate with XeF2. It is found that N is distributed throughout the film, but with the concentration higher at the surface and in a region centered 25 A from the film/substrate interface. The interface region itself is found to be oxygen-rich relative to the rest of the film. Possible models which can explain these results are discussed.
Vasquez, R. P.↗
XPS study of the Al/SiO2 interface viewed from the SiO2 side
The first nondestructive measurement of the chemical and physical characteristics of the interface between bulk SiO2 and thick aluminum films is presented. Both X-ray photoelectron spectroscopy (XPS) and electrical measurements of unannealed resistively evaporated Al films on thermal SiO2 indicate an atomically abrupt interface. Postmetallization annealing (PMA) at 450 C induces reduction of the SiO2 by the aluminum, resulting in the layer ordering SiO2/Al2O3/Si/Al. The XPS measurement is performed from the SiO2 side after removal of the Si substrate after etching with XeF2 gas and thinning of the SiO2 layer with HF:ETOH. This represents a powerful new approach to the study of metal-insulator and other interfaces.
Hecht, M. H.↗
Surface sensitive photoemission EXAFS: A new structural tool
A new technique for surface EXAFS has been developed. In this technique the absorption fine structure is observed by monitoring the photoelectrons emitted from core levels as a function of photon energy. The surface sensitivity is achieved by detecting elastic photoelectrons that escape to the vacuum from a few atomic layers near the surface. EXAFS from Mn 3p and F2s outer core levels in MnF2 were measured, the results were compared with transmission EXAFS from Mn ls core level and good agreement was found. This development is significant because: (1) almost all elements have suitable core levels of low binding energy; (2) since photopeaks from adjacent core levels do not cross as the photon energy is varied, the limitations imposed on other surface EXAFS techniques by this interference is removed. Auger electrons, which have fixed kinetic energies and so can cross photopeaks, will generally have low energies if they originate from outer core levels and be unlikely to appear in the EXAFS region of kinetic energies, i.e., in excess of about 50 eV; (3) VUV light is used, which greatly extends the usable range of photon energies; (4) more than one element in a solid may be studied with the same monochromator. The experiments were carried out on the VUV beam line U14A at NSLS.
Choudhary, K. M.↗