Michelangelo Delfino

X-ray photoemission spectra of reactively sputtered TiN

X‐ray photoemission spectra of reactively sputtered TiN1.0 films are recorded without interference from adsorbed contaminants or ion sputter cleaning damage. In this way, the transition from hcp TiN0.3 to fcc TiN1.0 is characterized by a discontinuity in film stoichiometry, Ti 2p splitting energy, and Ti 2p3/2 binding energy as a function of the Ar/N2 ratio during sputtering. The line shapes of the N 1s and 2s transitions experience only an asymmetric broadening on forming fcc TiN. The core‐level N 1s transition of fcc TiN is modeled as two components peaks with binding energies at 396.8 and 396.0 eV. Similarly, the valence band N 2s transition has corresponding component peaks at 16.8 and 16.2 eV. These high and low binding energy pairs are interpreted as on‐site Ns and interstitial site Ni populations of nitrogen in a fcc TiN lattice, respectively. The ratio of N/Ti is 1.0 and the Ns/Ni ratio is approximately 6. Both ratios are independent of the composition of the sputtering gas mixture and the substra...

Plasma cleaned Si analyzed in situ by x‐ray photoelectron spectroscopy, secondary ion mass spectrometry, and actinometry

Silicon surfaces are cleaned in an electron cyclotron resonance excited hydrogen plasma and characterized by in situ x‐ray photoelectron spectroscopy and in situ static secondary ion‐mass spectrometry. Emission spectroscopy and actinometry are used to characterize the hydrogen plasma. Exposure to the plasma for 3 to 4 minutes without applying heat or bias to the substrate completely removes the native silicon oxide resulting in a hydrogen terminated surface that is resistant to reoxidation. Adventitious hydrocarbon, when present on the surface, is also completely removed by the plasma. A shift in the isotope ratios of silicon suggests that a clean 〈100〉 silicon surface is monohydride terminated, whereas a 〈111〉 silicon surface appears largely dihydride terminated. A depth profile of the silicon isotope ratios shows a temporal instability, which with the assignment of a H 1s state in the valence‐band spectra provides evidence that the hydrogen is concentrated at the surface and has not diffused deep into t...

Correlation of electrical resistivity and grain size in sputtered titanium films

Abstract Thin Ti films deposited onto thermal SiO2 by sputtering in Ar or Ne are analyzed accounting for electron scattering at both film and grain boundary surfaces. An intrinsic resistivity of 54 and 63 μΩ cm, and an electron mean free path of 18 and 15 nm is derived for films sputter deposited in Ar and Ne, respectively. For both gases, a grain boundary reflection coefficient of 0.17 is calculated, assuming pure specular electron reflection at the film surfaces. Resistivity lowering is shown to correlate directly with an increase in grain size. Sputtering in Ar results in larger grain size films that have a small 21 μΩ cm residual resistivity and a high 2800 ppm temperature coefficient of resistance. The film grain size is independent of the deposition rate and reduced when sputtered in Ne, or in Ar and an applied negative substrate bias. The Ti film texture is found to be independent of film thickness and the presence of a collimator but sensitive to an applied substrate bias.

Temperature dependence of the electrical resistivity of reactively sputtered TiN films

The electrical resistivity of reactively sputtered TiN films was measured as a function of film thickness. The effect of directionality of the sputtered atoms, substrate temperature, bias voltage, deposition rate, and film morphology on the electron conductivity in TiN films was studied. The combination of rapid deposition rate and high substrate temperature with bias‐collimated sputtering results in TiN films with the lowest resistivity, 45 μΩ cm, the largest temperature coefficient of resistance, 1355 ppm, and the highest superconducting transition temperature, 5.04 K. These films are characterized by small grains with mixed <111≳ and <200≳ orientation and reduced electron scattering with an estimated electron mean‐free path of 96 nm.

Low energy ion etching of aluminum oxide films and native aluminum oxide

Aluminum oxide films were etched using low energy argon ions generated by a microwave electron cyclotron resonance (ECR) source argon plasma. The argon ion energies were controlled by biasing substrates placed on a 13.56 MHz capacitively coupled electrode. Reactively sputtered aluminum oxide films were used to study the relationship between the dc bias applied to these substrates and the etch rate of their films. In situ x‐ray photoemission spectra of the Al 2p and O 1s transitions showed that the ECR plasma was effective in completely removing native aluminum oxide and adventitious hydrocarbon in 1 min at ion energies as low as 100 eV. This preclean technology did not change the dielectric breakdown distribution of antenna structures with 12‐nm‐thick gate oxide capacitors.

X‐ray photoemission analysis and electrical contact properties of NF3 plasma cleaned Si surfaces

The removal of native silicon oxide on <100≳ silicon with an electron cyclotron resonance (ECR) excited NF3 plasma is demonstrated. In situ x‐ray photoemission spectroscopy verifies removal of the oxide and shows that a residue remains on the surface after exposure to the plasma. The residue is about 1.2 nm thick with the approximate formula Si6F8ON2 when analyzed with a uniform overlayer model. X‐ray photoemission spectra of the residue show fluorine and oxygen in at least two different bonding states and a unique nitrogen having a diamagnetic bond. Chemical bonding in the residue is ascribed to Fx‐Si, Fx‐Si‐O, Si‐O‐Si, and N2‐O‐Si species, where x=1, 2, and 3. A distinct high‐energy peak is identified in the quasicore level F 2s transition that is attributed to a small amount of interstitial fluorine having diffused into the silicon lattice. The residue is stable at room temperature in both vacuum and under hydrogen, but when exposed to room ambient, it and the substrate appear to oxidize accounting for...

Wavelength-specific pyrometry as a temperature measurement tool

A wavelength-specific 9.4+or-0.3- mu m pyrometer with a 0.41 constant emissivity was used to measure the temperature of 2 to 6 Omega -cm, n-type silicon coated with 1.3 mu m of thermal oxide from 270 degrees C to 600 degrees C with an accuracy of +or-1%. At lower temperatures, the emissivity monotonically decreases to 0.36 at 200 degrees C with a slope that is proportional to the thermally activated free-carrier absorption of the silicon. This dependency introduces. at any temperature, a temperature uncertainty that is proportional to the emissivity change divided by the constant emissivity. By comparison, the same accuracy inherent in constant emissivity measurements is limited to 430 degrees C when sensed with a more typical 11+or-3- mu m pyrometer. Furthermore, the emissivity change at 200 degrees C is three times larger, resulting in an equally large temperature uncertainty. A four-phase optical model with the constraint of substrate opacity is used to approximate the constant emissivity, as a function of the spectral bandwidth of the pyrometer. The greatest discrepancy between calculation and measurement is 0.14 emissivity or 24 degrees C at 430 degrees C. >

Thermal nitridation of silicon in a cluster tool

An integrated cluster tool process is described whereby stoichiometric Si3N4 films with less than 0.01 at % oxygen, hydrogen, and carbon are grown on 〈111〉 Si. The ultrahigh film purity is verified in situ with x‐ray photoelectron spectroscopy and static secondary ion‐mass spectrometry depth profiles. The two‐step process consists of cleaning the surface in an electron cyclotron resonance excited H2 plasma, and passing in vacuum to a second chamber where it is exposed to NH3 for 2 min at 1070 °C to promote nitridation. The films are approximately 5 nm thick with a refractive index of 2.01 at 633 nm. They are resistant to a dry O2 ambient for at least 6 h at 1050 °C. The average breakdown field of Al/Si3N4/Si capacitors is around 9 MV/cm.

Removal of fluorocarbon residue on Si with an electron cyclotron resonance excited Ar plasma

An electron cyclotron resonance‐excited Ar plasma completely removes CFx residue on Si resulting in a clean surface that is free of native Si oxide. In situ x‐ray photoelectron spectroscopy verifies the absence of C and F on the surface, and the presence of what is thought to be a small amount of adsorbed or interstitially implanted O. Mechanistically, the Ar ion bombardment affects a nearly instantaneous ablation of F from the CFx surface followed in succession by a low average energy (100 eV) sputtering of the C‐rich remnant, the native Si oxide, and the Si substrate. The etching rate of thick CFx residue is approximately 15 nm/min without any heat applied to the substrate.

Electron Cyclotron Resonance Plasma Etching of Native TiO2 on TiN

Thin-film polycrystalline Tin with an approximate 2 nm thick native TiO{sub 2} overlayer is bombarded with 50 to 200 eV Ar ions in an electron cyclotron resonance plasma. In situ X-ray photoelectron spectroscopy and static secondary ion mass spectrometry suggest complete removal of oxygen from the planar surface, independent of ion energy, with TiO{sub 2} remaining on the columnar grain boundaries. The TiN etching rate increases from 6 to 14 nm/min as the ion energy is raised from 100 to 200 eV. The TiN stoichiometry does not change with ion bombardment.