K. N. Ritz

Interactions of thin Ti films with Si, SiO2, Si3N4, and SiOxNy under rapid thermal annealing

Thin Ti films sputter deposited onto single‐crystal Si, thermal SiO2, and low‐pressure chemical vapor deposited Si3N4 and SiOxNy (x≊y≊1) substrates have been rapid thermal annealed in N2 or Ar, with and without an amorphous Si overlayer, and the reactions followed using Auger elecron spectroscopy, transmission electron microscopy, electron diffraction, and sheet resistance measurements. A multilayer film is created in practically every case with each layer containing essentially a single reaction product, viz.,TiSix, TiOx, δ‐TiN, or TiNxO1−x. The results are discussed in light of published Ti‐Si‐O and Ti‐Si‐N phase diagrams.

Study of reactive‐ion‐etch‐induced lattice damage in silicon by Ar, CF4, NF3, and CHF3 plasmas

Reactive‐ion‐etch‐induced damage in silicon has been investigated using transmission electron microscopy (TEM), Rutherford backscattering (RBS) ion channeling, and laser‐induced thermal waves (TW). A correlation has been found between lattice damage in silicon due to reactive ion etching and leakage current properties of thermal oxide films subsequently grown on the damaged silicon. The silicon wafers were plasma etched using Ar, CF4, NF3, and CHF3 etch gases at dc bias voltages ranging from 150 V to 450 V. Lattice damage at the silicon surface, as determined by TEM and RBS, was found to depend on both the dc bias voltage and the etch chemistry. Subsequent leakage current measurements of the silicon oxides show that the samples with more silicon substrate lattice damage prior to oxidation also have correspondingly higher leakage. The thermal wave technique also indicates a damage dependence on dc bias and on etch chemistry; however, the thermal wave measurements indicate a damage dependence on etch chemistry different from TEM and RBS measurements. The source of this difference is not yet understood.

Effects of high carbon concentration upon oxygen precipitation and related phenomena in CzSi

Effects of high carbon concentration upon oxygen precipitation and related phenomena in Czochralski (Cz) silicon have been investigated by combining various furnace and rapid thermal anneals. Our data show that oxide precipitate (OP) density, estimated from changes in interstitial oxygen concentration (ΔOi), increases with increasing substitutional carbon concentration, Cs, while thermal donor (TD) formation is inhibited at high Cs. Even though ΔOi increases monotonically with Cs, synchrotron radiation section topographs of processed high carbon content wafers (Cs∼4 ppma) exhibit Pendellosung fringes, indicating a strain‐free bulk state. Our transmission electron microscope and optical microscopic data also show very few resolvable structural defects associated with precipitates inside the bulk Si. Using a thermodynamic and kinetic model, we attempt to explain: (1) reduced thermal donor formation, (2) lack of bulk stress notwithstanding high ΔOi, and (3) predominantly polyhedral precipitate morphologies i...

Formation and high‐temperature stability of CoSix films on an SiO2 substrate

A thin α‐Co layer with an amorphous Si underlayer has been sputter deposited onto a thermal SiO2 substrate, rapid thermal annealed in N2 at 700–1050 °C, and the phases formed examined using Auger electron spectroscopy, transmission electron microscopy, electron diffraction, and sheet resistance measurements. A CoSix film results where x is constant with depth and determined by the relative amounts of Co and Si deposited. With increasing x, phases identified are α‐ and β‐Co containing dissolved Si, Co2Si, CoSi, and CoSi2. At high temperatures, the CoSi2 film agglomerates and thins the underlying oxide probably on account of excess Si in the silicide film. Furthermore, in an N2 atmosphere, the CoSi2 globules are converted into CoSi in accordance with the phase diagram.

Observation of slip dislocations in (100) silicon wafers after BF2 ion implantation and rapid thermal annealing

The generation of slip dislocations in BF2 ion‐implanted, 100‐mm‐diam silicon wafers during rapid thermal annealing is investigated. Whole wafer x‐ray topography shows that annealing at 1150 °C causes slip to initiate randomly at positions of maximum resolved stress at the wafer edges and over scribe marks made on the back surface prior to annealing. Lowering the annealing temperature by 20 °C, which corresponds to decreasing the silicon yield stress by less than 106 dyn cm−2, prevents slip from occurring and allows sufficient removal of implantation‐induced defects from which junction diodes with good current‐voltage characteristics are fabricated.

Effects of Carbon Concentration Upon Oxygen Precipitation in Cz Si

Effects of high carbon concentration upon oxygen precipitate formation in Cz silicon have been investigated by combining various furnace and rapid thermal anneals. Even though oxide precipitate density increases with increasing carbon levels, C/sub s/, synchrotron radiation section topographs of processed high carbon content wafers (C/sub s/ approx.4ppMa) exhibit Pendellosung fringes, indicating a strain free bulk state. Our optical microscopic data have also shown very few defect etch features inside the bulk. A model based upon a direct coupling of both SiO/sub 2/ and Si-C complex formation reactions is used to explain rather unique oxygen precipitation characteristics in the high carbon content Cz Si materials. 5 refs., 1 fig., 1 tab.