Kenneth C. Cadien

Reactive ion etching of SiC thin films using fluorinated gases

Reactive ion etching (RIE) using fluorinated gases, such as admixtures of CF4 with O2, has been conducted on sputter deposited films of SiC. For comparison purposes, the same experiments with SiO2 films and Si wafers have been conducted. The influence of rf power, pressure, and O2 concentration on etch rate in CF4+O2, SF6+He, and Ar gases has been investigated. RIE mechanisms were studied using in situ monitoring of excited fluorine emission intensity and dc self‐bias at the lower electrode. Typical etch rates of Si, SiO2, and SiC are 1220, 600, and 375 A/min in CF4+4% O2; 8850, 500, and 560 A/min in SF6+50% He; and 340, 280, and 270 A/min in Ar, respectively, at P=200 W, p=20 mTorr, and 300 K. Under these conditions the dc self‐bias levels are −396 V for CF4+4% O2, −350 V for SF6+50% He, and −414 V for Ar. In both CF4+4% O2 and SF6+50% He, the etch rates of Si, SiO2, and SiC all increase monotonically with the rf power. However, with increasing pressure the Si etch rate increases while the etch rates of ...

Growth of single‐crystal metastable semiconducting (GaSb)1−xGex films

Epitaxial metastable (GaSb)1−xGex alloys with compostions across the pseudobinary phase diagram have been grown on (100) GaAs substrates by multitarget rf sputtering. An essential feature allowing the growth of these metastable materials was low‐energy ion bombardment of the growing film during deposition to enhance surface diffusion, promote mixing, and preferentially sputter incipient second‐phase precipitates. Annealing experiments indicated that the metastable films exhibit good high‐temperature stability and that they transform through a continuous series of GaSb‐rich and Ge‐rich phases in which the solute concentrations decrease until the equilibrium two‐phase alloy is obtained. While the calculated free‐energy difference between the single‐phase metastable and equilibrium states is ∼18 meV, the measured activation barrier for the transformation is ∼3 eV. All films were p‐type with room‐temperature hole concentrations varying from 1016 to 1019 cm−3 and mobilities between 10 and 720 cm2/ V s, dependi...

An overview of corrosion - wear interaction for planarizing metallic thin films

Corrosion-wear interactions play a very crucial role in developing many technological processes. One of them is chemical-mechanical planarization (CMP) of metallic thin films for manufacturing semiconductor devices such as computer chips. In this paper, we present research approaches undertaken in developing CMP for different metallic thin films, such as tungsten and copper in aqueous media. Mechanisms of material removal during CMP are presented. The role of corrosion, wear, and their synergistic effect are explained. The importance of constructing corrosion-wear maps for these complicated tribo-corrosion-metallic thin film systems is addressed. The application of corrosion-wear maps in developing reliable CMP slurries and processes is discussed.

Growth of high quality epitaxial Ge films on (100)Si by sputter deposition

Expitaxial Ge films ∼1.5 μm thick, were grown on (100) Si substrates at relatively low temperatures, 470°C, by rf sputter deposition. Low‐energy ion bombardment of the substrate and growing film during deposition provided compositional grading of the lattice mismatched interface. X‐ray diffraction and electron channeling spectra indicated that the films were single crystals while Hall measurements showed them to be p type with p(300 K)≃1×1017 cm−3 and corresponding carrier mobilities, 1280 cm2/Vs, comparable to the best bulk crystals. The thickness of the compositionally graded junction was found by Auger electron spectroscopy depth profiling to be ∼200 nm. C‐V measurements indicated that over this region the net acceptor concentration increased from 4×1014 cm−3 near the substrate surface to the bulk film value of 1×1017 cm−3. Large area p‐n diodes exhibited reverse breakdown voltages of ⩾10 V.

Growth of single crystal GaAs and metastable (GaSb)1−xGexAlloys by sputter deposition: Ion-surface interaction effects

Abstract High quality single crystal GaAs films and metastable (GaSb) 1- x Ge x alloys have been grown on (100) GaAs substrates by sputter deposition. Low energy ion bombardment of the growing films was used to control elemental incorporation probabilities and hence doping concentrations in the case of the GaAs films and was an essential feature in allowing the growth of the metastable alloys. The results in both cases are discussed in terms of the operative mechanisms including trapping processes, preferential sputtering, surface segregation, and collisional mixing. Unintentionally doped GaAs films were high resistivity 10 5 -10 6 Ω cm n-type with room temperature mobilities as high as 5000 cm 2 /V·s. Multitarget rf sputtering was used to grow epitaxial metastable p-type (GaSb) 1- x Ge x alloys with compositions across the pseudobinary phase diagram. The maximum growth temperature ranged from 490 to 520°C depending on the alloy composition and annealing experiments indicated that the films exhibit good high temperature stability. While the free energy difference between the single phase metastable and the two phase equilibrium states is on the order of 20 meV/atom, the measured activation barrier for the transformation is ≈3 eV.

A method for eliminating hillocks in integrated‐circuit metallizations

In a novel method for eliminating hillocks in integrated‐circuit metallizations, a sandwich layer is grown between the Al film and the underlying SiO2. This layer must have a thermal expansion coefficient between those of SiO2 and Al. The technique is demonstrated with WSi2 as the sandwich layer.

Growth mechanism of atomic layer deposition of zinc oxide: A density functional theory approach

Atomic layer deposition of zinc oxide (ZnO) using diethylzinc (DEZ) and water is studied using density functional theory. The reaction pathways between the precursors and ZnO surface sites are discussed. Both reactions proceed by the formation of intermediate complexes on the surface. The Gibbs free energy of the formation of these complexes is positive at temperatures above ∼120 °C and ∼200 °C for DEZ and water half-reactions, respectively. Spectroscopic ellipsometry results show that the growth per cycle changes at approximately the same temperatures.

GaSb-Ge pseudobinary phase diagram

The GaSb-Ge pseudobinary phase diagram has been determined by differential thermal analysis and confirmed by X-ray diffraction. The system is a simple eutectic with an invarient point at 41 ± 2 mole % Ge and 650 ± 5°C. The maximum solid solubilities of Ge in GaSb and GaSb in Ge are 2 ± 0.5 mole % and 6.5 ± 0.5 mole %, respectively, at the eutectic temperature.

Surface plasmon polarization filtering in a single mode dielectric waveguide

We demonstrate that metallic electrodes symmetrically placed about a single mode dielectric waveguide can effectively polarize the mode by excitation of surface plasmons. The transmission through the metal electrode waveguide structure is examined as a function of mode polarization and electrode spacing. It is found that modes polarized perpendicular to the metal surface can resonantly excite surface plasmons, extinguishing the mode in the waveguide core, while modes polarized parallel to metal surface only suffer mode attenuation due to the presence of the metal. The phase matching conditions for excitation of surface plasmons are examined and the polarization and insertion loss of the transmitted mode is experimentally verified.

Challenges for on-chip optical interconnects

As integrated circuit interconnect dimensions continue to shrink and signaling frequencies increase, interconnect performance degrades. The performance degradation is due to several factors such as power consumption, cross-talk, and signal attenuation. On-chip optical interconnects are a potential solution to these scaling issues because they offer the promise of providing higher bandwidth. In this paper, progress on the major on-chip optical building blocks will be reviewed. It will be shown that significant advances have been made in the design and fabrication of waveguides, detectors, and couplers. However, major challenges in high speed electrical to optical conversion and signaling remain.