Dan O'Connell

Impact of Forming Gas Annealing on the Performance of Surface-Channel

We investigated the effect of forming gas (5% H₂/95% N₂) annealing on surface-channel In_0.53 Ga_0.47As MOSFETs with atomic-layer-deposited Al₂O₃ as the gate dielectric. We found that a forming gas anneal (FGA) at 300°C for 30 min was efficient at removing or passivating positive fixed charges in Al₂O₃ , resulting in a shift of the threshold voltage from -0.63 to 0.43 V and in an increase in the <i>I</i>_on/<i>I</i>_off ratio of three orders of magnitude. Following FGA, the MOSFETs exhibited a subthreshold swing of 150 mV/dec, and the peak transconductance, drive current, and peak effective mobility increased by 29%, 25%, and 15%, respectively. FGA significantly improved the source- or drain-to-substrate junction isolation, with a reduction of two orders of magnitude in the reverse bias leakage exhibited by the Si-implanted In_0.53Ga_0.47As n⁺/p junctions, which is consistent with passivation of midgap defects in In_0.53Ga_0.47As by the FGA process.

\hbox{In}_{0.53}\hbox{Ga}_{0.47}\hbox{As}

In this paper, state-of-the-art laser thermal annealing is used to form germanide contacts on n-doped Ge and is systematically compared with results generated by conventional rapid thermal annealing. Surface topography, interface quality, crystal structure, and material stoichiometry are explored for both annealing techniques. For electrical characterization, specific contact resistivity and thermal stability are extracted. It is shown that laser thermal annealing can produce a uniform contact with a remarkably smooth substrate interface with specific contact resistivity two to three orders of magnitude lower than the equivalent rapid thermal annealing case. It is shown that a specific contact resistivity of 2.84 × 10-7 Ω·cm2 is achieved for optimized laser thermal anneal energy density conditions.

MOSFETs With an ALD

In this paper, the contact resistivity of NiGe on n-doped Ge is extracted. Although phosphorus is the slowest n-type dopant in terms of diffusion in Ge, the corresponding contact resistivity data for this dopant are sparse. Contact resistivity dependence on implant dose will be determined, as well as a comparison of phosphorus- and arsenic-doped Ge layers. The impact of high contact resistance is evaluated for future technology n-type metal-oxide-semiconductor germanium devices.

\hbox{Al}_{2}\hbox{O}_{3}

This work describes a non-destructive method to introduce impurity atoms into silicon (Si) and germanium (Ge) using Molecular Layer Doping (MLD). Molecules containing dopant atoms (arsenic) were designed, synthesized and chemically bound in self-limiting monolayers to the semiconductor surface. Subsequent annealing enabled diffusion of the dopant atom into the substrate. Material characterization included assessment of surface analysis (AFM) and impurity and carrier concentrations (ECV). Record carrier concentration levels of arsenic (As) in Si (~5×1020 atoms/cm3) by diffusion doping have been achieved, and to the best of our knowledge this work is the first demonstration of doping Ge by MLD. Furthermore due to the ever increasing surface to bulk ratio of future devices (FinFets, MugFETs, nanowire-FETS) surface packing spacing requirements of MLD dopant molecules is becoming more relaxed. It is estimated that a molecular spacing of 2 nm and 3 nm is required to achieve doping concentration of 1020 atoms/cm3 in a 5 nm wide fin and 5 nm diameter nanowire respectively. From a molecular perspective this is readily achievable.

Gate Dielectric

In this work, we report on the occurrence of the soft breakdown (SBD) failure mode in 20nm-thick films of magnesium oxide (MgO) grown on Si substrates. To our knowledge, this is the first observation of this failure mechanism in a high-κ gate dielectric with such a large oxide thickness. We show that the I–V characteristics follow the power-law dependence typical of SBD conduction in a wider voltage range than that reported for SiO2. We pay special attention to the relationship between the magnitude of the current and the normalized differential conductance, and analyze the role played by the injection polarity and substrate type.

Atomically Flat Low-Resistive Germanide Contacts Formed by Laser Thermal Anneal

We present a systematic study of Si dopant implantation and activation in p-type In0.53Ga0.47As in an attempt to optimize the source and drain regions of an n-channel III-V metal?oxide?semiconductor field-effect transistor. Test structures based on the transfer length method were fabricated on Si-implanted p-In0.53Ga0.47As/p-InP buffer/semi-insulting InP. A Doehlert design of experiment (DOE) was used to investigate the effect of annealing temperature and time on the electrical properties of the samples. The DOE covered an experimental domain of 625?725??C and 15?45?s. The current?voltage characteristics of all tested structures exhibited excellent ohmic behavior. The DOE revealed a minimum sheet resistance of (195.6 ? 3.4) ?/? for an optimum anneal condition of 715??C for 32?s. Nonalloyed Au/Ge/Au/Ni/Au contacts, on the sample annealed at 675??C for 30?s (center point of the experimental domain), exhibited a low specific contact resistance of (7.4 ? 4.5)???10?7?? cm2. The sample annealed at 675??C for 30?s was further investigated using secondary ion mass spectrometry (SIMS) and cross-sectional transmission electron microscopy (XTEM) analyses. SIMS revealed that Si ions did not diffuse with annealing, while XTEM showed the formation of characteristic loop defects potentially responsible for the sheet resistance and specific contact resistance degradation.

NiGe Contacts and Junction Architectures for P and As Doped Germanium Devices

The authors report on the structural and electrical properties of TiN/Al2O3/TiN metal–insulator–metal (MIM) capacitor structures in submicron three-dimensional (3D) trench geometries with an aspect ratio of ∼30. A simplified process route was employed where the three layers for the MIM stack were deposited using atomic layer deposition (ALD) in a single run at a process temperature of 250 °C. The TiN top and bottom electrodes were deposited via plasma-enhanced ALD using a tetrakis(dimethylamino)titanium precursor. 3D trench devices yielded capacitance densities of 36 fF/μm2 and quality factors >65 at low frequency (200 Hz), with low leakage current densities (<3 nA/cm2 at 1 V). These devices also show strong optical iridescence which, when combined with the covert embedded capacitance, show potential for system in package (SiP) anticounterfeiting applications.

Molecular Layer Doping: Non-destructive doping of silicon and germanium

The advent of high surface-to-volume ratio devices has necessitated a revised approach to parameter extraction and process evaluation in field-effect transistor technologies. In this work, active d...

Soft breakdown in MgO dielectric layers

The authors extract contact resistivity of NiGe layers on phosphorus-doped and arsenic-doped germanium, using the Transfer Length Method. It is shown experimentally that higher implant dose yields lower contact resistivity. Furthermore phosphorus is a better choice of dopant in terms of contact resistance and sheet resistance at low activation anneal temperatures, such as 500 °C. The impact of high contact resistance is evaluated for 22 nm technology NMOS germanium devices and beyond.

On the activation of implanted silicon ions in p-In0.53Ga0.47As

The electrical behavior of broken down thin films of magnesium oxide (MgO) grown on indium phosphide (InP) substrates was investigated. To our knowledge, this is the first report that identifies the Soft Break Down (SBD) conduction mode in a metal gate/high-κ/III–V semiconductor structure. It is shown that the leakage current associated with this failure mode follows the power-law model I=aVb for both injection polarities in a voltage range that largely exceeds the one reported for SiO2. We also show that the Hard Break Down (HBD) current is remarkably high, involving significant thermal effects that are believed to be at the origin of the switching behavior exhibited by the I–V characteristics.