Selective Deposition of Ohmic Contacts to p-InGaAs by Electroless Plating
TL;DR: In this article, a three-layer Pd/Ru/Au electrolessly deposited ohmic contact to p-InGaAs, suitable for use in a self-aligned process, was presented.
Abstract: A three-layer Pd/Ru/Au electrolessly deposited ohmic contact to p-InGaAs, suitable for use in a self-aligned process, is presented. Cross-sectional transmission electron microscopy shows that the electrolessly plated metal layers are dense with a thin uniform reaction between the Pd and InGaAs. This contact metallization remains shallow and electrically stable even after aging for 4 h at 250°C. An average specific contact resistance of (1.6 ± 0.6) × 10 -6 Ω cm 2 was obtained for as-deposited contacts with an HCl surface treatment. When a UV ozone and NH 4 OH surface treatment was used, specific contact resistances as low as (2.1 ± 0.9) X 10 -7 Ω cm 2 were obtained.
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TL;DR: In this paper, the authors report specific contact resistance (ρc) values for Mo-, Ti-, TiW, Pd-, and Pt-based Ohmic contacts to n+-In086Ga014As that are deposited with either collimated sputter or electron-beam deposition Palladium-based contacts with 5 nm of electronbeam evaporated Pd.
Abstract: The authors report specific contact resistance (ρc) values for Mo-, Ti-, TiW-, Pd-, and Pt-based Ohmic contacts to n+-In086Ga014As that are deposited with either collimated sputter or electron-beam deposition Palladium-based contacts with 5 nm of electron-beam evaporated Pd have a specific contact resistance of 76 ± 05 × 10−9 Ω cm2, while identical collimated sputter deposited contacts have a specific contact resistance of 41 ± 04 × 10−9 Ω cm2 Contacts with a very thin evaporated Pd layer (2 nm) or a sputtered Pd/Ti 1/1 nm × 4 multilayer have stable ρc values of 54 ± 05 × 10−9 and 50 ± 05 × 10−9 Ω cm2, respectively, after 2 h at 270 °C The ρc of sputter deposited TiW-based contacts is an order of magnitude lower than for identical evaporated contacts (16 ± 03 × 10−8 vs 26 ± 03 × 10−7 Ω cm2) and is stable during annealing, while sputter deposition of Pt-based contacts yields rc values that are half an order of magnitude lower than similar evaporated contacts (45 ± 10 × 10−9 vs 17 ± 02
68 citations
TL;DR: The role of Fermi level pinning on the Schottky barrier that is often formed at the metal/semiconductor interface and common strategies for forming ohmic contacts is discussed in this paper.
Abstract: The scaling of transistors to smaller dimensions and the exploration of devices with III–V and Ge channels for digital logic places serious demands on the ohmic contacts used in these devices. Contacts with extremely low specific contact resistances are required to take full advantage of the performance promised by alternative semiconductor materials. In addition, device processes and contact morphologies must be compatible with the geometry and feature sizes of the transistors. In this article, we begin by reviewing what is known about contacts to Ge, InGaAs, InAs, and InSb, including the role of Fermi level pinning on the Schottky barrier that is often formed at the metal/semiconductor interface and common strategies for forming ohmic contacts. Then we turn our attention to the additional challenges faced when preparing ohmic contacts for the many types of field-effect transistors now under development for Ge and III–V complementary field-effect transistor technology.
44 citations
TL;DR: In this paper, a multilayer ohmic contact with differing first metal layers (Mo, Pd, Pt) beneath a Ti/Pt diffusion barrier and Au cap was fabricated on n+ and p+-InGaAs, and the relationship between their specific contact resistance and interfacial chemistry was examined.
Abstract: Multilayer ohmic contacts with differing first metal layers (M = Mo, Pd, Pt) beneath a Ti/Pt diffusion barrier and Au cap were fabricated on n+ and p+-InGaAs, and the relationship between their specific contact resistance and interfacial chemistry was examined. Palladium-based contacts offered the lowest specific contact resistances of ρc=3.2×10−8 and 1.9×10−8 Ω-cm2 to n+- and p+-InGaAs, respectively. The low resistances of the Pd-based contact were correlated with the formation of a uniform PdxInGaAs phase in direct contact with InGaAs, as observed using transmission electron microscopy and energy dispersive spectroscopy. On the other hand, the Mo-based contact to n+ and p+-InGaAs had much higher specific contact resistances, even though its specific contact resistance on lightly doped n-InGaAs was nearly the same as that of the Pd-based contact. The cause of this discrepancy was identified to be the native oxide layer that remained between the contact and semiconductor in the Mo-based contacts, as revea...
35 citations
TL;DR: An electroless Ru plating bath is prepared by mixing Ru precursor (K2RuCl5!xH2O), oxidizer (NaClO), stabilizer ( NaOH), and reducing agent (NaNO2) simultaneously in deionized water at a molar ratio of 1:1:20:10 as discussed by the authors.
Abstract: An electroless Ru plating bath is prepared by mixing Ru precursor (K2RuCl5!xH2O), oxidizer (NaClO), stabilizer (NaOH), and reducing agent (NaNO2) simultaneously in deionized water at a molar ratio of 1:1:20:10. Instead of conventional direct reduction route, the RuCl5 2" experiences an oxidative-reductive sequence to form metallic Ru on an activated Si substrate. Spectra from ultraviolet-visible and X-ray absorption spectroscopy indicate that the RuCl5 2" is oxidized to form RuO4 initially, followed by a slight reduction becoming RuO4 2". The RuO4 2" solution is relatively stable and is able to undergo further reduction to render metallic Ru via heterogeneous nucleation and growth. Images from scanning electron microscope demonstrate a solid film of 100 nm with scattered protrusions and cavities after 120 min plating time. Analysis from atomic force microscope determines its surface roughness of 7.8 nm. From X-ray diffraction patterns, the as-deposited film reveals an amorphous structure but turns crystalline after Ar annealing at 400#C for 2 h. Curve-fitting of Ru 3p3/2 signal from X-ray photoelectron spectroscopy suggests a film composition of 92.49 atom % Ru and 7.51 atom % RuO2. The electroless Ru plating bath exhibits impressive life time (137 h) and negligible homogeneous precipitation without involving surfactants and unnecessary chemical additives. VC 2011 The Electrochemical Society. [DOI: 10.1149/1.3592996] All rights reserved.
15 citations
TL;DR: In this article, structural characterization and contact resistances between metal and epitaxial regrowth for four structures: Si doped and Si and Te co-doped n + InAs regrowth on a 10-nm In 0.53 Ga 0.47 As channel, Si and Si-Te Co-Doped n+In 0.6×10 19 ǫ −3 without saturation effects, and 7-nm
9 citations
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TL;DR: In this article, theoretical and experimental results concerning two sources of error in the determination of specific contact resistance of ohmic contacts to semiconductor device structures that utilize circular test patterns with varying gap length are presented.
Abstract: This paper presents theoretical and experimental results concerning two sources of error in the determination of specific contact resistance of ohmic contacts to semiconductor device structures that utilize circular test patterns with varying gap length. It is shown that the potential drop vs gap length data cannot be usually represented by a straight line and a non-zero metal overlay sheet resistance can significantly alter the effective contact resistance value.
429 citations
IBM1
TL;DR: In this paper, a SiGe NPN HBT with unity gain cutoff frequency (f/sub T/) of 207 GHz and an f/sub MAX/ extrapolated from Mason's unilateral gain of 285 GHz was reported.
Abstract: This paper reports on SiGe NPN HBTs with unity gain cutoff frequency (f/sub T/) of 207 GHz and an f/sub MAX/ extrapolated from Mason's unilateral gain of 285 GHz. f/sub MAX/ extrapolated from maximum available gain is 194 GHz. Transistors sized 0.12/spl times/2.5 /spl mu/m/sup 2/ have these characteristics at a linear current of 1.0 mA//spl mu/m (8.3 mA//spl mu/m/sup 2/). Smaller transistors (0.12/spl times/0.5 /spl mu/m/sup 2/) have an f/sub T/ of 180 GHz at 800 /spl mu/A current. The devices have a pinched base sheet resistance of 2.5 k/spl Omega//sq. and an open-base breakdown voltage BV/sub CEO/ of 1.7 V. The improved performance is a result of a new self-aligned device structure that minimizes parasitic resistance and capacitance without affecting f/sub T/ at small lateral dimensions.
266 citations
TL;DR: In this paper, the initial stages of the Pd-GaAs reactions are studied by high resolution transmission electron microscopy, electron diffraction and energy-dispersive analysis of X-rays.
73 citations
TL;DR: In this paper, the deposition mechanism of gold and palladium and the effect of adding palladium to gold is discussed and a suitable choice of mixture of the three solutions is made, they allow the fabrication of multilayered heterostructures which could be fruitfully used for ohmic contact preparation onto without any initial activation step.
Abstract: Deposition of gold, palladium, and gold‐palladium alloys is obtained with the help of acidic electroless baths of low metal content. The baths are prepared by suitably mixing separate solutions containing the reductant (hydroxylamine hydrochloride) or one of the desired cations respectively, with suitable additives. The stability of the baths with time is good and their replenishment easy to realize. Provided that a suitable choice of mixture of the three solutions is made, they allow the fabrication of multilayered heterostructures which could be fruitfully used for ohmic contact preparation onto without any initial activation step. The deposition mechanism of gold and palladium and the effect of adding palladium to gold is discussed.
57 citations
TL;DR: In this paper, the authors reported extremely low specific contact resistivity (ρc) nonalloyed Ohmic contacts to n-type In0.53Ga0.47As, lattice matched to InP.
Abstract: We report extremely low specific contact resistivity (ρc) nonalloyed Ohmic contacts to n-type In0.53Ga0.47As, lattice matched to InP. Contacts were formed by oxidizing the semiconductor surface through exposure to ultraviolet-generated ozone, subsequently immersing the wafer in ammonium hydroxide (NH4OH, 14.8 normality), and finally depositing either Ti∕Pd∕Au contact metal by electron-beam evaporation or TiW contact metal by vacuum sputtering. Ti∕Pd∕Au contacts exhibited ρc of (0.73±0.44)Ωμm2—i.e., (7.3±4.4)×10−9Ωcm2—while TiW contacts exhibited ρc of (0.84±0.48)Ωμm2. The TiW contacts are thermally stable, showing no observable degradation in resistivity after a 500°C annealing of 1min duration.
55 citations