Cobalt Silicide OHMIC Contacts to 6H-SiC

1994 ◽  
Vol 339 ◽  
Author(s):  
Nils Lundberg ◽  
M. Östling
Keyword(s):  
Current Density ◽  
Ohmic Contacts ◽  
Elevated Temperatures ◽  
Rutherford Backscattering Spectrometry ◽  
Temperature Stability ◽  
Specific Contact Resistance ◽  
X Ray Diffraction ◽  
Materials Analysis ◽  
X Ray ◽  
Specific Contact

ABSTRACTMaterials and electrical evaluation were performed to determine the characteristics of ohmic contacts to 6H-SiC. Both elemental metal (Co) and suicides (CoSi and CoSi2) were studied following heat treatments at 500 °C and 900 °C for 5 hours and 2 hours, respectively. Materials analysis by Rutherford Backscattering Spectrometry (RBS) and X-ray Diffraction (XRD) monitored the temperature stability of the contacts after the annealings. Current density-voltage measurements at elevated temperatures established the specific contact resistance pc.

Fabrication and Characterization of Ohmic Contacts to 3C-SiC Layers Grown on Silicon

2019 ◽  
Vol 963 ◽  
pp. 485-489
Author(s):  
Monia Spera ◽  
Giuseppe Greco ◽  
Raffaella Lo Nigro ◽  
Salvatore di Franco ◽  
Domenico Corso ◽  
...  
Keyword(s):  
Structural Analysis ◽  
Ohmic Contacts ◽  
Specific Contact Resistance ◽  
Silicon Substrates ◽  
X Ray Diffraction ◽  
X Ray ◽  
Specific Contact ◽  
Fabrication And Characterization ◽  
P Type

This paper reports on the formation and characterization of Ohmic contacts to n-type and p-type type 3C-SiC layers grown on silicon substrates. In particular, Ohmic contact behavior was obtained either using Ni or Ti/Al/Ni layers annealed at 950°C. The values of the specific contact resistance ρc estimated by means of circular TLM (C-TLM) structures varied in the range ~ 10-3-10-5 Ωcm2, depending on the doping level of the 3C-SiC layer. A structural analysis performed by X-Ray Diffraction (XRD) allowed to identify the main phases formed upon annealing, i.e., Ni2Si and Al3Ni2. The morphology of the reacted contacts depended on that of the underlying substrate. The results can be useful for the development of a variety of devices on the cubic 3C-SiC polytype.

The Reliability of Multilevel Metallization on InGaAs/GaAs Layers

1994 ◽  
Vol 337 ◽  
Author(s):  
Edward Y. Chang ◽  
J.S. Chen ◽  
J.W. Wu ◽  
K.C. Lin
Keyword(s):  
Contact Resistance ◽  
Ohmic Contacts ◽  
Molecular Beam ◽  
Specific Contact Resistance ◽  
Transmission Line Model ◽  
X Ray Diffraction ◽  
X Ray ◽  
Specific Contact ◽  
Secondary Ion ◽  
Contact Metal

ABSTRACTNon-alloyed ohmic contacts using Ti/Pt/Au and Ni/Ge/Au on InGaAs/GaAs layers grown by Molecular Beam Epitaxy (MBE) have been investigated. The n-type InGaAs film has a doping concentration higher than 1X1019 cm-3. Specific contact resistance below 2X10-7 Ωcm2 could be easily achieved with Ti/Pt/Au. Due to the layer intermixing and outdiffusion of In and Ga, the specific contact resistance and sheet resistance increase after thermal treatment. When Ni/Ge/Au is used as the contact metal, the outdiffusion of In and Ga atoms is more severe than that of Ti/Pt/Au. After annealing at 450°C for two minutes, the Au4In formed and the characteristics of the contact became worse. All the phenomena illustrated above have been observed and investigated by Transmission Line Model, X-ray diffraction, Auger Electron Spectroscopy and Secondary Ion Mass Spectrum. As far as the thermal stability is concerned, it is convinced that Ti/Pt/Au is the best one of these two non-alloyed ohmic contact studied.

Ohmic Contacts to p-Type InGaAs/InP with a Graded Bandgap Heterobarrier

1993 ◽  
Vol 318 ◽  
Author(s):  
Patrick W. Leech ◽  
Geoffrey K. Reeves
Keyword(s):  
Contact Resistance ◽  
Ohmic Contacts ◽  
Rutherford Backscattering Spectrometry ◽  
Specific Contact Resistance ◽  
Superlattice Structure ◽  
Specific Contact ◽  
P Type ◽  
Metal Layers ◽  
Anneal Temperature ◽  
Graded Bandgap

ABSTRACTOhmic contacts to p-type InP with an In0.47Ga0.53As buffer layer and an interposed superlattice of 50 Å In0.47Ga0.53As/ 50 Å InP have been investigated. Initial studies of contacts to In0.47Ga0.53As/ InP without the superlattice structure have shown that Pd/Zn/Pd/Au metallization produced a lower specific contact resistance (pc = 1.1 × 10−4 Ω cm2) than Pd/Ge/Au, and over a wider range of anneal temperature than Au/Zn/Au. The incorporation of the superlattice in the p-In0.47Ga0.53As/ InP structure resulted in Pd/Zn/Pd/Au contacts with pc of 3.2 × 10−5 Ω cm2 as-deposited and 7.5 × 10−6 Ω.cm2 after a 500 °C anneal. The presence of Pd/Zn in the metallization was shown as important in reducing pc. Significant intermixing of the metal layers and In0.47Ga0.53As occured at ≥ 350 °C, as revealed by Rutherford backscattering spectrometry.

Investigation of Factors Limiting the High Temperature Stability of W/WC/TaC/SiC Ohmic Contacts to n-type 6H-SiC

2000 ◽  
Vol 640 ◽  
Author(s):  
T. Jang ◽  
B. Odekirk ◽  
L. M. Porter
Keyword(s):  
High Temperature ◽  
Ohmic Contacts ◽  
Temperature Stability ◽  
Atomic Scale ◽  
Specific Contact Resistance ◽  
High Temperature Stability ◽  
Specific Contact ◽  
Operating Limits ◽  
Metallurgical Reactions ◽  
Metal Layers

ABSTRACTThe electrical properties and thermal stability of TaC ohmic contacts with W/WC overlayers were investigated on n-type 6H-SiC (0001) substrates. The specific contact resistance (SCR) was measured after annealing at 600 °C and 1000 °C for 50 ∼ 1000 h. The SCRs (3.0 ∼ 3.6 ×10−5 Ωcm2) of contacts annealed at 600 °C for 1000 h remained constant within the experimental error. Significant increases in the SCR were not observed until the samples were annealed at 1000 °C for several hundred hours.No reaction of the film with the SiC substrate was observed after annealing at 600 °C for 1000 h; however, atomic-scale reactions appeared to be concentrated adjacent to grain boundaries in the reacted film. From Auger depth profiles, it was found that W and WC reacted to form W2C on TaC after annealing.According to SIMS analysis, after annealing at 1000 °C for 600 h, small but measurable changes in the electrical characteristics were associated with O incorporation at the interface between TaC and SiC. Investigation of the W/WC/TaC/SiC interface by TEM indicated that a reaction between the metal layers had occurred, but there was no observed reaction with the SiC substrate. After annealing for 1000 h, substantial changes in the contacts were observed. The findings indicate that both oxidation and metallurgical reactions have important implications on the current operating limits for SiC high temperature devices.

Nonalloyed Ohmic Contacts to N-Si Using a Strained Si0.5Ge0.5 Buffer Layer

1993 ◽  
Vol 320 ◽  
Author(s):  
Hsing-Kuen Liou ◽  
Edward S. Yang ◽  
K. N. Tu
Keyword(s):  
Buffer Layer ◽  
Photoelectron Spectroscopy ◽  
Ohmic Contacts ◽  
Depth Profiling ◽  
Binding Energies ◽  
Specific Contact Resistance ◽  
Strained Si ◽  
X Ray ◽  
Ohmic Behavior ◽  
Specific Contact

ABSTRACTNonalloyed shallow ohmic contacts to n-Si have been fabricated by using an 80 Å thick strained Si0.5Ge0.5 buffer layer grown by molecular beam epitaxy. X-ray photoelectron spectroscopy was employed to investigate the Si 2p and Ge 3d core level binding energies of the strained and the relaxed Si0.5Ge0.5 and to determine their relative Fermi level positions. It was found that the surfaces of strained Si0.5Ge0.5 exhibit pinning very close to the conduction band. Rutherford backscattering and Auger depth profiling were employed to determine the contact reactions using Ti, W or Pt as contact metals. In the case of Pt, a 500 Å W diffusion barrier can protect the ohmic behavior up to 550 °C for 30 min. The specific contact resistance of the Pt/W/Si0.5Ge0.5/n-Si contact extracted from the D-type cross-bridge Kelvin resistor was 3.5x10-5 Ω·cm2.

The Influence of Contact Composition, Pretreatment, and Annealing Gas on the Ohmic Behavior of Ti/Al-Based Ohmic Contacts to n-Al0.4Ga0.6N

2001 ◽  
Vol 680 ◽  
Author(s):  
K. O. Schweitz ◽  
T. G. Pribicko ◽  
S. E. Mohney ◽  
T. F. Isaacs-Smith ◽  
J. Williams ◽  
...  
Keyword(s):  
Ohmic Contacts ◽  
Metal Layer ◽  
Active Role ◽  
Specific Contact Resistance ◽  
X Ray Diffraction ◽  
Group Iii ◽  
Ohmic Behavior ◽  
Annealing Conditions ◽  
Specific Contact ◽  
Group Iii Nitride

ABSTRACTAs the group III nitride semiconductor technology matures, an increasing number of devices are being fabricated with high Al fraction AlGaN. In this study, ohmic behavior is achieved using Ti/Al/Pt/Au contacts to n-Al0.4Ga0.6N, which is the highest Al fraction for which ohmic contact formation has been reported. The effect of contact composition, pretreatment, and annealing conditions is studied by 30 s isochronal annealing experiments between 500°C and 1000°C. A specific contact resistance ρC of (5±3) × 10−5 ωcm2 is obtained using Ti(26 nm)/Al(74 nm)/Pt(50 nm)/Au(50 nm) contacts to n-Al0.4Ga0.6N annealed in N2 at 800°C; however, this value is shown to be artificially high because the metal sheet resistance RM is 4 ω/⊏ causing an artifact in the data analysis. All contacts with ρC < 10−3 ωcm2 exhibit a local minimum in ρC after annealing at 800°C. The observed increase in ρC upon annealing at 850°C and 900°C, however, is not an artifact originating from a change in RM. The top Au layer is found to play an active role in forming ohmic contacts with low ρC, since omitting the Au layer yields an increase in ρC of two orders of magnitude after annealing at 800°C. Furthermore, leaving out the Au layer requires an annealing temperature of 700°C to result in linear I-V curves for currents up to 100 µA, as opposed to 500°C when the Au layer is present. The role of Au is further studied in Ti(26 nm)/Al(74 nm)/Ni(50 nm)/Au(50 nm) contacts, where Rutherford backscattering spectroscopy reveals Ga in the metal layer and/or Au buried deeper than the original semiconductor-metal interface, and x-ray diffraction indicates the formation of new phases to happen concurrently with a decrease in ρC of three orders of magnitude.

Alloying Behavior and Reliabilty of Pt Embedded Metal/n+-GaAs Thin Ohmic Contact System

1996 ◽  
Vol 448 ◽  
Author(s):  
C.Y. Kim ◽  
W.S. Lee ◽  
H.J. Kwon ◽  
Y.W. Jeong ◽  
J.S. Lee ◽  
...  
Keyword(s):  
Ohmic Contact ◽  
Integrated Circuit ◽  
Ohmic Contacts ◽  
Specific Contact Resistance ◽  
X Ray Diffraction ◽  
Cross Sectional ◽  
Monolithic Microwave Integrated Circuit ◽  
Surface And Interface ◽  
Transmission Line Method ◽  
Specific Contact

AbstractPt embedded ohmic contacts to n+-GaAs (AuGe-800 Å/ Ni-150 Å/Pt-200 Å/Au-500 Å and AuGe-800 Å/Pt-200 Å/Ni-150 Å/Au-500 Å/n+-GaAs) have been developed for the advanced discrete devices and MMIC (monolithic microwave integrated circuit) applications. The specific contact resistance investigated by Transmission Line Method is 1x10-6 Ω cm2. Ohmic contact reliability investigated by thermal storage test at 300 °C under N2 ambient demonstrated nearly the same contact characteristics after 3000 hours. In both systems, X-ray diffraction results and Auger depth profiles show that the good ohmic contact is related to the formation of Au7Ga2, PtAs2, and Ni19Gen12 phases. AuGa compound enhances the creation of Ga vacancies, allowing incorporation of Ge into Ga sites, and PtAs compound is piled up in the middle of AuGa layer to suppress As outdifrusion from GaAs substrate. TEM cross-sectional view indicates that metal/n+-GaAs reaction layer is ∼ 1200 Å beneath GaAs. Surface and interface are very smooth and abrupt in comparison to conventional AuGe/Ni/Au contact.

The Stability to Ageing of Pd/Zn and Pt-Based Ohmic Contacts to p-InGaAs/InP

1998 ◽  
Vol 514 ◽  
Author(s):  
P. W. Leech ◽  
G. K. Reeves ◽  
P. Ressel
Keyword(s):  
Contact Resistance ◽  
Barrier Layer ◽  
Ohmic Contacts ◽  
Rutherford Backscattering Spectrometry ◽  
Rutherford Backscattering ◽  
Contact System ◽  
Specific Contact Resistance ◽  
Barrier Layers ◽  
Specific Contact ◽  
The Stability

ABSTRACTPd/Zn/Au contacts to p-In0.53Ga0.47As/InP with various barrier layers (Pd, Pt or LaB,) to the indiffusion of Au have been examined by Rutherford Backscattering Spectrometry (RBS). For the metallisations with a barrier layer of Pd, the ageing of the contacts at 400°C for 20 h produced a widespread indiffusion of Au. In comparison, the incorporation of a layer of Pt or amorphous LaB6 prevented an indiffusion of Au and significantly reduced any outdiffusion of the semiconductor elements. The presence of the barrier layer of Pt or LaB6 produced little or no detrimental increase in specific contact resistance, ρc, for this contact system. Values of ρc in the range 8–10 × 10−6 Ω cm2 were obtained for all of the contacts based on Pd/Zn/Au after annealing at 500°C. A comparison has been made with the characteristics of Pt/Ti/Pt/Au contacts to p-In0.53Ga0.47As/ InP which were shown as stable against the indiffusion of Au.

High Temperature Stability of Amorphous TaxCu1-x Diffusion Barriers on GaAs

1986 ◽  
Vol 77 ◽  
Author(s):  
J. E. Oh ◽  
J. J. Pouch ◽  
D. C. Ingram ◽  
S. A. Alterovitz ◽  
J. A. Woollam
Keyword(s):  
Elevated Temperatures ◽  
Alloy Composition ◽  
Vacuum Annealing ◽  
Temperature Stability ◽  
Diffusion Barriers ◽  
Maximum Temperature ◽  
High Temperature Stability ◽  
X Ray Diffraction ◽  
X Ray ◽  
Temperature Coefficients

ABSTRACTThe x value of the most thermally stable co-sputtered TaxCu1-x alloy films are found to correlate with measured maximum temperature coefficients of resistance as a function of alloy composition. To investigate the possible application of these materials as diffusion barriers for the Au-GaAs system, vacuum annealing and infrared rapid thermal annealing are made over a wide temperature range. Resistivity changes, X-ray diffraction, Auger electron spectroscopy, and Rutherford backscattering measurements are performed to find the metallurgical stabilities of these materials at elevated temperatures.For high x values, the reaction temperature for TaxCu1-x, in contact with GaAs lies between 500 and 700°C. For Au in contact with TaxCu1-x the TaxCu1-x/GaAs reaction occurs at about 600°C. Amorphous Ta93Cu7 exhibits uniform mixing with surrounding elements, whereas Ta80Cu20 exhibits phase separation.

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