Effects of CO/sub 2/ atmosphere on contact resistance characteristics of noble metal contacts

While nickel ohmic contacts to n-type silicon carbide have good electrical properties, the physical contact, and therefore the reliability, can be poor. An approach is described for using the good electrical properties of Ni ohmic contacts while using another metal for its desired mechanical, thermal and/or chemical properties. In the present work, once the Ni contacts have been annealed forming nickel silicides and achieving low contact resistance, they are etched off. Removing the primary Ni contacts also eliminates the poor morphology, voids, and at least some of the excess carbon produced by the Ni/SiC reaction. The Ni contacts are then replaced by a second contact metal. This second metal displays low contact resistance as-deposited, indicating that the critical feature responsible for the ohmic contact has not been removed by the primary contact etch. Not only does this approach provide more flexibility for optimizing the contact for a given application, it also provides some insight into the ohmic contact formation mechanism.

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A Scale Analysis Approach to Thermal Contact Resistance

Heat Transfer, Volume 1 ◽

10.1115/imece2003-55283 ◽

2003 ◽

Cited By ~ 1

Author(s):

M. Bahrami ◽

J. R. Culham ◽

M. M. Yovanovich

Keyword(s):

Contact Resistance ◽

Entire Range ◽

Thermal Contact Resistance ◽

Present Model ◽

Thermal Contact ◽

Scale Analysis ◽

Metal Contacts ◽

Novel Approach ◽

Wide Range ◽

Data Points

A new analytical model is developed for predicting thermal contact resistance (TCR) of non-conforming rough contacts of bare solids in a vacuum. Instead of using probability relationships to model the size and number of microcontacts of Gaussian surfaces, a novel approach by employing the “scale analysis methods” is taken. It is shown that the mean size of the microcontacts is proportional to the surface roughness and inversely proportional to the surface asperity slope. A general relationship for determining TCR is derived by superposition of the macro and the effective micro thermal resistances. The present model allows TCR to be predicted over the entire range of non-conforming rough contacts from conforming rough to smooth Hertzian contacts. It is demonstrated that the geometry of heat sources on a half-space for microcontacts is justifiable and that effective micro thermal resistance is not a function of surface curvature. A comparison of the present model with 604 experimental data points, collected by many researchers during the last forty years, shows good agreement for the entire range of TCR. The data covers a wide range of materials, mechanical and thermophysical properties, micro and macro contact geometries, and similar and dissimilar metal contacts.

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Al/Ni And Al/Ti Ohmic Contact To P-type SiC Diffused Layer

MRS Proceedings ◽

10.1557/proc-640-h5.19 ◽

2000 ◽

Vol 640 ◽

Cited By ~ 2

Author(s):

Xaiobin Wang ◽

Stanislav Soloviev ◽

Ying Gao ◽

G. Straty ◽

Tangali Sudarshan ◽

...

Keyword(s):

Contact Resistance ◽

Ohmic Contacts ◽

Specific Contact Resistance ◽

Metal Contacts ◽

Transfer Length ◽

Type Layer ◽

Transmission Line Method ◽

Specific Contact ◽

Background Doping ◽

P Type

ABSTRACTOhmic contacts to p-type SiC were fabricated by depositing Al/Ni and Al/Ti followed by high temperature annealing. A p-type layer was fabricated by Al or B diffusion from vapor phase into both p-type and n-type substrates. The thickness of the diffused layer was about 0.1–0.2 μm with surface carrier concentration of about 1.0×1019cm−3. Metal contacts to a p-type substrate with a background doping concentration of 1.2×1018cm−3, without a diffusion layer, were also formed. The values of specific contact resistance obtained by Circular Transmission Line Method (CTLM) and Transfer Length Method (TLM) for the n-type substrate, and by Cox & Strack method for p-type substrate, respectively, varied from 1.3×10−4Ωcm2 to 8.8×10−3 Ωcm2. The results indicate that the specific contact resistance could be significantly reduced by creating a highly doped diffused surface layer.

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Characterization of Contact Resistance between Carbon Nanotubes Film and Metal Electrodes

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.683.238 ◽

2013 ◽

Vol 683 ◽

pp. 238-241

Author(s):

Ki Bong Han ◽

Yong Ho Choi

Keyword(s):

Carbon Nanotubes ◽

Carbon Nanotube ◽

Contact Resistance ◽

Chemical Properties ◽

Metal Electrode ◽

Metal Contacts ◽

Metal Electrodes ◽

3 Dimensional ◽

Current Path ◽

Classical Technique

Carbon nanotube has attracted great research attentions due to its outstanding electrical, physical, mechanical, chemical properties. Based on its excellent properties, the carbon nanotube is promising nanoscale material for novel electrical, mechanical, chemical, and biological devices and sensors. However, it is very difficult to control the structure of carbon nanotube during synthesis. A carbon nanotubes film has 3 dimensional structures of interwoven carbon nanotubes as well as unique properties such as transparency, flexibility and good electrical conductivity. More importantly, the properties of carbon nanotubes are ensemble averaged in this formation. In this research, we study the contact resistance between carbon nanotubes film and metal electrode. For most of electrical devices using carbon nanotubes film, it is necessary to have metal electrodes on the film for current path. A resistance at the contact lowers the electrical efficiencies of the devices. Therefore, it is important to measure and characterize the contact resistance and lower it for better efficiencies. The device demonstrated in this study using classical technique for metal contacts provides relatively reliable contact resistance measurements for carbon nanotubes film applications.

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Low-Contact-Resistance Contacts to Graphene via Metal-Mediated Etching

MRS Proceedings ◽

10.1557/opl.2013.862 ◽

2013 ◽

Vol 1553 ◽

Author(s):

Wei Sun Leong ◽

John T.L. Thong

Keyword(s):

Contact Resistance ◽

Promising Method ◽

Pristine Graphene ◽

Cmos Process ◽

Metal Contacts ◽

Ambient Conditions ◽

Etching Technique ◽

Graphene Devices

ABSTRACTThe theoretically-predicted enhancement of metal-graphene contacts using the “end-contacted” configuration is studied. Graphene edges at the source/drain regions are created via a CMOS process compatible metal-assisted etching technique. The on-resistance of a graphene device with cobalt-etched-graphene contacts shows 6 times improvement compared to pristine graphene device. Apart from that, four-point contacted graphene devices with nickel-etched-graphene contacts were fabricated and tested under ambient conditions. The proposed graphene devices exhibit contact resistance as low as 14 Ωμm, with an average of 90 Ωμm. Thus, forming metal-etched-graphene contacts is a promising method to obtain low-contact resistance metal contacts to graphene.

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