Improved Nickel Silicide Ohmic Contacts to N-Type 4H and 6H-SiC Using Nichrome

1996 ◽  
Vol 423 ◽  
Author(s):  
E. D. Luckowski ◽  
J. R. Williams ◽  
M. J. Bozack ◽  
T. Isaacs-Smith ◽  
J. Crofton
Keyword(s):  
Barrier Layer ◽  
Ohmic Contact ◽  
Ohmic Contacts ◽  
Contact Layer ◽  
Weight Percent ◽  
Nickel Silicide ◽  
Electrical Characteristics ◽  
Success Rates ◽  
Diffusion Barrier Layer

AbstractResults are reported for ohmic contacts formed on n-type 4H and 6H-SiC using nichrome (80/20 weight percent Ni/Cr). In comparison to contacts formed on 6H-SiC using pure Ni, the electrical characteristics of these NiCr contacts are similar (∼ 1E-5 Ω-cm2 for moderately doped material), and composite Au/NiCr contacts exhibit good stability during long-term anneals (∼ 2500 hr) at 300 C without the requirement of a diffusion barrier layer between the ohmic contact layer and the Au cap layer. The use of NiCr also results in success rates near 100% for direct wire bonding to the Au cap layers.

scholarly journals DEPOSITION OF Al/SnAl OHMIC CONTACT ON SILICON FROM A LIQUID PHASE

2021 ◽  
Author(s):  
Vadym V. Tsybulenko ◽  
Stanislav V. Shutov ◽  
Oleg O. Boskin
Keyword(s):  
Liquid Phase ◽  
Silicon Wafer ◽  
Liquid Phase Epitaxy ◽  
Ohmic Contact ◽  
Ohmic Contacts ◽  
Contact Layer ◽  
Metal Films ◽  
Wafer Surface ◽  
Semiconductor Wafer

Background. Single- and multi-layer metal films are widely utilized in modern electronics and optoelectronics as ohmic contacts. As a rule, the films are deposited by thermal evaporation, ion sputtering and chemical vapour deposition. However the methods of deposition from a liquid phase are the most simple and cost-effective. Thus the ohmic contact deposition by these methods is still an actual problem. Objective. The purpose of the paper is to study the possibility of deposition of multi-layer ohmic metal films over a semiconductor wafer surface from a liquid phase, particularly by scanning liquid phase epitaxy technique. Methods. In this work we considered the influence of a long-term temperature gradient at the interface metallic solution-melt – semiconductor wafer on the possibility of deposition of multi-layer ohmic metal films on the semiconductor wafer surface during segmental contact between the solution-melt and the wafer. For this purpose we carried out the simulation of heat transport process, wafer wetting process as well as the process of wafer cleansing off the solution-melt taking into account capillary phenomena in the mask openings using the method of scanning liquid phase epitaxy. For experimental confirmation of adequacy of the model proposed we carried out the deposition of Al/SnAl layer on silicon wafer in the above mentioned conditions. Results. We have deposited the contact layer Al/SnAl on the surface of silicon wafer from Al-Sn solution-melt by scanning liquid phase epitaxy technique using supplementary heater for the wafer and mask installed in the apparatus. The contact layer is made as three identical pads located at different distance one from each other. By the analysis of current-voltage characteristic we determined that the metallic film contact with the semiconductor is a non-rectifying, i.e. ohmic contact. The specific contact resistance was determined by the Transmission Line Method using linear configuration of the contact pads (LTLM). Its value was 7.2∙10-4 Ohm·cm2. Conclusions. The principal possibility of obtaining of multi-layer ohmic contacts to the semiconductor by scanning liquid phase epitaxy technique in conditions of segmental contact between the solution-melt and the wafer as well as long-term gradient at the contact interface was shown. The conditions were realized by using extra heating of the wafer back side and the high-temperature mask through which the solution-melt contacted the wafer.

Structure and Electrical Properties of Cu/Ge Ohmic Contacts

1995 ◽  
Vol 402 ◽  
Author(s):  
S. Oktyabrsky ◽  
M. O. Aboelfotoh ◽  
J. Narayan
Keyword(s):  
Ohmic Contacts ◽  
Contact Layer ◽  
Interfacial Microstructure ◽  
Contact Resistivity ◽  
Electrical Characteristics ◽  
Secondary Phases ◽  
Gaas Substrates ◽  
Wide Range ◽  
Specific Contact ◽  
Average Lattice

AbstractChemistry, crystal structure, interfacial microstructure and electrical characteristics of novel Cu-Ge alloyed ohmic contacts to n-type GaAs with a very low specific contact resistivity ((4–6)×10−7 Ω·cm2 for n∼1×1017 cm−3) were investigated by various methods. The Cu-Ge alloys with a wide range of Ge concentration, from 15 to 40 at %, were prepared by depositing sequentially Cu and Ge layers (or vise versa) onto GaAs substrates at room temperature followed by annealing at 400°C. It is shown that Cu reacts only with Ge to form the ξ and ε1-Cu3Ge phases. The latter has an orthorhombic structure with average lattice parameters: a = 5.301 Å, bo = 4.204 Å, co = 4.555 Å, arising from the parent hexagonal ξ-phase by Cu-Ge ordering along ao. The interface with GaAs is atomically sharp and free from secondary phases. The ε1-Cu3Ge ordered phase which is chemically inert with respect to GaAs, is believed to be responsible for high thermal stability (up to 450°C), interface sharpness, high contact layer uniformity and low specific resistivity of 6 μΩ cm. Formation of the Cu-Ge phases creates a highly doped n+-GaAs surface layer which leads to the low contact resistivity.

Effect of Pt diffusion barrier layer in Ni/AuGe/Pt/Au on ohmic contact to n-GaAs

2015 ◽  
Vol 36 (3) ◽  
pp. 036002 ◽  
Author(s):  
Yong Wang ◽  
Dandan Liu ◽  
Guoqing Feng ◽  
Zhen Ye ◽  
Zhanqi Gao ◽  
...  
Keyword(s):  
Barrier Layer ◽  
Ohmic Contact ◽  
Diffusion Barrier ◽  
Diffusion Barrier Layer

scholarly journals Low Temperature Ni-Al Ohmic Contacts to p-Type 4H-SiC Using Semi-Salicide Processing

2018 ◽  
Vol 924 ◽  
pp. 389-392 ◽  
Author(s):  
Mattias Ekström ◽  
Shuoben Hou ◽  
Hossein Elahipanah ◽  
Arash Salemi ◽  
Mikael Östling ◽  
...  
Keyword(s):  
Low Temperature ◽  
Ohmic Contact ◽  
Thermal Processing ◽  
Ohmic Contacts ◽  
Rapid Thermal Processing ◽  
Nickel Silicide ◽  
Second Step ◽  
Low Resistance ◽  
Annealing Step ◽  
P Type

Most semiconductor devices require low-resistance ohmic contact to p-type doped regions. In this work, we present a semi-salicide process that forms low-resistance contacts (~10-4 Ω cm2) to epitaxially grown p-type (>5×1018 cm-3) 4H-SiC at temperatures as low as 600 °C using rapid thermal processing (RTP). The first step is to self-align the nickel silicide (Ni2Si) at 600 °C. The second step is to deposit aluminium on top of the silicide, pattern it and then perform a second annealing step in the range 500 °C to 700 °C.

Anode Side Diffusion Barrier Coating for Solid Oxide Fuel Cells Interconnects

2010 ◽  
Vol 7 (3) ◽  
Author(s):  
J. Froitzheim ◽  
L. Niewolak ◽  
M. Brandner ◽  
L. Singheiser ◽  
W. J. Quadakkers
Keyword(s):  
Fuel Cells ◽  
Solid Oxide Fuel Cells ◽  
Barrier Layer ◽  
Diffusion Barrier ◽  
Ferritic Steel ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Anode Side ◽  
Diffusion Barrier Layer

During the operation of solid oxide fuel cells (SOFCs) the Ni base anode and/or Ni-mesh is in direct contact with the ferritic steel interconnect or the metallic substrate. For assuring long-term stack operation a diffusion barrier layer with high electronic conductivity may be needed to impede interdiffusion between the various components. A pre-oxidation layer on the ferritic steel turned out to be not viable as a barrier layer since a Ni-layer tends to dissociate the oxide scale. Therefore the potential of ceria as a diffusion barrier layer for the anode side of the SOFC was estimated. The barrier properties of a ceria coating between the Ni and the ferritic steel Crofer 22 APU were tested for 1000 h in Ar–4H2–2H2O at 800°C. Conductivity experiments were performed in the same atmosphere at different temperatures. After long-term exposures no indication of interdiffusion between Ni and ferritic steel could be detected, however, sputtered coatings on ferritic steel substrates showed significantly lower conductivities than bulk ceria samples because of void formation between the ceria and the oxide on the steel surface. The latter could be prevented by an intermediate copper layer, which resulted in overall area specific resistance values lower than 20 mΩ cm2 after 100 h exposure at 800°C.

scholarly journals A limiting Current Oxygen Sensor Constituted of (CeO2)0.95(Y2O3)0.05 as Solid Electrolyte Layer and (CeO2)0.75(ZrO2)0.25 as Dense Diffusion Barrier Layer

Sensors ◽  
2019 ◽  
Vol 19 (16) ◽  
pp. 3511
Author(s):  
Wang ◽  
Liu ◽  
Yu
Keyword(s):  
Solid Electrolyte ◽  
Oxygen Concentration ◽  
Barrier Layer ◽  
Diffusion Barrier ◽  
Oxygen Sensor ◽  
Limiting Current ◽  
Long Term Stability ◽  
Diffusion Barrier Layer ◽  
Sensing Characteristics

Using the co-precipitation method to synthesize (CeO2)0.95(Y2O3)0.05 (YDC) and solidreaction method to synthesize (CeO2)0.75(ZrO2)0.25 (ZDC), and the crystal structure, micro-structure,total conductivity and electronic conductivity of the two materials was measured with X-raydiffraction (XRD), scanning electron microscope (SEM), DC van der Pauw and Hebb-Wagnermethods. A limiting current oxygen sensor was prepared with YDC solid electrolyte and a ZDCdense diffusion barrier layer by employing platinum pasting bonding. Sensing characteristics ofthe sensor were obtained at different conditions, including temperature (T), oxygen concentration(x(O2)) and water vapor pressure (p(H2O)), and the influence of various conditions on sensingperformance was studied. The long-term stability of the sensor was measured in an oxygen concentration of 1.2% and at a temperature of 800 °C for 120 h. XRD results show that the phase structure of both YDC and ZDC belongs to the cubic phase. SEM results show that both YDC and ZDC layers are dense layers, which are then qualified to be the composition materials of the sensor. The limiting current (IL) of the sensor is obtained and the sensor exhibits good sensing characteristics to satisfy the Knudsen model. Log(IL·T) depends linearly on 1000/T with a squared correlation coefficient (R2) of 0.9904; IL depends linearly on x(O2) with an R2 of 0.9726; and sensing characteristics are not affected by p(H2O). It was found that the oxygen sensor has good long-term stability.

Optimization of The Processing Parameters for Pulsed Laser Deposition of Nickel Silicide Ohmic Contacts On SiC

2000 ◽  
Vol 617 ◽  
Author(s):  
C. J. K. Richardson ◽  
M. H. Wisnioski ◽  
J. B. Spicer ◽  
J. D. Demaree ◽  
M. W. Cole ◽  
...  
Keyword(s):  
Pulsed Laser Deposition ◽  
Ohmic Contacts ◽  
Pulsed Laser ◽  
Nanocrystalline Structure ◽  
Processing Parameters ◽  
Nickel Silicide ◽  
Laser Deposition ◽  
Surface Roughening ◽  
Nickel Silicon

AbstractThis research investigates the potential of pulsed laser deposition to create reliable high current ohmic contacts of Ni2Si on single crystal 4H-SiC. Since this stoichiometry is the stable interphase in the nickel-silicon carbide diffusion couple, direct deposition eliminates the detrimental excess carbon normally formed by direct sintering Ni on SiC, the surface roughening that results from this sintering as well as the need for post-deposition high-temperature (900°C) anneals that are required in complex multi-component contacts. This study examines the processing parameters that must be used during deposition to obtain the desired microstructural characteristics for the contact. Pulsed laser deposition of nickel silicide produces smooth films with an amorphous or nanocrystalline structure interspersed with macroparticles. Macroparticle formation on the resulting films appear in the form of solidified droplets of the eutectic composition nickel silicide (3:1) that form during the long term target processing. The dependence of the number and size distributions of these droplets on laser fluence sample temperature is examined.

Demonstrating the Instability of SiC Ohmic Contacts and Drain Terminal Metallization Schemes Aged at 300 °C

2017 ◽  
Vol 897 ◽  
pp. 387-390 ◽  
Author(s):  
Dean P. Hamilton ◽  
Steven A. Hindmarsh ◽  
Fan Li ◽  
Michael R. Jennings ◽  
Stephen A.O. Russell ◽  
...  
Keyword(s):  
Ohmic Contacts ◽  
Storage Temperature ◽  
Nickel Silicide ◽  
Silicide Phase ◽  
Contact Metallization ◽  
Thermally Driven ◽  
High Storage Temperature ◽  
Silicide Growth ◽  
High Storage

The long-term thermal stability of the drain contacts of three different commercially available SiC MOSFET devices has been determined at a storage temperature of 300 °C. Existing literature suggests that, at this temperature, the nickel silicides associated with ohmic contact creation should be stable, but this was found not to be the case. Our TEM and EDX work revealed silicide phase transformations, further silicide growth and severe thermally-driven degradation of the drain contact metallization stack on top of the silicide layers. We attribute this instability and growth of the silicides to the high storage temperature and large supply of nickel atoms available from the metal stack. The nickel atoms diffuse and decompose the original silicides to enable the formation of a new low temperature Ni32Si12 phase, and slowly decompose the SiC substrate to form additional nickel silicide.

Formation of the Uniform Interface Ni/4H-SiC Ohmic Contact with Titanium as Barrier Layer

2018 ◽  
Vol 924 ◽  
pp. 397-400
Author(s):  
Moonkyong Na ◽  
In Ho Kang ◽  
Jeong Hyun Moon ◽  
Wook Bahng
Keyword(s):  
Contact Resistance ◽  
Barrier Layer ◽  
Ohmic Contact ◽  
Ohmic Contacts ◽  
Specific Contact Resistance ◽  
Metal Structures ◽  
Uniform Interface ◽  
Specific Contact ◽  
Thermal Annealing Process ◽  
Contact Metal

Nickel (Ni) is the most widely used metal for the formation of ohmic contact on n-type SiC. However, the irregular contact can potentially cause degradation in the device performance. To form the uniform ohmic interface, titanium (Ti) was applied as a barrier layer. Ni/Ti/SiC and Ti/Ni/SiC contact metal structures were prepared, and ohmic contacts were formed using a rapid thermal annealing process. The interfacial properties of both contact metal structures were enhanced by applying the Ti layer. The specific contact resistance of ohmic contacts showed a slightly lower or similar value (~ low 105 Ωcm2) compared with the specific contact resistance values formed from only the Ni contact metal.

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