Formation of Ohmic Contacts to n-Type 4H-SiC at Low Annealing Temperatures

2018 ◽  
Vol 924 ◽  
pp. 413-416 ◽  
Author(s):  
Vinoth Kumar Sundaramoorthy ◽  
Renato Amaral Minamisawa ◽  
Lukas Kranz ◽  
Lars Knoll ◽  
Giovanni Alfieri
Keyword(s):  
Ohmic Contacts ◽  
Annealing Temperature ◽  
Xrd Analysis ◽  
Nickel Silicide ◽  
Silicide Phase ◽  
Metal Contacts ◽  
Dopant Segregation ◽  
Annealing Temperatures ◽  
A Value ◽  
Specific Contact

The formation of Ohmic contacts to n-type 4H-SiC layers at low annealing temperature using dopant segregation technique is reported. n-SiC epilayer was implanted with phosphorous and subsequently activated at 1700 °C. Ni metal contacts fabricated on phosphorous implanted and annealed epilayers produced Ohmic contacts with a specific contact resistivity (ρc) of ~7.2x10-5 Ω.cm2 at an annealing temperature of 550 °C. ρc decreased with further annealing temperature reaching a value of ~2.1x10-5 Ω.cm2 at 1000 °C. XRD analysis showed that nickel silicide phase was formed at both 550 °C and 1000 °C.

Improvement of the Specific Contact Resistance on P-Type 4H-SiC by Using a Highly P-Typed Doped 4H-SiC Layer Selectively Grown by VLS Transport

2014 ◽  
Vol 806 ◽  
pp. 57-60
Author(s):  
Nicolas Thierry-Jebali ◽  
Arthur Vo-Ha ◽  
Davy Carole ◽  
Mihai Lazar ◽  
Gabriel Ferro ◽  
...  
Keyword(s):  
Contact Resistance ◽  
Ohmic Contacts ◽  
Schottky Barrier Height ◽  
Annealing Temperature ◽  
Process Condition ◽  
Specific Contact Resistance ◽  
High Doping Level ◽  
Annealing Temperatures ◽  
Specific Contact ◽  
P Type

This work reports on the improvement of ohmic contacts made on heavily p-type doped 4H-SiC epitaxial layer selectively grown by Vapor-Liquid-Solid (VLS) transport. Even before any annealing process, the contact is ohmic. This behavior can be explained by the high doping level of the VLS layer (Al concentration > 1020 cm-3) as characterized by SIMS profiling. Upon variation of annealing temperatures, a minimum value of the Specific Contact Resistance (SCR) down to 1.3x10-6 Ω.cm2 has been obtained for both 500 °C and 800 °C annealing temperature. However, a large variation of the SCR was observed for a same process condition. This variation is mainly attributed to a variation of the Schottky Barrier Height.

Nano-Electro-Structural Evolution of Ni-Si Ohmic Contacts to 3C-SiC

2009 ◽  
Vol 615-617 ◽  
pp. 569-572
Author(s):  
Jens Eriksson ◽  
Fabrizio Roccaforte ◽  
Filippo Giannazzo ◽  
Raffaella Lo Nigro ◽  
Giuseppe Moschetti ◽  
...  
Keyword(s):  
Ohmic Contacts ◽  
Annealing Temperature ◽  
Structural Evolution ◽  
Electrical Characterization ◽  
Nickel Silicide ◽  
Specific Contact Resistance ◽  
Specific Contact ◽  
Nanoscale Measurements

This paper reports on the macro- and nanoscale electro-structural evolution, as a function of annealing temperature, of nickel-silicide Ohmic contacts to 3C-SiC, grown on 6H-SiC substrates by a Vapor-Liquid-Solid (VLS) technique. The structural and electrical characterization of the contacts, carried out by combining different techniques, showed a correlation between the annealing temperature and the electrical characteristics in both the macro- and the nanoscale measurements. Increasing the annealing temperature between 600 and 950 °C caused a gradual increase of the uniformity of the nanoscale current-distribution, with an accompanying reduction of the specific contact resistance from 5 x 10-5 to 8.4 x 10-6 Ωcm2. After high temperature annealing (950 °C) the structural composition of the contacts stabilized, as only the Ni2Si phase was detected. A comparison with previous literature findings suggests a superior crystalline quality of the single domain VLS 3C-SiC layers.

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

2000 ◽  
Vol 640 ◽  
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.

scholarly journals Ohmic contacts to Si-implanted and un-implanted n-type GaN

1995 ◽  
Vol 395 ◽  
Author(s):  
J. Brown ◽  
J Ramer ◽  
K. ZHeng ◽  
L.F. Lester ◽  
S.D. Hersee ◽  
...  
Keyword(s):  
Contact Resistance ◽  
Ohmic Contacts ◽  
Annealing Temperature ◽  
Contact Resistivity ◽  
Contact Structures ◽  
Specific Contact Resistance ◽  
Resistance Variation ◽  
Specific Contact ◽  
Metal Layers ◽  
Nitrogen Vacancies

ABSTRACTWe report on ohmic contacts to Si-implanted and un-implanted n-type GaN on sapphire. A ring shaped contact design avoids the need to isolate the contact structures by additional implantation or etching. Metal layers of Al and Ti/Al were investigated. On un-implanted GaN, post metalization annealing was performed in an RTA for 30 seconds in N2 at temperatures of 700, 800, and 900°C, A minimum specific contact resistance (rc) of 1.4×10−5 Ω-cm2 was measured for Ti/Al at an annealing temperature of 800°C. Although these values are reasonably low, variations of 95% in specific contact resistance were measured within a 500 µm distance on the wafer. These results are most likely caused by the presence of compensating hydrogen. Specific contact resistance variation was reduced from 95% to 10% by annealing at 900°C prior to metalization. On Si-implanted GaN, un-annealed ohmic contacts were formed with Ti/Al metalization. The implant activation anneal of 1120°C generates nitrogen vacancies that leave the surface heavily n-type, which makes un-annealed ohmic contacts with low contact resistivity possible.

A Comparative Optimization of Electrical Properties and Surface Morphology of Ti/Al/Ta/Au Ohmic Contacts in AlGaN/GaN HEMTs on Si(111), Sapphire, 4H-SiC Substrates

2012 ◽  
Vol 538-541 ◽  
pp. 2207-2210
Author(s):  
Sung Jin Cho ◽  
Cong Wang ◽  
Nam Young Kim
Keyword(s):  
Surface Morphology ◽  
Sapphire Substrate ◽  
Ohmic Contact ◽  
Annealing Time ◽  
Ohmic Contacts ◽  
Annealing Temperature ◽  
Contact Process ◽  
Annealing Temperatures ◽  
Ohmic Resistance ◽  
Gan Hemts

In the process of characterizing AlGaN/GaN HEMTs on Si (111), Sapphire, 4H-SiC substrates, various Rapid Thermal Annealing (RTA) conditions for the Ti/Al/Ta/Au ohmic contact process and the resulting surface analysis have been investigated. In order to achieve a low ohmic contact resistance (RC) and a high quality surface morphology, we tested seven steps (800 °C to 920 °C) annealing temperatures and two steps (15, 30 sec) annealing times. According to these annealing temperatures and times, the optimal ohmic resistance of 3.62 × 10-6 Ohm • cm2 on Si(111) substrate, 9.44 × 10-6 Ohm • cm2 on Sapphire substrate and 1.24 × 10-6 Ohm • cm2 on 4H-SiC substrate are obtained at an annealing temperature of 850 °C and an annealing time of 30 sec, 800 °C and an annealing time of 30 sec and 900 °C and an annealing time of 30 sec, respectively. The surface morphologies of the ohmic contact metallization at different annealing temperatures are measured using an Atomic Force Microscope (AFM). AFM morphology Root Mean Square (RMS) level determines the relationship of the annealing temperature and the annealing time for all of the samples. According to these annealing temperatures and times, the optimal ohmic surface RMS roughness of 13.4 nm on Si(111) substrate, 3.8 nm on Sapphire substrate and 2.9 nm on 4H-SiC substrate are obtained at an annealing temperature of 850 °C and an annealing time of 30 sec, 800 °C and an annealing time of 30 sec and 900 °C and an annealing time of 30 sec, respectively.

Low Resistance Ohmic Contacts Formation and Mechanism of Current Transport Through p-GaN and p-AlGaN

2008 ◽  
Vol 1108 ◽  
Author(s):  
Indra Chary ◽  
Boris Borisov ◽  
Vladimir Kuryatkov ◽  
Yuriy Kudryavtsev ◽  
R Asomoza ◽  
...  
Keyword(s):  
Ohmic Contact ◽  
Ohmic Contacts ◽  
Annealing Temperature ◽  
Hole Concentration ◽  
Specific Contact Resistance ◽  
Current Transport ◽  
Bilayer Thickness ◽  
Aluminum Oxides ◽  
Mg Doping ◽  
Specific Contact

AbstractWe report the influence of surface treatment, annealing temperature and metal bilayer thickness on the specific contact resistance (ρc) of Au/Ni ohmic contacts to p-GaN and p-AlGaN. Ohmic contact on p-GaN with a hole concentration of 6.5 x 1017 cm-3, shows the lowest ρc of ˜9.2 x 10-6 Ω cm2, when GaN was treated in HCl:H2O (3:1) solution before metal deposition and annealed at 500°C for 10 minutes in 90% N2 and 0% O2 atmosphere. Similar procedure applied on p-AlxGa1-xN (x = 5-7%), with a hole concentration of 2.3 x 1017 cm-3, yields a ρc of 1.8 x 10-4 Ω cm2. An increase is observed in ρc when Mg doping exceeds 4 x 1019 cm-3 in both p-GaN and p-AlGaN. This is attributed to Mg self compensation. This increase is more pronounced in AlGaN which we attribute to the presence of residual native aluminum oxides.

Aluminum Doping by Low-Temperature Homoepitaxial Growth for Ni Ohmic Contacts to p-Type 4H-SiC

2009 ◽  
Vol 615-617 ◽  
pp. 581-584 ◽  
Author(s):  
Bharat Krishnan ◽  
Siva Prasad Kotamraju ◽  
Galyna Melnychuk ◽  
Neil Merrett ◽  
Yaroslav Koshka
Keyword(s):  
Low Temperature ◽  
Epitaxial Growth ◽  
Ohmic Contacts ◽  
Specific Contact Resistance ◽  
Metal Contacts ◽  
Atomic Concentration ◽  
Homoepitaxial Growth ◽  
Specific Contact ◽  
Sio2 Mask ◽  
P Type

Low-temperature halo-carbon homoepitaxial growth is suitable for selective epitaxial growth of 4H-SiC using SiO2 mask. A possibility of achieving high values of doping in combination with the selective growth makes it an alternative to ion implantation for selective doping in SiC. In this work, TMA doping in situ during a blanket low-temperature epitaxial growth was utilized to produce heavily Al doped SiC layers for Ohmic contact formation to p-type SiC. Nearly featureless epilayer morphology with Al atomic concentration exceeding 3x1020 cm-3 was obtained after growth at 13000C with the growth rate of 1.5 µm/hr. Ni TLM contacts with a thin adhesion layer of Ti were formed. The as-deposited metal contacts were almost completely Ohmic even before annealing. The specific contact resistance of 2x10-2 Ohm-cm2 and 6x10-5 Ohms-cm2 was achieved without and with contact annealing respectively. The resistivity of the epitaxial layers better than 0.01 Ohm cm was measured for Al atomic concentration of 2.7x1020 cm-3.

The Effects of Thermal Processing on Interfacial Microstructure for Thin Multilayered Metal Ohmic Contacts to p+-AlGaAs

1995 ◽  
Vol 382 ◽  
Author(s):  
M.W. Cole ◽  
W.Y. Han ◽  
K.A. Jones
Keyword(s):  
Ohmic Contacts ◽  
Annealing Temperature ◽  
Chemical Diffusion ◽  
Interfacial Microstructure ◽  
Specific Contact Resistance ◽  
Interfacial Region ◽  
Electrical Measurements ◽  
Two Phase ◽  
Specific Contact ◽  
P Type

ABSTRACTInterfacial microstructure and phase composition of PtTiGePd ohmic contacts to heavily C doped AlGaAs were investigated as a function of annealing temperature. Results of the material analyses were used to explain the specific contact resistances measured for each thermal treatment. Evidence of interdiffusion and compound formation between AIGaAs and Pd was visible in a Ga rich Pd-Ga-As reaction zone prior to heat treatment. This phase is critical for the formation of Ga vacancies, which upon heating are occupied by in-diffusing Ge. As the annealing temperature was elevated, from 530 - 600°C, As began to out-diffuse. This As out-diffusion, which is critical to the formation of good p-type ohmic contacts, contributed to the creation and development of the two phase TiAs/Pd12Ga2Ge5 interfacial region overlying the AlGaAs substrate. In response to the enhanced As out-diffusion at 600°C, the interfacial region became laterally continuous, compositionally uniform, and the specific contact resistance achieved its minimum value. Athigher annealing temperatures, ∼650°C, the electrical measurements degraded in response to intensive chemical diffusion and development of a broad, non-uniform multi-phased interfacial region.

Electrical Properties of (Zn, Mn) Containing Multilayer Metallizations to p-Type InGaAs/InP

1995 ◽  
Vol 382 ◽  
Author(s):  
Patrick W. Leec ◽  
Geoffrey K. Reeves ◽  
Wei Zhou
Keyword(s):  
Electrical Properties ◽  
Contact Resistance ◽  
Layer Thickness ◽  
Annealing Temperature ◽  
Specific Contact Resistance ◽  
Annealing Temperatures ◽  
Specific Contact ◽  
A Minor ◽  
P Type ◽  
Metal Layers

ABSTRACTThe specific contact resistance, pc, of Au/Zn/Au, Ni/Zn/Ni/Au, Pd/Zn/Pt/Au and Pd/Mln/Sb/Pd/Au contacts to p-In0.47Ga0.53As/ InP has been measured as a function of layer thickness of Zn or Mn. All of the as-deposited contacts were ohmic, with pc = 1−2 × 10−5 Ω cm2. Increasing thickness of the Zn layer above 200 Å in the Au/Zn/Au contacts resulted in a minor decrease in pc while producing no change in the Ni/Zn/Ni/Au metallization. For the as-deposited Pd/Mn/Pd/Au contacts, the value of pc was independent of thickness of the Mn layer but differences in pc emerged at annealing temperatures of ≥ 250°. The analysis of these structures by RBS has shown an extensive intermixing of the metal layers at an annealing temperature of 450 °. In the Pd/Zn/Pt/Au contacts, the value of pc was reduced to a minimum value of 8 × 10−6 Ω cm2 by annealing at a temperature of 500 °. An examination of the Pd/Zn/Pt/Au configuration by RBS has shown that the Pt layer acted as a barrier for the indiffusion of the Au.

Thermal Stability of Ohmic Contacts to n-InxGa1−xN

1995 ◽  
Vol 395 ◽  
Author(s):  
A. Duibha ◽  
S. J. Pearton ◽  
C. R. Abernathy ◽  
J. W. Lee ◽  
P. H. Holloway ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Electron Spectroscopy ◽  
Ohmic Contacts ◽  
Electrical Characteristics ◽  
Microstructural Properties ◽  
Excellent Thermal Stability ◽  
Annealing Temperatures ◽  
Specific Contact ◽  
Specific Contact Resistivity ◽  
Thermal Stability Of

ABSTRACTThe microstructural properties and interdiffusion reactions of Au/Ge/Ni, Ti/Pt/Au, WSix and AuBe contacts on GaN and In0.5Ga0.5N have been examined using Scanning Electron Microscopy and Auger Electron Spectroscopy. The WSix contacts possess excellent thermal stability and retained good structural properties at annealing temperatures as high as 800°C on GaN. The electrical characteristics of WSix contacts on In0.5Ga0.5N had a specific contact resistivity of 1.48×10−5Ωcm2 and an excellent surface morphology following annealing at 700°C. The increase in contact resistance observed at higher temperatures was attributed to intermixing of metal and semiconductor. In contrast the Ti/Pt/Au and Au/Ge/Ni contacts were stable only to ≤ 500°C. AuBe contacts had the poorest thermal stability, with substantial reaction with GaN occurring even at 400°C. The WSix contact appears to be an excellent choice for high temperature GaN electronics applications.

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