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Nanoscale electro-structural characterisation of ohmic contacts formed on p-type implanted 4H-SiC.

Frazzetto A, Giannazzo F, Lo Nigro R, Di Franco S, Bongiorno C, Saggio M, Zanetti E, Raineri V, Roccaforte F - Nanoscale Res Lett (2011)

Bottom Line: In particular, the surface roughness of the Al-implanted SiC regions annealed at 1700°C could be strongly reduced using a protective carbon capping layer during annealing.This latter resulted in an improved surface morphology and specific contact resistance of the Ti/Al ohmic contacts formed on these regions.The microstructure of the contacts was monitored by X-ray diffraction analysis and a cross-sectional transmission electron microscopy, and correlated with the electrical results.

View Article: PubMed Central - HTML - PubMed

Affiliation: Consiglio Nazionale delle Ricerche-Istituto per la Microelettronica e Microsistemi-Strada VIII, n, 5, Zona Industriale, 95121, Catania, Italy. fabrizio.roccaforte@imm.cnr.it.

ABSTRACT
This work reports a nanoscale electro-structural characterisation of Ti/Al ohmic contacts formed on p-type Al-implanted silicon carbide (4H-SiC). The morphological and the electrical properties of the Al-implanted layer, annealed at 1700°C with or without a protective capping layer, and of the ohmic contacts were studied using atomic force microscopy [AFM], transmission line model measurements and local current measurements performed with conductive AFM.The characteristics of the contacts were significantly affected by the roughness of the underlying SiC. In particular, the surface roughness of the Al-implanted SiC regions annealed at 1700°C could be strongly reduced using a protective carbon capping layer during annealing. This latter resulted in an improved surface morphology and specific contact resistance of the Ti/Al ohmic contacts formed on these regions. The microstructure of the contacts was monitored by X-ray diffraction analysis and a cross-sectional transmission electron microscopy, and correlated with the electrical results.

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AFM images and C - AFM current map for samples annealed without a protective carbon capping layer. Surface morphology (a) and C-AFM current map (b) on a contact Ti/Al fabricated on the Al+-implanted 4H-SiC surface and annealed at 1700°C without a protective carbon capping layer.
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Figure 4: AFM images and C - AFM current map for samples annealed without a protective carbon capping layer. Surface morphology (a) and C-AFM current map (b) on a contact Ti/Al fabricated on the Al+-implanted 4H-SiC surface and annealed at 1700°C without a protective carbon capping layer.

Mentions: The morphology of the Ti/Al ohmic contacts formed on these implanted regions and their local electrical properties were evaluated by AFM and C-AFM. Figures 3a and 4a show the AFM images for the samples annealed with and without a protective carbon capping layer, respectively. As can be seen, the Ti/Al annealed contacts are characterised by a high surface roughness, which in turn can be associated with the original morphology of the underlying SiC. In fact, the higher the original SiC surface roughness, the higher is the roughness of the annealed Ti/Al contacts formed on the top of this region. The RMS values of the Ti/Al annealed contacts, deduced from the AFM images, were 22 and 44 nm, respectively, for the sample annealed with and without the capping layer.


Nanoscale electro-structural characterisation of ohmic contacts formed on p-type implanted 4H-SiC.

Frazzetto A, Giannazzo F, Lo Nigro R, Di Franco S, Bongiorno C, Saggio M, Zanetti E, Raineri V, Roccaforte F - Nanoscale Res Lett (2011)

AFM images and C - AFM current map for samples annealed without a protective carbon capping layer. Surface morphology (a) and C-AFM current map (b) on a contact Ti/Al fabricated on the Al+-implanted 4H-SiC surface and annealed at 1700°C without a protective carbon capping layer.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211209&req=5

Figure 4: AFM images and C - AFM current map for samples annealed without a protective carbon capping layer. Surface morphology (a) and C-AFM current map (b) on a contact Ti/Al fabricated on the Al+-implanted 4H-SiC surface and annealed at 1700°C without a protective carbon capping layer.
Mentions: The morphology of the Ti/Al ohmic contacts formed on these implanted regions and their local electrical properties were evaluated by AFM and C-AFM. Figures 3a and 4a show the AFM images for the samples annealed with and without a protective carbon capping layer, respectively. As can be seen, the Ti/Al annealed contacts are characterised by a high surface roughness, which in turn can be associated with the original morphology of the underlying SiC. In fact, the higher the original SiC surface roughness, the higher is the roughness of the annealed Ti/Al contacts formed on the top of this region. The RMS values of the Ti/Al annealed contacts, deduced from the AFM images, were 22 and 44 nm, respectively, for the sample annealed with and without the capping layer.

Bottom Line: In particular, the surface roughness of the Al-implanted SiC regions annealed at 1700°C could be strongly reduced using a protective carbon capping layer during annealing.This latter resulted in an improved surface morphology and specific contact resistance of the Ti/Al ohmic contacts formed on these regions.The microstructure of the contacts was monitored by X-ray diffraction analysis and a cross-sectional transmission electron microscopy, and correlated with the electrical results.

View Article: PubMed Central - HTML - PubMed

Affiliation: Consiglio Nazionale delle Ricerche-Istituto per la Microelettronica e Microsistemi-Strada VIII, n, 5, Zona Industriale, 95121, Catania, Italy. fabrizio.roccaforte@imm.cnr.it.

ABSTRACT
This work reports a nanoscale electro-structural characterisation of Ti/Al ohmic contacts formed on p-type Al-implanted silicon carbide (4H-SiC). The morphological and the electrical properties of the Al-implanted layer, annealed at 1700°C with or without a protective capping layer, and of the ohmic contacts were studied using atomic force microscopy [AFM], transmission line model measurements and local current measurements performed with conductive AFM.The characteristics of the contacts were significantly affected by the roughness of the underlying SiC. In particular, the surface roughness of the Al-implanted SiC regions annealed at 1700°C could be strongly reduced using a protective carbon capping layer during annealing. This latter resulted in an improved surface morphology and specific contact resistance of the Ti/Al ohmic contacts formed on these regions. The microstructure of the contacts was monitored by X-ray diffraction analysis and a cross-sectional transmission electron microscopy, and correlated with the electrical results.

No MeSH data available.


Related in: MedlinePlus