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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 of the Al+-implanted and annealed 4H-SiC surface. (a) Sample annealed at 1700°C without a protective carbon capping layer. (b) Sample annealed at 1700°C with a protective carbon capping layer.
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Figure 2: AFM images of the Al+-implanted and annealed 4H-SiC surface. (a) Sample annealed at 1700°C without a protective carbon capping layer. (b) Sample annealed at 1700°C with a protective carbon capping layer.

Mentions: Figure 2 shows the AFM scans taken over the same area of 20 × 20 μm2 for the sample annealed at 1700°C without or with a protective capping layer (Figure 2a,b). While after high-temperature thermal treatment a significant increase of the surface roughness occurs in the sample annealed without capping layer, determined by the appearance of the typical step bunching on the surface (Figure 2a), the morphology of the sample annealed with a capping layer (Figure 2b) does not exhibit such a surface degradation, and only a slight increase of the roughness with respect to the as-implanted sample is observed. In particular, values of the RMS for the samples annealed at 1700°C without and with the protective carbon capping layer were 18.9 and 2.3 nm, respectively.


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 of the Al+-implanted and annealed 4H-SiC surface. (a) Sample annealed at 1700°C without a protective carbon capping layer. (b) Sample annealed at 1700°C with a protective carbon capping layer.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 2: AFM images of the Al+-implanted and annealed 4H-SiC surface. (a) Sample annealed at 1700°C without a protective carbon capping layer. (b) Sample annealed at 1700°C with a protective carbon capping layer.
Mentions: Figure 2 shows the AFM scans taken over the same area of 20 × 20 μm2 for the sample annealed at 1700°C without or with a protective capping layer (Figure 2a,b). While after high-temperature thermal treatment a significant increase of the surface roughness occurs in the sample annealed without capping layer, determined by the appearance of the typical step bunching on the surface (Figure 2a), the morphology of the sample annealed with a capping layer (Figure 2b) does not exhibit such a surface degradation, and only a slight increase of the roughness with respect to the as-implanted sample is observed. In particular, values of the RMS for the samples annealed at 1700°C without and with the protective carbon capping layer were 18.9 and 2.3 nm, respectively.

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