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Near-surface processing on AlGaN/GaN heterostructures: a nanoscale electrical and structural characterization.

Greco G, Giannazzo F, Frazzetto A, Raineri V, Roccaforte F - Nanoscale Res Lett (2011)

Bottom Line: In particular, a CHF3-based plasma process in the gate region resulted in a shift of the threshold voltage in HEMT devices towards less negative values.Two-dimensional current maps acquired by C-AFM on the sample surface allowed us to monitor the local electrical modifications induced by the plasma fluorine incorporated in the material.The results are compared with a recently introduced gate control processing: the local rapid thermal oxidation process of the AlGaN layer.By this process, a controlled thin oxide layer on surface of AlGaN can be reliably introduced while the resistance of the layer below increase locally.

View Article: PubMed Central - HTML - PubMed

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

ABSTRACT
The effects of near-surface processing on the properties of AlGaN/GaN heterostructures were studied, combining conventional electrical characterization on high-electron mobility transistors (HEMTs), with advanced characterization techniques with nanometer scale resolution, i.e., transmission electron microscopy, atomic force microscopy (AFM) and conductive atomic force microscopy (C-AFM). In particular, a CHF3-based plasma process in the gate region resulted in a shift of the threshold voltage in HEMT devices towards less negative values. Two-dimensional current maps acquired by C-AFM on the sample surface allowed us to monitor the local electrical modifications induced by the plasma fluorine incorporated in the material.The results are compared with a recently introduced gate control processing: the local rapid thermal oxidation process of the AlGaN layer. By this process, a controlled thin oxide layer on surface of AlGaN can be reliably introduced while the resistance of the layer below increase locally.

No MeSH data available.


Related in: MedlinePlus

C-AFM scans. Schematic of the C-AFM measurement setup (a) used to measure conductivity changes in a sample locally treated with CHF3 plasma (on lithographically defined stripes) and annealed at 400°C. AFM morphology (b) and C-AFM transversal current map (c) of the sample.
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Figure 4: C-AFM scans. Schematic of the C-AFM measurement setup (a) used to measure conductivity changes in a sample locally treated with CHF3 plasma (on lithographically defined stripes) and annealed at 400°C. AFM morphology (b) and C-AFM transversal current map (c) of the sample.

Mentions: In order to monitor the local electrical modification induced by the plasma treatment on the 2DEG, and corroborate the previous hypothesis, a nanoscale characterization approach was adopted. For this purpose C-AFM scans were performed on appropriate samples, in which the plasma treatments were performed in selected regions. In particular, resist stripes were defined on the sample surface by means of optical lithography, in order to selectively expose the sample surface to CHF3 process. The transversal current between the nanometric tip contact and the sample backside was measured by a high sensitivity current sensor in series with the tip, as illustrated in Figure 4a.


Near-surface processing on AlGaN/GaN heterostructures: a nanoscale electrical and structural characterization.

Greco G, Giannazzo F, Frazzetto A, Raineri V, Roccaforte F - Nanoscale Res Lett (2011)

C-AFM scans. Schematic of the C-AFM measurement setup (a) used to measure conductivity changes in a sample locally treated with CHF3 plasma (on lithographically defined stripes) and annealed at 400°C. AFM morphology (b) and C-AFM transversal current map (c) of the sample.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211179&req=5

Figure 4: C-AFM scans. Schematic of the C-AFM measurement setup (a) used to measure conductivity changes in a sample locally treated with CHF3 plasma (on lithographically defined stripes) and annealed at 400°C. AFM morphology (b) and C-AFM transversal current map (c) of the sample.
Mentions: In order to monitor the local electrical modification induced by the plasma treatment on the 2DEG, and corroborate the previous hypothesis, a nanoscale characterization approach was adopted. For this purpose C-AFM scans were performed on appropriate samples, in which the plasma treatments were performed in selected regions. In particular, resist stripes were defined on the sample surface by means of optical lithography, in order to selectively expose the sample surface to CHF3 process. The transversal current between the nanometric tip contact and the sample backside was measured by a high sensitivity current sensor in series with the tip, as illustrated in Figure 4a.

Bottom Line: In particular, a CHF3-based plasma process in the gate region resulted in a shift of the threshold voltage in HEMT devices towards less negative values.Two-dimensional current maps acquired by C-AFM on the sample surface allowed us to monitor the local electrical modifications induced by the plasma fluorine incorporated in the material.The results are compared with a recently introduced gate control processing: the local rapid thermal oxidation process of the AlGaN layer.By this process, a controlled thin oxide layer on surface of AlGaN can be reliably introduced while the resistance of the layer below increase locally.

View Article: PubMed Central - HTML - PubMed

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

ABSTRACT
The effects of near-surface processing on the properties of AlGaN/GaN heterostructures were studied, combining conventional electrical characterization on high-electron mobility transistors (HEMTs), with advanced characterization techniques with nanometer scale resolution, i.e., transmission electron microscopy, atomic force microscopy (AFM) and conductive atomic force microscopy (C-AFM). In particular, a CHF3-based plasma process in the gate region resulted in a shift of the threshold voltage in HEMT devices towards less negative values. Two-dimensional current maps acquired by C-AFM on the sample surface allowed us to monitor the local electrical modifications induced by the plasma fluorine incorporated in the material.The results are compared with a recently introduced gate control processing: the local rapid thermal oxidation process of the AlGaN layer. By this process, a controlled thin oxide layer on surface of AlGaN can be reliably introduced while the resistance of the layer below increase locally.

No MeSH data available.


Related in: MedlinePlus