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Reliable processing of graphene using metal etchmasks.

Kumar S, Peltekis N, Lee K, Kim HY, Duesberg GS - Nanoscale Res Lett (2011)

Bottom Line: We introduce a metal etch mask which minimises these problems.The high quality of graphene is shown by Raman and XPS spectroscopy as well as electrical measurements.The process is of high value for applications, as it improves the processability of graphene using high-throughput lithography and etching techniques.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Chemistry, Trinity College Dublin, Ireland. duesberg@tcd.ie.

ABSTRACT
Graphene exhibits exciting properties which make it an appealing candidate for use in electronic devices. Reliable processes for device fabrication are crucial prerequisites for this. We developed a large area of CVD synthesis and transfer of graphene films. With patterning of these graphene layers using standard photoresist masks, we are able to produce arrays of gated graphene devices with four point contacts. The etching and lift off process poses problems because of delamination and contamination due to polymer residues when using standard resists. We introduce a metal etch mask which minimises these problems. The high quality of graphene is shown by Raman and XPS spectroscopy as well as electrical measurements. The process is of high value for applications, as it improves the processability of graphene using high-throughput lithography and etching techniques.

No MeSH data available.


Schematic of processing for graphene. In first step, graphene is transferred on to suitable substrates and Ni etch mask is created on it in second step. Plasma etching and removal of Ni produced patterned graphene, which is then contacted in the last step using standard liftoff process.
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Figure 2: Schematic of processing for graphene. In first step, graphene is transferred on to suitable substrates and Ni etch mask is created on it in second step. Plasma etching and removal of Ni produced patterned graphene, which is then contacted in the last step using standard liftoff process.

Mentions: The graphene films were now patterned using optical lithography with negative resist followed by ICP plasma etch on an Oxford Instruments Plasmalab 200 in Ar/O2 atmosphere. The etch time ranged from 15 s to 2 min and plasma power between 100 and 500 W. The substrate holder was cooled by helium flow, and a heating of the substrate causing a possible crosslinking of the polymer resist cannot be ruled out. A 30 s treatment in a barrel asher (Diener) under O2 plasma was also tried. {AQ: Please supply missing word or phrase between "with" and "O2" in the sentence, "A barrel asher..." }A range of resist was investigated in our study which included AZ nLOF 2070 (~500 nm), maN-2403 (~ 300 nm) and S1813 (~ 1 μm). Bilayers photoresist masks using AZ nLOF 2070 as top layer and PMMA (450 k) or LOR-10B as bottom layers were also used. As delamination occurred during lift off of these resists, we created a processing procedure using a metal hard mask as shown in Figure 2. The optical images in Figure 3 depict several micron-sized structures formed using the two masks. The adhesion of photoresist to graphene after plasma treatment is stronger than the adhesion of graphene to substrate, which causes graphene to delaminate when photoresist is removed (Figure 3, right). Adhesion of Ni mask with graphene does not present this problem both because Ni removal is a chemical reaction, and interaction of graphene with Ni is not expected to be very different from its interaction with the oxide substrate. The very small D peak in Raman spectrum of etched graphene (Figure 3, left, inset) shows that the impurity concentration is low. This may be attributed to chemical action of acid on organic removing impurities. This observation was made repeatedly in our studies.


Reliable processing of graphene using metal etchmasks.

Kumar S, Peltekis N, Lee K, Kim HY, Duesberg GS - Nanoscale Res Lett (2011)

Schematic of processing for graphene. In first step, graphene is transferred on to suitable substrates and Ni etch mask is created on it in second step. Plasma etching and removal of Ni produced patterned graphene, which is then contacted in the last step using standard liftoff process.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211484&req=5

Figure 2: Schematic of processing for graphene. In first step, graphene is transferred on to suitable substrates and Ni etch mask is created on it in second step. Plasma etching and removal of Ni produced patterned graphene, which is then contacted in the last step using standard liftoff process.
Mentions: The graphene films were now patterned using optical lithography with negative resist followed by ICP plasma etch on an Oxford Instruments Plasmalab 200 in Ar/O2 atmosphere. The etch time ranged from 15 s to 2 min and plasma power between 100 and 500 W. The substrate holder was cooled by helium flow, and a heating of the substrate causing a possible crosslinking of the polymer resist cannot be ruled out. A 30 s treatment in a barrel asher (Diener) under O2 plasma was also tried. {AQ: Please supply missing word or phrase between "with" and "O2" in the sentence, "A barrel asher..." }A range of resist was investigated in our study which included AZ nLOF 2070 (~500 nm), maN-2403 (~ 300 nm) and S1813 (~ 1 μm). Bilayers photoresist masks using AZ nLOF 2070 as top layer and PMMA (450 k) or LOR-10B as bottom layers were also used. As delamination occurred during lift off of these resists, we created a processing procedure using a metal hard mask as shown in Figure 2. The optical images in Figure 3 depict several micron-sized structures formed using the two masks. The adhesion of photoresist to graphene after plasma treatment is stronger than the adhesion of graphene to substrate, which causes graphene to delaminate when photoresist is removed (Figure 3, right). Adhesion of Ni mask with graphene does not present this problem both because Ni removal is a chemical reaction, and interaction of graphene with Ni is not expected to be very different from its interaction with the oxide substrate. The very small D peak in Raman spectrum of etched graphene (Figure 3, left, inset) shows that the impurity concentration is low. This may be attributed to chemical action of acid on organic removing impurities. This observation was made repeatedly in our studies.

Bottom Line: We introduce a metal etch mask which minimises these problems.The high quality of graphene is shown by Raman and XPS spectroscopy as well as electrical measurements.The process is of high value for applications, as it improves the processability of graphene using high-throughput lithography and etching techniques.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Chemistry, Trinity College Dublin, Ireland. duesberg@tcd.ie.

ABSTRACT
Graphene exhibits exciting properties which make it an appealing candidate for use in electronic devices. Reliable processes for device fabrication are crucial prerequisites for this. We developed a large area of CVD synthesis and transfer of graphene films. With patterning of these graphene layers using standard photoresist masks, we are able to produce arrays of gated graphene devices with four point contacts. The etching and lift off process poses problems because of delamination and contamination due to polymer residues when using standard resists. We introduce a metal etch mask which minimises these problems. The high quality of graphene is shown by Raman and XPS spectroscopy as well as electrical measurements. The process is of high value for applications, as it improves the processability of graphene using high-throughput lithography and etching techniques.

No MeSH data available.