A Scalable Clean Graphene Transfer Process Using Polymethylglutarimide as a Support Scaffold

Abstract

Extrinsic scattering related to polymer residue limits the performance of chemical vapor deposited graphene films when transferred to insulating substrates. A clean graphene transfer process has been achieved by employing a support scaffold composed of a polymethylglutarimide (PMGI)-based resist. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) observations confirmed that the amount of residue on large-area transferred graphene was sufficiently reduced by using PMGI scaffolds in comparison to the traditional technique that uses polymethyl methacrylate (PMMA) scaffolds. The root mean square (RMS) roughness values of graphene surfaces using PMMA and PMGI scaffolds were 6.5 nm and 4.0 nm, respectively. This comparison confirms that a cleaner graphene surface was achieved by using PMGI as a support scaffold. Furthermore, Raman spectroscopy suggests that the quality of the transferred graphene was equivalent to that obtained by the traditional method. properties, graphene has drawn intense research interest for its multitude of potential applications. Chemical vapor deposition (CVD) of graphene films on transition metal substrates such as Ni 5 and Cu 6-8 has previously been reported. The CVD technique is capable of depositing high quality graphene films across large areas on Cu substrates. This is due to the low solubility of carbon in Cu, which promotes monolayer growth. However, numerous electronic applications require graphene films directly in contact with insulating substrates like SiO 2 . For this purpose, a graphene transfer technique from a Cu substrate to an insulating substrate has been developed. The standard transfer method uses a poly(methyl methacrylate) (PMMA) scaffold 9-13 on top of the graphene film to act as a support structure during the transfer process. Nevertheless, it is a great challenge to completely remove the PMMA scaffold without resist residue remaining on the transferred graphen. Unlike other semiconductor materials, resist residue on graphene cannot be removed by an ashing process, since this also removes graphene. Attempts to remove residues by high temperature annealing with Ar/H 2 gas 13 and O 2 gas 12 damaged the graphene, and resist residues were inadequately removed using this technique.12 These residues modify the electronic properties of graphene through increased extrinsic scattering and uncontrolled doping. Also, the residues inhibit conformal deposition of metal on graphene, resulting in increased and inconsistent contact resistance. Furthermore, high temperature processing is incompatible with certain graphene applications, such as flexible electronics and biomolecule encapsulation. Thus, a new graphene transfer technique to reduce resist residue without an annealing process is required for future graphene applications.Recently, it has been demonstrated that a clean graphene surface can be obtained after photolithographic processing by using a lift-off resist (LOR) from MicroChem.14 LOR is a resist based on polydimethylglutarimide (PMGI) and is traditiona...

Effects of post-lithography cleaning on the yield and performance of CVD graphene-based devices

“…This can be asserted by the fact that the bands at 1137, 1178, 1300, 1312, 1400, 1410, 1434, 1458 and 1604 cm −1 , shown in Fig. 3, are associated to PMGI polymer [12,14–16]. Thus, the huge increase of the device production using procedure P2 is accompanied by a significant contamination with PMGI during lift-off.…”

“…2). In fact, high-yields have been reported in the literature when PMGI is applied as support scaffold in the transfer of CVD graphene [12–13].…”

Localized optical-quality doping of graphene on silicon waveguides through a TFSA-containing polymer matrix

“…2E) after transferring graphene, due to the monolayer of carbon atoms containing PMMA residues. 72 After spin coating a TFSA/POFPMA layer onto the graphene, the roughness decreased to 0.4 nm/25 mm 2 , corresponding with an optical quality of l/1000 at a wavelength of 400 nm (Fig. 2F).…”

Poly‐Trimethoxyphenylsilane as Carrier Film for Residual‐Free CVD Graphene Transfer

“…The transfer technology is very important for the commercial applications of graphene synthesized on catalytic metal surface by chemical vapor deposition (CVD) method, [1] The most common transfer methods of CVD graphene can be divided into two categories: (i) coating carrier film such as poly(methyl methacrylate) on graphene and chemical etching of metal catalyst [2][3][4] and (ii) controlling adhesion force with substrate using polymer such as polydimethylsiloxane. [5][6][7] In the case of using carrier film, it is possible to transfer the CVD graphene uniformly over a large area, but the metal catalyst residue during etching remains between the wrinkles of the graphene, and the biggest problem is that the polymer itself used as a carrier film is not completely removed.…”

“…The transfer technology is very important for the commercial applications of graphene synthesized on catalytic metal surface by chemical vapor deposition (CVD) method, The most common transfer methods of CVD graphene can be divided into two categories: (i) coating carrier film such as poly(methyl methacrylate) on graphene and chemical etching of metal catalyst and (ii) controlling adhesion force with substrate using polymer such as polydimethylsiloxane …”