Layer by Layer Etching of the Highly Oriented Pyrolythic Graphite by Using Atomic Layer Etching

Abstract

The layers of exfoliation graphene obtained by scotch taping of highly oriented pyrolythic graphite could be controlled precisely using an atomic layer etching (ALET) technology. Using the ALET, that is, by adsorbing oxygen radicals chemically on the graphene surface during the adsorption step and by removing the chemisorbed species only by Ar particle beam irradiation during the desorption step, exactly one monolayer of graphene could be removed during each etch cycle. The removal of each graphene layer by each ALET etch cycle could be observed through the optical microscope. In addition, the decrease of graphene layers could be also observed through the peak position change/broadening of G Raman peak. However, after the ALET, physical damage on the graphene surface could be also observed by the increase of D peak and decrease of G peak using the Raman spectra. The damaged graphene could be partially recovered by annealing at 1000 • C for 30 minutes in 130 mTorr H 2 /He environment.Recent ITRS (International Technology Roadmap for Semiconductors) roadmap shows that materials such as graphene, Ge, III-V semiconductor, and carbon nanotubes are emerging research device materials for the next generation devices which can replace silicon materials to decrease power consumption and to improve the performance of the device. 1 Among these materials, graphene which is composed of one or a few layers of carbon atoms with two dimensional hexagonal arrangement is investigated the most as the high speed semiconductor device materials because it has a high mobility of 3000 ∼ 27000 cm 2 /Vs at room temperature and a high conductivity. 2 Most of the graphene is fabricated by exfoliation of graphite crystal 3 or by chemical vapor deposition (CVD). 4 Among these, the exfoliation graphene which is obtained from highly oriented pyrolythic graphite (HOPG) flake is high quality graphene and shows higher mobility compared to the graphene grown by CVD, therefore, it is studied by many researchers as the ideal material for the investigation of the next generation graphene devices such as field effect transistor, 5 gas-sensor, 6 bio-sensor, 7 etc. Especially, the decrease of graphene layers from multilayer to monolayer decreases the interlayer scattering, and which increases the mobility sharply by the current modulation 8 and changes band structure. 9 Therefore, the control of the number of graphene layers is one of the important factors in controlling the electrical properties of graphene and the technique in controlling the graphene layer needs to be investigated.The number of layers has been controlled by growing and stacking the monolayer CVD graphenes on a separate substrate, 4 or by etching the graphene by O 2 plasma, 10 or by removing the graphene layers through the oxidation at a high temperature, 11 etc. However, these methods are difficult to control the layers of graphene precisely and locally which is beneficial in fabricating graphene devices. Recently, a technique to remove a monolayer graphene only on a local area by sele...

Overview of atomic layer etching in the semiconductor industry

“…These include electron cyclotron resonance plasma, 33,39,56,62,86,87 helicon source plasma, 49,88 TCP, 6 capacitively coupled plasma, 5,60,89 and inductively coupled plasma. 90 Other types of energetic species have also been evaluated, including ion beams, 40,48 neutral beams, 35,[50][51][52]68,69,83,[91][92][93][94][95][96] and laser beams. 32,66,67,97,98 While specialized equipment certainly plays an integral part in basic understanding of ALE, it may be more practical to adapt conventional etching equipment for use in ALE.…”

“…122 Removal of a controlled number of layers has been demonstrated using ALE on graphene and graphene-like materials. 92,93,123 A highly publicized report of graphene ALE appeared in Science magazine in 2011. 123 In this report, Dimiev et al used zinc deposited by sputtering onto the top layer of graphene, as represented in Fig.…”

“…41,123 Graphene was also studied with directional ALE, using oxygen atoms from plasma to form the reactive layer on the uppermost graphene layer, followed by an Ar neutral beam, removing one monolayer of graphene in each cycle. 92,93 Besides graphene, directional ALE has also been successful on other potential 2D supermaterials, such as transition-metal dichalcogenide semiconductor (MoS 2 ). 63 Polymer surfaces were explored with ALE by Vogli et al on a polystyrene-based polymer, where a modified surface was produced by exposing polymer surface to oxygen gas (O 2 ) (reaction A).…”

Atomic Layer Etching at the Tipping Point: An Overview

“…They also discussed graphene damage issues, and damage annealing. Similarly, Kim et al 75 applied this approach to etching of graphite, and measured removal of 1 monolayer per etching cycle. On the other hand, Min et al 77 report HfO 2 etching using Cl 2 and neutral Ar beam etching at less than 1.0 A/cycle, with high selectivity against an SiO 2 underlayer.…”

Controlled Layer-by-Layer Etching of MoS2

“…Recently, the use of argon (Ar) plasma to conduct the layer-by-layer etching of MoS 2 has been investigated by Liu et al, Previously, in the etching of various semiconducting materials, the atomic layer etching technique (ALET) has shown promising results for next-generation devices due to characteristics such as precise atomic-scale control of the etch depth, extreme uniformity over a large wafer area, and low levels of damage and contamination. 23,24,25,26 In this research, we propose the ALET as a precise layer-by-layer etching technique for 2-D MoS 2 material.…”