# Experiment Research on Micro-/Nano Processing Technology of Graphite as Basic MEMS Material
## 1 Introduction  
With the continuous maturity of micro-/nanoprocessing technology, microelectromechanical systems (MEMS) with silicon as the basic material have been rapidly developed, and are used in aviation, biological, medical, and other fields [1; 2; 3]. Moreover, researchers are investigating new basic MEMS materials to meet the special needs of different applications. For example, flexible materials such as polydimethylsiloxane and polyimide film have been investigated and used as basic materials in preparing flexible and wearable MEMS devices [4; 5; 6]. High tensile-strength material has also been invented, such as the nickel-molybdenum-tungsten alloy, which is a strong material invented by [PERSON]'s team at Johns Hopkins University. It has good tensile and high-temperature resistance to meet the demand for MEMS to work in harsh environments [7]. With the continuous expansion of the scope and field of MEMS applications, researching for new basic MEMS materials, suitable for different application fields, is receiving increasing attention. Graphite is a globally abundant mineral. It is a crystalline carbon with a hexagonal-layered-structure crystal lattice, each layer has the single-atom thickness of graphene [8]. This structure gives graphite excellent characteristics, such as conductivity, heat conduction,high-temperature resistance, radiation resistance, and good chemical stability. For example, [PERSON] et al. found that superlubricity characteristics exist between micron-sized graphite layers in the atmosphere [9]. Moreover, they illustrated the importance of superlubricity characteristic in future technological applications, such as durable nano- and micro-electromechanical devices and mechanical bearings [10]. The other important characteristics such as conductivity and good chemical stability, have made graphite an important material for electrodes in the field of fuel cells [11]. The above characteristics may enable graphite become an important choice for basic MEMS materials and contribute to graphite-based MEMS to work under harsh conditions, such as in chemical corrosion, friction, and wear. However, micro-/nanoprocessing technology is the main method to fabricate MEMS devices. Therefore, graphite needs to meet the requirements of micro-/nanoprocessing technology to become a basic MEMS material. At present, Carbon-MEMS have been proposed and studied, [PERSON] et al. [12] proposes a method of mixing polyimide with nano-graphite particle additive to increase the releasing rate of sacrificial layer. [PERSON] et al. [13; 14; 15] fabricated C-MEMS/NEMS structure by pyrolysis of photoresists on silicon wafers at temperatures ranging from 600 to 1100 \({}^{\circ}\)C. Other researchers have used plasma-enhanced chemical vapor deposition (PECVD) to deposit nano-crystalline graphite (NCG) and apply NCG in MEM/NEM field [16; 17]. Moreover, researchers have carried out micro-/nanoprocessing on graphite and constructed micro-/nanostructures. [PERSON] et al. [18] deposited SiO\({}_{2}\) films as a hard mask on the graphite surface, followed by lithography and etching processes on the graphite surface. [PERSON] et al. [19] used aluminum film as a hard mask, followed by lithography and etching processes, and combined it with transfer technology to produce a 10-nanometer thick vermicular graphite. [PERSON] et al. [20] used lithography and lift-off processes to fabricate metal microstructures on the graphite surface. [PERSON] et al. [21; 22; 23] fabricated graphite-MEMS with titanium film as a hard mask coating on the graphite, then processed photoresist patterns on the titanium film. To the best of our knowledge, the current process of graphite etching relies on metal or metal oxide as a mask material, almost no research on the direct etching of the graphite surface after lithography is available. Moreover, no relevant research on the stability of graphic imaging during the direct lithography of the graphite surface is available.