Diamond and diamond-like carbon MEMS

Abstract

Diamond and diamond-like carbon (DLC) thin films possess a number of unique and attractive material properties that are unattainable from Si and other materials. These include high values of Young's modulus, hardness, tensile strength and high thermal conductivity, low thermal expansion coefficient combined with low coefficients of friction and good wear resistance. As a consequence, they are finding increasing applications in micro-electro-mechanical systems (MEMS). This paper reviews these distinctive material properties from an engineering design point of view and highlights the applications of diamond and DLC materials in various MEMS devices. Applications of diamond and DLC films in MEMS are in two categories: surface coatings and structural materials. Thin diamond and DLC layers have been used as coatings mainly to improve the wear and friction of micro-components and to reduce stiction between microstructures and their substrates. The high values of the elastic modulus of diamond and DLC have been exploited in the design of high frequency resonators and comb-drives for communication and sensing applications. Chemically modified surfaces and structures of diamond and DLC films have both been utilized as sensor materials for sensing traces of gases, to detect bio-molecules for biological research and disease diagnosis.

Principles for designing sputtering-based strategies for high-rate synthesis of dense and hard hydrogenated amorphous carbon thin films

“…For example, Godet et al [36] showed that polymeric a-C:H films exhibiting low mass densities (< 2 g/cm 3 ) and high H content (25%-40%) are grown under low RF bias powers using C2H2 as well as CH4 based ECR discharges while Baby et al [37] found a high average Raman base line slope at lower substrate bias potentials which corresponds to a high H content in the films when they deposited a-C:H films using C2H2/Ar based ICP discharge. In our case similar trends with respect to mass density are observed for films (see Fig.2) grown using HiPIMS+DCMS at Eion = -eVfl, whereas in 100% Ar HiPIMS case (where there is no intentional use of H) the film exhibit higher density at this ion energy values.…”

“…As a result of implantation, an increase in the local density of C atoms in the subsurface region occurs which causes a bond rearrangement from weaker C-C sp 2 to stronger C-C sp 3 bonds giving rise to denser phase of a-C as compared to the growth with lower Eion than Ep [5,38]. A further increase in Eion is likely to enhance implantation which in turn would result in an increased mass density of the film.…”

“…The physical attributes and thus the performance of amorphous carbon (a-C) thin films in technological applications are largely determined by their bonding configuration (i.e., sp 3 -tosp 2 bond ratio), as well as on the amount of hydrogen in the films [1][2][3][4][5][6][7]. Bonding configuration and hydrogen content can be, in turn, tailored by controlling the energy and flux of the depositing species [5,6].…”

“…Using magnetron sputtering based high plasma density discharges such as high power impulse magnetron sputtering (HiPIMS) [15] a higher C ionized fraction, mass density as well as sp 3 /sp 2 fraction has been obtained. However these properties are not comparable to those obtained by CVA and PLD [16,17].…”

Diamond, Diamond-Like Carbon (DLC) and Diamond-Like Nanocomposite (DLN) Thin Films for MEMS Applications

“…The DC plasma jet chemical vapor deposition can be used for Diamond like carbon films deposition also [28]. Table 1 shows the different properties of diamond films [29][30][31]6]. In this section, we describe diamond-like carbon deposition by plasma which consists of argon (99.998%), hydrogen (99.9%) and CH 4 (99.5%) is used as a carbon source and is mixed into the plasma jet.…”