Fabrication of MEMS Components Based on Ultrananocrystalline Diamond Thin Films and Characterization of Mechanical Properties

Abstract

The mechanical, thermal, chemical, and tribological properties of diamond make it an ideal material for the fabrication of MEMS components. However, conventional CVD diamond deposition methods result in either a coarse-grained pure diamond structure that prevents high- resolution patterning, or in a fine-grained diamond film with a significant amount of intergranular non-diamond carbon. At Argonne National Laboratory, we are able to produce phase-pure ultrananocrystalline diamond (UNCD) films for the fabrication of MEMS components. UNCD is grown by microwave plasma CVD using C60-Ar or CH4-Ar plasmas, resulting in films that have 3-5 nm grain size, are 10-20 times smoother than conventionally grown diamond films, and can have mechanical properties similar to that of single crystal diamond. We used lithographic patterning, lift-off, and etching, in conjunction with the capability for growing UNCD on SiO2 to fabricate 2-D and 3-D UNCD-MEMS structures. We have performed initial characterization of mechanical properties by using nanoindentation and in-situ TEM indentor techniques. The values of Hardness (∼88 GPa) and Young's modulus (∼ 864 GPa) measured are very close to those of single crystal diamond (100 GPa and 1000 GPa respectively). The results show that UNCD is a promising material for future high performance MEMS devices.

Are Diamonds a MEMS' Best Friend?

“…UNCD films exhibit hardness (98 GPa) and Young's modulus (980 GPa) [20] similar to corresponding values for singlecrystal diamond (100 GPa and 1,000 GPa, respectively). The Young's modulus is reduced to about 880 GPa [4] when adding about 3% N 2 in the gas phase to the plasma chemistry in order to produce electrically conductive UNCD films.…”

Strength of ultrananocrystalline diamond controlled by friction of buried interfaces

“…Materials with grain size refined to the nanometre scale hold great potential for mechanical applications that range from microelectromechanical systems (MEMS) to macroscopic abrasive coatings and cutting tools used in industrial applications [1][2][3][4][5][6][7][8][9]. Superior mechanical properties of nanocrystalline (NC) materials include high hardness, outstanding wear resistance, and improved fracture toughness and ductility [1,4,5,7].…”

“…We chose this material for a few different reasons. First of all, UNCD is a promising material for tribological applications because of its superior mechanical properties [2,6,9,[33][34][35][36][37][38][39][40][41][42]. For example, hardness of UNCD can be as high as 98 GPa [38].…”

“…Although it is expected that deformation of UNCD is localized at GBs, so far specific mechanisms of plasticity in this material have not been identified. UNCD serves also as an excellent model material to quantify the effect of GBs on a mechanical response because the extremely high value of τ dis in diamond (∼90 GPa, see section 3) makes the nucleation of dislocations unlikely during mechanical deformation [2,[33][34][35]38]. Understanding gained in the studies of UNCD will provide insights into deformation mechanisms of other NC materials (and NC ceramics in particular) in the regime where dislocation activity is known to be suppressed [18,19].…”

Synthesis of ultrananocrystalline diamond films by microwave plasma assisted chemical vapor deposition system

“…The Young's moduli measured were 840-930 GPa. For comparison, values reported for previous UNCD results include an average of 886 GPa measured using nanoindentation, (15) a range of 916-959 GPa measured using microcantilever deflection, (16) and a range of 930-970 GPa measured using microscale membrane deflection. (16) One important consideration for the deposition of UNCD for applications is the uniformity of the deposition across the 7.5-cm-diameter substrates that were used in this study.…”