Abstract. Single crystal 3C-SiC films were grown on (100) and (111) Si substrate orientations in order to study the resulting mechanical properties of this material. In addition, poly-crystalline 3C-SiC was also grown on (100)Si so that a comparison with monocrystaline 3C-SiC, also grown on (100)Si, could be made. The mechanical properties of single crystal and polycrystalline 3C-SiC films grown on Si substrates were measured by means of nanoindentation using a Berkovich diamond tip. These results indicate that polycrystalline SiC thin films are attractive for MEMS applications when compared with the single crystal 3C-SiC, which is promising since growing single crystal 3C-SiC films is more challenging. MEMS cantilevers and membranes fabricated from a 2 µm thick single crystal 3C-SiC grown on (100)Si under similar conditions resulted in a small degree of bow with only 9 µm of deflection for a cantilever of 700 µm length with an estimated tensile film stress of 300 MPa. Single crystal 3C-SiC films on (111)Si substrates have the highest elastic and plastic properties, although due to high residual stress they tend to crack and delaminate.

There is a technological need for hard thin films with high elastic modulus and fracture toughness. Silicon carbide (SiC) fulfills such requirements for a variety of applications at high temperatures and for high-wear MEMS. A detailed study of the mechanical properties of single crystal and polycrystalline 3C-SiC films grown on Si substrates was performed by means of nanoindentation using a Berkovich diamond tip. The thickness of both the single and polycrystalline SiC films was around 1-2 µm. Under indentation loads below 500 µN both films exhibit Hertzian elastic contact without plastic deformation. The polycrystalline SiC films have an elastic modulus of 457 + 50 GPa and hardness of 33.5 + 3.3 GPa, while the single crystalline SiC films elastic modulus and hardness were measured to be 433 + 50 GPa and 31.2 + 3.7 GPa, respectively. These results indicate that polycrystalline SiC thin films are more attractive for MEMS applications when compared with the single crystal 3C-SiC, which is promising since growing single crystal 3C-SiC films is more challenging.

Having superior mechanical properties, 3C-SiC is one of the target materials for power MEMS applications. Growing 3C-SiC films on Si is challenging, as there is a large mismatch in lattice parameter and thermal expansion between the SiC film and the Si substrate that needs to be accommodated, and results in high residual stress. Residual stress control is critical in MEMS devices as upon feature release it results in substantial deformation.3C-SiC single crystalline films were deposited on 50 mm (100) and (111) Si substrates in a hot-wall CVD reactor. The film tensile residual stress was so high that it fractured on the (111) Si wafer. The resulting film thickness on the (100) Si wafer was non-uniform, having a linear profile along the growth direction. This presented a challenge of using the substrate curvature method for calculating residual stress. Finite Element Method correction was applied to the Stoney's formula for calculating the residual stress along the wafer radius. Suggestions for reducing the amount of residual stress are made.