The chemical resistance of nano-sized SiC rich composite coating

• An 8–30 nm thick layer containing C, Si, Ga and SiC was produced by ion mixing of C/Si interface.
• SiC was in amorphous nano particle form.
• The intermixed layer containing > 20% SiC withstands harsh chemical etching.
• The layer fails by a defect mediated process.
• The etching rate of the non-defective part of the layer orders of magnitude less than that of poly-Si

30 keV Ga+ implantation was applied to a nominally C(20 nm)/Si(20 nm)/C(20 nm)/Si(20 nm)/C(20 nm)/Si substrate multilayer system. Due to the irradiation intermixing occurred and a layer containing C, Si, Ga and (amorphous) SiC was obtained. The thickness (7–30 nm) and composition of the layer depended on the fluence of irradiation. The chemical resistance of the layer was tested by applying microwave oxidation and various polysilicon etchants and was found to be excellent if the SiC concentration was above 20%. Using an etchant with an etching rate of about 100 nm/s for poly-Si during 10 s had not affected the integrity of the intermixed region with a thickness of 10 nm; only some defects appeared. With a further increase of the etching time the size of defects increased resulting in inhomogeneous layer removal. The in-depth composition of non-defective region that remained on the surface was determined by AES depth profiling, which revealed that the intermixed layer did not change during the harsh etching except the removal of its thin surface layer containing less than 20% SiC. The etching rate of the intermixed layer is orders of magnitude lower than that for poly-Si.