Nitride cantilevers with single crystal silicon tips

摘要

A nitride cantilever is formed with an integral conical silicon tip at the free end thereof. A top layer of silicon dioxide is patterned into a tip mask on a doped or epitaxial silicon layer in a silicon substrate. Photoresist is spun on the silicon substrate and patterned and the silicon is etched to define a cantilever pattern in the substrate with the tip mask positioned to be near the free end of a nitride cantilever to be subsequently formed. A bottom layer of silicon dioxide is formed on the silicon substrate and then patterned and etched to define a masking aperture on the bottom silicon dioxide layer. The bottom of the silicon substrate is anisotropically etched through the masking aperture and the etch stops at the doped silicon layer. Alternatively, electrochemical etching is done by applying an electric potential across the P-N junction between the doped silicon layer and the appropriately-doped substrate. This releases the free end of the doped silicon layer from the silicon substrate. The anisotropic etch preferentially etches all of the crystal planes of the silicon substrate except the (111) planes to leave a silicon base from which extends the silicon surface layer as a cantilever. A nitride layer is then formed on the silicon substrate and dry etched from the top surface of the doped silicon surface layer to form a nitride cantilever on the bottom of the silicon substrate. The doped silicon layer is etched away while the tip mask helps to form a pointed silicon tip near the free end of the nitride cantilever. A microfabricated cantilever includes a (100) silicon base having a (111) oblique side. A nitride layer is formed over the (111) oblique side of the silicon base and extends outwardly from the top surface of the silicon base to form a nitride cantilever having one end fixed to the silicon base and having a free end. On the free end is fixed a single-crystal sharp conical silicon tip which extends upwardly.