Poly -substrate etching exposure

A silicon wafer that has one surface oxidized to a controlled depth is coated (on the oxide surface) with a photoresist, such as poly(vinyl cinnamate), to produce a thin and uniform coating several micrometers thick when dry. Exposure to UV light through a mask insolubilizes part of the polymer. The uncross-linked polymer is washed off solvents. The bare substrate parts that thus reappear are etched through the oxide layer down to the silicon layer by a fluoride solution in water or by a plasma that contains reactive ions. 

Fig. 2 Process flow (a) Starting Material, (b)Deposit SisN (c)Deposit poly-silicon, (d) Deposit Al, (e) Resist coating, (f) Soft bake, (g) Exposure mask, (h) Develop resist (i) Poly-silicon RIE, (j) Alum etch and stripe resist, ion(k) Dry oxidation, (1) Poly-silicon nanogap pattern with pad Pt/Au fabrication( Electrical checking of the device can be performed on the fabricated pad)(Repeat step (a) to (j) for mask 2). Fig. 3 shows the circuit after serial impedance is measured, a simple resistor model is developed representing the substrate and polysilicon layer. The capacitor also found in series to describe the device with no liquid test...

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