1 Fabrication flow + Steps

1) Choose a SOI water with 400um silicon layer,4um buried oxide layer and 50 um handle layer as our basic substrate.
2) Grow 200 nm of silicon nitride by LPCVD (low pressure chemical vapor deposition) furnace
3) Grow 200nm of amorphous silicon by PVCVD followed by a quick HF dip in order to remove the native oxide layer. Diffusion dope on the amorphous silicon in MRL furnace by as phosphoryl chloride gas at 900 °C for 20 minutes and then annealed at 1050°C for 30minsutned to drive in the dopant. The amorphous silicon converts to polycrystalline silicon. The phosphosilicate glass layer, which is formed during diffusion process, is finally removed by a buffered oxide etch. 4 point probe measure  sheet resistance is used and value is around 0.75x102 Ω/□
4) Patten the piezoresistive strain gauge using photolithography by Karl Suss MA6 Mask Aligner followed by a RIE to transfer geometry into the polysilicon layer
5) Define and etch windows on the topside silicon nitride layer by Oxford 80 RIE etcher to make electrical connections to
the device layers
6) Define a lift-off pattern of the electrical trace and bond pads. CHA E-beam evaporation is used to deposit a 30nm
titanium adhesion layer followed by a 200nm gold trace layer. Then a lift-off process involved to remove the excess gold from wafer.
7) Spin a protection photoresist top of thew wafer and etch the backside polysilicon and silicon nitride layer.
8) Deposit 200nm of Al2O3 on both side the wafer as hard mask for deep silicon etch.
9) Define and transfer pattern on the bottom side Al2O3 by Cambridge Nano Tech savannh TM 200 ALD
10) Define and transfer pattern on the top side Al2O3.
11) Etch and transfer pattern into topside device layer by DRIE to define the thermal actuator by Asher Nordson March PX-250 deep silicon etch
12) Etch and transfer pattern into bottom side device layer by DRIE to define the thermal actuator and followed by a silicon oxide box layer etch to release the device.
13) Etch the top side Al2O3 hard mask to remove protective mask layer by RIE 790 plasma therm and re-expose the gold trace and bond pads.