Patent ID: 7838321

Claim:
A method for forming a deformable micro-mechanical device useful in an inkjet printing device, said method comprising: providing a starting structure comprising an upper deformable polysilicon layer with a release hole there through, said release hole extending from through said upper deformable polysilicon layer to a first sacrificial oxide layer, underlying layers, positioning said first sacrificial oxide layer and a second sacrificial nitride layer, etching said starting structure whereby said first sacrificial oxide layer is removed by a hydrofluoric (HF) initial etch, thereby leaving said second nitride sacrificial layer and said underlying layers intact, subsequently, said second (nitride) sacrificial layer is removed by a phosphoric acid etch to provide a final deformable micro-mechanical device, providing thereby said final deformable micro-mechanical device having an upper deformable polysilicon layer with a release hole therein and an air gap below said upper deformable layer, and below said gap are positioned said underlying layers.