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Draw and explain working principle of cantilever. Show basic quantitative behavior of cantilever. Also discuss process steps for fabrication of cantilever.

Mumbai University > Electronics Engineering > Sem 8 > MEMS Technology

Marks: 10M

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Surface micro-machined devices are typically made up of 3 types of components.

  1. A sacrificial component [spacer layer]
  2. A micro structural component
  3. An insulator component

The sacrificial components are usually made of phosphosilicate glass [PSG] ori $Sio_2$ deposited on substrates by LPCVD techniques

PSG can be etched more rapidly than $Sio_2$ in HF etchants. These components in the form of films can be as long as 1 to 2000 $\mu m$ and 0.1 to 5 $\mu m$ thick.

Both micro-structural and insulator components can be deposited in thin films. Polysilicon is a popular material

The etching rates for sacrificial components must be much higher than those for the two other components.

1. - A silicon substrate base with a PSG deposited on its surface.

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2. - A mask [ mask 1 ] is made instep 2 to cover the surface of the PSG layer for the subsequent etching to allow for the attachment of the future cantilever beam as shown in step 3.

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4. - Another mask [ mask 2 ] is made for the deposition of poly-silicon micro structural material in step 4.

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The PSG that remains in step 5 is subsequently etched way to produce the desired cantilever beam as shown in step 6.

enter image description here

The most suitable etchant used in the last step for the sacrificial PSG layer is 1 : 1 HF, Which is made of 1 : 1 HF : $H_2O$ + 1 : 1 HCI : $H_2O$

After itching, the structure is rinsed in deionized water thoroughly followed by drying under infrared lamp.

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