Biomedical Engineering Reference
In-Depth Information
Poly0 Etch
Poly0 Etch
P1_P2_via Etch
P1_P2_via Etch
Poly1
Poly1
2nd oxide
1st oxide
Poly0
Nitride
Poly0
Nitride
Substrate
Substrate
1st oxide
Anchor2 Etch
Poly0
P1_P2_via Etch
P1_P2_via Etch
Nitride
2nd oxide
2nd oxide
Poly1
Poly1
1st oxide
1st oxide
Poly0
Nitride
Substrate
Dimple Etch
Dimple Etch
Anchor1 Etch
Anchor1 Etch
1st oxide
Substrate
Poly0
Nitride
Poly2
2nd oxide
2nd oxide
Poly1
Poly1
1st oxide
1st oxide
Substrate
Poly0
Nitride
PSG Hard mask
Poly1
Substrate
1st oxide
Metal
Metal
Poly0
Nitride
Poly2
2nd oxide
2nd oxide
Poly1
Poly1
Substrate
1st oxide
1st oxide
Poly0
Nitride
Poly1
Poly1
1st oxide
Poly0
Nitride
Substrate
Poly2
Substrate
Poly1
Poly1
Poly0
Nitride
Poly1
Poly1
2nd oxide
1st oxide
Poly0
Nitride
Substrate
Substrate
1st oxide
Nitride
Poly0
Poly1
Poly2
Substrate
2nd oxide
Metal
FIGuRE 8.21
Cross. sections. of. the. three-layer. “PolyMUMPS”. polysilicon. surface. micromachining. process.
ofered. by. MEMSCAP.. Polysilicon. and. oxide. layers. are. deposited. and. patterned. in. a. cyclic. process,. with. anneal.
steps.of.the.doped.sacriicial.oxide.between.polysilicon.depositions..POLY0.is.an.electrical.layer.that.is.not.released..
POLY1.and.POLY2.are.structural.layers.that.can.be.released..he.deposition.and.patterning.steps.shown.here.result.
in.a.polysilicon.wheel,.deined.in.POLY1,.that.is.constrained.by.a.hub,.deined.in.POLY2..Dimples.deined.in.POLY1.
keep.the.wheel.from.becoming.stuck.to.the.POLY0.layer..(Reprinted.with.permission.from.MEMSCAP.Inc.)
with. one. of. the. plates. released. so. that. it. is. able. to. move,. as. shown. in.
Figure. 8.23
.. he. relationship.
between.the.capacitance.
C
,.voltage.
V
,.and.charge.
Q
.for.a.capacitor.is.given.by
Q
V
.
C
=
.
(8.6.2.1)
