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1996-10-09
Paul McGrath
1996-10-21
[email protected]
1996-10-22
Raj Gupta
1996-12-12
Shekhar Bhansali
1996-03-06
Christopher Raum
1997-05-02
[email protected]
1997-05-06
Babak Taheri
1997-07-04
Dr.Revati N.Kulkarni
1997-01-22
chao sun apph stnt
1997-07-25
[email protected]
No subject
Raj Gupta
1996-10-22
Message-Id:   <[email protected]>


Hi Guenter,

I find that surface deposition of charges also occur on SiN, where
SiN is the dielectric sitting on top of the Si substrate.  Charges
can be deposited either after pull-in (as in your case) or while the
structure is electrostatically deflected towards the substrate w/o
touching it at a voltage below pull-in.  To see the latter effect
in the devices I test (MUMPs polysilicon process of MCNC), I need
to wait on the order of a few minutes.  This procedure deposits
charges of the opposite polarity on the SiN and will decrease the
subsequently measured pull-in voltage.

I have not calculated the surface charge density, but I see pull-in
voltage shifts of up to, for example, 1V on a sample with a pull-in
voltage near 25V, with a nominal electrostatic gap of 2.2um.

Seeing such charge deposition is not uncommon in dielectrics, and
are a result of dangling bonds on the surface.

Raj Gupta
MIT


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