Browse Prior Art Database

Deep Trench Guard Ring

IP.com Disclosure Number: IPCOM000102860D
Original Publication Date: 1990-Mar-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 1 page(s) / 47K

Publishing Venue

IBM

Related People

Bracchita, JA: AUTHOR [+2]

Abstract

By means of a diode gated by a deep trench, carriers are trapped in a depletion region along side the trench walls and collected, thus avoiding carrier drift to adjacent devices where they may cause voltage shift below ground or above supply voltage (voltage over- and under-shoots).

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Deep Trench Guard Ring

      By means of a diode gated by a deep trench, carriers are
trapped in a depletion region along side the trench walls and
collected, thus avoiding carrier drift to adjacent devices where they
may cause voltage shift below ground or above supply voltage (voltage
over- and under-shoots).

      A typical guard ring is a diffusion of the proper type which
completely surrounds a forward biased diffusion; e.g., Ndiffusions
are used to guard against forward biased N+ diffusions.  Referring to
the figure, effectiveness of electron collection by N+ guard ring
diffusion 2 is enhanced by adding a doped polysilicon filled deep
trench 4.  Trench 4 penetrates Ndiffusion 2, P- epitaxial silicon 6,
and several microns into P+ substrate 8.  Walls of trench 4 have an
insulating layer 10.  A silicide strap 12 connects both parts of
diffused ring 2, and polysilicon in trench 2 to metal line 14 which
further interconnects P+ diffusion 16 over oxide 18.  These
interconnected parts 2, 4, 12, 14, and 16 are held at supply voltage
VDD.  A depletion region 20 is thus formed which collects electrons
emitted by forward biased N+ diffusion 22 that might otherwise
diffuse under oxide 24 to neighboring devices.  Electrons diffusing
to the depth of the trench have high probability of neutralization in
the heavily doped substrate 8 and have little chance of escaping to a
neighboring device region.

      Disclosed anonymously.