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Browse Prior Art Database

Chip Encircling Electrostatic Discharge Protection

IP.com Disclosure Number: IPCOM000119548D
Original Publication Date: 1991-Feb-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 2 page(s) / 64K

Publishing Venue

IBM

Related People

Colt, JZ: AUTHOR

Abstract

A bipolar clamp device is constructed to encircle an entire integrated circuit chip. Electrostatic discharge (ESD) high voltage and current is shunted away from sensitive circuitry through the very large, low impedance clamp without damage to the clamp device or the circuit it protects.

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This is the abbreviated version, containing approximately 61% of the total text.

Chip Encircling Electrostatic Discharge Protection

      A bipolar clamp device is constructed to encircle an
entire integrated circuit chip.  Electrostatic discharge (ESD) high
voltage and current is shunted away from sensitive circuitry through
the very large, low impedance clamp without damage to the clamp
device or the circuit it protects.

      Referring to Fig. 1, active circuit 10 is typically protected
by diodes D1, D2, D3, and D4 and a clamp device, e.g., NPN device C1
or PNP device C2, connected between high voltage line VH and low
voltage line VL.  The clamp device handles ESD voltage appearing
across pads P1 and P2.

      To create a clamp device which will not be damaged by ESD
discharges, especially with shallow junction technology, an extremely
large device is made to encircle an entire chip.  A cross-section of
such a device, a bipolar PNP such as device C2 in Fig. 1, is shown
in Fig. 2.  Regions 12 and 14 are P+ diffusions in substrate 16.
Regions 18 and 20 are N diffusions in substrate 16.  Regions 22, 24,
and 26 are P+ diffusions in N-well 18.  Insulating layer 28 has via
holes through which VL metal line 30 contacts diffusion 12 (node W in
Fig. 1) and diffusion 22.  Distance d between diffusion 22 and
diffusion 24, which is connected to metal VH 32 (node X in Fig. 1),
is varied to adjust voltages VA and VB on the NPN device
characteristic curve shown in Fig. 3.  Note that metal 32 contacts
both diffusions 24 and 18, thereby making c...