Spark gap for high voltage integrated circuit electrostatic...

Details Spark gap for high voltage integrated circuit electrostatic... Spark gap for high voltage integrated circuit electrostatic...

1999-02-09

2001-04-10

Wong, Don (Department: 2821)

Electric lamp and discharge devices: systems

Periodic switch in the supply circuit

Silicon controlled rectifier ignition

Reexamination Certificate

active

06215251

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a spark gap for high voltage integrated circuit electrostatic discharge protection circuit and more particularly, the present invention relates to a spark gap in a plastic assembly capable of withstanding high voltage and dissipating same.
BACKGROUND OF THE INVENTION
Over the years, since the invention of integrated circuits, an increasing number of high voltage circuit functions have been integrated into the silicon integrated circuit. Prior to this the high voltage circuit functions were implemented with discrete components or designed into hybrid modules. These two technologies are expensive for a given circuit compared to an integrated circuit.
The present invention provides an alternative to existing arrangements capable of isolating delicate components in the circuit from static discharge damage which may be of the order of kilovolts.
An important feature for implementing high voltage functionality on a semiconductor integrated circuit is to isolate the core circuitry behind high value resistors, usually of poly silicon resistors. Unfortunately, a problem arises when the chip is subjected to electrostatic discharges, ESD, because the resistance offered by the resistors is much higher than the output resistance of the ESD discharge. This causes a significant voltage to appear on the integrated circuit. Since ESD voltages are typically a few kilovolts, damage to the field oxide of the circuit may result. A particularly difficult problem arises when an input pad has to support both positive and negative high voltages in normal operation. Under these conditions, it is unlikely that a suitable on-chip diode pair can hold off the operating voltages and protect the semiconductor chip from ESD damage.
In principle, a simple spark gap may be used to provide protection for either polarity pulse and also to hold off the circuit voltages. A spark gap can be made to operate at less than 1000V on an integrated circuit, which may be adequate to protect the field oxide.
However, a further complication arises from the commercial need to use inexpensive plastic encapsulation for the silicon chip.
The present invention thus provides a spark gap operable in a plastic package, and a protection device for operation at about 2 kV ESD voltage (human body model, HBM).
SUMMARY OF THE INVENTION
One object of the present invention is to provide an improved spark gap assembly which overcomes the limitations of the prior art.
A further object of one embodiment of the present invention is to provide a spark gap assembly, comprising:
a first electroconductive bonding pad having an electrode;
a second electroconductive bonding pad having an electrode, each electrode of each pad in spaced relation to the other electrode;
at least a further electroconductive material overlying and isolating the first bonding pad and electrode and the second bonding pad and electrode; and
a spark gap in the further material between isolated pads and electrodes.
Yet another object of one embodiment of the present invention is to provide a spark gap assembly, comprising:
an electroconductive bonding pad having an electrode, the pad including a layer of first electroconductive material thereover;
a layer of second electroconductive material in electrical communication with the electrode;
at least one spark gap in the layer of second material; and
a plurality of individual resistor sections integral with the second material and adjacent the spark gap for reducing voltage in the gap from an electrostatic discharge.
Having thus generally described the invention, reference will now be made to the accompanying drawings illustrating preferred embodiments.


REFERENCES:
patent: 4809044 (1989-02-01), Pryor et al.
patent: 5357397 (1994-10-01), Leary
patent: 5436183 (1995-07-01), Davis et al.
patent: 5440162 (1995-08-01), Worley et al.
patent: 5610790 (1997-03-01), Staab et al.
patent: 5629617 (1997-05-01), Uhling et al.
patent: 5811935 (1998-09-01), Pinker et al.
patent: 5992326 (1999-11-01), Martinez-Tovar et al.
patent: 790758 (1997-08-01), None
patent: 2049299 (1980-12-01), None

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