Input protection circuit for use in semiconductor device having an improved electrostatic breakdown voltage
First Claim
1. An input protection circuit for use in a semiconductor device, comprising:
- an input signal pad selectively coated on an interlayer insulator film formed above a semiconductor substrate of a first conductivity type;
a bipolar protection device constituted of;
a first diffused layer of a second conductivity type opposite to said first conductivity type, said first diffused layer being connected to said input signal pad and formed selectively at a surface portion of said semiconductor substrate;
a second diffused layer of said second conductivity type formed at said surface portion of said semiconductor substrate, to extend in parallel to said first diffused layer but separated from said first diffused layer by a first space;
a third diffused layer of said first conductivity type formed in said semiconductor substrate in said first space to extend in parallel to said first and second diffused layers, in junction with said second diffused layer but separately from said first diffused layer, said third diffused layer having an impurity concentration higher than that of said surface portion of said semiconductor substrate,wherein said third diffused layer extends to cover a bottom and a side of said second diffused layer; and
a power supply line connected to said second diffused layer; and
an input protection resistor having a first terminal connected to said input signal pad and a second terminal connected to an input signal internal wiring conductor.
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Accused Products
Abstract
In an input protection circuit, a bipolar protection device is constituted of a semiconductor substrate of a first conductivity type, a first diffused layer of a second conductivity type formed in the substrate and connected to an input signal pad, a second diffused layer of the second conductivity type formed in the substrate to extend in parallel to the first diffused layer but separately from the first diffused layer by a first space, and a third diffused layer of a high impurity concentration and of the first conductivity type formed in the first space in the substrate to extend in parallel to the first and second diffused layers, in junction with the second diffused layer but separately from the first diffused layer. When a backward biasing voltage is applied, the thickness of a depletion layer formed is made large, so that generation of hot carriers is minimized. Thus, increase of a leakage current caused because hot carriers generated by application of an overvoltage were injected into a field oxide film, can be prevented.
12 Citations
8 Claims
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1. An input protection circuit for use in a semiconductor device, comprising:
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an input signal pad selectively coated on an interlayer insulator film formed above a semiconductor substrate of a first conductivity type; a bipolar protection device constituted of; a first diffused layer of a second conductivity type opposite to said first conductivity type, said first diffused layer being connected to said input signal pad and formed selectively at a surface portion of said semiconductor substrate; a second diffused layer of said second conductivity type formed at said surface portion of said semiconductor substrate, to extend in parallel to said first diffused layer but separated from said first diffused layer by a first space; a third diffused layer of said first conductivity type formed in said semiconductor substrate in said first space to extend in parallel to said first and second diffused layers, in junction with said second diffused layer but separately from said first diffused layer, said third diffused layer having an impurity concentration higher than that of said surface portion of said semiconductor substrate, wherein said third diffused layer extends to cover a bottom and a side of said second diffused layer; and a power supply line connected to said second diffused layer; and an input protection resistor having a first terminal connected to said input signal pad and a second terminal connected to an input signal internal wiring conductor. - View Dependent Claims (2, 3, 4, 5)
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6. An input protection circuit for use in a semiconductor device, comprising:
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an input signal pad selectively coated on an interlayer insulator film formed above a semiconductor substrate of a first conductivity type; a bipolar protection device constituted of; a first diffused layer of a second conductivity type opposite to said first conductivity type, said first diffused layer being connected to said input signal pad and formed selectively at a surface portion of said semiconductor substrate; a second diffused layer of said second conductivity type formed at said surface portion of said semiconductor substrate, to extend in parallel to said first diffused layer but separated from said first diffused layer by a first space; a third diffused layer of said first conductivity type formed in said semiconductor substrate in said first space to extend in parallel to said first and second diffused layers, in junction with said second diffused layer but separated from said first diffused layer, said third diffused layer having an impurity concentration higher than that of said surface portion of said semiconductor substrate, wherein said third diffused layer of each of said first named bipolar protection device and said second bipolar protection device extends to cover a bottom and a side of said second diffused layer; and a power supply line connected to said second diffused layer; and an input protection resistor having a first terminal connected to said input signal pad and a second terminal connected to an input signal internal wiring conductor, wherein said bipolar protection device is connected between said input signal pad and a power supply line, and a second bipolar protection device having the same structure as that of said bipolar protection device, is connected between said input signal pad and a ground line. - View Dependent Claims (7, 8)
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Specification