CN100525000C

CN100525000C - Static discharge protection circuit and structure for part charging mode

Info

Publication number: CN100525000C
Application number: CNB2006101187171A
Authority: CN
Inventors: 常欣; 金锋
Original assignee: Shanghai Hua Hong NEC Electronics Co Ltd
Current assignee: Shanghai Huahong Grace Semiconductor Manufacturing Corp
Priority date: 2006-11-24
Filing date: 2006-11-24
Publication date: 2009-08-05
Anticipated expiration: 2026-11-24
Also published as: CN101192753A

Abstract

The invention discloses a protection circuit of electrostatic discharge in a charge mode of an apparatus, which comprises a GGNMOS apparatus as a clamper of the electrostatic discharge in the charge mode, which is connected between a circuit gate of input stage and a ground wire pin. The invention also comprises a Schottky diode connected between a source of the GGNMOS and the ground wire pin; a metal electrode of the Schottky diode is connected with the source of the GGNMOS; a semiconductor electrode is connected with the ground wire pin. The invention further discloses a corresponding structure of the circuit. The Schottky diode is connected between the source of the GGNMOS and the ground wire pin in the invention. As the forward breakover voltage of the Schottky diode is about 0.3V, compared with the prior art, the breakover voltage is lower when the electrostatic discharge in the charge mode occurs; therefore, the Schottky diode can enter the status of the breakover and discharge current promptly.

Description

The part charging mode ESD-protection structure

Technical field

The present invention relates to a kind of electrostatic discharge protective circuit and corresponding devices structure thereof of device, particularly a kind of under part charging mode (CDM) Electrostatic Discharge situation protection device avoid circuit and the corresponding devices structure thereof that Electrostatic Discharge destroys.

Background technology

Electrostatic Discharge is a problem that must be noted that in the integrated circuit (IC) design.Along with the application of all kinds of integrated circuit, various design has also appearred in the ESD protection.Under the deep-submicron process technique, more and more serious ESD problem is the part charging mode static discharge phenomenon of (Charge Device Model is called for short CDM).Along with the manufacture of semiconductor development of technology, transistor gate level oxide layer is more and more thinner, in the more normal IC of the occurring in product of the damage phenomenon that makes the part charging mode static discharge be caused, therefore in the integrated circuit electrostatic discharge protection, must add special design in addition again and take precautions against the destruction of part charging mode static discharge integrated circuit.So-called charge mode static discharge, be meant the IC product earlier because of friction or other factors within it portion accumulated static, when this IC product that has static in processing procedure, when its pin touches ground plane, inner static just can flow out from inside via pin, and has caused the phenomenon of discharge.The static discharge time of CDM pattern is very short, about about 1 nanosecond.

In the current techniques; the solution that is proposed for the charge mode electrostatic discharge (ESD) protection is; add nearby that on the next door of input stage circuit grid level a undersized GGNMOS device is as CDM static discharge clamper; be connected the input stage circuit grid and ground wire pin (VSS) between; be used for strangulation too high voltage on the input stage circuit grid level; as shown in Figure 1, dotted line is depicted as the static discharge current IESD flow direction among Fig. 1.A concrete examples of applications of this method as shown in Figure 2, internal circuit is a cmos device.Connect a CDM clamp GGNMOS nearby in that the grid of input stage circuit is other, be connected with input stage CMOS grid as the drain electrode of the GGNMOS device of CDM static discharge clamper, the grid of GGNMOS and source electrode be connected to wire pin.Common esd protection circuit comprises that a first class of protection circuit is called esd clamp position (ESD Clamp) and a second class protection device GGNMOS Mn1 by name among Fig. 2.

The operation principle of above-mentioned protective circuit is that when static discharge took place, the electrostatic charge of releasing can cause the parasitic triode conducting of GGNMOS, as shown in Figure 5, produced the phenomenon of negative resistance or flyback (Snapback).As one with respect to ground wire pin VSS end for positive electrostatic interaction during at the GGNMOS drain terminal, the PN junction of drain terminal (collector electrode) and substrate (base stage) is anti-inclined to one side, thereby, voltage causes avalanche breakdown when continuing rising generation ionization by collision, bump knocked on electron and swept the GGNMOS drain terminal by electric field, the hole then flows to substrate and produces substrate current Isub.Because the existence of resistance substrate is drawn high substrate electric potential, thereby substrate (base stage) and source end (emitter) positively biased so the parasitic triode conducting, reach the effect of electrostatic discharge (ESD) protection.In said structure; GGNMOS is under ESD stress, and when having only the abundant forward conduction of PN junction when its substrate (base stage) and source electrode (emitter), ESD electric current immediately could begin to release; be that bias voltage on the substrate must just can enter conducting state and reach the esd protection effect than the high 0.7V of source electrode.

Protect internal circuit although adopted above-mentioned technology; the damage that the charge mode static discharge is caused still can occur on the grid level of input stage circuit sometimes, and this mainly is because electrostatic storage deflection (ESD) protection circuit has little time conducting with the discharging CDM static discharge current of moment.

Summary of the invention

The technical problem to be solved in the present invention provides a kind of part charging mode ESD-protection structure, wherein can quick conducting when the charge mode static discharge takes place as the GGNMOS of charge mode static discharge clamper.

For solving the problems of the technologies described above; part charging mode ESD-protection structure of the present invention; comprise GGNMOS device as charge mode static discharge clamper; this GGNMOS device comprises P type substrate; polysilicon gate and the source end and the drain terminal that form by the ion injection is characterized in that, embed a Schottky diode at GGNMOS device source end; the metal of this Schottky diode is metal silicide very, and semiconductor is P type silicon substrate very.

On described Schottky diode contact both sides N type guard ring is set.

The present invention embeds a Schottky diode at the source end as the GGNMOS of charge mode static discharge clamper; and N type guard ring is set on this Schottky diode contact both sides; because of the forward conduction voltage of Schottky diode is roughly about 0.3V; compared with prior art; when the charge mode static discharge takes place; its conducting voltage is low, can enter conducting state and leakage current faster.

Description of drawings

Fig. 1 is a charge mode electrostatic discharge (ESD) protection schematic diagram in the prior art;

Fig. 2 is the circuit diagram that principle shown in Figure 1 is applied to a physical circuit;

Fig. 3 is principle of the invention figure;

Fig. 4 is the circuit diagram that the present invention is used to protect the embodiment of a cmos device;

Fig. 5 is and the corresponding structural representation of circuit shown in Figure 2;

Fig. 6 is and the corresponding structural representation of circuit shown in Figure 4;

Fig. 7 is and the corresponding domain schematic diagram of Fig. 4.

Embodiment

The present invention is further detailed explanation below in conjunction with accompanying drawing.

Common GGNMOS is under ESD stress; when having only the abundant forward conduction of PN junction when its substrate (base stage) and source electrode (emitter); the ESD electric current that could begin immediately to release, promptly the bias voltage on the substrate must just can enter conducting state and reach the esd protection effect than the high 0.7V of source electrode.

Based on above principle; the invention provides a kind of novel GGNMOS structure; Fig. 6 is specific embodiment of this structure; compare as the structure of CDM static discharge clamper with utilizing GGNMOS in the prior art; pass through to change GGNMOS source end injection zone among this embodiment; embedded a Schottky diode that utilizes metal silicide to contact and form at GGNMOS source end, and formed N type guard ring on the Schottky contacts both sides and slow down electric field and prevent electric leakage with silicon.At this moment as one with respect to VSS end for positive electrostatic interaction during at drain terminal, because the PN junction of drain terminal and substrate is anti-inclined to one side, thereby the voltage rising produces ionization by collision and causes avalanche breakdown when ESD stress, bump knocked on electron and swept drain terminal by electric field, the hole then flows to substrate and produces substrate current Isub.Because the existence of resistance substrate is drawn high substrate electric potential, makes the embedded Schottky diode forward conduction of substrate and source end, reach the purpose that discharges the ESD electric current, the two empty arrow line among Fig. 6 shows the ESD sense of current.Because the forward conduction voltage of Schottky diode is roughly about 0.3V, compare the approximately low 0.4V of traditional substrate and source end PN junction forward conduction voltage, so under identical situation, new structure provided by the present invention can enter conducting state and leakage current faster than GGNMOS of the prior art.With regard to the carrier moving form, during the PN junction forward conduction, by the minority carrier hole in injection N district, P district, their form certain accumulation earlier, form electric current by diffusion motion then simultaneously.The accumulation of the non equilibrium carrier of this injection is called the charge storage effect, and it can influence the high speed performance of PN junction.And Schottky diode is a majority carrier device, mainly is to enter metal by the majority carrier in the semiconductor to form electric current, so have better high speed performance than PN junction.Therefore the Schottky diode of substrate and source end has performance at a high speed than the PN junction that traditional substrate and source end form.For CDM electro-static discharging device protection structure; sometimes have little time conducting with the discharging CDM static discharge current of moment; because this new structure has low conducting voltage and performance at a high speed, the GGNMOS that so just can utilize new structure to replace input stage circuit grid level next door in the prior art comes CDM static emergence pattern is protected.The equivalent electric circuit of the foregoing description as shown in Figure 4, the GGNMOS drain terminal is connected on the grid level of input stage circuit, GGNMOS grid end and source end ground connection, and Schottky diode is as the discharge path of a low positive pressure conducting, its metal utmost point is connected with the GGNMOS source electrode, and the semiconductor utmost point is connected with the ground wire pin; Serve as CDM static discharge clamper together at this GGNMOS and Schottky diode.

Arrange as shown in Figure 7 with the corresponding domain of structure shown in Figure 6, in order to form the Schottky diode that metal silicide contacts with silicon at the source end, only need in traditional GGNMOS domain, to revise the N+ type injection zone in the end active area of source, between metal silicide layer and P type substrate, reserve a directly part of contact, as the N+ zone being made into an annular, N+ encircles the contact channels of hollow space as metal silicide layer and P type substrate, thereby forms a Schottky diode at this.

Structure provided by the present invention is not additionally increasing under the prerequisite of mask and technical process; end has embedded Schottky diode in the source of GGNMOS; and having utilized the characteristic of its low conducting voltage and high speed performance, framework goes out a kind of novel GGNMOS electrostatic preventing structure with high speed on state characteristic.Just because of its quick conduction, this structure can to ESD take place speed faster part charging mode effectively protect.

Claims

1, a kind of part charging mode ESD-protection structure; comprise GGNMOS device as charge mode static discharge clamper; this GGNMOS device comprises P type substrate; polysilicon gate and the source end and the drain terminal that form by the ion injection; it is characterized in that; be provided with a Schottky diode at GGNMOS device source end, the metal of this Schottky diode is metal silicide very, and semiconductor is P type silicon substrate very.

2, part charging mode ESD-protection structure according to claim 1 is characterized in that, on described Schottky diode contact both sides N type guard ring is set.