CN100590872C

CN100590872C - Low trigger voltage thyristor electrostatic protection structure

Info

Publication number: CN100590872C
Application number: CN 200710094273
Authority: CN
Inventors: 田光春
Original assignee: Shanghai Hua Hong NEC Electronics Co Ltd
Current assignee: Shanghai Huahong Grace Semiconductor Manufacturing Corp
Priority date: 2007-11-23
Filing date: 2007-11-23
Publication date: 2010-02-17
Anticipated expiration: 2027-11-23
Also published as: CN101442047A

Abstract

The invention discloses a low-trigger voltage thyristor static protective structure, which comprises an NMOS transistor and an SCR structure, wherein the NMOS transistor is formed in PW; an NPN transistor formed by N+/PW/N+ parasitized by the NMOS transistor and an NPN transistor formed by parasitic N+/PW/NW have the same emitter terminal and base terminal; the SCR structure consists of a parasitic PNP transistor formed by N+/PW/NW and a parasitic NPN transistor formed by N+/PW/NW; a drain electrode of the NMOS transistor is in electrical connection with the static terminal through an NW resistor Rnw1; and trigger of the SCR structure is controlled by the NMOS transistor and the NW resistor Rnw1. The low-trigger voltage thyristor static protective structure can effectively reduce trigger voltage during SCR static protection, and can adjust the trigger voltage according to requirement so as to greatly facilitate static protection design, and can adjust current gain of the SCR structureaccording to requirement, thereby improving the static protecting capability of the structure.

Description

Electrostatic protection structure for low trigger voltage thyristor

Technical field

The present invention designs a kind of electrostatic protection device structure, particularly relates to a kind of electrostatic protection structure for low trigger voltage thyristor.

Background technology

As electrostatic protection device, thyristor (SCR) has stronger electrostatic leakage ability than Metal-oxide-semicondutor field effect transistor (MOSFE), and the electrostatic leakage ability of general SCR structure is 5～7 times of MOSFET.Figure 1 shows that the cross-sectional view of high trigger voltage SCR structure.In Fig. 1, the collector electrode of the parasitic PNP pipe that P+/NW/PW forms also is simultaneously the base stage of the parasitic NPN pipe of N+/PW/NW formation; Equally, the collector electrode of the parasitic NPN pipe of N+/PW/NW formation also is the base stage of the parasitic PNP pipe of P+/NW/PW formation.The equivalent circuit diagram circuit structure as shown in Figure 2 that parasitic NPN among Fig. 1 and PNP pipe are formed.As can be seen, the trigger voltage of the common SCR structure of forming of parasitic NPN pipe that parasitic PNP pipe that is formed by P+/NW/PW and N+/PW/NW form is the reverse breakdown voltage that NW/PW ties from Fig. 1 and Fig. 2.Usually the reverse breakdown voltage of NW/PW knot is than higher, and therefore, the application of this structure has been subjected to very big restriction.Structure shown in Figure 3 can reduce the trigger voltage of SCR electrostatic preventing structure effectively.Because the parasitic NPN pipe that is formed by N+/PW/N+ of NMOS pipe has identical emitter and base stage with the NPN pipe that N+/PW/NW forms, when the NPN pipe that is formed by N+/PW/N+ is triggered conducting, the NPN that N+/PW/NW forms is conducting simultaneously also, thereby triggers the common SCR structure of forming of the parasitic NPN pipe that parasitic PNP manages and N+/PW/NW forms that P+/NW/PW forms.Fig. 4 is the equivalent circuit diagram of SCR structure shown in Figure 3.From Fig. 3 and Fig. 4 as can be seen, the trigger voltage of this SCR structure is owing to there is the existence of resistance R nw, usually than the trigger voltage height of simple NMOS pipe parasitic NPN pipe.And resistance R nw is necessary for the operate as normal of SCR, must guarantee that the emitter-base stage of the parasitic PNP pipe that P+/NW/PW forms keeps forward bias by resistance R nw.

Summary of the invention

The technical problem to be solved in the present invention provides a kind of electrostatic protection structure for low trigger voltage thyristor; trigger voltage in the time of can reducing the SCR electrostatic protection effectively; can also carry out as required freely adjusting this trigger voltage, thereby make things convenient for the electrostatic protection design greatly.

For solving the problems of the technologies described above, electrostatic protection structure for low trigger voltage thyristor of the present invention comprises:

One NMOS pipe is formed among the PW (P trap), and the NPN pipe that the parasitic NPN that is formed by N+/PW/N+ of this NMOS pipe manages with N+/PW/NW by parasitism forms has identical emitter terminal and base terminal;

One SCR structure, the parasitic PNP pipe that forms by P+/NW/PW and form by the NPN pipe that the N+/PW/NW of parasitism forms, when the NPN that is formed by N+/PW/N+ managed triggering and conducting, the NPN that is formed by the N+/PW/NW of parasitism managed also conducting; And then trigger described SCR structure; Wherein:

The drain electrode of described NMOS pipe is electrically connected with the static end by NW resistance R nw1, and the triggering of described SCR structure is by this NMOS pipe and NW resistance R nw1 control.

Owing to adopt said structure, SCR structure of the present invention, the trigger voltage in the time of can not only reducing the SCR electrostatic protection effectively, and also its trigger voltage can also carry out freely adjusting as required, thus make things convenient for electrostatic protection design greatly.SCR structure of the present invention; the base width of the PNP pipe that NPN pipe that its parasitic N+/PW/NW forms and P+/NW/PW form can reach minimum as required; thereby the current gain of the common SCR electrostatic preventing structure of forming of PNP pipe that forms of the parasitic NPN pipe that forms of N+/PW/NW and P+/NW/PW can reach maximum, thereby improves the electrostatic leakage ability of whole SCR structure greatly.

Description of drawings

The present invention is further detailed explanation below in conjunction with accompanying drawing and embodiment:

Fig. 1 is existing high trigger voltage thyristor electrostatic preventing structure schematic diagram;

Fig. 2 is existing high trigger voltage thyristor electrostatic preventing structure schematic equivalent circuit;

Fig. 3 is existing electrostatic protection structure for low trigger voltage thyristor schematic diagram;

Fig. 4 is existing electrostatic protection structure for low trigger voltage thyristor schematic equivalent circuit;

Fig. 5 is an electrostatic protection structure for low trigger voltage thyristor schematic diagram of the present invention ();

Fig. 6 is the schematic equivalent circuit of Fig. 5;

Fig. 7 is an electrostatic protection structure for low trigger voltage thyristor schematic diagram of the present invention (two);

Fig. 8 is the schematic equivalent circuit of Fig. 7;

Fig. 9 electrostatic protection structure for low trigger voltage thyristor domain structure of the present invention schematic diagram (one);

Figure 10 is an electrostatic protection structure for low trigger voltage thyristor domain structure schematic diagram of the present invention (two).

Embodiment

As shown in Figure 5, because the NPN pipe that the parasitic NPN that is formed by N+/PW/N+ of NMOS pipe manages with N+/PW/NW by parasitism forms has identical emitter and base stage, when the NPN that is formed by N+/PW/N+ manages triggering and conducting, the also conducting simultaneously of NPN that forms by the N+/PW/NW of parasitism, thus trigger the parasitic PNP pipe that forms by P+/NW/PW and manage the common SCR structure of forming by the NPN that N+/PW/NW forms.Fig. 6 is the equivalent circuit diagram of Fig. 5.

As shown in the figure, electrostatic protection structure for low trigger voltage thyristor of the present invention comprises:

One NMOS pipe is formed among the PW (P trap); The NPN pipe that the parasitic NPN that is formed by N+/PW/N+ of this NMOS pipe manages with N+/PW/NW by parasitism forms has identical emitter and base stage.The drain electrode end of described NMOS pipe is electrically connected with the static end by NW resistance R nw1, and source terminal, gate terminal, substrate terminal are electrically connected with earth terminal.The collector terminal of the NPN pipe that the NMOS pipe is parasitic is electrically connected with the drain electrode end of described NMOS pipe, and the base terminal of the NPN pipe that the NMOS pipe is parasitic is electrically connected by resistance substrate Rpw with the substrate lead end of described NMOS pipe.The emitter terminal of the NPN pipe that the NMOS pipe is parasitic and the source end of described NMOS are electrically connected to earth terminal.

One SCR structure, the parasitic PNP pipe that forms by P+/NW/PW and form jointly by the parasitic NPN pipe that N+/PW/NW forms.The emitter terminal of the parasitic PNP pipe that is formed by P+/NW/PW is connected to the static end by the P+ end, its collector terminal also is simultaneously the base terminal of the NPN pipe of N+/PW/NW formation, pw is connected to earth terminal by the PW resistance R, its base terminal also is simultaneously the collector terminal of the NPN pipe of N+/PW/NW formation, be connected to the static end by NW (N trap) resistance R nw, the parasitic NPN pipe emitter terminal that is formed by N+/PW/NW is connected to earth terminal by the N+ end.

When the leakage (N+) of NMOS pipe/substrate current that the ionizing collision of substrate (PW) knot forms and the product Vbn of resistance substrate Rpw reach the base-emitter conducting voltage of parasitic NPN pipe of N+/PW/N+ formation, the parasitic NPN pipe that N+/PW/N+ the forms conducting that is triggered, because the parasitic NPN pipe that N+/PW/NW forms has identical base terminal and emitter terminal with the NPN pipe that N+/PW/N+ forms, so the NPN that N+/PW/NW forms manages the conducting that also is triggered simultaneously; The collector current of the NPN pipe that N+/PW/NW forms flows through NW resistance R nw and forms voltage difference Vbp, this voltage difference reaches the emitter-base stage cut-in voltage of the PNP pipe of P+/NW/PW formation rapidly, the then parasitic PNP pipe that forms of the P+/NW/PW conducting that also is triggered, and then the conducting that is triggered of described SCR structure.

The triggering of this SCR structure is by NW resistance R nw1 and the decision of NMOS pipe, and the size of NW resistance R nw1 can be adjusted as required.When NW resistance R nw1 reduced, the trigger voltage of SCR reduced, and when the size of NW resistance R nw1 is zero, can equivalence be that the static end directly links to each other with the drain terminal of NMOS then, as shown in Figure 7.Its equivalent circuit diagram as shown in Figure 8.When also needing further to reduce trigger voltage, can suitably reduce the channel length of NMOS pipe.

In Fig. 5 and Fig. 7, the emitter of the NPN pipe of two parasitisms that form by N+/PW/N+ with by N+/PW/NW and the parasitic PNP pipe that formed by P+/NW/PW can lean on very closely with NW as required, thereby reduce the base width of parasitic NPN pipe and PNP pipe, strengthen its current gain, thereby can strengthen the electrostatic leakage ability of whole SCR structure greatly.

Fig. 9 and Figure 10 are two kinds of specific embodiments of the present invention.Fig. 9 is the domain structure schematic diagram of the low trigger voltage SCR electrostatic preventing structure correspondence of adjustable, the high electrostatic leakage ability of trigger voltage shown in Figure 5.Figure 10 is the domain structure schematic diagram of the low trigger voltage SCR electrostatic preventing structure correspondence of high electrostatic leakage ability shown in Figure 7.

Claims

1, a kind of electrostatic protection structure for low trigger voltage thyristor comprises:

One NMOS pipe is formed among the PW, and the NPN pipe that the parasitic NPN that is formed by N+/PW/N+ of this NMOS pipe manages with N+/PW/NW by parasitism forms has identical emitter terminal and base terminal;

One thyristor structure, the parasitic PNP pipe that forms by P+/NW/PW and form by the NPN pipe that the N+/PW/NW of parasitism forms, when the NPN that is formed by N+/PW/N+ managed triggering and conducting, the NPN that is formed by the N+/PW/NW of parasitism managed also conducting; And then trigger described thyristor structure; It is characterized in that:

The drain electrode of described NMOS pipe is electrically connected with the static end by NW resistance R nw1, and the triggering of described thyristor structure is by this NMOS pipe and NW resistance R nw1 control.

2, electrostatic protection structure for low trigger voltage thyristor as claimed in claim 1 is characterized in that: when described NW resistance R nw1 reduced, the trigger voltage of thyristor reduced; When NW resistance R nw1 was zero, the drain electrode of described NMOS pipe directly was electrically connected with the static end.