CN101442039B

CN101442039B - Structure for reducing trigger voltage of silicon control rectifier

Info

Publication number: CN101442039B
Application number: CN200710094264A
Authority: CN
Inventors: 苏庆
Original assignee: Shanghai Hua Hong NEC Electronics Co Ltd
Current assignee: Shanghai Huahong Grace Semiconductor Manufacturing Corp
Priority date: 2007-11-22
Filing date: 2007-11-22
Publication date: 2010-05-26
Anticipated expiration: 2027-11-22
Also published as: CN101442039A

Abstract

The invention discloses a method for reducing trigger voltage of a thyristor. The structure of the thyristor comprises a P trap injection region and an N trap injection region which are parallelly distributed on a P-shaped substrate, wherein an N-shaped injection region is distributed on the surface of a contact zone of the P trap injection region and the N trap injection region; the N-shaped injection region in a range of the P trap injection region is an impurity injection range; and impurities are injected in the impurity injection range so as to realize the function of electrostatic charge discharge. The method reduces voltage of reverse breakdown, solves the problem that an internal circuit fails prior to SCR when the trigger voltage of the SCR is higher than failure voltage of the internal circuit. Therefore, the trigger voltage of the SCR is lower than the failure voltage of the internal circuit, and the internal circuit can not be destroyed by static electricity.

Description

Reduce the structure of trigger voltage of silicon control rectifier

Technical field

The present invention relates to a kind of method that reduces trigger voltage of silicon control rectifier that discharges by electrostatic charge.

Background technology

Static is masty problem for the injury of electronic product always; current popular use SCR (Silicon Controlled Rectifier silicon controlled rectifier protection structure); the basic structure of SCR as shown in Figure 1; comprise silicon substrate 1, also the P trap injection region 2 and the N trap injection region 3 of column distribution are arranged on it.2 close silicon faces are distributed with P type injection region 4 and N type injection region 5 in the P trap injection region, and this P type injection region 4 and N type injection region 5 are connected to negative electrode respectively, have oxide layer isolated area 6 to isolate therebetween.3 close silicon faces also are distributed with P type injection region 4 and N type injection region 5 in the N trap injection region, and this P type injection region 4 and N type injection region 5 are connected to anode respectively, also have oxide layer isolated area 6 to isolate therebetween.Between the P type injection region 4 of the N type type injection region 5 of P trap injection region 2 and N trap injection region 3, isolate by oxide layer isolated area 6.The equivalent electric circuit of its structure comprises two equivalent triodes (NPN type and positive-negative-positive) and two equivalent resistances (P trap resistance R p and N trap resistance R n) between anode and cathode circuit shown in dotted portion among Fig. 1.

Operation principle for the basic structure of SCR, form the reverse breakdown conducting between the N trap that its trigger condition is to connect anode and the P trap that is connected negative electrode, the NPN of enough big current trigger parasitism and base stage and the emitter forward conduction of PNP are provided, enter the forward current magnifying state, common bleed off electrostatic induced current.In carrying out the design of electrostatic charge discharging structure, need to consider that employed structure will satisfy suitable trigger voltage.Trigger voltage generally need be higher than normal working voltage, and must be lower than the ceiling voltage that internal circuit can bear.And the problem of structure shown in Figure 1 is that trigger voltage is very high; this is by the higher decision of knot reverse breakdown between N trap and the P trap; may be destroyed by electrostatic potential for a long time by claimed internal circuit before its conducting, this just is not suitable for applying in the lower circuit of operating voltage.Be the structure of at present more popular two kinds of optimizations as shown in Figures 2 and 3, purpose is in order to reduce trigger voltage.Increased a N type injection region 5 on the surface of P trap injection region and contact zone, N trap injection region among Fig. 2, this structure can reduce a part of trigger voltage.Also increase a polysilicon gate 7 among Fig. 3, formed a NMOS structure, also can discharge a part of electrostatic charge.But the limitation of above-mentioned improvement project is the amplitude of adjusting and is decided by technology, and technology is in case fixing, and then the space adjusted of its trigger voltage is still very little.The present invention has proposed a kind of method of new reduction trigger voltage again on above-mentioned improvement process structure.

Summary of the invention

Technical problem to be solved by this invention provides a kind of method that reduces trigger voltage of silicon control rectifier, and it can solve when the trigger voltage of SCR is higher than internal circuit inefficacy voltage, the problem that internal circuit lost efficacy prior to SCR.Make under situation about original SCR ability not being exerted an influence, make the trigger voltage of SCR be lower than the inefficacy voltage of internal circuit, guarantee the destruction that internal circuit is not subjected to static.

In order to solve above technical problem, the invention provides a kind of method that reduces trigger voltage of silicon control rectifier, the structure of its thyristor comprises: also the P trap injection region and the N trap injection region of column distribution are arranged on the P type substrate, and the surface distributed in P trap injection region and contact zone, N trap injection region has a N type injection region; The scope that N type injection region is positioned at P trap injection region is that impurity injects scope, and implanted dopant in this impurity injection scope is realized the function that electrostatic charge is discharged.

Because the present invention injects the function that realizes the electrostatic charge discharge with impurity, reduce the voltage that finishes reverse breakdown, solved when the trigger voltage of SCR is higher than internal circuit inefficacy voltage the problem that internal circuit lost efficacy prior to SCR.Make under situation about original SCR ability not being exerted an influence, make the trigger voltage of SCR be lower than the inefficacy voltage of internal circuit, guarantee the destruction that internal circuit is not subjected to static.

Description of drawings

Below in conjunction with the drawings and specific embodiments the present invention is described in further detail.

Fig. 1 is the existing SCR structural representation;

Fig. 2 is a kind of improvement structural representation of existing SCR;

Fig. 3 is that the another kind of existing SCR improves structural representation;

Fig. 4 is the structural representation of embodiments of the invention one;

Fig. 5 is the structural representation of embodiments of the invention two;

Fig. 6 is the structural representation of embodiments of the invention three;

Fig. 7 is the structural representation of embodiments of the invention four;

Fig. 8 is the structural representation of embodiments of the invention five;

Fig. 9 is the structural representation of embodiments of the invention six;

Figure 10 is a kind of application circuit schematic diagram of the present invention.

Reference numeral is among the figure, 1, substrate; 2, in the P trap injection region; 3, in the N trap injection region; 4, P type injection region; 5, N type injection region; 6, oxide layer isolated area; 7, polysilicon gate; 8, N type impurity injection region; 9, p type impurity injection region.

Embodiment

SCR basic structure of the present invention comprises silicon substrate 1, and also the P trap injection region 2 and the N trap injection region 3 of column distribution are arranged on it.2 close silicon faces are distributed with P type injection region 4 and N type injection region 5 in the P trap injection region, and this P type injection region 4 and N type injection region 5 are connected to negative electrode respectively, have oxide layer isolated area 6 to isolate therebetween.3 close silicon faces also are distributed with P type injection region 4 and N type injection region 5 in the N trap injection region, and this P type injection region 4 and N type injection region 5 are connected to anode respectively, also have oxide layer isolated area 6 to isolate therebetween.In the surface distributed with contact zone N trap injection region 3 P trap injection region 2 a N type injection region 5 is arranged, this N type injection region 5 is that impurity injects scope in the scope that belongs to P trap injection region 2, can be by implanted dopant in impurity injection scope, realize the function of electrostatic charge discharge, and then reduce trigger voltage.

As Fig. 4 is first embodiment of the present invention, and the impurity of injection is N type impurity, the part of the close N trap injection region 3 of its injection scope in impurity injection scope.

As Fig. 5 is second embodiment of the present invention, and the impurity of injection is p type impurity, the bottom of its injection areas in described impurity injection scope and a side of close P trap injection region 2.

As Fig. 6 is the 3rd embodiment of the present invention, the impurity that injects is N type impurity and p type impurity, the part of the close described N trap injection region of the injection areas of N type impurity in impurity injection scope wherein, N type impurity injection zone in impurity injection scope the bottom and near a side of described P trap injection region.

As Fig. 7 to Fig. 9 is other three embodiment of the present invention, wherein the structure of SCR is based on existing modified model SCR structure shown in Figure 3, the type that its impurity injects is identical with the method for injection zone and Fig. 1 to Fig. 3, if the impurity that injects is N type impurity, the part of the close N trap injection region 3 of its injection scope in impurity injection scope, if the impurity that injects is p type impurity, the bottom of its injection areas in described impurity injection scope and a side of close P trap injection region 2.If the impurity that injects is N type impurity and p type impurity, its injection areas is the stack in above-mentioned two zones.

Figure 10 is an embodiment of SCR structure applications circuit of the present invention, and input voltage is connected to the input of inverter through a resistance R among the figure, and other two ends one end of this inverter is connected with voltage VDD, and the other end directly is connected with ground.SCR anode in this circuit is connected on Input voltage terminal, and negative electrode is connected with ground.In the foregoing circuit, if use general SCR structure, the trigger voltage of this SCR is greater than the inefficacy voltage of the inside reverser of back one-level.Enter from input if any electrostatic charge this moment, flows out from earth terminal, because SCR can't open before one-level inner reverser in back takes place to lose efficacy, the coflow ability of SCR fails to obtain performance, does not reach the purpose of protection internal circuit.If use the present invention's (its structure can be a kind of of any embodiment among Fig. 4 to Fig. 9), for example use SCR structure shown in Figure 4, inject the scope zone at impurity and carry out N type impurity injection (can select for use phosphorus to inject), its knot N side concentration that forms between N type injection region and P trap injection region is increased, reduce the knot reverse breakdown voltage, thereby make the cut-in voltage of SCR drop to below the inner reverser inefficacy voltage, SCR opens coflow prior to internal circuit, and has guaranteed that inner reverser is not destroyed by the ESD electric charge.

Claims

1. structure that reduces trigger voltage of silicon control rectifier, the structure of described thyristor comprises: also the P trap injection region and the N trap injection region of column distribution are arranged on the P type substrate, and the surface distributed in described P trap injection region and contact zone, N trap injection region has a N type injection region; It is characterized in that the scope that described N type injection region is positioned at described P trap injection region is that impurity injects scope, implanted dopant in described impurity injection scope is realized the function that electrostatic charge is discharged.

2. the structure of reduction trigger voltage of silicon control rectifier as claimed in claim 1 is characterized in that, described impurity is N type impurity, the part of the close described N trap injection region of its injection areas in described impurity injection scope.

3. the structure of reduction trigger voltage of silicon control rectifier as claimed in claim 1 is characterized in that, described impurity is p type impurity, the bottom of its injection areas in described impurity injection scope and a side of close described P trap injection region.

4. the structure of reduction trigger voltage of silicon control rectifier as claimed in claim 1, it is characterized in that, described impurity is N type impurity and p type impurity, the part of the close described N trap injection region of the injection areas of described N type impurity in described impurity injection scope, a described N type impurity injection zone bottom in described impurity injection scope and a side of close described P trap injection region.