JP2579989B2 - Electrostatic discharge protection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] Regarding an electrostatic discharge protection device for a semiconductor integrated circuit, a sub-earth or an element isolation region (isolation region) is also used as a part of a protection element to effectively use the element region. intended to achieve, the second n ⁺ region is formed around the first diode formed in the first P ⁺ region and the n ⁺ region, further said 2 n ⁺
Around the region, a second P ⁺ region is formed which forms a second diode at a side junction with the second n ⁺ region and also serves as a sub-earth and an element isolation region, and the first P ⁺ region is formed. ⁺ Region and the second n ⁺ region are short-circuited.

[Industrial applications]

The present invention relates to an electrostatic discharge protection device for a semiconductor integrated circuit (for example, a memory).

[Conventional technology]

Generally, a circuit as shown in FIG. 5 is often used as this kind of electrostatic discharge protection device. In FIG. 5, T
Is an external input terminal (or output terminal) for a predetermined internal circuit (for example, a memory or the like). Diodes D1 and D2 are connected to a wiring extending from the terminal T to the internal circuit. On the other hand, the anode side of the diode D2 is the potential V applied to the semiconductor substrate.
_EE (eg -5.2V, usually referred to as sub-earth) is applied.

Thus, in the process of assembling the integrated circuit,
Positive electrostatic charge entering from the external terminal T through the human body or package is flowed to the ground side via the diode D1, whereas the negative side of the static electricity the terminal T side from Sabuasu V _EE side via the diode D2 This suppresses a large potential change of the terminal due to the static electricity, and protects the internal circuit from electrostatic breakdown.

Note that a reverse bias potential is always applied to the diode, and the diode has no effect on the internal circuit.

In this case, when forming the diode in the semiconductor substrate, a configuration as shown in FIG. 6 is usually used. That is, in FIG. 6, 71 is a P ^{− type} semiconductor substrate, 72 is an n ^{+ type} buried layer, 73 is an n ^{− type} epitaxial layer,
74 and 75 are n ^{+ type} and P ^{+ type} diffusion regions, 76 is an insulating film such as a silicon oxide film, 77 and 78 are aluminum wiring terminals, respectively, and the P ^{+ type} diffusion layer 75 and
A diode is formed at the junction with n ^{+ type} buried layer 72.

Figure 7 is intended to illustrate the configuration of the electrostatic discharge protection device in the prior art utilizing the configuration of the diode, in said Figure 7, the P 51 ^- type semiconductor substrate, 52 and 53 are n ⁺ Katachiuma Included layer, 54 is the n ^- type epitaxial layer, respectively 55 and 56
In the n ^{+ -type} and P ^{+ -type} diffusion regions, the diode D1 is formed at the junction between the P ^{+ -type} diffusion region 56 and the n ^{+ -type} buried layer 52. 57
Is a P ^{+ type} isolation region (element isolation region), which is formed so as to surround the internal region thereof. Further, 58 and 59 are n ^{+ type} and P ^{+ type} diffusion regions, respectively, and the diode D2 is the P ^{− type} semiconductor substrate 51 and the n ^{+ type} buried layer 53.
Formed at the junction with Reference numeral 60 denotes an insulating film such as a silicon oxide film, and reference numeral 61 denotes a wiring terminal on the anode side of the diode D2, which is a terminal on the sub-earth side to which a substrate potential V _EE (for example, −5.2 V) is applied. Reference numeral 62 denotes an external input / output terminal T connected to the internal circuit via an aluminum wiring, and is connected to the anode side of the diode D1 and the cathode side of the diode D2. 63 is a cathode-side wiring terminal for the diode D1 and is a ground-side terminal to which a ground potential is applied.

[Problems to be solved by the invention]

According to the prior art arrangement shown in the FIG. 7, the terminal of Sabuasu side (V _EE is applied) 61
And the terminal 63 on the ground potential side is a protection element (diode
D1 and D2) parts are far apart and the parasitic resistance of each diode (connected in series with each diode)
Therefore, the voltage due to the static electricity directly applied to each protection element (junction of each diode) drops to degrade the electrostatic breakdown protection characteristic, and by providing the above-mentioned isolation region (element isolation region). increasing the area of the entire protective device further P ^- type semiconductor substrate and the n ⁺ -type buried layer
It is difficult to make the capacity of the diode D2 formed at the junction with the 53 sufficiently large, and there is a problem that the electrostatic withstand capacity against static electricity on the negative side is reduced.

The present invention has been made to solve such a problem, and the sub-earth region and the isolation region are integrally formed as a part of a protection element (in this case, a diode D2) so that the element area can be effectively used. reducing the parasitic resistance of each diode strive further above V _EE
The capacity of the diode D2 on the side is also made sufficiently large, so that the electrostatic resistance against static electricity on the negative side is also increased.

[Means for solving the problem]

According to the present invention for solving the above-mentioned problems, the first P ⁺
The second n ⁺ region is formed around the first diode formed in the region and the n ⁺ regions, further around the second n ⁺ region, side junction between the second n ⁺ region A second P ⁺ region which also forms a second diode and also serves as a sub-earth and an element isolation region is formed, and the first P ⁺ region and the second n ⁺
An electrostatic discharge protection device is provided that is shorted to an area.

(Operation)

According to the above configuration, the first n ⁺ region is the diode D1
The first (corresponding to the cathode side (ground potential side) of the (positive-side static electricity protection element), which is short-circuited to each other.
P ⁺ region and the second n ⁺ region
Corresponding to the anode side of the external input / output terminal T corresponding to the cathode side of the diode D2 (a protection element against static electricity on the negative side).
Connected to. By further forming a second P ⁺ region around the second n ⁺ region, and these second n ⁺ region
The capacitance of the diode D2 formed at the side junction of the P ⁺ region can be made sufficiently large, and the second P ⁺ region corresponds to the anode side (sub-earth side) of the diode D2,
It also functions as an isolation region.

〔Example〕

FIG. 1 shows an electrostatic discharge protection device according to one embodiment of the present invention, in which 11 is a P ^{− type} semiconductor substrate, 12 is an n ^{+ type} buried layer,
13 the n ^- type epitaxial layer, 16 is the P ⁺ diffusion region 17 in the n ⁺ type diffusion region formed in an upper portion of the diffusion region 16, the diode D1 is formed at the junction of the diffusion regions 16 and 17 You. Reference numeral 15 denotes an n ^{+ type} diffusion region formed around the P ^{+ type} diffusion region 16,
The diffusion regions 15, 16 are both aluminum wiring terminals 20, 2.
It is connected to the external input / output terminal T via 0 '. In other words, the diffusion regions 15 and 16 and the buried layer 12
Are short-circuited to each other and correspond to a connection point between the anode side of the diode D1 and the cathode side of the diode D2.

Reference numeral 14 denotes a P ^{+ -type} diffusion region formed around the n ^{+ -type} diffusion region 15, and a junction formed on the side surface (peripheral surface) of the diffusion regions 14 and 15 functions as a diode D2. Where
The P ⁺ diffusion region 14 is functioning as isolation regions, and further connected to the diffusion region 14 is wiring terminals 19 and 19 the substrate potential V _EE is applied ', also functions as a so-called Sabuasu region I have. That is, the P ^{+ type} diffusion region 14 is a constituent element of the diode D2 which is a protection element,
It also functions as a sub-earth area and an isolation area. The n ^{+ -type} diffusion region 17, which is a component of the diode D1, is connected to a wiring terminal 21 to which a ground potential is applied, and reference numeral 18 denotes an insulating film such as a silicon oxide film.
Although the conventional diffusion technique for collector contact is used for forming the n ^{+ type} diffusion region 15, it is not used as a conventional collector contact region.

By utilizing the diffusion region 14 serving as both isolation and sub-earth and the Pn junction formed on the side surface of the diffusion region 15 for the diode D2, the capacitance of the diode D2 is sufficiently increased and the parasitic resistance is reduced. Thus, the resistance to negative static electricity can be improved.

2 and 3 show plan views of the diffusion regions 14 to 17 in FIG. 1, respectively, and may have a square or rectangular planar structure as shown in FIG. Also, a concentric plane structure as shown in FIG. 3 can be used. In the case of a concentric plane structure as in the latter, electric field concentration can be avoided,
This is advantageous in preventing the destruction of the element due to this.

FIG. 4 shows an electrostatic discharge protection device as another embodiment of the present invention. In FIG. 3, reference numerals 11 to 15 correspond to reference numerals 11 to 15 in FIG. the P ⁺ region 16 for constituting a 'is formed by using the base diffusion process or resistance diffusion process, the diode D1 is formed at the junction between the n ⁺ type diffusion region 17 formed thereon You.
Reference numerals 18 to 21 correspond to reference numerals 18 to 21 in FIG.

〔The invention's effect〕

According to the present invention, the sub-earth region, the isolation (element isolation) region, and the P ⁺ region of the protection diode D2 against negative static electricity can be covered by one P ⁺ diffusion region. As a result, the parasitic resistance of each diode decreases, and the withstand voltage against static electricity can be improved. Further, since the Pn junction formed on the side surface of the P ⁺ diffusion region is used as the diode D2, the capacitance of the diode D2 can be increased, and in particular, the resistance to negative static electricity can be increased. And all IC
Normal processes for manufacturing (element isolation diffusion, collector compensation diffusion, base diffusion, resistance diffusion, etc.) may be used, and no special steps are required to form the present device.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an electrostatic discharge protection device according to one embodiment of the present invention. FIGS. 2 and 3 are diagrams each exemplifying a planar structure of a main part of FIG. 1, FIG. Is a sectional view showing an electrostatic discharge protection device as another embodiment of the present invention, FIG. 5 is a general circuit diagram of this type of electrostatic discharge protection device, and FIG. FIG. 7 is a diagram illustrating a configuration of a diode used in the electrostatic breakdown protection device. FIG. 7 is a diagram illustrating a configuration of this type of electrostatic breakdown protection device according to the related art. (Explanation of reference numerals) 11, 51, 71: semiconductor substrate, 12, 52, 53, 72: n ^{+ type} buried layer, 14: P ^{+ type} diffusion region for both isolation and sub-earth, 15: P ^{+ type} region 14 N ^{+ type} diffusion region forming diode D2, 16, 16 ': P ^{+ type} diffusion region forming diode D1, 17: n ^{+ type} diffusion region forming diode D1, 57: isolation region, 59 : P ^{+ type} diffusion area on sub-earth side.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical indication location H01L 27/04 27/088 27/092

Claims (1)

(57) [Claims] 1. A second n ⁺ region around the first diode formed in the first P ⁺ region and the n ⁺ region is formed, further around the second n ⁺ region, said A second P ⁺ region is formed at a side junction with the second n ⁺ region and also serves as a sub-earth and an element isolation region, and the first P ⁺ region and the second P ⁺ region are formed. An electrostatic discharge protection device, wherein the n ⁺ region is short-circuited.