JPH04165666A - Clip diode device - Google Patents

Abstract

PURPOSE:To enable a large clip current to flow while reducing the wasteful substrate current by a method wherein the second diffused region of the first conductivity type in high concentration and the third diffused region of the first conductivity type in high concentration formed on a well region and connected to the reference voltage are provided. CONSTITUTION:A bipolar transistor Tr1 is formed of the second diffused region 19, a well region 11 and the third diffused region 15. On the other hand, the base of this bipolar transistor Tr1, i.e., the well region 11 is connected to the base of a parasitic transistor Tr2. Accordingly, a clip current runs in the base.emitter circuit of the bipolar transistor Tr1 in addition to the base emitter.circuit of the parasitic transistor Tr2 from the second diffused region 19 to the third diffused region 15 through the collector.emitter channel of the bipolar transistor Tr1 thereby enabling the clip current to be augmented. Through these procedures, the title clip diode with simple structure and high efficiency can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a clip diode device, and more particularly to a highly efficient clip diode device suitable for protecting transistors and the like in integrated circuit (IC) devices.

[Prior Art 1] In integrated circuit devices, clipping diodes are commonly used to protect transistors or to limit signal voltage levels within a predetermined range.1 For example, FIG. An example in which a clip diode 3 is used in the output section 1 of the pump circuit is shown. In other words, the charge pump circuit shown in the figure generates and outputs, for example, a -1OV t' source from a +5■ power supply ■DD. It is S. An example of such a single charge positive circuit is the integrated circuit MC145407 manufactured by Motorola. In the circuit shown in Fig. 4, ■ss” pressure output terminal 5
If the voltage reaches a stop value for some reason, an extra current may flow into the output i-rangestaff of the output section 1 of the charge pump circuit, possibly destroying the transistor 7 and the like. Measures to prevent such inconveniences
A clip diode 3 is connected between the output terminal 5 and the ground (GND) so that the potential of the power supply terminal E 5 does not become a positive value. A device having a structure as shown in Fig. 5 was not used.

The diode device shown in FIG. 5 is formed on, for example, an N-type semiconductor substrate 9, which may be an N-type epitaxial layer formed on a P-type conductive substrate. That is, a p-type well 11 is formed on the top of the N- type substrate 9, and a p-type well 11 is formed on the top of the F)-type well 11, respectively.
P-type and N1- type diffusion regions 13 and 15 are formed. Also, N-〒1 outside of P~ type Twell 1
An N+ type diffusion layer I7 is formed on the upper part of the substrate 9.

In such a diode device, the N4 type diffusion layer 1
For example, a +5■ power supply ■DD is applied to 7, a 10V power supply N·'SS, for example, is connected to the -P 10-type diffusion layer 13, and the N4- type diffusion layer 15 is connected to the ground.
Therefore, P between the P-type well 11 and the N-type diffusion layer 15
The N junction acts as a clip diode, and eventually the current a
A circuit configuration in which a clip diode is connected between vss and ground is realized.

[Problems to be Solved by the Invention] However, in the above diode device, as shown in FIG. Parasitic bipolar transistor T
r will be formed.

Then, ■, Sf, when the source line has a positive potential, P
Crimp current 1 is applied from the + type diffusion layer 13 to the N type diffusion layer 15.
s flows. On the other hand, since the clipping current IB is the base current of the transistor Tr, a collector current (2) flows from the substrate 9 (VDD) to the N-type diffusion layer 15, that is, to the ground. Or it will flow. This ■. The value of 1-base current IB of transistor Tr becomes t-, and becomes Iac fe to .h'. That is, in the conventional diode device, a wasteful current flows from the substrate to the ground, and this current increases as the clip current IB increases.

SUMMARY OF THE INVENTION An object of the present invention is to provide a highly efficient clip diode device that does not reduce wasteful substrate current and allows a large rip current to flow, in view of the problems with the conventional diode devices described above.

1 Means for Solving the Problems J In order to solve the above problems, a clip diode device according to the present invention includes a semiconductor substrate of a first conductivity type and a second semiconductor substrate of a low concentration formed on the semiconductor substrate. a well region of a conductivity type of -L, a first diffusion region of a high concentration second conductivity type formed in the well region -L and connected to a power supply line or a signal line to be clipped, and a first diffusion region of a second conductivity type formed on the well region. and a second conductivity type of the first conductivity type having a high fourth degree and connected to the first diffusion region.
and a third diffusion region of the first conductivity type with high drift, which is formed on the well region and connected to a reference potential.

Further, in the clip diode device according to a second aspect of the present invention, the clip diode device is formed on the well region between the second diffusion region and the third diffusion region with an insulating film interposed therebetween; It has a gate electrode connected to the diffusion region.

[Operation] In the crimp diode device described in L, a bipolar transistor is formed by the second diffusion region, the well region, and the third diffusion region. The base of this bipolar transistor, ie, the well region, is connected to the base of a parasitic transistor formed by a conventional semiconductor substrate, a well region, and a third diffusion region. Therefore, the clip current flowing from the first diffusion region through the well region to the third diffusion region flows through the base-emitter circuit of the bipolar transistor in addition to the base-emitter circuit of the conventional parasitic transistor. Therefore, the base current, and therefore the collector current, flowing through the conventional parasitic transistor is reduced, and the substrate current flowing from the semiconductor substrate through the well region and the third diffusion region is reduced.

Further, since current flows from the second diffusion region to the third diffusion region through the collector-emitter path of the bipolar transistor, it is possible to increase the clip current compared to the conventional device.

Furthermore, in the clip diode device according to the second aspect, the gate t'! is located on the well region between the second and third diffusion regions. #! , and MO8I-
Since a run transistor is formed, a clip current further flows from the second diffusion region to the third diffusion region through this MOS transistor. Therefore, it is possible to further increase the clipping current and to crimp the forward direction of a power supply line or the like to a voltage lower than that of a conventional PN junction.

[Example number Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 shows a schematic structure of a diode device according to an embodiment of the present invention. In the device shown in FIG. 1, another N medium diffusion layer 19 is formed in the upper part of the P− type well 11 in the device of the fifth section, for example, in the middle part between the p+ type diffused layer 13 and the N− type diffusion layer 15. , this N-+ type diffusion layer 19 is expanded to P soil type.
It is connected to the first layer 13, that is, the electric wire 'JJAV'. The other parts of A are the same as the apparatus shown in FIG. 5, and the same parts are designated by the same reference numerals.

In the diode device of FIG. 1, a parasitic transistor 1'r2 similar to the parasitic transistor T"r of FIG.
An N-type substrate 9, a P-type well 11, and an N-type diffusion layer 15.
It is formed by. However, in the diode device shown in FIG.
In addition to 2, N+ type scattered layer 19P- type well 11 and N+
Another bipolar transistor T by type scattering layer 15
r ] is formed. These transistors Tr L and Tr 2 have bases, i.e. P-type transistors 1,
and the emitter, that is, the N+ type diffusion layer I5, are common to each other. 6 Therefore, the clip current IaS flowing from the power supply I is shunted to the base-emitter circuit of transistors Tr 1 and Tr 2, and the N+ type diffusion layer is Layer 15 flows. Therefore, the substrate current I flowing from the N- type substrate 9 through the transistor Tr2 to the N+ type diffused layer 15 becomes smaller than the rate at which the base current of the transistor Tr2 decreases. That is, the wasted current I (Fig. 6) in the conventional diode device is divided into the current 'C1, which flows through the collector-emitter path of transistor Trt, and the current 'cv, which flows through the collector-emitter path of transistor Trt. .That is, i + I = h -1 + h ・■cl
cv feL B fev B=(
h1h)・I fe! , fev 8 , where hfe1 is h of transistor Tr 1
t8i amplification factor), and hfev is the transistor Tr
2 h 1 e.

Therefore, for example, if hfeL "" hfev, the conventionally wasted substrate current I can be halved. Further, the clipping current becomes IB+■at-, which is increased compared to the conventional diode device, and the clipping performance is further improved.

FIG. 2 shows a diode device according to a second embodiment of the invention. In the diode device shown in the figure, a gate electrode 21 is formed of, for example, polycrystalline silicon through an insulating film (not shown) in the P- type well 11f between one N++ diffusion region and the N++ diffusion region 15 of the diode device shown in FIG. This is what I did. This gate t&21 is connected to, for example, one N medium-sized diffusion layer, and then to the power supply ■ss. The other parts are diode equipment as shown in Figure 1! , and identical parts are given the same reference numerals.

In the diode device shown in FIG. 2, a clipping current of S 1 +IC flows from the source to the ground due to the same structure as in FIG. C■ has been reduced. Furthermore, in the diode device of FIG. 2, the N type diffusion layer 19.1.5 and the gate electrode 2
1 forms a MOS transistor, and a current IDS flows through a channel formed under the gate electrode 21. Therefore, the clipping current becomes ■±■+ID5 B cl , further improving the clipping performance. Also, power supply ■s
Since the MOS)-transistor is connected between S and the ground, the clip voltage of the power supply 3S can be made even smaller than the forward voltage of the conventional PN junction. Note that FIG. 2(b) shows the N+ type scattering layer 1915 and the gate electrode 21.
FIG. 2(c) shows a comprehensive equivalent circuit between the power supply VSS and ground.

FIG. 3 shows a diode device according to still another embodiment of the present invention.
As shown in FIG. 2A, the conductivity types of the respective semiconductor regions of the diode device shown in FIG. 2A are made to have opposite polarities. That is, an N- type well 25 is formed on a P- type substrate 23, and an N++ diffusion region 27, a P+ type diffusion region 29.31, and a gate electrode 33 are formed on the N- type well 25.
6 In addition, FIG. 3(b) shows an equivalent circuit of the MOS transistor constituted by the P type diffusion layer 29, 31, gate electrode 33, etc. in FIG. 3(a). (c) shows a comprehensive equivalent circuit between terminal A, that is, the N+ type diffused layer 27, and terminal B, that is, the P0 type diffused layer 31. Note that in the diode device of FIG. Terminal B is connected to, for example, ground, and terminal A is connected to a signal or a power source that has a positive potential under normal operating conditions.

[Effect of the invention 1 As described above, according to the present invention, with a simple structure, unnecessary substrate current can be reduced by half, and the clip current can be greatly increased and the clip voltage can be lowered compared to the conventional one. It becomes possible to further reduce the amount. That is,
A highly efficient clip diode can be realized with a simple structure.

Furthermore, the diode device according to the present invention is easier to manufacture than conventional diode devices, which do not require similar special processes and structures.

Furthermore, since the wasteful flow flowing through the substrate is reduced, so-called latch-up is less likely to occur.

Note that the diode device according to the present invention can be used in protection circuits for output transistors, input transistors, and others on integrated circuit devices, and can also be used for various purposes such as controlling and limiting signal voltage levels.

[Brief explanation of drawings]

FIG. 1 is a partial cross-sectional view showing the general structure of a diode device according to one embodiment of the present invention, and FIG. 2(a) shows the structure of a diode device according to a second embodiment of the present invention. A partial cross-sectional view, FIG. 2(b) is an electric circuit diagram showing an equivalent circuit of the MOS transistor part in the device shown in FIG. 2<a>, and FIG. FIG. 3(a) is a partial cross-sectional view showing a diode device according to a third embodiment of the present invention, and FIG. 3(b) is an electric circuit diagram showing an overall equivalent circuit of the diode device. FIG. 3(c) is an electric circuit diagram showing the equivalent circuit of the MO3I-transistor part in the device of FIG. 3(a), and FIG. 3(c) is an electrical circuit diagram showing the overall equivalent circuit of the diode device of FIG. 3(a). , Fig. 4 is an electric circuit diagram showing an example of the use of a clip diode, Fig. 5 is a partial cross-sectional view showing the structure of a conventional diode device, and Fig. 6 shows the operation of the diode device of Fig. 5. FIG. 9; N- type substrate, 1, 1, P- type well, 13; P-type diffusion region, 15.17.1.9: N++ diffusion region, 21; gate electrode, 23, P- type substrate, 25. N-type well, 27: N+ type diffusion region, 29.31; P+ type diffusion region. Patent applicant: Motorola Japan Co., Ltd. Agent: Patent attorney Yoshi Ikeuchi Disciple 1 Figure 2 (b) (... Figure 3 (a) (b) (C) Figure 4

Claims (1)

[Claims] 1. A semiconductor substrate of a first conductivity type, a low concentration well region of a second conductivity type formed on the semiconductor substrate, and a power supply formed on the well region to be clipped. a first diffusion region of a highly doped second conductivity type connected to the line or signal line; and a first diffusion region of a highly doped first conductivity type formed on the well region and connected to the first diffusion region. A clip diode device comprising: a second diffusion region; and a third diffusion region of a highly concentrated first conductivity type formed on the well region and connected to a reference potential. 2. A claim further comprising a gate electrode formed on the well region between the second diffusion region and the third diffusion region via an insulating film and connected to the second diffusion region. The clip diode device according to item 1.