JPH06151717A - Ic with built-in protective circuit and ic for driving display device - Google Patents

Abstract

PURPOSE:To miniaturize a protective circuit by reducing the area occupied by the circuit by a method wherein the considerable part of the region designated to the protective circuit is concurrently used as the region for a diode in addition to the region for a transistor. CONSTITUTION:A field transistor Tr 1 is composed of a region 131 as a drain, a part of a wiring 11a located above a field oxide film 132 as a gate, a part of the P-type substrate 135 as a channel and a region 133 as a source. Also, a region 134 is connected to a wiring 12a together with the region 133. As a result, a diode D1, having the direction from the wiring 12a to the wiring 11a as forward direction, is composed of the P-type region 134, the P-type substrate 135 and an N-type region 131. The region 131 is used not only as the drain region of the field transistor Tr 1, but also it is used as the anode region of the diode D1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protection circuit built-in IC and a display device driving IC, and more particularly to a built-in protection circuit having a protection circuit between two external terminals in order to protect the internal circuit from electrostatic breakdown. The present invention relates to an IC and a display device driving IC.

[0002]

2. Description of the Related Art An IC may receive an undesired voltage from the outside due to discharge or the like at its external terminal. A typical example of this is the case where the static electricity charged in the human body is discharged to the touched IC. In such cases, IC
The internal circuit of may be destroyed. Especially high insulation M
In an IC having an OS transistor, internal circuits are often destroyed. This is because the reverse voltage or excessive voltage is undesirably applied to the original voltage applied to the elements of the internal circuit, especially between the external terminals for power supply and ground, and open drain. Such a situation is likely to occur when the output external terminal or the like is discharged. Therefore, in order to protect the internal circuit from such an undesired voltage, a protection circuit is provided between these external terminals in the IC.

FIG. 2 shows a specific example of the protection circuit. I
In C10, the protection circuit 13 is composed of a diode D1 and a transistor Tr1 connected in parallel, and has an external terminal 11 for a power supply Vcc and a ground GND for supplying a power supply voltage to an internal circuit (not shown). Is provided between the external terminal 12 and the external terminal 12. The diode D1 is the external terminal 1
When a reverse bias voltage is applied between the external terminal 1 and the external terminal 12, the current flowing from the external terminal 12 to the external terminal 11 is passed as the forward current.

On the other hand, the threshold level of the transistor Tr1 is set to a predetermined value which is equal to or higher than the operating voltage of the internal circuit and is equal to or lower than the withstand voltage. When an undesired high voltage is applied between the external terminals 11 and 12, the current flowing from the external terminal 11 to the external terminal 12 is bypassed. This protects the internal circuit. In the same manner, the diode D2 and the transistor Tr2
With the protection circuit 16 including
The transistor Tr3 is protected from an undesired voltage applied between the external terminal 14 and the external terminal 15 for driving D and the like.

FIG. 3 shows a conventional specific structure of the protection circuit 13. Here, the part indicated by hatching is
It is a field oxide film. The wiring is indicated by a thick line so as to clearly show the area under the wiring. In addition, an equivalent circuit for a region corresponding to the broken line is also added in the cross-sectional view. The diode D1 and the transistor Tr1 of this protection circuit 13 are
Although they are provided adjacent to each other, independent regions are assigned to each and they are connected in parallel by wiring. And each shares the above-mentioned protection function.

[0006]

As described above, in the conventional protection circuit built-in IC and display device driving IC, a protection circuit including a diode and a transistor is provided between two external terminals connected to the internal circuit to be protected. Have. However, such a protection circuit is required to be able to flow a large current even in the worst possible state. Otherwise, the internal circuit cannot be protected. Therefore, the area occupied by this protection circuit tends to be large. Although only one diode and one transistor are shown on the circuit symbol, each occupies a considerably large area corresponding to the maximum current. Therefore, the area of the entire protection circuit provided in these individual regions is not so small that it can be ignored as compared with the area of the internal circuit.

When the ratio of the protection circuit in the IC chip is large as described above, the IC chip with the protection circuit becomes large and the yield of the IC decreases. This is inconvenient because the productivity is not good. The purpose of this invention is
In order to solve the problems of the conventional technology,
Built-in protection circuit with built-in protection circuit of compact structure I
It is to realize C and a display device driving IC.

[0008]

The structure of an IC with a built-in protection circuit of the present invention which achieves the above object has a first external terminal, a second external terminal, a first circuit, a diode and a transistor, The first circuit operates by receiving an operating voltage of a predetermined voltage level via the first external terminal and the second external terminal, and the diode is connected to the first external terminal and the second external terminal. When a voltage opposite to the operating voltage is applied between the second external terminal and the first external terminal, a current having a direction following the direction of the opposite voltage is forwarded between the second external terminal and the first external terminal. The first circuit is protected from the reverse voltage by flowing as a directional current, and the transistor has the same direction as the operating voltage applied between the first external terminal and the second external terminal. Of the voltage to be protected When the voltage reaches a predetermined voltage level that is equal to or higher than the voltage and is equal to or lower than the withstand voltage of the first circuit, bypasses a current in a direction that follows the same voltage direction between the first external terminal and the second external terminal. By doing so, the protection circuit built-in IC protects the first circuit from an overvoltage in the same direction as the operating voltage between the first external terminal and the second external terminal. Type (or P type) source or drain first
Of the P-type (or N-type) third region adjacent to the first region in a region adjacent to the second region of the other of the source and the drain, which is adjacent to the first region. A region is provided, and a portion including the second region and the third region also serves as the diode,
The diode and the transistor are integrally formed.

[0009]

The IC having the protection circuit of the present invention having such a structure
In this case, the protection circuit is composed of a diode and a transistor formed integrally, and a considerable part of the area is used not only as an area for a transistor but also as an area for a diode. Therefore, the area occupied by the protection circuit of the present invention is smaller than the area occupied by the protection circuit in which the diode and the transistor are formed in separate regions, by the area of the above-mentioned combined use region. As a result, it is possible to realize an IC with a built-in protection circuit which has a compact protection circuit.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a concrete structure of a protection circuit which is a characteristic part of an embodiment of an IC having a protection circuit according to the present invention. (A) is a plan view thereof, and (b) is a cross-sectional view thereof, and these are shown in a schematic view because it is difficult to understand from a measured view. The portion highlighted by hatching is the field oxide film. Further, the wiring is shown by a thick line in order to clearly show the region under the wiring, but in the sectional view, the wiring pattern of the electrode portion is also shown by a broken line and overlapped with the thick line of the wiring. Further, in the cross-sectional view, an equivalent circuit for a corresponding region is also indicated by a broken line for reference.

Here, 131 is an N-type region to which the wiring 11a which should receive the power supply voltage Vcc is connected through the external terminal (see 11 in FIG. 2) during the original operation of the IC, and 132
Is also a field oxide film as a gate insulating film under the gate to which the wiring 11a is connected, and 133 is an N type to which the wiring 12a to be grounded is connected via another external terminal (see 12 in FIG. 2). Area. These are so-called field using the region 131 as a drain, a part of the wiring 11a above the field oxide film 132 as a gate, a part of the P-type substrate 135 immediately below the field oxide film 132 as a channel, and a region 133 as a source. The transistor Tr1 is formed.

Reference numeral 134 denotes a region adjacent to the region 133, which is a P-type region provided adjacent to the region 133 in the region opposite to the region 131. This area 134 is connected to the wiring 12a together with the area 133. As a result, the P-type region 134, the P-type substrate 135, and the N-type region 131 are connected to the wiring 12a to the wiring 11
A diode D1 whose forward direction is a direction toward a is configured. In this example, these areas 131, 133, 1
Although 34 is provided on the P-type substrate 135, it may be provided on the P-type well.

In this way, the field transistor Tr1
By also providing the region 134 adjacent to the source region 133, the field transistor Tr1 and the diode D1 are integrally formed, and the region 131 is used not only as the drain region of the field transistor Tr1 but also as the anode region of the diode D1. Can be used. Therefore, since it is not necessary to separately allocate the anode region of the diode D1, the area occupied by the entire protection circuit can be reduced. Further, as the area is reduced, the area required for wiring to the area is reduced, and thus the area occupied by the protection circuit can be reduced.

Next, the operation of the protection circuit composed of the diode D1 and the transistor Tr1 having such a configuration will be described.
The diode D1 is originally connected to the external terminal (11) that should be placed on the relatively positive voltage side, and the wire 11a that is connected to the external terminal (12) that is originally placed on the relatively negative voltage side. When a reverse voltage is applied between the wiring 12a and the wiring 12a, a current flowing from the wiring 12a to the wiring 11a is passed as a forward current.

Therefore, the reverse voltage is applied to the diode D1.
It is suppressed to an extremely small level corresponding to the forward drop voltage of. Therefore, due to the action of the diode D1, almost no voltage opposite to the operating voltage of the internal circuit is applied to the internal circuit provided between the wiring 11a and the wiring 12a. This protects the internal circuit from unwanted reverse voltage.

Since the transistor Tr1 is a so-called field transistor having the field oxide film 132 as a gate film, the voltage applied between the wiring 11a and the wiring 12a does not conduct at about the operating voltage of the internal circuit. However, the threshold level conducts when the internal circuit has a withstand voltage or less. This is the field oxide film 1
It can be easily set by adjusting the concentration of the so-called channel stopper immediately below 32. Then, when an undesired high voltage that would exceed the breakdown voltage of the internal circuit if the transistor Tr1 is not applied is applied between the wiring 11a and the wiring 12a, the wiring 11a to the wiring 1
The current flowing toward 2a is bypassed.

Therefore, the high voltage in the forward direction is suppressed below the withstand voltage of the internal circuit corresponding to the threshold level of the transistor Tr1. Therefore, the wiring 11a and the wiring 1
An undesirably large forward high voltage exceeding the withstand voltage of the internal circuit is not applied to the internal circuit provided between the internal circuit 2a and 2a. As a result, the internal circuit is protected from an excessive voltage in the same direction as the operating voltage. When the power supply voltage of the original operating voltage level is applied between the wiring 11a and the wiring 12a, neither the diode D1 nor the transistor Tr1 conducts, so that the protection circuit prevents normal operation of the internal circuit. There is no inconvenience.

As described above, by providing the protection circuit in which the transistor for coping with the high voltage in the same direction as the operating voltage of the internal circuit and the diode for coping with the voltage in the opposite direction are integrally formed compactly, , The protection circuit built-in IC of the present invention does not impair its performance and function,
The chip size is small. The case where the protection circuit having the N-type MOS transistor is provided between the external terminals for the power supply has been described above as an example, but the case where the protection circuit having the P-type MOS transistor is provided is almost the same. When the protection circuit is provided between the input / output external terminals as in the second protection circuit 16, the same operational effect is obtained. Although it has been described that the diode is formed in combination with the transistor, this is simply because the transistor has been described above for convenience of explanation, and the same is true when the transistor is formed in combination with the diode. It may be formed as. The present invention is also suitable for driving a display device, and when applied to such an object, it is realized as a display device driving IC.

[0019]

As can be understood from the above description, in the present invention, a considerable part of the region assigned to the protection circuit is used not only as the region for the transistor but also as the region for the diode. . As a result, the area occupied by the protection circuit can be made smaller by the area of the shared area than that when the diode and the transistor are individually formed, and the protection circuit can be made compact. Therefore, it is possible to realize an IC with a built-in protection circuit that has a compact protection circuit, and as a result,
The chip size of the protection circuit built-in IC is reduced, the yield is increased, and the productivity is improved.

[Brief description of drawings]

FIG. 1 is a structural explanatory view of an embodiment of an IC with a protection circuit according to the present invention.

FIG. 2 is an explanatory diagram at a circuit level regarding an IC having a protection circuit.

FIG. 3 is a structural explanatory diagram of a conventional IC with a built-in protection circuit.

[Explanation of symbols]

 10 IC 11, 12 External Terminal 13 Protection Circuit 14, 15 External Terminal 16 Protection Circuit 131 N-type Region 132 Field Oxide Film 133 N-type Region 134 P-type Region 135 P-type Substrate

Claims (2)

[Claims] 1. A first external terminal, a second external terminal, a first circuit, a diode, and a transistor, wherein the first circuit includes the first external terminal and the second external terminal. Is operated by receiving an operating voltage of a predetermined voltage level through the diode, and the diode is applied with a voltage opposite to the operating voltage between the first external terminal and the second external terminal. Protecting the first circuit from the reverse voltage by causing a current in a direction following the reverse voltage direction to flow as a forward current between the second external terminal and the first external terminal. When the voltage in the same direction as the operating voltage applied between the first external terminal and the second external terminal reaches a voltage to be protected, the transistor has the first external terminal and the second external terminal. To the same direction of voltage between the external terminals of An IC with a built-in protection circuit that protects the first circuit from an overvoltage in the same direction as the operating voltage between the first external terminal and the second external terminal by bypassing the current in the positive direction. And one of the N-type (or P-type) source and drain of the transistor is a first region, and the other one of the source and the drain is a second region, with respect to the first region. And a third region of P-type (or N-type) is provided on the opposite side of the second region adjacent to the first region, and includes the second region and the third region. Also functions as the diode, whereby the diode and the transistor are integrally formed. 2. A first external terminal, a second external terminal, a first circuit, a diode, and a transistor, wherein the first circuit includes the first external terminal and the second external terminal. Is operated by receiving an operating voltage of a predetermined voltage level through the diode, and the diode is applied with a voltage opposite to the operating voltage between the first external terminal and the second external terminal. Protecting the first circuit from the reverse voltage by causing a current in a direction following the reverse voltage direction to flow as a forward current between the second external terminal and the first external terminal. When the voltage in the same direction as the operating voltage applied between the first external terminal and the second external terminal reaches a voltage to be protected, the transistor has the first external terminal and the second external terminal. To the same direction of voltage between the external terminals of A display device driving IC that protects the first circuit from an overvoltage in the same direction as the operating voltage between the first external terminal and the second external terminal by bypassing a positive current. And one of the N-type (or P-type) source and drain of the transistor is a first region, and the other of the source and the drain is a second region, and On the other hand, a P-type (or N-type) third region is provided on the opposite side of the second region adjacent to the first region, and includes the second region and the third region. A display device driving IC, characterized in that the diode and the transistor are integrally formed by making a portion also serve as the diode.