JPH05160348A - Semiconductor device and overvoltage protective device - Google Patents

Abstract

(57) [Summary] (Modified) [Object] The present invention provides a semiconductor device for overvoltage protection in which the protection capability against insulation of a semiconductor integrated circuit is improved, and an overvoltage protection device using this semiconductor device. To aim. A drain 31 and a source 32 are formed with a thick gate insulating film 2 formed on a semiconductor layer 1 of one conductivity type sandwiched therebetween, and a first gate 4 is formed on the thick gate insulating film 2 and isolated from the drain. One end 82 of the first conductor layer 8 formed and connected to the drain and formed on the insulating film forms the second gate 81 in the region corresponding to the thick gate insulating film 4 described above. A capacitor is formed between the first gate 4 and the first gate 4 in a region corresponding to the first gate 4, and the other end of the first conductor layer 8 has a pad 6 for signal input.
2 and the first gate 4 is grounded or connected to a positive potential via a resistor 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvements in a semiconductor device for an overvoltage protection device of a semiconductor integrated circuit and an overvoltage protection device using the semiconductor device. In particular, it is an object of the present invention to provide a semiconductor device for overvoltage protection that prevents an internal element from dielectric breakdown even if an overvoltage is applied to the semiconductor integrated circuit from the outside, and an overvoltage protection device using the semiconductor device. To improve.

[0002]

2. Description of the Related Art In recent years, semiconductor integrated circuits have become more and more miniaturized in response to the demand for higher integration, and it has become difficult to ensure sufficient insulation against external overvoltage surges. For this reason, how to protect the semiconductor integrated circuit from an external overvoltage surge has become a serious problem, and the following protection device has already been put into practical use as an overvoltage protection device for the semiconductor integrated circuit.

FIG. 4 is an equivalent circuit diagram of an overvoltage protection device according to a first example of the prior art. In FIG. 4, 11 is a P-channel MOSFET, the source and the gate of which are connected to the positive potential V _DD , and the drain of which is connected to the input connection pad 62 of the semiconductor integrated circuit 15 to be protected. Reference numeral 12 denotes an N-channel MOSFET, the source and the gate of which are grounded, the drain of which is connected to the drain of the P-channel MOSFET 11 and which is connected to the input connection pad 62 of the semiconductor integrated circuit 15 to be protected. Reference numeral 13 is a diode whose anode is connected to the input connection pad 62 and whose cathode is connected to the positive potential V _DD , and 14 is a diode whose anode is grounded and whose cathode is connected to the above input connection pad 62. is there. The P-channel MOSFET 11 and the diode 14 are turned on when a negative overvoltage surge enters the input connection pad 62 to suppress the potential rise of the input connection pad 62 and protect the semiconductor integrated circuit 15. And above N channel
The MOSFET 12 and the diode 13 are rendered conductive when a positive overvoltage surge enters the input connection pad 62 to suppress the potential rise of the input connection pad 62 and protect the semiconductor integrated circuit 15.

FIG. 5 is an equivalent circuit diagram of an overvoltage protection device according to a second example of the prior art. In FIG. 5, reference numeral 17 denotes a P-channel aluminum field transistor, the source of which is connected to the positive potential V _DD ,
The drain and gate are connected to the input connection pad 62 of the semiconductor integrated circuit 15 to be protected. Reference numeral 18 denotes an N-channel aluminum field transistor whose source is grounded and whose drain and gate are connected to the input connection pad 62 of the semiconductor integrated circuit 15 to be protected. 13
Reference numerals 14 and 14 are diodes similar to those in the first embodiment. In the case of the present embodiment as well as in the case of the first embodiment, the P-channel aluminum field transistor 17 and the diode 14 become conductive with respect to a negative overvoltage surge, and the above with respect to a positive overvoltage surge. The N-channel aluminum field transistor 18 and the diode 13 are electrically connected to each other to suppress the potential rise of the input connection pad 62 and protect the semiconductor integrated circuit 15.

[0005]

However, in the overvoltage protection device according to the first example of the prior art, the drain region directly connected to the input connection pad 62 and the polysilicon gate connected to the ground or the positive potential are provided. However, there is a drawback that an external overvoltage is applied to a portion adjacent to each other and the thin gate insulating film is destroyed.

Further, in the overvoltage protection device according to the second example of the prior art, since the gate insulating film is thick, the breakdown voltage is higher than that of the above-mentioned first example, but the on-speed is slow when the overvoltage is applied. The drawback is that protection is not possible in the initial stage of the overvoltage (the period until the transistor is turned on), and the impedance of the transistor when it is turned on is not sufficiently small, so that it is necessary to sufficiently suppress the potential rise of the input connection pad. There is a drawback to say.

An object of the present invention is to provide a semiconductor device for overvoltage protection which solves this drawback and has an improved protection capability against insulation of a semiconductor integrated circuit, and an overvoltage protection device using this semiconductor device. is there.

[0008]

The above object is achieved by the following semiconductor device and overvoltage protection device. In the semiconductor device, a thick gate insulating film (2) is formed on a semiconductor layer (1) of one conductivity type, and a drain (31) and a source (31) formed of regions of opposite conductivity type sandwiching the thick gate insulating film (2). 32) is formed, and a first gate (4) is formed on the thick gate insulating film (2) separated from the drain (31), and the gate (4) has a resistance (5). Is connected to the first connection pad (61) through the insulating film (7) leaving the drain contact window and the source contact window.
Is formed to connect to the drain (31) and cover the insulating film (7) in a region corresponding to the thick gate insulating film (2) and the gate (4). A conductor layer (8) is formed, and the first conductor layer (8) is formed.
One end of the first gate constitutes a second gate (81) in a region corresponding to only the thick gate insulating film (2), and the first gate in the region corresponding to only the first gate (4). One pole (82) of the capacitor whose other pole is the gate (4) of
The other end of the first conductor layer (8) is connected to a second connection pad (62) for signal input, and the source (32) and the third connection pad (63) are connected. ) And connect the second
The semiconductor device in which the conductor layer (9) is formed.

In the above configuration, the source (32)
Is separated from the thick gate insulating film (2) and is connected to the thick gate insulating film (2) to form a thin gate insulating film (21) on the semiconductor layer (1) of one conductivity type. Was
The first gate (4) is connected to one of the sources (32).
The effect is particularly remarkable when the region is extended to the edge.

Further, the overvoltage protection device has the above-mentioned structure, and the first connection pad (61) and the third connection pad (63).
And the above-mentioned first conductor layer (8) of the first semiconductor device (A) which is grounded, and the above-mentioned configuration, and the first connection pad (61) and the third connection pad ( 63) is connected to a positive potential and the first conductor layer (8) of the second semiconductor device (B) is a third conductor layer (C) for signal input / output. It is an overvoltage protection device that is commonly connected.

[0011]

In the semiconductor device of the overvoltage protection device according to the present invention, one end of the aluminum wiring connected to the second connection pad for signal input extends to the region corresponding to the first gate (polysilicon gate). A capacitor is formed between the first gate and the first gate, and the first gate is connected to the ground or a positive potential through a resistor. Therefore, an external overvoltage surge is applied to the second connection pad. , The potential of the first gate rises momentarily and the channel portion corresponding to the first gate first turns on. After a short delay, the channel portion corresponding to the second gate having the end portion of the aluminum wiring is turned on, and a current flows between the drain and the source. Therefore, the turn-on speed of the semiconductor device is relatively high. Further, since most of the channel corresponds to the first gate, the on-resistance is smaller than that of the aluminum field transistor, and it is possible to effectively suppress the potential rise of the second connection pad. Further, since the drain to which the overvoltage is applied and the first gate are separated from each other and the thick insulating film is interposed therebetween, the gate insulating film is not easily broken.

Therefore, using the above semiconductor device,
The overvoltage protection device configured by grounding the first gate and the source or connecting the source to a positive potential can improve the protection capability against insulation of the semiconductor integrated circuit.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A semiconductor device for an overvoltage protection device and an overvoltage protection device according to a second embodiment of the present invention will be described below with reference to the drawings.

FIG. 1A is a sectional view of a semiconductor device of a first embodiment (corresponding to claim 1), and FIG. 1B is an equivalent circuit diagram thereof. See FIG. 1. In the figure, 1 is a semiconductor layer of one conductivity type (for example, a P substrate)
Is. Reference numeral 2 is a thick gate insulating film formed on the semiconductor layer 1. Reference numerals 31 and 32 denote a drain and a source (for example, N type) formed with the thick gate insulating film 2 sandwiched therebetween.
Reference numeral 4 is a first gate formed on the thick gate insulating film 2 so as to be separated from the drain 31. The first gate 4 is connected to the first connection pad 61 via the resistor 5. Reference numeral 7 is an insulating film formed leaving the drain contact window and the source contact window. 8 is the above drain
A first conductor layer connected to 31 and formed to cover the insulating film 7 in a region corresponding to the thick gate insulating film 2 and the gate 4. Reference numeral 81 is a second gate formed in a region corresponding to only the thick gate insulating film 2 at one end of the first conductor layer 8.
Is one end of the above-mentioned first conductor layer 8 which constitutes one pole of the capacitor having the above-mentioned first gate 4 as the other pole in the region corresponding to only the above-mentioned first gate 4. The other end of the first conductor layer 8 is connected to the second connection pad 62 for signal input. Reference numeral 9 is a second conductor layer formed by connecting the source 32 and the third connection pad 63. Further, in FIG. 1B, 100 is a portion having an aluminum field transistor function of the semiconductor device according to the present invention, and 200 is a portion having a MOSFET function. D and S in FIG. 1 (b) indicate that they correspond to the drain and source of both parts 100 and 200 above.

Next, the operation of this embodiment will be described. When an extraneous overvoltage surge enters the second connection pad 62, this surge causes a capacitor to be formed between the first end 82 of the first conductor layer 8 and the first gate 4 and thus the first surge. Potential of the gate 4 of the
The channel portion corresponding to is turned on first. A little late,
The channel portion corresponding to the second gate 81 is turned on, and a current flows between the drain 31 and the source 32. Therefore,
The speed at which the semiconductor device is turned on is relatively high. Also, since most of the channel corresponds to the first gate, the on-resistance is relatively small, and the second connection pad for signal input is used.
The potential increase at 62 is effectively suppressed. In addition, the drain 31
And the first gate 4 are separated from each other, and the thick gate insulating film 2 is interposed, so that the gate insulating film 2 is not easily broken.

FIG. 2 is a sectional view of a semiconductor device according to a second embodiment (corresponding to claim 2). Referring to FIG. 2, the present embodiment is different from the first embodiment in that the source 32 is separated from the thick gate insulating film 2 and is connected to the thick insulating film 2 so that the one conductive type semiconductor layer 1 is formed. The thin gate insulating film 21 is formed on the first gate 4, and the first gate 4 extends only to the region corresponding to one end of the source 32. In addition,
The description of the other reference numerals is the same as that of the first embodiment, and will be omitted.

In this embodiment, the channel portion corresponding to the first gate turns on faster than the first embodiment, and therefore the semiconductor device turns on faster. The other operations are almost the same as those in the first embodiment.

FIG. 3 is an equivalent circuit diagram of an overvoltage protection device using the semiconductor device according to the first or second embodiment. See FIG. 3. In the figure, A and B are the semiconductor device of the first embodiment or the semiconductor device of the second embodiment.

The first connection pad 61 and the third connection pad of the semiconductor device A
Of the semiconductor device B is grounded, and the first connection pad 61 and the third connection pad 63 of the semiconductor device B are connected to a positive potential. In addition, the first conductor layer 8 of the semiconductor device A and the first conductor layer 8 of the semiconductor device B are connected to the third conductor layer C connected to the second connection pad 62 for signal input. Commonly connected.

Therefore, the semiconductor device A is turned on with respect to the positive overvoltage surge, and the semiconductor device B is turned on with respect to the negative overvoltage surge, and the semiconductor connected to the third conductor layer C is connected. Protects the integrated circuit (not shown) from overvoltage.

[0021]

As described above, in the semiconductor device for overvoltage protection according to the present invention, the drain and source of opposite conductivity type are formed with the thick gate insulating film formed in the semiconductor layer of one conductivity type interposed. , A first gate is formed on the thick insulating film separated from the drain, and the first gate is connected to a first connection pad via a resistor, and a drain contact window and a source contact window are formed. The insulating film is formed by leaving the thick gate insulating film and the first
A first conductor layer is formed to cover the insulating film in a region corresponding to the gate of the first conductor layer, and one end of the first conductor layer has a second gate in the region corresponding to the thick insulating film. And forming a capacitor between the first gate and the first gate in a region corresponding to the first gate.
The other end of the conductor layer is connected to the second connection pad for signal input, and the source and the third connection pad are connected to form the second conductor layer. In the overvoltage device, two sets of semiconductor devices having the above-described configuration are used, the first connection pad and the third connection pad of one semiconductor device are grounded, and the first connection pad of the other semiconductor device is Since the third connection pad is connected to a positive potential and the first conductor layers of both semiconductor devices are connected to the common third conductor layer, an overvoltage surge is introduced to the second connection pad. Then, the potential of the first gate instantaneously rises, the channel corresponding to the first gate is first turned on, and then the channel corresponding to the second gate is turned on, and the current between the drain and the source is increased. Flows. Therefore, the turn-on speed of the semiconductor device is high. Also, since most of the channel corresponds to the first gate, the on-resistance is relatively small, and the potential rise of the second connection pad for signal input can be suppressed. Further, since the drain and the first gate are isolated from each other and the thick gate insulating film is interposed, the gate insulating film is not easily broken.

Therefore, the present invention can provide an overvoltage protection semiconductor device having improved protection capability against insulation of a semiconductor integrated circuit and an overvoltage protection device using the semiconductor device.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a semiconductor device according to a first exemplary embodiment of the present invention.

FIG. 2 is a sectional view of a semiconductor device according to a second embodiment of the present invention.

FIG. 3 is an equivalent circuit diagram of an overvoltage protection device according to the present invention.

FIG. 4 is an equivalent circuit diagram of an overvoltage protection device according to a first example of the prior art.

FIG. 5 is an equivalent circuit diagram of an overvoltage protection device according to a second example of the prior art.

[Explanation of symbols]

Reference Signs List 1 1 conductive type semiconductor layer 2 thick gate insulating film 4 first gate 5 resistor 7 insulating film 8 first conductive layer 9 second conductive layer 11 P-channel MOSFET 12 N-channel MOSFET 13/14 diode 15 semiconductor Integrated circuit 17 P-channel aluminum field transistor 18 N-channel aluminum field transistor 21 Thin gate insulating film 31 Drain 32 Source 61 First connection pad 62 Second connection pad 63 Third connection pad 81 Second gate 82 Second One end of the conductor layer of 1 100 A part having an aluminum field transistor function 200 A part having a MOSFET function A A semiconductor device on the ground side B A semiconductor device on the positive potential side C Third conductor layer

Claims (3)

[Claims] 1. A gate insulating film (2) is formed on a semiconductor layer (1) of one conductivity type, and a drain (31) and a source (32) formed of regions of opposite conductivity type sandwiching the gate insulating film (2). ) Is formed, and a first gate (4) is formed on the gate insulating film (2) so as to be separated from the drain (31). An insulating film (7) is formed, which is connected to the connection pad (61) of No. 1 and leaves a drain contact window and a source contact window, and is connected to the drain (31) and the gate insulating film (2).
A first conductor layer (8) is formed to cover the insulating film (7) in a region corresponding to the gate (4) and one end of the first conductor layer (8) is The second gate (81) in the region corresponding to only the gate insulating film (2)
And a first pole (82) of a capacitor having the first gate (4) as the other pole in a region corresponding to only the first gate (4), and the first conductor layer ( The other end of 8) is connected to the second connection pad (62) for signal input, and connects the source (32) and the third connection pad (63) to the second conductor layer (9). ) Are formed in the semiconductor device. 2. The source (32) is separated from the gate insulating film (2), is connected to the gate insulating film (2), and is a thin gate insulating film on the one conductivity type semiconductor layer (1). The semiconductor device according to claim 1, wherein (21) is formed, and the first gate (4) extends to a region corresponding to one end of the source (32). 3. A first connection pad (61) and a third connection pad (63) having the structure according to claim 1 or claim 2.
And the first semiconductor device (A), which is grounded,
A conductive layer (8) and a structure according to claim 1 or 2, wherein the first connection pad (61) and the third connection pad (63) are connected to a positive potential. The second conductor layer (8) of the second semiconductor device (B) is commonly connected to the third conductor layer (C) for signal input / output. apparatus.