JPH11111727A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device which can prevent the breakage of a bipolar transistor having an emitter region on the main surface of a semiconductor substrate by suppressing the current which flows into the end section of the emitter region of the transistor, even when a large current flows to the transistor. SOLUTION: A PNP bipolar transistor 110 uses an N-type well 100 formed on the main surface of a P-type semiconductor substrate 1 as a base region and a P-type high-concentration region 101 formed on the main surface of the N-type well 100 as an emitter region. A plurality of trench grooves 102, having depths which are deeper than or nearly equal to the depth of the emitter region is formed in the emitter region and each small region in the emitter region divided or partitioned by the grooves 102 is connected electrically to another, except for the end sections of the P-type high-concentration region 101.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a semiconductor device.

[0002]

2. Description of the Related Art A conventional semiconductor device is shown in FIG. 6 (see Japanese Patent Application Laid-Open No. 55-91171).
There is. Hereinafter, the structure and operation of the conventional example will be described with reference to FIG. An N-type well 619 is formed on the main surface of the P-type semiconductor substrate 601, and a P-type high concentration region 650 and an N-type high concentration region 651 are provided on the N-type well 619 main surface. Then, one end of the P-type high-concentration region 650 is connected to the input terminal 608, and the other end is connected to a signal line 609 leading to an internal circuit. Further, the N-type well 619 has an N-type high concentration region 651.
Is connected to the well contact 622, and the P-type semiconductor substrate 601 is connected to the substrate contact 612. As a result, the input protection resistor 620 including the P-type high-concentration region 650 is connected between the input terminal 608 and the signal line 609. Further, a PNP bipolar transistor (hereinafter, transistor is abbreviated as Tr) 621 having a P-type high concentration region 650 as an emitter, an N-type well 619 as a base, and a P-type semiconductor substrate 601 as a collector is connected.

Next, the operation of this conventional example will be described. In a normal circuit operation, a signal is applied to an internal circuit through an input protection resistor 620. However, since this portion is not directly related to the operation of the semiconductor device, a detailed description is omitted. Next, when a positive overvoltage surge is applied to the input terminal 608, the emitter-base junction of the PNP bipolar Tr 621 functions as a pull-up diode, and the PNP bipolar Tr 621 turns on.
An excessive current caused by the surge is bypassed from the input terminal 608 to the well contact 622 and the P-type semiconductor substrate 601. Therefore, no excessive voltage due to the surge is applied to the internal circuit to which the signal line 609 is connected, and no excessive current due to the surge is injected. Therefore, destruction of the internal circuit due to the surge is prevented. When a negative overvoltage surge is applied to the signal line 608, the PNP bipolar Tr 621
By turning on the reverse Tr, the breakdown of the internal circuit due to the surge is similarly prevented.

[0004]

However, such a conventional semiconductor device has the following problems. Since the base current of PNP bipolar Tr 621 is injected from N-type high concentration region 651 on the main surface of N-type well 619, a voltage drop occurs inside the base. Therefore N
Current concentration effect that the forward bias of the emitter-base junction is higher at the end of the emitter region closer to the high-concentration region 651 (for details, see "Semiconductor Devices", page 123, Seijiro Furukawa, published by Corona Co.) . This effect becomes more pronounced as the Tr current increases. Therefore, the PNP bipolar Tr 621 is turned on by the application of the overvoltage surge, and when a large current due to the surge flows through the PNP bipolar Tr 621, the PNP bipolar Tr 621 has a P-type high concentration region 650 which is the emitter region of the PNP bipolar Tr 621 due to the emitter current concentration effect described above. At the end, a Tr
The current is concentrated, and as a result, the PNP bipolar Tr 621 is broken. The present invention has been made in view of such a conventional problem. In a bipolar Tr having an emitter region on a main surface of a semiconductor substrate, particularly, the emitter region has an input terminal or an output terminal of a semiconductor device, or a high potential terminal. Alternatively, in a bipolar Tr connected to one of the low potential terminals, the emitter region is divided or divided into small regions by a plurality of trenches, and these small regions are electrically connected. Even if a large current flows through the Tr, the Tr current flowing to the end of the emitter region is prevented from becoming excessive, and
There is an effect that the destruction of r can be prevented.

[0005]

In order to achieve the above object, according to the first aspect of the present invention, a well of a second conductivity type formed on a main surface of a semiconductor substrate of a first conductivity type is used as a base region, In a bipolar transistor having a first conductivity type high-concentration region formed on a surface as an emitter region, a plurality of trenches are formed in the emitter region, and the trenches are deeper than the emitter region or approximately the same. Each small region of the emitter region having a depth and excluding an end of the first conductivity type high-concentration region forming the emitter region among the emitter regions divided or separated by the trench groove Are electrically connected.

According to a second aspect of the present invention, in the semiconductor device according to the first aspect, the emitter region is connected to one of an input terminal or an output terminal of the semiconductor device, or a high potential terminal or a low potential terminal. Configuration.

According to a third aspect of the present invention, in the semiconductor device according to the second aspect of the present invention, the small region near the end of the emitter region is connected to the center of the emitter region via a resistance region formed on the main surface of the substrate. A portion connected to the small region, and the small region in the central portion of the emitter region is connected to the terminal.

A semiconductor device according to a fourth aspect of the present invention is the semiconductor device according to the second or third aspect, wherein a second portion is provided inside the well in contact with the bottom surface of the small region near the end of the emitter region and at a portion in contact with the bottom surface. A conductive type high concentration region was formed.

According to a fifth aspect of the present invention, in the semiconductor device according to any one of the second to fourth aspects, the small region in the central portion of the emitter region is connected to the terminal, and the small region in the central portion of the emitter region is connected to the small region. The emitter region is divided by the trench so that an electric path to the small region in the vicinity of the end of the emitter region is a polygonal line, and the path becomes longer as approaching the emitter end. ing.

[0010]

Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a cross-sectional structure of the first embodiment. First, the sectional structure will be described with reference to FIG. An N-type well 100 is formed on the main surface of the P-type semiconductor substrate 1, and a P-type high concentration region 101 and an N-type high concentration region 103 are provided on the N-type well 100 main surface. Then, the P-type high-concentration region 101 is divided into a plurality of small regions by a plurality of trenches 102, and the main surface of each of the small-regions of the P-type high-concentration region 101 is defined as A.
Ohmic connection is made to the 1 electrode 106. Al electrode 106
Is connected to the input terminal 104 and the signal line 10
5 is also connected. Here, the signal line 105 is connected to an internal circuit via a protection resistor (not shown). The N-type high-concentration region 103 has a predetermined voltage, for example, Vdd for supplying a high potential of the semiconductor device through the well contact 107.
Connected to terminal. The P-type semiconductor substrate 1 is connected to a Vss terminal that supplies a low potential to the semiconductor device.

Next, the circuit configuration will be described. Trench groove 1
02, each small region of the P-type high-concentration region 101 is an emitter, the N-type well 100 is a base, and the P-type semiconductor substrate 1 is
Are formed as a plurality of PNP bipolar Trs 110, and these PNP bipolar Trs 110 are
They are connected in parallel with each other. Here, each PNP bipolar Tr11 is provided in each small region inside the P-type high concentration region 101.
A zero emitter resistance 111 is formed, and a base resistance 112 of the PNP bipolar Tr 110 is formed inside the N-type well 100.

Next, the operation will be described. During normal circuit operation, a signal applied to the input terminal 104 is transmitted to the internal circuit via the signal line 105. Since this part is not directly related to the present invention, a detailed description is omitted.

When a positive overvoltage surge is applied to the input terminal 104, the PNP bipolar Tr 110 is turned on, and an excessive current caused by the surge is bypassed from the input terminal 104 to the P-type semiconductor substrate 1, thereby causing an excessive circuit in the internal circuit. Prevents voltage application and excessive current injection. Therefore, the destruction of the internal circuit due to the surge is prevented.

Here, the reason why the present embodiment can prevent the destruction of the PNP bipolar transistor due to the application of a surge will be described. When a positive overvoltage surge is applied to the input terminal, the surge current flows through the PNP bipolar Tr 110 formed inside the N-type well 100 and connected in parallel with each other. At this time, due to the emitter current concentration effect described above, the bipolar Tr current increases in the portion of the PNP bipolar Tr 110 closer to the N-type high-concentration region 103 serving as the base contact. In this case, since the trench 102 divides the N-type high-concentration region 101, which is the emitter region, into a plurality of small regions, the PNP bipolar Tr 110 through which a large current flows becomes smaller at the emitter-base junction due to the voltage drop at the emitter resistor 111. , The increase in the forward bias is suppressed, and the increase in the Tr current is suppressed. The emitter-base junction of PNP bipolar Tr 110 is only at the bottom of N-type high concentration region 101. Therefore, a large Tr current flows without concentrating on a part of the emitter-base junction, and the PNP bipolar Tr 110 enters a high-level injection state. As a result, an increase in the Tr current is further suppressed. As described above, the surge current causes a part of the bipolar Tr, that is, the pn formed by the P-type high concentration region 101 and the N-type well 100.
Since it is difficult to concentrate on a part of the junction, breakdown of the PNP bipolar Tr 110 and the semiconductor device is less likely to occur.

In addition, compared to the case where only the end of the P-type high-concentration region 101 is simply surrounded by the trench groove 102, the present embodiment has a higher breakdown strength due to surge for the following reason. Even if the trench 102 is formed only at the end of the P-type high-concentration region 101, the above effect does not occur because the emitter resistance 111 hardly occurs. In addition, although the Tr current flows only through the bottom surface of the P-type high-concentration region 101, the current density near the end of the P-type high-concentration region 101 near the base contact increases due to the above-described emitter current concentration effect. Combined with the absence of the above effect, the Tr current concentrates on this portion. Therefore, there is a high possibility that the surge will destroy the Tr.

FIG. 2 shows the structure of the second embodiment. In the second embodiment, in the structure of the first embodiment, the small region divided by the trench 102 near the end of the P-type high-concentration region 101 is replaced by a resistor formed on the main surface of the small region. A region 200, for example, a P ⁺ -type polysilicon region is connected to a small region at the center of the P-type high concentration region 101. The small area at the center of the P-type high-concentration area 101 is connected to the input terminal 104. The second embodiment is different from the first embodiment in the above points, and the other structure is the same as that of the first embodiment.

Next, the operation will be described. In the second embodiment, the resistance component of the resistance region 200 is the emitter resistance 11 of the PNP bipolar Tr 110 described in the first embodiment.
1 in series. Therefore, due to the effect of the first embodiment, the P-type near the end of the P-type high-concentration region 101
Destruction of the NP bipolar Tr110 is less likely to occur. As a result, the destruction of the semiconductor device due to the application of the surge is further prevented.

FIG. 3 shows the structure of the third embodiment. In the third embodiment, in the structure of the first embodiment, inside the N-type well 100 contacting the bottom surface of the small region divided by the trench 102 near the end of the P-type high-concentration region 101 and the small region N-type high concentration region 3
00 is formed. The third embodiment is different from the first embodiment in the above points, and the other configuration is the same as the first embodiment.

Next, the operation will be described. In the third embodiment, the PNP bipolar T near the end of the P-type high concentration region 101
Since the base concentration of r110 increases, RFE decreases.
Therefore, the PNP bipolar Tr110
Is turned on, the PNP bipolar Tr11 near the end of the P-type high concentration region 101 is different from that of the first embodiment.
0 current bias capability is reduced. Therefore, excessive current concentration on the PNP bipolar Tr 110 near this end is further suppressed, and a Tr current due to a surge flows through each PNP bipolar Tr 110 in a more averaged manner. As a result, the destruction of the semiconductor device due to the surge is further prevented.

FIG. 4 shows the structure of the fourth embodiment. In the fourth embodiment, in the structure of the first embodiment, the P-type high-concentration region 401 is not divided by the trench, but the P-type high-concentration region 401 is formed by the trench 402. The electric path from the central portion to the vicinity of the end of the P-type high-concentration region 401 is a polygonal line, and the path is divided such that the longer the closer to the end of the P-type high-concentration region 401, the longer the path. Only the central portion of the high concentration region 401 is connected to the input terminal 104. Embodiment 4
The above points are different from the first embodiment, and other structures are the same as the first embodiment.

Next, the operation will be described. In the fourth embodiment, in the PNP bipolar Tr 110 near the end of the P-type high-concentration region 401, the resistance inside the P-type high-concentration region 401 is connected in series, and the value of the resistor connected in series is It becomes larger as it approaches the end of the P-type high concentration region 401. Further, the value of this resistance can be designed to an arbitrary value by adjusting the way of dividing the P-type high-concentration region 401 by the trench 402. Therefore, due to the effect described in the first embodiment, excessive current concentration on PNP bipolar Tr 110 near the end of P-type high concentration region 401 is further suppressed, and surge current flowing through PNP bipolar Tr 110 is further averaged. . As a result, the destruction of the semiconductor device due to the surge is further prevented.

Further, in Embodiment 4, Embodiment 2
Since there is no need to form a new region such as the resistance region 200 in FIG. 1 and the N-type high-concentration region 300 in the third embodiment, an increase in manufacturing cost can be suppressed.

In each of the embodiments described above, PN
The P bipolar transistor has been described as an example. NPN bipolar T
Even in the case of r, the operation of each embodiment is equally generated. In this case, in each embodiment, the N-type high-concentration region and the P-type high-concentration region, and the Vdd terminal for supplying a high potential and the Vss terminal for supplying a low potential may be exchanged. The trench is P
The same effect can be obtained even if it is not necessarily formed deeper than the high-concentration region and is set to the same depth. For example, as shown in FIG. 5, in the first embodiment, even if the trench 500 is formed to be approximately the same as or slightly shallower than the P-type high-concentration region 101,
Almost the same operation as in the first embodiment occurs. Embodiment 2,
The same applies to 3 and 4.

[0024]

As described above, in the semiconductor device of the present invention, the emitter region is divided or divided into small regions by the plurality of trenches, and these small regions are electrically connected. Configuration, the bipolar Tr
Tr flows to the end of the emitter region even if a large current
It is possible to prevent the current from becoming excessive, prevent the bipolar transistor from being damaged, and prevent the semiconductor device from being damaged by the application of a surge.

[Brief description of the drawings]

FIG. 1 is a diagram showing a cross-sectional structure of a first embodiment.

FIG. 2 is a diagram illustrating a cross-sectional structure according to a second embodiment;

FIG. 3 is a diagram illustrating a cross-sectional structure according to a third embodiment;

FIG. 4 is a diagram showing a cross-sectional structure according to a fourth embodiment.

FIG. 5 is a diagram illustrating a second cross-sectional structure according to the first embodiment;

FIG. 6 is a diagram showing a cross-sectional structure of a conventional example.

[Explanation of symbols]

 Reference Signs List 1 P-type semiconductor substrate 100 N-type well 101 P-type high concentration region 102 Trench groove 103 N-type high concentration region 104 Input terminal 105 Signal line 106 Al electrode 107 Well contact 110 PNP bipolar Tr 111 Emitter resistance 112 Base resistance 200 Resistance region 300 N-type high-concentration region 401 P-type high-concentration region 402 Trench groove 500 Trench groove 601 P-type semiconductor substrate 608 Input terminal 609 Signal line 612 Substrate contact 619 N-type well 620 Input protection resistor 621 PNP bipolar Tr 622 Well contact 650 P-type high Concentration area 651 N-type high concentration area

Claims (5)

[Claims] 1. A bipolar having a second conductivity type well formed on a main surface of a semiconductor substrate of a first conductivity type as a base region and a high concentration region of the first conductivity type formed on the main surface of the well as an emitter region. In the transistor, a plurality of trench grooves are formed in the emitter region portion, the trench grooves are deeper than or equal to the emitter region, and the emitter is divided or divided by the trench grooves. A semiconductor device, wherein each of the small regions of the emitter region, except for the end of the high-concentration region of the first conductivity type forming the emitter region, is electrically connected. 2. The semiconductor device according to claim 1, wherein the emitter region is connected to an input terminal or an output terminal of the semiconductor device, or one of a high potential terminal and a low potential terminal. Semiconductor device. 3. The semiconductor device according to claim 2, wherein the small region near an end of the emitter region is connected to the small region at a central portion of the emitter region via a resistance region formed on the main surface of the substrate. A semiconductor device, wherein the small region at the center of the emitter region is connected to the terminal. 4. The semiconductor device according to claim 2, wherein a high-concentration region of the second conductivity type is provided inside the well in contact with the bottom surface of the small region near the end of the emitter region and in a portion in contact with the bottom surface. A semiconductor device characterized by being formed. 5. The semiconductor device according to claim 2, wherein the small region in the central portion of the emitter region is connected to the terminal, and the small region in the central portion of the emitter region is connected to an end of the emitter region. An electric path leading to the small region in the vicinity is a polygonal line, and the emitter region is separated by the trench groove such that the path becomes longer as approaching the emitter end. Semiconductor device.