protective element

Abstract

This protection element includes first to fourth switching elements, and a back gate guard ring surrounding the first to fourth switching elements. The back gate guard ring includes a first section, a second section, and a third section. The first section is disposed adjacent to a side of the first switching element opposite to the second switching element. The second section is disposed between the second switching element and the third switching element. The third section is disposed adjacent to a side of the fourth switching element opposite to the third switching element. A source of the first switching element is disposed closer to the first section than a gate of the first switching element. A source of the second switching element is disposed closer to the second section than a gate of the second switching element. A source of the third switching element is disposed closer to the second section than a gate of the third switching element.

Description

[Technical Field]

[0001] This disclosure relates to a protective element. [Background technology]

[0002] Conventionally, protective elements composed of n-type MOSFETs (metal-oxide-semiconductor field-effect transistors) have been known as protective elements to protect against electrostatic discharge (ESD) (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2002-324842 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Incidentally, with the miniaturization of electronic components, there is a demand to miniaturize protective elements. However, when protective elements are miniaturized, their hold voltage decreases, and there is a risk that the protective element may activate at the operating voltage of the circuit it protects. [Means for solving the problem]

[0005] A protective element that solves the above problem comprises a plurality of switching elements made of n-type MOSFETs, arranged in a line in one direction in parallel with each other, and a back gate guard ring surrounding the plurality of switching elements, wherein the plurality of switching elements include a first switching element, a second switching element, a third switching element, and a fourth switching element arranged in order, and the back gate guard ring comprises a first portion located next to the first switching element on the opposite side from the second switching element, a second portion located between the second switching element and the third switching element, and a third portion located next to the fourth switching element on the opposite side from the third switching element, wherein the source of the first switching element is located closer to the first portion than to the gate of the first switching element, the source of the second switching element is located closer to the second portion than to the gate of the second switching element, and the source of the third switching element is located closer to the second portion than to the gate of the third switching element.

[0006] With this configuration, the back gate guard ring is positioned near the sources of the first to third switching elements, which increases the hold voltage of the protection element and suppresses malfunctions of the protection element. Furthermore, since the second portion of the back gate guard ring is positioned between the source of the second switching element and the source of the third switching element, the area of ​​the protection element can be reduced compared to a configuration in which the first to fourth switching elements are individually surrounded by back gate guard rings. Therefore, malfunctions of the protection element can be suppressed and the protection element can be miniaturized. [Effects of the Invention]

[0007] The above-described protective element can suppress malfunctions of the protective element and also enable miniaturization of the protective element. [Brief explanation of the drawing]

[0008] [Figure 1]Circuit diagram showing an embodiment of the protection element. [Figure 2] Plan view showing a part of the protection element. [Figure 3] Schematic cross-sectional view of the protection element in FIG. 2. [Figure 4] Characteristic diagram showing the V-I characteristics of the protection element. [Figure 5] Plan view showing a part of the protection element of the comparative example. [Figure 6] Schematic cross-sectional view of the protection element in FIG. 5. [Figure 7] Plan view showing a part of the protection element of another comparative example. [Figure 8] Table showing the area and hold voltage of the protection element of the present embodiment and the protection element of the comparative example. [Figure 9] Plan view showing a part of the protection element of the modification example. [Figure 10] Plan view showing a part of the protection element of the modification example.

Mode for Carrying Out the Invention

[0009] Hereinafter, an embodiment of the protection element will be described with reference to the drawings. The embodiments shown below illustrate configurations and methods for embodying the technical idea, and do not limit the materials, structures, arrangements, dimensions, etc. of each component to those described below. The description "at least one of A and B" in this specification should be understood to mean "only A, or only B, or both A and B".

[0010] Referring to FIGS. 1 to 3, an embodiment of the protection element 10 will be described. As shown in Figure 1, the protection element 10 is a protection element that protects, for example, a pair of switching elements 201 and 202 of the inverter device 200 from ESD. Switching element 201 is, for example, a high-side switching element connected to the drive power supply, and switching element 202 is a low-side switching element. Examples of switching elements 201 and 202 include transistors such as MOSFETs and IGBTs. In the following description, the case in which MOSFETs are used for switching elements 201 and 202 will be described. In this embodiment, a p-type MOSFET is used for switching element 201, and an n-type MOSFET is used for switching element 202.

[0011] The source of switching element 201 is connected to the first wire L1, and its drain is connected to the drain of switching element 202. The source of switching element 202 is connected to the second wire L2. In other words, switching elements 201 and 202 are connected in series between the first wire L1 and the second wire L2. The gates of each switching element 201 and 202 are connected to a gate driver (not shown). The first wire L1 is connected to the power supply terminal VDD, which is connected to the drive power supply, and the second wire L2 is connected to the ground terminal GND.

[0012] The protection element 10 is provided between the power supply terminal VDD and the ground terminal GND and the pair of switching elements 201 and 202, and is an element that directs the current that would otherwise flow toward the pair of switching elements 201 and 202 due to static electricity to the pair of switching elements 201 and 202 instead.

[0013] The protection element 10 comprises a plurality of switching elements 20. Each switching element 20 is composed of an n-type MOSFET. The plurality of switching elements 20 are connected in parallel to each other. In one example, 10 to 20 switching elements 20 are connected in parallel. In this embodiment, 12 switching elements 20 are connected in parallel. The drain 21 of each switching element 20 is connected to the first wire L1, the source 22 is connected to the second wire L2, and the gate 23 is connected to the source 22. In addition, the back gate 24 of each switching element 20 is connected to the source 22 of each switching element 20. Since the source 22 of each switching element 20 is connected to the second wire L2, each back gate 24 is at ground potential.

[0014] The protection element 10 may be provided as a separate package from the pair of switching elements 201 and 202, or as an integrated package with the pair of switching elements 201 and 202. In this embodiment, the protection element 10 is provided as a separate package from the pair of switching elements 201 and 202, that is, as a package composed of multiple switching elements 20.

[0015] Figure 2 shows an example of the arrangement of multiple switching elements 20. Figure 2 describes the arrangement of four switching elements 20. The arrangement of the remaining eight switching elements 20 is the same as in Figure 2, so its description is omitted. For convenience, Figure 2 omits the switching elements 20 other than the four.

[0016] For convenience, in the following explanation, the four switching elements 20 will be referred to as the first switching element 20A, the second switching element 20B, the third switching element 20C, and the fourth switching element 20D. Also, in Figure 2, for ease of understanding, the drain 21 is labeled "D", the source 22 is labeled "S", the gate 23 is labeled "G", and the back gate 24 is labeled "BG". For convenience, the back gate 24 is also labeled with dot hatching.

[0017] As shown in Figure 2, each switching element 20A to 20D is formed on the semiconductor substrate 30. In other words, Figure 2 is a plan view of the semiconductor substrate 30 as seen from its thickness direction. An example of the semiconductor substrate 30 is a Si (silicon) substrate. Each switching element 20A to 20D is arranged in one direction. In the following explanation, the direction in which each switching element 20A to 20D is arranged will be referred to as the x-direction, the thickness direction of the semiconductor substrate 30 will be referred to as the z-direction, and the direction perpendicular to both the x-direction and the z-direction will be referred to as the y-direction. Also, "plan view" refers to the view from the z-direction.

[0018] As shown in Figure 2, each switching element 20A to 20D is arranged so that they are aligned in the y-direction and spaced apart in the x-direction. In this embodiment, in the x-direction, the first switching element 20A, the second switching element 20B, the third switching element 20C, and the fourth switching element 20D are arranged in this order. That is, in the x-direction, the second switching element 20B and the third switching element 20C are positioned between the first switching element 20A and the fourth switching element 20D. The second switching element 20B is positioned closer to the first switching element 20A than to the third switching element 20C.

[0019] The drains 21, sources 22, and gates 23 of each switching element 20A to 20D are arranged in the x-direction. In other words, the arrangement direction of the drains 21, sources 22, and gates 23 of each switching element 20A to 20D is the same as the arrangement direction of each switching element 20A to 20D.

[0020] In this embodiment, the first switching element 20A has its source 22, gate 23, and drain 21 arranged in that order, and the second switching element 20B has its drain 21, gate 23, and source 22 arranged in that order. In other words, the drain 21 of the first switching element 20A and the drain 21 of the second switching element 20B are arranged to be adjacent in the x-direction. Furthermore, the source 22 of the first switching element 20A and the source 22 of the second switching element 20B are arranged to be as far apart from each other as possible.

[0021] The arrangement of the drain 21, source 22, and gate 23 of the third switching element 20C and the fourth switching element 20D is the same as that of the first switching element 20A and the second switching element 20B. That is, in the third switching element 20C, the source 22, gate 23, and drain 21 are arranged in that order, and in the fourth switching element 20D, the drain 21, gate 23, and source 22 are arranged in that order. For this reason, the source 22 of the third switching element 20C and the source 22 of the second switching element 20B are arranged to be adjacent in the x-direction.

[0022] The drains 21, sources 22, and gates 23 of each switching element 20A to 20D are aligned in the x-direction while being aligned with each other in the y-direction. In a plan view, the drain 21, source 22, and gate 23 of each switching element 20A to 20D are each strip-shaped, extending in the y-direction. The length of the drain 21 in the y-direction is equal to the length of the source 22 in the y-direction. The length of the gate 23 in the y-direction is longer than the lengths of the drain 21 and source 22 in the y-direction. In a plan view, both ends of the gate 23 in the y-direction protrude in the y-direction relative to the drain 21 and source 22.

[0023] As shown in Figure 2, the protective element 10 includes a back gate guard ring 25 that surrounds a plurality of switching elements 20. The back gate guard ring 25 shown in Figure 2 surrounds each switching element 20A to 20D and is composed of the back gates 24 of each switching element 20A to 20D. In other words, the back gate guard ring 25 is configured as a common back gate 24 for each switching element 20A to 20D.

[0024] The back gate guard ring 25 comprises a first portion 25A located next to the first switching element 20A on the opposite side from the second switching element 20B, a second portion 25B located between the second switching element 20B and the third switching element 20C, and a third portion 25C located on the opposite side of the fourth switching element 20D from the third switching element 20C. In plan view, the shape of the first to third portions 25A to 25C is a band extending in the y direction.

[0025] In a plan view, the source 22 of the first switching element 20A is located closer to the first portion 25A than the gate 23 of the first switching element 20A. The drain 21 of the first switching element 20A is located closer to the second portion 25B than the gate 23 of the first switching element 20A. The drain 21 of the second switching element 20B is located closer to the first portion 25A than the gate 23 of the second switching element 20B. The source 22 of the second switching element 20B is located closer to the second portion 25B than the gate 23 of the second switching element 20B. The source 22 of the third switching element 20C is located closer to the second portion 25B than the gate 23 of the third switching element 20C. The drain 21 of the third switching element 20C is located closer to the third portion 25C than the gate 23 of the third switching element 20C. The drain 21 of the fourth switching element 20D is located closer to the second portion 25B than the gate 23 of the fourth switching element 20D. The source 22 of the fourth switching element 20D is located closer to the third portion 25C than the gate 23 of the fourth switching element 20D.

[0026] Thus, in the first switching element 20A, the source 22, gate 23, and drain 21 are arranged in this order from the first part 25A to the second part 25B in the x-direction. In the second switching element 20B, the drain 21, gate 23, and source 22 are arranged in this order from the first part 25A to the second part 25B in the x-direction. In the third switching element 20C, the source 22, gate 23, and drain 21 are arranged in this order from the second part 25B to the third part 25C in the x-direction. In the fourth switching element 20D, the drain 21, gate 23, and source 22 are arranged in this order from the second part 25B to the third part 25C in the x-direction.

[0027] As shown in Figure 2, the first portion 25A is positioned spaced apart from the source 22 of the first switching element 20A in the x-direction. The second portion 25B is positioned spaced apart from both the source 22 of the second switching element 20B and the source 22 of the third switching element 20C in the x-direction. The third portion 25C is positioned spaced apart from the source 22 of the fourth switching element 20D in the x-direction.

[0028] Furthermore, the back gate guard ring 25 includes a pair of fourth parts 25D that connect the y-direction ends of the first to third parts 25A to 25C. In plan view, the shape of the pair of fourth parts 25D is a strip extending in the x-direction. The pair of fourth parts 25D are spaced apart from each switching element 20A to 20D in the y-direction.

[0029] The first switching element 20A and the second switching element 20B are surrounded by the first part 25A, the second part 25B, and a pair of fourth parts 25D. The third switching element 20C and the fourth switching element 20D are surrounded by the second part 25B, the third part 25C, and a pair of fourth parts 25D.

[0030] As shown in Figure 2, in this embodiment, in a plan view, the first to third parts 25A to 25C are each formed in the shape of a single strip extending in the y direction. In other words, in a plan view, the first part 25A is formed in the shape of a single strip extending in a direction perpendicular to the arrangement direction of the multiple switching elements 20. The second part 25B is formed in the shape of a single strip extending in a direction perpendicular to the arrangement direction of the multiple switching elements 20. The third part 25C is formed in the shape of a single strip extending in a direction perpendicular to the arrangement direction of the multiple switching elements 20. Here, in a plan view, if the angle between the direction in which the first part 25A extends and the arrangement direction of the multiple switching elements 20 is, for example, 85° or more and 95° or less, then it can be said that it extends in a direction perpendicular to the arrangement direction of the multiple switching elements 20. In a plan view, if the angle between the direction in which the second part 25B extends and the arrangement direction of the multiple switching elements 20 is, for example, 85° or more and 95° or less, then it can be said that it extends in a direction perpendicular to the arrangement direction of the multiple switching elements 20. In a plan view, if the angle between the direction in which the third part 25C extends and the arrangement direction of the multiple switching elements 20 is, for example, 85° or more and 95° or less, then it can be said that it extends in a direction perpendicular to the arrangement direction of the multiple switching elements 20. The arrangement direction of the multiple switching elements 20 can be defined, for example, by a line segment connecting the centers in the y direction of the gates 23 of each switching element 20.

[0031] Since the second portion 25B positioned between the second switching element 20B and the third switching element 20C is formed as a single unit, the second portion 25B becomes a common back gate guard ring 25 for both the source 22 of the second switching element 20B and the source 22 of the third switching element 20C.

[0032] The positional relationship between the back gate guard ring 25 and each switching element 20A to 20D will be explained. In a plan view, the sources 22 of each switching element 20A to 20D are parallel to the first to third parts 25A to 25C. That is, the distance in the x-direction between the source 22 of the first switching element 20A and the first part 25A is constant in the y-direction, the distance in the x-direction between the source 22 of the second switching element 20B and the second part 25B is constant in the y-direction, the distance in the x-direction between the source 22 of the third switching element 20C and the second part 25B is constant in the y-direction, and the distance in the x-direction between the source 22 of the fourth switching element 20D and the third part 25C is constant in the y-direction.

[0033] Because the second portion 25B is positioned between the second switching element 20B and the third switching element 20C, the distance DS2 between the second switching element 20B and the third switching element 20C is greater than the distance DS1 between the first switching element 20A and the second switching element 20B. Furthermore, the distance DS2 is greater than the distance DS3 between the third switching element 20C and the fourth switching element 20D.

[0034] The distance D1 between the source 22 of the first switching element 20A and the first part 25A is equal to the distance D2 between the source 22 of the second switching element 20B and the second part 25B. Here, if the difference between distance D1 and distance D2 is, for example, within 10% of distance D1, then distances D1 and D2 can be said to be equal.

[0035] The distance D3 between the source 22 of the third switching element 20C and the second part 25B is equal to the distance D2 between the source 22 of the second switching element 20B and the second part 25B. Here, if the difference between distance D3 and distance D2 is, for example, within 10% of distance D3, then distances D3 and D2 can be said to be equal.

[0036] The distance D4 between the source 22 of the fourth switching element 20D and the third part 25C is equal to the distance D2 between the source 22 of the second switching element 20B and the second part 25B. In other words, distances D1 to D4 are equal to each other. Here, if the difference between distance D4 and distance D2 is, for example, within 10% of distance D4, then we can say that distances D4 and D2 are equal. In other words, distances D1, D2, D3, and D4 are equal to each other.

[0037] Note that while we considered distances D1, D3, and D4 to be equal because they are equal to distance D2, this is not the only way; any distance other than D2 may be used as the reference. For example, distances D1 to D4 may be considered equal because they are equal to distance D1. Also, if the maximum deviation among distances D1 to D4 is within, for example, 10% of distance D1, then distances D1 to D4 may be considered equal. Here, we used distance D1 as the reference, but this is not the only way; any of distances D2 to D4 may be used.

[0038] In this embodiment, distances D1 to D4 are equal to the distance between the drain 21 of the first switching element 20A and the drain 21 of the second switching element 20B, i.e., the distance DS1 between the first switching element 20A and the second switching element 20B. Also, distances D1 to D4 are equal to the distance between the drain 21 of the third switching element 20C and the drain 21 of the fourth switching element 20D, i.e., the distance DS3 between the third switching element 20C and the fourth switching element 20D. Note that the relationship between distances D1 to D4 and distances DS1 and DS3 can be arbitrarily changed. In one example, distances DS1 and DS3 may be smaller than distances D1 to D4.

[0039] Figure 3 shows cross-sectional views of each switching element 20A to 20D. As shown in Figure 3, the semiconductor substrate 30 is p - This is a Si substrate having a mold region 34. -The type region 34 is formed on the semiconductor substrate 30, for example, as a well region. On the surface 31 of the semiconductor substrate 30, the drains 21 and sources 22 of each switching element 20A to 20D and the back gate guard ring 25 are formed. The drains 21 and sources 22 are n + It is formed by a well region of the type. The back gate guard ring 25 is p + It is formed by the well region of the type.

[0040] Furthermore, gates 23 for each switching element 20A to 20D are formed on the surface 31 of the semiconductor substrate 30 via an oxide film 32. An example of an oxide film 32 is silicon oxide (SiO2). In other words, multiple oxide films 32 are formed on the surface 31 of the semiconductor substrate 30. The multiple oxide films 32 are arranged spaced apart from each other in the x-direction. Each oxide film 32 is formed between the drain 21 and the source 22. A gate 23 is formed on each oxide film 32.

[0041] Element isolation zones 33 are formed between the source 22 of the first switching element 20A and the first portion 25A of the back gate guard ring 25, between the drain 21 of the first switching element 20A and the drain 21 of the second switching element 20B, between the source 22 of the second switching element 20B and the second portion 25B, between the source 22 of the third switching element 20C and the second portion 25B, between the drain 21 of the third switching element 20C and the drain 21 of the fourth switching element 20D, and between the source 22 of the fourth switching element 20D and the third portion 25C. The element isolation zones 33 are, for example, STI or LOCOS.

[0042] As shown in Figure 3, the drain 21(n + ) and source 22(n + ) and the p of the semiconductor substrate 30 -The first parasitic transistor 26A is composed of the p-type region 34. The base of the first parasitic transistor 26A is connected to the first portion 25A of the back gate guard ring 25. The resistance RA between the base of the first parasitic transistor 26A and the first portion 25A is the resistance component of the p - -type region 34.

[0043] The drain 21 (n + ) and the source 22 (n + ) of the second switching element 20B, and the p - -type region 34 form the second parasitic transistor 26B. The drain 21 (n + ) and the source 22 (n + ) of the third switching element 20C, and the p - -type region 34 form the third parasitic transistor 26C. The bases of the respective parasitic transistors 26B and 26C are connected to the second portion 25B of the back gate guard ring 25. The resistance RB between the base of the second parasitic transistor 26B and the second portion 25B and the resistance RC between the base of the third parasitic transistor 26C and the second portion 25B are each the resistance components of the p - -type region 34.

[0044] The drain 21 (n + ) and the source 22 (n + ) of the fourth switching element 20D, and the p - -type region 34 form the fourth parasitic transistor 26D. The base of the fourth parasitic transistor 26D is connected to the third portion 25C of the back gate guard ring 25. The resistance RD between the base of the fourth parasitic transistor 26D and the third portion 25C is the resistance component of the p - -type region 34.

[0045] The solid-line graph in FIG. 4 is a characteristic diagram showing the I-V characteristics of the protection element 10. In FIG. 4, the dot-hatching region indicating the range from the voltage of 0 V to VS indicates the operating region of each switching element 201 and 202 (see FIG. 1). The dot-hatching region indicating that the voltage is equal to or higher than the voltage VDL indicates the region where each switching element 201 and 202 fails.

[0046] As shown in Figure 4, when the voltage V between wires L1 and L2 (see Figure 1) rises, a leakage current flows through the back gate guard ring 25 (see Figure 3), causing the potential of the back gate guard ring 25 to rise. When the voltage V reaches a predetermined voltage VT, each parasitic transistor 26A to 26D (see Figure 3) conducts. When each parasitic transistor 26A to 26D conducts, it snaps back and the voltage V drops to the hold voltage VH, after which a current corresponding to the voltage V can flow to the protection element 10.

[0047] (action) The operation of the protective element 10 in this embodiment will be explained with reference to Figures 4 to 8. In Figure 8, the protective element of the comparative example shown in Figures 5 and 6 is referred to as Comparative Example 1, and the protective element of the comparative example shown in Figure 7 is referred to as Comparative Example 2.

[0048] The voltage V between wires L1 and L2 fluctuates due to ESD. The protection element 10 protects the switching elements 201 and 202 from this fluctuating voltage V. More specifically, the protection element 10 must operate so that the voltage V is below a first voltage value VDL, which is the lower limit of the voltage at which the switching elements 201 and 202 are destroyed. Furthermore, the protection element 10 must operate at a voltage higher than a second voltage value VDM, which is higher than the upper limit of the voltage range in which the switching elements 201 and 202 operate, so as not to operate within that voltage range. In other words, the protection element 10 must operate in a voltage range higher than the second voltage value VDM and lower than the first voltage value VDL. The second voltage value VDM is also called the absolute maximum voltage.

[0049] By the way, the demand for space saving necessitates miniaturization of the protection element 10 itself. However, if the protection element 10 is miniaturized, the hold voltage VH may decrease and fall below the second voltage value VDM.

[0050] Therefore, it is necessary to increase the hold voltage VH. In order to increase the hold voltage VH, the p between the source 22 and the back gate 24 -It is necessary to reduce the resistance value of the resistive component in the type region 34. This resistance value is thought to be proportional to the distance between the source 22 and the back gate 24. In other words, as shown in Figure 5, when the back gate guard ring 25X is formed to surround each switching element 20A to 20D together, the distance DX1 between the source 22 of the second switching element 20B and the first end 25XA of the back gate guard ring 25X, and the distance DX2 between the source 22 of the third switching element 20C and the second end 25XB of the back gate guard ring 25X become larger. As shown in Figure 6, the distance between the source 22 of the second switching element 20B and the first end 25XA of the back gate guard ring 25X is... - The resistor RX1 in region 34 is the p between the base of the second parasitic transistor 26B and the base of the first parasitic transistor 26A. - The resistance component of region 34 and the p between the first parasitic transistor 26A and the first end 25XA of the back gate guard ring 25X - This is the sum of the resistance component of type region 34. Also, the p between the source 22 of the third switching element 20C and the second end 25XB of the back gate guard ring 25X - The resistor RX2 in region 34 is the p between the base of the third parasitic transistor 26C and the base of the fourth parasitic transistor 26D. - The resistive component of region 34 and the p between the base of the fourth parasitic transistor 26D and the second end 25XB of the back gate guard ring 25X - This is the sum of the resistance components in type region 34. As a result, the resistances RX1 and RX2 each increase, and the hold voltage VH decreases, as shown in Figure 8.

[0051] Therefore, one example of a method to increase the hold voltage VH is to increase the number of back gate guard rings. For example, as shown in Figure 7, it is conceivable to form back gate guard rings 25X so as to individually surround each switching element 20A to 20D. In this case, the distance DXA between the first end 25XA of the back gate guard ring 25X and the source 22 of the first switching element 20A, the distance DXB between the first intermediate part 25XC of the back gate guard ring 25X and the source 22 of the second switching element 20B, the distance DXC between the first intermediate part 25XC and the source 22 of the third switching element 20C, and the distance DXD between the second end 25XB of the back gate guard ring 25X and the source 22 of the fourth switching element 20D are all shortened. As a result, as shown in Figure 8, the hold voltage VH (hold voltage VH of Comparative Example 2) becomes higher than the hold voltage VH in the case of the protection element in Figure 5 (Comparative Example 1).

[0052] However, the back gate guard ring 25X shown in Figure 7 includes a second intermediate section 25XD between switching elements 20A and 20B, and a third intermediate section 25XE between switching elements 20C and 20D. As shown in Figure 8, the area ratio of the protective element of Comparative Example 2 in Figure 7 to the protective element of Comparative Example 1 in Figure 5 is 1.61, and the area of ​​the protective element of Comparative Example 2 is larger than the area of ​​the protective element of Comparative Example 1.

[0053] In addition, since the second intermediate section 25XD is positioned between the drain 21 of the first switching element 20A and the drain 21 of the second switching element 20B, and the third intermediate section 25XE is positioned between the drain 21 of the third switching element 20C and the drain 21 of the fourth switching element 20D, the two intermediate sections 25XD and 25XE do not substantially contribute to improving the hold voltage VH.

[0054] In this embodiment, as shown in Figure 2, the back gate guard ring 25 comprises a first portion 25A positioned next to the source 22 of the first switching element 20A, a second portion 25B positioned between the source 22 of the second switching element 20B and the source 22 of the third switching element 20C, and a third portion 25C positioned next to the source 22 of the fourth switching element 20D. In other words, the back gate guard ring 25 of this embodiment does not have the second intermediate portion 25XD and the third intermediate portion 25XE of the back gate guard ring 25X shown in Figure 7. Therefore, as shown in Figure 8, the area ratio of the protection element 10 of this embodiment to the protection element of Comparative Example 1 in Figure 5 is smaller than the area ratio of the protection element of Comparative Example 2 in Figure 7 to the protection element of Comparative Example 1, and the hold voltage VH of the protection element 10 of this embodiment is approximately the same as the hold voltage VH of the protection element of Comparative Example 2.

[0055] (effect) The protective element 10 of this embodiment provides the following effects. (1) The protection element 10 comprises a plurality of switching elements 20, each composed of n-type MOSFETs arranged in a line in one direction and connected in parallel to one another, and a back gate guard ring 25 surrounding the plurality of switching elements 20. The plurality of switching elements 20 include a first switching element 20A, a second switching element 20B, a third switching element 20C, and a fourth switching element 20D, arranged in order. The back gate guard ring 25 comprises a first portion 25A located next to the first switching element 20A on the opposite side from the second switching element 20B, a second portion 25B located between the second switching element 20B and the third switching element 20C, and a third portion 25C located next to the fourth switching element 20D on the opposite side from the third switching element 20C. The source 22 of the first switching element 20A is positioned closer to the first portion 25A than the gate 23 of the first switching element 20A, the source 22 of the second switching element 20B is positioned closer to the second portion 25B than the gate 23 of the second switching element 20B, and the source 22 of the third switching element 20C is positioned closer to the second portion 25B than the gate 23 of the third switching element 20C.

[0056] With this configuration, since the back gate guard ring 25 is positioned near the sources 22 of the first to third switching elements 20A to 20C, the hold voltage VH of the protection element 10 can be increased, thereby suppressing malfunctions of the protection element 10. Furthermore, since the second portion 25B of the back gate guard ring 25 is positioned between the source 22 of the second switching element 20B and the source 22 of the third switching element 20C, the area of ​​the protection element 10 can be reduced compared to a configuration in which each switching element 20A to 20D is individually surrounded by a back gate guard ring, as shown in Figure 7. Therefore, malfunctions of the protection element 10 can be suppressed and the protection element 10 can be miniaturized.

[0057] (2) The distance D1 between the source 22 of the first switching element 20A and the first portion 25A of the back gate guard ring 25, the distance D2 between the source 22 of the second switching element 20B and the second portion 25B, the distance D3 between the source 22 of the third switching element 20C and the second portion 25B, and the distance D4 between the source 22 of the fourth switching element 20D and the third portion 25C are equal to each other.

[0058] This configuration makes it possible to suppress the uneven current flow to specific switching elements in each switching element 20A to 20D. Therefore, it is possible to suppress a decrease in the current value that the protection element 10 can tolerate.

[0059] (3) In a plan view, the second portion 25B of the back gate guard ring 25 is formed in the shape of a single strip extending in a direction (y direction) perpendicular to the arrangement direction (x direction) of the plurality of switching elements 20.

[0060] This configuration allows for a smaller area of ​​the protective element 10 in a plan view compared to a configuration in which multiple second parts 25B are provided. Therefore, the protective element 10 can be miniaturized.

[0061] (4) Each switching element 20A to 20D has a drain 21 provided individually. With this configuration, the first switching element 20A and the second switching element 20B are provided with a common drain, and compared to a configuration where the third switching element 20C and the fourth switching element 20D are provided with a common drain, the volume of the drain 21 can be made larger. Therefore, the current value that the protection element 10 can tolerate can be made larger.

[0062] [Example of changes] The embodiments described above are illustrative of possible forms of the protective element according to this disclosure and are not intended to limit its form. The protective element according to this disclosure may take forms different from those illustrated in the embodiments above. One example is a form in which some of the configurations of the embodiments above are replaced, modified, or omitted, or a form in which new configurations are added to the embodiments above. Furthermore, the following modifications can be combined with each other as long as they do not conflict with technical standards. In the following modifications, parts common to the embodiments above are denoted by the same reference numerals as in the embodiments above, and their descriptions are omitted.

[0063] In the above embodiment, multiple second portions 25B of the back gate guard ring 25 may be provided. In one example, as shown in Figure 9, two second portions 25B of the back gate guard ring 25 are provided spaced apart in the x direction. In this case, the distance D2 between the second portion 25B located next to the second switching element 20B and the source 22 of the second switching element 20B is equal to the distance D3 between the second portion 25B located next to the third switching element 20C and the source 22 of the third switching element 20C. Furthermore, distances D2 and D3 are equal to both the distance D1 between the source 22 of the first switching element 20A and the first portion 25A of the back gate guard ring 25, and the distance D4 between the source 22 of the fourth switching element 20D and the third portion 25C.

[0064] In the above embodiment, as shown in Figure 10, the drain 21 of the first switching element 20A and the drain 21 of the second switching element 20B may be provided as a common drain. This common drain corresponds to the first drain. The drains 21 of the third switching element 20C and the fourth switching element 20D may also be made common. The common drain of the third switching element 20C and the fourth switching element 20D corresponds to the second drain. With this configuration, the area of ​​the protection element 10 can be reduced compared to the case where the drains 21 of each switching element 20A to 20D are provided individually.

[0065] As shown in Figure 10, in the first switching element 20A and the second switching element 20B, the source 22 of the first switching element 20A, the gate 23 of the first switching element 20A, the common drain 21, the gate 23 of the second switching element 20B, and the source 22 of the second switching element 20B are arranged in this order from the first part 25A to the second part 25B in the x direction.

[0066] In the third switching element 20C and the fourth switching element 20D, the source 22 of the third switching element 20C, the gate 23 of the third switching element 20C, the common drain 21, the gate 23 of the fourth switching element 20D, and the source 22 of the fourth switching element 20D are arranged in this order from the second part 25B to the third part 25C in the x-direction.

[0067] In the above embodiment, at least one of the pair of fourth portions 25D from the back gate guard ring 25 may be omitted. In the above embodiment, the protection element 10 was a protection element for protecting a pair of switching elements 201 and 202, but it is not limited to this. For example, the protection element 10 may be a protection element for protecting an LSI. In short, the protection element 10 can be any protection element for electronic components such as semiconductor devices.

[0068] [Note] The technical concepts that can be understood from the above embodiments and each of the above modifications are described below. (Note 1) Multiple switching elements, each composed of an n-type MOSFET and arranged in a line connected in parallel to one another, The system comprises a back gate guard ring surrounding the plurality of switching elements, The plurality of switching elements include a first switching element and a second switching element. The aforementioned back gate guard ring includes a first part and a second part, The first part, the first switching element, the second switching element, and the second part are arranged in that order. The source of the first switching element is located closer to the first portion than the gate of the first switching element. The source of the second switching element is located closer to the second portion than the gate of the second switching element. Protective element.

[0069] (Note 2) The distance between the source and the first part of the first switching element and the distance between the source and the second part of the second switching element are equal to each other. The protective element described in Appendix 1.

[0070] (Note 3) The drains of each of the aforementioned switching elements are provided individually. The protective element described in Appendix 1 or 2.

[0071] (Note 4) The drain, gate, and source of each of the switching elements are arranged along the direction of the arrangement of the plurality of switching elements. The protective element described in Appendix 3.

[0072] (Note 5) In the arrangement direction of the first switching element and the second switching element, the source, gate, and drain of the first switching element are arranged in this order from the first portion to the second portion. In the arrangement direction of the first and second switching elements, the drain, gate, and source of the second switching element are arranged in this order from the first portion toward the second portion. The protective element described in Appendix 4.

[0073] (Note 6) The drain of the first switching element and the drain of the second switching element are provided as a common drain. The protective element described in Appendix 1 or 2.

[0074] (Note 7) The source, gate, and common drain of each of the switching elements are arranged along the direction of the arrangement of the plurality of switching elements. The protective element described in Appendix 6.

[0075] (Note 8) In the first switching element and the second switching element, the source of the first switching element, the gate of the first switching element, the common drain, the gate of the second switching element, and the source of the second switching element are arranged in the same order from the first portion to the second portion in the direction of arrangement of the first and second switching elements. The protective element described in Appendix 7. (Note A1) Multiple switching elements, each composed of an n-type MOSFET and connected in parallel to one another and arranged in a unidirectional line, The system comprises a back gate guard ring surrounding the plurality of switching elements, The plurality of switching elements include a first switching element, a second switching element, a third switching element, and a fourth switching element arranged in order. The aforementioned back gate guard ring is A first portion of the first switching element, located adjacent to the second switching element on the opposite side, A second portion disposed between the second switching element and the third switching element, The fourth switching element comprises a third portion located adjacent to the third switching element on the opposite side, The source of the first switching element is located closer to the first portion than the gate of the first switching element. The source of the second switching element is located closer to the second portion than the gate of the second switching element. The source of the third switching element is located closer to the second portion than the gate of the third switching element. Protective element. (Appendix A2) The source of the fourth switching element is located closer to the third portion than the gate of the fourth switching element. The protective element described in Appendix A1. (Note A3) The distance between the source and the first part of the first switching element, the distance between the source and the second part of the second switching element, the distance between the source and the second part of the third switching element, and the distance between the source and the third part of the fourth switching element are equal to each other. The protective element described in Appendix A2. (Note A4) In a plan view, the second portion is formed in the shape of a single strip extending in a direction perpendicular to the arrangement direction of the plurality of switching elements. The protective element described in any one of the appendices A1 to A3. (Note A5) The drains of each of the aforementioned switching elements are provided individually. The protective element described in one of the appendices A1 to A4. (Note A6) The drain, gate, and source of each of the switching elements are arranged along the direction of the arrangement of the plurality of switching elements. The protective element described in Appendix A5. (Note A7) In the arrangement direction of the plurality of switching elements, the source, gate, and drain of the first switching element are arranged in this order from the first portion to the second portion. In the arrangement direction of the plurality of switching elements, the drain, gate, and source of the second switching element are arranged in this order from the first portion to the second portion. In the arrangement direction of the plurality of switching elements, the source, gate, and drain of the third switching element are arranged in this order from the second portion to the third portion. In the arrangement direction of the plurality of switching elements, the drain, gate, and source of the fourth switching element are arranged in this order from the second portion to the third portion. The protective element described in Appendix A6. (Note A8) The drain of the first switching element and the drain of the second switching element are provided as a common first drain. The drain of the third switching element and the drain of the fourth switching element are provided as a common second drain. The protective element described in one of the appendices A1 to A4. (Note A9) The source, gate, first drain, and second drain of each of the switching elements are arranged along the direction of the arrangement of the plurality of switching elements. The protective element described in Appendix A8. (Note A10) In the first switching element and the second switching element, the source of the first switching element, the gate of the first switching element, the first drain, the gate of the second switching element, and the source of the second switching element are arranged in the same order from the first portion to the second portion in the direction of the arrangement of the plurality of switching elements. In the third and fourth switching elements, the source of the third switching element, the gate of the third switching element, the drain of the second switching element, the gate of the fourth switching element, and the source of the fourth switching element are arranged in this order from the second portion to the third portion in the direction of the arrangement of the plurality of switching elements. The protective element described in Appendix A9. [Explanation of Symbols]

[0076] 10…Protective element 20…Switching elements 20A...First switching element 20B...Second switching element 20C…Third switching element 20D…Fourth switching element 21... Drain 22… Source 23…Gate 25... Back gate guard ring 25A…1st part 25B…Second part 25C…3rd part

Claims

1. Multiple switching elements, each composed of an n-type MOSFET and connected in parallel to one another and arranged in a unidirectional line, A back gate guard ring surrounding the aforementioned plurality of switching elements, Equipped with, The plurality of switching elements include a first switching element, a second switching element, a third switching element, and a fourth switching element arranged in order. The aforementioned back gate guard ring is A first portion of the first switching element, located adjacent to the second switching element on the opposite side, A second portion disposed between the second switching element and the third switching element, The fourth switching element comprises a third portion located adjacent to the third switching element on the opposite side, The source of the first switching element is located closer to the first portion than the gate of the first switching element. The source of the second switching element is located closer to the second portion than the gate of the second switching element. The source of the third switching element is located closer to the second portion than the gate of the third switching element. An element isolation zone is provided between the source and the second portion of the second switching element, and between the source and the second portion of the third switching element, respectively. Protective element.

2. The source of the fourth switching element is located closer to the third portion than the gate of the fourth switching element. The protective element according to claim 1.

3. The distance between the source and the first part of the first switching element, the distance between the source and the second part of the second switching element, the distance between the source and the second part of the third switching element, and the distance between the source and the third part of the fourth switching element are equal to each other. The protective element according to claim 2.

4. In a plan view, the second portion is formed in the shape of a single strip extending in a direction perpendicular to the arrangement direction of the plurality of switching elements. The protective element according to any one of claims 1 to 3.

5. The drains of each of the aforementioned switching elements are provided individually. The protective element according to any one of claims 1 to 4.

6. The drain, gate, and source of each of the switching elements are arranged along the direction of the arrangement of the plurality of switching elements. The protective element according to claim 5.

7. In the arrangement direction of the plurality of switching elements, the source, gate, and drain of the first switching element are arranged in this order from the first portion to the second portion. In the arrangement direction of the plurality of switching elements, the drain, gate, and source of the second switching element are arranged in this order from the first portion to the second portion. In the arrangement direction of the plurality of switching elements, the source, gate, and drain of the third switching element are arranged in this order from the second portion to the third portion. In the arrangement direction of the plurality of switching elements, the drain, gate, and source of the fourth switching element are arranged in this order from the second portion to the third portion. The protective element according to claim 6.

8. The drain of the first switching element and the drain of the second switching element are provided as a common first drain. The drain of the third switching element and the drain of the fourth switching element are provided as a common second drain. The protective element according to any one of claims 1 to 4.

9. The source, gate, first drain, and second drain of each of the switching elements are arranged along the direction of the arrangement of the plurality of switching elements. The protective element according to claim 8.

10. In the first switching element and the second switching element, the source of the first switching element, the gate of the first switching element, the first drain, the gate of the second switching element, and the source of the second switching element are arranged in the same order from the first portion to the second portion in the direction of the arrangement of the plurality of switching elements. In the third and fourth switching elements, the source of the third switching element, the gate of the third switching element, the drain of the second switching element, the gate of the fourth switching element, and the source of the fourth switching element are arranged in this order from the second portion to the third portion in the direction of the arrangement of the plurality of switching elements. The protective element according to claim 9.

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