Transient voltage absorbing element

Abstract

This transient voltage absorbing element (101A) is connected in series with a signal line and in shunt with respect to a reference potential, and comprises: a base material; a first input / output terminal (T1) formed on the base material and connected to the signal line (SL); a second input / output terminal (T2) formed on the base material and connected to the signal line (SL); a reference potential connection terminal (T3) formed on the base material and connected to the reference potential; an internal signal line (SLO) formed in the base material and electrically connected between the first input / output terminal (T1) and the second input / output terminal (T2); and a surge absorbing element connected between the internal signal line (SLO) and the reference potential connection terminal (T3). The magnitude of the impedance of a parasitic capacitive component (Cp1, Cp2) produced between the first input / output terminal (T1) and the second input / output terminal (T2) in the frequency band of a signal propagating in the internal signal line (SLO) is smaller than a resistive component (R1, R2) of the internal signal line (SLO).

Description

Technical Field

[0001] The present invention relates to a transient voltage absorbing element that absorbs transient abnormal voltages caused by ESD (electrostatic discharge) or the like, and surges such as lightning surges and switching surges.

Background Art

[0002] Patent Document 1 discloses a repeater surge protection circuit that protects an amplifier section of a repeater from high voltage surges or high current surges generated due to cable failures or the like, and reduces the occurrence of group delay distortion.

[0003] FIG. 12 is a circuit diagram of the repeater surge protection circuit shown in Patent Document 1. This repeater surge protection circuit includes input / output terminals (9, 10), (11, 12), surge absorbing elements 17, 18, a DC blocking capacitor 19, and T-type four-terminal circuits 20, 21.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the repeater surge protection circuit shown in FIG. 12, since the resistance elements in the T-type four-terminal circuits 20, 21 are provided to act in a low frequency band including DC, the insertion loss of the transmission line becomes large in the entire frequency band. In addition, since the capacitors in the T-type four-terminal circuits 20, 21 are incorporated by mounting on a circuit board, a resistance component R occurs in the wiring and capacitors to which these capacitors are connected. Since this resistance component R is connected in series to the transmission line, the insertion loss is large even in the operating frequency band. In addition, due to the large number of parts in total, the mounting area has to be large.

[0006] Therefore, an object of the present invention is to provide a transient voltage absorption element that has a resistance component in series with a transmission line and reduces insertion loss in a high-frequency band, which is the operating frequency band.

Means for Solving the Problems

[0007] A transient voltage absorption element as an example of the present disclosure is a transient voltage absorption element connected in series to a signal line and shunt-connected to a reference potential, a base material, a first input / output terminal formed on the base material and connected to the signal line, a second input / output terminal formed on the base material and connected to the signal line, a reference potential connection terminal formed on the base material and connected to the reference potential, an internal signal line formed inside the base material and electrically connected between the first input / output terminal and the second input / output terminal, a surge absorption element connected between the internal signal line and the reference potential connection terminal, and includes the magnitude of the impedance in the frequency band of the signal propagating through the internal signal line of the parasitic capacitance component generated between the first input / output terminal and the second input / output terminal is smaller than the resistance component of the internal signal line, characterized by this.

Effects of the Invention

[0008] According to the present invention, a transient voltage absorption element having a low insertion loss in a high-frequency band, which is the operating frequency band, can be obtained while having a resistance component in series with a transmission line.

Brief Description of the Drawings

[0009]

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Embodiments for Carrying Out the Invention

[0010] Hereinafter, several specific examples will be given with reference to the drawings to show a plurality of forms for implementing the present invention. The same reference numerals are given to the same parts in each drawing. For the convenience of explanation, the embodiments are divided into a plurality of embodiments in consideration of the easiness of explanation of the key points or understanding. However, partial substitution or combination of the configurations shown in different embodiments is possible. In the following second and subsequent embodiments, the description of matters common to the first embodiment will be omitted, and only the different points will be described. In particular, the same effects due to the same configuration will not be sequentially mentioned for each embodiment.

[0011] 《First Embodiment》 FIG. 1 is a circuit diagram of a transient voltage absorbing element 101A according to the first embodiment. This transient voltage absorbing element 101A is a transient voltage absorbing element connected in series to the signal line SL and shunted between the reference potential.

[0012] Further, the transient voltage absorbing element 101A includes a first input / output terminal T1 connected to the signal line SL, a second input / output terminal T2 connected to the signal line SL, and a reference potential connection terminal T3 connected to the reference potential.

[0013] An internal signal line SL0 is provided between the first input / output terminal T1 and the second input / output terminal T2. This internal signal line SL0 includes a first resistance component R1 and a second resistance component R2. A diode BD is connected between the internal signal line SL0 and the reference potential connection terminal T3.

[0014] A first parasitic capacitance component Cp1 and a second parasitic capacitance component Cp2 exist between the first input / output terminal T1 and the second input / output terminal T2.

[0015] The first resistance component R1 and the second resistance component R2 act as current limiting resistors that limit low-frequency (mainly direct current) current. Or, they act as termination resistors for impedance matching.

[0016] In the frequency band of the signal propagating through the internal signal line SL0, the first parasitic capacitance component Cp1 has a lower impedance compared to the first resistance component R1, and the second parasitic capacitance component Cp2 has a lower impedance compared to the second resistance component R2. That is, the impedance ABS(1 / jωCp1) with the first parasitic capacitance component as Cp1 is smaller than the first resistance component R1, and the impedance ABS(1 / jωCp2) with the second parasitic capacitance component as Cp2 is smaller than the second resistance component R2. Note that ABS() represents the absolute value.

[0017] Therefore, in the high-frequency band (for example, the 10 GHz band) which is the operating frequency band, the presence of the first resistance component R1 and the second resistance component R2 can be ignored in the transient voltage absorption element 101A, and low insertion loss can be achieved.

[0018] Next, an example of the structure of the transient voltage absorption element 101A is shown. FIG. 2 is a plan view of the transient voltage absorption element 101A, and FIG. 3 is a cross-sectional view of the X-X portion in FIG. 2.

[0019] As shown in FIG. 3, the transient voltage absorption element 101A is composed of a semiconductor substrate portion and a rewiring portion. The semiconductor substrate portion and the rewiring portion correspond to the "base material" according to the present invention.

[0020] The semiconductor substrate portion includes a semiconductor substrate Sub, an epitaxial layer Epi, an insulator Ins1, and conductors Cond11, Cond12, Cond13. The semiconductor substrate Sub is, for example, a Si substrate, a GaAs substrate, or the like. As the material of the insulator Ins1, a SiO2 film may be used. As the materials of the conductors Cond11, Cond12, Cond13, for example, Al or Cu may be used.

[0021] The rewiring portion includes insulators Ins2, Ins3, Ins4, Ins5, a conductor Cond2, and a pad Pad.

[0022] Insulator Ins2 is, for example, SiN, and insulators Ins3, Ins4, and Ins5 are organic resins such as epoxy. For the material of conductor Cond2, for example, Cu may be used. Pad is composed of, for example, a conductor for forming a multi-layer electrode. For example, Pad may include an underlayer and a surface layer. Further, it may further include an adhesion layer between the underlayer and the surface layer. Ni may be used for the material of the underlayer, Ti may be used for the material of the adhesion layer, and Au may be used for the material of the surface layer.

[0023] The first terminal electrode E1, the second terminal electrode E2, and the third terminal electrode E3 shown in FIG. 2 are constituted by the pad Pad shown in FIG. 3. Further, the first resistance component R1 and the second resistance component R2 are constituted by the conductor Cond2 in the lower layer of the rewiring portion. That is, the conductor Cond2 in the lower layer of the rewiring portion is a wiring pattern of a conductor having a predetermined resistivity. The upper conductor Cond2 and the lower conductor Cond2 are connected by via conductors V11 and V12. The lower conductor Cond2 and the conductor Cond11 in the semiconductor substrate portion are connected by a via conductor V21.

[0024] In such a structure, in order to increase the resistance values of the first resistance component R1 and the second resistance component R2 shown in FIG. 1, it is effective to reduce the film thickness of the wiring pattern formed by the conductor Cond2 or to narrow the line width of the wiring pattern. Also, it is effective to increase the length of the via conductors V11 and V12 or to reduce the diameter of the via conductors V11 and V12.

[0025] As shown in FIG. 2, a diode BD is formed between the conductor Cond11 and the conductor Cond13. The conductor Cond3 and the third terminal electrode E3 are connected through via conductors V22 and a conductor.

[0026] The upper layer pattern and the lower layer pattern of the conductor Cond2 that constitutes the internal signal line SLO face each other via the insulator Ins4. The first parasitic capacitance component Cp1 occurs in the region where the upper layer pattern and the lower layer pattern face each other at the location that constitutes the first resistance component R1. The second parasitic capacitance component Cp2 occurs in the region where the upper layer pattern and the lower layer pattern face each other at the location that constitutes the second resistance component R2.

[0027] The first terminal electrode E1 shown in FIG. 2 corresponds to the first input / output terminal T1 shown in FIG. 1, the second terminal electrode E2 corresponds to the second input / output terminal T2, and the third terminal electrode E3 corresponds to the reference potential connection terminal T3.

[0028] FIG. 4 is a circuit diagram of another transient voltage absorbing element 101B according to the first embodiment. In the transient voltage absorbing element 101A shown in FIG. 1, an example is shown where the resistance component R1 exists in the front stage of the connection point of the diode BD with respect to the internal signal line SL0, and the resistance component R2 exists in the rear stage. However, in the transient voltage absorbing element 101B, the resistance component R2 exists only in the rear stage of the connection point of the diode BD with respect to the internal signal line SL0. This resistance component R2 is used, for example, as a termination resistance.

[0029] Thus, the present invention can be similarly applied to a transient voltage absorbing element in which the resistance component inserted into the internal signal line is provided only in the rear stage of the diode BD. Similarly, the present invention can be similarly applied to a transient voltage absorbing element in which the resistance component inserted into the internal signal line is provided only in the front stage of the diode BD.

[0030] FIG. 5(A) is a diagram showing a circuit constituted by the first resistance component R1 and the first parasitic capacitance component Cp1 of the transient voltage absorbing element 101A, and FIG. 5(B) is its equivalent circuit diagram.

[0031] Since the insulator Ins4 is a dielectric layer, as shown in FIG. 5(A), a parasitic capacitance is formed between the conductor Cond2 constituting the first resistance component R1 and the first terminal electrode E1. When this parasitic capacitance is equivalently represented by a single capacitor, as shown in FIG. 5(B), it becomes a circuit in which a first parasitic capacitance component Cp1 is connected in parallel to the first resistance component R1. The same applies to the relationship between the second resistance component R2 and the second parasitic capacitance component Cp2.

[0032] FIG. 6 is a cross-sectional view of the diode BD formation region. However, FIG. 6 shows the semiconductor substrate portion. The semiconductor substrate portion of the diode BD formation region includes a semiconductor substrate Sub, an epitaxial layer Epi, a trench TR, and an insulator Ins1.

[0033] The epitaxial layer Epi is, for example, an n-type epitaxial layer and is formed on the surface of the semiconductor substrate Sub. A p+ region and an n+ region are formed on the surface layer of the epitaxial layer Epi. An insulator Ins1 is formed on the surface of the epitaxial layer Epi. Conductors Cond11, Cond12, and Cond13 are formed from the surface of the epitaxial layer Epi to the p+ region and the n+ region. Also, a trench TR is formed from the insulator Ins1 to the semiconductor substrate Sub.

[0034] The epitaxial layer Epi, the p+ region, and the n+ region constitute a diode. When the epitaxial layer Epi is an n-type epitaxial layer, a depletion layer is formed at the interface between the epitaxial layer Epi and the p+ region. The trench TR separates between the diodes.

[0035] Note that the diode for surge absorption may be a Zener diode that conducts when the Zener voltage is exceeded, in addition to a diode that conducts when the forward voltage drop is exceeded.

[0036] FIG. 7 is a circuit diagram of diode BD. The dashed arrows in FIG. 7 indicate the path and direction of the current flowing through diode BD. That is, when a positive potential is applied to conductor Cond11 in FIG. 7 and a voltage exceeding the forward voltage of each diode is applied to each diode, current flows along the path of conductor Cond11 → diode D11 → conductor Cond12 → diode D12 → conductor Cond13. Also, when a positive potential is applied to conductor Cond13 in FIG. 7 and a voltage exceeding the forward voltage of each diode is applied to each diode, current flows along the path of conductor Cond13 → diode D21 → conductor Cond12 → diode D22 → conductor Cond11.

[0037] In the examples shown above, the resistance component is composed of a conductor, but the resistance component may be composed of other resistors or conductor patterns.

[0038] 《Second Embodiment》 In the second embodiment, an example of forming a parasitic capacitance with a structure different from the example shown in the first embodiment will be shown.

[0039] FIG. 8 is a plan view of the main part of the transient voltage absorbing element 102 according to the second embodiment. The surface of the transient voltage absorbing element 102 is covered with an insulator Ins5 in the same manner as the example shown in FIG. 3 in the first embodiment, and the openings of the insulator Ins5 are the first terminal electrode E1, the second terminal electrode E2, and the third terminal electrode E3. These first terminal electrode E1, second terminal electrode E2, and third terminal electrode E3 are composed of a part of a conductor and a pad Pad in the same manner as the example shown in FIG. 3 in the first embodiment.

[0040] The first resistance component R1 and the second resistance component R2 are formed by the above conductor Cond2. The conductor Cond2 constituting the first resistance component R1 forms a first parasitic capacitance component Cp1 between its patterns. Similarly, the conductor Cond2 constituting the second resistance component R2 forms a second parasitic capacitance component Cp2 between its patterns.

[0041] A diode BD is provided between the connection part of one end of the first resistance component R1 and the second resistance component R2 and the third terminal electrode E3. However, in FIG. 8, this diode BD is represented by a circuit symbol. The basic structure of this diode BD is the same as the diode BD shown in FIG. 2.

[0042] FIG. 9(A) is a diagram showing a circuit constituted by a first resistance component R1 and a first parasitic capacitance component Cp1 of a transient voltage absorbing element according to a second embodiment, and FIG. 9(B) is an equivalent circuit diagram thereof.

[0043] Since the conductor Cond2 constituting the first resistance component R1 has a bent pattern such as a meander line, a first parasitic capacitance component Cp1 is formed between the conductors Cond2 in the plane. When these first parasitic capacitance components Cp1 are equivalently represented by a single capacitor, as shown in FIG. 9(B), it becomes a circuit in which the first parasitic capacitance component Cp1 is connected in parallel to the first resistance component R1. The same applies to the relationship between the second resistance component R2 and the second parasitic capacitance component Cp2.

[0044] As shown in this embodiment, the parasitic capacitance may be a parasitic capacitance generated between portions of a pattern formed by a resistor or a conductor constituting a resistance component.

[0045] In the transient voltage absorbing element 102 having the structure shown in this second embodiment, in order to increase the resistance values of the first resistance component R1 and the second resistance component R2, it is effective to lengthen the routing of the conductor pattern or to reduce the film thickness of the conductor.

[0046] Thus, when a resistance component is constituted by a single-layer conductor Cond2, the parasitic capacitance generated between its wiring patterns may be utilized.

[0047] In the examples shown above, the resistance component is constituted by a conductor, but the resistance component may be constituted by other resistor or conductor patterns.

[0048] 《Third Embodiment》 In the third embodiment, an example of forming a parasitic capacitance with a structure different from the examples shown in the first and second embodiments will be described.

[0049] FIG. 10 is a plan view of a main part of a transient voltage absorbing element 103 according to the third embodiment. The transient voltage absorbing element 103 is composed of a semiconductor substrate portion and a rewiring portion, similar to the example shown in the first embodiment. The first terminal electrode E1 shown in FIG. 10 corresponds to the first input / output terminal T1 shown in FIG. 1, the second terminal electrode E2 corresponds to the second input / output terminal T2, and the third terminal electrode E3 corresponds to the reference potential connection terminal T3.

[0050] A conductor Cond12 that conducts to conductors Cond11 and Cond13 is formed in the rewiring portion. The first terminal electrode E1, the second terminal electrode E2, and the third terminal electrode E3 shown in FIG. 10 are composed of an upper-layer conductor Cond2 and a pad in the rewiring portion. Also, a first resistance component R1 and a second resistance component R2 are formed by a lower-layer conductor Cond2 in the rewiring portion. The upper-layer conductor Cond2 and the lower-layer conductor Cond2 are connected by via conductors V11 and V12. The lower-layer conductor Cond2 and the conductor Cond11 of the semiconductor substrate portion are connected by a via conductor V21.

[0051] As shown in FIG. 10, a diode BD is formed between the conductor Cond11 and the conductor Cond13. The conductor Cond13 and the third terminal electrode E3 are connected through a via conductor V22 and a conductor. The configuration of the diode BD is the same as that shown in the first embodiment.

[0052] FIG. 11(A) is a diagram showing a circuit composed of the first resistance component R1 and the first parasitic capacitance component Cp1 of the transient voltage absorbing element 103, and FIG. 11(B) is its equivalent circuit diagram.

[0053] As shown in FIG. 11(A), a first parasitic capacitance component Cp1 is formed between conductors Cond2 that constitute the first resistance component R1. Also, a first parasitic capacitance component Cp1 is formed between the conductor Cond2 that constitutes the first resistance component R1 and the first terminal electrode E1. When this parasitic capacitance is equivalently represented by a single capacitor, as shown in FIG. 11(B), it becomes a circuit in which the first parasitic capacitance component Cp1 is connected in parallel to the first resistance component R1. The same applies to the relationship between the second resistance component R2 and the second parasitic capacitance component Cp2.

[0054] In the transient voltage absorbing element 103 having the structure shown in this third embodiment, to increase the resistance values of the first resistance component R1 and the second resistance component R2, it is effective to lengthen the routing of the pattern of the conductor Cond2. Also, it is effective to reduce the film thickness of the wiring pattern formed by the conductor Cond2, or to narrow the line width of this wiring pattern. Furthermore, it is also effective to increase the length of the via conductors V11, V12, or to narrow the diameter of the via conductors V11, V12.

[0055] Finally, the descriptions of the above embodiments are illustrative in all respects and not restrictive. Modifications and changes are appropriately possible for those skilled in the art. The scope of the present invention is shown not by the above embodiments but by the claims. Furthermore, the scope of the present invention includes changes from the embodiments within the scope equivalent to the claims.

[0056] For example, in each of the above-described embodiments, a transient voltage absorbing element connected to a single signal line has been shown. However, a transient voltage absorbing element for a differential signal line may be configured by providing a pair of these transient voltage absorbing elements on a single base material.

[0057] Also, in each of the above-described embodiments, an example in which a surge absorbing element is constituted by a plurality of diodes has been shown. However, the surge absorbing element may be constituted by a Zener diode or a thyristor.

Explanation of Reference Numerals

[0058] BD... Diode Cond11, Cond12, Cond13, Cond2, Cond3… Conductor Cp1… First parasitic capacitance component Cp2… Second parasitic capacitance component D11, D12, D21, D22… Diode E1… First terminal electrode E2… Second terminal electrode E3… Third terminal electrode Epi… Epitaxial layer Ins1, Ins2, Ins3, Ins4, Ins5… Insulator Pad… Pad R1… First resistance component R2… Second resistance component Sub… Semiconductor substrate SL… Signal line SL0… Internal signal line T1… First input / output terminal T2… Second input / output terminal T3… Reference potential connection terminal TR… Trench V11, V12, V21, V22… Via conductor 17, 18… Surge absorption element 19… DC blocking capacitor 20, 21… T-shaped 4-terminal circuit 101A, 101B, 102, 103… Transient voltage absorption element

Claims

1. A transient voltage absorption element that is connected in series to a signal line and shunted between the signal line and a reference potential, comprising a base material, a first input / output terminal formed on the base material and connected to the signal line, a second input / output terminal formed on the base material and connected to the signal line, a reference potential connection terminal formed on the base material and connected to the reference potential, an internal signal line formed inside the base material and electrically connected between the first input / output terminal and the second input / output terminal, a surge absorption element connected between the internal signal line and the reference potential connection terminal, wherein the magnitude of the impedance in the frequency band of the signal propagating through the internal signal line of the parasitic capacitance component generated between the first input / output terminal and the second input / output terminal is smaller than the resistance component of the internal signal line. A transient voltage absorption element characterized by the above.

2. The internal signal line is a wiring pattern of a conductor having a predetermined resistance component formed on the base material, and is directly connected to the first input / output terminal and the second input / output terminal. The transient voltage absorption element according to claim 1, characterized by the above.

3. The internal signal line is formed in one layer, and the parasitic capacitance component is generated in a plane by the wiring pattern. The transient voltage absorption element according to claim 2, characterized by the above.

4. The internal signal line includes a meander shape. The transient voltage absorption element according to claim 3.

5. The parasitic capacitance component is generated between the internal signal line and at least one of the first input / output terminal and the second input / output terminal. The transient voltage absorption element according to claim 2, characterized by the above.

6. The base material further includes a dielectric layer, and the internal signal line is disposed at a position facing at least one of the first input / output terminal and the second input / output terminal with the dielectric layer interposed therebetween. The transient voltage absorption element according to claim 5, characterized by the above.

7. The base material further includes a dielectric layer, and two or more layers of the internal signal line are formed at positions sandwiching a dielectric film, and the parasitic capacitance component is formed in a region sandwiching the dielectric. The transient voltage absorption element according to claim 2, characterized by the above.

8. The resistance component and the parasitic capacitance component are respectively generated between the first input / output terminal and the reference potential connection terminal and between the second input / output terminal and the reference potential connection terminal. The transient voltage absorbing element according to claim 2, characterized in that...

9. The wiring pattern of the internal signal line has a symmetrical shape with respect to the surge absorbing element. The transient voltage absorbing element according to claim 8, characterized in that...

10. The first input / output terminal and the second input / output terminal are arranged at symmetrical positions with respect to the reference potential connection terminal. The transient voltage absorbing element according to claim 8, characterized in that...

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