JPH08274263A - noise filter - Google Patents

Abstract

(57) [Summary] [Structure] A noise filter based on a semiconductor process. The first metal wiring 3 is formed on the semiconductor substrate 1 via the first insulating film 6.
Is formed into a spiral shape. Second metal wirings 5 are spirally opposed to each other with a second insulating film 7 interposed therebetween. The first metal wiring 3 operates as a signal line. The extraction electrode 9 of the second metal wiring 5 and the lead frame 12 to which the semiconductor substrate 1 is bonded with the conductive paste 10 are connected by a bonding wire 13, and the second metal wiring 5 and the semiconductor substrate 1 are the same. It becomes a potential (ground). [Effect] Since the built-in capacitance is determined by the sum of the distributed capacitance formed between the first metal wiring and the second metal wiring and the distributed capacitance formed between the semiconductor substrate and the first metal wiring. A high-capacity distributed constant low-pass filter can be realized with almost no change in the number of process steps. Furthermore, by adding a protection diode in the process step, it is possible to increase only the electrostatic withstand capability without degrading the frequency attenuation characteristic.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise filter by a semiconductor process.

[0002]

2. Description of the Related Art With the recent increase in speed of electronic equipment, measures against noise in internal circuits have become indispensable, and the demand for noise filters used in internal circuits is increasing year by year. Further, in order to reduce the total cost of products, the market requires low-cost and high-performance noise filters. Recently, a noise filter using a semiconductor process that can be mass-produced at low cost has been attracting attention.

A conventional noise filter utilizing a semiconductor process is disclosed in Japanese Patent Laid-Open No. 6-77711. FIG. 14 shows a cross-sectional view of a conventional noise filter, and FIG. 15 shows an equivalent circuit of the conventional noise filter.

In FIG. 14, 1 is a semiconductor substrate, 2 is an insulating film, 3 is a first metal wiring, 5 is a second metal wiring, and 8 is an extraction electrode of the first metal wiring 3.

In the conventional noise filter process, the first metal wiring 3 is spirally formed on the semiconductor substrate 1, then the insulating film 2 is formed on the surface of the first metal wiring 3, and A second metal wiring 5 is spirally formed on the insulating film 2, and the first metal wiring 3 is formed.
The extraction electrode 8 is formed at the end of the.

After the above steps, bonding is performed to the lead electrodes 8 on both ends of the second metal wiring 5 and the end of the first metal wiring 3.

In FIG. 15, 3 is the first metal wiring, 5 is the second metal wiring, 8 is the extraction electrode of the first metal wiring 3,
Reference numeral 5 is a distributed capacitance formed between the first metal wiring 3 and the second metal wiring 5, and 20 is an inductance possessed by the first metal wiring 3 and the second metal wiring 5.

The first metal wiring 3 and the second metal wiring 5 formed in a spiral shape have a predetermined inductance 20, and the insulating film 2 of FIG. 14 acts as a dielectric to cause the first metal wiring to flow. Since the distributed capacitance 15 is formed between the third metal wiring 5 and the third metal wiring 5, it can be used as a distributed constant type low-pass filter based on the inductance and the distributed capacitance.

[0009]

In a conventional noise filter using a semiconductor process, the built-in capacitance is determined by the relative permittivity and the film thickness of the insulating film that insulates the first metal wiring and the second metal wiring. Therefore, when a high-capacity noise filter is made, an insulating material having a large relative dielectric constant must be used, or the insulating film must be thinned if there is no suitable insulating material. In the latter case, the thinner the insulating film, the weaker it is against electrostatic breakdown, and the minimum value of the film thickness is determined from the viewpoint of the electrostatic resistance, making it difficult to make a high-capacity noise filter.

In addition, the static electricity resistance of the first metal wiring and the second metal wiring is
It is determined by the film thickness value of the insulating film that insulates the metal wiring, and there is a problem that electrostatic breakdown of the noise filter cannot be avoided if static electricity with a voltage exceeding the product of the breakdown electric field of the insulating film and the film thickness value enters. It was

An object of the present invention is to solve the above-mentioned problems, and to make a noise filter having substantially the same cost as the conventional one and a higher capacity or a larger electrostatic withstand capability than the conventional one without significantly changing the conventional structure. It is possible to do that.

[0012]

[Means for Solving the Problems]

(Means 1) In the noise filter according to the present invention, the first metal wiring is spirally formed on the semiconductor substrate via the first insulating film, and the second insulating film is provided on the first metal wiring. So that the second metal wiring is spirally opposed to each other, and the first metal wiring is operated as a signal line so that the second metal wiring and the semiconductor substrate have the same potential (ground). The lead electrode of the second metal wiring and the lead frame where the semiconductor substrate is bonded with a conductive paste are connected by a bonding wire.

(Means 2) In the noise filter of means 1, the sheet resistance of the surface of the semiconductor substrate is lowered.

(Means 3) In the noise filter according to the present invention, the first metal wiring is spirally formed on the semiconductor substrate through the first insulating film, and the second insulation is formed on the first metal wiring. Second metal wirings are formed to face each other in a spiral shape with a film interposed therebetween, and the first metal wirings are operated as signal lines, so that the second metal wirings and the semiconductor substrate have the same potential (ground). So that a part of the second metal wiring is
It is characterized in that it is in direct contact with the semiconductor substrate via a first metal wiring (different from the signal line) or directly.

(Means 4) The noise filter of means 3 is characterized in that the sheet resistance of the surface of the semiconductor substrate is lowered.

(Means 5) In the noise filter according to the present invention, the first metal wiring is spirally formed on the semiconductor substrate through the first insulating film, and the second insulating film is formed on the first metal wiring. The second metal wiring is spirally opposed to the second metal wiring via the film, and the third metal wiring is spirally opposed to the second metal wiring via the third insulating film. , Operating the second metal wiring as a signal line,
A part of the third metal wiring is provided with the second metal wiring so that the first metal wiring and the third metal wiring have the same potential (ground).
And is in direct contact with the first metal wiring through the metal wiring (different from the signal line) or directly.

(Means 6) In the noise filter of means 5, the roles of the signal line and the ground are exchanged.

(Means 7) In the noise filter according to the present invention, the first metal wiring is spirally formed on the semiconductor substrate via the first insulating film, and the second insulation is formed on the first metal wiring. Second metal wirings are formed to face each other in a spiral shape with a film interposed therebetween, and the first metal wirings are operated as signal lines, so that the second metal wirings and the semiconductor substrate have the same potential (ground). As described above, the lead electrode of the second metal wiring and the lead frame where the semiconductor substrate is adhered with the conductive paste are connected by a bonding wire, and the lead electrode is attached to a part of the surface of the semiconductor substrate. A region of a conductivity type different from the conductivity type of the semiconductor substrate (referred to as a region 1) is formed, and a part of the first metal wiring is in direct contact with the region 1.

(Means 8) In the noise filter of means 7, the extraction electrode of the second metal wiring (ground) is formed inside the spiral, and the extraction electrode of the input terminal of the first metal wiring (signal line) is formed. Is formed inside the spiral, the extraction electrode of the output terminal is formed outside the spiral,
The region 1 is formed in the vicinity of the extraction electrode of the input terminal.

(Means 9) In the noise filter of means 7, the extraction electrode of the second metal wiring (ground) is formed inside the spiral, and the extraction electrode of the input terminal in the first metal wiring (signal line). Is formed inside the spiral, the extraction electrode of the output terminal is formed outside the spiral,
The region 1 is formed in the vicinity of the extraction electrode of the output terminal.

(Means 10) The noise filter of means 7 is characterized in that the contents of means 8 and 9 are satisfied at the same time.

(Means 11) The noise filter of the means 7 is characterized in that the sheet resistance of the surface of the semiconductor substrate is lowered.

(Means 12) In the noise filter according to the present invention, the first metal wiring is spirally formed on the semiconductor substrate via the first insulating film, and the second insulating film is formed on the first metal wiring. Second metal wirings are formed on the spiral so as to be opposed to each other through a film, and the first metal wirings are operated as signal lines, and the second metal wirings and the semiconductor substrate have the same potential (ground). As described above, a part of the second metal wiring is in contact with the semiconductor substrate through the first metal wiring (different from the signal line) or directly, and a part of the surface of the semiconductor substrate is formed. A region of a conductivity type different from the conductivity type of the semiconductor substrate (referred to as region 1) is formed, and a part of the first metal wiring (signal line) is in direct contact with the region 1. And

(Means 13) In the noise filter of means 12, the sheet resistance of the surface of the semiconductor substrate is lowered.

(Means 14) The noise filter of means 7 is characterized in that the region 1 is partially or entirely formed in a spiral shape under the first metal wiring.

[0026]

In the noise filter according to the present invention, the built-in capacitance is divided into a distributed capacitance formed between the first metal wiring and the second metal wiring and a distributed capacitance formed between the semiconductor substrate and the first metal wiring. Since it is determined by the sum, it is possible to make a noise filter with a higher capacity than before. Further, the frequency attenuation characteristic can be improved.

The same effect can be obtained even if the metal wiring has three layers.

Further, by forming a protection diode against electrostatic breakdown between the first metal wiring and the semiconductor substrate, it is possible to increase the electrostatic withstand capability without degrading the frequency attenuation characteristic as compared with the noise filter without the diode.

Further, when the protection diode is provided, it is possible to make a noise filter having a higher capacity than when the protection diode is not provided, and the chip size can be reduced accordingly.

[0030]

EXAMPLES First, examples of the means 1 of the present invention will be described.

FIG. 1 shows a sectional view of the noise filter according to the means 1. The structure is almost the same as the conventional one, 1 is a semiconductor substrate, 6 is a first insulating film, 3 is a first metal wiring, 7 is a second insulating film, 5 is a second metal wiring, and 8 is a first metal wiring. The extraction electrode of the metal wiring 3, and the extraction electrode 9 of the second metal wiring 5.
Is a conductive paste, 12 is a lead frame, and 13 is a bonding wire.

In the process step, the first insulating film 6 is formed on the semiconductor substrate 1, and then the first insulating film 6 is formed on the first insulating film 6.
The metal wiring 3 of is formed in a spiral shape, and then the second wiring is formed on the surface.
Of the second insulating film 7 is formed by etching, and then the second insulating film 7 is removed by etching only at the portions where the lead electrodes 8 are formed at both ends of the first metal wiring 3. The second metal wiring 5 is spirally formed on the upper surface, and the extraction electrodes 8 are formed on both ends of the first metal wiring 3. Finally, a passivation film is formed by CVD or the like, and the passivation film is removed by etching only the portions of the extraction electrode 8 on both ends of the first metal wiring 3 and the extraction electrode 9 of the second metal wiring 5. To do. (The passivation film is omitted in FIG. 1)
When the lead electrode 9 of the metal wiring 5 and the lead electrodes 8 at both ends of the first metal wiring 3 are bonded, the difference from the prior art is that the second metal wiring 5 and the semiconductor substrate 1 have the same potential (ground). First, the extraction electrode 9 of the second metal wiring 5 and the lead frame 12 where the semiconductor substrate 1 is bonded with the conductive paste 10 are connected by the bonding wire 13.

FIG. 2 shows an equivalent circuit of the noise filter according to the means 1. 3 is the first metal wiring, 5 is the second metal wiring, 15 is the distributed capacitance formed between the first metal wiring 3 and the second metal wiring 5, and 20 is the first metal wiring 3 and the first metal wiring 3. Two
The inductance is owned by the metal wiring 5 of FIG. Reference numeral 16 is a distributed capacitance (MOS capacitance) formed between the first metal wiring 3 and the semiconductor substrate 1, 12 is a lead frame, 9 is an extraction electrode of the second metal wiring 5, 8 is the first metal wiring 3 Lead-out electrodes at both ends of and are bonding wires.

As is apparent from FIG. 2, according to the means 1, the distributed capacitance 15 formed between the first metal wiring 3 and the second metal wiring 5, the semiconductor substrate 1 and the first metal wiring 3 are formed. A distributed constant type low-pass filter is formed by the distributed capacitance 16 formed between the first and second spirals and the inductance possessed by the spirally formed first metal wiring 3 and second metal wiring 5.

Conventionally, the built-in capacitance is determined by the distributed capacitance formed between the first metal wiring and the second metal wiring, but according to the means 1, the built-in capacitance is determined by the first metal wiring. Since it is determined by the sum of the distributed capacitance formed between the second metal wiring and the distributed capacitance formed between the semiconductor substrate and the first metal wiring, the process cost does not increase significantly compared to the conventional method. It is possible to make a noise filter with a higher capacity than before.

Further, static electricity from the outside is divided into a distributed capacitance formed between the first metal wiring and the second metal wiring and a distributed capacitance formed between the semiconductor substrate and the first metal wiring. Since it is absorbed and absorbed, there is an effect that the static electricity resistance is improved as compared with the conventional case.

Further, there are the following effects.

In the conventional noise filter, the first metal wiring is grounded and the second metal wiring is used as the signal line. Therefore, the noise entering the second metal wiring (signal line) is the first metal. It escapes to the first metal wiring (ground) via the distributed capacitance formed between the wiring and the second metal wiring.

In the conventional example, there is a peak at the attenuation point in the frequency attenuation characteristic in the vicinity of the cutoff frequency (f = 1 / 2π / √ (LC)) determined by the inductance and the distributed capacitance in the path through which noise escapes.

According to the means 1, the noise that has entered the first metal wiring (signal line) is transmitted to the second metal through the distributed capacitance formed between the first metal wiring and the second metal wiring. In addition to the route that escapes to the wiring (ground) (equivalent to the conventional route through which noise escapes and is referred to as route 1), another noise that enters the first metal line (signal line) is used as the first metal line. A path (referred to as path 2) is formed to escape to the semiconductor substrate (ground) and the lead frame via the distributed capacitance formed between the semiconductor substrates, and a plurality of paths for escape of noise are formed.

In this case, the cutoff frequency (f1 = 1 / 2π) determined by the inductance and the distributed capacitance in the path 1
/ √ (L1C1)) has a peak at the attenuation point in the frequency attenuation characteristic, and the cutoff frequency (f2 = 1/2) determined by the inductance and the distributed capacitance in the path 2
Even in the vicinity of π / √ (L2C2), there is a peak at the attenuation point in the frequency attenuation characteristic, and two peaks at the attenuation point in the frequency attenuation characteristic are created.

Here, the inductance L1 in the path 1
And the distributed capacitance C1 and the inductance L2 in the path 2
And the distributed capacitance C2 by adjusting the cutoff frequency of the path 1 (f1 = 1 / 2π / √ (L1C1)) to the cutoff frequency of the path 2 (f2 = 1 / 2π / √ (L2C
If 2)) is adjusted to be high, another attenuation point peak can be generated at a frequency higher than the conventional cutoff frequency, so the attenuation characteristic in the high frequency band becomes good,
There is an effect that the frequency attenuation characteristic is improved as compared with the conventional case. Also, L1 and C are set so that f1 and f2 have the same value.
By adjusting 1, L2 and C2, it is possible to obtain a frequency attenuation characteristic in which the peak of the attenuation point is very large at a specific frequency.

Next, an embodiment of the means 3 according to the present invention will be described.

FIG. 3 shows a sectional view of the noise filter by the means 3. The structure is almost the same as the conventional one, 1 is a semiconductor substrate, 6 is a first insulating film, 3 is a first metal wiring, 7 is a second insulating film, 5 is a second metal wiring, and 8 is a first metal wiring. The extraction electrode of the metal wiring 3, and the extraction electrode 9 of the second metal wiring 5.
Is a conductive paste, 12 is a lead frame, 11 is a first
Of the metal wiring (different from the first metal wiring 3).

In the process step, the first insulating film 6 is formed on the semiconductor substrate 1, and then a part of the first insulating film 6 is removed by etching. Then, a first film is formed on the first insulating film 6.
Of the metal wiring 3 is spirally formed, and the first metal wiring 11 is formed on the portion where the first insulating film 6 is removed.
To form. Next, the second insulating film 7 is formed on the surface, and then only the portions where the extraction electrodes 8 at both ends of the first metal wiring 3 and the portions of the first metal wiring 11 are formed are the second insulating film 7. Are removed by etching, then the second metal wiring 5 is spirally formed on the second insulating film 7, and the extraction electrodes 8 are formed on both ends of the first metal wiring 3. A contact is made between a part of the second metal wiring 5 and the first metal wiring 11. The rest is the same as the means 1, and the description is omitted.

After the process steps are completed, the lead-out electrodes 9 of the second metal wiring 5 and the lead-out electrodes 8 at both ends of the first metal wiring 3 are bonded.

Here, a part of the second metal wiring 5 is the first metal wiring 11 (the first metal which is a signal line) so that the second metal wiring 5 and the semiconductor substrate 1 have the same potential (ground). It is the same as the means 1 except that the semiconductor substrate 1 is in contact with the semiconductor substrate 1 via the wiring 3).

FIG. 4 shows an equivalent circuit of the noise filter by the means 3. 1 is a semiconductor substrate, 11 is a first metal wiring and is the same as in FIG. 2 except that a distributed constant type low-pass filter is formed.

With the structure of the means 3, the same effect as that of the means 1 can be obtained.

FIG. 5 shows a sectional view of the noise filter of the means 4 according to the present invention. The means 4 is an example in which the sheet resistance of the surface of the semiconductor substrate is lowered in the means 3.

It is the same as FIG. 3 except that the well region 14 of high concentration is formed in order to reduce the sheet resistance on the surface of the semiconductor substrate 1. In this case, the semiconductor substrate 1 (ground), the first metal wiring 1 and the first metal wiring 3 are distributed via the distributed capacitance formed between the first metal wiring 3 and the semiconductor substrate 1.
In the route (route 2) that escapes to the first and second metal wirings 5, the noise passes through the well region 14 having a high resistance and a low resistance, so that the noise can easily escape. For example, if the equivalent resistance of the semiconductor substrate when there is no well region in the path 2 is 1 kΩ and C = 100 pF, then τ = CR = 1 /
From f, f = 10 MHz, and the high frequency noise of 10 MHz or more is greatly affected by the equivalent resistance, and the frequency attenuation characteristic deteriorates. However, if a high-concentration well region is formed and the equivalent resistance of the semiconductor substrate is lowered to 50Ω, then f = 200 MHz from the above equation, and 200 M
Noise up to Hz can be satisfactorily removed. Further, like the means 2, the sheet resistance on the surface of the semiconductor substrate may be lowered in the means 1 in the means 1.

Next, an embodiment of the means 5 according to the present invention will be described.

FIG. 6 shows a sectional view of the noise filter by the means 5. The structure has three layers of metal wiring, 1 is a semiconductor substrate, 6 is a first insulating film, 3 is a first metal wiring, 7 is a second insulating film, 5 is a second metal wiring, and 30 is a second metal wiring. 3. Insulating film 3; 31, third metal wiring; 38, third metal wiring 31
Is a lead electrode of the second metal wiring 5, 10 is a conductive paste, 12 is a lead frame, and 32 is a second metal wiring (different from the second metal wiring 5).

In the process step, a first insulating film 6 is formed on the semiconductor substrate 1, and then a first insulating film 6 is formed on the first insulating film 6.
The metal wiring 3 is formed in a spiral shape. Next, a second insulating film 7 is formed on the surface, and then the second insulating film 7 on the surface of only a part of the first metal wiring 3 is removed by etching.
Next, the second metal wiring 5 is formed in a spiral shape on the second insulating film 7, and the second metal wiring 32 and the first metal wiring 3 are contacted with each other. Next, a third insulating film 30 is formed on the surface, and then the second metal wiring 3 is formed.
2 and the extraction electrodes 9 at both ends of the second metal wiring 5
The third insulating film 30 is removed only by etching, and then the third metal wiring 31 is spirally formed on the third insulating film 30 and the second metal wiring 5 is formed.
Extraction electrodes 9 are formed on both ends of the second metal wiring 3
Contact is made between the second metal wiring 31 and the third metal wiring 31, and the extraction electrode 38 of the third metal wiring 31 is formed. Finally, a passivation film is formed, and the extraction electrodes 9 on both ends of the second metal wiring 5 and the extraction electrodes 38 of the third metal wiring 31 are formed.
Then, the passivation film is removed by etching only in the part of FIG. After the process step (the passivation film is omitted in FIG. 6), bonding is performed to the extraction electrodes 9 on both ends of the second metal wiring 5 and the extraction electrodes 38 of the third metal wiring 31.

FIG. 7 shows an equivalent circuit of the noise filter by the means 5. 3 is the first metal wiring, 5 is the second metal wiring, 15 is the distributed capacitance formed between the first metal wiring 3 and the second metal wiring 5, and 36 is the second metal wiring 5 and The distributed capacitance formed between the three metal wirings 31, 20 is the first metal wiring 3, the second metal wiring 5, and the third metal wiring 3
1 has an inductance, 32 has a second metal wiring,
Reference numeral 9 is an extraction electrode at both ends of the second metal wiring 5, and 38 is an extraction electrode of the third metal wiring 31.

As is apparent from this equivalent circuit diagram, according to the means 5, the distributed capacitance 15 formed between the first metal wiring 3 and the second metal wiring 5, the second metal wiring 5, and the second metal wiring 5 are formed. The distributed capacitance 36 formed between the three metal wirings 31 and the inductance of the spirally formed first metal wiring 3, second metal wiring 5, and third metal wiring 31 have a distributed constant type. Low pass filter is formed.

With the above structure, the built-in capacitance is formed between the first metal wiring and the second metal wiring, and the built-in capacitance is formed between the second metal wiring and the third metal wiring. Since it is determined by the sum of the above, a noise filter having a higher capacity than the conventional one can be made as in the case of the means 1, and the electrostatic withstand capability is also improved.

Further, according to the means 5, the noise that has entered the second metal wiring (signal line) is transmitted to the first metal wiring through the distributed capacitance formed between the first metal wiring and the second metal wiring. In addition to the route to escape to the metal wiring (ground) (equivalent to the conventional route to escape noise, referred to as route 1), another noise is introduced into the second metal wiring (signal line). And the third
A path (referred to as path 3) that escapes to the third metal wire (ground) via the distributed capacitance formed between the metal wires is formed, and the frequency attenuation characteristic is improved similarly to the means 1.

Here, in the means 5, since the resistance in the path 3 is determined by the wiring resistance of the metal wiring, its equivalent resistance is 10
If Ω and C = 100 pF, then τ = CR = 1 / f and f =
It becomes 1 GHz, so that noise up to 1 GHz can be removed, and there is an effect that the frequency attenuation characteristic is further improved as compared with the means 1 to 4. Also, the equivalent resistance can be lowered to about several Ω.

Next, a method for greatly improving electrostatic withstand capability will be described.

First, an embodiment of the means 7 according to the present invention will be described.

FIG. 8 shows a sectional view of the noise filter by means 7. Reference numeral 25 denotes a region of a conductivity type different from the conductivity type of the semiconductor substrate 1, and the others are the same as those in FIG. In the means 1, the semiconductor substrate 1 will be described as p-type and 25 as n-type.

In the process step, the first insulating film 6 is formed on the semiconductor substrate 1 (p-type), and then a part of the first insulating film 6 is removed by etching. Next, a region 25 (n type) having a conductivity type different from the conductivity type of the semiconductor substrate 1 is formed in the portion where the first insulating film 6 is removed by diffusion or ion implantation. Next, the first insulating film 6
The first metal wiring 3 is formed in a spiral shape on the above, and a part of the first metal wiring 3 is brought into contact with 25. The rest is the same as the means 1 and will be omitted.

After the process steps are completed, the lead-out electrodes 9 of the second metal wiring 5 and the lead-out electrodes 8 at both ends of the first metal wiring 3 are bonded.

FIG. 9 shows an equivalent circuit of the noise filter by the means 7. It is the same as FIG. 2 except that a pn junction diode 26 formed at the junction surface of the semiconductor substrate 1 (p-type) and a region 25 (n-type) of a conductivity type different from the conductivity type of the semiconductor substrate 1 is added.

As is apparent from this equivalent circuit diagram, the means 7 forms the same distributed constant type low-pass filter as the means 1, and further the protection diode against electrostatic breakdown is formed.

With the structure described above, the electrostatic withstand capability can be increased without deteriorating the frequency attenuation characteristic as compared with the case without the protection diode. For example, 1 without protection diode
The junction capacitance of the protection diode of the noise filter with the protection diode is 6 for the 00pF noise filter.
When the capacitance is pF, the built-in capacitance is 106 pF, and the capacitance is apparently increased by 6%, but at this level, the frequency attenuation characteristic is hardly deteriorated.

Since the protective diode is provided, the first
Value of a second insulating film that insulates the second metal wiring from the first metal wiring and a first insulating layer that insulates the semiconductor substrate from the first metal wiring
The film thickness value of the insulating film can be made smaller than that without the protection diode, and a noise filter having a higher capacity than that without the protection diode can be made, and the chip size can be reduced accordingly. Therefore, although the number of process steps is increased by about 10% from the conventional method, the total cost can be reduced to the same level as the conventional method by shrinking the chip.

When a pn junction diode is added, it is possible to operate within the range of the threshold voltage of the forward characteristic to the break voltage of the backward characteristic, and the break voltage of the backward characteristic can be changed in the process step. The voltage range used can be adjusted by adjusting.

Next, an embodiment of the means 8 according to the present invention will be described.

FIG. 10 shows a surface view of the noise filter by means 8 (up to the step of forming the first metal wiring).
1 is a semiconductor substrate, 3 is a first metal wiring, 25 is a region of a conductivity type different from that of the semiconductor substrate 1, 81 is an extraction electrode of an input terminal of the first metal wiring, and 82 is a first metal wiring. Is an extraction electrode of the output terminal of.

FIG. 11 shows an equivalent circuit of the noise filter by the means 8. Reference numeral 26 denotes a semiconductor substrate 1 (p-type) and a region 25 having a conductivity type different from that of the semiconductor substrate 1.
A pn junction diode formed by an (n-type) junction surface, wherein the pn junction diode formed in the process step is formed near the extraction electrode of the input terminal of the first metal wiring (near the center of the chip). Except that it is the same as the means 7.

In the case of the means 8, the pn junction diode formed in the process step is formed near the center of the chip.
Therefore, the static electricity that has entered the signal line is evenly distributed toward the semiconductor substrate through the pn junction diode, which is advantageous in that the static electricity resistance is maximized.

Next, an embodiment of the means 9 according to the present invention will be described.

FIG. 12 shows a surface view of the noise filter by means 9 (up to the step of forming the first metal wiring).
It is the same as FIG. 10 except that the formation location of 25 is different.

FIG. 13 shows an equivalent circuit of the noise filter by the means 9. It is the same as FIG. 11 except that the position of the pn junction diode 26 is different.

In the case of the means 9, the pn junction diode formed in the process step is formed in the vicinity of the extraction electrode of the output terminal of the first metal wiring (corner of the chip). When the noise filter is viewed from the input terminal, the junction capacitance of the diode is added near the output terminal. Therefore, in this structure, the final stage of the circuit is the circuit in which the inductance L and the capacitance C are connected in cascade. It is needless to say that the junction capacitance is connected in series, the number of cascaded LC stages is increased, and the electrostatic withstand capability is increased, and the frequency attenuation characteristic is sharper and better.

Further, like the means 10, the means 7 may have a structure which simultaneously satisfies the means 8 and 9.

Further, like the means 12, a part of the second metal wiring is different from the first metal wiring (different from the signal line) so that the second metal wiring and the semiconductor substrate have the same potential (ground). ) Or may be a structure which is in direct contact with the semiconductor substrate.

Further, like the means 11 and 13, a well may be provided on the surface of the semiconductor substrate to reduce the sheet resistance on the surface. In this case, the break voltage is lower than that in the case where there is no well, so there is an advantage that the electrostatic withstand capability is further increased.

Further, like the means 14, the pn junction diode formed in the process step may be partially or entirely formed in a spiral shape under the first metal wiring. In this case, increasing the diode area increases the electrostatic withstand capability.

It is needless to say that the embodiments described so far are not limited to this and can be modified without departing from the spirit of the present invention.

[0083]

The noise filter according to the present invention is formed between the semiconductor substrate and the first metal wiring and the distributed capacitance in which the built-in capacitance is formed between the first metal wiring and the second metal wiring. Since it is determined by the sum of distributed capacities, the number of process steps is almost the same as the conventional one, and a noise filter having a higher capacity than the conventional one can be manufactured.

Further, static electricity from the outside is divided into a distributed capacitance formed between the first metal wiring and the second metal wiring and a distributed capacitance formed between the semiconductor substrate and the first metal wiring. Since it is absorbed as a result, there is an effect that the electrostatic withstand capability is improved as compared with the conventional case.

From the first metal wiring (signal line) to the first
In addition to the path (equivalent to the conventional path through which noise escapes) to the second metal wire (ground) via the distributed capacitance formed between the second metal wire and the second metal wire, A path for escaping from the metal wiring to the semiconductor substrate (ground) via the distributed capacitance formed between the first metal wiring and the semiconductor substrate, there are a plurality of paths for noise to escape, and the frequency attenuation characteristic is improved. .

Further, even if the metal wiring has three layers, the same effect as described above can be obtained.

Further, by forming a protection diode against electrostatic breakdown between the first metal wiring and the semiconductor substrate in the process step, the electrostatic withstand capability can be increased without deteriorating the frequency attenuation characteristic as compared with the noise filter without the diode. You can

Further, when the protective diode is provided, it is possible to make a noise filter having a higher capacity than when the protective diode is not provided, and the chip size can be reduced accordingly.

[Brief description of drawings]

FIG. 1 is a sectional view of a noise filter according to means 1.

FIG. 2 is a diagram of an equivalent circuit of the noise filter according to means 1.

FIG. 3 is a cross-sectional view of a noise filter according to means 3.

FIG. 4 is a diagram of an equivalent circuit of the noise filter according to means 3.

FIG. 5 is a sectional view of the noise filter according to means 4.

FIG. 6 is a sectional view of a noise filter according to means 5.

FIG. 7 is a diagram of an equivalent circuit of the noise filter according to means 5.

FIG. 8 is a cross-sectional view of a noise filter according to means 7.

FIG. 9 is a diagram of an equivalent circuit of the noise filter according to means 7.

FIG. 10 is a surface view of a noise filter according to means 8.

FIG. 11 is a diagram of an equivalent circuit of the noise filter according to means 8.

FIG. 12 is a surface view of a noise filter according to means 9.

FIG. 13 is a diagram of an equivalent circuit of the noise filter according to means 9.

FIG. 14 is a cross-sectional view of a conventional noise filter.

FIG. 15 is a diagram of an equivalent circuit of a conventional noise filter.

[Explanation of symbols]

1. ． ． ． Semiconductor substrate 2. ． ． ． Insulating film 3. ． ． ． First metal wiring 5. ． ． ． Second metal wiring 6. ． ． ． First insulating film 7. ． ． ． Second insulating film 8. ． ． ． Extraction electrode of first metal wiring 9. ． ． ． Extraction electrode of second metal wiring 10. ． ． ． Conductive paste 11. ． ． ． First metal wiring 12. ． ． ． Lead frame 13. ． ． ． Bonding wire 14. ． ． ． Well region 15. ． ． ． 15. A distributed capacitance formed between the first metal wiring and the second metal wiring 16. ． ． ． The distributed capacitance formed between the first metal wiring and the semiconductor substrate 20. ． ． ． Inductors owned by the first metal wiring, the second metal wiring, and the third metal wiring 25. ． ． ． 26. A region of a conductivity type different from the conductivity type of the semiconductor substrate 26. ． ． ． pn junction diode 30. ． ． ． Third insulating film 31. ． ． ． Third metal wiring 32. ． ． ． Second metal wiring 36. ． ． ． Distributed capacitance formed between the second metal wiring and the third metal wiring 38. ． ． ． Third metal wiring extraction electrode 81. ． ． ． Extraction electrode of input terminal of first metal wiring 82. ． ． ． Extraction electrode of output terminal of first metal wiring

Claims (14)

[Claims] A first insulating film formed on the semiconductor substrate via a first insulating film;
Forming a metal wiring in a spiral shape, forming a second metal wiring spirally on the first metal wiring via a second insulating film, and forming the first metal wiring as a signal. Where the lead electrode of the second metal wiring and the semiconductor substrate are bonded with a conductive paste so that the second metal wiring and the semiconductor substrate have the same potential (ground) as a wire. The noise filter is characterized in that the lead frame of is connected with a bonding wire. 2. The noise filter according to claim 1, wherein the sheet resistance of the surface of the semiconductor substrate is reduced. 3. A first insulating film on a semiconductor substrate via a first insulating film.
Forming a metal wiring in a spiral shape, forming a second metal wiring spirally on the first metal wiring via a second insulating film, and forming the first metal wiring as a signal. Part of the second metal wiring is different from the first metal wiring (different from the signal line) so that the second metal wiring and the semiconductor substrate have the same potential (ground). A noise filter, which is in direct contact with the semiconductor substrate through or directly. 4. The noise filter according to claim 3, wherein the sheet resistance of the surface of the semiconductor substrate is reduced. 5. A first insulating film is formed on the semiconductor substrate with a first insulating film interposed therebetween.
Forming a metal wiring in a spiral shape, and forming a second metal wiring in a spiral shape on the first metal wiring via a second insulating film, and forming the second metal wiring on the second metal wiring. A third metal wiring is spirally opposed to the first metal wiring via a third insulating film, and the second metal wiring is operated as a signal line, and the first metal wiring and the third metal wiring are formed. So that they have the same potential (ground), a part of the third metal wiring is either directly connected to the first metal wiring through the second metal wiring (different from the signal line) or directly. A noise filter that is characterized by 6. The noise filter according to claim 5, wherein the roles of the signal line and ground are exchanged. 7. A first insulating film is formed on a semiconductor substrate via a first insulating film.
Forming a metal wiring in a spiral shape, forming a second metal wiring spirally on the first metal wiring via a second insulating film, and forming the first metal wiring as a signal. Where the lead electrode of the second metal wiring and the semiconductor substrate are bonded with a conductive paste so that the second metal wiring and the semiconductor substrate have the same potential (ground) as a wire. And a lead frame of the semiconductor substrate are connected by a bonding wire, and a region of a conductivity type different from the conductivity type of the semiconductor substrate (referred to as region 1) is formed on a part of the surface of the semiconductor substrate, A noise filter, wherein a part of the metal wiring is in direct contact with the region 1. 8. The noise filter according to claim 7, wherein the extraction electrode of the second metal wiring (ground) is formed inside the spiral, and the extraction electrode of the input terminal of the first metal wiring (signal line) is formed. Is formed inside the spiral,
A noise filter, wherein the extraction electrode of the output terminal is formed outside the spiral, and the region 1 is formed in the vicinity of the extraction electrode of the input terminal. 9. The noise filter according to claim 7, wherein the extraction electrode of the second metal wiring (ground) is formed inside the spiral, and the extraction electrode of the input terminal of the first metal wiring (signal line) is formed. Is formed inside the spiral,
A noise filter, wherein the extraction electrode of the output terminal is formed outside the spiral, and the region 1 is formed in the vicinity of the extraction electrode of the output terminal. 10. A noise filter according to claim 7, wherein the contents of claims 8 and 9 are satisfied at the same time. 11. A noise filter according to claim 7, wherein the sheet resistance of the surface of the semiconductor substrate is reduced. 12. A first metal wiring is spirally formed on a semiconductor substrate via a first insulating film, and a second metal is formed on the first metal wiring via a second insulating film. Wirings are formed so as to face each other on a spiral, and the first metal wiring is operated as a signal line so that the second metal wiring and the semiconductor substrate have the same potential (ground), A part of the wiring is in contact with the semiconductor substrate via a first metal wiring (different from the signal line) or directly, and a part of the surface of the semiconductor substrate is different from the conductivity type of the semiconductor substrate. A noise filter, wherein regions of different conductivity types (referred to as regions 1) are formed, and a part of the first metal wiring (signal line) is in direct contact with the region 1. 13. A noise filter according to claim 12, wherein the sheet resistance of the surface of the semiconductor substrate is lowered. 14. The noise filter according to claim 7, wherein the region 1 is formed in a spiral shape partially or entirely under the first metal wiring.