JPH0563147A - Integrated circuit and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide an integrated circuit of a simple structure in which an RC filter occupying a smaller space is formed to save the active areas on a substrate. CONSTITUTION:An RC filter circuit is composed of p-type diffused resistors 25-28 and parasitic capacitors 29-32 in the resistors.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor integrated circuit having an RC filter circuit including a resistance element and a capacitance element, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, as an RC filter circuit, one having a circuit diagram shown in FIG. 12 is known. 1 in the figure
Is an input terminal, 2 is a resistance element, 3 is a capacitive element, and 4 is an output terminal. This RC filter circuit constitutes a so-called low pass filter.

Conventionally, when this RC filter circuit is built in a semiconductor integrated circuit, FIG. 13 shows a sectional view thereof (see FIG. 14).
(A cross-sectional view taken along line AA in FIG. 14) and FIG. 14 is a plan view thereof. In the figure, 5 is a P-type silicon substrate, 6 and 7 are N ⁺ buried layers, 8 is an N ⁻ epitaxial layer, 9 is an N ⁺ contact layer, and 10 is an element isolation region.

Further, 12 and 13 are P type diffusion layers,
The type diffusion layer 12 is the resistance element 2 in FIG. The junction capacitance 14 between the P type diffusion layer 13 and the N ⁻ epitaxial layer 8 is the capacitance element 3 in FIG. In addition, 15 is a SiO ₂ layer which forms an insulating layer, 16, 17,
18 is electrode wiring made of aluminum, 19, 20, 2
Reference numerals 1 and 22 are contact holes.

[0005]

When the RC filter circuit whose circuit diagram is shown in FIG. 12 is constructed as shown in the sectional view of FIG. 13 and the plan view of FIG. 14, the capacitive element is separated from the resistive element. Since they are formed independently, there is a problem that the structure is complicated, the required area becomes large, and the element formation surface of the semiconductor integrated circuit cannot be effectively used.

In view of the above points, the present invention provides a semiconductor integrated circuit having a simple structure and a built-in RC filter circuit which requires a small area, and makes it possible to effectively use an element formation surface, and a manufacturing method thereof. The purpose is to do.

[0007]

A first aspect of the present invention relates to a semiconductor integrated circuit, wherein a diffusion resistance formed in a semiconductor layer is used as a resistance element, and a parasitic capacitance parasitic on the diffusion resistance, that is, , An RC filter circuit having a junction capacitance between the diffusion resistor and the semiconductor layer as a capacitive element is built in.

A second aspect of the present invention relates to a semiconductor integrated circuit, wherein a plurality of diffused resistors formed in a semiconductor layer are used as resistance elements, and parasitic capacitance parasitic on the plurality of diffused resistors is used as a capacitive element. The built-in RC filter circuit is configured.

A third aspect of the present invention relates to a semiconductor integrated circuit, wherein diffusion resistances formed in a plurality of electrically separated semiconductor layers are used as resistance elements and are formed in the plurality of semiconductor layers. In addition, all or part of the parasitic capacitance parasitic on the diffused resistor is built in and configured as an RC filter circuit.

A fourth aspect of the present invention relates to a method of manufacturing a semiconductor integrated circuit, which comprises forming a plurality of diffusion resistors in a semiconductor layer and selecting a connection of wirings connecting the plurality of diffusion resistors. An RC in which all or part of the plurality of diffused resistors are resistance elements and all or part of parasitic capacitances parasitic on the plurality of diffused resistors are capacitor elements.
The step of forming a filter circuit is included.

A fifth aspect of the present invention relates to a method for manufacturing a semiconductor integrated circuit, wherein diffusion resistance is formed in a plurality of electrically isolated semiconductor layers, and the semiconductors of the plurality of semiconductor layers are individually formed. Connect the layer to the input source, or
By selecting whether to connect to a fixed potential, the diffusion resistance formed in the plurality of electrically separated semiconductor layers is used as a resistance element, and parasitic capacitance parasitic on the diffusion resistance formed in the plurality of semiconductor layers. The method includes the step of forming an RC filter circuit configured by using all or part of the above as a capacitive element.

[0012]

According to the present invention, since the parasitic capacitance of the diffused resistor is used as the capacitive element of the RC filter circuit, it is not necessary to form a PN junction for forming the capacitive element separately from the diffused resistor. Therefore, R has a simple structure and a small area.
A C filter circuit can be obtained, and the element formation surface can be effectively used. According to the second to fifth aspects, the band of the built-in RC filter circuit can be easily set and changed.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The first embodiment of the present invention will be described below with reference to FIGS.
An example, a second example and an application example will be described.

First Embodiment FIG. 1 to FIG. 5 FIG. 1 is a sectional view (a sectional view taken along the line BB of FIG. 2) showing an RC filter circuit incorporated in the first embodiment of the present invention. Two
FIG. 3 is a plan view showing an RC filter circuit also incorporated in the first embodiment of the present invention.

In the figure, 23 is a P-type silicon substrate and 24 is N.
^- epitaxial layer, 25 to 28 diffused resistor, 29-32 parasitic capacitance of the diffusion resistance 25-28 consisting of P-type diffusion layer, i.e., the diffusion resistor 25 to 28 and the N ^- junction capacitance between the epitaxial layer 24, 33 Insulating SiO ₂ layer, 34
˜38 are electrode wirings made of aluminum, 39 to 46 are contact holes, 47 is an input terminal, and 48 is an output terminal.

The first embodiment constitutes an RC filter circuit as shown in the circuit diagram of FIG. 3, in which 49 to 52 are resistance elements composed of diffused resistors 25 to 28, respectively. 53 to 56 are diffused resistors 25, respectively.
28 is a capacitive element including parasitic capacitances 29 to 32.

As described above, according to the first embodiment as well, R
Although a C filter circuit can be configured, according to the first embodiment, the parasitic capacitances 29 to 3 of the diffused resistors 25 to 28 are included.
Since 2 is a capacitive element, it is not necessary to form a PN junction for forming a capacitive element separately from the diffused resistors 25 to 28. Therefore, an RC filter circuit having a simple structure and a small area can be obtained, and the element formation surface of the semiconductor integrated circuit can be effectively used.

According to the first embodiment, the band characteristic can be easily changed by changing the wiring. For example, in FIG. 4, the wiring 36 shown in FIG.
5 is an example in which the wiring 37 is connected to the wiring 37.

Further, FIG. 5 shows an example in which both the wiring 36 and the wiring 57 are provided in advance, and the wiring 36 or the wiring 57 is cut as necessary to obtain a desired band. Such cutting can be performed by a laser, but can also be performed in a mask process.

Second Embodiment ... FIGS. 6 to 8 FIG. 6 is a sectional view (a sectional view taken along the line CC of FIG. 7) showing an RC filter circuit incorporated in the second embodiment of the present invention. 7
FIG. 8 is a plan view showing an RC filter circuit incorporated in the second embodiment of the present invention.

In the figure, 58 is a P type silicon substrate, and 59 to 6
2 is an N ⁺ buried layer, 63 is an element isolation region, 64 to 67
Is an N ^- epitaxial layer isolated by the element isolation region 63, and 68 to 71 are N ⁺ contact layers.

Reference numerals 72 to 75 are diffusion resistors made of P type diffusion layers, 76 is a parasitic capacitance of the diffusion resistors 72, that is, a junction capacitance between the diffusion resistors 72 and the N ^- epitaxial layer 64, 77.
Is the parasitic capacitance of the diffused resistor 73, that is, the diffused resistor 73 and N ^−.
It is the junction capacitance with the epitaxial layer 65.

Reference numeral 78 is a parasitic capacitance of the diffusion resistor 74, that is, a junction capacitance between the P-type diffusion layer 74 and the N ⁻ epitaxial layer 66, and 79 is a parasitic capacitance of the diffusion resistor 75, that is, an N ⁻ epitaxial layer 67. It is the junction capacity. Further, 80 is a SiO ₂ layer forming an insulating layer, 81 to 87 are electrode wirings made of aluminum, 88 to 99 are contact holes, 100
Is an input terminal and 101 is an output terminal.

This second embodiment constitutes an RC filter circuit as shown in the circuit diagram of FIG.
Reference numerals 102 to 105 are resistance elements formed of diffused resistors 72 to 75, and reference numerals 106 to 109 are capacitive elements formed of parasitic capacitances 76 to 79 of the diffused resistors 72 to 75, respectively.

As described above, according to the second embodiment as well, R
Although a C filter circuit can be configured, according to the second embodiment, the parasitic capacitances 76 to 7 of the diffused resistors 72 to 75 are included.
Since 9 is a capacitive element, the diffusion resistors 102 to 105
It is not necessary to form a PN junction for forming a capacitive element separately from. Therefore, an RC filter circuit having a simple structure and a small area can be obtained, and the element formation surface of the semiconductor integrated circuit can be effectively used.

Here, according to the second embodiment, the capacitive elements 106 and 107 have the N of the PN junction forming them.
The side, that is, the N ⁻ epitaxial layers 64 and 65 have the same potential as the input terminal 100 via the electrode wiring 82. Therefore, these capacitive elements 106 and 107 are connected to the input terminal 1
It cannot be seen as a capacity from the 00 side. That is, in the second embodiment, the resistive elements 102 to 105 and the capacitive element 1 are
The RC filter circuit is composed of 08 and 109.

Therefore, according to the second embodiment, the electrode wirings 82 and 87 and the N ^- epitaxial layers 64-67 are formed.
By changing the manner of connection with the electrodes, for example, only the N ⁻ epitaxial layer 64 is connected to the electrode wiring 82, and the N ⁻ epitaxial layers 65 to 67 are connected to the electrode wiring 87. The characteristics can be obtained.

Application Example: FIGS. 9 to 11 FIG. 9 is an application example of the RC filter circuit incorporated in the present invention to an equalizer circuit. The equalizer circuit of FIG.
The feedback resistor 110 of the low pass filter circuit shown in FIG. 10 is replaced with the RC filter circuit 111 of the present invention.

9 and 10, 112 is an input terminal, 113 is an output terminal, 114 to 117 are resistors, and 1 is a resistor.
Reference numerals 18 and 119 denote npn transistors forming a differential pair transistor, 120 denotes an output npn transistor, and 12
Reference numerals 1 and 122 are capacitors, and 123 and 124 are constant current sources.

The low-pass filter circuit shown in FIG. 10 is a voltage follower type circuit in which the npn transistors 118 and 119 are in a balanced state when the voltage at the input terminal 112 and the voltage at the output terminal 113 become equal to each other.
When an AC signal is input to the input terminal 112, as shown in FIG.
As shown by the curve X, the AC signal is output to the output terminal 113 up to a certain frequency band.

Feedback resistor 11 of this low-pass filter circuit
When the present invention is used instead of 0, the characteristic of the RC filter circuit has the negative gain shown by the alternate long and short dash line Y in FIG.
In order to keep the npn transistors 118 and 119 in a balanced state, the output terminal voltage becomes high at a certain frequency. When this is illustrated, it becomes like the chain double-dashed line Z in FIG. 11, and the equalizer characteristic can be obtained.

The RC filter circuit incorporated in the present invention has a high pass and a band pass.
It is obvious that the present invention can be applied to an equalizer circuit having the above characteristics and various analog circuits.

[0033]

According to the present invention, since the parasitic capacitance of the diffused resistor is used as the capacitive element of the RC filter circuit, a PN junction for forming the capacitive element is formed separately from the diffused resistor which forms the resistive element. No need, simple to configure, and
An RC filter circuit having a small area can be obtained, and the element formation surface can be effectively used. In particular, according to the second to fifth inventions, the band of the built-in RC filter circuit can be easily set and changed.

[Brief description of drawings]

FIG. 1 is a sectional view showing an RC filter circuit incorporated in a first embodiment of the present invention.

FIG. 2 is a plan view showing an RC filter circuit incorporated in the first embodiment of the present invention.

FIG. 3 is an equivalent circuit diagram of an RC filter circuit incorporated in the first embodiment of the present invention.

FIG. 4 is a plan view for explaining an example of advantages of the RC filter circuit incorporated in the first embodiment of the present invention.

FIG. 5 is a plan view for explaining another example of the advantage of the RC filter circuit incorporated in the first embodiment of the present invention.

FIG. 6 is a sectional view showing an RC filter circuit incorporated in a second embodiment of the present invention.

FIG. 7 is a plan view showing an RC filter circuit incorporated in the second embodiment of the present invention.

FIG. 8 is an equivalent circuit diagram of an RC filter circuit incorporated in the second embodiment of the present invention.

FIG. 9 is a circuit diagram showing an application example of an RC filter circuit incorporated in the present invention to an equalizer circuit.

FIG. 10 is a circuit diagram showing an example of a low-pass filter circuit.

11 is a diagram showing characteristics and the like of the equalizer circuit shown in FIG.

FIG. 12 is a circuit diagram showing an RC filter circuit.

FIG. 13 is a cross-sectional view showing an RC filter circuit incorporated in a conventional semiconductor integrated circuit.

FIG. 14 is a plan view showing an RC filter circuit incorporated in a conventional semiconductor integrated circuit.

[Explanation of symbols]

23 P-type silicon substrate 24 N ^- Epitaxial layer 25-28 Diffusion resistance (P-type diffusion layer) 29-32 Diffusion resistance 25-28 parasitic capacitance 33 SiO ₂ layer 34-38 Electrode wiring made of aluminum 39-46 Contact hole 47 Input terminal 48 Output terminal

Claims (5)

[Claims] 1. A semiconductor integrated circuit comprising an RC filter circuit, wherein a diffusion resistance formed in a semiconductor layer is used as a resistance element, and a parasitic capacitance parasitic on the diffusion resistance is used as a capacitance element. 2. A semiconductor integrated circuit, comprising: an RC filter circuit having a plurality of diffusion resistors formed in a semiconductor layer as resistance elements, and a parasitic capacitance parasitic on the plurality of diffusion resistances as a capacitance element. circuit. 3. A diffusion element formed in a plurality of electrically isolated semiconductor layers is used as a resistance element, and all or a part of parasitic capacitance parasitic on the diffusion resistance formed in the plurality of semiconductor layers is a capacitance element. A semiconductor integrated circuit having an RC filter circuit configured as follows. 4. A plurality of diffused resistors are formed in a semiconductor layer, and by selecting connection of wirings connecting these diffused resistors, all or a part of the diffused resistors are made resistive elements, and the plurality of diffused resistors are formed. A method of manufacturing a semiconductor integrated circuit, comprising the step of forming an RC filter circuit in which all or part of parasitic capacitance parasitic on a diffusion resistance is formed as a capacitive element. 5. A diffusion resistor is formed in a plurality of electrically separated semiconductor layers, and each semiconductor layer of the plurality of semiconductor layers is selected to be connected to an input signal source or a fixed potential. As a result, the diffusion resistance formed in the plurality of electrically separated semiconductor layers is used as a resistance element, and all or part of the parasitic capacitance parasitic on the diffusion resistance formed in the plurality of semiconductor layers is changed to a capacitance element. And a step of forming an RC filter circuit configured as described above.