JPS612361A - Electrostatic breakdown preventive element - Google Patents

Abstract

PURPOSE:To transmit a signal having a high-frequency component by comparatively simple constitution by forming a resistor constituting an electrostatic breakdown preventive element onto an oxide film on the surface of a semiconductor. CONSTITUTION:Large line resistance formed by each adding resistors R30 by one layer wiring 30 sections, wiring resistors 32 by second layer wiring 32 sections and wiring resistors RH by a plurality of through-holes TH in series along a zigzag path is shaped. The large line resistance is interposed in series between a protective input in and a protective output out as a resistor R. Since the resistor R is formed onto an oxide film on the surface of a semiconductor, P-N junction capacitance is not parasitized. Accordingly, even signals having high-frequency components can be transmitted positively without attenuation or delay.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a technique for preventing electrostatic damage and a technique particularly effective when applied to protecting internal circuits of semiconductor integrated circuit devices from high voltage surges such as static electricity. for example,
The present invention relates to a technique effective for use in an input protection circuit of a semiconductor integrated circuit device in which a Bipolari element is formed.

[Background technology]

For example, in a semiconductor integrated circuit device in which a circuit is formed using bipolar type elements, in order to protect the bipolar type elements from electrostatic damage, there is a gap between the terminal band portion connected to the external terminal bin and the input side of the internal circuit. It is necessary to provide an electrostatic breakdown prevention element to absorb or bypass overvoltage. In this case, it is not known which polarity (positive or negative) high voltage surge will be applied to the protection input side. Therefore,
The electrostatic damage prevention device described above must be capable of providing protection against surges of either positive or negative polarity.

As an example of an electrostatic breakdown prevention element that can provide protection against surges of either positive or negative polarity,
There is an electrostatic breakdown prevention element disclosed in Japanese Patent No. 21838.

FIG. 1 shows the cross-sectional state and planar layout state of the electrostatic breakdown prevention element disclosed in Japanese Patent Publication No. 53-21838, together with an equivalent circuit, and FIG. 1al shows the cross-sectional state of the element. 1bl shows an equivalent circuit of the element.

The electrostatic breakdown prevention element shown in FIG.
are selectively formed, and further, a first conductivity type region 18 is selectively formed within the second conductivity type region 16. As a result, as shown in the same figure, two transistor portions Ql and Q2 having the second conductivity type region 16 as a common base region are formed. Further, both transistor portions Q1. The first conductivity type regions 18 and 18 on each side of Q2 are connected to each other via a diffusion layer resistance R. and,
The first conductivity type region 18 of one transistor section Q1 is connected to the protection input in, and the first conductivity type region 18 of the other transistor section Q2 is connected to the protection output out.

Here, as the first conductivity type semiconductor substrate 14, la
As shown in FIG. 1, an n-type epitaxial layer formed on a p-type silicon semiconductor substrate 10 is used. An n+ type buried layer 12 is formed in an island shape under this epitaxial layer (IIO).

Further, the second conductivity type region 16 uses a p-type base diffusion layer formed by selectively diffusing p-type conductive impurities such as boron into the n-type epitaxial layer (141). In the first conductivity type region 18°18, the above p
An n+ type emitter diffusion layer formed by selecting and diffusing an n type conductive impurity such as phosphorus into the type base diffusion layer (161) is used.Then, this n+ type emitter diffusion layer a barrel, α rapid surface oxidation is used. Apertures H, H are provided in the membrane 20, and the apertures H
, H is formed by patterning the wiring 30 in the portion including the electrodes. Furthermore, the diffusion layer resistor R uses an n+ type emitter diffusion layer 18a which is diffused together with the first conductivity type region 18.18.

FIG. 2 shows the operation of the electrostatic breakdown prevention element described above.

First, as shown in FIG. 1al, when a positive high voltage surge +■srg enters the protection input in, the first conductivity type region, that is, the n+ type emitter diffusion layer 18°18 becomes the collector of the transistor parts Ql and Q2. In addition to functioning as
The first conductive type semiconductor substrate, that is, the n-type epitaxial layer 14 forms two transistor parts Q1. It comes to function as a common emitter for Q2. As a result, a current flows in the direction of the arrow from the protection input in toward the power supply Vcc, and the positive surge +Vsrg is voltage clamped, and as a result, a circuit element such as a bipolar transistor connected to the protection output out side will be protected from.

Next, as shown in FIG. In addition to functioning as an emitter,
The first conductive type semiconductor body, that is, the n-type epitaxial layer 14 functions as a common collector of the two transistor parts Ql and Q2. As a result, the power supply Vc
A current flows in the direction of the arrow from c toward the protection input in, and the negative surge -Vsrg is voltage clamped, thereby protecting the circuit elements connected to the protection output out side from the negative surge -Vsrg. It becomes like this.

As described above, an electrostatic breakdown prevention element that works effectively against surges of either positive or negative polarity is configured in one active region.

However, in such a technique, first, the resistance R is n+
Since it is constituted by the type emitter diffusion layer 18a,
A pn junction capacitance is parasitic between the n+ type emitter diffusion layer 18 and the second conductivity type region, that is, the p type base diffusion layer 16, so that signals with high frequency components are input to the protected input.
It became clear that the data could not be reliably transmitted from the protection output side to the protection output OUT side, making it difficult to transmit digital signals that change at high speed without delay. It has also been found that in order to form the diffusion layer 18a, an elongated and irregularly shaped layout pattern is required in order to obtain a predetermined resistance value, which increases the element area.

[Purpose of the invention]

An object of the present invention is to provide an electrostatic breakdown prevention element as described above, which has a relatively simple structure, does not impede the transmission of signals with high frequency components, and can reduce the required layout area. It provides technology that allows it to be made smaller.

The above and other objects and novel features of the present invention will be apparent from the description of the present specification and the accompanying drawings.

[Summary of the invention]

A brief overview of typical inventions disclosed in this application is as follows.

In other words, by forming the resistor that constitutes the electrostatic breakdown prevention element on the oxide film on the semiconductor surface, it is possible to reduce the capacitance and prevent the transmission of signals with high frequency components, and also to This achieves the purpose of reducing the layout area.

〔Example〕

Hereinafter, typical embodiments of the present invention will be described with reference to the drawings.

In the drawings, the same reference numerals indicate the same or corresponding parts.

FIG. 3 shows the cross-sectional state and planar layout state of an electrostatic breakdown prevention element according to an embodiment of the present invention, together with an equivalent circuit, and FIG. 1al shows the cross-sectional state of the element.
In the same figure, fbl shows an equivalent circuit of the element, and in the same figure (cl shows the planar layout state of the element, respectively).

The electrostatic breakdown prevention element shown in FIG.
are selectively formed, and further a first conductivity type region 18.18 is selectively formed within the second conductivity type region 16. As a result, as shown in FIG. The first conductivity type regions 18 and 18 are connected to each other via a resistor R.The first conductivity type region 18 of one transistor section Q1 is connected to the protection input in, and the other transistor section Q1 is connected to the protection input in.
The two first conductivity type regions 18 are configured to be connected to the protection output out.

As the first conductive type semiconductor substrate 14, an n-type epitaxial layer formed on a p-type silicon semiconductor substrate 10 is used, as shown in lal. An n+ type buried layer 12 is formed in the shape of an island below this epitaxial layer σ(a). Further, the second conductivity type region 16 uses a p-type base diffusion layer formed by selectively diffusing p-type conductive impurities such as boron into the n-temperature epitaxial layer aa.

Further, in the first conductivity type region 18.18, an n+ type emitter diffusion layer formed by selectively diffusing an n type conductive impurity such as phosphorus into the p type base diffusion layer (1119) is used. , holes H, H are provided in this n+ type emitter diffusion layer α barrel side quick stop surface oxide film 20;
Wiring 30.32 patterned in the H-containing part
The electrodes are taken out.

Here, the resistor R is formed on an oxide film 20 formed on the semiconductor surface, as shown in FIG. 3 1a+.

To explain in more detail, this embodiment is constructed using a multilayer wiring structure. That is, first, the first layer wiring 30 is formed by patterning on the first layer oxide film 20. Next, a second layer of oxide film 22 is formed on this first layer of wiring 30, and a second layer of wiring 32 is formed on this second layer of oxide film 22 by patterning. Furthermore, the through hole TH connecting the first layer wiring 30 and the second layer wiring 32 is connected to the two first conductive regions, that is, n
A plurality of them are provided between the + type emitter diffusion layers 18 and 18. And these multiple through holes TH
As a result, an electric path is formed that alternately passes through the first-layer wiring 30 and the second-layer wiring 32 and follows a zigzag path as shown in FIG. The electric path formed in this way includes, as shown in FIG. 3, 1b+.
A large line resistance is generated by adding in series the resistance R30 due to the wiring 300 portion of the first layer, the wiring resistance 32 due to the wiring 320 portion of the second layer, and the wiring resistance RH due to the plurality of through holes TH.

This large line resistance acts as the resistance R, and the protection input in
and the protection output out in series.

Now, the characteristic feature of the electrostatic breakdown prevention element constructed as described above is that, first, since the resistor R is formed on the oxide film on the semiconductor surface, there is no parasitic pn junction capacitance. be. This makes it possible to reliably transmit signals with high frequency components without attenuation or delay. This allows for example Bip
When used as an electrostatic breakdown prevention element for an internal circuit in which an olar logic circuit is formed, it can function satisfactorily as a protection element without impairing the high-speed performance of the internal circuit.

Further, the through hole TH used to form the resistor R can easily have a high resistance by reducing the diameter of the through hole. Furthermore, since the through-hole resistor RH is formed in the vertical direction, it requires almost no layout area. This also has the excellent effect that the layout area required to form the element can be significantly reduced.

Furthermore, it should be noted that in the above embodiment, the n''W
The emitter diffusion layers 18, 18 are each formed as an independent island. This results in the so-called washed
This makes it possible to adopt an emitter structure. In other words, the hole H for taking out the electrode can be formed in a self-aligned manner (washed emitter method) by rare etching of the surface oxide film 2o, and this has the advantage that miniaturization of the device can be easily achieved. will be obtained at the same time.

FIG. 4 shows the operation of the electrostatic breakdown prevention element described above.

First, as shown in FIG. 1al, when a positive high voltage surge +Vsrg is input to the protection input in, the first conductivity type region, that is, the n+ type emitter diffusion layer 18°18 functions as the collector of the transistor parts Ql and Q2. At the same time, the first conductivity type semiconductor substrate, that is, the n'''' type epitaxial layer 14 comes to function as a common emitter of the two transistor parts Ql and Q2. As a result, a current flows in the direction of the arrow from the protection input in toward the power supply Vcc, and the positive surge +Vsrg is voltage clamped, thereby protecting the circuit elements connected to the protection output out side from the positive surge +Vsrg. become.

Next, as shown in FIG. The first conductivity type semiconductor substrate, that is, the n-type epitaxial layer 1 serves as an emitter.
4 is the two transistor section Q1. It will now function as a common collector for Q2. As a result, a current flows in the direction of the arrow from the power supply Vcc toward the protection input in, and the voltage of the negative surge -Vsrg is clamped.
It will be protected from rg.

As described above, an electrostatic breakdown prevention element is constructed that is effective against surges of either positive or negative polarity, has excellent signal transmission characteristics, and is suitable for miniaturization.

As for the materials of the wirings 30 and 32, it is appropriate that the first layer is made of polycrystalline silicon or polycide, and the second layer is made of aluminum or other metal.

〔effect〕

(1) By forming the resistor constituting the electrostatic breakdown prevention element on the oxide film on the semiconductor surface, it is possible to have a relatively simple structure and avoid interfering with the transmission of signals with high frequency components. This effect can be obtained.

(2) Furthermore, by configuring the above-mentioned resistor using a through-hole wiring resistor, an effect can be obtained in that the required layout area can be reduced.

(3) Since both positive and negative surges are clamped, they do not affect the internal circuit.

Although the invention made by the present inventor has been specifically explained above based on Examples, this invention is not limited to the above Examples (although it is possible to make various changes without departing from the gist of the invention). For example, the above resistance R
may be composed only of a thin film resistor formed on an oxide film on the semiconductor surface. Furthermore, the same effect can be obtained even if the n++ diffused layer 18 on the internal circuit connection side of the electrostatic breakdown prevention element is not formed but is formed as shown in FIG. Further, the arrangement of the resistors formed by through holes is not limited to the above embodiment, and may be arranged in a figure 8 pattern around the input and output electrodes.

In this example, since a resistor is formed around the electrode, an electrostatic breakdown prevention element with a smaller element area than the previous example can be formed, and the degree of integration can be improved.

[Application field]

In the above explanation, the invention made by the present inventor was mainly applied to the electrostatic damage prevention technology for 13ipolar type semiconductor integrated circuits, which is the background field of application, but the invention is not limited to this. For example, it can be applied to overvoltage protection prevention technology for MO8 type semiconductor integrated circuits or analog circuits.

A diagram showing a cross-sectional state and a planar layout state of an electrostatic breakdown prevention element according to an embodiment of the third invention, together with an equivalent circuit, and a planar layout state together with an equivalent circuit; FIG. 5 is a diagram showing the planar layout of an electrostatic breakdown prevention device according to another embodiment of the present invention.

DESCRIPTION OF SYMBOLS 10...p-type semiconductor substrate, 12...n+ buried layer, 14...first conductivity type semiconductor substrate (n'''' epitaxial layer), 16...second conductivity type region (p type diffusion layer)
, 18...first conductivity type region (n+ type scattering layer, 30...
...1st layer wiring, 32...2nd layer wiring, H...hole for electrode extraction, TH...through hole, in...protection input, out...protection output, Ql, Q2 ...Transistor part, R...Resistance, R30...Resistance due to first layer wiring, R32...Resistance due to second layer wiring,
RH...Through hole wiring resistance, Vcc...Power supply,
-Vsrg...Negative surge power supply, +Vsrg...
Positive surge power.

Figure 1 (d)

Claims (1)

[Claims] 1. By selectively forming a second conductivity type region in the first conductivity type semiconductor substrate, and further selectively forming a first conductivity type region within the second conductivity type region, Two transistor parts are formed having the second conductivity type region as a common base region, and the first conductivity type regions of each one of both transistor parts are connected to each other via a resistor, and the An electrostatic breakdown prevention element configured to use a first conductivity type region as a protection input and a first conductivity type region of the other transistor section as a protection output, the resistor being arranged on an oxide film on a semiconductor surface. An electrostatic breakdown prevention element characterized by the following: 2. The electrostatic breakdown prevention element according to claim 1, wherein the resistor is constructed using a through-hole wiring resistor.