JPH08195477A - Semiconductor device - Google Patents

Abstract

PURPOSE: To prevent insulation breakage from occurring when a high surge voltage is applied to the electrode on a thin insulating film by arranging the semiconductor device such that the diode made right under it is biased reversely to the region right under the wiring of a semiconductor substrate when surge voltage is applied to the electrode. CONSTITUTION: An n layer 4 which has a dimension larger than the dimension of the electrode 3 on an insulating film 2 in any direction is made on the surface layer in the region where a pad electrode 3 on the surface is made and there is a fear of positive surge voltage adding, of the p-type silicon substrate 1 of an integrated circuit. Especially, a diode 11, which has a region pn junction including the region opposed to the electrode 3, is made within the silicon substrate 1 right under the insulating film 2. And, when surge voltage is applied to the electrode 3, this diode 11 is reversely biased. Hereby, the strength of the internal electric field of the insulating film 2 drops, and insulation breakage can be prevented from occurring in the insulating film 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device in which electrodes are provided on a semiconductor substrate via an insulating film.

[0002]

2. Description of the Related Art In a semiconductor integrated circuit, an electrode connected to an integrated element is provided on a semiconductor substrate via an insulating film. FIG. 3 shows an Al pad portion used for connecting such an Al wiring and an external circuit.
A pad electrode 3 is formed on a part of the wiring provided on the above via an insulating film 2 such as an oxide film.

[0003]

With the miniaturization of integrated circuits, the insulating film 2 on the surface is required to be thin.
For this reason, the breakdown voltage of the insulating film is lowered, and when a high surge voltage is applied to the electrode 3, dielectric breakdown may occur.
In order to prevent this destruction, it is conceivable to locally thicken the insulating film under the wiring, but this requires an additional process.

An object of the present invention is to solve the above problems and to provide a semiconductor device in which dielectric breakdown is prevented from occurring when a high surge voltage is applied to an electrode on a thin insulating film.

[0005]

In order to achieve the above object, the present invention provides a semiconductor device having an electrode provided on a semiconductor substrate via an insulating film, in which the electrode is provided in the semiconductor substrate immediately below the insulating film. Of the area including the area facing the
It is assumed that a diode having a junction is formed and that the diode is reverse biased when a surge voltage is applied to the electrode. A PN junction exists between the semiconductor substrate of the first conductivity type and the region of the second conductivity type formed on the surface layer of the substrate, or is formed on the semiconductor substrate of the first conductivity type and the surface layer of the substrate. Between the second conductivity type region and the second conductivity type region and between the second conductivity type region and the first conductivity type region formed in the surface layer of this region.

[0006]

When the surge voltage is applied to the electrode provided on the semiconductor substrate via the insulating film, the diode formed immediately below is reverse-biased, so that the electric field strength inside the insulating film is lowered. The dielectric breakdown of the insulating film is prevented. When the PN junction of this diode exists only between the substrate of the first conductivity type and the region of the second conductivity type formed in the surface layer thereof, the polarity of the surge voltage applied to the electrodes is limited, Further, a region of the first conductivity type is formed on the surface layer of the region of the second conductivity type to form PNP or N
When there are two diodes connected in anti-series by the PN structure, the insulating film is protected regardless of the polarity of the surge voltage.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to the drawings including the same parts in FIG.
In the embodiment shown in FIG. 1, the insulating film 2 is formed in any direction on the surface layer of the region where the pad electrode 3 is formed on the surface of the p-type silicon substrate 1 of the integrated circuit where a positive surge voltage may be applied. With a size larger than the size of the electrode 3 on the
Layer 4 has been formed. The n layer 4 is formed at the same time when the substrate 1 of the integrated circuit is subjected to the diffusion process of the n layer, or at the same time when the n type polycrystalline Si layer deposition process is performed. . However, it is necessary that the n layer is insulated from other layers in the substrate 1 or is floating. As shown in the figure, the diode 11 produced by the n-layer 4 and the P-substrate 1
On the other hand, the positive surge voltage applied to the electrode 3 has a reverse bias. The reverse breakdown voltage of the diode lowers the electric field strength in the insulating film 2 and the surge voltage does not cause dielectric breakdown. When the substrate 1 is n-type and the surge voltage applied to the electrode 3 is negative, the same effect is produced by forming a p-layer larger than the size of the electrode.

On the other hand, FIG. 2 shows an embodiment of the present invention which is effective regardless of the conductivity type of the substrate or the polarity of the voltage applied to the electrodes. In this case, the n layer 4 is formed on the surface layer of the p-type silicon substrate 1 of the integrated circuit, and the p layer 5 is further formed on the surface layer of the n layer 4. n layer 4,
Each of the p-layers 5 is in the process for manufacturing an integrated circuit,
It is formed at the same time as the diffusion step or the polycrystalline Si layer deposition step. The dimension of the p layer 5 is larger than the dimension of the electrode 3 on the insulating film 2 in any direction, the n layer 4 surrounds the p layer 5, and the depth under the p layer 5 is added to the electrode 3. It is determined from the height of the surge voltage and the resistivity of the p layer. In this structure, two diodes 11 and 12 are connected in anti-series as shown in the figure. When a positive surge voltage is applied to the electrode 3, the diode 11 is in the reverse direction and the diode 12 is in the forward direction, and when a negative surge voltage is applied, the diode 12 is in the reverse direction and the diode 11 is in the forward direction. Therefore, dielectric breakdown of the insulating film 2 does not occur even if a surge voltage of any polarity is applied. When the substrate of the integrated circuit is n-type, by forming the p-layer on the surface layer and the n-layer in the surface layer, two diodes in anti-series connection can be similarly obtained, and the same effect is produced. .

[0009]

According to the present invention, when a surge voltage is applied to an electrode in a region immediately below a wiring of a semiconductor substrate, a diode is formed so that the voltage becomes a reverse bias, whereby an insulating film directly below the electrode is formed. Since the withstand voltage of 50 V is improved by 50 V or more, the insulating film can be made thin, and is particularly effective for a semiconductor device such as an integrated circuit device in which the surface insulating film is thinned for miniaturization. Further, this diode has an advantage that it can be formed without adding steps during the manufacturing process of the semiconductor device.

[Brief description of drawings]

FIG. 1 is a sectional view of a pad electrode portion of a semiconductor device according to an embodiment of the present invention.

FIG. 2 is a sectional view of a pad electrode portion of a semiconductor device according to another embodiment of the present invention.

FIG. 3 is a sectional view of a pad electrode portion of a conventional semiconductor device.

[Explanation of symbols]

 1 p-type silicon substrate 2 insulating film 3 pad electrode 4 n layer 5 p layer

Claims (3)

[Claims] 1. A diode having an electrode provided on a semiconductor substrate via an insulating film, wherein a diode having a PN junction in a region including a region facing the electrode is formed in the semiconductor substrate immediately below the insulating film. A semiconductor device in which the diode is reverse-biased when a surge voltage is applied to the electrodes. 2. The semiconductor device according to claim 1, wherein the PN junction exists between the semiconductor substrate of the first conductivity type and the region of the second conductivity type formed in the surface layer of the substrate. 3. A PN junction is formed between a semiconductor substrate of the first conductivity type and a region of the second conductivity type formed in the surface layer of the substrate, and in the region of the second conductivity type and the surface layer of this region. 2. The semiconductor device according to claim 1, wherein the semiconductor device exists in both of the region of the first conductivity type and the region of the first conductivity type.