JP2754947B2 - Semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly, to a semiconductor device in which the structure of a medium- and high-voltage protection diode element is considered.

[0002]

2. Description of the Related Art BV of a normal enhancement transistor
_{The DS} withstand voltage is several tens of volts. For example, when connecting to a car battery, a port with a withstand voltage of 18 volts or more is required.

Conventionally, the protection diode in, high-voltage port of this kind, as shown in FIG. 3, the n ⁺ -type region 6 is formed within the P-well region 3, apart from the n ⁺ -type region 6, A channel stopper region 11 is provided immediately below the element isolation region 10, and a P ⁺ type region 7 is formed as an anode electrode. The middle and high-voltage diodes, a Pn junction formed by the P-well region 3 and the n ⁺ -type region 6, for example, a P-well B ⁺ 10
Heat treatment was performed at 1200 ° C. for 2.5 hours under the implantation condition of 0 Kev2.1E13, and the n ⁺ -type region was changed to As ⁻ 70 Kev3.0E.
When formed under 15 implantation conditions, the reverse breakdown voltage of this diode is about 20 V, and a desired value can be obtained.

Next, the operation as a protection element will be described.

[0005] If the cathode is biased in the reverse direction, since breakdown voltage that is determined in part in contact with the n ⁺ -type region 6 and the element isolation region 10, the current from the side surface of the n ⁺ -type region 6 flows It passes through the P ⁺ type region 7 and is used as an anode electrode. Therefore, if the n ⁺ -type region 6 is made large and the side surface length is made large, the current allowable capacity is improved, and accordingly, the ESD (electrostatic breakdown) resistance when reverse bias is applied is also increased. On the other hand, when the cathode electrode is biased in the forward direction, the current flows through the n ⁺ -type contact region 5 having the lowest resistance formed in the contact hole in a self-aligned manner. Since a large current locally flows in a small area of the contact hole, the Pn junction is easily thermally destroyed. For example, when an ESD test using a machine model is performed, the protection diode is broken at about 100 to 200 V regardless of the size of the protection diode.

[0006]

The conventional withstand voltage is 10
Medium / high withstand voltage protection diodes for the latter half of the V generation, when the cathode electrode is forward biased by the surge voltage,
Current concentrates and flows just below the contact hole, and Pn
There is a problem that the joint is easily broken and the protection ability is low.

[0007]

According to the present invention, there is provided a semiconductor device comprising:
A first region of a second conductivity type and a second region of a first conductivity type are provided on a surface of a semiconductor substrate of a first conductivity type, and a protection diode is formed between the first region and the second region. In the semiconductor device, a third region of a second conductivity type is formed on the surface of the semiconductor substrate so as to overlap the first region, and a second region connected to an electrode of the protection diode is formed in the third region. A fourth region of a conductivity type is formed, and the third region is a region deeper than the fourth region and the first region.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of a first embodiment of the present invention. An n-well region 2 is formed in a P-type semiconductor substrate 1, and a contact with a cathode electrode of a diode is formed inside the n-well region 2, and a large n ⁺ -type region 6 is formed so as to cover the n-well region 2. The side surface of the n ⁺ type region 6 is the element isolation region 1
0 and overlaps with the P-well region 3, and P is formed inside the P-well region 3 as an anode electrode.
^{A +} type region 7 is provided.

When the cathode electrode 8 is biased in the reverse direction, the breakdown voltage is determined on the side surface of the n ⁺ -type region 6 where the concentration gradient is the largest. It has a withstand voltage of V.

However, the Pn junction formed by the n-well region 2 and the P-type semiconductor substrate 1 is a portion where the concentration gradient is the smallest, and when the cathode electrode is biased in the reverse direction and the depletion layer is fully extended, the P-well region 3 Unless the n-well region 2 and the P-well region 3 are separated from each other by a certain distance so as not to reach the desired voltage, a desired breakdown voltage cannot be obtained . If the current from the side surface of the conventional the cathode electrode 8 is reverse biased examples as well as n ⁺ -type region 6 to the anode electrode 9 This is the ESD immunity is improved according to aspects length of flow diode.

Next, when the cathode electrode 8 is biased in the forward direction, since the n-well region 2 deeper than the n ⁺ -type contact injection region 5 is formed, the lowest resistance is from the cathode electrode to the n-well region. This is a path through which the current flows to the intersection of the n ⁺ -type region 2 and the n ⁺ -type region 6, and unlike the case shown in the conventional example, the current does not intensively flow directly below the contact hole.

FIG. 2 is a plan view of the first embodiment. When the cathode electrode 8 is biased in the forward direction, current flows to the side of the n-well region 2 and is proportional to the size of the n-well region 2. As a result, the current allowable capacity is increased, and the ESD tolerance is also improved accordingly. Therefore, unlike the conventional example, there is no portion through which current flows in a concentrated manner. For example, if the side length of the diode is set to about 500 μm in a machine model of an ESD test, an ESD resistance of about 400 V can be obtained. The protection ability against surge voltage is much higher.

FIG. 4 is a sectional view of the second embodiment. In this embodiment, as in the previous embodiment, the cathode portion is formed by the n-well region 2 deeper than the n ⁺ contact injection region 5.
When the anode electrode is forward biased,
The current does not intensively flow immediately below the contact unlike the conventional example, and the protection capability against the surge voltage is determined by the size of the n-well region 2. When the anode electrode is biased in the reverse direction, the breakdown voltage becomes as large as about 50 to 60 V due to the small concentration gradient of the Pn junction between the P-type semiconductor substrate 1 and the n-well region 2. There is no problem at all, and the protection capability against surge voltage is determined by the side length of the n-well region 2 as in the case of the forward bias. In Example 2, the side length of the diode was about 500 μm, and the
It has a protection capacity of about 00V.

[0015]

The present invention described above, according to the present invention, by forming the deep n-well region than the contact injection layer to the cathode electrode of the medium- and high protection diode, the protection capability when a surge voltage is applied It has the effect of increasing.

[Brief description of the drawings]

FIG. 1 is a sectional view of a first embodiment of the present invention.

FIG. 2 is a plan view of a cathode section according to the first embodiment of the present invention.

FIG. 3 is a sectional view of a conventional example.

FIG. 4 is a sectional view of a second embodiment of the present invention.

Claims (1)

(57) [Claims] 1. A first region of a second conductivity type and a second region of a first conductivity type are provided on a surface of a semiconductor substrate of a first conductivity type, and a first region of the second conductivity type is provided between the first region and the second region. In a semiconductor device having a protection diode formed thereon, a third region of a second conductivity type is formed on the surface of the semiconductor substrate so as to overlap with the first region, and further, an electrode of the protection diode is formed in the third region. A semiconductor device, wherein a fourth region of a second conductivity type to be connected is formed, and the third region is a region deeper than the fourth region and the first region.