JPH09135020A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a gate-cathode avalanche strength by a method wherein a first conductivity type low-resistance region is formed in contact with the bottom of a cathode region and the impurity concentration of the low-resistance region is set higher than that of a first conductivity type region. SOLUTION: P-type gate regions 6 and a p-type region 3 are formed from the surface on one side of the surfaces of an n-type semiconductor substrate constituting an n-type high-resistance layer 2. Then, a p-type low-resistance region 4 is formed. Subsequently, after an n-type cathode region 5 is formed, patterns of insulating films 10 consisting of a silicon oxide film or the like are formed. The surface impurity concentration of the region 5 is set higher than those of the regions 3 and 4. In this case, a breakdown voltage of the bent part of the junction between the region 3 and the periphery of the region 5 is higher than that of the junction part between the region 4 and the bottom of the region 5 and most of a reverse current in a breakdown flows through the junction part between the region 4 and the bottom of the region 5. As a result, the improvement of a gate-cathode avalanche strength becomes possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device such as a turn-off thyristor having a flat gate structure, and more particularly to a method for improving a withstand voltage characteristic between a gate and a cathode.

[0002]

2. Description of the Related Art As a semiconductor device having a structure in which a p-type region is provided between opposing p-type gate regions of a plane type, and an n-type cathode region is selectively formed on the surface layer of the p-type region. The turn-off thyristors disclosed in JP-A-13310, JP-A-3-219640 and the like are known. The turn-off thyristor in the above example has a so-called normally-off characteristic that can prevent the forward voltage between the anode and the cathode without reverse biasing between the gate and the cathode, and has an improved turn-on compared to the conventional thyristor. There is a feature that the characteristics can be obtained.

In the above example, when the thickness of the p-type region is made smaller than that of the p-type gate region, the space charge amount per unit area of the depletion layer formed in the p-type region in the off state is calculated as the p-type gate region. The sheet resistance of the p-type region can be made larger than that of the conventional thyristor because it can be made smaller than the space charge amount. In order to further improve the turn-off characteristic, it is effective to reduce the resistance between the p-type region directly below the central portion of the n-type cathode region and the gate electrode. The unit element can be miniaturized by reducing the width of the p-type region.

[0004]

The turn-off thyristor of the above example is apt to have an insufficient avalanche withstanding capability when the gate and cathode are reverse-biased at the time of turn-off and breakdown occurs. In the case of such a thyristor, the breakdown voltage of the pn junction in which the n-type cathode region is selectively formed in the p-type region tends to be minimized in the bent portion of the peripheral junction. On the other hand, the thickness of the n-type cathode region is reduced with the miniaturization of the unit element,
As a result, the junction bending in the peripheral area becomes smaller,
It can be said that the increase in the breakdown current at the junction bending portion causes a lack of avalanche withstand capability. The present invention has been made in view of the above-mentioned points, and an object thereof is to provide an effective means for improving the avalanche withstand capability between the gate and the cathode, and to arrange a large number of unit elements in parallel. It is to provide an effective means for increasing the area and increasing the current.

[0005]

That is, the semiconductor device according to claim 1 is a means for achieving the above-mentioned object. A semiconductor device having a structure in which a lower first conductivity type region is provided, a second conductivity type cathode region is selectively formed on a surface layer of the first conductivity type region, and a cathode electrode is connected to the cathode region surface. A low resistance region of the first conductivity type is formed in contact with the lower surface of the region, and the impurity concentration of the low resistance region is set higher than that of the first conductivity type region.

According to another aspect of the semiconductor device of the present invention, a first conductivity type region having an impurity concentration lower than that of the gate region is provided between the planarly opposed gate regions of the first conductivity type. A first region is formed by surrounding a region in which a plurality of unit devices in which a cathode region of the second conductivity type is selectively formed on the surface layer are arranged in parallel.
A conductive type frame gate region is formed, a gate electrode is connected to the surface of the frame gate region, an insulating film is provided in a portion other than the cathode region of the unit element, and the cathode electrode is connected to the cathode region surface and extends on the insulating film. The existing structure is formed as a segment, a plurality of the segments are arranged in parallel, the frame gate region and the gate electrode of each segment are connected, and the cathode electrode of each segment is pressure-contacted via a common pressure-contact electrode. Connected in parallel by
A gate take-out electrode is connected to a part of the gate electrode, and the semiconductor device has the structure according to claim 1.

According to another aspect of the semiconductor device of the present invention, a first conductivity type region having an impurity concentration lower than that of the gate region is provided between the planarly opposed first conductivity type gate regions.
A frame gate region of the first conductivity type is formed by surrounding a region in which a plurality of unit elements in which a cathode region of the second conductivity type is selectively formed on the surface layer of the conductivity type region is arranged, and the frame gate region is partially formed. A high-concentration region of the first conductivity type is formed in the dug and dug surface portion, and a gate electrode is connected to the dug low surface, and an insulating film is provided in a portion other than the cathode region of the unit element. A segment having a structure in which the cathode electrode is connected to the surface of the cathode region and extends on the insulating film, and a plurality of the segments are arranged in parallel, and the frame gate region and the gate electrode of each segment are connected, A cathode electrode of each segment is connected in parallel by pressure contact through a common pressure contact electrode, and a gate extraction electrode is connected to a part of the gate electrode. Having the configuration of a semiconductor device according to.

[0008]

According to the semiconductor device of the first aspect, the junction between the low resistance region of the first conductivity type and the lower surface of the cathode region of the second conductivity type reduces bending, makes it easy to flatten the shape, and causes breakdown. The voltage can be easily adjusted by the impurity concentration in the low resistance region.
Then, the breakdown voltage of the lower surface portion of the cathode region can be set lower than that of the bent portion of the junction around the cathode region of the second conductivity type. Therefore, the breakdown current when the gate and cathode are reverse-biased is large at the low-side junction of the cathode region, and can be made small at the bend of the junction around the cathode region, thus improving the avalanche withstand capability. become.

According to the semiconductor device of the second aspect, the segments in which a plurality of unit elements are arranged in parallel are arranged in parallel, and the cathode electrodes of the segments are collectively pressure-contacted (press-contact) with a common press-contact electrode. It is possible to increase the area of the element and increase the current, and it is possible to improve reliability and reduce the thermal resistance by allowing both sides of the element to be cooled. According to the semiconductor device of claim 3, it is easy to increase a step between the cathode electrode and the gate electrode of each segment, and when the cathode electrodes are collectively pressure-contacted by using the pressure-contact electrode, the gap between the gate and the cathode electrode is reduced. The insulation distance can be increased, and the element can be easily assembled. Less than,
An embodiment of the present invention will be described in detail with reference to the drawings.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A turn-off thyristor as a semiconductor device according to a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional explanatory view of a unit element constituting a turn-off thyristor, in which 1 is a p-type anode region, 2 is an n-type high resistance layer made of an n-type semiconductor substrate, 3 is a p-type region, and 4 is a p-type region. A p-type low resistance region, 5 is an n-type cathode region, 6 is a p-type gate region, 7 is an anode electrode, 8 is a cathode electrode, and 9 is a gate electrode. The manufacturing process of this embodiment will be described with reference to FIG. As shown in FIG. 2a, a p-type gate region 6 and a p-type region 3 are formed from one surface of an n-type semiconductor substrate forming the n-type high resistance layer 2 by a selective diffusion method of boron. Next, as shown in FIG. 2b, the p-type low resistance region 4 is formed by the selective diffusion method of boron. Then, as shown in FIG. 2c, n
After the cathode region 5 is formed by the phosphorus or arsenic selective diffusion method, the pattern of the insulating film 10 made of a silicon oxide film or the like is formed. Subsequently, as shown in FIG. 1, an anode electrode 7, a cathode electrode 8 and a gate electrode 9 are formed by evaporating aluminum.

As an example of the junction structure, the surface impurity concentration of the n-type cathode region is 1 × 10 ²⁰ cm ³ , the thickness is 2 μm, and the impurity concentration of the p-type region and the p-type low resistance region is 1 × 10 ¹⁶ , respectively. It is composed of 1 × 10 ¹⁷ cm ³ . In this case, the breakdown voltage of the junction is about 25 V at the bent portion of the junction around the p-type region and the n-type cathode region, and about 20 V at the junction portion of the low surface of the p-type low resistance region and the n-type cathode region. Most of the reverse current flows through the lower junction of the n-type cathode region.

A turn-off thyristor as a second embodiment will be described with reference to FIG. FIG. 3 shows a cross-sectional structure of a segment in which a plurality of unit elements are arranged in parallel. In the figure, 11 is a frame gate region surrounding the area where the unit elements are arranged in parallel, 20 is a gate electrode, 21 is a cathode electrode, Reference numeral 12 is an insulating material made of polyimide or the like for preventing a short circuit between the gate electrode and the cathode electrode, and the other description is the same as in FIG. The segments shown in FIG. 3 have a horizontal direction of 1 to 3 mm in the drawing and a vertical direction of 0.1 to 0.3 mm in the drawing, and such segments are, for example, concentrically and radially arranged in parallel. The gate electrode 20 surrounding the cathode electrode 21 of each segment is usually connected throughout the device. The cathode electrodes arranged in parallel are connected in parallel by pressure contact via a common pressure contact electrode 21 made of molybdenum or tungsten. A gate pressure contact electrode is pressure contacted with the gate electrode at the center or outer periphery of the device.

A turn-off thyristor as a third embodiment will be described with reference to the segment sectional view shown in FIG. The third embodiment differs from the second embodiment in that a frame gate region 13 is dug in, a p-type high-concentration region 14 is formed in the surface portion thereof, and a gate electrode 30 is dug in a low-density region. It is the same as the second embodiment except that it is connected to the surface. In the third embodiment, it is easy to increase the step difference between the gate electrode and the cathode electrode as compared with the second embodiment, and the insulation distance between the pressure contact electrode 32 on the cathode electrode and the gate electrode is increased. Is easy. The present invention is an application example to a transistor by making the anode region of the turn-off thyristor of the above embodiment the same conductivity type as the cathode region. Further, it is apparent that the pressure contact electrode can be connected to the cathode electrode shown in the above embodiment by a welding method instead of pressure contact.

[0014]

As described above, according to the present invention, it is possible to improve and improve the avalanche withstand capability of a gate-cathode pn junction when a unit element of a semiconductor device having a planar gate structure is miniaturized. Furthermore, it is easy to arrange a large number of miniaturized unit elements in parallel to increase the area and current of the element, and to simplify the assembly structure of the element by applying the pressure contact structure. It is possible to obtain effects such as improvement and cooling of both sides of the element.

[Brief description of the drawings]

FIG. 1 is a cross-sectional explanatory view of a unit element showing a turn-off thyristor in a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a unit element showing a manufacturing process of the turn-off thyristor of the first embodiment.

FIG. 3 is an explanatory cross-sectional view of a segment showing a turn-off thyristor according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional explanatory view of a segment showing a turn-off thyristor according to a third embodiment of the present invention.

[Explanation of symbols]

 1 p-type anode region 2 n-type high resistance layer 3 p-type region 4 p-type low resistance region 5 n-type cathode region 6 p-type gate region 7 anode electrode 8 cathode electrode 9 gate electrode 10 insulating film 11 frame gate electrode 12 insulating material 13 Frame gate electrode 14 P-type high concentration region 15 Insulating material 20 Gate electrode 21 Cathode electrode 22 Pressure contact electrode 30 Gate electrode 31 Cathode electrode 32 Pressure contact electrode

Claims (3)

[Claims] 1. A first conductivity type region having an impurity concentration lower than that of the gate region is provided between gate regions of the first conductivity type that are opposed to each other in a plan view, and a second conductivity type is provided in a surface layer of the first conductivity type region. In a semiconductor device having a structure in which a cathode region is selectively formed and a cathode electrode is connected to the surface of the cathode region, a low resistance region of the first conductivity type is formed in contact with the bottom surface of the cathode region, and the low resistance region is formed. The impurity concentration of the semiconductor device is set higher than that of the first conductivity type region. 2. A first conductivity type region having an impurity concentration lower than that of the gate region is provided between the gate regions of the first conductivity type that are opposed to each other in a plan view, and a surface layer of the first conductivity type region is formed of the second conductivity type. A frame gate region of the first conductivity type is formed so as to surround a region in which a plurality of unit devices in which cathode regions are selectively formed are arranged in parallel, and a gate electrode is connected to the surface of the frame gate region, except for the cathode region of the unit device. An insulating film is provided on the cathode electrode, the cathode electrode is connected to the surface of the cathode region, and the structure is provided to extend on the insulating film to form a segment,
A plurality of the segments are arranged in parallel, the frame gate region and the gate electrode of each segment are connected, and the cathode electrodes of each segment are connected in parallel by pressure contact through a common pressure contact electrode, and a part of the gate electrode is connected. The semiconductor device according to claim 1, wherein a gate extraction electrode is connected. 3. A first conductivity type region having an impurity concentration lower than that of the gate region is provided between gate regions of the first conductivity type that are opposed to each other in plan view, and a surface layer of the first conductivity type region is formed of the second conductivity type. A frame gate region of the first conductivity type is formed so as to surround a region in which a plurality of unit elements in which the cathode region is selectively formed are arranged in parallel, and the frame gate region is partially dug into the dug surface. A high-concentration region of the first conductivity type is formed, and a gate electrode is connected to the dug-down low surface,
An insulating film is provided in a region other than the cathode region of the unit element, and the structure in which the cathode electrode is connected to the surface of the cathode region and extends on the insulating film is a segment, and a plurality of the segments are arranged in parallel. The frame gate region and the gate electrode of the segment are connected, and the cathode electrode of each segment is connected in parallel by pressure contact through a common pressure contact electrode, and the gate extraction electrode is connected to a part of the gate electrode. The semiconductor device according to claim 1.