JPH07273307A - High breakdown strength semiconductor device - Google Patents

Abstract

PURPOSE:To arrange functionally a positive bevel configuration and a negative bevel configuration in an end surface of a semiconductor substrate to exhibit high reliability and high breakdown strength characteristics. CONSTITUTION:A high breakdown strength semiconductor device comprises at least a first semiconductor region 2 of a p-type high impurity concentration and a second semiconductor region 3 of an n-type, and a pn junction part 13 is formed with the first semiconductor region 2 and second semiconductor region 3, and the above device comprises a semiconductor substrate 1 of which an end surface 9 is exposed, an anode electrode 7 provided in the first semiconductor region 2 and a cathode electrode 8 provided in the second semiconductor region 3. In the end surface 9 exposed from the semiconductor substrate 1, a specific thickness portion containing a pn junction part 13 has a positive bevel configuration 10. A remaining thickness portion is formed so as to have a negative bevel configuration 11, and the cathode electrode 8 projects outwardly of the end surface 9 exposed from the second semiconductor region 3 and a length containing the projected portion is equal to or slightly longer than the longest width between the end surfaces of the first semiconductor region 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high breakdown voltage semiconductor device, and more particularly, to a semiconductor substrate having an exposed end surface having a positive bevel structure and a negative bevel structure, which has a high breakdown voltage characteristic and a high reliability. The present invention relates to a high breakdown voltage semiconductor device having both characteristics.

[0002]

2. Description of the Related Art Conventionally, in a high breakdown voltage semiconductor device, particularly in a high breakdown voltage diode, a p-type semiconductor region and an n-type semiconductor region form a semiconductor substrate having a pn junction, and the pn in the semiconductor substrate is formed. The exposed end face including the junction is formed into a bevel structure, and the bevel angle of the bevel structure is appropriately adjusted to reduce the electric field strength generated on the end face including the pn junction to obtain a diode having a high breakdown voltage characteristic. Means (hereinafter referred to as known first means) are known. Then, this known first means is, for example, “IEEE Transaction o
n Electron Devices "Vol. ED
-31, No. 6, P733 (1984) and the like.

Similarly, in a high breakdown voltage diode, a pn is formed by a p-type semiconductor region and an n-type semiconductor region.
A semiconductor base having a junction is formed, and an exposed end surface (side surface) including the pn junction of the semiconductor base is formed into a concave curve, and the apex of the concave curve is the p-type semiconductor region. And a means for obtaining a diode having a high withstand voltage characteristic by preventing discharge from occurring on the surface portion of the semiconductor substrate by forming the diode so as to come to the side of the low impurity concentration semiconductor region in the n-type semiconductor region (hereinafter referred to as The known second means) is also known. The known second means is disclosed in, for example, Japanese Utility Model Publication No. 48-40370.

Further, in other high breakdown voltage semiconductor devices, particularly in static induction thyristors, static induction transistors, etc., at least one or more p-type semiconductor regions and n are respectively provided.
A semiconductor substrate having two or more pn junctions is formed by the type semiconductor region, and one of the p-type semiconductor regions has a p-type junction.
The end surface including the n-junction portion is formed into a positive bevel structure, and the other end surface including the pn junction portion is formed into a negative bevel structure. By forming these two bevel structures, an electrostatic induction thyristor having high withstand voltage characteristics and A means for obtaining an electrostatic induction transistor or the like (hereinafter, referred to as a known third means) is known. The known third means is disclosed, for example, in JP-A-64-45171 and JP-A-62-150774.
JP-A-61-144871, JP-A-61-137
No. 361 and JP-A-60-163460.

[0005]

However, in the known first means, the electric field strength generated at the end face of the semiconductor substrate including the pn junction is not uniform, and the bevel angle of the bevel structure formed on the end face is Depending on the polarity and strength of the charges in the protective film, the electric field strength of the surface portion of the end face of the n-type semiconductor region close to the p-type semiconductor region or the n-type semiconductor region having a high impurity concentration becomes large, so There is a problem that the yield phenomenon is likely to occur.

That is, the breakdown phenomenon is caused by the pn of the semiconductor substrate.
It does not occur uniformly at the joint, but occurs exclusively at the end face portion. Even if a high breakdown voltage diode is obtained, when a breakdown phenomenon occurs in the high breakdown voltage diode, it is locally generated. The semiconductor substrate is likely to be broken due to heat generation. This phenomenon remarkably occurs particularly when performing a life test such as a so-called high temperature bias test in which a voltage is applied to the high withstand voltage diode and kept at a high temperature.

Further, since the known second means does not sufficiently consider the amount of electric charges existing in the stabilizing film on the surface of the high breakdown voltage diode, like the known first means, in the high breakdown voltage diode, When performing a life test such as a high temperature bias test, the blocking characteristic of the high breakdown voltage diode is deteriorated, and there is a problem that a satisfactory high breakdown voltage characteristic cannot be obtained.

Further, in any of the known third means, the end face including one pn junction in the semiconductor substrate is formed into a positive bevel structure, and the end face including the other pn junction is formed into the negative bevel. When the structure is formed, the position where the positive bevel structure is converted to the negative bevel structure is provided at a substantially central position with respect to the thickness of the semiconductor substrate, so the functions of these two bevel structures are not fully utilized. There is a problem.

The present invention eliminates the above-mentioned problems, and an object thereof is to functionally dispose a positive bevel structure and a negative bevel structure on an end face of a semiconductor substrate, thereby sufficiently satisfying high reliability and high reliability. An object of the present invention is to provide a high breakdown voltage semiconductor device capable of exhibiting breakdown voltage characteristics.

[0010]

In order to achieve the above-mentioned object, the present invention provides at least a first semiconductor region of a high impurity concentration of a first conductivity type and a second semiconductor region of a second conductivity type. And a semiconductor substrate in which a pn junction is formed by the first semiconductor region and the second semiconductor region, and an end face is exposed, and a first electrode provided on the surface of the first semiconductor region. And a second electrode provided on the surface of the second semiconductor region, the exposed end face of the semiconductor substrate has a constant thickness in the thickness direction including the pn junction. Part has a positive bevel structure, and the remaining thickness part has a negative bevel structure, and the second electrode is outside the exposed end surface of the semiconductor region of the provided part. Projecting in the direction of the Length including comprises means for constituting slightly longer than or equal to the largest width between the end faces of the first semiconductor region.

[0011]

According to the above means, the exposed end surface of the semiconductor substrate is formed in the thickness direction so that the portion having a constant thickness including the pn junction has the positive bevel structure.
The depletion layer formed in the semiconductor substrate largely spreads toward the second semiconductor region side, and the breakdown voltage of the semiconductor device can be increased. Further, the exposed end surface of the semiconductor substrate is formed in the thickness direction so that the remaining thickness part of the constant thickness part has a negative bevel structure, and the second electrode is provided. Since the semiconductor region is formed so as to protrude outward from the exposed end face and the length including the protruding portion is equal to or slightly longer than the longest width between the end faces of the first semiconductor region, The combined use of the negative bevel structure and the protruding portion of the second electrode suppresses the expansion of the depletion layer toward the second semiconductor region side, and the electric field strength at a specific portion does not rise extremely, resulting in high reliability. It is possible to obtain a high breakdown voltage semiconductor device having both high breakdown voltage characteristics and high breakdown voltage characteristics.

Therefore, even if the electric charge of the stabilizing film on the surface of the semiconductor substrate is uneven, the electric field strength at the surface portion of the end face of the second semiconductor region does not locally increase, and the high breakdown voltage semiconductor device is obtained. The high withstand voltage characteristic of does not deteriorate.

In this case, the semiconductor device has a structure in which a third semiconductor region having the same conductivity type as that of the second semiconductor region and a high impurity concentration is provided between the second semiconductor region and the second electrode. At some point, the exposed end face of this third semiconductor region
If the exposed end face of the second semiconductor region is formed to have a continuous negative bevel structure, the second semiconductor region and the third semiconductor region can be formed.
It is possible to effectively prevent the electric field strength of the end face near the junction with the semiconductor region from becoming extremely high.

[0014]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a cross sectional view showing the structure of a first embodiment of a high breakdown voltage semiconductor device according to the present invention.

In FIG. 1, 1 is a semiconductor substrate, 2 is a p-type (first conductivity type) high impurity concentration first semiconductor region,
3 is an n-type (second conductivity type) second semiconductor region, 4 is n
-Type (second conductivity type) high impurity concentration third semiconductor region, 5 is the first main surface of the semiconductor substrate 1, 6 is the second main surface of the semiconductor substrate 1, 7 is an anode electrode, and 8 is A cathode electrode, 9 is an end surface of the semiconductor substrate 1, 10 is a positive bevel structure portion of the end surface 9, 11 is a negative bevel structure portion of the end surface 9, 12 is a turning point of the bevel structure, 13 is a pn junction, and 14 is nn +. It is a junction.

The semiconductor substrate 1 is composed of a p-type first semiconductor region 2, an n-type second semiconductor region 3, and an n-type third semiconductor region 4, which are laminated structures. Is the first surface of the p-type first semiconductor region 2 side.
Is the main surface 5 of the above, and the surface on the n-type third semiconductor region 4 side is the second main surface 6. An anode electrode 7 is formed in an ohmic contact state on the p-type first semiconductor region 2 on the first main surface 5, and an anode electrode 7 is formed on the n-type third semiconductor region 4 on the second main surface 6. -The electrode 8 is formed in an equipotential contact state. The boundary between the p-type first semiconductor region 2 and the n-type second semiconductor region 3 constitutes a pn junction 12, and both of the n-type second semiconductor region 3 and the third semiconductor region 4 are formed. The boundary constitutes the nn + junction 14. The semiconductor substrate 1 is an end face 9 whose side surface is exposed. The exposed end face 9 has a positive bevel structure 10 (a structure in which the width between the end faces decreases from the low impurity concentration portion to the high impurity concentration portion). The bevel structure 11 (the structure in which the width between the end faces decreases from the high impurity concentration portion to the low impurity concentration portion). The turning point 12 of the bevel structure, which is the junction between the positive bevel structure 10 and the negative bevel structure 11, is the semiconductor substrate 1
In the thickness direction of the semiconductor substrate 1, the semiconductor substrate 1 is provided at a position deviated considerably from the center toward the second main surface 6, that is, at a position deviated to the negative bevel structure in the semiconductor substrate 1.

In the high breakdown voltage semiconductor device of the first embodiment having the above-mentioned structure, when a voltage is applied between the anode electrode 7 and the cathode electrode 8 so that the anode electrode 7 side is negative and the cathode electrode 8 side is positive. , A reverse bias voltage is applied to the pn junction 13 between the p-type first semiconductor region 2 and the n-type second semiconductor region 3. By applying this reverse bias voltage, a depletion layer is generated in the semiconductor substrate 1, and the depletion layer is pn.
It extends from the junction 13 to the inside of the p-type first semiconductor region 2 side and the n-type second semiconductor region 3 side. In this case, the first
In the embodiment, since the end surface 9 including the pn junction 13 is formed in the positive bevel structure 10, the depletion layer has a small spread to the side of the p-type first semiconductor region 2 having a high impurity concentration, The spread toward the n-type second semiconductor region 3 side having a relatively low impurity concentration becomes large, and moreover, the pn junction 1
The expansion of the depletion layer in the area 3 is smaller on the end face 9 than on the inside on the p-type first semiconductor region 2 side, and conversely,
On the n-type second semiconductor region 3 side, the number of end faces 9 is considerably larger than that of the inside.

Here, the depletion layer extending toward the n-type second semiconductor region 3 side extends toward the n-type third semiconductor region 4 side along the end face 9 of the n-type second semiconductor region 3. It will spread out. In this case, in the first embodiment, the end face 9 of the n-type second semiconductor region 3 has a bevel structure turning point which is separated from the pn junction 13 by a certain thickness in the thickness direction of the semiconductor substrate 1. At 12, the positive bevel structure 10 is changed to the negative bevel structure 11, so that the depletion layer extending along the end face 9 of the n-type second semiconductor region 3 toward the n-type third semiconductor region 4 side is The presence of the negative bevel structure 11 ahead of the turning point 12 of the bevel structure suppresses the spread in the direction along the end surface 9.

Further, in the first embodiment, the cathode electrode 8 has both ends projecting outward from the exposed end surface 9 of the n-type third semiconductor region 4, and the projecting portion thereof. Is equal to or slightly longer than the longest width between the end faces 9 in the p-type first semiconductor region 2, so that the negative bevel from the turning point 12 of the bevel structure to the negative bevel. The depletion layer extending in the direction of the structure 11, that is, along the end face 9 of the n-type second semiconductor region 3 toward the n-type third semiconductor region 4 side, protrudes to the outside of the cathode electrode 8. The extended portion further suppresses the spread along the end surface 9.

By the way, in the first embodiment,
Both ends of the cathode electrode 8 are formed to be shorter than the longest width between the end faces 9 in the p-type first semiconductor region 2. In particular, both ends of the cathode electrode 8 are n-type third semiconductor regions. 4 is formed to be equal to or shorter than the longest width between the end faces 9 in FIG. 4, the lines of electric force generated by the voltage applied between the anode electrode 7 and the cathode electrode 8 Are concentrated at the nn + junction 14 at the boundary between the n-type second semiconductor region 3 and the n-type high impurity concentration third semiconductor region 4, and as a result, the end face 9 near the nn + junction 14 is formed. Since the electric field strength becomes extremely high, it becomes difficult to obtain a highly reliable high breakdown voltage semiconductor device.

On the other hand, in the first embodiment, the end face 9 of the semiconductor substrate 1 is formed so as to have the positive bevel structure 10 and the negative bevel structure 11, and moreover, the cathode electrode 8 is formed.
Are formed so as to be equal to or slightly longer than the longest width between the end faces 9 in the p-type first semiconductor region 2, so that the n-type second portion is formed from the pn junction portion 13.
The depletion layer extending along the end face 9 of the semiconductor region 3 is effectively suppressed by both the negative bevel structure 11 and the projecting portion of the cathode electrode 8, whereby the end face 9 near the nn + junction 14 is suppressed. It is possible to obtain a semiconductor device having both high reliability and high withstand voltage characteristics, because the electric field strength does not rise extremely.

Here, FIG. 2 is a characteristic diagram showing the distribution of the electric field intensity at each part of the end surface 9 of the semiconductor substrate 1.
The characteristics of the high breakdown voltage semiconductor device of the first embodiment are shown in comparison with the characteristics of a known high breakdown voltage semiconductor device and a known high breakdown voltage semiconductor device.

In FIG. 2, the vertical axis represents the electric field strength expressed in kV / cm, and the horizontal axis represents the distance from the second main surface 6 expressed in arbitrary units. The curve is the characteristic of the high breakdown voltage semiconductor device of the first embodiment, the curve is the characteristic of the known high breakdown voltage semiconductor device, and the curve is the characteristic of the reference high breakdown voltage semiconductor device. The same components as those shown in FIG. 1 are designated by the same reference numerals.

In this case, the known high breakdown voltage semiconductor device is provided with only the positive bevel structure 10 on the end surface 9 of the semiconductor substrate 1 without the negative bevel structure 11, and both ends of the cathode electrode 8 are n-type high. The reference high withstand voltage semiconductor device is configured to be equal to or shorter than the width between the end faces of the third semiconductor region 4 having an impurity concentration, while the reference high withstand voltage semiconductor device is the same as the high withstand voltage semiconductor device of the first embodiment. Both ends of the cathode electrode 8 are configured to be equal to or shorter than the width between the end faces of the n-type high impurity concentration third semiconductor region 4.

As shown in the curve of FIG. 2, according to the known high breakdown voltage semiconductor device, the line of electric force generated by the voltage applied between the anode electrode 7 and the cathode electrode 8 is n. -Type second semiconductor region 3 and n-type third semiconductor region 4 having a high impurity concentration are concentrated near the nn + junction 14, and the electric field strength of the end face 9 near the nn + junction 14 is extremely high. Therefore, it has been extremely difficult to obtain a high breakdown voltage semiconductor device having both high reliability and high breakdown voltage characteristics. Further, as shown by the curve in FIG. 2, according to the reference high breakdown voltage semiconductor device, a positive bevel structure is formed on the end surface 9 of the semiconductor substrate 1, specifically, the end surface 9 of the n-type second semiconductor region 3. Since there is a bevel structure inversion point 12 that is changed from 10 to the negative bevel structure 11, the increase in the electric field strength of the end face 9 near the nn + junction 14 which occurs in the known high breakdown voltage semiconductor device is considerably alleviated. Since the electric field strength of the end face 9 near the turning point 12 of the bevel structure is increased, it is also difficult to obtain a high breakdown voltage semiconductor device having both high reliability and high breakdown voltage characteristics. On the other hand, FIG.
As shown by the curve, the high withstand voltage semiconductor device of the first embodiment increases the electric field strength of the end surface 9 near the nn + junction 14 and the electric field strength of the end surface 9 near the turning point 12 of the bevel structure. Both increases can be mitigated, which makes it possible to obtain a high breakdown voltage semiconductor device having both high reliability and high breakdown voltage characteristics.

In the description of the first embodiment, the n-type third semiconductor region 4 having a high impurity concentration is provided between the n-type second semiconductor region 3 and the cathode electrode 8. However, in the present invention, the third semiconductor region 4 of the n-type high impurity concentration may be omitted, and the function and operation when omitted are the same as those of the first embodiment. And the operation is almost the same.

Continuing, FIG. 3 is a cross sectional view showing the structure of a second embodiment of the high breakdown voltage semiconductor device according to the present invention.
The gate turn-off (G) of the first embodiment shown in FIG.
It shows an example applied to a TO) thyristor.

In FIG. 3, 15 is a p-type semiconductor emitter region, 16 is an n-type semiconductor emitter region, and 17 is a gate.
The same components as those shown in FIG. 1 are denoted by the same reference numerals.

The difference between the structure of the first embodiment and the structure of the second embodiment is firstly that the p-type first structure is used.
Semiconductor region 2 is a p-type base region (p _B ), and n
-Type second semiconductor region 3 is an n-type n-base region (n _B ).
Second, a plurality of p-type semiconductor emitter regions 15 reaching the n-type n base region (n _B ) are provided inside the n-type high impurity concentration third semiconductor region 4. Third, a plurality of n-type semiconductor emitter regions 16 and a plurality of gate electrodes 17 are formed on the surface of the p-type first semiconductor region 2.
And a divided anode electrode 7 is provided on each of the plurality of n-type semiconductor emitter regions 16.
In other respects, there is no difference in structure between the first embodiment and the second embodiment.

The basic operation mode of the GTO thyristor according to the second embodiment having the above-mentioned structure is the same as that of a normal GTO thyristor, and the operation mode is well known in the art. Therefore, the description of the operation mode in the GTO thyristor of the second embodiment is omitted.

Also in the second embodiment, as in the first embodiment, a voltage between the anode electrode 7 and the cathode electrode 8 is negative on the anode electrode 7 side and positive on the cathode electrode 8 side. Is applied, a reverse bias voltage is applied to the pn junction 13 between the p-type base region (p _B ) and the n-type n base region (n _B ) and is generated in the semiconductor substrate 1 at that time. From the depletion layer and the pn junction 13 to the p-type base region (p
_B ) and the n-type n base region (n _B ). In this case, the end face 9 including the pn junction 13 is also used in the second embodiment.
Since There has been a positive bevel structure 10, the depletion layer, p-type base having a high impurity concentration - than the spread of the source region (p _B), a relatively impurity concentration smaller n-type n base region (n
_B ) and the pn junction 13
In the n-type n base region (n _B ), the spread of the depletion layer in the end face 9 is larger in the end face 9 than in the inside. Also in this second embodiment, the end surface 9 of the n-type n base region (n _B ) is changed from the positive bevel structure 10 to the negative bevel structure 11 at the turning point 12 of the bevel structure, so that the n-type n base region (n _B )
The depletion layer expanding toward the n-type third semiconductor region 4 side along the end face 9 is suppressed from spreading along the end face 9 by the negative bevel structure 11 ahead of the turning point 12 of the bevel structure.

Furthermore, in the second embodiment as well,
The both ends of the electrode 8 project outward from the exposed end surface 9 of the n-type third semiconductor region 4, and the end surface in the base region (p _B ) having a length of p-type including the projecting portion. The depletion layer extending from the turning point 12 of the bevel structure toward the n-type third semiconductor region 4 side along the end face 9 is equal to or slightly longer than the longest width between the two. Of the cathode electrode 8 is prevented from spreading along the end surface 9 by the outwardly projecting portion.

As described above, according to the second embodiment, pn
The depletion layer extending from the junction 13 along the end face 9 of the n-type n base region (n _B ) is effectively suppressed by both the negative bevel structure 11 and the protruding portion of the cathode electrode 8. As a result, it is possible to obtain a high breakdown voltage semiconductor device GTO thyristor) that suppresses an extreme increase in the electric field strength at the end face 9 close to the nn + junction 14 and achieves both high reliability and high breakdown voltage characteristics.

Next, FIG. 4 is a cross sectional view showing the structure of a third embodiment of the high breakdown voltage semiconductor device according to the present invention.

In FIG. 4, 18 is an n-type fourth semiconductor region, 19 is an nn-junction portion, and other same components as those shown in FIG. 1 are designated by the same reference numerals.

The difference between the structure of the first embodiment and the structure of the third embodiment is that, firstly, the n-type second structure is used.
Second semiconductor region 3 of n-type low impurity concentration (n-). Second, the second semiconductor region 3 of n-type low impurity concentration (n-) is formed. Between the n-type third semiconductor region 4 having a high impurity concentration and the n-type fourth semiconductor region 18, and other points are the same as those of the first embodiment. There is no difference in structure from the third embodiment.

Also in the high withstand voltage semiconductor device of the third embodiment having the above structure, a voltage is applied between the anode electrode 7 and the cathode electrode 8 so that the anode electrode 7 side is negative and the cathode electrode 8 side is positive. The operation mode at this time is almost the same as the operation mode of the high breakdown voltage semiconductor device of the first embodiment,
In the third embodiment, an n-type fourth semiconductor region 18 is provided between the n-type low impurity concentration second semiconductor region 3 and the n-type high impurity concentration third semiconductor region 4. Is interposed, one nn is formed at the boundary between the n-type low impurity concentration second semiconductor region 3 and the n-type fourth semiconductor region 18.
-A junction 19, another nn + junction 14 is formed at the boundary between the n-type fourth semiconductor region 18 and the n-type high impurity concentration third semiconductor region 4, and these nn- junctions 19 are formed.
Since the electric field is dispersed between the nn + junction and the nn + junction, the increase in the electric field strength can be further alleviated as compared with the electric field intensity generated on the end face 9 near the nn + junction 14 in the first embodiment. Therefore, it is possible to obtain a high breakdown voltage semiconductor device having both higher reliability and higher breakdown voltage characteristics than those of the high breakdown voltage semiconductor device of the first embodiment.

Next, FIG. 5 is a cross-sectional view showing the structure of the fourth embodiment of the high breakdown voltage semiconductor device according to the present invention, and the gate gate of the third embodiment shown in FIG. It shows an example applied to a turn-off (GTO) thyristor.

In FIG. 5, the same components as those shown in FIGS. 3 and 4 are designated by the same reference numerals.

The difference between the structure of the second embodiment and the structure of the fourth embodiment is firstly that the n-type n base region (n _B ) has a low n-type impurity concentration ( that consist n base region of the n-) (n _B), the second, third n base region (n _B) and n-type high impurity concentration of the low impurity concentration of the n-type (n-) The fourth semiconductor region 18 of the n-type is provided between the second and fourth semiconductor regions 4, and the other points are the same as those of the second and fourth embodiments. I can't find the difference above.

The basic operation mode of the GTO thyristor according to the fourth embodiment having the above structure is the same as that of a normal GTO thyristor, and the operation mode is well known in the art. Therefore, the description of the operation mode in the GTO thyristor of the fourth embodiment will be omitted.

Also in the fourth embodiment, as in the third embodiment, the n-type low impurity concentration (n-) n base region (n _B ) and the n-type high impurity concentration of the third embodiment are used. Since the n-type fourth semiconductor region 18 is interposed between the n-type semiconductor region 4 and the n-type semiconductor region 4, the n-type low impurity concentration (n-) n-base region (n _B ) and the n-type fourth region 18 are formed. N on the boundary of the semiconductor region 18 of
The nn + junction 14 is formed at the boundary between the n− junction 19, the n-type fourth semiconductor region 18 and the n-type high impurity concentration third semiconductor region 4, and the nn− junction 19 and the nn + junction are formed. Since the electric field is dispersed between n and n in the second embodiment
Compared with the electric field strength generated on the end face 9 near the n + junction 14,
A high breakdown voltage semiconductor device (GTO thyristor) that can further alleviate the increase in electric field strength and has both higher reliability and higher breakdown voltage characteristics than the high breakdown voltage semiconductor device (GTO thyristor) of the second embodiment. ) Can be obtained.

Next, FIG. 6 is a transverse sectional view showing the structure of the fifth embodiment of the high breakdown voltage semiconductor device according to the present invention.

In FIG. 6, reference numeral 20 is an accessory electrode, and other components that are the same as those shown in FIG. 1 are designated by the same reference numerals.

The difference between the structure of the first embodiment and the structure of the fifth embodiment is that, firstly, both ends of the cathode electrode 8 are n-type third semiconductors of high impurity concentration. The point that the length is almost equal to the width between the end faces of the region 4, the second
An auxiliary electrode 20 is provided on the surface of the cathode electrode 8. The auxiliary electrode 20 projects outward from both ends of the cathode electrode 8 and has a p-type first length including the projecting portion.
Is equal to or slightly longer than the longest width between the end faces of the semiconductor region 2, and the other points are between the first embodiment and the fifth embodiment. There is no structural difference.

The high breakdown voltage semiconductor device of the fifth embodiment having the above structure is substantially equivalent to the high voltage semiconductor device of the first embodiment in which the cathode electrode 8 of the first embodiment is replaced with the auxiliary electrode 20 of the fifth embodiment. Therefore, the operation mode when a voltage that the anode electrode 7 side is negative and the cathode electrode 8 side is positive is applied between the anode electrode 7 and the cathode electrode 8 is the same as that of the first embodiment described above. The operation mode of the withstand voltage semiconductor device is almost the same, and similarly to the first embodiment, the fifth embodiment also provides a high withstand voltage semiconductor device having both high reliability and high withstand voltage characteristics. It is what is done.

Next, FIG. 7 is a cross-sectional view showing the structure of a sixth embodiment of the high breakdown voltage semiconductor device according to the present invention, and the gate gate of the fifth embodiment shown in FIG. It shows an example applied to a turn-off (GTO) thyristor.

In FIG. 7, the same components as those shown in FIGS. 2 and 5 are designated by the same reference numerals.

The difference between the structure of the second embodiment and the structure of the sixth embodiment is, firstly, that both ends of the cathode electrode 8 are n-type third semiconductors of high impurity concentration. The point that the length is almost equal to the width between the end faces of the region 4, the second
In addition, an auxiliary electrode 20 is provided on the surface of the cathode electrode 8. The auxiliary electrode 20 projects outward from both ends of the cathode electrode 8, and the length including the projecting portion is a p-conduction type first electrode. It is configured such that it is equal to or slightly longer than the longest width between the end faces of the semiconductor region 2, and other points are between the first embodiment and the fifth embodiment. There is no structural difference.

The basic operation mode of the GTO thyristor according to the sixth embodiment having the above-mentioned structure is the same as that of the normal GTO thyristor, and the operation mode is well known in the art. Therefore, the description of the operation mode in the GTO thyristor of the sixth embodiment will be omitted.

The high breakdown voltage semiconductor device of the sixth embodiment having the above structure is also substantially the same as the cathode electrode 8 of the second embodiment.
Is equivalent to the electrode of the sixth embodiment replaced by the accessory electrode 20, so that between the anode electrode 7 and the cathode electrode 8,
The operation mode when a voltage is applied such that the anode electrode 7 side is negative and the cathode electrode 8 side is positive is almost the same as the operation mode of the high breakdown voltage semiconductor device of the second embodiment described above. Two
Similar to the embodiment described above, also in the sixth embodiment, a high breakdown voltage semiconductor device having both high reliability and high breakdown voltage characteristics can be obtained.

In each of the above embodiments, the length of the protruding portion of the cathode electrode 8 or the auxiliary electrode 20 is, of course,
It cannot be uniformly determined because it depends on the size of each part constituting the semiconductor device, but in the case of the cathode electrode 8, when the thickness is 10 to 20 μm, for example,
The length of the protruding portion is selected to be about 1 to 5 mm.

[0054]

As described above, according to the present invention,
The exposed end surface 9 of the semiconductor substrate 1 has p
The part of constant thickness including the n-junction 13 is a positive bevel structure 1
Therefore, the depletion layer formed in the semiconductor substrate 1 is the second semiconductor region 3 of the second conductivity type.
There is an effect that it can be widely spread to the side and the breakdown voltage of the semiconductor device can be increased.

Further, according to the present invention, the exposed end surface 9 of the semiconductor substrate 1 is formed in the thickness direction so that the remaining thickness portion of the constant thickness portion has the negative bevel structure 11. Moreover, the second electrode 8 projects outward from the exposed end surface of the semiconductor region in which the second electrode 8 is provided, and the length including the projecting portion is the end surface of the first semiconductor region 2 of the first conductivity type. Since the negative bevel structure 11 and the protruding portion of the second electrode 8 are used together, the depletion layer of the second conductivity type of the second conductivity type is formed. It is possible to obtain a high breakdown voltage semiconductor device in which the spread to the semiconductor region 3 side is suppressed, the electric field strength at a specific portion, for example, the nn + junction portion 14 does not rise extremely, and high reliability and high breakdown voltage characteristics are compatible with each other. The effect is that you can.

Further, even if the electric charge of the stabilizing film on the surface of the semiconductor substrate 1 is uneven, the electric field strength locally increases at the surface portion of the end face of the second semiconductor region 3 of the second conductivity type. This also has the effect of not deteriorating the high breakdown voltage characteristics of the semiconductor device.

The semiconductor device is the second conductivity type second
Between the second semiconductor region 3 of the second conductivity type and the second semiconductor region 3 of the second conductivity type.
Of the second conductivity type, the exposed end face 9 of the third semiconductor region 4 is
Of the second semiconductor region 3 of the conductivity type is formed so as to have a continuous negative bevel structure 11 on the exposed end face 9.
That the electric field strength of the end face 9 in the vicinity of the nn + junction 14 between the second semiconductor region 3 of the second conductivity type and the third semiconductor region 4 of the second conductivity type can be effectively suppressed. There is also.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the configuration of a first embodiment of a high breakdown voltage semiconductor device according to the present invention.

FIG. 2 is a characteristic diagram showing a distribution of electric field intensity in each part of the end surface 9 of the semiconductor substrate 1.

FIG. 3 is a cross-sectional view showing the configuration of a second embodiment of the high breakdown voltage semiconductor device according to the present invention.

FIG. 4 is a transverse sectional view showing the configuration of a third embodiment of the high breakdown voltage semiconductor device according to the present invention.

FIG. 5 is a transverse sectional view showing the configuration of a fourth embodiment of the high breakdown voltage semiconductor device according to the present invention.

FIG. 6 is a cross-sectional view showing the configuration of a fifth embodiment of the high breakdown voltage semiconductor device according to the present invention.

FIG. 7 is a cross-sectional view showing the configuration of a sixth embodiment of the high breakdown voltage semiconductor device according to the present invention.

[Explanation of symbols]

1 semiconductor substrate 2 p-type (first conductivity type) high impurity concentration first semiconductor region 3 n-type (second conductivity type) second semiconductor region 4 n-type (second conductivity type) High impurity concentration third semiconductor region 5 First major surface of semiconductor substrate 1 Second major surface of semiconductor substrate 1 Anode electrode 8 Cathode electrode 9 End face 10 of semiconductor substrate 1 Positive bevel structure of end face 9 Part 11 Negative bevel structure part of end face 9 12 Turning point of bevel structure 13 pn junction 14 nn + junction 15 p conductive type semiconductor emitter region 16 n type semiconductor emitter region 17 gate electrode 18 n type fourth Semiconductor region 19 nn-junction 20 Attached electrode

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location 9171-4M H01L 29/80 V (72) Inventor Yasuhiro Mochizuki 7-1 Omika-cho, Hitachi-shi, Ibaraki No. 1 Hitachi, Ltd. Hitachi Research Laboratory

Claims (5)

[Claims] 1. A high-impurity concentration first semiconductor region of at least a first conductivity type and a second semiconductor region of a second conductivity type, the first semiconductor region and the second semiconductor region. Form a pn junction and have an exposed end face, a first electrode provided on the surface of the first semiconductor region, and a second electrode provided on the surface of the second semiconductor region. In the high breakdown voltage semiconductor device having the electrode of, the exposed end surface of the semiconductor substrate has a positive bevel structure in the thickness direction including the pn junction, and has a remaining thickness of The portion is configured to have a negative bevel structure, the second electrode protrudes outward from the exposed end surface of the semiconductor region of the portion where the second electrode is provided, and the length including the protruding portion is the first electrode. Equal to the longest width between the end faces of the semiconductor region A high breakdown voltage semiconductor device characterized in that it is configured to be slightly longer than that. 2. A third semiconductor region of the second conductivity type having a higher impurity concentration than the second semiconductor region is provided between the second semiconductor region and the second electrode, and Third
2. The high breakdown voltage semiconductor device according to claim 1, wherein the exposed end face of the semiconductor region has a negative bevel structure continuous with the exposed end face of the second semiconductor region. 3. A second impurity region between the second semiconductor region and the third semiconductor region, the impurity concentration being higher than that of the second semiconductor region and lower than that of the third semiconductor region. A fourth semiconductor region of conductivity type is provided, and the exposed end face of the fourth semiconductor region is a negative bevel structure together with the exposed end face of the second semiconductor region and the exposed end face of the third semiconductor region. The high breakdown voltage semiconductor device according to claim 2, further comprising: 4. An auxiliary electrode is formed on the second electrode, the auxiliary electrode protruding outward from the exposed end face, and the protruding length is the longest between the end faces of the first semiconductor. 4. The high breakdown voltage semiconductor device according to claim 1, wherein the high breakdown voltage semiconductor device is configured to be equal to or slightly longer than the width. 5. The position where the positive bevel structure provided on the end surface of the semiconductor substrate is converted to the negative bevel structure is a portion of the semiconductor substrate which is biased to the negative bevel structure. A high breakdown voltage semiconductor device according to any one of 1.