JP2003204065A - Semiconductor device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention can be applied to active elements such as MOSFET (insulated gate field effect transistor), IGBT (conductivity modulation type MOSFET) and bipolar transistor and passive elements such as diode, and has a high breakdown voltage. The present invention relates to a vertical power semiconductor device that achieves both high performance and large current capacity.

In a vertical semiconductor device having a vertical drift portion in which a current flows in the thickness direction of the substrate provided with electrode portions on both sides of the substrate, there is a trade-off relationship between on-resistance (current capacity) and withstand voltage. Since they exist, the vertical p-type regions are formed by alternately repeating vertical n-type regions and vertical p-type regions having an increased impurity concentration in the creeping direction of the substrate.
It is known to adopt an n structure. However, although the vertical drift portion of the parallel pn structure is depleted quickly, in the breakdown voltage structure portion where the current does not substantially flow around the drift portion, the depletion layer is difficult to spread outward or to the deep portion of the substrate, and the electric field strength is silicon. Since the critical electric field strength is reached quickly, the breakdown voltage is limited in the breakdown voltage structure portion. In order to obtain a designed breakdown voltage, it is desirable to use a vertical semiconductor device that employs a parallel pn structure also in the breakdown voltage structure portion.

FIG. 9 is a plan view showing a drift portion and an element outer peripheral portion (breakdown voltage structure portion) in a vertical MOSFET, and FIG.
9 is a vertical sectional view showing a state cut along the line AA 'in FIG. 9, and FIG. 11 is a vertical sectional view showing a state cut along the line BB' in FIG. In addition, in FIG. 9, 1/4 of the drift portion is shown by a hatched portion.

This n-channel vertical MOSFET has a backside
N of low resistance in which the drain electrode 18 of⁺Drain
The first layer formed on the in layer (contact layer) 11
Drain / drift section 22 of column pn structure and this drift
Of the device active region selectively formed on the surface layer of the gate portion 22.
High impurity concentration p base region (p well, channel region
Area) 13a and the surface side in the p base region 13a.
Selectively formed high impurity concentration n⁺Source region 14
And provided on the surface of the substrate via the gate insulating film 15.
A gate electrode layer 16 made of polysilicon or the like and an interlayer insulating film 19
through the contact hole formed in a to the p base region 13a and
And n⁺A source electrode that makes conductive contact across the source region 14.
Poles 17 and. Well-shaped p base region 13a
In n ⁺The source region 14 is shallowly formed, and 2
It constitutes a heavy diffusion type MOS part. Note that 26 is p⁺
Gate electrode in the contact region and in a portion not shown
A metal film gate line is in conductive contact with the layer 16.

The drain / drift portion 22 of the first parallel pn structure has a first layered vertical n-type region 22a oriented in the thickness direction of the substrate and a first layered vertical p-type oriented in the thickness direction of the substrate. This is a structure in which the regions 22b are alternately and repeatedly joined. The upper end is the interstitial region 12e of the p base region 13a.
The first layered vertical n-type region 22a which reaches the position is a substantial electric path region. First layered vertical n-type region 22a
Is in contact with the n ⁺ drain layer 11. The upper end of the first layered vertical p-type region 22b is in contact with the bottom surface of the well of the p base region 13a, and the lower end thereof is in contact with the n ⁺ drain layer 11.

The breakdown voltage structure portion 20 around the vertical drain / drift portion 22 between the substrate surface and the n ⁺ drain layer 11.
Also, the second layered vertical n-type regions 20a oriented in the thickness direction of the substrate and the second layered vertical p-type regions 20b oriented in the thickness direction of the substrate are alternately arranged in the creeping direction of the substrate. A second parallel pn structure formed by repeatedly joining is formed. An oxide film (insulating film) 23 made of a thermal oxide film or phosphor silica glass (PSG) is formed on the surface of the second parallel pn structure of the breakdown voltage structure portion 20 for surface protection and stabilization. There is. In the second parallel pn structure, the impurity concentration of the second parallel pn structure is lower than the impurity concentration of the first parallel pn structure or the second parallel pn structure is used in order to facilitate the expansion of the depletion layer. Of the first parallel pn structure is smaller than the repeating pitch P1 of the first parallel pn structure.

[0007]

However, the vertical MOSFETs shown in FIGS. 9 to 11 have the following problems.

That is, the first layered vertical n on the outermost side of the first parallel pn structure which is the drain / drift portion 22.
Since the second vertical layered p-type region 20bb at the innermost side of the second parallel pn structure having a different impurity concentration or a different repeating pitch is present around the mold region 22aa,
The charge balance between the n-type region 22aa and the p-type region 20bb is destroyed. Therefore, electric field concentration occurs near the surface X at the boundary between the first parallel pn structure and the second parallel pn structure, and the breakdown voltage is reduced. In such a structure, it is difficult to obtain the designed breakdown voltage, and the significance of providing the second parallel pn structure in the breakdown voltage structure portion 20 is lost.

In view of the above problems, an object of the present invention is to provide a withstand voltage structure portion in a semiconductor device having a second parallel pn structure as a withstand voltage structure portion around the drift portion which is the first parallel pn structure. The purpose of the present invention is to provide a semiconductor device capable of further increasing the withstand voltage and the large current by relaxing the surface electric field in the above.

[0010]

In order to solve the above problems, the basic structure of a semiconductor device according to the present invention is the first structure of a substrate.
First conductively connected to an element active portion formed on the main surface side
Intervening between the element active portion and the low resistance layer, the second electrode layer conductively connected to the first conductivity type low resistance layer formed on the second main surface side of the substrate, The drift current flows in the vertical direction in the on-state and is depleted in the off-state, and is interposed between the first main surface and the low resistance layer around the vertical drift part. In addition, the breakdown voltage structure portion is depleted in the off state. The vertical drift portion is formed by alternately repeating and joining first vertical first conductivity type regions oriented in the thickness direction of the substrate and first vertical second conductivity type regions oriented in the thickness direction of the substrate. It is a parallel pn structure. The breakdown voltage structure portion is formed by alternately and repeatedly joining second vertical first conductivity type regions oriented in the thickness direction of the substrate and second vertical second conductivity type regions oriented in the thickness direction of the substrate. It has two parallel pn structures. The impurity concentration of the second parallel pn structure is lower than the impurity concentration of the first parallel pn structure, and / or the repetition pitch of the second parallel pn structure is the repetition pitch of the first parallel pn structure. It is smaller than the pitch. The element active portion formed on the first main surface side of the substrate is, for example, in the case of a vertical MOSFET, a switching portion including a channel diffusion layer forming an inversion layer and a source region on the first main surface side, and a bipolar transistor. In the case of, it is a switching part including the emitter or collector region,
The active portion or the passive portion having a function of selecting conduction or non-conduction on the first main surface side of the drift portion.

In such a basic structure, the breakdown voltage structure portion around the drift portion in the present invention is not only composed of the second parallel pn structure, but the repeating pitch adjacent to the drift portion is 1 from the drift portion. It has an inner peripheral structure part which is a part of the first parallel pn structure extended outward by a pitch or more, and an outer peripheral structure part which is a second parallel pn structure adjacent to the inner peripheral structure part. For this reason,
There is no boundary between the first parallel pn structure and the second parallel pn structure in the adjacent peripheral portion of the drift part, and the boundary exists between the inner peripheral structure part and the outer peripheral structure part of the breakdown voltage structure part. Therefore, the charge balance of the parallel pn structure does not collapse in the outer peripheral portion adjacent to the drift portion, and therefore, the surface electric field in the outer peripheral portion adjacent to the drift portion can be suppressed and the breakdown voltage can be increased.

Further, according to the present invention, a field plate is formed on the insulating film on the first main surface of the breakdown voltage structure portion so as to cover the inner peripheral structure portion and have a tip protruding over the outer peripheral structure portion. As a result, the field plate overhangs for a long time, and the electric field concentrated portion immediately below the tip of the field plate deviates from the adjacent outer peripheral portion of the drift portion to become the outer peripheral structure portion, so that the surface electric field at the inner peripheral structure portion can be further suppressed, and the higher withstand voltage Can be realized.

At this time, if a sufficient withstand voltage is ensured by the insulating film, the withstand voltage share in the parallel pn structure portion under the insulating film becomes small. Then, even if the charge balance is broken at the boundary between the first and second parallel pn structures, the decrease in breakdown voltage due to the breakdown is compensated by the breakdown voltage held by the insulating film.
The element as a whole is not affected. Further, also in the breakdown voltage structure portion located outside the tip of the field plate, the concentration of the breakdown voltage is reduced, so that the concentration of the surface electric field can be suppressed. Therefore, in the present invention, by increasing the film thickness of the insulating film from the drift portion side toward the outer peripheral structure portion side, high breakdown voltage can be achieved.

It is desirable that this insulating film has a film thickness that gradually increases from the drift portion side toward the outer peripheral structure portion side. However, since it is difficult to form such an insulating film, the insulating film is formed gradually thicker from the drift portion side to the outer peripheral structure side. In the design withstand voltage of 700 V class, it is desirable that the number of film thickness steps of the insulating film is two or more.
However, since a step is formed on the field plate at the portion where the film thickness changes abruptly, electric field concentration occurs directly under the step.

In order to solve this problem, according to the present invention, the first vertical second type among the first parallel pn structures of the inner peripheral structure portion is used.
The position on the first main surface side of the pn junction surface having the conductivity type region on the outside and the step position of the field plate are matched. The first vertical second conductivity type region is in a potential floating state,
Since the first vertical second conductivity type region is outside the first vertical first conductivity type region, the equipotential line on the high potential side among the equipotential lines approaching each other on the first main surface side is the first It is distributed to the outside of the vertical second conductivity type region. Therefore, the concentration of equipotential lines immediately below the step of the field plate is eliminated, the electric field concentration can be effectively alleviated, and a high breakdown voltage can be achieved.

As described above, the electric field concentration due to the collapse of the charge balance at the boundary between the first parallel pn structure and the second parallel pn structure and the electric field concentration just below the step of the field plate can be alleviated, but the outer periphery of the breakdown voltage structure portion. It is also necessary to mitigate the electric field concentration that occurs just below the tip of the field plate in the structure. For example, the second parallel p in the outer peripheral structure portion
It is also possible to form a high-resistance layer of the first conductivity type on the first principal surface side of the n structure and form a second conductivity type guard ring on the first principal surface side of the n-structure. Then, instead of forming a regular guard ring, the first main surface side position of the pn junction surface having the second vertical second conductivity type region on the outside of the second parallel pn structure and the tip position of the field plate. And are matched. The second vertical second conductivity type region is in a potential floating state, but since the second vertical second conductivity type region is outside the second vertical first conductivity type region, on the first main surface side. The equipotential lines on the high potential side among the equipotential lines that approach each other are distributed to the outside of the second second conductivity type region. For this reason, the concentration of equipotential lines immediately below the tip of the field plate can be eliminated, electric field concentration can be relieved, and high breakdown voltage can be achieved.

The first pn junction surface having the tip of the field plate and the second vertical second conductivity type region on the outer side.
The configuration in which the position on the main surface side is matched is effective even for the pressure resistant structure portion having no inner peripheral structure.

It is also necessary to relax the surface electric field in the breakdown voltage structure portion located outside the tip of the field plate. The present invention relates to a second vertical type second structure which is located outside the tip of the field plate in the second parallel pn structure.
The impurity concentration on the first main surface side of the conductivity type region is higher than the impurity concentration on the first main surface side of the adjacent second vertical first conductivity type region. Even if the first main surface side of the second vertical first conductivity type region is void, the adjacent second vertical second
The first major surface side of the conductivity type region is not completely vacant, and some carriers remain as the second conductivity type region, which functions as a guard ring, and the second vertical second conductivity type region is formed. Since it is outside the second vertical first conductivity type region,
The equipotential lines on the high potential side among the equipotential lines that are close to each other on the main surface side are distributed to the outside of the second second conductivity type region. Therefore, the surface electric field in the breakdown voltage structure portion located outside the tip of the field plate is relaxed, and the breakdown voltage can be increased.

As described above, the first of the second second conductivity type region is formed.
In order to make the main surface side function as a guard ring, the second
The width dimension of the vertical second conductivity type region on the first main surface side may be wider than the width dimension of the adjacent second vertical first conductivity type region on the first main surface side. The impurity concentration on the first main surface side of the second vertical first conductivity type region may be lower than the impurity concentration on the first main surface side of the adjacent second second conductivity type region. Note that the structure for relaxing the surface electric field in the breakdown voltage structure portion located outside the tip of the field plate is as follows.
It is effective even if the pressure-resistant structure portion does not have an inner peripheral structure.

The direction of the repeating pitch in the first parallel pn structure and the direction of the repeating pitch in the second parallel pn structure are not limited to the same direction, but may be substantially orthogonal to each other.

By providing the first conductivity type surrounding area surrounding the outer peripheral structure portion and the third electrode portion in conductive contact with the first main surface side, the leakage current can be suppressed.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. In the following, in layers and regions prefixed with n or p, it is meant that electrons or holes are majority carriers, respectively. Further, + means that the impurity concentration is relatively high.
Although n is selected as the first conductivity type and p is selected as the second conductivity type in all of the embodiments, the opposite case is also possible.

[Embodiment 1] FIG. 1 is a schematic plan view showing a chip of a vertical MOSFET device according to Embodiment 1 of the present invention, and FIG. 2 shows a state cut along the line AA 'in FIG. FIG. Note that FIG. 1 shows 1/4 of the drain / drift portion.

The vertical MOSFET of this example has a backside drain.
N having a low resistance in which the electrode 18 is in conductive contact⁺Drain layer
First parallel pn formed on (contact layer) 11
The drain / drift part 22 of the structure and this drain / drift part
An element active region selectively formed on the surface layer of the lift portion 22.
Area of high impurity concentration p base region (p well) 13a
And selectively formed on the surface side in the p base region 13a.
N of high impurity concentration ⁺Source region 14 and substrate surface
Polysilicon provided on the surface through the gate insulating film 15
And the gate electrode layer 16 such as an insulating film and the interlayer insulating film 19a.
P base regions 13a and n through the contact holes⁺So
The source electrode 17 that is in conductive contact across the source region 14.
Have N in the well-shaped p base region 13a
⁺The source region 14 is shallowly formed, and is a double diffusion type.
It constitutes the MOS section. Note that 26 is p⁺Contact
Of the gate electrode layer 16 in a region not shown.
The metal film gate wiring is in conductive contact therewith.

The drain / drift portion 22 is a device activation region.
Corresponding to the area directly under the p-base region 13 of a plurality of wells
And the first layered vertical n-type region oriented in the thickness direction of the substrate.
The first layer-shaped vertical layer oriented in the thickness direction of the region 22a and the substrate.
Repeating the p-type region 22b with the pitch P1
First parallel pn structure formed by alternately and repeatedly joining
Is. One of the first n-type regions 22a has an upper end
Reaches the interstitial region 12e of the p base region 13 and its lower end
Is n⁺It is in contact with the drain layer 11. Hama area 12e
The first n-type region 22a reaching the
However, the remaining first n-type region 22a is almost a non-electric path.
It has become an area. In addition, the first p-type region 22b is
The upper end is in contact with the bottom surface of the well of the p base region 13a,
The edge is n⁺ It is in contact with the drain layer 11.

Around the drain / drift unit 22, a parallel p
The breakdown voltage structure portion (element peripheral portion) is composed of the n structure, but this breakdown voltage structure portion is adjacent to the first parallel pn structure of the drain / drift portion 22 and has the same repeating pitch and the same impurity concentration. The circumferential structure portion 30 and the inner circumferential structure portion 3
Peripheral structure portion 40 that is a second parallel pn structure adjacent to 0
Have and. The repeating pitch of the first parallel pn structure belonging to the inner peripheral structure portion 30 is several pitches. The second parallel pn structure belonging to the outer peripheral structure portion 40 has a layered vertical second n-type region 41 oriented in the thickness direction of the substrate and a layered vertical second p-type region 42 oriented in the substrate thickness direction. And are joined alternately. In this example, the second parallel pn
The impurity concentration of the second parallel pn structure is lower than the impurity concentration of the first parallel pn structure, and the repetition pitch P2 of the second parallel pn structure is first It is narrower than the repeating pitch P1 of the parallel pn structure. However, it is needless to say that it is possible to easily expand the depletion layer in the second parallel pn structure only by satisfying one of the conditions.

An oxide film (insulating film) 123 is formed on the main surface of the insulating film on the surfaces of the inner peripheral structure portion 30 and the outer peripheral structure portion 40. The oxide film 123 has a film thickness of the drift portion 22.
It is formed so that it becomes thicker from the outer peripheral structure part 40 to the outer peripheral structure part 40, and becomes thicker stepwise on the inner peripheral structure part 30. That is, the oxide film 123 includes an inner region oxide film 123 a having a minimum thickness formed on the inner structure portion 30 adjacent to the drift portion 22 and an intermediate region oxide film formed on the inner structure portion 30. From the top of the membrane 123b and the inner peripheral structure 30 to the outer peripheral structure 4
The outer peripheral region oxide film 123c having the maximum thickness formed over 0 is integrally formed, and the number of film thickness steps is two. And
The oxide film 12 extending from the source electrode 17 in the breakdown voltage structure portion
3, the inner peripheral structure portion 30 is covered with the tip of the outer peripheral structure portion 4
A field plate FP is formed so as to extend to above 0. This field plate FP is an oxide film 1
It has steps S1 and S2 reflecting the step of No. 23. A step between the inner region oxide film 123a and the middle region oxide film 123b,
That is, the step S1 of the field plate FP is the first part of the first parallel pn structure belonging to the inner peripheral structure portion 30.
It coincides with the surface side position T1 of the pn junction surface having the p-type region 22b on the outside. Further, the step between the intermediate oxide film 123b and the outer oxide film 123c, that is, the step S2 of the field plate FP is the second p-type region in a part of the first parallel pn structure belonging to the inner peripheral structure portion 30. It coincides with the surface side position T2 of the pn junction surface having 22b on the outside. Further, the tip S3 of the field plate FP is connected to the second parallel p
In the n structure, it coincides with the surface side position T3 of the pn junction surface having the second p-type region 42 on the outside.

An n-type surrounding region 50 is formed as a channel stopper outside the outer peripheral structure 40, and a stopper electrode 51 is in conductive contact with the surface side of the n-type surrounding region 50.

The vertical MOSFET of this example has a breakdown voltage of 600 V class, and the impurity concentration of the n ⁺ drain layer 11 is 2 ×.
10 ¹⁸ cm ⁻³ , first n-type region 22a and first p
The impurity concentration of the mold region 22b is 2.57 × 10 ¹⁵ cm
^-3 , the substrate depth (thickness) is 44 μm, the first repeating pitch P1 is 16 μm, and the second p-type region 4 is
The impurity concentration of the first and second p-type regions 42 is 1.2 × 10
^{At 15} cm ⁻³ , the substrate depth (thickness) is 44 μm, and the second repeating pitch P2 is 8 μm. Oxide film 123
The inner peripheral oxide film 123a has a thickness of 0.1 μm, the intermediate oxide film 123b has a thickness of 0.8 μm, and the outer peripheral oxide film 123 has a thickness of 0.8 μm.
The film thickness of c is 3.0 μm.

As described above, the breakdown voltage structure portion around the drain / drift portion 22 is not limited to the outer peripheral structure portion 40, which is the second parallel pn structure, but the drain / drift portion 22 and the outer peripheral structure portion 40. In the meantime, adjacent to the drain / drift portion 22, there is an inner peripheral structure portion 30 which is a part of the first parallel pn structure in which the repeating pitch is continuously extended from the drift portion to the outside by one pitch or more. Therefore, the first peripheral portion of the drain / drift portion 22 is adjacent to the first peripheral portion.
The surface position of the boundary between the parallel pn structure and the second parallel pn structure does not exist, and the surface position T4 of the boundary is the inner peripheral structure portion 3
0 and the outer peripheral structure 40. In the outer peripheral portion T5 adjacent to the drain / drift portion 22, parallel pn
The charge balance of the structure is not disturbed, and therefore, the surface electric field at the adjacent outer peripheral portion of the drain / drift portion can be suppressed and the breakdown voltage can be increased.

Further, since the tip S3 of the field plate FP extends over the inner circumferential structure portion 30 and extends over the outer circumferential structure portion 40, the electric field concentrated portion immediately below the tip end S3 of the field plate FP is the drain / drift portion 22. Since the outer peripheral structure portion 40 is separated from the adjacent outer peripheral portion, the surface electric field in the inner peripheral structure portion 30 can be further suppressed, and the breakdown voltage can be further increased.

At this time, if the breakdown voltage is sufficiently secured by the oxide film 123, the breakdown voltage sharing in the parallel pn structure portion below the oxide film 123 becomes small. Then, if the first and second parallel p
Even if the charge balance is lost at the boundary of the n structure, the decrease in breakdown voltage due to the breakdown is compensated for by the breakdown voltage held by the oxide film 123, so that the entire device is not affected. Further, also in the breakdown voltage structure portion located outside the tip S3 of the field plate FP, the concentration of the breakdown voltage is reduced, so that the concentration of the surface electric field can be suppressed. Therefore, by increasing the thickness of the oxide film 123 from the drift portion 22 side toward the outer peripheral structure portion 40 side, it is possible to increase the breakdown voltage.

However, since the oxide film 123 is formed thicker stepwise, the field plate FP has steps S1 and S2 at a portion where the film thickness suddenly changes. In order to solve this problem, the step S1 of the field plate FP includes the first step S1 belonging to the inner peripheral structure portion 30.
First p-type region 22b of a portion of the parallel pn structure of
Corresponding to the position T1 on the front surface side of the pn junction surface having the outside, and the step S2 of the field plate FP is located outside the second p-type region 22b in a part of the first parallel pn structure belonging to the inner peripheral structure portion 30. It coincides with the position T2 on the front surface side of the pn junction surface held in. The first p-type region 22b is almost in a floating state, but the first p-type region 22b is the first N-type region 22.
Since it is outside a, the equipotential lines on the high potential side among the equipotential lines that are close to each other on the surface side are the first p-type region 22b.
To the outside of. Therefore, the field plate F
The concentration of equipotential lines immediately below the steps S1 and S2 of P is eliminated, electric field concentration can be effectively mitigated, and high breakdown voltage can be achieved.

As described above, the electric field concentration due to the collapse of the charge balance at the boundary between the first parallel pn structure and the second parallel pn structure and the electric field concentration immediately below the steps S1 and S2 of the field plate FP can be relaxed, but the breakdown voltage is reduced. It is also necessary to reduce the electric field concentration that occurs in the outer peripheral structure 40 of the structure just below the tip S3 of the field plate FP. In this example, instead of forming a regular guard ring on the front surface side of the outer peripheral structure portion 40, the first main surface of the pn junction surface of the second parallel pn structure having the second p-type region 42 on the outer side. The side position T3 and the tip position S3 of the field plate FP are matched. The second p-type region 42 is in a potential floating state,
Since the second p-type region 42 is outside the second n-type region 41, the equipotential lines on the high potential side of the equipotential lines that are close to each other on the surface side are outside the second p-type region 42. Sort to. Therefore, the concentration of equipotential lines immediately below the tip S3 of the field plate FP is eliminated, the electric field concentration can be alleviated, and a high breakdown voltage can be achieved.

Further, in this example, since the n-type surrounding region 50 surrounding the outer peripheral structure portion 40 and the stopper electrode 51 are formed, the leakage current can be suppressed.

[Embodiment 2] FIG. 3 is a partial vertical sectional view showing a vertical MOSFET according to Embodiment 2 of the present invention. FIG. 3 is a longitudinal sectional view showing a state similarly cut along the line AA ′ in FIG.

In this example, the difference from the configuration of the first embodiment is that in the second parallel pn structure of the outer peripheral structure 40, the second p-type region 42 located outside the tip of the field plate FP is the surface. The second side portion 42a has a side portion 42a. The surface side portion 42a has a higher impurity concentration than that of the adjacent second n-type region 41 and has a width dimension adjacent to the second n portion. It is wider than the width dimension of the mold region 41 on the front surface side. In other words, the surface-side portion 42a has the impurity concentration of the second p-type region 42.
Of the second p-type region 42 adjacent to the second p-type region 42 adjacent thereto.
Although the front surface side portion 42a has a high impurity concentration and a wide width, it may be formed on either side.

In the off state, even if the surface side of the second n-type region 41 is vacant, the adjacent surface side portion 42a is not completely vacant, and some carriers remain as the p-type region. This functions as a guard ring, and distributes the equipotential lines on the high potential side among the equipotential lines approaching each other on the surface side to the outside of the surface side portion 42a. Therefore, the pressure-resistant structure portion 4 located outside the tip of the field plate FP.
The surface electric field at 0 is relaxed, and high breakdown voltage can be achieved.

[Embodiment 3] FIG. 4 is a schematic plan view showing a chip of a vertical MOSFET device according to Embodiment 3 of the present invention, and FIG. 5 shows a state cut along the line AA 'in FIG. FIG. Note that FIG. 4 shows 1/4 of the drain / drift portion.

In this example, the difference from the configuration of Example 1 is that the repeating pitch P2 of the second parallel pn structure of the outer structure 40 is the same as the repeating pitch P1 of the first parallel pn structure. The impurity concentration of the second parallel pn structure is sufficiently lower than the impurity concentration of the first parallel pn structure. If the impurity concentration of the second parallel pn structure is sufficiently lower than the impurity concentration of the first parallel pn structure, the repeating pitch P2 may be wider than the repeating pitch P1.

Further, in the present embodiment, the second outer pressure-resistant portion 40 is located outside the tip of the field plate FP.
The impurity concentration of the surface side portion 41a of the n-type region 41 is lower than the impurity concentration of the adjacent second p-type region 42 on the surface side. Even in such a case, even if the surface side portion 41a of the second n-type region 41 is vacant in the off state, the surface side of the adjacent second p-type region 42 is not completely vacant, and p Since some carrier remains as the mold area,
This functions as a guard ring, and among the equipotential lines that are close to each other on the surface side, the equipotential lines on the high potential side are distributed to the outside of the surface side portion of the second p-type region 42. For this reason, the surface electric field in the breakdown voltage structure portion 40 located outside the tip of the field plate FP is relaxed, and a high breakdown voltage can be achieved.

As described above, in this example, it is not necessary to form the second side-by-side pn structure as wide as the surface side portion 42a of the second p-type region 42, and the adjustment of impurities is sufficient.
The impurity introduction mask can be reduced. The impurity concentration of the surface side portion of the second p-type region 42 may be higher than the impurity concentration of the surface side portion of the second n-type region 41.

[Embodiment 4] FIG. 6 is a schematic plan view showing a chip of a vertical MOSFET device according to Embodiment 4 of the present invention, and FIG. 7 shows a state cut along the line AA 'in FIG. FIG. 8 is a vertical sectional view showing a state of being cut along the line BB ′ in FIG.

In the first embodiment, the direction of the repeating pitch P1 in the first parallel pn structure is the same as the direction of the repeating pitch P2 in the second parallel pn structure. The direction of the repeating pitch P1 in the pn structure and the direction of the repeating pitch P2 in the second parallel pn structure are orthogonal to each other. That is, the planar stripes of the first parallel pn structure and the planar stripes of the second parallel pn structure are orthogonal to each other. Even if the stripe direction changes, there is no difference in that the breakdown voltage can be maintained when the reverse voltage is applied and the breakdown voltage can be maintained. Even if the charge balance at the transition of the stripe direction is lost, the inner breakdown voltage portion 3
Since 0 exists, high breakdown voltage can be achieved.

In the present invention, the above embodiment is based on the vertical MOS.
Although the FET element has been described, it goes without saying that it can be applied to general semiconductor devices having a vertical drift portion.

[0046]

As described above, in the present invention,
The withstand voltage structure portion around the drift portion includes an inner peripheral structure portion which is a portion of a first parallel pn structure in which a repeating pitch is continuously extended from the drift portion to the outside by one pitch or more adjacent to the drift portion, and the inner peripheral structure portion. It has a second parallel pn structure and an outer peripheral structure part adjacent to the structure part. Therefore, the first parallel p structure is provided in the peripheral portion adjacent to the drift part.
Since there is no boundary between the n structure and the second parallel pn structure, and the boundary exists between the inner peripheral structure part and the outer peripheral structure part of the breakdown voltage structure part, in the outer peripheral part adjacent to the drift part. The charge balance of the parallel pn structure does not collapse, and therefore, the surface electric field at the adjacent outer peripheral portion of the drift portion can be suppressed, and high breakdown voltage and large current can be achieved.

[Brief description of drawings]

FIG. 1 is a schematic plan view showing a chip of a vertical MOSFET device according to a first embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view showing a state cut along line AA ′ in FIG.

FIG. 3 is a partial vertical sectional view showing a vertical MOSFET according to a second embodiment of the present invention.

FIG. 4 is a schematic plan view showing a chip of a vertical MOSFET device according to a third embodiment of the present invention.

5 is a vertical cross-sectional view showing a state cut along the line AA 'in FIG.

FIG. 6 is a schematic plan view showing a chip of a vertical MOSFET device according to a fourth embodiment of the present invention.

FIG. 7 is a vertical cross-sectional view showing a state cut along the line AA ′ in FIG.

FIG. 8 is a vertical cross-sectional view showing a state of being cut along the line BB ′ in FIG.

FIG. 9 is a plan view showing a drift portion and an element outer peripheral portion (breakdown voltage structure portion) in a vertical MOSFET.

10 is a vertical cross-sectional view showing a state of being cut along the line AA ′ in FIG.

FIG. 11 is a vertical cross-sectional view showing a state cut along the line BB ′ in FIG. 9.

[Explanation of symbols]

11 ... n ⁺ drain layer (contact layer) 12e ... interleaved region 13a ... p base region (p well) 14 ... n ⁺ source region 15 ... gate insulating film 16 ... gate electrode layer 17 ... source electrode 18 ... drain electrode 19a ... interlayer Insulating film 22 ... Drain / drift part 22a ... First n-type region 22b ... First p-type region 26 ... P ⁺ contact region 30 ... Inner peripheral structure part 40 ... Outer peripheral structure part 41 ... Second n-type region 41a , 42a ... Surface-side portion 42 ... Second p-type region 50 ... N-type surrounding region 51 ... Stopper electrode 123 ... Oxide film 123a ... Inner region oxide film 123b ... Intermediate region oxide film 123c ... Outer region oxide film P1 ... Repeat pitch P2 of one parallel pn structure ... Repeat pitch FP of second parallel pn structure ... Field plates S1, S2 ... Step S3 ... Tip of field plate T1 to T5 Surface-side position of the pn junction surface

Claims (19)

[Claims] 1. A first electrode layer conductively connected to an element active portion formed on a first main surface side of a substrate, and a second electrode layer of the substrate.
The second electrode layer formed on the main surface side and conductively connected to the low-resistance layer of the first conductivity type is interposed between the element active portion and the low-resistance layer. Flowing in the direction and depleted in the off state, and interposed between the first main surface and the low resistance layer around the vertical drift part, and in the on state, it is a non-electric path region and is off. The vertical drift portion is oriented in the thickness direction of the substrate.
Of the first parallel type pn structure in which the first vertical conductivity type regions and the first vertical second conductivity type regions oriented in the thickness direction of the substrate are alternately and repeatedly joined, and the breakdown voltage structure portion is A second vertical first conductivity type region oriented in the thickness direction of the substrate and a second vertical second region oriented in the thickness direction of the substrate.
It has a second parallel pn structure formed by alternately repeating and joining conductive type regions, and the impurity concentration of the second parallel pn structure is lower than the impurity concentration of the first parallel pn structure. In the semiconductor device, the breakdown voltage structure portion is an inner peripheral structure portion that is adjacent to the drift portion and is a part of the first parallel pn structure in which a repeating pitch is continuously extended outward from the drift portion by one pitch or more, A semiconductor device having an outer peripheral structure part that is the second parallel pn structure adjacent to the inner peripheral structure part. 2. A first electrode layer conductively connected to an element active portion formed on the first main surface side of the substrate, and a second electrode layer of the substrate.
The second electrode layer formed on the main surface side and conductively connected to the low-resistance layer of the first conductivity type is interposed between the element active portion and the low-resistance layer, and a drift current is vertically generated in the ON state. Flowing in the direction and depleted in the off state, and interposed between the first main surface and the low resistance layer around the vertical drift part, and in the on state, it is a non-electric path region and is off. The vertical drift portion is oriented in the thickness direction of the substrate.
Of the first parallel type pn structure in which the first vertical conductivity type regions and the first vertical second conductivity type regions oriented in the thickness direction of the substrate are alternately and repeatedly joined, and the breakdown voltage structure portion is A second vertical first conductivity type region oriented in the thickness direction of the substrate and a second vertical second region oriented in the thickness direction of the substrate.
A second parallel pn structure is formed by alternately and repeatedly joining conductive type regions, and the repeating pitch of the second parallel pn structure is smaller than the repeating pitch of the first parallel pn structure. In the semiconductor device, the breakdown voltage structure portion is an inner peripheral structure portion that is adjacent to the drift portion and is a part of the first parallel pn structure in which a repeating pitch is continuously extended outward by one pitch or more from the drift portion, A semiconductor device having an outer peripheral structure part that is the second parallel pn structure adjacent to the inner peripheral structure part. 3. The insulating film is formed on the first main surface of the pressure-resistant structure portion, and the tip covers the inner peripheral structure portion on the insulating film. A semiconductor device having a field plate formed so as to extend above the peripheral structure portion. 4. The semiconductor device according to claim 3, wherein the insulating film has a film thickness that increases from the drift portion side toward the outer peripheral structure portion side. 5. The semiconductor device according to claim 4, wherein the insulating film has a film thickness that gradually increases from the drift portion side toward the outer peripheral structure portion side. 6. The semiconductor device according to claim 5, wherein the number of steps of film thickness of the insulating film is 2 or more. 7. The pn junction surface according to claim 5 or 6, wherein the first vertical second conductivity type region is provided outside of a portion of the first parallel pn structure belonging to the inner peripheral structure portion. The semiconductor device, wherein the position on the first main surface side and the step position of the field plate are matched. 8. The first main pn junction surface according to claim 3, wherein the second vertical pn junction surface of the second parallel pn structure has the second vertical second conductivity type region outside. A semiconductor device, wherein a surface side position and a tip position of the field plate coincide with each other. 9. The second vertical second conductivity type region according to any one of claims 3 to 8, wherein the second vertical second conductivity type region is located outside the tip of the field plate in the second parallel pn structure. The semiconductor device is characterized in that the impurity concentration on the first main surface side is higher than the impurity concentration on the first main surface side of the adjacent second vertical first conductivity type region. 10. The second vertical second conductivity type region according to any one of claims 3 to 8, wherein the second vertical second conductivity type region is located outside the tip of the field plate in the second parallel pn structure. The semiconductor device is characterized in that the width dimension on the first main surface side is wider than the width dimension on the first main surface side of the adjacent second vertical first conductivity type regions. 11. The second vertical first conductivity type region according to any one of claims 3 to 8, wherein the second vertical first conductivity type region is located outside the tip of the field plate in the second parallel pn structure. The semiconductor device is characterized in that the impurity concentration on the first main surface side is lower than the impurity concentration on the first main surface side of the adjacent second second conductivity type region. 12. The semiconductor device according to claim 1, wherein the first parallel pn structure and the second parallel pn structure are planar stripes. 13. The repetitive pitch direction in the first parallel pn structure and the repetitive pitch direction in the second parallel pn structure are substantially orthogonal to each other according to any one of claims 1 to 12. A semiconductor device characterized in that 14. The semiconductor device according to claim 1, further comprising a first conductivity type surrounding region surrounding the outer peripheral structure portion. 15. The semiconductor device according to claim 14, further comprising a third electrode portion that is in conductive contact with a side of the first main surface of the first conductivity type surrounding area. 16. A first conductive layer formed on the first main surface side of the substrate and conductively connected to an element active portion, and a first conductivity type low layer formed on the second main surface side of the substrate. A second electrode layer that is conductively connected to the resistance layer; and a vertical drift portion that is interposed between the element active portion and the low resistance layer and that has a drift current flowing in the vertical direction in the on state and depleted in the off state. A breakdown voltage structure portion that is interposed between the first main surface and the low resistance layer around the vertical drift portion and that is substantially a non-electric path region in an on state and is depleted in an off state, The vertical drift portion has a first orientation oriented in the thickness direction of the substrate.
And a first parallel pn structure formed by alternately and repeatedly joining the vertical first conductivity type drift regions and the first vertical second conductivity type partition regions oriented in the thickness direction of the substrate.
The breakdown voltage structure portion is formed by alternately and repeatedly joining second vertical first conductivity type regions oriented in the thickness direction of the substrate and second vertical second conductivity type regions oriented in the thickness direction of the substrate. It has a second parallel pn structure,
In a semiconductor device having a field plate formed on an insulating film on a main surface, a second pn junction surface having the second vertical second conductivity type region on the outside of the second parallel pn structure is provided. 1. A semiconductor device characterized in that the position on the main surface side and the position of the tip of the field plate coincide with each other. 17. A first conductive layer formed on the first main surface side of the substrate and conductively connected to an element active portion, and a first conductivity type low layer formed on the second main surface side of the substrate. A second electrode layer that is conductively connected to the resistance layer; and a vertical drift portion that is interposed between the element active portion and the low resistance layer and that has a drift current flowing in the vertical direction in the on state and depleted in the off state. A breakdown voltage structure portion that is interposed between the first main surface and the low resistance layer around the vertical drift portion and that is substantially a non-electric path region in an on state and is depleted in an off state, The vertical drift portion has a first orientation oriented in the thickness direction of the substrate.
And a first parallel pn structure in which the vertical first conductivity type drift regions and the first vertical second conductivity type partition regions oriented in the thickness direction of the substrate are alternately and repeatedly joined.
The breakdown voltage structure portion is formed by alternately and repeatedly joining second vertical first conductivity type regions oriented in the thickness direction of the substrate and second vertical second conductivity type regions oriented in the thickness direction of the substrate. It has a second parallel pn structure,
In a semiconductor device having a field plate formed on an insulating film on a main surface, in the second parallel pn structure, the second vertical second conductive member located outside an end of the field plate. A semiconductor device, wherein the impurity concentration on the first main surface side of the type region is higher than the impurity concentration on the first main surface side of the adjacent second vertical first conductivity type region. 18. A first conductive layer formed on the side of the first main surface of the substrate and conductively connected to an element active portion, and a first conductivity type low layer formed on the side of the second main surface of the substrate. A second electrode layer that is conductively connected to the resistance layer; and a vertical drift portion that is interposed between the element active portion and the low resistance layer and that has a drift current flowing in the vertical direction in the on state and depleted in the off state. A breakdown voltage structure portion that is interposed between the first main surface and the low resistance layer around the vertical drift portion and that is substantially a non-electric path region in an on state and is depleted in an off state, The vertical drift portion has a first orientation oriented in the thickness direction of the substrate.
And a first parallel pn structure formed by alternately and repeatedly joining the vertical first conductivity type drift regions and the first vertical second conductivity type partition regions oriented in the thickness direction of the substrate.
The breakdown voltage structure portion is formed by alternately and repeatedly joining second vertical first conductivity type regions oriented in the thickness direction of the substrate and second vertical second conductivity type regions oriented in the thickness direction of the substrate. It has a second parallel pn structure,
In a semiconductor device having a field plate formed on an insulating film on a main surface, in the second parallel pn structure, the second vertical second conductive member located outside an end of the field plate. A semiconductor device, wherein the width dimension of the first main surface side of the mold region is wider than the width dimension of the adjacent second vertical first conductivity type region on the first main surface side. 19. A first electrode layer conductively connected to an element active portion formed on a first main surface side of a substrate, and a first conductivity type low layer formed on a second main surface side of the substrate. A second electrode layer that is conductively connected to the resistance layer; and a vertical drift portion that is interposed between the element active portion and the low resistance layer and that has a drift current flowing in the vertical direction in the on state and depleted in the off state. A breakdown voltage structure portion that is interposed between the first main surface and the low resistance layer around the vertical drift portion and that is substantially a non-electric path region in an on state and is depleted in an off state, The vertical drift portion has a first orientation oriented in the thickness direction of the substrate.
And a first parallel pn structure formed by alternately and repeatedly joining the vertical first conductivity type drift regions and the first vertical second conductivity type partition regions oriented in the thickness direction of the substrate.
The breakdown voltage structure portion is formed by alternately and repeatedly joining second vertical first conductivity type regions oriented in the thickness direction of the substrate and second vertical second conductivity type regions oriented in the thickness direction of the substrate. It has a second parallel pn structure,
In a semiconductor device having a field plate formed on an insulating film on a main surface, the second vertical first conductive member located outside the tip of the field plate in the second parallel pn structure. A semiconductor device, wherein the impurity concentration on the first main surface side of the type region is lower than the impurity concentration on the first main surface side of the adjacent second second conductivity type region.