Semiconductor device

Abstract

To relax the electric field concentration at the end part of a field plate 7 provided on a termination area 102 and increase the withstand voltage.SOLUTION: A semiconductor device 100 having an active area 101 having a semiconductor element and a termination area 102 surrounding the active area 101. The termination area 102 has a first conductive type drift layer 1, a second conductive type field limiting layer 3 formed on a portion of the surface of the drift layer 1, a field insulating film 8 covering the drift layer 1 and the field limiting layer 3, and a field plate 7 electrically connected to the field limiting layer 3. The field plate 7 is formed on the surface of the field insulating film 8 so as to extend to the outside of the field limiting layer 3. The field insulating film 8 is thicker in the area overlapping the field plate 7 as it approaches the end part of the field plate 7.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a semiconductor device.

Background Art

[0002] In a semiconductor device, in order to ensure breakdown voltage, a structure for relaxing an electric field is provided in a termination region. As an example, there is one that uses a field limiting layer and a field plate electrically connected to the field limiting layer. The field plate is formed to extend outside the end of the field limiting layer in order to avoid electric field concentration at the end of the field limiting layer.

[0003] Examples of those disclosing such technology include FIGS. 1 and 2 of Patent Document 1.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The longer the distance between the end of the field limiting layer and the end of the field plate, the stronger the electric field relaxation effect by the field plate at the end of the field limiting layer.

[0006] However, the longer this distance, the smaller the radius of curvature of the equipotential line that wraps around the end of the field plate, so that the electric field is likely to concentrate at the end of the field plate, resulting in a problem of a decrease in breakdown voltage.

[0007] The problem to be solved by the present invention is to provide a semiconductor device that can alleviate the electric field concentration at the end of the field plate provided in the termination region and increase the breakdown voltage.

Means for Solving the Problem

[0008] In order to solve the above-described problem, a semiconductor device of the present invention is a semiconductor device having an active region having a semiconductor element and a termination region surrounding the active region, wherein the termination region includes a drift layer of a first conductivity type, a field limiting layer of a second conductivity type formed on a part of the surface of the drift layer, a field insulating film covering the drift layer and the field limiting layer, and a field plate electrically connected to the field limiting layer, the field plate is formed to extend to the outside of the field limiting layer on the surface of the field insulating film, and the field insulating film is characterized in that the thickness thereof increases as it approaches the end of the field plate in a region overlapping the field plate.

Effect of the Invention

[0009] According to the semiconductor device of the present invention, the electric field concentration at the end of the field plate provided in the termination region can be alleviated, and the breakdown voltage can be increased.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each figure and each embodiment, the same or similar components are denoted by the same reference numerals, and redundant descriptions are omitted.

Embodiment

[0012] FIG. 1 is a top view of the semiconductor device of Embodiment 1. FIG. 2 is a cross-sectional view taken along line A-A' of FIG. 1.

[0013] The semiconductor device 100 of the present embodiment includes an active region 101 having semiconductor elements and a termination region 102 surrounding the active region 101.

[0014] As the semiconductor elements, for example, an IGBT (Insulated Gate Bipolar Transistor), a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), a diode, etc. can be used. In the present embodiment, an example applied to an IGBT will be described.

[0015] In the present embodiment, the case where the first conductivity type is n-type and the second conductivity type is p-type will be described as an example for the conductivity type of the semiconductor layer. Note that the present invention is not limited to this, and the first conductivity type may be p-type and the second conductivity type may be n-type. Also, regarding the impurity concentration of the semiconductor layer, an example will be given for explanation, but the present invention is not limited to this, and it can be appropriately changed within the range where the intended operation in the embodiment can be realized.

[0016] The active region 101 includes a drift layer 1 of the first conductivity type, a well layer 2 of the second conductivity type, a first main electrode 5, a collector layer 9 of the second conductivity type, and a second main electrode 10. In the case of an IGBT, the first main electrode 5 is an emitter electrode and the second main electrode 10 is a collector electrode. The active region 101 also includes, among other things, a gate electrode (not shown), a gate insulating film, an emitter layer of the first conductivity type, a channel layer of the second conductivity type, a body layer of the second conductivity type, etc. The impurity concentration of each semiconductor layer is, for example, the drift layer 1 has a low concentration of n-, the well layer 2 has a medium concentration of p, the collector layer 9 has a high concentration of p+, the emitter layer has a high concentration of n+, the channel layer has a medium concentration of p, and the body layer has a medium concentration of p. Since the configuration of the active region 101 is the same as that of a general semiconductor element, a detailed description will be omitted.

[0017] The termination region 102 includes a drift layer 1 of the first conductivity type, a field limiting layer 3 of the second conductivity type formed on a part of the surface of the drift layer 1, a field insulating film 8 covering the drift layer 1 and the field limiting layer 3, and a field plate 7 electrically connected to the field limiting layer 3. Note that, at the location shown in FIG. 2, the field limiting layer 3 and the field plate 7 are insulated from each other by the field insulating film 8, but at the connection part shown in FIG. 4 described later, the two are electrically connected.

[0018] The field limiting layer 3 is, for example, a field limiting ring. The impurity concentration of the field limiting layer 3 is, for example, a medium concentration of p. The field insulating film 8 is, for example, an oxide film.

[0019] In this embodiment, the case where there is one set of the field limiting layer 3 and the field plate 7 is illustrated, but it is not limited thereto, and a configuration may be adopted in which a plurality of field limiting layers 3 are provided side by side and field plates 7 are provided corresponding to each of them.

[0020] The field plate 7 is formed on the surface of the field insulating film 8 so as to extend to the outside of the field limiting layer 3. The longer the distance L between the end of the field limiting layer 3 and the end of the field plate 7, the stronger the electric field relaxation effect of the field plate 7 at the end of the field limiting layer 3. However, the longer this distance L, the smaller the radius of curvature of the equipotential line 11 that wraps around the end of the field plate 7, so there is a problem that the electric field tends to concentrate at the end of the field plate 7 and the breakdown voltage decreases.

[0021] Therefore, in this embodiment, the field insulating film 8 is configured to be thicker as it approaches the end of the field plate 7 in the region overlapping the field plate 7. More specifically, in the region overlapping the field plate 7, the surface of the field insulating film 8 is configured to become stepwise higher as it approaches the end of the field plate 7. Such a shape of the field insulating film 8 can be realized, for example, by repeating the formation and etching of the insulating film using a plurality of masks. The number of steps of the stepwise shape is desirably 3 or more. Also, in the region overlapping the field plate 7 and outside the field limiting layer 3, it is desirable that the surface of the field insulating film 8 becomes higher as it approaches the end of the field plate 7.

[0022] According to this embodiment, since the equipotential line 11 becomes inclined along the lower part of the stepped field plate 7 (the surface of the field insulating film 8), the radius of curvature of the equipotential line 11 that wraps around the end of the field plate 7 becomes larger, so the concentration of the electric field at the end of the field plate 7 can be alleviated and the breakdown voltage can be increased.

[0023] FIG. 3 is a cross-sectional view of a semiconductor device of a comparative example.

[0024] In the semiconductor device 100 of the comparative example, the surface of the field insulating film 8 and the field plate 7 have a flat shape at least outside the field limiting layer 3. Therefore, it can be seen that the radius of curvature of the equipotential line 11 that wraps around the end of the field plate 7 is smaller than that of this embodiment.

[0025] As can be seen from the comparison between this embodiment and the comparative example, according to this embodiment, the concentration of the electric field at the end of the field plate 7 provided in the termination region 102 can be alleviated, and the breakdown voltage can be increased.

[0026] As shown in FIG. 2, in this embodiment, the termination region 102 further includes a channel stopper 4 of the first conductivity type, a field stopper electrode 6, and an interlayer insulating film 12.

[0027] The channel stopper 4 is formed on a part of the surface of the drift layer 1 and is disposed outside the field limiting layer 3 and the field plate 7. The field stopper electrode 6 is electrically connected to the channel stopper 4.

[0028] The interlayer insulating film 12 is formed to cover the field plate 7 and the field insulating film 8.

[0029] FIG. 4 is a cross-sectional view of the connection portion of the first embodiment.

[0030] In the connection part that electrically connects the field limiting layer 3 and the field plate 7, the field insulating film 8 has a contact hole 13 for electrically connecting the field limiting layer 3 and the field plate 7 at a position overlapping the field limiting layer 3. Note that the contact hole 13 is also formed in the field plate 7 and the interlayer insulating film 12. Then, the field limiting layer 3 and the field plate 7 are electrically connected using the connection electrode 14. The connection electrode 14 can be formed simultaneously using the same material as the first main electrode 5 and the field stopper electrode. Note that the connection electrode 14 is not shown in FIG. 1. Also, the structure of the connection part is not limited to the structure shown in FIG. 4.

Example

[0031] FIG. 5 is a cross-sectional view of the semiconductor device of Example 2.

[0032] Example 2 is a modification of Example 1. In this example, in the region overlapping the field plate 7, the surface of the field insulating film 8 becomes curved and higher as it approaches the end of the field plate 7. Such a shape of the field insulating film 8 can be realized, for example, by isotropic wet etching.

[0033] According to this example, since the field plate 7 is curved, the radius of curvature of the equipotential line 11 that wraps around the end of the field plate 7 can be made larger than that in Example 1. Therefore, the concentration of the electric field at the end of the field plate 7 can be alleviated compared to Example 1, and the breakdown voltage can be increased.

[0034] Although the embodiments of the present invention have been described above, the present invention is not limited to the configurations described in the embodiments, and various modifications are possible within the scope of the technical idea of the present invention. Also, a part or all of the configurations described in each embodiment may be combined and applied.

Explanation of Reference Numerals

[0035] 1: Drift layer 2: Well layer 3: Field limiting layer 4: Channel stopper 5: First main electrode 6: Field stopper electrode 7: Field plate 8: Field insulating film 9: Collector layer 10: Second main electrode 11: Isoelectric line 12: Interlayer insulating film 13: Contact hole 14: Connection electrode 100: Semiconductor device 101: Active region 102: Termination region

Claims

1. A semiconductor device having an active region with a semiconductor element and a termination region surrounding the active region, wherein the termination region includes a drift layer of a first conductivity type, a field limiting layer of a second conductivity type formed on a part of the surface of the drift layer, a field insulating film covering the drift layer and the field limiting layer, and a field plate electrically connected to the field limiting layer, the field plate being formed to extend to the outside of the field limiting layer on the surface of the field insulating film, and the field insulating film being thicker as it approaches the end of the field plate in a region overlapping the field plate. A semiconductor device characterized by this.

2. In Claim 1, in a region overlapping the field plate, the surface of the field insulating film becomes stepwise higher as it approaches the end of the field plate. A semiconductor device characterized by this.

3. In Claim 2, a semiconductor device characterized in that the number of steps of the stepwise shape is 3 or more.

4. In Claim 1, in a region overlapping the field plate, the surface of the field insulating film becomes curved higher as it approaches the end of the field plate. A semiconductor device characterized by this.

5. In Claim 1, in a region overlapping the field plate and outside the field limiting layer, the surface of the field insulating film becomes higher as it approaches the end of the field plate. A semiconductor device characterized by this.

6. In Claim 1, the field insulating film has a contact hole for electrically connecting the field limiting layer and the field plate at a position overlapping the field limiting layer. A semiconductor device characterized by this.

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