Semiconductor device and method of manufacturing the same

Abstract

A semiconductor device A1 comprises: a semiconductor layer 11 having a trench 10; an insulation film 12 that covers the inner surface 10a of the trench; a conductor 13 embedded in the trench that is covered by the insulation film 12; a silicide layer 14 that forms a Schottky bond with the semiconductor layer surface 11a adjacent to the trench; and a metal layer 15 that continuously covers from the end face 14a of the silicide layer positioned higher than the top end face 12a of the insulation film covering the inner wall surface 10a of the trench, to the top end face of the insulation film. The metal layer has a metal element of the same type as the metal element that constitutes the silicide layer.

Description

Technical Field

[0001] The present disclosure relates to a semiconductor device and a method for manufacturing the semiconductor device.

Background Art

[0002] Conventionally, in the manufacture of a semiconductor device having a Schottky junction as also described in Japanese Patent Application Laid-Open No. 9-232597, an insulating film is formed on the surface of a semiconductor layer having a trench, a conductor is embedded in the trench, the insulating film on the surface of the semiconductor layer adjacent to the trench is removed by etching to expose the surface of the semiconductor layer, and a Schottky junction is formed on the surface of the semiconductor layer.

Summary of the Invention

[0003] A semiconductor device according to one aspect of the present disclosure includes a semiconductor layer having a trench, an insulating film covering an inner surface of the trench, a conductor embedded in the trench covered with the insulating film, a silicide layer forming a Schottky junction with a surface of the semiconductor layer adjacent to the trench, and a metal layer continuously covering from an end surface of the silicide layer located above an upper end surface of the insulating film covering an inner wall surface of the trench to the upper end surface of the insulating film. The metal layer has the same kind of metal element as a metal element constituting the silicide layer. A top electrode is provided which is in contact with the upper surface of the silicide layer through the opening of the metal layer, The upper end surface of the insulating film is located at the same depth as the surface of the semiconductor layer under the silicide layer or above the surface of the semiconductor layer under the silicide layer.

[0004] A method for manufacturing a semiconductor device according to one aspect of the present disclosure includes forming an insulating film on the surface of a semiconductor layer having a trench, embedding a conductor in the trench, removing the insulating film on the surface of the semiconductor layer adjacent to the trench by etching to expose the semiconductor layer, and forming a Schottky junction on the semiconductor layer. In the etching, the upper end surface of the insulating film covering the inner wall surface of the trench is lowered below the surface of the semiconductor layer. In the formation of the Schottky junction, a metal layer is brought into contact with the surface of the semiconductor layer and heat-treated to form a silicide layer by the reaction between the metal layer and the semiconductor layer, so that the interface between the silicide layer and the semiconductor layer is used as the Schottky junction. After the formation of the Schottky junction, the metal layer while continuously leaves a portion covering from the end face of the silicide layer to the upper end face of the insulating film removing a portion of the metal layer that covers the upper surface of the silicide layer to form an opening, , and then forming a top electrode in contact with the upper surface of the silicide layer through the opening. the upper end surface of the insulating film is located at the same depth as the surface of the semiconductor layer under the silicide layer or above the surface of the semiconductor layer under the silicide layer.

Brief Description of the Drawings

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Best Mode for Carrying Out the Invention

[0006] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. 〔Semiconductor Device〕 As shown in FIGS. 1 and 2, a semiconductor device A1 according to an embodiment of the present disclosure includes a semiconductor layer 11 having a trench 10, an insulating film 12, a conductor 13, a silicide layer 14, a metal layer 15, and a top electrode 16. The insulating film 12 covers the inner surface 10a of the trench 10. The conductor 13 is embedded in the trench 10 covered with the insulating film 12. The silicide layer 14 forms a Schottky junction with the semiconductor layer surface 11a adjacent to the trench 10. The metal layer 15 continuously covers from the end face 14a of the silicide layer 14 located above the upper end face 12a of the insulating film 12 covering the inner wall surface 10a1 of the trench 10 to the upper end face 12a of the insulating film 12. As the conductor 13, for example, polysilicon may be applied. The semiconductor layer 11 is silicon, and the insulating film 12 is a silicon oxide film as an example. As the top electrode 16, for example, aluminum is applied. The silicide layer 14 is a silicide layer formed by the reaction between the semiconductor layer 11 and the metal layer 15. As the silicide layer 14, for example, nickel silicide may be applied.

[0007] As shown in FIG. 2, the metal layer 15 covers the side surface 11b of the semiconductor layer 11 located above the upper end face 12a of the insulating film 12. That is, the semiconductor layer surface 11a corresponding to the Schottky junction with the silicide layer 14 is located above the upper end face 12a of the insulating film 12. Therefore, the side surface 11b of the semiconductor layer 11 continuous with the semiconductor layer surface 11a is located between the silicide layer 14 and the upper end face 12a of the insulating film 12. If there is no metal layer 15, the side surface 11b of the semiconductor layer 11 will directly contact the top electrode 16. Therefore, when a reverse voltage is applied, a current passing through the side surface 11b causes an increase in leakage current. According to the semiconductor device A1 of the present embodiment, the side surface 11b of the semiconductor layer 11 is covered by the metal layer 15. Therefore, the side surface 11b of the semiconductor layer 11 does not come into direct contact with the top electrode 16. The metal layer 15 has the same metal element as the metal element constituting the silicide layer 14 that forms the Schottky junction. The metal layer 15, which is the same metal as the Schottky junction forming metal, has a protective effect. That is, the side surface 11b is isolated from the top electrode 16 such as aluminum by the metal layer 15. Thereby, the generation of current passing through the side surface 11b during reverse voltage application can be suppressed, and the leakage current can be kept low.

[0008] Also, the top electrode 16 is in contact with the top surface of the silicide layer 14 through the opening of the metal layer 15. Thereby, the silicide layer 14 that forms the Schottky junction and the top electrode 16 can be directly electrically connected.

[0009] 〔Method for manufacturing a semiconductor device〕 An example of a manufacturing method for obtaining the above semiconductor device A1 will be described. (Insulating film formation, conductor embedding process) First, as shown in FIG. 3, an insulating film 12 is formed on the surface of the semiconductor layer 11 having the trench 10, and a conductor 13 is embedded in the trench 10. The top surface 13a of the conductor 13 is housed within the trench 10.

[0010] (Insulating film etching process) Next, the insulating film 12 on the surface 11a of the semiconductor layer adjacent to the trench 10 is removed by etching to expose the surface 11c of the semiconductor layer 11 as shown in FIG. 4. At this time, the insulating film 12 is over-etched to sufficiently expose the surface 11c of the semiconductor layer. As a result, the upper end surface 12a of the insulating film 12 covering the inner wall surface 10a1 of the trench 10 is etched deeper. That is, the upper end surface 12a of the insulating film 12 covering the inner wall surface 10a1 of the trench 10 is lowered below the surface 11c of the semiconductor layer. As shown in FIG. 4, the upper end surface 12a is located below the surface 11c of the semiconductor layer. In this case, the insulating film on the surface 11c of the semiconductor layer is sufficiently removed. Note that in the description of this semiconductor device and its manufacturing method, up and down are defined as follows: the direction in which the trench 10 is dug downward from the surface of the semiconductor layer 11 is down, and the opposite is up. This does not refer to the up and down directions (gravity directions) during the manufacturing or use of this semiconductor device.

[0011] (Schottky Junction Formation Step) Thereafter, as shown in FIG. 5, a metal layer 15 is formed on the surface 11c of the semiconductor layer, the upper end surface 12a of the insulating film 12, and the upper surface 13a of the conductor 13, and the metal layer 15 is brought into contact with the surface 11c of the semiconductor layer. Then, by performing heat treatment to form a silicide layer 14 by the reaction between the metal layer 15 and the semiconductor layer 11 as shown in FIG. 6, a Schottky junction is formed at the interface between the silicide layer 14 and the semiconductor layer 11, that is, at the surface 11a of the semiconductor layer.

[0012] (Upper Electrode Formation Step) Next, after opening the metal layer 15, aluminum or the like is formed as the upper electrode 16 on the silicide layer 14 and the metal layer 15 to obtain the semiconductor device A1 having the structure shown in FIGS. 1 and 2. Other necessary steps are performed to complete the semiconductor device A1. In this process, regarding the metal layer 15, at least the portion covering from the end face 14a of the silicide layer 14 to the upper end face 12a of the insulating film 12 is continuously left. That is, after forming the Schottky junction, while continuously leaving the portion covering from the end face 14a of the silicide layer 14 of the metal layer 15 to the upper end face 12a of the insulating film 12 (including the portion covering the side face 11b in this embodiment), the portion covering the upper surface of the silicide layer 14 of the metal layer 15 is removed to form an opening. Then, an upper electrode 16 in contact with the upper surface of the silicide layer 14 is formed through the opening. In this embodiment, the metal layer 15 is also left on the upper surface 13a of the conductor 13, but this may be removed.

[0013] 〔Comparison of reverse direction characteristics〕 FIG. 7 and FIG. 8 show a semiconductor device B1 of a comparative example. The semiconductor device B1 of the comparative example is different from the semiconductor device A1 of the above-described embodiment only in that the metal layer 15 is absent and the upper electrode 16 is in contact with the upper end face 12a of the silicide layer 14, the insulating film 12, and the upper surface 13a of the conductor 13, and the others are common. Such a semiconductor device B1 can be manufactured by removing all of the metal layer 15 before the upper electrode forming step with respect to the manufacturing method of the above-described embodiment. Regarding the semiconductor device A1 of the present embodiment and the semiconductor device B1 of the comparative example, when the reverse voltage-current characteristics were simulated under common conditions, the results were as shown in FIG. 9. As shown in FIG. 9, the semiconductor device A1 of the present embodiment can suppress the reverse current to be lower than that of the semiconductor device B1 of the comparative example, and the reverse direction characteristics are improved. It was confirmed that the leakage current can be suppressed to be low due to the protection effect of the above-described metal layer 15.

[0014] 〔Summary, others〕 According to the semiconductor device of the embodiment of the present disclosure described above, due to the protection effect of the metal layer 15, the leakage current at the edge of the Schottky junction can be suppressed to be low when a reverse voltage is applied. Also, the insulating film on the semiconductor layer surface 11c is sufficiently removed, and the device characteristics are good. According to the manufacturing method of the above-described embodiment of the present disclosure, a semiconductor device capable of suppressing the leakage current during reverse voltage application to a low level can be manufactured due to the protection effect of the metal layer 15. In addition, in the manufactured semiconductor device, the insulating film on the semiconductor layer surface 11c is sufficiently removed, and the device characteristics are good.

[0015] Although the embodiments of the present disclosure have been described above, these embodiments are shown as examples, and can be implemented in various other forms. Omissions, replacements, and changes of components can be made without departing from the gist of the invention. In the above embodiment, the metal layer 15 is opened on the silicide layer 14, and the silicide layer 14 and the upper electrode 16 are directly connected. However, a structure in which the silicide layer 14 and the upper electrode 16 are electrically connected via the metal layer 15 may be implemented. In that case, the step of opening the metal layer 15 is unnecessary.

[0016] In addition, in the above embodiment, the side surface 11b of the semiconductor layer 11 is located between the silicide layer 14 and the upper end surface 12a of the insulating film 12. However, even when the side surface 11b of the semiconductor layer 11 is not located between the silicide layer 14 and the upper end surface 12a of the insulating film 12, covering the peripheral portion (from the end surface 14a to the upper end surface 12a) of the Schottky junction with the metal layer 15 has the effect of suppressing the leakage current. For example, the upper end surface 12a of the insulating film 12 may be at the same depth position as the semiconductor layer surface 11a, or slightly above, and the insulating film 12 may cover only the lower part of the end surface 14a and not the upper part. Even in this case, the covering protection of the peripheral portion of the Schottky junction by the insulating film 12 becomes insufficient, which is a factor increasing the leakage current. Even in such a case, covering the peripheral portion (from the end surface 14a to the upper end surface 12a) of the Schottky junction with the metal layer 15 has the effect of suppressing the leakage current. Therefore, the present disclosure is not limited to the case where the side surface 11b of the semiconductor layer 11 is located between the silicide layer 14 and the upper end surface 12a of the insulating film 12. However, when the side surface 11b of the semiconductor layer 11 is located between the silicide layer 14 and the upper end surface 12a of the insulating film 12, the effect of suppressing the leakage current according to the present invention is remarkable.

[0017] In the above embodiment, the silicide layer 14 is a silicide layer formed by the reaction between the semiconductor layer 11 and the metal layer 15. By leaving the metal layer 15, a metal layer having the above-described protective effect is provided. However, it goes without saying that the same effect can be obtained even if a metal layer made of the same kind of metal element is newly formed as the metal layer 15 after removing the metal layer 15. However, according to the above embodiment, the number of steps is small, the production efficiency is good, and the metal layer for forming the silicide layer 14 is effectively utilized, so that the material is not wasted and it is economical.

Industrial Applicability

[0018] The present disclosure can be used in a semiconductor device and a method for manufacturing a semiconductor device.

Explanation of Reference Numerals

[0019] 10 Trench 11 Semiconductor layer 11a Semiconductor layer surface 12 Insulating film 13 Conductor 14 Silicide layer 15 Metal layer 16 Upper surface electrode A1 Semiconductor device

Claims

1. A semiconductor layer having a trench, an insulating film covering the inner surface of the trench, a conductor embedded in the trench covered by the insulating film, a silicide layer forming a Schottky junction with the surface of the semiconductor layer adjacent to the trench, a metal layer continuously covering from the end face of the silicide layer located above the upper end face of the insulating film covering the inner wall surface of the trench to the upper end face of the insulating film, comprising: the metal layer has the same metal element as the metal element constituting the silicide layer, comprising an upper electrode in contact with the upper surface of the silicide layer through an opening of the metal layer, a semiconductor device in which the upper end face of the insulating film is located at the same depth as the surface of the semiconductor layer under the silicide layer or above the surface of the semiconductor layer under the silicide layer.

2. The semiconductor device according to claim 1, wherein the silicide layer is a silicide layer formed by reaction between the semiconductor layer and the metal layer.

3. A method for manufacturing a semiconductor device, comprising forming an insulating film on the surface of a semiconductor layer having a trench, embedding a conductor in the trench, removing the insulating film on the surface of the semiconductor layer adjacent to the trench by etching to expose the semiconductor layer, and forming a Schottky junction on the semiconductor layer, in the etching, lowering the upper end face of the insulating film covering the inner wall surface of the trench below the surface of the semiconductor layer, in the formation of the Schottky junction, forming by bringing a metal layer into contact with the surface of the semiconductor layer and performing heat treatment to form a silicide layer by reaction between the metal layer and the semiconductor layer, thereby making the interface between the silicide layer and the semiconductor layer the Schottky junction, after the formation of the Schottky junction, while continuously leaving a portion of the metal layer covering from the end face of the silicide layer to the upper end face of the insulating film, removing a portion of the metal layer covering the upper surface of the silicide layer to form an opening, then, forming an upper electrode in contact with the upper surface of the silicide layer through the opening, a method for manufacturing a semiconductor device in which the upper end face of the insulating film is located at the same depth as the surface of the semiconductor layer under the silicide layer or above the surface of the semiconductor layer under the silicide layer.

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