Semiconductor device

Abstract

Embodiments relate to a semiconductor device. The semiconductor device includes: a first semiconductor layer of a first conductivity type provided on a first electrode, the first semiconductor layer having a plurality of land portions extending in a second direction and located at positions separated from each other in a first direction; a second electrode located in a recess provided in an upper portion of the stage portion and extending in a second direction; a gate electrode adjacent to the table portion in the first direction; an insulating film provided between the mesa portion and the gate electrode; and a second semiconductor layer of a second conductivity type in contact with an end portion of the second electrode in the second direction. The stage portion has: a first side surface facing the gate electrode across the insulating film in the first direction; and a second side surface that is located on the opposite side of the first side surface in the first direction and that is in contact with the second electrode.

Description

[0001] Related Application

[0002] This application claims priority from Japanese Patent Application No. 2024-059675 (Filing Date: April 2, 2024). The entire contents of the base application are incorporated herein by reference. TECHNICAL FIELD

[0003] Embodiments relate to a semiconductor device. BACKGROUND

[0004] In a vertical MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor), a Schottky-type MOSFET is proposed, which does not provide a p-type base layer, and which realizes an off state by a depletion layer extending from a Schottky junction between a source electrode in a trench contact portion and a semiconductor layer. SUMMARY

[0005] According to an embodiment, a semiconductor device includes: a first electrode; a first semiconductor layer of a first conductivity type, provided on the first electrode, having a plurality of mesa portions located at mutually separate positions in a first direction and extending in a second direction orthogonal to the first direction; a second electrode located in a recess provided on an upper portion of the mesa portion and extending in the second direction; a gate electrode adjacent to the mesa portion in the first direction; an insulating film provided between the mesa portion and the gate electrode; and a second semiconductor layer of a second conductivity type, in contact with an end portion of the second electrode in the second direction. The mesa portion has: a first side surface facing the gate electrode across the insulating film in the first direction; and a second side surface located on an opposite side of the first side surface in the first direction and in contact with the second electrode.

[0006] According to the present embodiment, a semiconductor device capable of reducing a leakage current can be provided. BRIEF DESCRIPTION OF DRAWINGS

[0007] Figure 1 is a schematic plan view of a semiconductor device of an embodiment.

[0008] Figure 2 is an enlarged schematic plan view of A portion in Figure 1

[0009] Figure 3 is an A-A sectional view in Figure 2

[0010] Figure 4 is​​Figure 2 BB cross-section view in.

[0011] Figure 5 yes Figure 2 CC section view in.

[0012] Figure 6 yes Figure 2 DD cross-sectional view in.

[0013] Figure 7 It is a schematic plan view of a semiconductor device according to a second embodiment.

[0014] Figure 8 yes Figure 7 EE cross-sectional view in.

[0015] Figure 9 This is a schematic plan view of a semiconductor device according to a first modification of the second embodiment.

[0016] Figure 10 It is a schematic plan view of a semiconductor device according to a second modification of the second embodiment.

[0017] Figure 11 It is a schematic plan view of a semiconductor device according to a third modification of the second embodiment.

[0018] Figure 12 This is a schematic plan view of a semiconductor device according to a third embodiment.

[0019] Figure 13 yes Figure 12 FF cross-sectional view in.

[0020] Description of reference numerals:

[0021] 10 ... first semiconductor layer, 11 ... terrace, 11A ... recess, 11B ... channel portion, 11C ... contact portion, 11S1 ... first side surface, 11S2 ... second side surface, 20 ... second semiconductor layer, 30 ... third semiconductor layer, 40 ... gate electrode, 51 ... first insulating film, 52 ... insulating layer, 53 ... second insulating film, 60 ... field plate electrode, 71 ... first connecting portion, 72 ... second connecting portion, 81 ... first conductive component, 82 ... second conductive component, 91 ... first electrode, 92 ... second electrode, 92A ... end surface, 93 ... gate pad, 101 ... element region, 102 ... terminal region DETAILED DESCRIPTION

[0022] The following describes each embodiment with reference to the accompanying drawings. Identical reference numbers are assigned to identical components in the drawings. In the following figures, directions are represented by the X-axis, Y-axis, and Z-axis. The direction along the X-axis is referred to as the first direction X. The direction along the Y-axis is referred to as the second direction Y, which is orthogonal to the first direction X. The direction along the Z-axis is referred to as the third direction Z, which is orthogonal to the first direction X and the second direction Y. In this specification, the width in a particular direction represents the maximum width in that particular direction.

[0023] like Figure 1 As shown, the semiconductor device of each embodiment includes a device region 101 and a termination region 102. Termination region 102 is continuous with device region 101 and surrounds device region 101. The semiconductor device includes a semiconductor layer. In this specification, the first conductivity type in the semiconductor layer is n-type, and the second conductivity type is p-type. Alternatively, the first conductivity type may be p-type and the second conductivity type may be n-type. The semiconductor layer is, for example, a silicon layer. Alternatively, the semiconductor layer may be a silicon carbide layer, a gallium nitride layer, or the like.

[0024] A second electrode 92 and a gate pad 93 are provided on the semiconductor layer. The gate pad 93 is electrically connected to a gate electrode described later. A wire is bonded to each of the second electrode 92 and the gate pad 93, for example, to electrically connect the second electrode 92 and the gate electrode to an external circuit.

[0025] [First embodiment]

[0026] Reference Figures 2-6 The semiconductor device according to the first embodiment will be described.

[0027] Figure 2 yes Figure 1 The enlarged schematic plan view of the A portion in FIG. Figure 7 、 Figures 9-12 Too Figure 1 An enlarged schematic plan view of section A.

[0028] Figure 3 yes Figure 2 AA section view in.

[0029] Figure 4 yes Figure 2 BB cross-section view in.

[0030] Figure 5 yes Figure 2 CC section view in.

[0031] Figure 6 yes Figure 2 DD cross-sectional view in.

[0032] like Figure 3As shown, the semiconductor device of the embodiment includes a first electrode 91, a first semiconductor layer 10 of n-type provided over the first electrode 91, and a second electrode 92 provided over the first semiconductor layer 10. The semiconductor device of the embodiment has, for example, a MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) configuration. The first electrode 91 is a drain electrode in the MOSFET, and the second electrode 92 is a source electrode in the MOSFET. For example, the first electrode 91 is applied with a positive potential, and the second electrode 92 is applied with 0 V. In an on state in which a gate voltage of the gate electrode 40 is higher than a threshold voltage, current flows between the first electrode 91 and the second electrode 92 along a longitudinal direction (third direction Z) through the first semiconductor layer 10. In the third direction Z, a direction from the first electrode 91 toward the second electrode 92 is set to be upward or above, and a direction from the second electrode 92 toward the first electrode 91 is set to be downward or below.

[0033] The first semiconductor layer 10 has a plurality of mesa portions 11 located at mutually separated positions in the first direction X and extending in the second direction Y. A trench configuration portion having the gate electrode 40 is provided adjacent to the mesa portion 11 in the first direction X. A plurality of the trench configuration portions are arranged in the first direction X. Each of the trench configuration portions extends in the second direction Y. The mesa portion 11 and the trench configuration portion are arranged in the element region 101.

[0034] The second electrode 92 is located in a recessed portion 11A provided in an upper portion of the mesa portion 11. The recessed portion 11A and the second electrode 92 in the recessed portion 11A extend in the second direction Y. In addition, the second electrode 92 is also provided on the trench configuration portion.

[0035] The trench configuration portion also has an insulating layer 52 provided between the gate electrode 40 and the second electrode 92 in the third direction Z, and a first insulating film 51 provided between the mesa portion 11 and the gate electrode 40 in the first direction X.

[0036] The trench configuration portion can also have a field plate electrode 60 and a second insulating film 53. The field plate electrode 60 is located below the gate electrode 40. The second insulating film 53 is provided between the gate electrode 40 and the field plate electrode 60, and between the field plate electrode 60 and the first semiconductor layer 10.

[0037] The portion of the mesa portion 11 between the trench structure portion and the second electrode 92 (the recess 11A) has a first side surface 11S1 and a second side surface 11S2. The first side surface 11S1 opposes the gate electrode 40 with the first insulating film 51 interposed therebetween in the first direction X. The second side surface 11S2 is located on the opposite side of the first side surface 11S1 in the first direction X. The second electrode 92 within the recess 11A is in contact with the second side surface 11S2.

[0038] The portion of the mesa portion 11 between the first side surface 11S1 and the second side surface 11S2 has a channel portion 11B and a contact portion 11C. The channel portion 11B opposes the gate electrode 40 with the first insulating film 51 interposed therebetween in the first direction X. The contact portion 11C is provided on the channel portion 11B. The n-type impurity concentration of the contact portion 11C is higher than the n-type impurity concentration of the channel portion 11B. The mesa portion 11 in the element region 101 does not include a p-type semiconductor layer.

[0039] The second electrode 92 is composed of a metal material. The second electrode 92 forms a Schottky junction with the second side surface 11S2 of the channel portion 11B. The second electrode 92 is in direct contact with the second side surface 11S2 of the channel portion 11B. Alternatively, the second electrode 92 can be in contact with the second side surface 11S2 of the channel portion 11B with an insulating film interposed therebetween. The second electrode 92 forms an ohmic contact with the second side surface 11S2 of the contact portion 11C.

[0040] The semiconductor device further includes a third semiconductor layer 30 of n-type, which is provided between the first electrode 91 and the first semiconductor layer 10 and is electrically connected to the first electrode 91. The n-type impurity concentration of the third semiconductor layer 30 is higher than the n-type impurity concentration of the first semiconductor layer 10.

[0041] In an on state in which the gate voltage of the gate electrode 40 is higher than the threshold voltage, current flows between the first electrode 91 and the second electrode 92 via the contact portion 11C and the channel portion 11B.

[0042] When the gate voltage of the gate electrode 40 is, for example, 0 V, which is lower than the threshold voltage, the channel portion 11B is depleted by a depletion layer extending in the first direction X from the Schottky junction between the second side surface 11S2 of the channel portion 11B and the second electrode 92 and a depletion layer extending in the first direction X from the boundary between the second side surface 11S2 of the channel portion 11B and the first insulating film 51 of the trench structure portion, and the semiconductor device becomes an off state.

[0043] To facilitate depletion of the channel portion 11B, the width of the channel portion 11B in the first direction X is preferably small. For example, the width of the channel portion 11B in the first direction X may be smaller than the width of the second electrode 92 in the recess 11A in the first direction X. The threshold voltage of the semiconductor device depends on the width of the channel portion 11B in the first direction X. Furthermore, the breakdown voltage and threshold voltage of the semiconductor device depend on the barrier height between the metal of the second electrode 92 and the first semiconductor layer 10. By using a metal with a high work function, such as Pt, as the second electrode 92, the barrier height between the second electrode 92 and the first semiconductor layer 10 can be increased, thereby improving the breakdown voltage.

[0044] The semiconductor device of the embodiment can be used as a switching element in applications such as inverters and motor drives. In this case, the semiconductor device is required to have a freewheeling diode function to flow the reverse current generated during switching. In this case, the second electrode 92 is preferably in contact with the first semiconductor layer 10 at the bottom of the recess 11A. This ensures a current path (a current path that does not pass through the channel portion) when the freewheeling diode operates.

[0045] The first semiconductor layer 10 is also provided in the terminal region 102 of the semiconductor device. No contact portion 11C is provided in the terminal region 102. In addition, a p-type second semiconductor layer 20 described later is provided in the terminal region 102.

[0046] The side surface of the second electrode 92 in the first direction X faces the groove structure. Figure 2 As shown, the end surface 92A of the second electrode 92 in the second direction Y does not face the trench structure in the second direction Y. Therefore, in the region adjacent to the end surface 92A of the second electrode 92, the depletion layer cannot extend from the boundary between the trench structure and the first semiconductor layer 10 in the second direction Y. This may cause leakage current to flow along the end surface 92A of the second electrode 92.

[0047] According to this embodiment, Figure 2 and Figure 4 As shown, a p-type second semiconductor layer 20 is provided in contact with the end portion of the second electrode 92 in the second direction Y. The second semiconductor layer 20 is provided within the first semiconductor layer 10 and is in contact with the end surface 92A and the bottom surface 92B of the end portion of the second electrode 92 in the second direction Y. The pn junction formed by the second semiconductor layer 20 and the first semiconductor layer 10 can reduce leakage current in the region adjacent to the end surface 92A of the second electrode 92.

[0048] like Figure 2 and Figure 5As shown in FIG. 1, the gate electrode 40 is electrically connected to an unillustrated gate wiring provided on the insulating layer 52 via a first connecting portion 71 that penetrates the insulating layer 52 in the end region 102. Figure 1 The gate pad 93 is electrically connected as shown in FIG. 1.

[0049] As shown in FIG. 1, the field plate electrode 60 is electrically connected to the second electrode 92 provided on the insulating layer 52 via a second connecting portion 72 that penetrates the insulating layer 52 in the end region 102. Figure 2 Figure 6 As shown in FIG. 1, the field plate electrode 60 is electrically connected to the second electrode 92 provided on the insulating layer 52 via a second connecting portion 72 that penetrates the insulating layer 52 in the end region 102.

[0050] [2nd Embodiment]

[0051] Referring to FIG. 2, a semiconductor device according to a 2nd embodiment will be described. The semiconductor device according to the 2nd embodiment is different from the semiconductor device according to the 1st embodiment in that the semiconductor device according to the 2nd embodiment has a first conductive member 81 in an end region 102. Figures 7-11 As shown in FIG. 2, the semiconductor device according to the 2nd embodiment has the first conductive member 81 in the end region 102. The first conductive member 81 extends in the first direction X and opposes an end surface 92A of the second electrode 92 in the second direction Y.

[0052] Figure 7 Figure 8 As shown in FIG. 2, the semiconductor device according to the 2nd embodiment has the first conductive member 81 in the end region 102. The first conductive member 81 extends in the first direction X and opposes an end surface 92A of the second electrode 92 in the second direction Y.

[0053] The trench structure portion in the end region 102 is arranged so as to extend in the first direction X as in the element region 101. For example, the trench structure portion in the element region 101 and the trench structure portion in the end region 102 are formed simultaneously. For example, the first conductive member 81 in the trench structure portion in the end region 102 is formed simultaneously from the same material as the gate electrode 40 in the trench structure portion in the element region 101. The trench structure portion in the end region 102 has the first insulating film 51, the second insulating film 53, the field plate electrode 60, and the insulating layer 52 as in the trench structure portion in the element region 101.

[0054] As shown in FIG. 2, a portion 11D of the first semiconductor layer 10 is provided between the end surface 92A of the second electrode 92 and the first conductive member 81 in the second direction Y in the end region 102. The end surface 92A of the second electrode 92 forms a Schottky junction with the portion 11D of the first semiconductor layer 10. The first insulating film 51 is provided between the portion 11D of the first semiconductor layer 10 and the first conductive member 81 in the second direction Y. Figure 8

[0055] ​​​​According to the second embodiment, the portion 11D of the first semiconductor layer 10 can be depleted by a depletion layer extending in the second direction Y from the Schottky junction between the end surface 92A of the second electrode 92 and the portion 11D of the first semiconductor layer 10, and a depletion layer extending in the second direction Y from the boundary between the portion 11D of the first semiconductor layer 10 and the first insulating film 51. Thus, the leakage current in the region adjacent to the end surface 92A of the second electrode 92 can be reduced. In order to easily deplete the portion 11D of the first semiconductor layer 10, the width of the portion 11D of the first semiconductor layer 10 in the second direction Y is preferably smaller than the width of the first conductive member 81 in the second direction Y.

[0056] For example, the trench formed in the element region 101 and the trench formed in the terminal region 102 are connected to each other, and the first conductive member 81 and the gate electrode 40 are connected to each other in the trenches.

[0057] In Figure 7 In the example shown in FIG. 1, the semiconductor device has the second conductive member 82 in the terminal region 102, the second conductive member 82 being connected to the first conductive member 81 and extending in the second direction Y. The gate electrode 40 and the second conductive member 82 extend in opposite directions from the first conductive member 81. The gate electrode 40 extends from the first conductive member 81 toward the element region 101, and the second conductive member 82 extends from the first conductive member 81 toward the terminal of the semiconductor device.

[0058] For example, the trench structure portion including the gate electrode 40, the trench structure portion including the first conductive member 81, and the trench structure portion including the second conductive member 82 are formed in the same process. The gate electrode 40, the first conductive member 81, and the second conductive member 82 are formed of the same material at the same time. The trench structure portion including the second conductive member 82 has the first insulating film 51, the second insulating film 53, the field plate electrode 60, and the insulating layer 52, like the trench structure portion of the element region 101.

[0059] The end portion of the second conductive member 82 in the second direction Y is connected to the end portion of the first conductive member 81 in the second direction Y. Figure 5 Also, the gate wire and the gate pad 93 can be connected via the first connection portion 71. Thus, the gate electrode 40 is electrically connected to the gate wire and the gate pad 93 via the first conductive member 81 and the second conductive member 82.

[0060] In addition, the field plate electrode 60 is continuous below the gate electrode 40, below the first conductive member 81, and below the second conductive member 82. The end portion of the field plate electrode 60 in the second direction Y below the second conductive member 82 is connected to the end portion of the field plate electrode 60 in the second direction Y below the first conductive member 81. Figure 6 Also, the second electrode 92 is connected via the second connection portion 72.

[0061] exist Figure 7 In the example shown, the gate electrode 40 extending in the second direction Y and the second conductive member 82 extending in the second direction Y are offset from each other in the first direction X. Alternatively, as shown in FIG. Figure 10 As shown in FIG, the groove structure portion extending in the first direction X and the groove structure portion extending in the second direction Y may cross each other. Figure 7 The layout of the grooves and Figure 10 Compared with the layout of the trenches formed together, the embedding property of the conductive materials that become the gate electrode 40, the first conductive member 81 and the second conductive member 82 can be improved.

[0062] like Figure 9 As shown, the second conductive member 82 may not be provided. The trench structure including the gate electrode 40 and extending in the second direction Y is connected to the trench structure including the first conductive member 81 and extending in the first direction X in a T-shape.

[0063] like Figure 11 As shown, the trench structure portion including the gate electrode 40 and extending in the second direction Y may not be connected to the trench structure portion including the first conductive member 81 and extending in the first direction X.

[0064] [Third embodiment]

[0065] Reference Figure 12 and Figure 13 The semiconductor device of the third embodiment is described below. The semiconductor device of the third embodiment has a structure in which the p-type second semiconductor layer 20 of the first embodiment and the trench structure including the first conductive member 81 of the second embodiment are combined.

[0066] In the end region 102 , the second semiconductor layer 20 is located between the end surface 92A of the second electrode 92 and the first conductive member 81 in the second direction Y. The second semiconductor layer 20 is in contact with the end surface 92A and the bottom surface 92B of the second electrode 92 in the second direction Y.

[0067] The second semiconductor layer 20 is provided between the end surface 92A of the second electrode 92 and the first conductive member 81 in the second direction Y. In the second direction Y, the first insulating film 51 is provided between the second semiconductor layer 20 and the first conductive member 81 .

[0068] According to the third embodiment, the second semiconductor layer 20 adjacent to the end face 92A of the second electrode 92 can be depleted by the depletion layer extending from the boundary between the second semiconductor layer 20 and the first insulating film 51 in the second direction Y. In addition, the pn junction formed by the second semiconductor layer 20 and the first semiconductor layer 10 can reduce leakage current in the region adjacent to the end face 92A of the second electrode 92.

[0069] In the first and third embodiments, depending on the work function of the metal of the second electrode 92 or the impurity concentration of the second semiconductor layer 20, the end surface 92A of the second electrode 92 and the second semiconductor layer 20 can form a Schottky junction. In this case, it is possible to cause the depletion layer to spread from the interface between the end surface 92A of the second electrode 92 and the second semiconductor layer 20.

[0070] The film thickness of the first insulating film 51 in the end region 102 can also be thicker than the film thickness of the first insulating film 51 in the element region 101. Thereby, it is possible to improve the withstand voltage.

[0071] The above describes several embodiments of the present application, but these embodiments are presented as examples, and the intention is not to limit the scope of the application. These new embodiments can be implemented in other various ways, and various omissions, substitutions, and changes can be made within the scope of the gist of the application. These embodiments and variations thereof are included in the scope or gist of the application, and are included in the scope of the application and equivalents thereof recited in the claims.

Claims

1. A semiconductor device, wherein: have: 1st electrode; a first semiconductor layer of a first conductivity type provided on the first electrode and having a plurality of terraces located at positions separated from each other in a first direction and extending in a second direction perpendicular to the first direction; a second electrode located in a recess provided on an upper portion of the stage and extending in the second direction; a gate electrode adjacent to the mesa portion in the first direction; an insulating film provided between the mesa and the gate electrode; and a second semiconductor layer of the second conductivity type in contact with an end portion of the second electrode in the second direction; The platform has: a first side surface facing the gate electrode with the insulating film interposed therebetween in the first direction; and The second side surface is located on the opposite side to the first side surface in the first direction and is in contact with the second electrode.

2. A semiconductor device, wherein: have: 1st electrode; a first semiconductor layer of a first conductivity type provided on the first electrode and having a plurality of terraces located at positions separated from each other in a first direction and extending in a second direction perpendicular to the first direction; a second electrode located in a recess provided on an upper portion of the stage and extending in the second direction; a gate electrode adjacent to the mesa portion in the first direction; an insulating film provided between the mesa and the gate electrode; as well as a first conductive member extending in the first direction and facing an end portion of the second electrode in the second direction; The platform has: a first side surface facing the gate electrode with the insulating film interposed therebetween in the first direction; and The second side surface is located on the opposite side to the first side surface in the first direction and is in contact with the second electrode.

3. The semiconductor device according to claim 2, wherein Also features: The second semiconductor layer of the second conductivity type is located between the end portion of the second electrode and the first conductive member in the second direction and is in contact with the end portion of the second electrode.

4. The semiconductor device according to claim 2 or 3, wherein: The first conductive member is connected to the gate electrode.

5. The semiconductor device according to claim 4, wherein Also features: a second conductive component connected to the first conductive component and extending in the second direction; The gate electrode and the second conductive member extend from the first conductive member in opposite directions.

6. The semiconductor device according to claim 5, wherein The gate electrode and the second conductive member are offset from each other in the first direction.

7. The semiconductor device according to claim 1 or 2, wherein: The platform has: a channel portion located between the gate electrode and the second electrode in the first direction; and The contact portion is provided on the channel portion, and the first conductivity type impurity concentration of the contact portion is higher than that of the channel portion.

8. The semiconductor device according to claim 7, wherein The channel portion and the second electrode form a Schottky junction, The second electrode forms an ohmic contact with the contact portion.

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