Semiconductor device, and manufacturing method for same

Abstract

A semiconductor device comprising: a substrate; a first conductive member provided on a part of the surface of the substrate; a plurality of nitride semiconductor layers provided on the substrate and on the first conductive member and separated from each other; a source electrode provided on the nitride semiconductor layers; a drain electrode provided on the nitride semiconductor layer; a gate electrode provided on the nitride semiconductor layers; and a second conductive member extending between the first conductive member and the source electrode in the nitride semiconductor layers, and electrically connected to the first conductive member and the source electrode.

Description

Semiconductor device and manufacturing method thereof

[0001] The embodiments relate to a semiconductor device and a manufacturing method thereof.

[0002] High electron mobility transistors (HEMTs) using gallium nitride (GaN)-based materials are known as power devices. For example, if a half-bridge circuit including two GaN HEMTs is formed on the same wafer, a negative voltage is applied to the backside of the high-side device when the low-side device is turned off, which effectively creates a back-gate effect, potentially increasing the on-resistance.

[0003] JP 2013-211423 A

[0004] The embodiments provide a semiconductor device capable of fixing the potential of a substrate supporting a plurality of nitride semiconductor layers that are isolated from one another, and a method for manufacturing the same.

[0005] According to an embodiment, a semiconductor device includes a substrate, a first conductive member provided on a portion of a surface of the substrate, a plurality of nitride semiconductor layers provided on the substrate and the first conductive member and separated from each other, a source electrode provided on the nitride semiconductor layer, a drain electrode provided on the nitride semiconductor layer, a gate electrode provided on the nitride semiconductor layer, and a second conductive member extending between the first conductive member and the source electrode in the nitride semiconductor layer and electrically connected to the first conductive member and the source electrode.

[0006] 1 is a schematic plan view of a semiconductor device according to an embodiment; FIG. 2 is a schematic plan view of an active region in the semiconductor device according to an embodiment; FIG. 3 is a cross-sectional view taken along line A-A in FIG. 2; FIG. 4 is a schematic plan view showing an example of a pattern of a first conductive member in the semiconductor device according to an embodiment; FIG. 5 is a cross-sectional view taken along line B-B in FIG. 1; (a) and (b) are schematic cross-sectional views showing a method for manufacturing the semiconductor device according to an embodiment; (a) and (b) are schematic cross-sectional views showing a method for manufacturing the semiconductor device according to an embodiment; and FIG. 6 is a schematic plan view of a semiconductor device according to a modified embodiment.

[0007] Hereinafter, embodiments will be described with reference to the drawings, in which the same components are denoted by the same reference numerals.

[0008] As shown in Figure 4, the semiconductor device 1 of the embodiment includes a substrate 10 and a first conductive member 20 provided on a portion of the surface 10a of the substrate 10. Two directions that are parallel to the surface 10a of the substrate 10 and intersect each other (orthogonal in this example) are defined as a first direction X and a second direction Y. A direction that is orthogonal to the first direction X and the second direction Y and perpendicular to the surface 10a of the substrate 10 is defined as a third direction Z. For example, the first conductive member 20 extends along the first direction X and the second direction Y and has a grid-like planar pattern. The first conductive member 20 is in direct contact with the surface 10a of the substrate 10.

[0009] The substrate 10 is, for example, a silicon substrate. A sapphire substrate may also be used as the substrate 10. The first conductive member 20 may contain, for example, at least one selected from the group consisting of nickel, titanium nitride, and tungsten. When a silicon substrate is used as the substrate 10, the first conductive member 20 may contain nickel silicide.

[0010] The semiconductor device 1 of the embodiment includes a plurality of nitride semiconductor elements. In the example shown in Fig. 1, the plurality of nitride semiconductor elements are a first nitride semiconductor element 101 and a second nitride semiconductor element 102. The first nitride semiconductor element 101 and the second nitride semiconductor element 102 are, for example, lateral HEMT elements.

[0011] The first nitride semiconductor element 101 and the second nitride semiconductor element 102 are provided on the substrate 10 and the first conductive member 20, and have a plurality of nitride semiconductor layers 30 that are separated from each other. The first nitride semiconductor element 101 has a first nitride semiconductor layer 30A, and the second nitride semiconductor element 102 has a second nitride semiconductor layer 30B. In this specification, the first nitride semiconductor layer 30A and the second nitride semiconductor layer 30B are not distinguished from each other and are also simply referred to as nitride semiconductor layers 30. Note that three or more nitride semiconductor layers 30 that are isolated from each other may be provided on the substrate 10.

[0012] The first nitride semiconductor layer 30A and the second nitride semiconductor layer 30B are separated from each other by an element isolation portion 300 on the substrate 10. The element isolation portion 300 continuously surrounds the periphery of the first nitride semiconductor layer 30A and the periphery of the second nitride semiconductor layer 30B. The element isolation portion 300 is an insulating member and may include, for example, a silicon oxide film.

[0013] 3 , the nitride semiconductor layer 30 has a first layer 31 and a second layer 32. The second layer 32 is provided on the first layer 31 in the third direction Z. The band gap of the second layer 32 is wider than the band gap of the first layer 31. For example, the first layer 31 is a gallium nitride (GaN) layer, and the second layer 32 is an aluminum gallium nitride (AlGaN) layer. A two-dimensional electron gas 35 is distributed in the first layer 31 near the interface with the second layer 32.

[0014] The nitride semiconductor layer 30 may further include a third layer 33. The third layer 33 is provided between the substrate 10 and the first layer 31, and between the first conductive member 20 and the first layer 31. The third layer 33 functions as a buffer layer that reduces crystal defects in the nitride semiconductor layer 30. As the third layer 33, for example, an aluminum nitride (AlN) layer can be used.

[0015] Each of the first nitride semiconductor device 101 and the second nitride semiconductor device 102 has an active region AR. Fig. 2 is a schematic plan view of the active region AR. Fig. 3 is a cross-sectional view taken along line AA in Fig. 2.

[0016] Each of the first nitride semiconductor element 101 and the second nitride semiconductor element 102 has a source electrode 60, a drain electrode 40, a gate electrode 50, and a first insulating film 71. These are provided on the nitride semiconductor layer 30.

[0017] 2, the source electrode 60 has source finger portions 62 and a source pad portion 61. The source pad portion 61 extends in a first direction X. A plurality of source finger portions 62 extend from the source pad portion 61 in a second direction Y. As shown in FIG. 3, the source finger portions 62 contact the surface of the nitride semiconductor layer 30 and are electrically connected to the nitride semiconductor layer 30. The source electrode 60 can be made of, for example, a layered structure of titanium (Ti) and aluminum (Al).

[0018] 2, the drain electrode 40 has a drain finger portion 42 and a drain pad portion 41. The drain pad portion 41 extends in a first direction X. The plurality of drain finger portions 42 extend in a second direction Y from the drain pad portion 41 toward the source pad portion 61. As shown in FIG. 3, the drain finger portions 42 contact the surface of the nitride semiconductor layer 30 and are electrically connected to the nitride semiconductor layer 30. The drain electrode 40 may be made of the same material as the source electrode 60, for example.

[0019] 3, a first insulating film 71 is provided on the surface of the nitride semiconductor layer 30 between the source finger portion 62 and the drain finger portion 42. As the first insulating film 71, for example, a silicon oxide film can be used.

[0020] As shown in FIG. 2 , the gate electrode 50 has a gate finger portion 52 and a gate wiring portion 51. The gate wiring portion 51 extends in a first direction X. A plurality of gate finger portions 52 extend from the gate wiring portion 51 in a second direction Y. For example, the gate finger portion 52 extends from the gate wiring portion 51 toward the drain pad portion 41. The gate finger portions 52 are located between the drain finger portions 42 and the source finger portions 62 in the first direction X. Two gate finger portions 52 are located between two adjacent drain finger portions 42 in the first direction X. One source finger portion 62 is located between two adjacent gate finger portions 52 in the first direction X. The gate electrode 50 can be made of, for example, a stacked structure of nickel (Ni) and gold (Au), titanium nitride (TiN), or polycrystalline silicon (Poly-Si).

[0021] 3, the gate finger portions 52 are provided on a first insulating film 71. The distance in the first direction X between the drain finger portions 42 of the drain electrode 40 and the gate finger portions 52 of the gate electrode 50 is longer than the distance in the first direction X between the source finger portions 62 of the source electrode 60 and the gate finger portions 52 of the gate electrode 50. This improves the breakdown voltage.

[0022] Each of the first nitride semiconductor element 101 and the second nitride semiconductor element 102 has a second conductive member 80 shown in Fig. 5. The second conductive member 80 is provided in a columnar shape within the nitride semiconductor layer 30. The second conductive member 80 extends between the first conductive member 20 and the source electrode 60, and is electrically connected to the first conductive member 20 and the source electrode 60. Examples of materials that can be used for the second conductive member 80 include nickel (Ni), titanium (Ti), and aluminum (Al).

[0023] The second conductive member 80 is provided in a hole h formed in the nitride semiconductor layer 30. The first conductive member 20 is exposed at the bottom of the hole h. The second conductive member 80 is in contact with the exposed first conductive member 20. The second conductive member 80 is in contact with at least one of the multiple first conductive members 20 extending in, for example, a lattice pattern. Because the multiple first conductive members 20 are continuous in, for example, a lattice pattern, the multiple first conductive members 20 are electrically connected to the source electrode 60 via the second conductive member 80. The upper surface of the second conductive member 80 is in contact with the source pad portion 61 of the source electrode 60.

[0024] Each of the first nitride semiconductor element 101 and the second nitride semiconductor element 102 can have a second insulating film 72 provided between the surface of the nitride semiconductor layer 30 and the source pad portion 61. The second insulating film 72 is also provided between the surface of the nitride semiconductor layer 30 and the drain pad portion 41, and between the surface of the nitride semiconductor layer 30 and the gate wiring portion 51. The second insulating film 72 is also provided between a gate pad portion 53 (shown in FIG. 1 ), which will be described later, and the surface of the nitride semiconductor layer 30. As the second insulating film 72, for example, a silicon oxide film can be used.

[0025] 1 , the semiconductor device of the embodiment can include a support member 200 that supports a first nitride semiconductor element 101 and a second nitride semiconductor element 102. The support member 200 has an insulating portion 201 and a conductive portion. The insulating portion 201 can be made of, for example, a resin. The conductive portion is, for example, a lead frame, and includes a first lead 211, a second lead 212, a third lead 213, a fourth lead 214, and a fifth lead 215. The first lead 211, the second lead 212, the third lead 213, the fourth lead 214, and the fifth lead 215 can be made of, for example, iron (Fe), nickel (Ni), or copper (Cu).

[0026] The first nitride semiconductor element 101 and the second nitride semiconductor element 102 configure, for example, a half-bridge circuit. The first nitride semiconductor element 101 functions as a high-side element, and the second nitride semiconductor element 102 functions as a low-side element. Note that the semiconductor device 1 may have three or more nitride semiconductor elements on the substrate 10.

[0027] 1, the drain pad portion 41 provided on the first nitride semiconductor layer 30A of the first nitride semiconductor device 101 is electrically connected to a first lead 211 via a wire w. The first lead 211 is electrically connected to a power supply. The wire w may be, for example, a gold wire.

[0028] The source pad portion 61 provided on the second nitride semiconductor layer 30B of the second nitride semiconductor device 102 is electrically connected to the second lead 212 via the wire w. The second lead 212 is grounded.

[0029] A gate pad portion 53 electrically connected to the gate wiring portion 51 of the first nitride semiconductor element 101 is provided on the first nitride semiconductor layer 30A of the first nitride semiconductor element 101, and the gate pad portion 53 of the first nitride semiconductor element 101 is electrically connected to the third lead 213 via a wire w.

[0030] A gate pad portion 53 electrically connected to the gate wiring portion 51 of the second nitride semiconductor element 102 is provided on the second nitride semiconductor layer 30B of the second nitride semiconductor element 102, and the gate pad portion 53 of the second nitride semiconductor element 102 is electrically connected to the fourth lead 214 via a wire w.

[0031] The source pad portion 61 provided on the first nitride semiconductor layer 30A of the first nitride semiconductor element 101 is electrically connected to the fifth lead 215 via a wire w. The drain pad portion 41 provided on the second nitride semiconductor layer 30B of the second nitride semiconductor element 102 is electrically connected to the fifth lead 215 via a wire w. Therefore, the source electrode 60 of the first nitride semiconductor element 101 is electrically connected to the drain electrode 40 of the second nitride semiconductor element 102 at the fifth lead 215. The fifth lead 215 serves as an output terminal of the half-bridge circuit.

[0032] Alternatively, as shown in FIG. 8 , the source pad portion 61 of the first nitride semiconductor element 101 and the drain pad portion 41 of the second nitride semiconductor element 102 may be connected above the nitride semiconductor layer 30 so as to straddle the element isolation portion 300, thereby electrically connecting the source electrode 60 of the first nitride semiconductor element 101 and the drain electrode 40 of the second nitride semiconductor element 102.

[0033] The upper surface of the semiconductor device 1 shown in FIG. 1 is covered with a sealing member made of, for example, a resin material.

[0034] According to this embodiment, multiple nitride semiconductor elements 101, 102 can be realized on the same substrate 10, and the potential of the source electrode 60 can be applied to the substrate 10 via the second conductive member 80 and the first conductive member 20. By fixing the potential of the substrate 10 to the source potential, each of the multiple nitride semiconductor elements 101, 102 can be operated without being affected by the other nitride semiconductor elements. For example, it is possible to suppress an increase in on-resistance caused by a negative voltage being applied to the back surface of the high-side element (first nitride semiconductor element 101) when the low-side element (second nitride semiconductor element 102) is turned off. The source potential is, for example, ground potential.

[0035] 4 , the first conductive members 20 extend, for example, in a grid pattern on the surface 10a of the substrate 10, and portions of the grid-shaped first conductive members 20 contact the second conductive members 80, thereby applying a source potential to a wide range on the surface 10a of the substrate 10 other than the positions of the second conductive members 80. The planar pattern of the first conductive members 20 may be, for example, a pattern of multiple stripes extending in the first direction X or the second direction Y. In this case, the stripe-shaped first conductive members 20 can be connected to each other by at least one first conductive member 20 extending in a direction crossing the stripe-shaped first conductive members 20.

[0036] 3, the first conductive member 20 is also located below the drain finger portion 42 of the drain electrode 40 and below the gate finger portion 52 of the gate electrode 50. This allows a field plate effect to be imparted to the nitride semiconductor layer 30 from the back surface side, making it possible to alleviate the concentration of the electric field.

[0037] Next, a method for manufacturing the semiconductor device according to the embodiment will be described.

[0038] 6A, the method for manufacturing a semiconductor device according to the embodiment includes a step of forming first conductive members 20 on a portion of the surface 10a of the substrate 10. For example, as described above with reference to FIG.

[0039] After forming the first conductive member 20 , the method for manufacturing a semiconductor device according to the embodiment includes a step of forming a nitride semiconductor layer 30 on the substrate 10 and the first conductive member 20 .

[0040] For example, the nitride semiconductor layer 30 can be formed on the substrate 10, which is a silicon substrate, by a metal organic chemical vapor deposition (MOCVD) method. In order to allow the nitride semiconductor layer 30 to grow satisfactorily on the substrate 10, it is preferable that the area of ​​a portion of the surface 10a of the substrate 10 where the first conductive member 20 is provided is smaller than the area of ​​the other portion where the first conductive member 20 is not provided.

[0041] For example, in the example shown in FIG. 4 , the width of the first conductive member 20 in the first direction X and the width of the first conductive member 20 in the second direction Y are 0.1 μm, and the distance (pitch) between adjacent first conductive members 20 in the first direction X and the distance (pitch) between adjacent first conductive members 20 in the second direction Y are 10 μm.

[0042] 6B, in the step of forming the nitride semiconductor layer 30, for example, a third layer 33 is formed on the surface 10a of the substrate 10 as a buffer layer. The third layer 33 grown from the surface 10a of the substrate 10 can grow laterally on the first conductive member 20 to cover the first conductive member 20. The third layer 33 can be, for example, an aluminum nitride layer.

[0043] 7A, the first layer 31 and the second layer 32 are sequentially grown on the third layer 33. In addition, the insulating film 70 is formed on the second layer 32. The insulating film 70 may include the first insulating film 71 and the second insulating film 72 described above.

[0044] The method for manufacturing a semiconductor device according to the embodiment includes a step of separating the nitride semiconductor layer 30 into multiple pieces. For example, a trench is formed in the nitride semiconductor layer 30 by reactive ion etching (RIE) along the element isolation portion 300 shown in FIG. 1 . The trench reaches the surface 10a of the substrate 10. At the bottom of the trench, the third layer 33 may remain between the first conductive members 20. The trench separates the nitride semiconductor layer 30 into multiple pieces. In the example shown in FIG. 1 , the nitride semiconductor layer 30 is separated into a first nitride semiconductor layer 30A and a second nitride semiconductor layer 30B. An insulating member is buried in the trench. The nitride semiconductor layer 30 may be separated into three or more pieces.

[0045] 7B, the method for manufacturing a semiconductor device according to the embodiment includes a step of forming holes h in the nitride semiconductor layer 30, the holes h reaching the first conductive members 20. The holes h can be formed by, for example, RIE. The trenches and holes can be formed simultaneously. The holes h penetrate at least the insulating film 70, the second layer 32, and the first layer 31 in the third direction Z. At least the top surface of the first conductive member 20 is exposed at the bottom of the holes h. At least a portion of the side surface of the first conductive member 20 may be exposed at the bottom of the holes h.

[0046] The planar shape of the holes h is, for example, a rectangle. The planar shape of the holes h may also be circular. The width or diameter of the holes h can be, for example, 100 μm. In this case, for example, about 10 of the multiple first conductive members 20 arranged in the first direction X at intervals (pitch) of 10 μm can be exposed at the bottom of the holes h. Similarly, for example, about 10 of the multiple first conductive members 20 arranged in the second direction Y at intervals (pitch) of 10 μm can be exposed at the bottom of the holes h. By forming the first conductive members 20 in, for example, a grid pattern on the surface 10 a of the substrate 10 and forming holes h with a planar size larger than the pitch of the first conductive members 20, it is possible to easily expose the first conductive members 20 at the bottom of the holes h regardless of where the holes h are formed in the nitride semiconductor layer 30, without requiring any particular marks or the like.

[0047] The method for manufacturing a semiconductor device according to the embodiment includes a step of forming a second conductive member 80 in the hole h. As shown in FIG. 5, the second conductive member 80 contacts the first conductive member 20 at the bottom of the hole h.

[0048] The method for manufacturing a semiconductor device according to the embodiment includes a step of forming a source electrode 60 electrically connected to a second conductive member 80 on the nitride semiconductor layer 30. In the example shown in FIG. 5 , a source pad portion 61 of the source electrode 60 contacts an upper surface of the second conductive member 80. As a result, the first conductive member 20 is electrically connected to the source electrode 60 via the second conductive member 80.

[0049] In the step of forming the first conductive member 20, when the substrate 10 is a silicon substrate, the first conductive member 20 preferably contains nickel. After the first conductive member 20 is formed, the silicon of the substrate 10 and the nickel of the first conductive member 20 can be thermally reacted to convert the first conductive member 20 into nickel silicide. Because the lattice constant of nickel silicide is close to that of silicon, in the step of forming the nitride semiconductor layer 30, the nitride semiconductor layer 30 can be easily formed on the first conductive member 20 with reduced defects.

[0050] For example, the first conductive member 20 can be converted into nickel silicide by heat applied in the process of forming the nitride semiconductor layer 30 by MOCVD, and the nitride semiconductor layer 30 can be grown on the nickel silicide.

[0051] By reducing the thickness (height) of the first conductive member 20 in the third direction Z, it is easy to ensure the flatness of the nitride semiconductor layer 30. Furthermore, the thickness of the first conductive member 20 is required to be a thickness that ensures that the first conductive member 20 remains without being lost during etching to form the holes h. From this viewpoint, the thickness (height) of the first conductive member 20 in the third direction Z is preferably 10 nm or more and 100 nm or less.

[0052] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims.

[0053] REFERENCE SIGNS LIST 1...Semiconductor device, 10...Substrate, 20...First conductive member, 30...Nitride semiconductor layer, 30A...First nitride semiconductor layer, 30B...Second nitride semiconductor layer, 31...First layer, 32...Second layer, 33...Third layer, 35...Two-dimensional electron gas, 40...Drain electrode, 41...Drain pad portion, 42...Drain finger portion, 50...Gate electrode, 51...Gate wiring portion, 52...Gate finger portion, 53...Gate pad portion, 60...Source electrode, 61...Source pad portion, 62...Source finger portion, 101...First nitride semiconductor element, 102...Second nitride semiconductor element, 200...Support member, 211...First lead, 212...Second lead, 213...Third lead, 214...Fourth lead, 215...Fifth lead, 300...Element isolation portion, h...Hole, AR...Active region

Claims

1. A semiconductor device comprising: a substrate; a first conductive member provided on a portion of a surface of the substrate; a plurality of nitride semiconductor layers provided on the substrate and on the first conductive member and separated from one another; a source electrode provided on the nitride semiconductor layer; a drain electrode provided on the nitride semiconductor layer; a gate electrode provided on the nitride semiconductor layer; and a second conductive member extending between the first conductive member and the source electrode within the nitride semiconductor layer and electrically connected to the first conductive member and the source electrode.

2. The semiconductor device according to claim 1, wherein the area of ​​the portion of the surface of the substrate where the first conductive member is provided is smaller than the area of ​​the other portion where the first conductive member is not provided.

3. The semiconductor device according to claim 1 or 2, wherein the first conductive member extends in two directions that are parallel to the surface of the substrate and intersect with each other.

4. The semiconductor device according to claim 1 or 2, wherein the nitride semiconductor layer comprises a first layer and a second layer provided on the first layer and having a wider band gap than the first layer.

5. The semiconductor device according to claim 1 or 2, wherein the plurality of nitride semiconductor layers include a first nitride semiconductor layer and a second nitride semiconductor layer, and the source electrode provided on the first nitride semiconductor layer is electrically connected to the drain electrode provided on the second nitride semiconductor layer.

6. The semiconductor device according to claim 1 or 2, wherein the first conductive member is also located below the drain electrode and below the gate electrode.

7. The semiconductor device according to claim 1 or 2, wherein the substrate is a silicon substrate, and the first conductive member includes nickel silicide.

8. The semiconductor device according to claim 1 or 2, wherein the distance between the drain electrode and the gate electrode is longer than the distance between the source electrode and the gate electrode.

9. A method for manufacturing a semiconductor device, comprising the steps of: forming a first conductive member on a portion of a surface of a substrate; forming a nitride semiconductor layer on the substrate and on the first conductive member; separating the nitride semiconductor layer into a plurality of pieces; forming a hole in the nitride semiconductor layer reaching the first conductive member; forming a second conductive member in the hole in contact with the first conductive member; and forming a source electrode on the nitride semiconductor layer electrically connected to the second conductive member.

10. The method for manufacturing a semiconductor device according to claim 9, wherein the substrate is a silicon substrate, the first conductive member contains nickel, and the silicon and nickel are thermally reacted to convert the first conductive member into nickel silicide.

11. The method for manufacturing a semiconductor device according to claim 10, wherein the first conductive member is converted into nickel silicide by heat applied in the step of forming the nitride semiconductor layer.

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