This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2021-149048, filed on Sep. 14, 2021, and Japanese Patent Application No. 2022-130035, filed on Aug. 17, 2022; the entire contents of all of which are incorporated herein by reference.
Embodiments relate to a semiconductor device.
In a power control module, a semiconductor chip is preferably mounted using a copper wire of low electrical resistance. However, copper is harder than aluminum, silver or the like, and the copper wire may generate bonding damage in the semiconductor chip.
According to one embodiment, a semiconductor device includes a semiconductor part, first and second electrodes, and first and second protective films. The first electrode is provided on the semiconductor part. The first protective film is provided on the semiconductor part and covers an outer edge of the first electrode. The second electrode is provided on the first electrode. The second electrode includes an outer edge partially covering the first protective film. The second protective film is provided on the semiconductor part and covers the first protective film and the outer edge of the second electrode.
Embodiments will now be described with reference to the drawings. The same portions inside the drawings are marked with the same numerals; a detailed description is omitted as appropriate; and the different portions are described. The drawings are schematic or conceptual; and the relationships between the thicknesses and widths of portions, the proportions of sizes between portions, etc., are not necessarily the same as the actual values thereof. The dimensions and/or the proportions may be illustrated differently between the drawings, even in the case where the same portion is illustrated.
There are cases where the dispositions of the components are described using the directions of XYZ axes shown in the drawings. The X-axis, the Y-axis, and the Z-axis are orthogonal to each other. Hereinbelow, the directions of the X-axis, the Y-axis, and the Z-axis are described as an X-direction, a Y-direction, and a Z-direction. Also, there are cases where the Z-direction is described as upward and the direction opposite to the Z-direction is described as downward.
As shown in
The first electrode 20 is provided on a front surface of the semiconductor part 10 and is electrically connected to an active region (not illustrated) of the semiconductor part 10. The first electrode 20 includes, for example, aluminum. The first electrode 20 is, for example, a source electrode of a MOSFET. Or, the first electrode 20 is an emitter electrode of an IGBT or an anode electrode of a Schottky diode.
The second electrode 30 is provided on the first electrode 20. The second electrode 30 contacts the first electrode 20 and is electrically connected to the first electrode 20. The second electrode 30 includes a material having a higher hardness than the material of the first electrode 20. The second electrode 30 includes, for example, copper (Cu). The second electrode 30 is thicker than the first electrode 20 in a direction, e.g., a Z-direction, perpendicular to the front surface of the semiconductor part 10. Thereby, the semiconductor part 10 can reduced the impact applied thereto when bonding, for example, a copper wire to the second electrode 30; and it is possible to prevent the bonding damage.
The first protective film 40 is provided on the semiconductor part 10 to cover an outer edge 20e of the first electrode 20. The first protective film 40 includes, for example, a first resin that is insulative. The first protective film 40 includes, for example, polyimide. For example, the first protective film 40 covers, and protects from the outside air, the outer perimeter part of the first electrode 20 and the outer edge of the contact surface between the semiconductor part 10 and the first electrode 20.
The first protective film 40 includes a first part 40a covering the outer edge 20e of the first electrode 20, and a second part 40b contacting the front surface of the semiconductor part 10. The first part 40a and the second part 40b are provided as a continuous body. The first part 40a extends between the first electrode 20 and the second electrode 30.
The second protective film 50 is provided on the semiconductor part 10 to cover the first protective film 40 and an outer edge 30e of the second electrode 30. The second protective film 50 includes, for example, a second resin that is insulative. The second resin of the second protective film 50 may include the same component as the first resin of the first protective film 40. The second protective film 50 includes, for example, polyimide. The second resin may be a resin different from the first resin.
The second protective film 50 includes, for example, a first part 50a, a second part 50b, and a third part 50c. The first part 50a contacts a front surface of the second electrode 30 and extends along the front surface of the second electrode 30. The first part 50a extends inward from the outer edge 30e of the second electrode 30. For example, the first part 50a extends over the part at which the first part 40a of the first protective film 40 extends between the first electrode 20 and the second electrode 30; and the first part 50a covers the part at which the first electrode 20 and the second electrode 30 contact. The second part 50b contacts the front surface of the semiconductor part 10. The third part 50c covers the first protective film 40 between the first part 50a and the second part 50b. The first part 50a, the second part 50b, and the third part 50c of the second protective film 50 are provided as a continuous body.
The second protective film 50 doubly protects the contact surface between the semiconductor part 10 and the first electrode 20. Also, the second protective film 50 prevents delamination of the second electrode 30 from the first protective film 40 starting from the outer edge 30e of the second electrode 30.
For example, the close contact between the first protective film 40 and the second electrode 30 is not very secure because the first protective film 40 includes a resin. When operating the semiconductor device 1, stress is generated between the first protective film 40 and the second electrode 30 due to the linear thermal expansion coefficient difference thereof. When the second protective film 50 is not provided, there is a risk that the adhesion between the first protective film 40 and the second electrode 30 may degrade, and the second electrode 30 lifts up from the outer edge. Furthermore, the temperature rise and temperature drop that are repeated when operating the semiconductor device 1 may cause separation of the interface between the first electrode 20 and the second electrode 30. Such a discrepancy degrades the reliability of the semiconductor device 1.
In the semiconductor device 1 according to the embodiment, the delamination of the outer edge 30e of the second electrode 30 from the first protective film 40 can be prevented by providing the second protective film 50. Also, the reliability of the semiconductor device 1 can be further improved by the first and second protective films 40 and 50 including resins having high moisture resistance. For example, it is preferable for the second protective film 50 to include a resin having a higher moisture resistance than the first protective film 40.
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Thus, by providing the second electrode 30 further inward than the first electrode 20, the creepage distance from the front surface of the semiconductor part 10 to the outer edge 30e of the second electrode 30 via the surface of the first protective film 40 can be lengthened. The breakdown voltage of the semiconductor device 1 can be increased thereby. The breakdown voltage of the semiconductor device 1 can be further improved by providing the second protective film 50 that covers the first protective film 40 and the outer edge 30e of the second electrode 30.
A method for manufacturing the semiconductor device 1 will now be described with reference to
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An active region (not illustrated) of the semiconductor device 1 is provided directly under the first electrode 20. When the semiconductor device 1 is a MOSFET, a drain electrode (not illustrated) is provided at the backside of the wafer 100. When the semiconductor device 1 is an IGBT or a Schottky diode, a collector electrode, or a cathode electrode (not illustrated) is provided at the backside of the wafer 100.
For example, the wafer 100 can be diced into multiple semiconductor devices 1 in the state shown in
According to the embodiment as shown in
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The second protective film 50 is provided to expose a bonding area 30BA of the second electrode 30 to which a metal wire is bonded. The second protective film 50 also is provided so that a bonding area 60BA of the control pad 60 is exposed. Thus, the bonding areas 30BA and 60BA each have an exposed area sufficient for bonding the metal wires; and the second protective film 50 preferably covers the second electrode 30 and the control pad 60 as much as possible.
In the example shown in
The second protective film 50 effectively suppresses the delamination of the second electrode 30 from the first protective film 40. The second protective film 50 prevents the penetration of moisture and the like from the outside air, and increases the breakdown voltage of the semiconductor device 1.
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The metal wire 80 is bonded on the bonding area 60BA of the control pad 60 (see
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On the other hand, for example, the metal wire 80 (see
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For example, the semiconductor device 1 is mounted on the front surface of a DBC (Direct Bonded Copper) substrate 110 that is provided inside a case 120. The DBC substrate 110 includes a mount pad 113 and a control interconnect 115. The mount pad 113 and the control interconnect 115 are, for example, copper foil.
The semiconductor device 1 is mounted with the backside toward the mount pad 113. For example, the electrode at the backside of the semiconductor device 1 is electrically connected to the mount pad 113 via a die mount material 13 that is conductive.
For example, the DBC substrate 110 is mounted on a base plate 130 via a solder material 117. The solder material 117 connects the base plate 130 and the back surface of the DBC substrate 110. The base plate 130 is, for example, a metal plate. When operating the semiconductor device 1, the generated heat is externally dissipated via the DBC substrate 110 and the base plate 130.
The case 120 surrounds the DBC substrate 110 and the base plate 130 on which the semiconductor device 1 is mounted. The bottom of the case 120 contacts the base plate 130.
The case 120 includes connection terminals 123 and 125. The semiconductor device 1 provided inside the case 120 is electrically connected to the external circuit via the connection terminals 123 and 125. For example, the connection terminal 123 is electrically connected to the second electrode 30 of the semiconductor device 1 via the metal wire 70. For example, the connection terminal 125 is electrically connected to the mount pad 113 of the DBC substrate 110 via a metal wire 90. In other words, the connection terminal 125 is electrically connected to the electrode at the backside of the semiconductor device 1 via the metal wire 90 and the mount pad 113.
For example, the control pad 60 of the semiconductor device 1 (see
The semiconductor device 1 that is mounted on the DBC substrate 110 is immersed in, for example, a gel-like insulating member 140 filled into the space surrounded with the case 120 and the base plate 130. The space that is surrounded with the case 120 and the base plate 130 is sealed by a lid 150 connected to the upper end of the case 120.
In the power module 2, a large current flows between the connection terminal 123 and the connection terminal 125. Therefore, the reliability of the electrical connections between the semiconductor device 1 and the connection terminal 123 and between the mount pad 113 and the connection terminal 125 are increased by using, for example, copper wires as the metal wires 70 and 90. The plate-shaped or block-shaped metal connector 75 may be used instead of the metal wire 70.
As shown in
The first protective film 40 covers the outer edge 20e of the first electrode 20 on the semiconductor part 10. The first protective film 40 includes the first part 40a covering the outer edge 20e of the first electrode 20, and the second part 40b contacting the front surface of the semiconductor part 10. The first part 40a and the second part 40b are provided as a continuous body.
The second protective film 50 is provided on the semiconductor part 10 to cover the first protective film 40 and the outer edge 30e of the second electrode 30. The second protective film 50 includes, for example, the first part 50a, the second part 50b, and the third part 50c. The first part 50a contacts the front surface of the second electrode 30 and extends along the front surface of the second electrode 30 inward from the outer edge 30e of the second electrode 30. The second part 50b contacts the front surface of the semiconductor part 10. The third part 50c covers the first protective film 40 between the first part 50a and the second part 50b. The first part 50a, the second part 50b, and the third part 50c of the second protective film 50 are provided as a continuous body. The second protective film 50 doubly protects the contact surface between the semiconductor part 10 and the first electrode 20.
In the example, the second electrode 30 is provided on the first electrode 20 so that the outer edge 30e is apart from the first protective film 40. The second protective film 50 covers the front surface of the first electrode 20 exposed between the first protective film 40 and the second electrode 30.
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In the semiconductor device 3, the creepage distance from the front surface of the semiconductor part 10 to the outer edge 30e of the second electrode 30 via the surface of the first protective film 40 is longer, and the breakdown voltage can be increased. The breakdown voltage can be further increased by the second protective film 50 covering the outer edge 30e of the second electrode 30 and the exposed front surfaces of the first protective film 40 and the first electrode 20.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions, and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention.
Number | Date | Country | Kind |
---|---|---|---|
2021-149048 | Sep 2021 | JP | national |
2022-130035 | Aug 2022 | JP | national |