Patent Application
20230275119
The present disclosure relates to a transformer element, a semiconductor device, a method of manufacturing a transformer element, and a method of manufacturing a semiconductor device.
International Publication No. 2014/155478 discloses a semiconductor device including two coils that are magnetically coupled to each other.
By thickening a wire bonding pad of the coil formed on the upper side of the insulating film that insulates between the coils, the operability level of wire bonding to the pad improves. In the conventional technology, however, thickening the pad without affecting the coil characteristics has been difficult to implement.
An object of the present disclosure is to provide a transformer element in which pads are made thick while suppressing influence on coil characteristics, and a method of manufacturing a transformer element in which a pad or pads are made thick while suppressing influence on coil characteristics.
In an aspect of the present disclosure, a transformer element includes a first coil having a planner shape, a first insulating film provided on an upper side of the first coil, a second coil having a planner shape and opposite to the first coil and provided on the first insulating film, a first pad provided on the first insulating film and connected to a side of one end of the second coil, a second pad provided on the first pad, and a second insulating film provided on the first insulating film and the second coil so as to cover the second coil. An aggregate thickness of the first pad and the second pad is thicker than the second coil, and the second pad at least partially covers the second insulating film.
In an aspect of the present disclosure, in a method of manufacturing a transformer element, the transformer element includes a first coil having a planner shape, a first insulating film provided on an upper side of the first coil, a second coil having a planner shape and opposite to the first coil and provided on the first insulating film, a first pad provided on the first insulating film and connected to a side of one end of the second coil, a second pad provided on the first pad, and a second insulating film provided on the first insulating film and the second coil so as to cover the second coil. The method includes forming the second coil on the first insulating film, and then forming the second insulating film on the first insulating film and the second coil such that the second coil is covered and the first pad is not covered at least partially. The method also includes forming the second pad on the first pad after forming the second insulating film.
The present disclosure is to provide a transformer element in which pads are made thick while suppressing influence on coil characteristics, and a method of manufacturing a transformer element in which the pad or pads are made thick while suppressing influence on coil characteristics.
These and other objects, features, aspects and advantages of the present disclosure will become more apparent from the following detailed description of the present disclosure when taken in conjunction with the accompanying drawings.
In the description to be made, even though terms indicating specific directions such as “upper” and “lower”, may be used, these terms are for promoting the understanding of the contents of the embodiments; therefore, they do not limit the directions at the time of manufacturing or the time of using of the transformer element or the semiconductor device.
The transformer element 101 includes an insulating film 2, a coil module 3, a coil module 4, an insulating film 5, an insulating film 6, an insulating film 7, an insulating film 8, and an insulating film 9. A film including the insulating film 6, the insulating film 7, and the insulating film 8 is an example of a first insulating film, and the insulating film 9 is an example of a second insulating film.
The transformer element 101 is formed on a substrate 1, as illustrated in
The coil module 3 includes a wiring 31, a coil 32 (an example of a first coil), a contact 33, a pad 34, a pad 35, and a pad 36. The coil 32, being a planar coil, is a spiral coil as well.
The coil module 4 includes a coil 42 (an example of a second coil), a pad 45 (an example of a first pad), and a pad 46 (an example of a second pad). The coil 42, being a planar coil, is a spiral coil as well.
The substrate 1 may be a semiconductor substrate using a semiconductor such as Si, SiC, or GaN, or may be an insulating substrate such as glass or ceramics. The semiconductor device of the first embodiment is a semiconductor device, for example, in which the substrate 1 is a semiconductor substrate and a semiconductor element is formed on a portion of the substrate 1 other than the portion illustrated in
The insulating film 2 is provided on the substrate 1.
The wiring 31 is provided on the insulating film 2.
The insulating film 5 is provided on the insulating film 2 and the wiring 31.
The contact 33 and the pad 34 are provided on wiring 31, respectively. The contact 33 and the pad 34 respectively protrude above the upper surface of the insulating film 5.
The coil 32 is provided on the insulating film 5.
The pad 34 is connected to one end on the center side of the coil 32, which is a spiral coil, via the wiring 31 and the contact 33.
The insulating film 6 is provided on the insulating film 5, the coil 32, and the contact 33.
The pad 34 is partially covered with the insulating film 6. The pad 35 is provided on a portion of pad 34 without the insulating film 6 covering thereof.
The insulating film 7 is provided on the insulating film 6. The insulating film 7 is provided on a region overlapping with the coil 32 in plan view. The insulating film 7 is not provided on a region overlapping with the pad 35 in plan view.
The insulating film 8 is provided on the insulating film 7.
The coil 42 and the pad 45 is provided on the insulating film 8. The coil 42 and the coil 32 are opposite to each other with the insulating film 6, the insulating film 7, and the insulating film 8 interposed therebetween.
The pad 45 is connected to one end side of the coil 42. The pad 45 is connected to one end on the center side of the coil 42, which is a spiral coil.
The insulating film 9 is provided on the insulating film 8 and the coil 42 so as to cover the coil 42. The insulating film 9 protects the surface of the transformer element 101. The pad 46 is provided on the pad 45. The aggregate thickness of the pad 46 and the pad 45 is greater than the thickness of the coil 42. The insulating film 9 is, for example, a polyimide film.
An opening 91 is provided in the insulating film 9 at a position that at least partially overlaps with the pad 45 in plan view. The pad 45 is at least partially not covered with the insulating film 9.
An opening 92 is provided in the insulating film 9 at a position that at least partially overlaps with the pad 35 in plan view. The pad 35 is at least partially not covered with the insulating film 9.
The insulating film 2, the insulating film 5, and the insulating film 6 are each, for example, an oxide film or a nitride film typically used in semiconductor devices. For the insulating film 2, the insulating film 5, and the insulating film 6, films formed using the same material, or films formed using different materials may be adoptable.
The coil 32 is, for example, a primary coil, and coil 42 is, for example, a secondary coil. The magnetic coupling between the coil 32 and the coil 42 establishes signal transmission between a circuit electrically connected to the coil 32 and a circuit electrically connected to the coil 42.
A high voltage may be applied to the coil 32 and the coil 42, in which case a high potential difference causes between the coil 32 and the coil 42. The breakdown voltage of the transformer element 101 is adjustable by coordinating the configuration of the insulating film 7 provided between the coil 32 and the coil 42. For example, by thickening the insulating film 7, the breakdown voltage of the transformer element 101 can be increased.
The insulating film 7 is, for example, an organic insulating film The organic insulating film is, for example, a polyimide film.
The insulating film 8 provided on the insulating film 7 is preferably a film formed using a material different from the material of the insulating film 7, such as an oxide film or a nitride film.
Signal exchange between the coil module 3 and the outside of the transformer element 101 is implemented via wires connected to the pad 36.
The coil module 3 may not be provided with the pad 36 as illustrated in
The pad 36 has the dimensions larger than the opening 92 provided in the insulating film 9 in plan view. The pad 36 overlaps with the entire opening 92 in plan view, for example. The pad 36 at least partially covers the insulating film 9. The pad 36 covers, for example, the edge of the opening 92 of the insulating film 9 in the entire circumferential direction of the edge of the opening 92.
The pad 46 has the dimensions larger than the opening 91 provided in the insulating film 9 in plan view. The pad 46 overlaps with the entire opening 91 in plan view, for example. The pad 46 at least partially covers the insulating film 9. The pad 46 covers, for example, the edge of the opening 91 of the insulating film 9 in the entire circumferential direction of the edge of the opening 91.
Signal exchange between the coil module 4 and the outside of the transformer element 101 is implemented via wires connected to the pad 46. The coil module 4 includes the pad 45 formed in the same process as the coil 42 is formed and the pad 46 formed in a separate process from the coil 42 is formed, and the aggregate thickness of the pad 45 and the pad 46 is thicker than the coil 42. The pad 46 may partially overlap with the coil 42 in plan view.
When performing wire bonding to the pads, the wire bonding is performed with the raised temperature and a load and ultrasonic waves being applied thereto so as to secure sufficient bonding strength between the wires and the pads. The strength of the bond between the wires and the pads is also affected by the pad thickness and bases of the pads.
In the case of the transformer element 101, the bases of the pad 34, the pad 35 and the pad 36, which are the pads of the coil module 3, are the wiring 31, the insulating film 2 and the substrate 1, and the bases of the pad 45 and the pad 46, which are the pads of the coil module 4, are the insulating film 8 and the insulating film 7 being a thick film. The bond strength by the wire bonding to the pads of the coil module 3 is greatly affected by the substrate 1. The bond strength by the wire bonding to the pads of the coil module 4 is greatly affected by the insulating film 7.
The insulating film 7 is an organic insulating film and is softer than the substrate 1, which is a semiconductor substrate or the like, therefore, in the transformer element 101z, when wire bonding to the pad of the coil module 3 and wire bonding to the pad of the coil module 4 are performed under the same conditions, the bond strength of the coil module 4 is lower. In other words, if wire bonding to the pad of the coil module 4 is performed under the condition where wire bonding to the pad of the coil module 3 is properly performed in the transformer element 101z, the bonding strength of the wire bonding to the pad of the coil module 4 is insufficient.
On the other hand, if the wire bonding to the pad of the coil module 3 is performed under the condition where the wire bonding to the pad of the coil module 4 is properly performed, excessive load is applied to the pad of the coil module 3, causing cracks in the wiring 31 or the insulating film 2 being the base of the pad, and lowering the reliability of the transformer element 101z.
It is also conceivable in the transformer element 101z that the bonding to the pad of the coil module 4 is properly performed under the same conditions as the bonding to the pad of the coil module 3 by thickening the coil 42 and pad 45. For example, an experiment showed that it has been confirmed that the bonding strength of wire bonding of the coil module 4 to the pad is sufficient by setting the thickness of the pad 45 to 8 μm or more when the insulating film 7 is made of polyimide. However, in the transformer element 101z, in order to increase the thickness of the pad 45, the coil 42 must be thickened as well. In order to increase the thickness of the coil 42, widening the radial interval of the spiral shape of the coil 42 is required, or the line width of the spiral shape of the coil 42 may become thin during processing. Therefore, in the transformer element 101z, there is a problem that when the pad 45 is made thicker, the space efficiency of the coil 42 is deteriorated and the electrical characteristics of the coil 42 is deteriorated.
The transformer element 101 of the first embodiment includes the pad 45 formed in the same process as the coil 42 is formed, and the pad 46 formed in a process different from that of coil 42; therefore, the pads of the coil module 4 can be formed thick as a whole without thickening the coil 42, and the pads of the coil module 4 can be thickened while suppressing the influence on the characteristics of the coil 42. For example, even if the pads of the coil module 4 are thickened, the space efficiency of the coil 42 does not deteriorate. In addition, the transformer element 101 is advantageous in that, even if it is required to change the wire bonding conditions with the film thickness or material of the insulating film 7 having changed, such a change is dealt with simply changing the film thickness of the pad 46 without changing the configuration of the coil 42. The aggregate thickness of the pad 45 and the pad 46 is, for example, 8 μm or more.
Wire-bonding to pad is performed with a wire-bonding tool being pressed against the pad, and the pad must be larger than the wire-bonding tool. The pad 46, which, at least, partially covers the insulating film 9, is provided; therefore, the required pad size is secured for wire bonding with only the size of the pad 46 increasing without changing the arrangement area of the coil 42.
First, the insulating film 2 is formed on the substrate 1 in Step S1. The insulating film 2 may be any material as long as it can electrically insulate the substrate 1 from the coil module 3 and the coil module 4. The insulating film 2 is, for example, an oxide film or a nitride film, however, other films may be adoptable as long as insulation can be secured.
Next, the wiring 31 is formed on the insulating film 2 in Step S2. In Step S2, a conductive film is formed on the insulating film 2 using a vacuum deposition method, a chemical vapor deposition method, a sputtering method, or the like, and then, the wiring 31 is formed by processing the conductive film into a desired pattern using a photolithography technique and an etching technique. The conductive film formed on the insulating film 2 may be any of a film of metal such as gold or aluminum, a low-resistance semiconductor film, or a conductive organic film.
Next, in Step S3, the insulating film 5 is formed on the insulating film 2 and the wiring 31. In Step S3, the insulating film 5 is formed so as to have openings at positions where the contact 33 and the pad 34 are formed.
Next, in Step S4, the coil 32, the contact 33 and the pad 34 are formed. In Step S4, a conductive film is formed using a vacuum deposition method, a chemical vapor deposition method, a sputtering method, or the like, and the coil 32, the contact 33, and the pad 34 are formed by processing the conductive film into a desired pattern using a photolithography technique and an etching technique.
Next, in Step S5, the insulating film 6, the insulating film 7, and the insulating film 8, which are inter-coil insulating films, are formed. In Step S5, first, the insulating film 6 is formed on the insulating film 5, the coil 32, the contact 33, and the pad 34, and then an opening is provided in the insulating film 6 so that the pad 34 is partially exposed from the insulating film 6 (see
Next, in Step S6, a conductive film is formed, and then, the conductive film is processed to form the pad 35, the coil 42, and the pad 45 (see
Next, in Step S7. the insulating film 9 is formed to protect the surface of the transformer element 101 (see
Next, in Step S8, the pad 36 and the pad 46 are formed.
In Step S8, first, a conductive film 40 is formed on the insulating film 9 (see
The transformer element 101 illustrated in
As described above, in the method of manufacturing the transformer element of the first embodiment, the coil 42 is formed on the insulating film 8 and then the insulating film 9 is formed on the insulating film 8 and the coil 42 such that the coil 42 is covered and the pad 45 is not covered at least partially, and after forming the insulating film 9 the pad 46 is formed on the pad 45.
It is also possible to form the pad 46 and the pad 36 from the state illustrated in
The semiconductor device of the first embodiment is manufactured by using a semiconductor substrate as the substrate 1 and forming the transformer element 101 on the substrate 1 by the above-described method of manufacturing the transformer element of the first embodiment.
A coil module 3 in the transformer element 102 is different from the coil module 3 in the transformer element 101 in that, instead of the pad 35 and the pad 36, a pad 36b is provided therein. A coil module 4 in the transformer element 102 is different from the coil module 4 in transformer element 101 in that, instead of the pad 45 and the pad 46, a pad 46b is provided therein. In other respects, the transformer element 102 is similar to the transformer element 101.
The pad 46b is thicker than the coil 42. The pad 46b is thick enough for proper wire bonding. That is, the thickness of pad 46b is equivalent to the aggregate thickness of the pad 45 and the pad 46 in the first embodiment.
Steps S1 to S5 in the method of manufacturing the semiconductor device of the second embodiment are the same as Steps S1 to S5 in the method of manufacturing the transformer element 101 in the first embodiment.
After Step S5, in Step S6b, the pad 36b, the pad 46b, and the coil 42 are formed from the state illustrated in
In Step S6b, first, a conductive film 41 is formed as illustrated in
Next, the insulating film 9 for surface protection is formed in Step S7. The method of forming the insulating film 9 is the same as that in the first embodiment.
The transformer element 102 illustrated in
The pad 46b being thick improves the bonding strength in wire bonding to the pad 46b. The pad 46b is thicker than the coil 42; therefore, even if the pad 46b is thickened so as to obtain sufficient bonding strength in wire bonding to the pad 46b, the influence on the characteristics of the coil 42 is suppressed.
In the manufacturing method of the semiconductor device of the second embodiment, the conductive film 41 to be the coil 42 and the pad 46b is formed on the insulating film 8, and then the conductive film 41 is partially removed to form the coil 42 and the pad 46b. Therefore, the formation of the conductive film for forming the coil module 4 needs to be performed only once, improving the production efficiency.
The semiconductor device of the second embodiment is manufactured by using a semiconductor substrate as the substrate 1 and forming the transformer element 102 on the substrate 1 by the above-described method of manufacturing the transformer element of the second embodiment.
In the transformer element 103 as well, the pad 46 is provided on the pad 45 as in the case of the transformer element 101 of the first embodiment. The aggregate thickness of the pad 46 and the pad 45 is greater than the thickness of the coil 42. The pad 46 has the dimensions larger than the opening 91 provided in the insulating film 9 in plan view. The pad 46 overlaps the entire opening 91 in plan view. The pad 46 at least partially covers the insulating film 9. The pad 46 covers, for example, the edge of the opening 91 of the insulating film 9 in the entire circumferential direction of the edge of the opening 91.
The pad 36c has the dimensions larger than the opening 92 provided in the insulating film 7 and the insulating film 9 in plan view. The pad 36c overlaps the entire opening 92 in plan view. The pad 36c at least partially covers the insulating film 9. The pad 36c covers, for example, the edge of the opening 92 of the insulating film 9 in the entire circumferential direction of the edge of the opening 92.
Steps S1 to S4 in the method of manufacturing the semiconductor device of the third embodiment are the same as Steps S1 to S4 in the method of manufacturing the transformer element 101 in the first embodiment.
In Step S5c, first, an insulating film 6 is formed in the same manner as in Step S5 in the manufacturing method of the semiconductor device of the first embodiment (see
In Step S5c, next, an insulating film 7 is formed from the state of
Next, in Step S6c, the coil 42 and the pad 45 are formed on the insulating film 7 by a method similar to that described in the first embodiment (see
Next, the insulating film 9 is formed in Step S7c. In Step S7c, first, the insulating film 9 is formed as illustrated in
Next, in Step S8c, the pad 46 is formed on the pad 45 (see
Next, in Step S9c, the pad 36c is formed. In Step S9c, the resist 10 is formed on the insulating film 9 (see
The transformer element 103 illustrated in
In the method of manufacturing the transformer element of the third embodiment, processing proceeds to the state illustrated in
The semiconductor device of the third embodiment is manufactured by using a semiconductor substrate as the substrate 1 and forming the transformer element 103 on the substrate 1 by the above-described method of manufacturing the transformer element of the third embodiment.
The embodiments can be combined, appropriately modified or omitted, without departing from the scope of the disclosure.
While the disclosure has been illustrated and described in detail, the foregoing description is in all aspects illustrative and not restrictive. It is therefore understood that numerous modifications and variations can be devised without departing from the scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-028032 | Feb 2022 | JP | national |
