JP6508679B2 - Electronic device - Google Patents

Description

  The present invention relates to an electronic device in which a current path is interrupted when an overcurrent flows, and more particularly to an electronic device in which a soluble conductor is provided in the current path and the current path is interrupted by melting the soluble conductor.

  A fuse element which is an electronic device provided with a fusible conductor in a current path is widely used for the purpose of characteristic adjustment of an electronic circuit connected to the current path and protection from an overcurrent.

  In a general fuse element 20, a fusible conductor 21 formed of a metal thin film on an insulating film is formed in a shape as shown in FIG. 8, and an overcurrent is applied to the fusible conductor 21 or a laser beam is applied. By the irradiation, the fusing part 22 is fused. In addition, an example in which this type of fuse element is configured by a MEMS (Micro Electro Mechanical Systems) element is also proposed, and a MEMS micro fuse is disclosed in Patent Document 1. In general, in a fuse element, a fusible conductor which has been once melted and becomes nonconductive is not used again as a current path.

  On the other hand, in the semiconductor integrated circuit, in order to protect the internal circuit from electrostatic discharge, an ESD protection element composed of a PN diode is provided. The ESD protection element can not protect the internal circuit if it is destroyed by a single electrostatic discharge, and it is necessary to protect the internal circuit even when the electrostatic discharge occurs repeatedly. Therefore, although the fuse element may be used as a component of a protection circuit, it is not used as an ESD protection element itself.

Japanese Patent Application Publication No. 2006-514786

  Conventional fuse elements can not be used again as current paths once they are blown. An object of the present invention is to provide an electronic device which can be used also as an ESD protection element while another current path remains even if it is once blown like a fuse element.

  In order to achieve the above object, the invention according to claim 1 of the present application is an electronic device including a soluble conductor in a current path, and the current path being blocked by melting the soluble conductor. A first soluble conductor includes a first soluble conductor and a second soluble conductor, the first soluble conductor includes a plurality of soluble conductor pieces, and opposite to the tip of each soluble conductor piece The end is connected to the first wiring, and the second fusible conductor includes a plurality of fusible conductor pieces, and the end opposite to the tip of each fusible conductor piece is the first And the fusible conductor piece is provided with a constriction portion to be a fusing portion between the tip end portion and the connection portion between the first wiring and the second wiring. And the tip of the fusible conductor of the first fusible conductor and the tip of the fusible conductor of the second fusible conductor are spaced apart from each other. Characterized in that it is a arranged a free end.

  The invention according to claim 2 is the electronic device according to claim 1, wherein the soluble conductor is formed on an insulating film, and a space from which at least a part of the insulating film is removed or a space on the insulating film The tip end is disposed at the free end, and the narrowed portion is disposed on the insulating film.

  In the electronic device of the present invention, when a large voltage is applied, a discharge occurs between the first fusible conductor piece and the second fusible conductor piece, and a current equal to or greater than the allowable current density flows in the current path to Melting occurs and this pathway is broken. However, according to the present invention, since a plurality of fusible conductor pieces are provided, the fusible conductor pieces remaining without being melted and cut form another current path, and can be repeatedly operated.

  Further, in the electronic device of the present invention, the discharge start voltage can be adjusted by adjusting the separation dimension of the pair of soluble conductor pieces, and the allowable current density can be adjusted by adjusting the dimension of the narrowed portion. The blocking capacity can be easily adjusted when used as

  Furthermore, the electronic device of the present invention can also be used, for example, as a protection circuit of a semiconductor integrated circuit, and high speed response is possible because parasitic capacitance that can not be avoided when the protection circuit is configured with a diode which is a semiconductor element does not exist. Has the advantage of being able to realize

  Furthermore, the electronic device of the present invention can be configured as a MEMS element structure that can be miniaturized, and can be handled like ordinary electronic components. For example, if all current paths are melted and can not be used, the electronic device can be used to replace it with a new electronic device, and the frequency of replacement can be significantly reduced compared to the prior art. It has the advantage of being able to

It is explanatory drawing which showed typically the soluble conductor of the electronic device of this invention. It is a figure explaining the manufacturing process of the fuse element of the example of the present invention. It is a figure explaining the manufacturing process of the fuse element of the example of the present invention. It is a figure explaining the manufacturing process of the fuse element of the example of the present invention. It is a figure explaining the manufacturing process of the fuse element of the example of the present invention. FIG. 7 is a drawing for explaining the manufacturing process of another fuse element of the embodiment of the present invention. It is explanatory drawing in the case of using the fuse element of the Example of this invention as a protection element. It is explanatory drawing of a general fuse element.

  The electronic device according to the present invention has a configuration in which the fusible conductor forming the current path has a predetermined shape, so that even when a fusible conductor is partially melted, the fusible conductor can be repeatedly used a predetermined number of times. . Specifically, an explanatory view schematically showing the soluble conductor of the present invention is shown in FIG. Fig.1 (a) is a top view, FIG.1 (b) has shown sectional drawing which passes along the center of either of a soluble conductor piece. As shown in FIG. 1 (a), the soluble conductors formed in the current path are composed of the first soluble conductor 1 and the second soluble conductor 2 separated from each other, and these are further soluble The conductor pieces 1a to 1c and 2a to 2c are respectively provided. Although FIG. 1 shows the case where three pieces of fusible conductor are formed, it is sufficient to have a structure having two or more pieces of fusible conductor, and the number is not limited. Each of the fusible conductor pieces is connected to the first wire 3a or the second wire 3b at the end opposite to the tip. Further, in the fusible conductor pieces 1a to 1c and 2a to 2c, a narrowed portion 4 is formed between the connection portion of the first or second wiring 3a or 3b and the tip portion 1p or 2p. The narrowed portion 4 is disposed on the insulating film 6 described later.

  FIG. 1 (b) shows a cross-sectional view. The tip portions 1p and 2p of the respective fusible conductor pieces are disposed on the substrate 5 and the cavity 7 formed by removing a part of the insulating film 6 on the substrate 5 and are free ends. The cavity 7 may have a space enough to be discharged in the air when discharge occurs between the tip portions 1p and 2p of the fusible conductor pieces, and the substrate 5 penetrates as shown in FIG. 1 (b). You do not have to.

  According to this structure, when an overvoltage is applied to the current path between the first wiring 3a and the second wiring 3b, one tip portion of the fusible conductor piece of the first fusible conductor and the second A discharge occurs between the tip of one of the fusible conductor pieces of the fusible conductor, and when the current flowing in the fusible conductors 1 and 2 exceeds the allowable current density, melting occurs at the narrowing portion 4 of the fusible conductor pieces Do. At this time, the discharge occurs only between the pair of soluble conductors in which the discharge first started, and the discharge does not occur simultaneously in two or more pairs of movable conductor pieces. Therefore, since the first soluble conductor 1 and the second soluble conductor 2 respectively have a plurality of soluble conductor pieces, it is possible to form a state in which a current path is formed by the soluble conductor pieces that are not fused. I keep it. Therefore, unlike the conventional fuse element, it can not be used by one blow, but can be repeatedly used at least as many as the number of pairs of soluble conductor pieces. Hereinafter, examples of the present invention will be described in detail.

  The first embodiment of the present invention will be described according to the manufacturing process for the case where a fuse element is configured as an electronic device. First, silicon is thermally oxidized to form an insulating film 6 on the surface of a substrate 5 made of, for example, silicon. Thereafter, a polysilicon film is laminated on the insulating film 6 by the CVD method. This polysilicon film is a conductive film. Thereafter, predetermined patterning including the first soluble conductor 1, the second soluble conductor 2, the first wiring 3a and the second wiring 3b is performed (FIG. 2). Here, the first and second soluble conductors 1 and 2 are provided with soluble conductor pieces 1a to 1c and 2a to 2c as shown in FIG. Have a structure. Here, the dimensions of the constricted portion 4 and the thickness of the fusible conductor piece are set such that melting occurs in the constricted portion 4 when the current value of the allowable current density is exceeded. The first soluble conductor 1 and the second soluble conductor 2 and the first wiring 3a and the second wiring 3b do not necessarily have to be formed of the same conductive film, but in separate steps, Furthermore, it may be formed of another metal film.

  The dimension between the tip portion 1p of the first fusible conductor piece and the tip portion 2p of the second fusible conductor piece is set so as to have characteristics required as a fuse element. It is desirable that the tip be formed at an acute angle so that discharge always occurs at the tip. Specifically, when the dimension between the tip of the first fusible conductor and the tip of the second fusible conductor opposite to each other is 0.1 to 0.5 μm, discharge at about 10 to 20 V Is started. At this time, if the narrowed portion 4 has a width of 1 to 10 μm, melting can be performed.

  Next, an oxide film is laminated on the entire surface by the CVD method. Thereafter, at least a portion of the first wiring 3a and the second wiring 3b serving as electrodes for connection to other circuits and the like are exposed, and the narrowed portion 4 is exposed, and the narrowed portion 4 and the fusible conductor piece The oxide film is patterned so as to surround 1 and 2 to form a frame 8. Since the narrowed portion 4 is a melting portion, it is desirable that the narrowed portion 4 be disposed on the insulating film 6 and not be covered by the frame 8 and be exposed. Further, a part of the insulating film 6 on the back surface of the substrate 5 is removed to expose the back surface side of the substrate 5 in the cavity formation planned region (FIG. 3).

  Using the insulating film 6 left on the back side of the substrate 5 as an etching mask, the exposed part of the substrate 5 and the insulating film 6 are etched away to form a cavity 7 (FIG. 4). Due to the formation of the cavity 7, the tip portions 1p, 2p of the fusible conductor piece become free ends free of the supported substrate and the like.

  Thereafter, a film resist is attached on the surface frame 8 and patterned into a predetermined shape, whereby the lid 9 is formed (FIG. 5).

  The fuse element thus formed is surrounded by the frame 8 and in the area covered by the lid 9, the first fusible conductor piece constituting the first fusible conductor 1 is on the cavity 7 from the left side of the drawing. The second fusible conductor piece constituting the second fusible conductor 2 extends from the right side of the drawing onto the cavity 7. As shown in FIG. 5, the tip portion 1P of the first soluble conductor piece of the first soluble conductor 1 and the tip portion 2P of the second soluble conductor piece constituting the second soluble conductor 2 They are opposite free ends separated by a fixed size. The narrowed portion 4 is formed on the insulating film 6 in a region surrounded by the frame 8.

  In the fuse element having such a structure, when a predetermined voltage is applied between the first wiring 3a and the second wiring 3b, the tip portion of one fusible conductor piece of the first fusible conductor 1 A discharge occurs between 1p and the tip 2p of one fusible conductor piece of the second fusible conductor 2, and an overcurrent flows in both fusible conductor pieces. Here, when a current equal to or higher than the allowable current density flows, the narrowed portion 4 of the fusible conductor piece for which the current density is the highest is melted down. Thus, the current path is interrupted between the two fusible conductor pieces through which the overcurrent flows, and the fuse element functions.

  Here, the combination of the soluble conductor pieces in which the discharge occurs is limited to the combination in which the discharge first occurs, and the discharge does not occur simultaneously between the other soluble conductor pieces. Therefore, the current path is formed by the combination of other soluble conductor pieces. As described above, in this embodiment, unlike the conventional fuse element, it can not be used by one blow, and can be used repeatedly as many as the number of combinations of fusible conductor pieces.

  Since the electronic device of the present invention is a MEMS element, it is easy to replace it with another electronic device if all fusible conductor pieces are fused. Also, this replacement frequency can be significantly reduced.

  The following second embodiment will be described. In the first embodiment, the case where the end 1p2p of the fusible conductor is made free by the cavity 7 formed by etching away a part of the substrate 5 has been described, but the free end is made by another method It is also possible.

  In FIG. 6A, after forming the insulating film 6 by thermal oxidation on the surface of the substrate 5 described in FIG. 2 of the first embodiment, a sacrificial layer 10 is formed, and then a conductive polysilicon film is formed. It shows a state in which predetermined patterning including the first soluble conductor 1, the second soluble conductor 2, the first wiring 3 a and the second wiring 3 b is performed. The shapes of the first soluble conductor 1 and the second soluble conductor 2 are the same as those in the above-described embodiment.

  Thereafter, when the sacrificial layer 10 is etched away, the tips 1p and 2p can be made free ends. If it is formed by such a method, it becomes possible to form very simply in comparison with the method of forming the cavity 7 by etching and removing a part of the substrate 5 (FIG. 6b).

  There is no problem in the space from which the sacrificial layer 10 has been removed as long as discharge can occur between the tip 1p of the first fusible conductor piece and the tip 2p of the second fusible conductor.

  A third embodiment will now be described. It is also possible to use the fuse element described in the first or second embodiment as an ESD protection circuit of a semiconductor device. For example, as shown in FIG. 7, the fuse element described in the first embodiment is connected to a semiconductor integrated circuit 12 having an input terminal 11. That is, the fuse element 13 connects the first wiring 3a to the input terminal 11 of the semiconductor integrated circuit 12 to be a protected circuit, and connects the second wiring 3b to the power supply voltage. For example, one fuse element 13 is connected to the power supply voltage Vss, and the other fuse element 13 is connected to the ground potential.

  In the semiconductor integrated circuit 12 provided with the ESD protection circuit configured as shown in FIG. 7, when a surge voltage is applied to the input terminal 11, the first fusible conductor piece to the second via the first wiring 3a are used. A discharge is generated in the fusible conductor piece, and an electrostatic discharge current flows in the second wiring 3b. When the electrostatic discharge current becomes equal to or higher than the allowable current density, the narrow portion 4 of the fusible conductor piece is melted and energy of the surge current is consumed, and the internal elements of the semiconductor integrated circuit can be prevented from being broken.

  The fuse element 13 of the present invention is provided with a plurality of fusible conductor pieces, so that the fusible conductor pieces which are not melted are kept in a state in which the current path is formed. It becomes usable. In addition, when all the current paths become unusable, it becomes usable again by replacing only the fuse element 13.

  Furthermore, since the fuse element 13 of the present invention does not have parasitic capacitance, it becomes a protection element capable of high-speed response.

  As described above, in the electronic device of the present invention, the current path can be interrupted by melting the soluble conductor in the same manner as a general fuse element. On the other hand, unlike a general fuse element, it can not be used by one blow and can be used multiple times. After all the fusible conductors are fused, they can be replaced as parts separate from the semiconductor integrated circuit 12, and there is no problem in continuous use.

1: first soluble conductor, 1a to 1b: first soluble conductor piece, 2: second soluble conductor, 2a to 2c: second soluble conductor piece, 3a: first wiring, 3b Reference numeral 2: second wiring, 4: narrow portion, 5: substrate, 6: insulating film, 7: cavity, 8: frame, 9: lid, 10: sacrificial layer, 11: input terminal, 12: semiconductor integrated circuit, 13 20: Fuse element 21: Soluble conductor 22: Fused part

Claims (2)

In an electronic device including a fusible conductor in a current path, and the fusible conductor being melted and cut off the current path,
The fusible conductor includes a first fusible conductor and a second fusible conductor.
The first fusible conductor includes a plurality of fusible conductor pieces, and the end opposite to the tip of each fusible conductor piece is connected to the first wiring;
The second fusible conductor includes a plurality of fusible conductor pieces, and an end opposite to a tip of each fusible conductor piece is connected to the second wiring.
The fusible conductor piece includes a constriction portion to be a fusing portion between the tip portion and a connection portion between the first wiring and the second wiring.
The tip end of the fusible conductor piece of the first fusible conductor and the tip end of the fusible conductor piece of the second fusible conductor are free ends which are disposed to be opposed to each other. An electronic device characterized by   The electronic device according to claim 1, wherein the soluble conductor is formed on an insulating film, and the free end is disposed in a space from which at least a part of the insulating film is removed or a space on the insulating film. An electronic device, wherein the narrowed portion is disposed on the insulating film.

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