JPH11186381A - Wiring structure and method of forming the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce wiring capacitance at intersections and wiring resistance, by providing insulative support member at an air region between a first and a second wirings for blocking the first wiring from contacting the second wiring. SOLUTION: A second wiring 20 is disposed at predetermined distance from a first wiring 12 through a space 26 between the wirings 20, 12, and an insulative support member 24 for supporting so as to block the first wiring 12 from contacting the second wiring 20 is provided in this space 26, thereby insulating the first wiring 12 from the second wiring 20 to reduce wiring capacitance. The support member 24 for supporting the first and the second wirings 121, 20 blocks the distance from narrowing between the first and the second wirings 12, 20 to avoid contacting the first wiring 12 to the second wiring 20, thereby reducing the wiring resistance at intersections in an expanded configuration of the first wiring 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a wiring structure and a method for forming the same, and more particularly, to an air bridge wiring in a semiconductor integrated circuit and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, an MMI which is a high-frequency device
When two wirings cross each other in a wiring structure such as C without electrically connecting them, the other wiring jumps over one wiring so as not to contact one wiring, and air is blown between the two wirings. An existing air bridge structure has been proposed. This air bridge structure uses Si between two wirings.
Instead of insulating with an insulating member such as O ₂ or SiN,
By insulating with air, the wiring capacitance at the intersection position is reduced and the high frequency characteristics of the MMIC are improved.

FIG. 6 is a schematic explanatory view showing such an air bridge structure. FIG. 6 shows a state cut along the length direction of a second wiring 52 intersecting the first wiring 51 at an angle of 90 °. FIG. As shown in FIG. 5, at the intersection of the first wiring 51 and the second wiring 52, the second wiring 52 is arranged at a predetermined distance from the first wiring 51. In other words, the second wiring 52 is formed to jump over the first wiring 51 so as not to contact the first wiring 51. Therefore, the first wiring 51 and the second wiring 52
A space 56 is formed between the first wiring 51 and the second wiring 52. Air existing in the space 56 insulates the first wiring 51 from the second wiring 52.

[0004]

However, in such an air bridge structure, when the width of the first wiring is increased to reduce the wiring resistance, the first wiring is skipped so as not to come into contact with the first wiring. The mechanical strength of the formed second wiring is weakened. That is, since the width of the first wiring is widened, the length of the second wiring jumping over the first wiring at the intersection position is increased, and the second wiring is easily bent.
In some cases, the short circuit may occur due to contact with the first wiring. Therefore, the air bridge structure having the above configuration has a problem that there is a limit in reducing the wiring resistance.

In view of the above, it is an object of the present invention to provide a wiring structure and a method for forming the wiring structure, in which the wiring capacitance at the intersection position is small and the wiring resistance can be reduced.
It is another object of the present invention to provide a wiring structure with improved mechanical strength at the intersection position and a method for forming the same.

[0006]

In order to achieve the above object,
The invention according to claim 1 is a wiring structure at a crossing position of at least two wirings of a first wiring and a second wiring provided along the same plane, wherein the second wiring is connected to the first wiring. The first wiring and the second wiring are arranged at a predetermined distance from the first wiring with air interposed therebetween, and in an air intervening region between the first wiring and the second wiring. An insulating support member for supporting the contact member so as to prevent the contact is provided.

According to a first aspect of the present invention, there is provided a wiring structure in which a wiring capacity is reduced by a configuration in which a space between a first wiring and a second wiring is insulated by air. An insulating support member is provided in the intervening region, and the insulating support member supports the first wiring and the second wiring, thereby preventing the distance between the first wiring and the second wiring from being reduced. ,
The contact between the first wiring and the second wiring is prevented.

That is, the amount of bending of the second wiring is limited by the support member, and the distance between the first wiring and the second wiring is maintained so as not to be less than a predetermined value. Short circuit due to contact with wiring can be prevented. Of course, the mechanical strength at the intersection of the second wiring itself is also reinforced.

Therefore, even if the width of the first wiring arranged on the lower side is increased, the bending of the second wiring provided above the first wiring so as to jump over the first wiring is suppressed.
There is no problem such that the wiring and the second wiring come into contact with each other and short-circuit between the wirings. This makes it possible to reduce the wiring resistance at the intersection position as a configuration in which the wiring width of the first wiring is wider than in the related art. Of course, there is also an advantage that the strength of the entire intersection structure between the first wiring and the second wiring is increased.

The distance between the first wiring and the second wiring is determined in advance while the first wiring and the second wiring are insulated at the intersection of the first wiring and the second wiring. For example, the lower end is connected to the upper surface of the first wiring, the upper end is connected to the lower surface of the second wiring, and the distance between the first wiring and the second wiring is arranged first. A configuration in which the distance is maintained, or a lower end is connected to the upper surface of the first wiring and an upper end is disposed between the first and second wirings, and the upper end is a lower surface of the second wiring when the second wiring is bent. A configuration in which the distance between the first wiring and the second wiring is not shorter than its own height by being supported in contact with the side;
The upper end is connected to the upper surface of the second wiring, the lower end is disposed between the first wiring and the second wiring, and when the second wiring is bent, the lower end contacts the upper surface of the first wiring to form the second wiring. One having a configuration for supporting the member so as not to bend further can be used. Of course, the number of support members is not limited to one, and a plurality of support members can be provided in accordance with the width of the first wiring and the second wiring to be formed, the length of the second wiring jumping over the first wiring, and the like.

According to a second aspect of the present invention, in the wiring structure according to the first aspect, the support member has one end connected to the first wiring and the other end connected to the second wiring. It is characterized by.

That is, according to the second aspect of the present invention, one end of the insulating support is connected to the first wiring, and the other end is connected to the second wiring, and the distance between the first wiring and the second wiring is initially set. In this configuration, the strength at the intersection of the second wirings is increased, the bending of the second wirings is significantly suppressed, and the second wirings are strong against the load applied from the side surface direction of the second wirings. There is an advantage that it becomes. Therefore, there is an advantage that a short circuit due to contact between the first wiring and the second wiring does not occur as compared with the related art.

According to a third aspect of the present invention, in the wiring structure according to the first aspect, the supporting member has one end connected to one of the first wiring and the second wiring and the other end connected to the other wiring. An end is provided apart from the other wiring of the first wiring or the second wiring, and when the second wiring is bent, the other end comes into contact with the other wiring to form the second wiring. It is characterized by supporting.

That is, according to the third aspect of the present invention, the supporting member does not connect the first wiring and the second wiring, but is connected to the upper surface of the first wiring and separated from the lower surface of the second wiring.
Since the connection is made to the lower surface of the wiring and away from the upper surface of the first wiring, the first wiring is connected to the first wiring in comparison with the case where the second wiring is connected.
The parasitic capacitance between the wiring and the second wiring can be reduced.
Therefore, there is a new advantage that the high frequency characteristics are not impaired when applied to the wiring structure of the MMIC. Of course, since the support member is configured to support the second wiring when the second wiring is bent, there is an advantage that a short circuit due to contact between the first wiring and the second wiring does not occur as compared with the related art.

According to a fourth aspect of the present invention, an insulating film is formed on a substrate having a first wiring formed in close contact with the surface until the first wiring is buried, and a region where the second wiring is to intersect is formed. Removing the insulating film and forming a dummy pattern made of an insulating material; forming a metal film on the surface of the substrate on which the dummy pattern has been formed; and patterning the metal film to form a second wiring passing over the dummy pattern. Forming a second wiring, and forming the second pattern on the dummy pattern.
The first wiring and the second wiring are formed by forming a mask on a part of the side surface of the wiring and etching the dummy pattern in a direction parallel to the substrate surface from the side surface on which the mask is formed.
A supporting member forming step of forming an insulating supporting member for supporting the first wiring and the second wiring so as to prevent contact between the wiring and the first wiring.

According to a fourth aspect of the present invention, there is provided a method for forming the wiring structure according to any one of the first to third aspects. First, in a dummy pattern forming step, a dummy pattern having a spatial shape to be formed between the first wiring and the second wiring is first formed of an insulating material.
After forming on the wiring, the second wiring is formed in the second wiring forming step.
Wiring is formed on the dummy pattern. Thereafter, in a supporting member forming step, a mask having a predetermined height in a direction from the upper surface of the first wiring to the lower surface of the second wiring is formed on a part of the dummy pattern on the side surface of the second wiring, and from the side surface on which the mask is formed. Etching (side etching) in a direction parallel to the substrate surface. As a result, a columnar support member protruding from the upper surface of the first wiring toward the second wiring is formed.

The arrangement of the support members is determined by the mask formation region, and the intended arrangement of the support members can be easily controlled by adjusting the mask formation region. For example, when the mask formation region is a region extending from the upper surface of the first wiring to the lower surface of the second wiring, one end of the obtained support member is connected to the upper surface of the first wiring, and the other end is connected to the lower surface of the second wiring so that the first member is connected to the first wiring. In the case where the distance between the wiring and the second wiring is maintained at the initially set distance relationship, and the mask formation region is a region from the upper surface of the first wiring to an intermediate position between the first wiring and the second wiring. The obtained supporting member has one end connected to the upper surface of the first wiring, the other end disposed between the first wiring and the second wiring, and the other end disposed on the lower surface of the second wiring when the second wiring is bent. Contact with the second
This is a configuration that supports the wiring. Of course, if the shape of the mask is made large, the resulting support member will also be large. That is, by controlling the formation position and the shape of the mask, a support member having a desired shape can be easily formed at a desired position.

This mask may be provided on both sides of the dummy pattern on the side surface of the second wiring, respectively.
It may be provided only on one side, and as an etching method at this time, use of reactive ion etching (hereinafter referred to as RIE) or anisotropic dry etching such as ion milling may be used. When a mask is provided on both sides of the dummy pattern, etching can be performed from both sides. In addition to the anisotropic dry etching, an etching method such as isotropic dry etching and isotropic wet etching is also used. be able to.

According to a fifth aspect of the present invention, an insulating film is formed on a substrate having a first wiring formed in close contact with the surface until the first wiring is buried, and the insulating film is formed to intersect with the second wiring. A supporting member forming step of forming an insulating supporting member on the first wiring by removing the insulating film while leaving a part of the region, and forming a resist film on the substrate on which the supporting member is formed. Then, the dummy film is formed by removing the resist film while leaving a region where the second wiring on the first wiring is to intersect with the second wiring to form a dummy pattern made of a resist having a support member inserted therein, and the dummy pattern is formed. Forming a metal film on the surface of the substrate, and patterning the metal film to form a second wire passing over the support member; and a dummy pattern between the first wire and the second wire. To And removing a dummy pattern by etching.

According to a fifth aspect of the present invention, there is provided a method for forming the wiring structure according to any one of the first to third aspects. First, after forming an insulating film on the first wiring in the supporting member forming step, a columnar supporting member made of an insulating material is formed on the first wiring using a lift-off method or the like. At this time, the support member can be formed at a plurality of locations on the upper surface of the first wiring according to the design such as the wiring width.

Thereafter, in a dummy pattern forming step, a resist film is formed to a thickness set in advance based on the positional relationship between the support member and the second wiring, and then a space is formed between the first wiring and the second wiring. The resist is etched into a shape to form a dummy pattern.

In the case where the resist film is formed so that the support member is filled with the resist film, if the resist is molded so that the support member protrudes or is exposed on the upper surface, the support member becomes the second wiring formed on the resist. If the resist is molded so as not to project or expose the support member on the upper surface, the support member is not connected to the second wiring. That is, the configuration of the support member finally obtained is determined by the resist molding state at this time. When a resist film is formed so that the insulating support film is not buried in the resist film, the structure is such that the insulating support film and the second wiring are always connected.

Thereafter, a second wiring is formed on the dummy pattern so as to be connected to the supporting member or to pass through the upper layer of the supporting member in the second wiring forming step, and then the resist is removed by etching in the dummy pattern removing step. Connecting the first wiring and the second wiring, or
A wiring structure having a columnar support member protruding from the upper surface of the first wiring toward the second wiring between the wiring and the second wiring is obtained.

As described above, in the invention of claim 5, the first
Since the second wiring is formed using the resist after forming the supporting member on the wiring, there is an advantage that the formation position of the supporting member can be accurately adjusted. Of course, there is also an advantage that even when the support member is formed at a plurality of positions, it can be formed easily and accurately at the designed position.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. All figures are cross-sectional views showing a state where the first wiring and the second wiring provided on the semiconductor substrate are cut along the length direction of the second wiring when the first wiring and the second wiring intersect at an angle of 90 °. In all the drawings, the same or corresponding parts are denoted by the same reference numerals. (First Embodiment) FIG. 1 is a flowchart schematically showing a process of forming a wiring structure according to a first embodiment. Hereinafter, a brief description will be given with reference to FIGS.

First, a first wiring pattern is formed on the semiconductor substrate 10 using a resist (not shown), and then a conductive film of Ti / Pt / Au is formed on the upper surface of the semiconductor substrate 10. The Ti / Pt / Au film has a thickness of 50 n
After depositing until the film thickness reaches m, Pt is deposited until the film thickness becomes 50 nm, and further, Au is deposited until the film thickness becomes 1000 nm. After the formation of the Ti / Pt / Au film, the resist is removed to obtain the semiconductor substrate 10 on which the first wiring 12 made of the Ti / Pt / Au laminated film is formed.

Next, a polyimide (for example, polyimide PI-2) is formed on the upper surface of the semiconductor substrate 10 on which the first wiring 12 is formed.
610D (manufactured by DuPont, trade name)) with a thickness of 1 μm
And coat at 150 ° C for 30 μm or less.
The polyimide film 14 is an insulating film by heating for
Is formed (see FIG. 1A).

Thereafter, a positive resist (for example, OFPR
800 (trade name, manufactured by Tokyo Ohkasha Co., Ltd.) is applied to the upper surface by about 1 μm. After the positive resist is applied, the polyimide film 14 in the intersection region with the second wiring 20 to be formed later remains in a rectangular shape and forms a precursor of a dummy pattern, and is exposed to light by shielding the light corresponding to the intersection region. (For example, NMD-3
(Manufactured by Tokyo Ohkasha Co., Ltd.). At this time, the polyimide film 14 other than the intersection region with the second wiring 20
Is removed by a developing solution together with a resist (not shown), so that a rectangular positive resist 1
6, the polyimide film 14a in a region covered with the rectangular positive resist 16 and the polyimide film 14a
The first wiring 12 which is partially wrapped is left (see FIG. 1).
(B)).

Then, after removing the rectangular positive resist 16 with acetone, the substrate is heated at 350 ° C. for about 1 hour.
At this time, the rectangular polyimide film 14a is shrunk by the high temperature, and a dummy pattern of the polyimide film 14a having a smooth side surface is formed as shown in FIG.

Thereafter, Ti is deposited on the upper surface of the semiconductor substrate 10 to a thickness of 50 nm, and Au is deposited on the upper surface of the semiconductor substrate 10 to a thickness of 50 nm by electron beam deposition or sputter deposition. Au
Film). Further, after a pattern of the second wiring 20 is formed on the semiconductor substrate 10 using a resist (not shown), an Au film as a metal film is formed by electrolytic plating until the thickness becomes about 1 μm or more and 3 μm or less. Thereafter, the current film 18 in a region other than the resist pattern and the second wiring 20 is removed by ion milling using an inert gas such as Ar or Xe.

Of course, the thickness of the Au film serving as the second wiring 20 is about 1 μm or more and 3 μm or less, and the Ti film and the Au film forming the current film 18 (Ti / Au film) are 50 nm each. There is no need to worry that the Au film serving as the second wiring 20 is completely removed when the film 18 is removed. Thus, the semiconductor substrate 10 in which the second wiring 20 is formed above the first wiring 12 via the polyimide film 14a and the current film 18 is obtained (see FIG. 1D).

On the obtained semiconductor substrate 10, a flat mask 22 extending vertically from the upper surface of the first wiring 12 is applied to the second
It is provided so as to cover a part of the side surface of the wiring 20 and a part of the side surface of the dummy pattern by the polyimide film 14a (FIG. 1).
(E)).

Thereafter, ashing is performed by oxygen plasma from the side surface of the second wiring 20 in a direction parallel to the substrate plane (in a direction in which the first wiring 12 extends, that is, in FIG. 1, from the near side to the paper surface). The polyimide film 14a between the first wiring 12 and the second wiring 20 is removed by an etching process (side etching) to form a space 26 which is an air intervening region. At this time, the masked polyimide portion remains without being etched, and this portion becomes the support portion 24 which is a support member that connects the upper surface of the first wiring 12 and the lower surface of the second wiring 20 while maintaining insulation. . This allows
In a space 26 between the first wiring 12 and the second wiring 20, there is provided a wiring structure having a column 24 having one end connected to the upper surface of the first wiring 12 and the other end connected to the lower surface of the second wiring 20. (See FIG. 1 (f)).

In the above, the polyimide film 14 formed on the first wiring 12 is masked with a resist, and the other area is removed by exposing and developing to remove the polyimide film 14a from the rectangular polyimide film 14a remaining on the substrate. The method of forming the dummy pattern to be formed has been described. However, a photosensitive polyimide that is cured by exposure is formed on the first wiring 12 and only the dummy pattern formation region of the photosensitive polyimide film is exposed and developed to form the first pattern. A method of forming a dummy pattern on the wiring 12 may be used.

The process of forming a dummy pattern composed of a rectangular polyimide film 14a having a smooth side surface as shown in FIG. 1C using a photosensitive polyimide film will be briefly described below. .

First, polyimide PI-2703D (trade name, manufactured by DuPont) is applied on the substrate on which the first wiring 12 is formed so as to have a thickness of 1 μm or more and 3 μm or less. Heat treatment (pre-bake) for 3 minutes to form a polyimide film. Next, the polyimide film is partially cured by irradiating light to an intersection region with a second wiring to be formed later. Thereafter, development is performed to remove the polyimide film other than the light irradiation region, and the polyimide film in the light irradiation region is left as a dummy pattern on the upper surface of the semiconductor substrate. Thereafter, the polyimide forming the dummy pattern is fully cured by heat treatment at 350 ° C. for about 1 hour, and the rectangular polyimide film is shrunk by high temperature, so that the side surface inclination is smooth as shown in FIG. A polyimide film having a shape is formed.

As shown in the perspective views of FIGS. 1F and 2, the wiring structure obtained by the above-described steps includes the first wiring 12 provided on the semiconductor substrate 10 and the first wiring 12. One end is connected to the upper surface of the first wiring 12 in a space 26 between the second wiring 20 and the second wiring 20 crossing at an angle of 90 ° with respect to
The other end is provided with the support portion 24 connected to the lower surface of the second wiring 20. Since the support portion 24 is formed of an insulating film, the first wiring 12 and the second wiring 20 are connected in an insulated state. For this reason, the second wiring is supported by the support portion 24 at a predetermined distance from the first wiring 12, and the bending of the second wiring is suppressed, so that the mechanical strength of the entire cross wiring structure can be improved. .

Therefore, the line width of the first wiring can be designed without being affected by the limit of the mechanical strength of the second wiring 20, so that the line width of the first wiring 12 is increased and the wiring resistance becomes a target value. Can be reduced. (Second Embodiment) FIG. 3 is a flowchart schematically showing a process of forming a wiring structure according to a second embodiment. Hereinafter, a brief description will be given with reference to FIGS.

First, a first wiring 12 made of a Ti / Pt / Au film is formed on a semiconductor substrate 10 by a method similar to the method described in the first embodiment. Next, the semiconductor substrate 1
An SiN film 15 as an insulating film is formed on the upper surface by plasma CVD until the thickness becomes about 1 μm or more and 3 μm or less. Thereafter, a mask 22 made of a photoresist is formed on the upper surface of the SiN film 15 at a position to be connected to the second wiring 20 (see FIG. 3A).

[0040] The photoresist SiN film 15 in the region where the mask 22 is not formed by using a SF ₆ gas R
Remove by IE. Subsequently, the mask 22 made of photoresist is removed, and SiN as a support member is formed on the first wiring.
The support 24 is formed (see FIG. 3B).

Thereafter, the OFPR is used until the support portion 24 is filled.
A positive resist such as 800 is applied. After the application of the positive resist, the positive resist in the intersection region with the second wiring 20 to be formed later remains in a rectangular shape and forms a precursor of the dummy pattern.
3 and developed with a developer such as
6 is formed as a dummy pattern precursor (FIG. 3C).
reference). After that, the upper surface of the positive resist film 16 is etched by oxygen plasma until the support portion 24 is exposed, and then heated at a temperature of 120 ° C. or more and 140 ° C. or less for about 3 minutes to reflow the positive resist film 16 to reduce the inclination of the side surface. Then, a dummy pattern is formed by the positive resist film 16 (see FIG. 3D). When the upper surface of the positive resist film 16 is etched by oxygen plasma, the positive resist film 16 may be reflowed. In such a case, the reflow process is not performed.

Thereafter, Ti is deposited on the upper surface of the semiconductor substrate 10 to a thickness of 50 nm and Au is deposited to a thickness of 50 nm by electron beam deposition or sputter deposition. Au
Film). Further, after a pattern of the second wiring 20 is formed on the semiconductor substrate 10 using a resist (not shown), an Au film as a metal film is formed by electrolytic plating until the thickness becomes about 1 μm or more and 3 μm or less. Thereafter, the current film 18 in a region other than the resist pattern and the second wiring 20 is removed by ion milling using an inert gas such as Ar or Xe to form the second wiring 20 made of Au. Of course, the thickness of the Au film serving as the second wiring 20 is about 1 μm or more and 3 μm or less.
Since each of the Ti film and the Au film forming 8 (Ti / Au film) has a thickness of 50 nm, there is no concern that the removal of the current film 18 and the removal of the entire Au film serving as the second wiring 20 will also occur. As a result, the positive resist 16, the support 24, and the current film 1 are formed on the first wiring 12.
The semiconductor substrate 10 on which the second wiring 20 is formed is obtained through the intermediary 8 (see FIG. 3E).

Thereafter, the obtained semiconductor substrate 10 is ashed by oxygen plasma to form the first wiring 12 and the second wiring 2.
The positive resist 16 between 0 and 0 is removed to form a space 26 that is an air intervening region. At this time, since the support portion 24 remains without being removed, the upper surface of the first wiring 12 and the second wiring 20 are not removed.
(See FIG. 3 (f)).

As shown in FIG. 3F, the wiring structure obtained by the above-described steps has a structure in which the first wiring 12 provided on the semiconductor substrate 10 is 90 ° away from the first wiring 12.
One end is connected to the upper surface of the first wiring 12 and the other end is connected to the space 26 between the second wiring 20 and
Is provided with the support portion 24 connected to the lower surface of the support. Since the support portion 24 is formed of an insulating film, the first wiring 12 and the second wiring 20 are connected in an insulated state.
For this reason, the second wiring is formed by the support portion 24 so as to form the first wiring 12.
The second wiring is supported at a predetermined distance from the second wiring, the bending of the second wiring is suppressed, and the mechanical strength of the entire cross wiring structure can be improved.

Therefore, the line width of the first wiring can be designed without being affected by the limit of the mechanical strength of the second wiring 20, so that the line width of the first wiring 12 is increased and the wiring resistance becomes a target value. Can be reduced.

Further, according to this method, it is possible to accurately form the support portion 24 at an arbitrary position, and there is an advantage that the degree of freedom in pattern design is increased. (Third Embodiment) FIG. 4 is a flowchart schematically showing a process of forming a wiring structure according to a third embodiment. Hereinafter, FIG.
A brief description will be given with reference to (a) to (e).

First, a first wiring 12 made of a Ti / Pt / Au film is formed on a semiconductor substrate 10 by a method similar to the method described in the first embodiment. Next, the semiconductor substrate 1
An SiN film 15 as an insulating film is formed on the upper surface by plasma CVD until the thickness becomes about 1 μm or more and 3 μm or less. Thereafter, a mask 22 made of a photoresist is formed on the upper surface of the SiN film 15 at a position where the second wiring 20 is to be connected (see FIG. 4A).

The SiN film 15 in a region not masked by the photoresist is removed by RIE using SF ₆ gas. Subsequently, the mask 22 made of the photoresist is removed to form a support portion 24 made of SiN as a support member on the first wiring (see FIG. 4B).

Thereafter, for example, a positive resist such as OFPR800 is applied to a thickness of about 2 μm or more and 3 μm or less to bury the support portion 24 in the positive resist. After the application of the positive resist, the positive resist in the intersection region with the second wiring 20 to be formed later remains in a rectangular shape and is exposed by shielding the light for the intersection region so as to form a precursor of the dummy pattern. Developing with a developer such as -3, a rectangular positive resist 16 in which the pillars 24 are embedded is formed as a dummy pattern precursor. After that, 120 ° C or more 14
By heating at a temperature of 0 ° C. or lower for about 3 minutes, the positive resist 16 is reflowed to smooth the side surfaces, and a dummy pattern is formed by the positive resist film 16 (see FIG. 4C). When the upper surface of the positive resist 16 is etched by oxygen plasma, the positive resist 16 may be reflowed. In this case, the reflow process is not performed.

Further, Ti is vapor-deposited on the upper surface of the semiconductor substrate 10 to a thickness of 50 nm and Au is vapor-deposited to a thickness of 50 nm by electron beam vapor deposition or sputter vapor deposition. Au
Film). Further, after a pattern of the second wiring 20 is formed on the semiconductor substrate 10 using a resist (not shown), an Au film as a metal film is formed by electrolytic plating until the thickness becomes about 1 μm or more and 3 μm or less.

After that, the resist pattern and the second wiring 2
The current film 18 in a region other than 0 is removed by ion milling using an inert gas such as Ar or Xe to obtain Au.
The second wiring 20 is formed. Of course, the thickness of the Au film serving as the second wiring 20 is about 1 μm or more and 3 μm or less, and the Ti film and the Au film forming the current film 18 (Ti / Au film) are each 50 nm. A which becomes the second wiring 20 upon removal
There is no worry that all of the u film will be removed. As a result, the positive resist 16 and the support 2 are formed on the first wiring 12.
The semiconductor substrate 10 on which the second wiring 20 is formed is obtained via the current wiring 4 and the current film 18 (see FIG. 4D).

Thereafter, the obtained semiconductor substrate 10 is ashed by oxygen plasma to form the first wiring 12 and the second wiring 2.
The positive resist 16 between 0 and 0 is removed to form a space 26 that is an air intervening region. At this time, since the support portion 24 remains without being removed, a wiring structure including the support portion 24 having a height protruding from the upper surface of the first wiring 12 and not contacting the lower surface of the second wiring 12 is obtained (FIG. 4E). )reference).

That is, as shown in FIG. 4E, the wiring structure obtained by the above-described process has the first wiring 12 provided on the semiconductor substrate 10 and the first wiring 12
Space 26 between the second wiring 20 crossing at an angle of 0 °
A column 2 having one end connected to the upper surface of the first wiring 12 and the other end disposed in a region between the first wiring 12 and the second wiring 20.
4 is provided. The support portion 24 is provided with the second wiring 2
0 is bent and approaches the first wiring 12, the second wiring 2
The second wiring 20 is supported from the lower surface side of 0 so that the first wiring 12 and the second wiring 20 do not approach each other. Of course, since it is formed of SiN, even when the second wiring is supported, the first wiring 12 and the second wiring 20 can be formed.
Is insulated. Further, when the second wiring 20 is bent, the second wiring 20 is supported from the lower surface side while keeping the second wiring 20 at a predetermined distance from the first wiring, so that the bending of the second wiring is suppressed, and the cross wiring is formed. The mechanical strength of the entire structure is improved. Therefore, the line width of the first wiring can be designed without being affected by the limit of the mechanical strength of the second wiring 20, so that the line width of the first wiring 12 is increased and the wiring resistance is reduced to a target value. be able to.

In addition, according to this configuration, the first wiring 12
The first wiring 12 is compared with the case where the first wiring 12 is connected to the second wiring 20.
It is possible to reduce a parasitic capacitance between the MMIC and the second wiring 20, so that there is a new advantage that high frequency characteristics of the MMIC are not impaired. (Fourth Embodiment) FIG. 5 is a flowchart schematically showing a process of forming a wiring structure according to a fourth embodiment. Hereinafter, a brief description will be given with reference to FIGS.

First, a first wiring 12 made of a Ti / Pt / Au film is formed on a semiconductor substrate 10 by a method similar to the method described in the first embodiment. Next, the semiconductor substrate 1
A SiN film 15 as an insulating film is formed on the upper surface by plasma CVD until the thickness becomes about 3 μm. afterwards,
A mask 22 made of a photoresist is formed on the upper surface of the SiN film 15 at a position where the second wiring 20 is to be connected (FIG. 5A).
reference).

The SiN film 15 in a region not masked by the photoresist is removed by RIE using SF ₆ gas. Subsequently, the mask 22 made of the photoresist is removed to form a support portion 24 made of SiN as a support member on the first wiring (see FIG. 5B).

Thereafter, for example, a positive resist such as OFPR800 is applied to a thickness of about 2 μm. At this time, since the positive resist is applied thinner than the height of the support portion 24, a thin positive resist is applied to the surface of the support portion 24 protruding from the positive resist film as shown in FIG. State or exposed state. .
Here, in order to simplify the description, a case will be described in which a thin positive resist is applied to a surface of the support portion 24 protruding from the positive resist. Of course, it is needless to say that the state where the surface of the support portion 24 is exposed has the same effect.

After the application of the positive resist, the positive resist at the intersection with the second wiring 20 to be formed later remains in a rectangular shape and is exposed to light by shielding the light so as to form the precursor of the dummy pattern. For example, development is performed using a developing solution such as NMD-3, and a rectangular positive resist 16 having a columnar portion 24 protruding from the upper surface is formed as a dummy pattern precursor.
Thereafter, the positive resist 16 is heated at a temperature of 120 ° C. or more and 140 ° C. or less for about 3 minutes to reflow the positive resist 16 to smooth the side surfaces, thereby forming a dummy pattern by the positive resist film 16 (see FIG. 5D). When the upper surface of the positive resist 16 is etched by oxygen plasma, the positive resist 16 may be reflowed. In this case, the reflow process is not performed.

Further, Ti is deposited on the upper surface of the semiconductor substrate 10 to a thickness of 50 nm and Au is deposited on the upper surface of the semiconductor substrate 10 to a thickness of 50 nm by electron beam deposition or sputter deposition. Au
Film). Further, after a pattern of the second wiring 20 is formed on the semiconductor substrate 10 using a resist (not shown), an Au film as a metal film is formed by electrolytic plating until the thickness becomes about 1 μm or more and 3 μm or less.

After that, the resist pattern and the second wiring 2
The current film 18 in a region other than 0 is removed by ion milling using an inert gas such as Ar or Xe to obtain Au.
The second wiring 20 is formed. Of course, the thickness of the Au film serving as the second wiring 20 is about 1 μm or more and 3 μm or less, and the Ti film and the Au film forming the current film 18 (Ti / Au film) are each 50 nm. A which becomes the second wiring 20 upon removal
There is no worry that all of the u film will be removed. As a result, the positive resist 16 and the support 2 are formed on the first wiring 12.
The semiconductor substrate 10 on which the second wiring 20 is formed is obtained via the current film 4 and the current film 18 (see FIG. 5E).

Thereafter, the obtained semiconductor substrate 10 is ashed by oxygen plasma to form the first wiring 12 and the second wiring 2.
The positive resist 16 between 0 and 0 is removed to form a space 26 which is an air intervening region. At this time, since the support portion 24 remains without being removed, the support portion 24
Is obtained (see FIG. 5F).

That is, as shown in FIG. 5F, the wiring structure obtained by the above-described steps has the first wiring 12 provided on the semiconductor substrate 10 and the first wiring 12 with respect to the first wiring 12.
Space 26 between the second wiring 20 crossing at an angle of 0 °
A pillar 2 having one end connected to the upper surface of the first wiring 12 and the other end entering the inside of the second wiring from the lower surface of the second wiring 20.
4 is provided. Since the support portion 24 is formed of the SiN film, the first wire 12 and the second wire 20 are connected in an insulated state. For this reason, the second wiring is supported by the support portion 24 at a predetermined distance from the first wiring 12, and the bending of the second wiring is suppressed, so that the mechanical strength of the entire cross wiring structure can be improved. .

Further, since the other end enters the inside of the second wiring from the lower surface side of the second wiring 20, the connection strength with the second wiring is high, and the mechanical strength of the entire cross wiring structure is further improved. It will be.

Therefore, the line width of the first wiring can be designed without being affected by the limit of the mechanical strength of the second wiring 20, so that the line width of the first wiring 12 is increased and the wiring resistance becomes a target value. Can be reduced. Of course, according to this method, it is possible to accurately form the support portion 24 at an arbitrary position, and there is an advantage that the degree of freedom in pattern design is increased.

In all the embodiments described above, the case where two wirings of the first wiring and the second wiring 20 intersect is shown for simplicity of explanation, but the present invention is not limited to the case where two or more wirings intersect. The present invention can be applied to a case where wirings cross each other.

In all the embodiments described above,
Although the wiring is provided on the semiconductor substrate, the wiring structure of the present invention is applicable not only to the semiconductor substrate but also to any substrate such as a printed wiring board on which wiring can be provided on the surface.

[0067]

As described above, according to the first aspect of the present invention, the insulating property for preventing the contact between the first wiring and the second wiring in the air intervening region between the first wiring and the second wiring. Since the first wiring and the second wiring are not in contact with each other due to the bending of the second wiring, a problem such as a short circuit between the wirings does not occur, and the wiring width of the first wiring is wider than before. As a result, the effect that the wiring resistance at the intersection position can be reduced is achieved. Of course, the effect of increasing the strength of the entire intersection structure between the first wiring and the second wiring is also achieved.

According to the second aspect of the present invention, in the wiring structure of the first aspect, since the insulating support is a structure for connecting the first wiring and the second wiring, the strength at the intersection of the second wiring is provided. And the bending of the second wiring is considerably suppressed, and the second wiring has an effect of being strong against a load applied from the side surface direction of the second wiring. Therefore, the effect of obtaining a wiring structure in which a short circuit does not occur due to contact between the first wiring and the second wiring compared to the related art is achieved.

According to a third aspect of the present invention, in the wiring structure of the first aspect, the support member is connected to the upper surface of the first wiring and separated from the lower surface of the second wiring, or is connected to the lower surface of the second wiring and connected to the lower surface of the second wiring. Since the first wiring and the second wiring are separated from each other, the effect of reducing the parasitic capacitance between the first wiring and the second wiring can be achieved as compared with the case where the first wiring and the second wiring are connected. Therefore, when applied to the wiring structure of the MMIC, the effect that the high frequency characteristics are not impaired is achieved. Of course, since the support member is configured to support the second wiring from the lower surface side when the second wiring is bent, a short circuit due to contact between the first wiring and the second wiring does not occur as compared with the related art.
The effect is also achieved. The invention of claim 4 achieves an effect that a support member having a desired shape can be easily formed at a target position. Further, an effect that a support member can be formed between the first and second wirings without significantly changing the device configuration is also achieved.

Further, the invention of claim 5 achieves the effect that the support member can be formed accurately at any place.
Of course, even when the support member is formed at a plurality of positions, the support member can be formed easily and accurately at the designed position, so that the effect of increasing the degree of freedom in pattern design is achieved.

[Brief description of the drawings]

FIG. 1 is a flowchart schematically showing a process of forming a wiring structure according to a first embodiment.

FIG. 2 is a perspective view schematically showing a wiring structure obtained by the manufacturing method shown in FIG.

FIG. 3 is a flowchart schematically showing a process of forming a wiring structure according to a second embodiment.

FIG. 4 is a flowchart schematically showing a process of forming a wiring structure according to a third embodiment.

FIG. 5 is a flowchart schematically showing a step of forming a wiring structure according to a fourth embodiment.

FIG. 6 is a schematic explanatory view showing a conventional wiring structure.

[Explanation of symbols]

 Reference Signs List 10 semiconductor substrate 12 first wiring 14 polyimide film 14a rectangular polyimide film 15 SiN film 16 positive resist 18 current film 20 second wiring 22 mask 24 support portion 26 space

Claims (5)

[Claims] 1. A wiring structure at an intersection of at least two wirings of a first wiring and a second wiring provided along the same plane, wherein the second wiring is located between the first wiring and the first wiring. It is arranged at a predetermined distance from the first wiring with air interposed therebetween, and in an air intervening region between the first wiring and the second wiring,
A wiring structure, comprising: an insulating support member that supports the first wiring and the second wiring so as to prevent the first wiring from coming into contact with the second wiring. 2. The wiring structure according to claim 1, wherein the supporting member has one end connected to the first wiring and the other end connected to the second wiring. 3. The support member has one end connected to one of the first wiring and the second wiring.
The other end is provided apart from the other of the first wiring or the second wiring, and when the second wiring is bent, the other end contacts the other wiring to form the second wiring. The wiring structure according to claim 1, wherein the wiring structure is supported. 4. An insulating film is formed on a substrate having a first wiring formed in close contact with a surface thereof until the first wiring is buried, and the insulating film is left except for a region where the second wiring intersects. Forming a dummy pattern made of an insulating material, forming a metal film on the surface of the substrate on which the dummy pattern has been formed, and patterning the metal film to form a second wiring passing over the dummy pattern. Forming a mask on a part of the dummy pattern on the side surface of the second wiring, and etching the dummy pattern in a direction parallel to the substrate surface from the side surface on which the mask is formed, thereby forming the first wiring A supporting member forming step of forming an insulating supporting member for supporting the first wiring and the second wiring so as to prevent contact between the second wiring and the second wiring. A method for forming a characteristic wiring structure. 5. An insulating film is formed on a substrate having a first wiring formed in close contact with a surface thereof until the first wiring is buried, leaving a part of a region expected to intersect with the second wiring. A supporting member forming step of forming an insulating supporting member on the first wiring by removing the insulating film; and forming a resist film on the substrate on which the supporting member is formed, and then forming a resist film on the first wiring. A dummy pattern forming step of forming a dummy pattern made of a resist having a support member inserted therein by removing the resist film while leaving a region expected to intersect with the second wiring, and forming a metal film on a substrate surface on which the dummy pattern is formed. After the formation, a second wiring forming step of patterning the metal film to form a second wiring passing over the support member; and removing a dummy pattern between the first wiring and the second wiring by etching. And a dummy pattern removing step.