JPH07135251A - Air bridge wiring for high-frequency circuit device - Google Patents

Abstract

PURPOSE:To provide air bridge wiring for high-frequency circuit devices which can prevent sacrifice later removing time from becoming longer and the occurrence of the residue of a sacrifice layer and, at the same time, can reduce the parasitic capacitance between wires intersecting each other. CONSTITUTION:Upper-layer wiring 15 formed across lower-layer wiring 11 with an air gap in between has a pair of leg sections 15b rising from the fixing sections 15a of the wiring 15 extended on a substrate 12 and the leg sections 15b support in the air the overbridge section 15c of the wiring 15 having a narrower width than the fixing sections 15a have. When the upper-layer wiring 15 is constituted in such a way, a sacrifice layer immediately below the wiring 15 can be easily removed and the parasitic capacitance between the overbridge section 15c and lower-layer wiring 11 can be kept at a small value, because the overbridge section 15c has a narrow width even when the width of the wiring is large as a whole.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to air bridge wiring for high frequency circuit devices such as high frequency transistors and high frequency ICs.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication (Kokai) No. 63-250155 proposes an aerial wiring (air bridge wiring) structure in order to reduce the parasitic capacitance of the wiring of a high frequency circuit.

[0003]

In order to form this air bridge wiring, it is necessary to remove the sacrificial layer under the upper wiring, but as the wiring width increases, the volume of the sacrificial layer to be removed increases. There is a problem that the sacrifice layer removal time is extended and the sacrifice layer residue is generated. Further, if the wiring width is increased, the parasitic capacitance between the crossing wirings is increased even if the sacrificial layer is removed, so that the crosstalk between the crossing wirings also deteriorates the SN ratio.

Further, even if the above air bridge wiring is used, the parasitic capacitance increases as the frequency increases. Therefore, the high frequency characteristics are deteriorated. The present invention has been made in view of the above problems, and it is possible to prevent the extension of the sacrifice layer removal time and the generation of a sacrifice layer residue, and to reduce the parasitic capacitance between the cross wirings. Its purpose is to provide.

[0005]

The air bridge wiring of the high-frequency circuit device of the present invention has a lower layer wiring extended on a substrate and an upper layer wiring intersecting the lower layer wiring with a gap. The upper layer wiring is an air of an integrated circuit including a laying portion extended on the substrate, a pair of leg portions rising from the laying portion in a direction approaching each other, and a bridging portion having both ends supported by the both leg portions. In the bridge wiring, the width of the bridging portion is formed to be narrower than the width of other portions of the upper layer wiring.

The width of the bridging portion may be narrowed by providing an opening in the central portion of the bridging portion. In a preferred aspect, the width of the straddle portion is formed to be narrower than the width of the leg portion. In a preferred aspect, the lower portion of the leg portion is formed wider than the upper portion of the leg portion.

[0007]

The upper layer wiring straddling the lower layer wiring has a pair of leg portions rising from a laying portion extended on the substrate, and the pair of leg portions has a narrower straddle portion than the other portions. Support in the air. In this way, even if the overall width of the upper layer wiring is large, the width of the straddling portion is narrow, so that the sacrificial layer immediately below can be easily removed, and moreover, the sacrificial layer immediately below the wiring portion and the lower layer wiring can be easily removed. The parasitic capacitance is also small. Of course, the electric resistance of the straddle portion increases as the width is narrow, but the straddle portion only needs to have a length enough to straddle the lower layer wiring, and the increase in resistance of the entire upper layer wiring can be almost ignored.

In a preferred mode, the width of the straddle portion is formed to be narrower than the width of the leg portion. With this configuration, the legs support the crossover part which is relatively small and lightweight as compared with its own strength, and the strength against vibration and the like is improved. In a preferred mode, the lower part of the leg is formed wider than the upper part of the leg. With this configuration, it is possible to prevent the sacrifice layer adjacent to the leg portion from being easily removed and to reduce the parasitic capacitance between the leg portion and the lower layer wiring while suppressing the strength reduction of the leg portion.

[0009]

【Example】

(Embodiment 1) An example of the air bridge wiring of the high-frequency circuit device of the present invention will be described based on (not shown) 1. Figure 1
1A is a schematic plan view of a main part of the air bridge wiring, and FIG. 1B is a schematic cross-sectional view taken along the line C-C of the air bridge structure of FIG. 1A.

The lower layer wiring 11 (hereinafter referred to as wiring 1) is formed on the substrate 12.
1) and upper layer wiring 15 (hereinafter also referred to as wiring 15)
Is formed, and at the intersection of the wiring 11 and the wiring 15,
The wiring 15 has a so-called air bridge wiring structure that straddles the wiring 11 in the air. That is, the wiring 15 is the substrate 1
Wide laying part 15a extended above 2 and laying part 15a
And a pair of leg portions 15b standing up in a substantially diagonal direction approaching each other and a narrow straddle portion 15c supported by both leg portions. Also. The width of the leg portion 15b is gradually narrowed from the lower portion to the upper portion.

In this embodiment, the lower end width of the leg 15b is 3
0 μm, the upper end width is 10 μm, and the width of the straddle portion 15c is 10 μm in the central portion. Further, both ends of the bridging portion 15c are gradually widened so as to be aligned with the upper ends of the leg portions 15b. In this way, the width of the overpass 15c in the air bridge structure is narrower than that of the leg 15b, so that it is easy to remove a sacrifice layer described later, and moreover, between the overpass 15c and the lower layer wiring 11. The parasitic capacitance of can also be reduced.

Further, the leg portion 15b supports the crossover portion 15c which is comparatively small and light in weight as compared with its own strength, so that the strength against vibration and the like is improved. Further, the width of the leg portion 15b is gradually narrowed from the lower portion to the upper portion, so that the leg portion 15b
It is possible to easily remove the sacrificial layer adjacent to the leg portion 15b and reduce the parasitic capacitance between the leg portion 15b and the lower layer wiring 11 while suppressing the decrease in strength of b.

Next, an example of the manufacturing process of this air bridge wiring will be described with reference to FIGS. 2 (a), 2 (b) and 2 (c).
In FIG. 2A, the substrate 2 on which the lower layer wiring 22 is arranged
A first-layer resist pattern 23 is formed on the first layer. This resist pattern covers the lower layer wiring 22 in the area A where the bridging portion is to be formed.

Next, as shown in FIG. 2B, a power supply electrode 24 for plating is formed by a method such as mask vapor deposition, and a resist pattern 25 of the second layer is further formed. Feeding electrode 2
Reference numeral 4 denotes a power supply electrode 24a provided on the surface of the straddle portion formation-scheduled region A and the surfaces of the leg portion formation-scheduled regions B on the left and right thereof,
It is composed of a power feeding electrode 24b for feeding power to the power feeding electrode portion 24a. The second-layer resist pattern 25 exposes the power feeding electrode portion 24a and covers the power feeding electrode 24b. Next, an electric current is passed through the power feeding electrode 24 to form the air bridge wiring 26 on the power feeding electrode 24a by electrolytic plating.

Next, the second layer resist pattern 25, the power supply electrode 24b, and the first layer resist pattern 23 are sequentially removed to obtain the air bridge wiring shown in FIG. 2 (c). First
The layer resist 23 and the second layer resist 25 are removed by oxygen ashing or cleaning with an organic solvent such as acetone or a resist remover. The power supply electrode 24 is removed by a method such as wet etching or argon sputtering.

Before forming the feeding electrode 24 for plating by a method such as mask vapor deposition, if the resist pattern 23 of the first layer is deformed into a mountain shape by thermal softening, as shown in FIG. Further, the power feeding electrode 24 can be raised obliquely. (Other Embodiments) Another embodiment of the air bridge structure according to the present invention will be described with reference to FIGS. 3 (a) and 3 (b). Figure 3
FIG. 3A is a schematic plan view of this air bridge wiring, and FIG. 3B is a schematic cross-sectional view taken along the line DD of FIG.

In FIGS. 3A and 3B, the lower layer wiring 31 and the upper layer wiring 35 are formed on the substrate 32, and the wiring 35 is formed in the air at the intersection of the wiring 31 and the wiring 35. It is so-called air bridge wiring to get over. An opening 33 is formed in the wiring 35 at a position directly above the wiring 31 in the bridging portion 35c of the wiring 35. The process of forming this opening is, for example, as shown in FIG.
An opening may be formed in the pattern of the power supply electrode 24 that is mask-deposited.

Although the shape of the opening 33 is a quadrangle, it may be a circle, a rhombus, an ellipse or the like. Also,
It is also possible to provide a plurality of openings. In this way, the width of the bridging portion 35c of the upper layer wiring 35 is determined by the laying portion 35 thereof.
Since the width is smaller than the width a and the opening 35c is provided in the center of the straddle portion 35c, the overlap (intersection) area between the upper layer wiring 35 and the lower layer wiring can be reduced and the parasitic capacitance can be reduced.

Further, by providing the opening 34, it is possible to easily remove the resist pattern 23 of the first layer immediately below the bridging portion 35c. That is, in FIG. 2B, when the resist 23 of the first layer is removed by a method such as cleaning the resist with a solvent, the resist 23 of the first layer can be removed from the opening provided in the air bridge wiring. It is possible to reduce the resist removal time and prevent the resist residue generated under the air bridge wiring.

[Brief description of drawings]

FIG. 1 (a) is a schematic plan view of a main portion of this air bridge wiring, and FIG. 1 (b) is a schematic cross-sectional view taken along the line C-C.

FIG. 2 shows an example of a manufacturing process of air bridge wiring.

FIG. 3 (a) shows a schematic plan view of this air bridge wiring, and FIG. 3 (b) shows a schematic sectional view taken along the line D-D.

[Explanation of symbols]

11 is a lower layer wiring, 12 is a substrate, 15 is an upper layer wiring, 15a
Is a laying portion, 15b is a leg portion, and 15c is a crossover portion.

Claims (3)

[Claims] 1. A lower layer wiring extending on a substrate, and an upper layer wiring intersecting the lower layer wiring with a gap therebetween, the upper layer wiring being a laying portion extended on the substrate, In an air bridge wiring of an integrated circuit consisting of a pair of legs rising in a direction approaching each other from a laid portion and a bridging portion whose both ends are supported by the both legs, the width of the bridging portion is equal to that of the upper layer wiring. Air bridge wiring for a high-frequency circuit device, which is formed to be narrower than the width of other portions. 2. The air bridge wiring of the high frequency circuit device according to claim 1, wherein a width of the bridging portion is formed narrower than a width of the leg portion. 3. The air bridge wiring of the high frequency circuit device according to claim 1, wherein a lower portion of the leg portion is formed wider than an upper portion of the leg portion.