JPH1187618A - Inductor for semiconductor device and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inductor having advantage of meander type, without particularly having lowered Q for the large number of turns in a coil, while having a high integration efficiency. SOLUTION: An inductor for semiconductor device comprising a thin film wiring formed on insulation films 4 and 5 on the semiconductor substrate is formed, so that the insulation films 4 and 5 are correspondingly formed by plural projecting sections 8 and recess sections 9 alternately parallel to each other as in the teeth of a comb, the difference in height between the sections 8 and the sections 9 is made thicker than at least the thickness of the wiring, and a bevel step 7 is constituted forwardly tapered. A meander coil is formed by the wiring along the section 8 and the section 9 with the wiring being folded back at the bevel step 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inductor provided as one of passive elements inside a high frequency IC.

[0002]

2. Description of the Related Art Conventionally, spiral type inductors and meander type inductors have been widely used as inductors built in high frequency ICs.

FIG. 2A is a plan view of a spiral inductor, FIG. 2B is a sectional view thereof, FIG. 3A is a plan view of a meander inductor, and FIG. 2B is a sectional view thereof. .

A spiral type inductor is usually formed in a two-layer structure as shown in FIG. A lead wiring 2 is formed on an insulating film 5 provided on a semiconductor substrate 6, and a second-layer insulating film 4 is provided over the lead wiring 2, and a spiral coil made of a metal thin-film wiring is formed thereon. The center end of the coil is a via hole (vi) formed in the insulating film 4.
(ahole) 3 and connected to the extraction wiring 2.

On the other hand, the meander-type inductor has a single-layer structure, as shown in FIG. 3, and has a coiled portion formed by winding wires 1 formed on an insulating film 5.

[0006]

In the conventional inductors as shown in FIGS. 2 and 3, when the number of turns is increased, the occupied area and the length of the wiring (therefore, the resistance) are greatly increased. In addition, there is a problem that it is difficult to produce an inductor having good area efficiency and good Q characteristics.

In the spiral inductor shown in FIG. 2, if the pitch of the coil is s, the length of the minimum coil side is L 1, and the number of turns is n, the wiring length A 1 and the occupied area of the coil portion S1 is as follows. A1 = 4nL1 + 2 (2n-1) ns S1 = {L1 + 2 (n-1) s} 2

As shown in the above equation, when the number of turns increases, both the wiring length and the occupied area increase in proportion to the square of the number of turns n, so that the above-mentioned problem becomes significant.

On the other hand, in the meander type inductor shown in FIG. 3, the length of the element side is L2, the pitch is s, and the number of turns is n.
Then, the wiring length A2 and the occupied area S2 are as follows: A2 = 2n · L2 + 2n · s S2 = 2n · L2 · s Both the wiring length and the occupied area increase in proportion to the number of turns n. Therefore, there is no problem in increasing the number of turns in the area efficiency and the Q characteristic described above.

However, in the meander-type inductor, the currents flowing through the adjacent conductors are in opposite directions.
Mutual inductance between adjacent conductors has a negative effect on self-inductance, and as the distance between conductors (interval between wires) is reduced, the inductance value is reduced. This is a constraint on increasing the density.

An object of the present invention is to provide an inductor for a semiconductor device which has solved the above problems.

[0012]

According to the present invention, there is provided an inductor for a semiconductor device provided on an insulating film on a semiconductor substrate and formed of thin-film wiring. A meandering coil formed by forming a stepped shape having a convex portion and a concave portion, and a wiring portion formed along the convex portion and the concave portion and a folded wiring portion formed at the step portion. .

As described above, the insulating film is formed so as to have a step, and the meander-type coil is formed by using the wirings along the convex and concave portions as main parts, thereby substantially reducing the distance between adjacent conductors. Since the problem of reduction in inductance value due to the narrowing of the conductor spacing described above is alleviated, it is possible to increase the mounting density while using a meander type coil.

In the semiconductor device inductor, a step of depositing a first insulating film over a predetermined area on a semiconductor substrate, depositing a second insulating film on the first insulating film, and selectively etching the second insulating film. Forming a plurality of convex portions such that the step portions thereof have a forward tapered shape, and depositing a wiring material on the upper surfaces of the first insulating film and the second insulating film, and etching or forming the wiring material. Can be manufactured by a series of steps including a step of forming a coil portion by direct depiction of the coil section.

[0015]

1A and 1B are explanatory views of an inductor for a semiconductor device according to the present invention, wherein FIG. 1A is a plan view thereof, and FIG.
Is a sectional view thereof. Hereinafter, the structure of the inductor of the present invention and the manufacturing procedure thereof will be described for one embodiment provided on a semiconductor substrate such as Si.

First, an insulating film 5 made of, for example, SiO2 is formed on a semiconductor substrate 6 by CVD or the like. This insulating film 5 is also used as a base insulating film for forming other elements.

Next, S is formed on the upper surface of the insulating film 5 by CVD or the like.
An insulating film 4 of iO2 or the like is deposited, and a plurality of convex portions 8 which are alternately parallel in a comb shape are formed by selective etching of the insulating film. By this step, a concave portion having the surface of the insulating film 5 is formed on the bottom surface. The step portion 7 needs to be formed to have a forward taper in order to ensure the wiring to be performed in the next step. The step portion 7 is formed by dry etching or the like. It is necessary to adjust the material and the composition of the etching solution.

Also, polyimide can be used as the insulating film 4. In this case, a film is formed by spin coating, and a convex portion is similarly formed by etching, but the step portion has a forward tapered shape due to the nature of the material.

Next, a metal thin film of Al, Au, or the like is deposited on the stepped insulating film by sputtering, vapor deposition, or the like, and is etched while leaving selected portions, thereby forming the parallel convex portions 8. A meander-type thin-film coil extending along the concave portion 9 and folding back at the step portion 7 is formed.
The above-mentioned thin film coil can be formed by a method in which a wiring material is directly drawn using a FIB apparatus or the like and applied.

With the above configuration, since the wiring structure becomes three-dimensional, it is possible to realize an inductor having a wiring space substantially wider than that of the conventional one for the same mounting density.

[0021]

As described above, the inductor for a semiconductor device according to the present invention has a shape in which an insulating film is stepped so as to have a plurality of convex portions and concave portions which are alternately parallel in a comb shape. The meander-type coil was formed by forming the wiring along the convex and concave portions and the folded wiring at the step, so that the wiring interval could be substantially increased, which is a weak point of the meander type. The problem of a reduction in the inductance value due to the narrowing of the wiring interval is alleviated.

Therefore, it is possible to realize a meander-type inductor having good mounting efficiency while having the advantage of the meander-type in which Q is not particularly reduced when the number of turns is large.

Further, the insulating film having the above-mentioned steps, which is a feature of the present invention, is a step of depositing a first insulating film over a predetermined area on a semiconductor substrate, and forming a second insulating film on the first insulating film. It can be easily formed by using a process of depositing and selectively etching the second insulating film.

Further, the inductor of the present invention does not require complicated two-layer wiring including wiring connection by via holes, etc.
It has the advantage that it can be manufactured with relatively simple single-layer wiring.

[Brief description of the drawings]

FIGS. 1A and 1B are explanatory views of one embodiment of an inductor for a semiconductor device according to the present invention, wherein FIG. 1A is a plan view and FIG.

FIGS. 2A and 2B are explanatory diagrams of a conventional inductor for a spiral type semiconductor device, wherein FIG. 2A is a plan view and FIG.

3A and 3B are explanatory diagrams of a conventional meander-type semiconductor device inductor, in which FIG. 3A is a plan view and FIG. 3B is a cross-sectional view thereof.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Coil part wiring 2 Lead-out wiring 3 Via hole 4, 5 Insulating film 6 Semiconductor substrate 7 Step part 8 Convex part 9 Concave part

Claims (2)

[Claims] 1. A semiconductor device inductor provided on an insulating film on a semiconductor substrate and comprising thin-film wiring, wherein said insulating film has a plurality of convex portions and concave portions which are alternately parallel in a comb shape. Formed in a shape with a step so as to have a portion, and a meander type coil is configured by a wiring portion formed along the convex portion and the concave portion and a folded wiring portion formed in the step portion. For semiconductor devices. 2. A method for manufacturing an inductor for a semiconductor device, which is provided on an insulating film on a semiconductor substrate and includes thin-film wirings, wherein a first area over a predetermined area on the semiconductor substrate is provided.
Depositing an insulating film, depositing a second insulating film on the first insulating film, and selectively etching the second insulating film so that a plurality of convex portions are formed so that the steps become forward tapered. Forming a coil portion by depositing a wiring material on an upper surface of the first insulating film and the second insulating film and etching or directly drawing the wiring material. Of manufacturing inductors for automobiles.