JPH06283864A - Forming method for multilayer interconnection structure - Google Patents

Abstract

PURPOSE:To provide a method for controlling a relative permittivity of an layer insulating film formed of resin in the case of forming a multilayer interconnection structure. CONSTITUTION:A film 35 in which naphthoquinone azide compound 33 is mixed in polyimide resin is formed on a board 31. This sample is heated at 250-400 deg.C, and the layer 35 of the resin is cured. Thus, the compound is decomposed by heat treating for curing the film 35 of the resin to generate nitrogen gas, and hence the film 35 of the resin is foamed. As a result, an layer insulating film 37 having an air gap 37a is obtained, and an adding amount of the compound 33 is controlled to control number of the gaps 37a, thereby controlling a relative permittivity of the film 37.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a multilayer wiring structure, and more particularly to a method for controlling the relative dielectric constant of an interlayer insulating film.

[0002]

2. Description of the Related Art For example, a printed circuit board on which various electronic parts such as a semiconductor integrated circuit (IC) are mounted,
In an IC mounted on such a printed circuit board,
A so-called multi-layer wiring structure is often used in which wirings are stacked in multiple layers via an interlayer insulating film, and these wirings are connected using a through hole provided in the interlayer insulating film. This is because by doing so, desired constituent components can be mounted or formed on the printed circuit board or the semiconductor substrate with high density, and the operating speed of the electronic device or IC can be improved.

In the field of utilizing such a multilayer wiring structure, in recent years, an interlayer insulating film has been made of a resin, particularly a heat resistant thermosetting resin. This is because advantages such as easier formation of the interlayer insulating film can be obtained as compared with the method of forming the interlayer insulating film using a vacuum device or the like.

In the case of forming a multi-layer wiring structure having an interlayer insulating film made of resin, conventionally, a method generally described below has been generally used. 4 and 5 are process diagrams used for the description. Each drawing shows a cross section of the sample in the main step of forming the multilayer wiring structure taken along a direction parallel to the thickness direction.

First, the base 11 on which a multilayer wiring structure is desired to be formed
As the resin for forming the interlayer insulating film, for example, a thermosetting resin film is formed thereon by a suitable method such as a spin coating method or a spraying method. Next, this sample is heat-treated at a predetermined temperature to obtain a first-layer interlayer insulating film 13 made of resin (FIG. 4A). Here, the base is various things such as a ceramic substrate, an alumina substrate, or a semiconductor substrate for which a multilayer wiring structure is desired to be formed. The resin for forming the interlayer insulating film is, for example, polyimide, BCB (benzocyclobutene), polyquinoline (manufactured by Maxdem), or pyrene (CNET).
Various resins such as CYTOP (manufactured by Asahi Glass), Teflon AF (manufactured by DuPont), PTEF, and PFA.

Next, a suitable thin film of chromium, copper, titanium, aluminum or the like is formed as the conductor layer 15 on the interlayer insulating film 13 by a suitable method (FIG. 4 (B)). In some cases, the surface of the interlayer insulating film 13 may be treated with plasma or chemicals before forming the conductor layer 15 in order to increase the adhesion between the interlayer insulating film 13 and the conductor layer 15.

Then, a resist pattern 17 having an opening 17a exposing only a predetermined portion of the conductor layer 15 is formed on the conductor layer 15 by a known lithography technique (FIG. 4C).

Next, a conductor film 19 for contact wiring, a so-called via post 19, is formed on the portion of the conductor layer 15 exposed from the resist opening 17a by electrolytic plating or electroless plating (FIG. 4D). .

Next, the resist pattern 17 is removed (FIG. 5A).

Next, a thermosetting resin film 21 for forming an interlayer insulating film is formed again on this sample (FIG. 5B).
Further, a predetermined heat is applied to this sample, so that the resin film 2
1 curing is performed.

Next, the cured resin film is removed until the surface of the via post 19 is exposed, and the second interlayer insulating film 21a is obtained (FIG. 5C). After that, the desired multilayer wiring structure is obtained by repeating the procedure described with reference to FIGS. 4B to 5C according to the required number of layers.

[0012]

However, in the above-described conventional method for forming a multilayer wiring structure, the interlayer insulating film is formed by simply forming a resin film and curing the film. Therefore, the relative permittivity of this interlayer insulating film is determined by the relative permittivity of the resin that constitutes this interlayer insulating film. Therefore, on the side of purchasing and simply using the resin, the relative permittivity of the interlayer insulating film is There is a problem that it is difficult to control. In printed wiring boards and ICs, it is often desired to change the relative permittivity of the interlayer insulating film for the purpose of improving the transmission characteristics and the like. A technology that can be controlled at the manufacturing stage is desired.

The present invention has been made in view of the above circumstances, and therefore an object of the present invention is to improve the relative dielectric constant of an interlayer insulating film when forming a multilayer wiring structure having an interlayer insulating film made of a resin. It is to provide a method that can be controlled at the manufacturing stage.

[0014]

In order to achieve this object, according to the present invention, in forming a multilayer wiring structure having an interlayer insulating film made of a resin, the formation of the interlayer insulating film is performed as follows. It is characterized in that the steps are carried out including the steps a) to (c).

(A) A step of mixing a foaming agent which is decomposed by the action of energy applied to the resin to cure the resin into the resin for forming the interlayer insulating film.

(B) A step of forming a resin film mixed with the foaming agent on a lower surface for forming an interlayer insulating film.

(C) A step of applying the above-mentioned energy to the underlayer on which the resin film is formed to cure the resin film and form voids due to the foaming agent in the cured film.

Here, the resin for forming the interlayer insulating film may be various resins suitable for the intended multilayer wiring structure and is not particularly limited. For example, the above-exemplified resins such as polyimide resin are suitable.

Further, the energy to be applied to the resin later to cure the resin is preferably heat, for example. However, other energy sources such as light may be used in some cases.

Further, the base for forming the interlayer insulating film can be various kinds of bases on which the interlayer insulating film is desired to be formed. For example, various substrates such as a glass epoxy substrate, a ceramics substrate, a glass substrate, or a semiconductor substrate, and those on which one layer or several layers of a multilayer wiring structure have been already formed, etc.

The above-mentioned foaming agent is not limited to this, but examples thereof include aromatic bisazides such as naphthoquinonediazide compounds.

[0022]

According to the structure of the present invention, an interlayer insulating film (porous interlayer insulating film) made of resin and having a large number of voids inside can be obtained. Since the dielectric constant of the void portion is different from the dielectric constant of the resin for forming the interlayer insulating film, the relative dielectric constant of the interlayer insulating film formed by the method of the present invention is different from that in the case where the interlayer insulating film is simply formed of resin. It becomes a value. For example, if the void is air, the relative dielectric constant of the interlayer insulating film can be controlled to be smaller than that in the case where the interlayer insulating film is made of only resin. Further, the relative permittivity of the interlayer insulating film can be changed by the size and density of the voids, and the density of the voids can be controlled by, for example, adjusting the amount of the foaming agent mixed with the resin for forming the interlayer insulating film. Therefore, the relative dielectric constant of the interlayer insulating film can be controlled.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the method for forming a multilayer wiring structure of the present invention will be described below with reference to FIGS. In addition,
These figures show a cross section of the sample in the main step of forming the multilayer wiring structure, taken along a direction parallel to the thickness direction. However, these figures merely show the dimensions, shapes, and positional relationships of the respective constituents to the extent that the present invention can be understood.

First, an underlayer on which a multilayer wiring structure is desired to be formed, such as a glass substrate or a ceramic substrate, is prepared and washed with an organic solvent or the like. On the other hand, in this case, the polyimide resin as the resin for forming the interlayer insulating film is decomposed by the action of energy (heat in this embodiment) applied to the resin later to cure the resin. An appropriate amount of naphthoquinonediazide compound in this case as a foaming agent is mixed therein.

Next, the above-mentioned polyimide resin mixed with a foaming agent is applied onto a substrate using a suitable device such as a spinner, a roll coater or a bar coater, and a resin film containing the foaming agent 33 is applied onto the substrate 31. 35 (FIG. 1
(A)).

Next, the sample is heated using a suitable heating device in order to cure the resin film 35. Although this heating is not limited to this, for example, a step called half cure (for example, a step at a temperature of 80 to 130 ° C.) and a step called Frucure that follows this step (for example, 200 to 450 ° C.). The temperature is set to the above step). It is known that a naphthoquinonediazide compound decomposes when heated to 140 ° C. or higher and emits nitrogen (N ₂ ) gas. And since the temperature for curing the polyimide resin includes the high temperature of 200 to 450 ° C. as described above,
The temperature of the naphthoquinonediazide compound is sufficiently higher than the temperature at which N ₂ gas is emitted. Therefore, in the step of curing the polyimide resin film 35, the naphthoquinonediazide compound in the film 35 emits N ₂ gas, which causes the polyimide resin film 35 to foam, resulting in the voids 37a.
The inter-layer insulating film 37 having the above is obtained (FIG. 1B). Here, the relative permittivity of the interlayer insulating film 37 can be changed by the density (number) of the voids 37a in the interlayer insulating film 37. The density (number) of the voids 37a can be adjusted by the amount of the naphthoquinonediazide compound added to the resin.

Next, for the purpose of flattening the surface of the interlayer insulating film 37, only the resin for forming the interlayer insulating film (also referred to as a planarizing resin for the sake of explanation) is formed on the interlayer insulating film 37 (this time also). Naphthoquinonediazide compound-free) is applied by a suitable method, and then this is heat-cured to flatten the flattening layer 3
9 is obtained (FIG. 1 (C)). The flattening layer 39, of course, constitutes a part of the interlayer insulating film. However, if the surface of the interlayer insulating film 37 has a flatness that causes no practical problem, the planarizing layer 39 is not necessarily provided. On the other hand, when flattening cannot be achieved by applying the flattening resin, it is preferable to carry out a polishing process or an etch-back process.

Next, a suitable thin film of chromium, copper, titanium, aluminum or the like is formed as a conductor layer (not shown) on the interlayer insulating film 37 (on which the flattening layer 39 is provided) by a vapor deposition method, It is formed by a suitable method such as a sputtering method. In some cases, the surface of the interlayer insulating film 37 may be treated with plasma or chemicals before forming the conductor layer in order to increase the adhesion between the interlayer insulating film 37 and the conductor layer.
Next, a resist pattern (not shown) having an opening exposing only a predetermined portion of the conductor layer is formed on the sample on which the conductor layer is formed. Next, a metal film is formed on the portion of the conductor layer exposed from the resist opening by electrolytic plating or electroless plating to obtain the lower wiring 41 (FIG. 1D). Next, a resist pattern 43 having an opening 43a exposing only a predetermined portion of the lower wiring 41 is formed on the sample on which the lower wiring 41 has been formed by a known lithography technique (FIG. 1D).

Next, a conductor film 45 for contact wiring, a so-called via post 45, is formed on the portion of the wiring forming thin film 41 exposed from the resist opening 43a by electrolytic plating or electroless plating (see FIG. 2A). )). next,
The resist pattern 43 is removed (FIG. 2 (B)).

Next, a resin film 35 for forming an interlayer insulating film containing a foaming agent 35 is again formed on this sample, for example, as shown in FIG.
It is formed by the method described with reference to FIG.
(C)).

Next, the resin film 35 is cured and foamed by the method described with reference to FIG. 2B to form the void 37a (FIG. 3A).

Next, if necessary, a planarizing layer (not shown) is formed by the method described with reference to FIG. 1C, and then the sample surface is etched until the surface of the via post 45 is exposed. To do. As a result, the interlayer insulating film 47 having the void 37a is obtained (FIG. 3B).

Next, a thin film (not shown) such as chromium, gold, or copper for forming the upper wiring is formed on the interlayer insulating film 47 by a suitable method, and the thin film is formed by a known method. The upper wiring 49 is obtained by patterning (FIG. 3C).

Then, depending on the required number of layers, the process shown in FIG.
By repeating the procedure described with reference to FIG. 3C, a desired multilayer wiring structure can be obtained.

Although the embodiments of the multilayer wiring structure of the present invention have been described above, the present invention is not limited to the above embodiments. For example, the procedure for forming the lower wiring and the upper wiring is merely an example. Moreover, the structure of the multilayer wiring is merely an example.

[0036]

As is apparent from the above description, according to the present invention, a porous interlayer insulating film made of resin and having a large number of voids inside can be formed during the formation of a multilayer wiring structure. . Therefore, it is possible to easily obtain an interlayer insulating film having a relative dielectric constant different from that of the case where the interlayer insulating film is made of only resin. Moreover, since the relative permittivity can be controlled by adjusting the mixing amount of the foaming agent in the resin for forming the interlayer insulating film, the relative permittivity of the interlayer insulating film can be controlled. Therefore, an interlayer insulating film having a desired relative permittivity can be easily obtained, so that improvement in transmission characteristics in electronic devices and ICs can be expected.

[Brief description of drawings]

FIG. 1 is a process drawing for explaining an example.

FIG. 2 is a process chart following FIG. 1 for explaining an example.

FIG. 3 is a process chart following FIG. 2 for explaining the embodiment.

FIG. 4 is a process diagram for explaining the conventional technique.

FIG. 5 is a process chart following FIG. 4 for explaining the conventional technique.

[Explanation of symbols]

 31: Substrate 33: Foaming Agent 35: Interlayer Insulating Film Forming Resin Film 37, 47: Interlayer Insulating Film Having Voids 37a: Voids 41: Lower Wiring 45: Beer Post 49: Upper Wiring

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H05K 1/03 E 7011-4E

Claims (2)

[Claims] 1. When forming a multilayer wiring structure having an interlayer insulating film made of resin, the interlayer insulating film is formed by steps including the following steps (a) to (c): Method for forming multi-layer wiring structure. (A) A step of mixing a foaming agent that is decomposed by the action of energy applied to the resin to cure the resin into the resin for forming the interlayer insulating film. (B) A step of forming a resin film mixed with the foaming agent on a lower surface for forming an interlayer insulating film. (C) A step of applying the energy to the underlayer on which the resin film is formed to cure the resin film and form voids due to the foaming agent in the cured film. 2. The method for forming a multilayer wiring structure according to claim 1, wherein the foaming agent is a naphthoquinonediazide compound.