JPS61190959A - Forming method for multilayer interconnection - Google Patents

Abstract

PURPOSE:To reduce contact resistance between a first layer wiring and a second layer wiring in a fined through-hole section, and to improve the degree of integration of multilayer interconnection structure by boring a through-hole to an inter-layer insulating film and forming the second layer wiring under the state in which the inner side surface of the through-hole is coated with an inorganic insulating film. CONSTITUTION:A through-hole 6 is bored to one part of a polyimide film to expose one part of a first layer Al wiring 3. The diameter of the through-hole 6 is brought to size such as 2mum at that time. A plasma CVD oxide film 7 is formed onto the whole surface containing the through-hole in thin size (approximately 0.4mum). The surface of the polyimide film and the plasma CVD oxide film on the base of the through-hole are dry-etched through RIE. Only a CVD oxide film 7a in the inner surface section of the through-hole is left at that time. Al is evaporated, and patterned, thus shaping a second layer Al wiring 5 connected to the first layer Al wiring 3 through the through-hole onto the polyimide film, then completing double layer interconnection structure.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a technology for miniaturizing multilayer wiring, and mainly relates to a method for forming multilayer wiring in semiconductor devices. [Background Art] In semiconductor devices such as ICs and LSIs, elements per chip are As the number of devices increases, it is no longer possible to use a single layer structure for interconnects made of aluminum or the like to connect between electrodes of elements, and a multilayer interconnect structure of two or more layers is being adopted. Conventionally, an inorganic insulating film such as silicon oxide thread glass containing silicon oxide or phosphorous oxide has been used as an interlayer insulating layer between two or more layers of wiring, but it is possible to form a thick film with this. In case,
Cracks are likely to occur due to distortion during heat treatment, and
When insulating films made of different materials are stacked in multiple layers, the level difference on the surface becomes severe, causing problems such as disconnections in the wiring formed thereon.

Instead of such inorganic insulating films, single-organic insulating films, which can be processed at relatively low temperatures and can ensure surface flatness, have come to be used. In particular, a wiring structure in which a highly heat-resistant polyimide polymer resin developed by the present inventor is used as an interlayer insulator has been adopted (see Japanese Patent Publication No. 57-36759).

This polyimide resin, for example, aromatic diamine,
A polyimide resin made of a polymer obtained by reacting with an aromatic tetracarboxylic dianhydride is interlayered on a substrate.
When forming an ik film, a prepolymer solution of polyimide resin! After applying the solution to the surface of the substrate on which wiring is formed using a spinner, the solvent component is evaporated, and heat treatment is performed at 200 to 300° C. to polymerize and harden, thereby forming an a'v layer.

Figure 7 shows interlayer polyimide resin #111g1! FIG. 2 is a cross-sectional view showing an example of a two-layer aluminum wiring structure used in FIG.

1 is a silicon crystal substrate, 2 is a surface oxide film (SiQ).

III). 3 is a first layer AJ (aluminum) wiring having a thickness d1 of about 1 to 1.75 μm. 4 is an interlayer insulating film made of polyimide resin, thickness d2 = 2.2μ
It is about m. 5 is a second layer 1 wiring formed on the interlayer insulating film 4, and a through hole formed in a part thereof.
6 to the first layer Al wiring 3.

In such a two-layer wiring structure, as the through-holes in the first-layer insulating film 4 become finer and their diameter becomes 3 μm or less, the opening of the holes becomes difficult even if sputter cleaning is performed later. It has been found that the contact resistance with the two-layer interconnect 5 increases rapidly.

OBJECT OF THE INVENTION] The present invention has been made to overcome the above-mentioned problems.

Therefore, one object of the present invention is to reduce the contact resistance between upper and lower aluminum wires in a through hole of an interlayer insulating film using polyimide resin in a multilayer wiring structure.

Another object of the present invention is to realize higher integration of a semiconductor device having a multilayer wiring structure using polyimide resin as an interlayer insulating film.

[Summary of the invention]

A brief overview of typical inventions disclosed in this application is as follows.

That is, in order to connect the second layer 1 wiring and the second layer 1 wiring on the substrate through through holes made in the interlayer insulating film made of polyimide resin, the through holes were formed in the interlayer insulating film. After that, by forming a second layer wiring with at least the inner surface of the through hole covered with an inorganic insulating film, contact between the first layer wiring and the second layer wiring in the miniaturized through hole portion is established. It is possible to reduce resistance and achieve high integration of multilayer wiring structures.

〔Example〕

FIGS. 1 to 7 show an embodiment of the present invention, and are cross-sectional views of a process for forming two-layer Al wiring on a semiconductor substrate. Please explain each step in detail below.

(1) As shown in FIG. 1, a Si (silicon) I crystal substrate (wafer) IY is prepared, a semiconductor element (not shown) is formed on the whole surface of this substrate, and the surface oxide film 2 generated at that time is On top of this, evaporation (or sputtering) is performed to form a 17th @Alj wiring having a thickness of 1.75 μm (3 feet) (AI<aluminum).

(2) A polyimide resin is applied thereon, and an interlayer insulating film 4 having a thickness of 5KJIk and about 1.75 to 2.0 μm is formed to cover the first layer AI layer 3 as shown in FIG. This cover is 1g! In step 4, a prepolymer solution of a polyimide resin or a half-form compound solution (for example, a solution of N-methyl-2-pyrrolidone or N-N-dimethyl-acetamide) is applied to the surface of the substrate using a spinner, and then a solvent is applied. It is formed by evaporating the components and further heat-treating at 200 to 300°C to harden it.

(3) Next, pass through a photoresist mask to remove hydrazine.
Etching is performed using Hitlered ethylene amine to make a through hole 6 in a part of the polyimide film to expose a part of the first layer 1 wiring 3, as shown in FIG. At this time, the diameter of the through hole 6 is, for example, 2 μm.

(4) After this, using a plasma discharge device, SiQ is chemically generated in the gas phase, that is, the plasma CVDW film 7
As shown in FIG. 4, is formed to a thickness of about 0.4 μm over the entire surface including the through hole.

(5) Perform so-called RIE (IJ active ion etching), which performs etching only in the vertical direction while applying an electric field to the substrate, to remove the plasma CVD#R film on the surface of the polyimide film and the bottom of the through hole. Have dry sex.

At this time, only the CVD oxide film 7a on the inner surface of the through hole along the ion projection direction remains without being etched, as shown in FIG.

(By vapor-depositing 61Al (aluminum) and buttering, a second layer Al wiring 5 is formed on the polyimide film to be connected to the second layer Al wiring 3 through a through hole as shown in FIG. The layer wiring structure is completed.

〔effect〕

According to the present invention explained in the embodiments above, the following effects can be obtained.

The reason why the contact resistance between the first layer Al wiring and the 21st IAl wiring increases when the through holes in the interlayer insulating film made of polyimide resin are miniaturized is due to A! when forming the second layer wiring. During vapor deposition, degassing from the surface of the polyimide resin inside the through-hole causes AJ on the bottom of the through-hole.
The surface changes in quality and A! It is thought that a high resistivity hlKi film containing oxides is generated.

However, by covering the inner surface of the through hole with an inorganic plasma CVD 5iO film, the surface deterioration of the AI coating due to the detung gas from the polyimide resin is significantly prevented, and in this state, the first layer Al wiring is Due to this formation, the contact resistance between the first layer Al wiring and the second layer Al wiring is reduced.

However, the inner surface of the through hole was coated with inorganic plasma CV.
By covering with DSiOt@, the deterioration of the A1 surface due to degassing from the polyimide resin is significantly prevented, and by forming the second layer Al wiring in this state, it is able to match the first layer Al wiring. Contact resistance with the second layer Al wiring can be reduced.

FIG. 8 is a curve diagram showing the relationship between the resistance of the upper and lower AI wirings in the through-hole portion and the bottom surface (D) of the through-hole, which varies depending on the state of the interlayer insulating film.

In the same figure, a person uses S t 02 or 5iN in the interlayer insulating film.
When using an inorganic film such as (nitride), B
C shows an example where an organic film such as polyimide resin is used, and C shows an example where a polyimide resin is used and the inside surface of the through hole is covered with a 5iQ1 film. With polyimide resin, the through-hole resistance R obtained is limited to about 4 μm, but it is possible to make it as fine as about 2 μm by covering the inside surface of the through-hole with SiQ, a film, etc. It is.

As described above, according to the present invention, by increasing the limit of miniaturization of through-holes, it is possible to realize highly integrated polyimide-based resin multilayer wiring.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the above Examples and can be modified in various ways without departing from the gist thereof. For example, a similar effect can be obtained when plasma Si3N is used as the inorganic film covering the inner surface of the through hole.

[Application field]

Is the present invention applicable to two-layer wiring or three or more layer wiring'? :Has 1
The present invention can be applied to any semiconductor device having a multilayer wiring structure in which an organic film such as a polyimide resin is used as a single-layer insulation film.

The present invention particularly applies to semiconductor integrated circuit devices such as linear ICs.
It is most effective to use

[Brief explanation of the drawing]

FIGS. 1 to 6 are process cross-sectional views of a two-layer wiring process showing an embodiment of the present invention. FIG. 7 is a sectional view showing an example of a conventional two-layer wiring structure. FIG. 8 is a relationship curve diagram between through-hole resistance and through-hole diameter. 1...Si substrate, 2...SiQ, film, 3...first
Layer Al wiring, 4... Polyimide interlayer, 5... Second
k1 layer wiring, 6... through hole, 7... inorganic coating. Figure 1 ♀ Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] 1. When connecting the first layer wiring and the second layer wiring formed on the substrate through the through hole formed in the organic insulating film between the layers, the organic insulating film between the layers is connected. A method for forming a multilayer wiring, which comprises forming a second layer wiring with at least the inner surface of the through hole covered with an inorganic insulating film after forming the hole. 2. The method for forming a multilayer wiring according to claim 1, wherein a polyimide resin is used as the organic insulating film. 3. The method of forming a multilayer wiring according to claim 1, wherein a polyimide resin is used for the organic insulating film, and silicon oxide thread glass is used for the inorganic insulating film.