JP2772050B2 - Multilayer wiring structure and method of manufacturing the same - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer wiring structure used for various solid-state devices including a semiconductor integrated circuit and a method for manufacturing the same.

[Conventional technology]

The following two structures have been proposed as a conventional multilayer wiring structure using interlayer connection metal columns. As shown in FIG. 2, the first structure has a structure in which the interlayer connection metal pillar 7 and the lower wiring layer 3 are made of the same metal and have an integrated structure (refer to "ERSirkin and IABlech:" A Method of Formi
ng Contacts Between Two Conducting Layers Separate
d by aDielectric ", J.Electrochem.Soc: SOLIDSTATESCIE
NCE AND TECHNOROGY, Vol. 131, No. 1, 1984. "). As shown in FIG. 3, the second structure has an interlayer connecting metal column 7 formed through a via hole formed in the insulating film 4 for stopper (refer to “Kiyoshi Irino et al .:“ Al pillar method). Multilayer Wiring ", 49th Fall Meeting, 17p-Q-16,198
7.)). In the first structure, after the lower wiring layer 3 including the interlayer connecting metal pillars 7 is deposited, first, only the interlayer connecting metal pillars 7 are processed selectively and leaving the thickness to be the lower wiring layer 3. This is realized by selectively processing a region to be the lower wiring layer 3. In this structure, since the lower wiring layer 3 and the interlayer connection metal pillar 7 have an integral structure, there is no problem of the interface between them, and there is a feature that the contact characteristics are not affected. In the second structure, after the lower wiring layer 3 is formed, the stopper insulating film 4 is formed, a via hole is opened in a portion where interlayer connection is to be performed, and a metal film for interlayer connection is formed. By doing, the interlayer connection metal pillar 7
Can be realized. This feature is high due to the provision of the stopper insulating film 4 (aspect ratio H / W
(Large) can be formed between the interlayer connection columns. 2 and 3, 1 is a substrate, 2 is an insulating layer, 3 'is a conductor wiring layer, and 8 is an interlayer insulating film.

[Problems to be solved by the invention]

However, these conventional multilayer wiring structures cannot be adapted to fine and high-density LSIs.

That is, as the wiring pitch is reduced due to the increase in the density of the LSI, the pattern dimensions of the wiring layer and the connection pillar must be reduced to submicron or less, making it difficult to provide an alignment margin in design. In any of the above methods, since alignment is required in the lithography process in any case, a pattern rule must be designed in consideration of an alignment error. Therefore, there is a problem that the wiring pitch as a multilayer wiring cannot be reduced even if a fine connecting pillar can be formed independently.

The present invention has been made in view of the above circumstances, and a multilayer wiring structure capable of realizing fine and high-aspect interlayer connection pillars without increasing the wiring pitch, and realizing fine and high-density multilayer wiring and It is an object of the present invention to provide a manufacturing method thereof.

[Means for solving the problem]

In order to achieve the above object, a multilayer wiring structure of the present invention is a metal multilayer wiring structure having an Al alloy wiring layer and an Al alloy interlayer connection pillar, wherein a lower Al alloy wiring in contact with the Al alloy interlayer connection pillar is provided. Characterized in that the surface of the layer is composed of an Al alloy layer / Ti nitride layer, and the method of manufacturing a multilayer wiring structure of the present invention comprises the steps of: forming an Al alloy layer / Ti nitride layer on a substrate; Forming a first conductive wiring layer of a laminated type composed of an Al / Al alloy layer, forming an insulating layer on the substrate excluding the first conductive wiring layer, and flattening the first conductive wiring layer; Forming an Al alloy interlayer connection pillar made of an Al alloy layer on a part of the conductor wiring layer.

[Action]

When processing Al alloy interlayer connection pillars, by performing RIE processing using silicon tetrachloride as the main component gas, it is possible to have sufficient selectivity with the underlying Ti nitride layer Therefore, etching can be stopped in a self-aligned manner. Therefore, it is possible to process a high Al alloy interlayer connection pillar, and a large alignment margin can be obtained, so that a fine and high aspect Al alloy interlayer connection pillar can be realized without increasing a wiring pitch, A fine and high-density multilayer wiring can be realized.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

1 (A) to 1 (E) are process sectional views showing an embodiment of the present invention.

FIG. 1 (A) shows a substrate such as a silicon substrate 11,
After the first conductor layer is deposited in a laminated manner and continuously through the first insulating layer 12, the first conductor layer is processed by a known lithography technique and a dry etching technique to form an Al alloy layer 1 of the conductor wiring layer.
3, a state in which a first laminated conductor wiring layer including a Ti nitride layer 14 as a metal nitride layer (etching stopper layer) and an Al alloy layer 16 as a protective conductor layer is formed. Here, Ti nitride layer 14
The layer functions as an etching stop layer at the time of pillar metal processing in a later step, and the uppermost Al alloy layer 16 functions as an altered protection film of the Ti nitride layer 14. Further, by using a reactive ion etching method using a chlorine-based material such as silicon tetrachloride for the dry etching, the first laminated conductor wiring layer can be continuously processed.

Insert extremely thin Ti layers above and below the Ti nitride layer 14.
It is also possible to adopt a Ti / TiN / Ti configuration, so that the contact can be further stabilized.

FIG. 1 (B) shows a state where a buried insulating layer 15 is formed on the first insulating layer 12 in a region other than the first stacked-type conductor wiring layer. The method of forming the buried insulating layer 15 is a known two-stage etch-back technique (see the document “Eiichi Yamamoto et al.
The method can be implemented by using the method of reducing wiring steps by step etch back ", 1988, 1986. In this etch-back technique, after forming a first laminated conductor wiring layer, a buried insulating layer substantially the same as the first laminated conductor wiring layer is formed, and subsequently, an organic film is applied to smooth the surface. Is performed, a reactive ion etching method using an oxygen-based gas is used as an etch back in the first step, a part of the organic film remains, and the buried insulation on the first stacked conductive wiring layer is left. After etching back under the condition that the organic film does not remain, the buried insulating layer on the first stacked conductive wiring layer is completely etched using the organic film as a mask by a reactive ion etching method using a fluorine-based gas as the etch back in the second step. Etching back to further remove the organic film, and further removing an unnecessary organic film, thereby embedding the insulating layer with self-alignment in a region other than the first stacked conductive wiring layer. Can. As shown in FIG. 1 (B), by providing an Al alloy layer 16 on the uppermost layer of the first stacked conductor wiring layer, Ti nitride can be prevented from reacting with fluorine-based reactive ion in the above-mentioned etch back. layer
14 can be reliably protected. FIG. 1 (C) shows a state in which, for example, after depositing an Al alloy layer as a pillar metal, an Al alloy pillar 17 for an interlayer connection conductor pillar is formed by a known lithography technique and a dry etching technique. Here, for dry etching, a reactive ion etching method using silicon tetrachloride gas is used, and the power density is 0.2 W / cm.
^By processing under condition ² , the selection between Al alloy and Ti nitride can be made as large as 7 to 9 (Al alloy / Ti nitride). This is because the Ti nitride layer 14 is the Al alloy pillar 17
This is because it acts as a stopper while etching a thick Al alloy layer for etching. Therefore, the extremely thin Ti nitride layer 14 can function as an etching stop layer at the time of processing the Al alloy pillar 17, and satisfactory processing without etching residue can be performed by sufficient over-etching in consideration of etching non-uniformity. .

FIG. 1D shows a state in which an interlayer insulating film 18 is formed in all regions except the Al alloy pillar 17. This forming method includes the two-stage etch-back technique described with reference to FIG.
In the case of an inorganic insulating layer, the method can be realized by repeating the method twice.

Further, an organic insulating film, for example, polyimide is applied to the interlayer insulating film 18.
In the case of using the polyimide, after forming a polyimide, a photoresist having good flatness is formed on the laminate, and this is etched back until the upper portion of the pillar 17 is exposed by an oxygen-based reactive ion etching method. Can be realized.

FIG. 1E shows that a second conductive wiring layer 13 'is formed by depositing, for example, an Al layer as a conductive layer on an interlayer insulating film 18 including pillars 17 by a known lithography and dry etching method. It shows the state where it was done.

Although a two-layer wiring can be realized by the above-described steps, it goes without saying that a multilayer wiring of three or more layers can be realized by repeating this.

In this example, Al was used as the pillar material.
Similar results can be obtained by using Al-Cu, Al-Si, Al-Si-Cu, etc. as an Al-based alloy material. It is preferable to form an alloy and form a finen. In addition, the same configuration can be realized by using Cu or a Cu alloy for the wiring layer and the pillar in order to reduce the resistance.

In this example, TiN was used as the stopper material.However, if the resistivity is low to some extent and the compatibility with Al is good, and if the etching stopper effect is recognized, it is not possible to apply other metals or metal nitrides. Needless to say.

〔The invention's effect〕

As described above, the multilayer wiring structure and the method of manufacturing the same according to the present invention have a configuration in which a Ti nitride layer is provided on the uppermost layer of a lower Al alloy wiring layer which is a lower layer of a pillar metal for wiring interlayer connection. Thereby, the pillar metal can be formed in a self-aligned manner, and a fine, high-aspect pillar can be formed. Therefore, the wiring pitch can be reduced to the limit of the lithography,
Remarkable densification of the multilayer wiring is achieved. Further, since it is not necessary to form a fine via hole and bury a metal in the via hole, the reliability and yield in the wiring interlayer can be significantly improved.

[Brief description of the drawings]

1 (A) to 1 (E) are process sectional views showing one embodiment of the present invention, and FIGS. 2 and 3 are structural sectional views showing a conventional multilayer wiring structure. 11 ... substrate, 12 ... insulating layer, 13 ... Al alloy layer, 13 '...
Conductor wiring layer, 14 Ti nitride layer (etching stopper layer), 15 Buried insulating layer, 16 Al alloy layer, 17
Al alloy pillar, 18 …… Interlayer insulating film.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 21/3205 H01L 21/3213 H01L 21/768

Claims (2)

(57) [Claims] In a metal multilayer wiring structure having an Al alloy wiring layer and an Al alloy interlayer connection pillar, a surface of a lower Al alloy wiring layer in contact with the Al alloy interlayer connection pillar is formed of an Al alloy layer / Ti nitride. A multilayer wiring structure comprising a plurality of layers. 2. A step of forming, on a substrate, a laminated first conductor wiring layer composed of an Al alloy layer / Ti nitride layer / Al alloy layer;
Forming an insulating layer on the substrate except for the first conductor wiring layer and flattening the same; and forming an Al alloy interlayer connection pillar made of an Al alloy layer on a part of the first conductor wiring layer. And a method for manufacturing a multilayer wiring structure.