JPH01202838A - Thin-film wiring - Google Patents

Abstract

PURPOSE:To lower contact resistance, to facilitate bonding and to improve oxidation resistance by coating the surface and side face of a first aluminum group wiring layer with a second wiring layer and a third aluminum group wiring layer. CONSTITUTION:The surface and side face of a first aluminum group wiring layer 3 are coated with a second wiring layer 4 and a third aluminum group wiring layer 5. Consequently, wirings are formed by the wiring films 3-5 of three layers, thus simultaneously satisfying a plurality of requirements as a whole by providing each layer 3-5 with different characteristics. Wirings at a level capable of permitting both characteristics can be shaped by combining a film having large crystal grain size and high electromigration resistance and a film having small grain size and high stress migration resistance. Since the upper and lower layers 3, 5 are formed by aluminum group films, wiring resistance is lowered. Accordingly, contact resistance is reduced, oxidation resistance is improved and bonding is facilitated.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to thin film wiring used in integrated circuits and the like.

[Conventional technology]

Thin film wiring using aluminum or the like is used as wiring for electronic elements such as integrated circuits (for example, ``LSI Handbook'', edited by the Institute of Electronics and Communication Engineers, published by Ohmsha in 1981, pp. 27S-281).

In fine aluminum-based interconnects, improving electromigration and stress migration resistance is a particularly important issue (for example, in the aforementioned book 'LSI Handbook' pp. 291-292 and Journal of Vacuum 5cie by Hinode et al.
nce & Tec-hnology B Magazine Volume 5, 2
issue, pages 501-522).

In order to solve this problem, a structure in which the aluminum-based wiring layer 9 is covered with a tungsten film 10 deposited by selective vapor deposition is being considered as shown in FIG.
86 International Electron
Devices Meeting Technic
al Digest (published by IEEE in 1986) 50~
Paper by H. P. W. Hey et al. on page 53).

[Problem to be solved by the invention]

However, although this structure certainly reduces the failure rate due to electromigration and stress migration, when applied to multilayer wiring, the contact resistance between wiring layers is high, and tungsten is difficult to bond with gold wire or aluminum wire. Furthermore, tungsten has the problem of being easily oxidized and becoming a lower oxide, which is easily evaporated.

An object of the present invention is to provide a novel thin film wiring that solves the problems of conventional thin film wiring.

[Means to solve the problem]

In order to achieve the above object, according to the thin film wiring of the present invention,
The second layer covers the surface and side surfaces of the first aluminum-based wiring layer.
The wiring layer is characterized by having a third aluminum-based wiring layer that further covers the surface and side surfaces of the second wiring layer.

[Effect]

Since the wiring according to the present invention is formed of three layers of wiring films, it is possible to simultaneously satisfy a plurality of requirements as a whole by providing each layer with different characteristics.

For example, by combining a film with a large crystal grain size and high electromigration resistance and a film with a small grain size and high stress migration resistance, it is possible to realize wiring at a level that allows both characteristics. In addition, since the upper and lower layers are made of aluminum-based films, not only the wiring resistance is low, but also low contact resistance can be obtained when applied to multilayer wiring, and it is resistant to oxidizing atmospheres. It is also easy to bond with aluminum wire. Furthermore, in the structure of the present invention, since the surface and side surfaces of the first aluminum-based wiring layer are covered with the second wiring layer and the third aluminum-based wiring layer, the crystals of the first aluminum-based wiring layer are The grain boundaries do not come into contact with the cover film, and the stress from the cover film is relaxed, so stress migration is less likely to occur even if the first aluminum-based wiring layer has a bamboo structure, and the second wiring layer and A selective vapor deposition method can be used to form the third aluminum-based wiring layer. That is, since it is necessary to process only the first wiring layer by the usual photoetching method, the thickness of the aluminum-based thin film to be photoetched becomes thinner, which is advantageous in forming fine wiring. For example, by forming a selectively deposited tungsten film as the second wiring layer and then selectively vapor-depositing a copper-containing aluminum thin film with high electromigration resistance as the third aluminum-based wiring layer, conventional problems could be solved. The problem that reactive ion etching of copper-containing aluminum thin films is difficult can be avoided. Furthermore, by using a non-aluminum-based thin film such as a refractory metal or refractory metal silicide as the second wiring layer, even if voids are formed at the same position in the first and third aluminum wiring layers due to electromigration or stress migration, Even if a disconnection occurs, the non-aluminum-based second wiring layer serves as a redundant wiring, which not only reduces the probability of malfunction of the integrated circuit element, but also reduces the probability that the integrated circuit device will malfunction. Since it is possible to prevent mutual diffusion and epitaxial growth of both the third aluminum-based wiring layers, the first and second wiring layers with different structures and structures can be prevented. Formation of the third aluminum-based wiring layer becomes easier.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

In FIG. 1(a), a silicon oxide film 2 is deposited on a silicon substrate 1 according to a standard integrated circuit manufacturing process. Next, 0.5 tm thick silicon and 1% copper were each deposited on the silicon oxide film 2 by standard sputtering.
After depositing the aluminum film 3 containing aluminum, the first aluminum-based wiring layer 3 is removed using standard photoetching techniques.
form. Next, the above structure is heat-treated in a mixed gas of hydrogen and nitrogen at 450° C. to stabilize the first aluminum-based wiring layer and grow the crystal grain size. As a result, in wirings with a line width of about 2p or less, a so-called bamboo structure wiring layer in which the grain boundaries exist almost in the wiring width direction is formed, as shown in FIG. 1(b). A tungsten layer 4 having a thickness of α2p is deposited as a second wiring layer covering the first aluminum-based wiring layer 3 by selective vapor deposition (selective CVO) using tungsten fluoride and hydrogen as reaction gases. . Next, as shown in FIG. 1(c), by selective CVD using triisobutylaluminum as a reaction gas, a third aluminum wiring layer 5 is formed covering the tungsten layer 4, which is the second wiring layer. Deposited to a thickness of .

Next, a standard cover film made of phosphorus glass, silicon nitride, etc. is deposited by a standard method (not shown) to complete a thin film interconnect that has sufficient resistance to electromigration and stress migration. .

In the above embodiment, a tungsten film was used as the second wiring layer, but it is also possible to use a conductive material such as silicide that allows selective CvD.

〔Effect of the invention〕

As explained above, according to the structure of the present invention, it is possible to realize a fine thin film wiring having sufficient resistance to electromigration and stress migration.

[Brief explanation of the drawing]

FIGS. 1(a) to (c) are schematic cross-sectional views of a sample in the main steps of forming a wiring structure according to an embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view of a sample in a conventional wiring structure.

Claims (1)

[Claims] 1. It has a second wiring layer that covers the surface and side surfaces of the first aluminum wiring layer, and a third aluminum wiring layer that further covers the surface and side surfaces of the second wiring layer. Thin film wiring.