Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material
Reexamination Certificate
1999-08-27
2001-12-04
Smith, Matthew (Department: 2825)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
C438S360000, C438S627000, C257S750000
Reexamination Certificate
active
06326287
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor device and a method of fabricating the same, and, more particularly, to a semiconductor device which can be miniaturized and has a wiring layer made of an aluminum alloy having high electro-migration resistance, and to a method of fabricating the same.
2. Description of Related Art
In semiconductor devices such as LSIs, recent advances in miniaturization, integration, and multi-layering of electronic elements have required through-holes with a large aspect ratio. It is difficult to embed wiring materials into such through-holes, and this has become an important technical problem in recent years. Therefore, attempts have been made to embed aluminum or an aluminum alloy which is useful as a wiring material into the through-holes.
Customary methods, however, require high temperature in sputtering to bury aluminum or an aluminum alloy in a through-hole. As the temperature increases, whiskers are easily produced, causing short circuits between wires, and aluminum of a wiring layer in the through-hole reacts with silicon in a substrate giving easy rise to electrical characteristic problems such as leaks. Recent advances in miniaturization and integration of electronic elements have required further flatness of deposited layers and also formation of a thinner film of wiring layers. However, if the wiring layer is thin, the electro-migration resistance is reduced and hence conventionally used aluminum alloy materials cannot adequately cope with this phenomenon.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a semiconductor device using, as a wiring material, a specific aluminum alloy which can be embedded in a through-hole without producing any void or wire breaking, and being highly resistant to electro-migration. It is a further object of the present invention to provide a method of fabricating such semiconductor device.
According to a first aspect of the present invention, there is provided a semiconductor device comprising a semiconductor substrate including an electronic element, at least one metal wiring layer, and at least one interlayer dielectric, wherein the metal wiring layer contains aluminum as a major component and 0.1-3 wt % of beryllium.
In the semiconductor device, an aluminum alloy containing a specific quantity of beryllium is used as a metal wiring material to thereby obtain a metal wiring layer which is highly resistant to electro-migration. Although the reason is not clear, it is considered that a beryllium alloy (for instance, a beryllium/copper alloy or an aluminum/beryllium/copper alloy) precipitates at the grain boundary of the aluminum, thereby inhibiting the electro-migration of aluminum.
Beryllium is also capable of occluding oxygen. For instance, beryllium occludes oxygen which is produced from silicon oxide of an interlayer dielectric and exists in an aluminum alloy to improve the fluidity of aluminum and the capability of embedding an aluminum alloy in a through-hole.
Moreover, trace titanium and magnesium improve the effect of occluding oxygen, which further improves the capability of embedding an aluminum alloy in a through-hole. At least one of magnesium and titanium may be contained in a proportion of 0.1 to 3 wt %.
A gasifiable component may be excluded from the interlayer dielectric by thermal processing. A contact section formed of an aluminum alloy having excellent step coverage can be formed by removing a gasifiable component produced in the interlayer dielectric. The reason will be described later.
In the semiconductor device, an oxide of a metal that is included in the barrier layer may be distributed in the barrier layer in an island-like configuration. This structure increases the barrier capability of the barrier layer as compared with the case where the barrier layer does not include a metal oxide.
The reason is considered to be as follows. For instance, a barrier layer containing titanium has been considered to be in an amorphous state. However, it has been clarified from the studies of the inventors of the present invention that, in the barrier layer of the present invention, crystal grains of titanium oxide (TiO
2
) are dispersed in an island-like configuration at random in a titanium nitride layer which has a disordered crystal structure. Titanium oxide is an almost perfect insulating material and is a material in which a metal such as aluminum is diffused with extreme difficulty. The presence of such titanium oxide grains formed in an island-like configuration in the barrier layer disarranges the crystal structure of titanium nitride to inhibit the intrusion of aluminum which diffuses beyond the grain boundary (boundary between crystal grains). As a consequence, the barrier capability of the barrier layer is outstandingly improved. This phenomenon also occurs when the barrier layer contains a metal such as cobalt or tungsten.
An oxide of a metal that is included in the barrier layer exists in a manner that it is dispersed island-like in the barrier layer and hence does not inhibit the electroconductivity of the barrier layer. In other words, the grains of the metal oxide contained in the barrier layer are preferably dispersed in such a condition that the electroconductivity of the barrier layer is not inhibited.
Preferably the average particle diameter of the grains of the oxide of a metal that is included in the barrier layer may be in a range between 2 and 20 nm taking the barrier capability and the electroconductivity into consideration.
According to a second aspect of the present invention, there is provided a method of fabricating a semiconductor device comprising the steps of: (a) forming a through-hole in an interlayer dielectric; and (b) forming a metal wiring layer by depositing a metal layer that contains aluminum as its major component and 0.1-3 wt % of beryllium, on the interlayer dielectric and in the through-hole.
The fabrication method according to the present invention can improve the fluidity of an aluminum alloy as stated above with the result that the temperature for sputtering the aluminum alloy layer can be reduced. The fabrication method of the present invention therefore not only restrains the occurrence of whiskers caused by the growth of an aluminum monocrystal, which is produced at high temperatures, but also prevents the development of short circuits between wiring layers. Moreover, in a contact hole on the substrate including electronic elements, the reaction between aluminum in the wiring layer and silicon in the substrate can be restrained by reducing the temperature in the sputtering of the aluminum alloy layer. This results in resistance to a rise in the electric characteristics problem such as leaks.
In the step (b), the metal wiring layer may be formed by sputtering a target material containing aluminum as its major component and 0.1-3 wt % of beryllium at a temperature of 500° C. or less. The target material may further include at least one of magnesium and titanium in an amount of 0.1 to 3 wt % where necessary. It may also include copper and silicon as required.
In the step (b), the metal wiring layer may be formed by: a step of forming a first aluminum layer comprising an alloy containing aluminum as its major component at a temperature of 200° C. or less; and a step of forming a second aluminum layer comprising an alloy containing aluminum as its major component at a temperature of 300-500° C. on the first aluminum layer.
The first aluminum layer is formed at temperatures of 200° C. or less and preferably 30 to 100° C. thereby restraining gasification of gasifiable components contained in the interlayer dielectric and intermediate layers between the interlayer dielectric and the aluminum layer. Here, the intermediate layers means those present between the interlayer dielectric and the aluminum layer, that is, a barrier layer, a wetting layer or the like. Since the gas produced and emitted externally from the intermediate layer is restrained, a reduction in the wett
Asahina Michio
Matsumoto Kazuki
Suzuki Eiji
Oliff & Berridg,e PLC
Rocchegiani Remzo N.
Seiko Epson Corporation
Smith Matthew
LandOfFree
Semiconductor device and method of fabricating the same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Semiconductor device and method of fabricating the same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Semiconductor device and method of fabricating the same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2572416