Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Of specified material other than unalloyed aluminum
Reexamination Certificate
1999-12-02
2001-09-11
Quach, T. N. (Department: 2814)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Of specified material other than unalloyed aluminum
C257S764000, C257S765000, C257S767000
Reexamination Certificate
active
06288450
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a wiring structure for a semiconductor device and a method for manufacturing the same.
2. Description of the Related Art
Aluminum having the second best conductivity after copper is used as a main material for wiring of a semiconductor device such as an integrated circuit (IC). However, aluminum wiring is vulnerable to breakage caused by electromigration. In order to increase the resistance against electromigration and to lengthen a life of the wiring, technologies are proposed to use an aluminum alloy such as Al—Cu and Al—Si—Cu or to introduce a stacked structure provided with the aluminum alloy as an upper layer and with a refractory metal layer composed of Ti, TiN, WSi or the like as a lower layer.
By forming the aluminum alloy layer, through the refractory metal layer, on an insulating layer on the semiconductor substrate such as Si, the aluminum alloy of high quality having few defects that may cause such electromigration and having a large grain diameter can be formed, and because the refractory layer used as the lower layer functions as a bypass for parts suffering from electromigration, the life of the wiring can be lengthened accordingly.
However, it was reported by M. Hosaka et al., in Proceedings of 36th International Reliability Physics Symposium (1998, P329) that, when the aluminum alloy layer is formed on the refractory metal layer described above, a compound layer composed of Al
3
Ti is produced between the aluminum alloy layer and the refractory metal layer and an interface of compound layers acts as a diffusion path for aluminum. If such compound layers produced between aluminum and the refractory metal are formed in an ranged manner on the wiring region, it reduces remarkably the resistance against electromigration.
SUMMARY OF THE INVENTION
In view of the above, it is an object of the present invention to provide a wiring structure being excellent in the resistance against electromigration and being able to lengthen a life of the wiring and a method for manufacturing the same.
According to a first aspect of the present invention, there is provided a wiring structure for a semiconductor device comprising:
a refractory metal layer formed on a semiconductor substrate;
an aluminum alloy layer stacked on the refractory metal layer;
a stacked structure wherein a layer of a compound composed of aluminum contained in said aluminum alloy and of a metal contained in the refractory metal is produced between both layers;
whereby the refractory metal layer is parted by the aluminum alloy layer in an extended direction of wiring and a length of an interval between parted refractory metal layer portions exceeds a value being twice as large as a thickness of said compound layer.
Furthermore, according to the configuration of the present invention, since the refractory metal is parted or separated in the extended direction of the wiring and the length of the interval between the parted refractory metal layer portions is set to be a value being twice as large as the thickness of the compound layer, it is possible to prevent the compound layer produced between the refractory metal layer and the aluminum alloy layer from growing in a ranged manner in the extended direction.
In the foregoing, a preferable mode is one wherein a length of the refractory metal layer portion in the direction of the wiring is smaller than Blech's critical length. By setting the length of the refractory metal layer portion in the direction of the wiring to be smaller than the Blech's critical length, the resistance against electromigration can be increased more. Though the Blech's critical length is increased or decreased depending on stress introduced into the aluminum alloy layer disposed on the refractory metal layer, since it is approximately 100 &mgr;m, the length of refractory metal layer in the direction of the wiring is preferably about 100 &mgr;m or less.
Also, a preferable mode is one wherein the parted region between the refractory metal layer portions extends at an oblique angle with respect to an extended direction of the wiring.
Also, a preferable mode is one wherein the refractory metal layer is stacked on an insulating layer formed on the semiconductor substrate.
Also, a preferable mode is one wherein the insulating layer, on which the refractory metal layers are stacked, is provided with a concave portion in which a distance between its side walls being opposite to each other increases as it moves from its top part to its bottom part.
Furthermore, a preferable mode is one wherein the refractory metal layer is composed of titanium.
According to a second aspect of the present invention, there is provided a method for forming wiring for semiconductor device comprising the steps of:
forming refractory metal layers each having almost the same thickness on an insulating layer on a semiconductor substrate;
performing selectively etching processing on the refractory metal layers to make the insulating layer partially exposed from the refractory metal layers along a wiring region on which wiring is established;
forming an aluminum alloy layer on the refractory metal layer containing the region in which the insulating layer is exposed; and
taking off unnecessary portion of a stacked structure to form wiring for the structure containing the refractory metal layer and the aluminum alloy layer along the wiring region.
In the foregoing, it is preferable that a length of the exposed region of the insulating layer to be exposed by the etching processing performed on the refractory metal layer along an extended direction of the wiring region exceeds a value being twice as large as a thickness of a compound film produced by a reaction of a metal contained in the refractory metal layer with aluminum contained in said aluminum alloy layer and a width being rectangular to the extended direction in the exposed region is larger than that of the wiring region.
Also, it is preferable that a length between the exposed regions in the refractory metal layer is smaller than Blech's critical length.
Also, it is preferable that the exposed region in the refractory metal layer is defined by a rectangular etching hole formed along the wiring region.
Also, it is preferable that the exposed region on the refractory metal layer is defined by an etching trench arranged on the wiring region in a lattice form in a manner that it forms a tilt angle with respect to the extended direction of the wiring region.
Also, it is preferable that a length of a diagonal line of a refractory metal line partitioned by the lattice-like etching trench is smaller than Blech's critical length.
According to a third aspect of the present invention, there is provided a method for forming wiring comprising the steps of:
forming an etching hole along a wiring region on a semiconductor substrate wherein a distance between its side walls being opposite to each other increases as it moves from its top part to its bottom part;
stacking a refractory metal layer on an insulating film having its thickness that does not completely cover an etching hole without allowing said refractory metal layer to grow along side walls of said etching hole from a bottom of the etching hole to its top in an ranged manner;
forming an aluminum alloy layer on the refractory metal layer containing the region on which the etching hole is formed; and
taking off, by using an etching method, unnecessary parts of the stacked structure in order to form wiring of a stacked structure containing the refractory metal layer and the aluminum alloy layer along the wiring region.
In the foregoing, a preferable mode is one wherein a length, along the extended direction of the wiring region, of a vacant portion of the refractory metal layer formed to respond to the etching hole of the insulating film exceeds a value being twice as large as a thickness of a compound film produced by the reaction of the refractory metal layer with the aluminum alloy layer and a length being rectang
Nakamura Makiko
Narita Tadashi
Jones Volentine PLLC
OKI Electric Industry Co., Ltd.
Quach T. N.
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