Aluminum structures
Devices with aluminum structures and methods of fabrication are provided. An exemplary device includes an interconnect structure and an aluminum structure electrically connected to the interconnect structure. The aluminum structure includes a first aluminum layer, a migration barrier layer over the first aluminum layer, and a second aluminum layer over the migration barrier layer.
1 . A device comprising:
an interconnect structure; and
an aluminum structure electrically connected to the interconnect structure, wherein the aluminum structure comprises:
a first aluminum layer;
a migration barrier layer over the first aluminum layer; and
a second aluminum layer over the migration barrier layer; wherein the aluminum structure has a sidewall formed by the first aluminum layer, the migration barrier layer, and the second aluminum layer, and wherein the sidewall includes an undercut portion at the migration barrier layer.
2 . The device of claim 1 , further comprising a dielectric layer over the interconnect structure, wherein the dielectric layer contacts the sidewall at the migration barrier layer.
3 . The device of claim 1 , wherein the aluminum structure has a height in a z-direction of from 0.5 micrometers to 5 micrometers, and wherein the migration barrier layer has a thickness in the z-direction of from 2 nanometers to 6 nanometers.
4 . The device of claim 1 , wherein the first aluminum layer has a thickness T 1 in a z-direction, wherein the second aluminum layer has a thickness T 2 in the z-direction, and wherein T 1 :T 2 is from 3:1 to 1:3.
5 . The device of claim 1 , wherein the migration barrier layer is a first migration barrier layer and wherein the device further comprises:
a second migration barrier layer over the second aluminum layer; and
a third aluminum layer over the second migration barrier layer.
6 . The device of claim 1 , wherein the migration barrier layer comprises aluminum oxide, aluminum nitride, and/or aluminum oxynitride, and/or is a ceramic layer.
7 . The device of claim 1 , wherein:
the first aluminum layer has a first lateral edge forming a portion of the sidewall;
the second aluminum layer has a second lateral edge forming a portion of the sidewall;
the migration barrier layer has a barrier lateral edge forming a portion of the sidewall;
the first lateral edge and the second lateral edge define a plane; and
the barrier lateral edge is distanced from the plane by less than 10 nanometers (nm) to define the undercut portion between the first aluminum layer and the second aluminum layer.
8 . A semiconductor device comprising:
a first aluminum layer;
a ceramic layer directly on the first aluminum layer, wherein the ceramic layer is comprised of aluminum oxide, aluminum nitride, and/or aluminum oxynitride; and
a second aluminum layer directly on the ceramic layer, wherein the first aluminum layer, the ceramic layer, and the second aluminum layer form a conductive structure having a sidewall, and wherein the sidewall includes an undercut portion at the ceramic layer.
9 . The semiconductor device of claim 8 , further comprising:
an interconnect structure;
a dielectric layer lying over the interconnect structure; and
a metal diffusion barrier over the dielectric layer and over an uncovered portion of an upper surface of the interconnect structure, wherein the metal diffusion barrier comprises tantalum nitride (TaN) or titanium nitride (TiN);
wherein the first aluminum layer, the ceramic layer, and the second aluminum layer comprise a conductive via extending through the dielectric layer to electrically contact the interconnect structure, and wherein the first aluminum layer is on the metal diffusion barrier.
10 . The semiconductor device of claim 9 , further comprising a passivation layer over the conductive via, wherein the passivation layer comprises silicon oxide (SiO 2 ) or silicon nitride (SiN), and wherein the passivation layer has a planarized upper surface.
11 . The semiconductor device of claim 10 , further comprising:
an opening through the passivation layer exposing a portion of the second aluminum layer;
a conductive liner over the second aluminum layer in the opening, wherein the conductive liner comprises chromium, copper, or aluminum; and
a solder bump over the conductive liner and in electrical connection with the aluminum structure.
12 . A method for fabricating a semiconductor device comprising:
depositing a first layer of aluminum, wherein the first layer of aluminum has an upper surface;
treating the upper surface of the first layer of aluminum to form a migration barrier layer by performing a vacuum break and forming native aluminum oxide on the upper surface of the first layer of aluminum, wherein a remainder of the first layer of aluminum under the migration barrier layer remains unmodified; and
depositing a second layer of aluminum over the migration barrier layer.
13 . The method of claim 12 , wherein the migration barrier layer is a first migration barrier layer and wherein the second layer of aluminum has an upper surface, the method further comprising:
treating the upper surface of the second layer of aluminum to form a second migration barrier layer, wherein a remainder of the second layer of aluminum under the second migration barrier layer remains unmodified; and
depositing a third layer of aluminum over the second migration barrier layer.
14 . The method of claim 12 , further comprising:
etching the second layer of aluminum, the migration barrier layer, and the first layer of aluminum to form a conductive line having a first sidewall and a second sidewall, wherein the conductive line has a line width in an x-direction from the first sidewall to the second sidewall, and wherein the line width is less than 2 micrometers.
15 . The method of claim 12 , further comprising:
etching the second layer of aluminum, the migration barrier layer, and the first layer of aluminum to form a conductive structure having a first sidewall; and
depositing a dielectric material over the conductive structure.
16 . The method of claim 15 , wherein when etching the second layer of aluminum, the migration barrier layer, and the first layer of aluminum to form a conductive structure having a first sidewall an undercut void is formed from an edge of the migration barrier layer, and wherein the undercut void has a width of less than 10 nanometers (nm).
17 . The method of claim 15 , wherein after etching the second layer of aluminum, the migration barrier layer, and the first layer of aluminum to form a conductive structure having a first sidewall the first layer of aluminum has a first lateral edge, the second layer of aluminum has a second lateral edge, the migration barrier layer has a barrier lateral edge, the first lateral edge and the second lateral edge define a plane, and the barrier lateral edge is distanced from the plane by less than 10 nanometers (nm).
18 . The method of claim 12 , wherein treating the upper surface of the first layer of aluminum to form the migration barrier layer further comprises incorporating nitrogen into a portion of the native aluminum oxide to form an aluminum oxynitride layer.
19 . The method of claim 12 , wherein treating the upper surface of the first layer of aluminum to form the migration barrier layer further comprises performing a plasma ionization process with oxygen (O 2 ), nitrogen (N 2 ), or nitrous oxide (N 2 O) after the vacuum break.
20 . The method of claim 19 , wherein the plasma ionization process is performed at a temperature of from 25 to 400° C., at a pressure of from 0.001 to 10 torr, and for a time duration of from 10 to 120 seconds.