Electrical connection and forming method thereof
An electrical connection includes a first driving substrate, a first adhesive layer, a first bonding pad a first bonding pad and a second bonding pad. The first driving substrate includes a first substrate and a first dielectric layer on the first substrate. The first adhesive layer is at a sidewall of the first dielectric layer of the first driving substrate. The first bonding pad is on the first substrate of the first driving substrate and in contact with the first adhesive layer, and the first bonding pad includes a plurality of grains, the grains are connected with each other, the grains include [111]-oriented copper grains, and a maximum width of the first bonding pad is equal to or less than 8 microns. The second bonding pad is on the first bonding pad.
1 . An electrical connection, comprising:
a first driving substrate comprising a first substrate and a first dielectric layer on the first substrate;
a first adhesive layer at a sidewall of the first dielectric layer of the first driving substrate;
a first bonding pad on the first substrate of the first driving substrate and contact with the first adhesive layer, wherein the first bonding pad comprises a plurality of grains, the grains are connected with each other, the grains include [111]-oriented copper grains, and a maximum width of the first bonding pad is equal to or less than 8 microns, wherein a sidewall of the first bonding pad comprises a non-[111]-oriented copper grain region, a bottom of the non-[111]-oriented copper grain region is higher than a bottom of the first bonding pad; and
a second bonding pad on the first bonding pad.
2 . The electrical connection of claim 1 , wherein an interface is between the first bonding pad and the second bonding pad, when the maximum width of the first bonding pad is in a range between 4 microns and 8 microns, at a substantial maximum width of the interface, a length covered by the [111]-oriented copper grains accounts for 60% of the substantial maximum width of the interface.
3 . The electrical connection of claim 2 , wherein the interface is tortuous.
4 . The electrical connection of claim 1 , wherein an interface is between the first bonding pad and the second bonding pad, when the maximum width of the first bonding pad is equal to or less than 4 microns, at a substantial maximum width of the interface, a length covered by the [111]-oriented copper grains accounts for 40% of the substantial maximum width of the interface.
5 . The electrical connection of claim 1 , wherein a vertical distance between the bottom of the non-[111]-oriented copper grain region and the bottom of the first bonding pad is more than 50% of a thickness of the first bonding pad.
6 . The electrical connection of claim 1 , wherein a portion of the second bonding pad is in contact with the first dielectric layer.
7 . A forming method of an electrical connection, comprising:
forming a first bonding pad by using a first periodic reverse electroplating, wherein the first bonding pad comprises a plurality of [111]-oriented copper grains, and a maximum width of the first bonding pad is equal to or less than 8 microns, wherein forming the first bonding pad by using the first periodic reverse electroplating comprises:
providing an electroplating apparatus comprising an anode immersed in a electroplating solution;
placing a first driving substrate at a cathode of the electroplating apparatus, wherein the first driving substrate has a recess; and
providing a pulse current to the first driving substrate, wherein the pulse current comprises a plurality of pulse periods each comprising a forward current and a backward current, a current density of the forward current is in a range between 6 A/dm 2 to 12 A/dm 2 , and a current density of the backward current is in a range between 4 A/dm 2 to 8 A/dm 2 ;
forming a second bonding pad by using a second periodic reverse electroplating, wherein the second bonding pad comprises a plurality of [111]-oriented copper grains, and a maximum width of the second bonding pad is equal to or less than 8 microns; and
bonding a surface of the first bonding pad to a surface of the second bonding pad.
8 . The forming method of claim 7 , wherein a duration of the forward current is in a range between 75 milliseconds to 85 milliseconds, and a duration of the backward current is in a range between 4 milliseconds to 8 milliseconds.
9 . The forming method of claim 7 , wherein a bonding temperature of bonding the surface of the first bonding pad to the surface of the second bonding pad is between 70 degree Celsius and 250 degree Celsius.
10 . The forming method of claim 7 , wherein at a substantial maximum width of the surface of the first bonding pad, a length covered by the [111]-oriented copper grains accounts for 60% of the substantial maximum width of the surface of the first bonding pad.
11 . The forming method of claim 10 , wherein at the substantial maximum width of the surface of the first bonding pad, a length covered by the [111]-oriented copper grains accounts for 90% of the substantial maximum width of the surface of the first bonding pad.
12 . The forming method of claim 7 , wherein an interface is formed after bonding the surface of the first bonding pad to the surface of the second bonding pad, when a maximum width of the first bonding pad is in a range between 4 microns and 8 microns, at a substantial maximum width of the interface, a length covered by the [111]-oriented copper grains accounts for 60% of the substantial maximum width of the interface.
13 . The forming method of claim 7 , wherein an interface is formed after bonding the surface of the first bonding pad to the surface of the second bonding pad, when a maximum width of the first bonding pad is less than 4 microns, at a substantial maximum width of the interface, a length covered by the [111]-oriented copper grains accounts for 40% of the substantial maximum width of the interface.