Filling deep and wide openings with defect-free conductor
Relatively large openings or features in integrated circuit metallization or packaging vias are filled by two plating or electrodeposition processes in sequence. The first electrodeposition process conformally lines the large, high aspect ratio features to define an inner cavity. The second electrodeposition process uses a different solution to bottom-up fill the inner cavity left by the first electrodeposition process. Conformality is typically induced by use of levelers during the first electrodeposition, while accelerators and suppressors may be used to promote bottom-up fill during the second electrodeposition, although either process may employ any of the three additives.
1 . A method of electrochemically filling a conductive material in a feature formed in a surface of a workpiece, comprising:
providing the workpiece with the feature having a width of at least 2 microns and a depth of at least twice the width, wherein the feature and the surface of the workpiece are lined with a seed layer;
performing a first electrodeposition process of the conductive material to form a substantially conformal conductive layer on the seed layer, the conformal conductive layer partially filling the feature and extending over the surface of the workpiece; and
performing a second electrodeposition process to fill a remainder of the feature completely with the conductive material in a bottom-up fashion.
2 . The method of claim 1 , wherein performing the first electrodeposition process includes an electrochemical deposition process using a first solution.
3 . The method of claim 2 , wherein the first solution includes a conformality-promoting species.
4 . The method of claim 3 , wherein the conformality-promoting species includes a leveler.
5 . The method of claim 4 , wherein the first solution comprises a leveler concentration of 2-20 ml/l.
6 . The method of claim 2 , wherein performing the second electrodeposition process includes an electrochemical deposition process using a second solution different from the first solution.
7 . The method of claim 6 , wherein the second solution includes a bottom-up filling promoting species.
8 . The method of claim 7 , wherein the bottom-up filling promoting species includes an accelerator.
9 . The method of claim 8 , wherein the second solution comprises an accelerator concentration of 2-10 ml/l.
10 . The method of claim 1 , further comprising treating a surface of the conformal conductive layer with a treatment solution prior to performing the second electrodeposition process, wherein the solution includes a bottom-up filling promoting species.
11 . The method of claim 10 , further comprising sweeping a surface portion of the conformal conductive layer after treating, wherein the surface portion is on the surface of the workpiece.
12 . The method of claim 10 , further comprising drying the conformal conductive layer after treating.
13 . The method of claim 10 , wherein the bottom-up filling promoting species includes an accelerator.
14 . The method of claim 13 , wherein the treatment solution comprises an accelerator concentration of 2-20 ml/l.
15 . The method of claim 1 , wherein performing the second electrodeposition process comprises electrochemical mechanical deposition.
16 . The method of claim 1 , wherein performing the first electrodeposition to form the substantially conformal conductive layer within the feature results in an inner cavity having a width.
17 . The method of claim 16 , wherein the width is less than 1 micron.
18 . The method of claim 16 , wherein the width is less than 0.6 micron.
19 . The method of claim 1 , wherein the feature has a depth greater than 50 μm.
20 . A method of electrochemically filling a conductive material in a feature formed in a surface of wafer, comprising:
electrodepositing the conductive material from a first solution onto the surface to partially fill the feature having an aspect ratio larger than 2 with a conformal conductor coating an interior of the feature so that an inner cavity is formed; and
electrodepositing the conductive material from a second solution different from the first solution onto the conformal conductor to completely fill the inner cavity in a bottom-up manner.
21 . The method of claim 20 , wherein a width of the inner cavity is less than 1 micron.
22 . The method of claim 20 , wherein a width of the inner cavity is less than 0.6 micron.
23 . The method of claim 20 , wherein the first solution includes a conformality-promoting species.
24 . The method of claim 23 , wherein the conformality-promoting species includes a leveler.
25 . The method of claim 24 , wherein the first solution comprises a leveler concentration of 2-20 ml/l.
26 . The method of claim 20 , wherein the second solution includes a bottom-up filling promoting species.
27 . The method of claim 26 , wherein the bottom-up filling promoting species includes an accelerator.
28 . The method of claim 27 , wherein the second solution comprises an accelerator concentration of 2-10 ml/l.
29 . A method for electrochemically filling conductive material in a feature formed in a surface of a workpiece, comprising:
performing a first electrodeposition process to form a substantially conformal conductive layer that partially fills the feature, wherein the feature has a depth at least twice its width, and wherein after the first electrodeposition process the substantially conformal conductive layer defining an inner cavity in the feature, the inner cavity having a width less than one micron; and
performing a second electrodeposition process different from the first process to fill the inner cavity completely with conductive material.
30 . The method of claim 29 , wherein the substantially conformal conductive layer has a thickness of about 1-10 microns.
31 . The method of claim 29 , wherein performing the first electrodeposition process includes an electrochemical deposition process using a first solution including a leveler.
32 . The method of claim 31 , wherein performing the second electrodeposition process uses a second solution different from the first solution.
33 . The method of claim 32 , wherein the second solution includes an accelerator.
34 . The method of claim 29 , wherein prior to performing the first electrodeposition process, the feature has an opening too wide for suppressors and accelerators to differentiate between interior surfaces of the feature and upper surfaces of the workpiece.
35 . The method of claim 34 , wherein prior to performing the first electrodeposition process, the feature has a width greater than 2 microns.
36 . The method of claim 35 , wherein prior to performing the first electrodeposition process, the feature has a width greater than 5 microns.
37 . The method of claim 29 , wherein the conductive material and the conformal conductive layer both comprise copper.