U.S. patent application number 09/729220 was filed with the patent office on 2002-06-06 for method for removing carbon-rich particles adhered on a copper surface.
This patent application is currently assigned to United Microelectronics Corp.. Invention is credited to Hsu, Chia-Lin, Tsai, Teng-Chun, Wei, Yung-Tsung, Yang, Ming-Sheng.
Application Number | 20020068455 09/729220 |
Document ID | / |
Family ID | 24930077 |
Filed Date | 2002-06-06 |
United States Patent
Application |
20020068455 |
Kind Code |
A1 |
Tsai, Teng-Chun ; et
al. |
June 6, 2002 |
Method for removing carbon-rich particles adhered on a copper
surface
Abstract
A method for removing carbon-rich particles adhered on a copper
surface, especially on a copper surface of a copper/low k
dielectric dual damascene structure is provided. A barrier layer
and a barrier-CMP stopping layer are formed between the copper
layer and the low k dielectric layer of the dual damascene
structure. After a Cu-CMP process and a barrier CMP process, a
chemical buffing polishing process using an acidic aqueous solution
under a downward force of about 0.5 to 3 psi is performed to remove
carbon-rich particles adhered on the exposed copper surface, which
is due to the low k dielectric layer having at least 90% carbon
element being exposed and then polished during the Cu-CMP process
and the barrier CMP process, resulting from a dishing phenomenon of
the copper layer occurring during the two CMP processes.
Alternately, a first chemical buffing polishing process is followed
after the Cu-CMP process, and a second chemical buffing polishing
process is followed after the barrier CMP process.
Inventors: |
Tsai, Teng-Chun; (Hsin-Chu
City, TW) ; Hsu, Chia-Lin; (Taipei City, TW) ;
Wei, Yung-Tsung; (Pai-Ho Chen, TW) ; Yang,
Ming-Sheng; (Hsin-Chu City, TW) |
Correspondence
Address: |
Benjamin J. Hauptman
LOWE HAUPTMAN GILMAN & BERNER
Suite 310
1700 Diagonal Road
Alexandria
VA
22314
US
|
Assignee: |
United Microelectronics
Corp.
|
Family ID: |
24930077 |
Appl. No.: |
09/729220 |
Filed: |
December 5, 2000 |
Current U.S.
Class: |
438/692 ;
257/E21.244; 257/E21.304; 257/E21.583; 438/691; 438/694; 438/695;
438/697; 438/699; 438/703 |
Current CPC
Class: |
H01L 21/31053 20130101;
H01L 21/7684 20130101; H01L 21/02074 20130101; Y10S 438/906
20130101 |
Class at
Publication: |
438/692 ;
438/694; 438/691; 438/695; 438/697; 438/699; 438/703 |
International
Class: |
H01L 021/44; H01L
021/302; H01L 021/461; H01L 021/311 |
Claims
What is claimed is:
1. A method for removing carbon-rich particles adhered on a copper
surface, said method comprising: providing a semiconductor
substrate having a substructure comprising devices formed in said
substrate and a metal layer formed thereon; forming a low k
dielectric layer over said substrate; forming a stopping layer on
said low k dielectric layer; patterning said stopping layer and
said low k dielectric layer to form a plurality of via holes for
interconnects; patterning said stopping layer and said low k
dielectric layer to form a plurality of trenches for conductive
lines; forming a conformal blanket layer above the patterned layer
of said stopping layer and said low k dielectric layer as a barrier
layer; forming a copper layer over said barrier layer to fill said
via hole and said trench; performing a copper chemical mechanical
polishing process to planarize said copper layer until said barrier
layer; performing a barrier chemical mechanical polishing process
to remove said barrier layer until said stopping layer; performing
a chemical buffing polishing process using an acidic aqueous
solution to remove said carbon-rich particles adhered on the
exposed copper surface of said copper layer filled in said trench
and said via hole; and performing a post chemical mechanical
polishing cleaning process.
2. The method of claim 1, wherein said low k dielectric layer is
formed of spin-on polymer low k materials.
3. The method of claim 2, wherein said low k dielectric layer is
formed of a spin-on polymer low k material selected from a group
consisting of aromatic hydrocarbons, silk and flare.
4. The method of claim 1, wherein said stopping layer is formed of
silicon nitride (Si.sub.3N.sub.4).
5. The method of claim 1, wherein said stopping layer is formed of
silicon carbide.
6. The method of claim 1, wherein said barrier layer is formed of
Ta.
7. The method of claim 1, wherein said barrier layer is formed of
TaN.
8. The method of claim 1, wherein said copper layer is formed by a
chemical vapor deposition method.
9. The method of claim 1, wherein said copper layer is formed by a
physical vapor deposition method.
10. The method of claim 1, wherein said copper layer is formed by
an electroplating method.
11. The method of claim 1, wherein said chemical buffing polishing
process is performed using an acidic aqueous solution containing a
carboxylic acid.
12. The method of claim 11, wherein said carboxylic acid is citric
acid.
13. The method of claim 11, wherein said carboxylic acid is oxalic
acid.
14. The method of claim 1, wherein said chemical buffing polishing
process is performed using an acidic aqueous solution containing
ammonium carboxylate salt.
15. The method of claim 1, wherein said chemical buffing polishing
process is performed under a downward force of about 0.5 to 3
psi.
16. A method for removing carbon-rich particles adhered on a copper
surface, said method comprising: providing a semiconductor
substrate having a substructure comprising devices formed in said
substrate and a metal layer formed thereon; forming a low k
dielectric layer over said substrate; forming a stopping layer on
said low k dielectric layer; patterning said stopping layer and
said low k dielectric layer to form a plurality of via holes for
interconnects; patterning said stopping layer and said low k
dielectric layer to form a plurality of trenches for conductive
lines; forming a conformal blanket layer above the patterned layer
of said stopping layer and said low k dielectric layer as a barrier
layer; forming a copper layer over said barrier layer to fill said
via hole and said trench; performing a copper chemical mechanical
polishing process to planarize said copper layer until said barrier
layer; performing a first chemical buffing polishing process using
an acidic aqueous solution to remove said carbon-rich particles
adhered on the exposed copper surface of said copper layer filled
in said trench and said via hole; performing a barrier chemical
mechanical polishing process to remove said barrier layer until
said stopping layer; performing a second chemical buffing polishing
process using an acidic aqueous solution to remove said carbon-rich
particles adhered on the exposed copper surface of said copper
layer filled in said trench and said via hole; and performing a
post chemical mechanical polishing cleaning process.
17. The method of claim 16, wherein said low k dielectric layer is
formed of spin-on polymer low k materials.
18. The method of claim 17, wherein said low k dielectric layer is
formed of a spin-on polymer low k material selected from a group
consisting of aromatic hydrocarbons, silk and flare.
19. The method of claim 16, wherein said stopping layer is formed
of silicon nitride (Si.sub.3N.sub.4).
20. The method of claim 16, wherein said stopping layer is formed
of silicon carbide.
21. The method of claim 16, wherein said barrier layer is formed of
Ta.
22. The method of claim 16, wherein said barrier layer is formed of
TaN.
23. The method of claim 16, wherein said copper layer is formed by
a chemical vapor deposition method.
24. The method of claim 16, wherein said copper layer is formed by
a physical vapor deposition method.
25. The method of claim 16, wherein said copper layer is formed by
an electroplating method.
26. The method of claim 16, wherein said first chemical buffing
polishing process is performed using an acidic aqueous solution
containing a carboxylic acid.
27. The method of claim 26, wherein said carboxylic acid is citric
acid.
28. The method of claim 26, wherein said carboxylic acid is oxalic
acid.
29. The method of claim 16, wherein said first chemical buffing
polishing process is performed using an acidic aqueous solution
containing ammonium carboxylate salt.
30. The method of claim 16, wherein said second chemical buffing
polishing process is performed using an acidic aqueous solution
containing a carboxylic acid.
31. The method of claim 30, wherein said carboxylic acid is citric
acid.
32. The method of claim 30, wherein said carboxylic acid is oxalic
acid.
33. The method of claim 16, wherein said second chemical buffing
polishing process is performed using an acidic aqueous solution
containing ammonium carboxylate salt.
34. The method of claim 16, wherein said first chemical buffing
polishing process is performed under a downward force of about 0.5
to 3 psi.
35. The method of claim 16, wherein said second chemical buffing
polishing process is performed under a downward force of about 0.5
to 3 psi.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a semiconductor process.
More particularly, the present invention relates to a method for
removing carbon-rich particles adhered on a metal surface,
especially on the exposed copper surface of a copper/low k
dielectric dual damascene structure.
[0003] 2. Description of the Prior Art
[0004] When the semiconductor process steps into the stage of
deep-submicron, it is a trend to employ a Cu damascene process
combined with a low k material as an interlayer dielectric to
effectively reduce RC delay and improve electromigration property.
FIG. 1A shows a typical copper/low k dielectric dual damascene
structure. A semiconductor substrate 100 having a substructure
comprising devices formed in the substrate and a metal layer formed
thereon (not shown in the figure) is provided. And, a barrier-CMP
stopping layer 104 formed of silicon nitride (Si.sub.3N.sub.4)/or
silicon carbide and a barrier layer 106 of Ta/or TaN are
inter-layers between a low k dielectric layer 102 formed on the
substrate 100 and a copper layer 108. The barrier layer 106 is
served for preventing copper diffusion to the low k dielectric
layer 102.
[0005] Referring to FIG. 1B, during the copper/low k dielectric
dual damascene process, a copper chemical mechanical polishing
process is firstly applied to planarize the copper layer 108 inlaid
into the trench 112 and via hole 110 structures of the low k
dielectric layer 102, until the barrier layer 106. Then, a barrier
chemical mechanical polishing process is followed to remove the
barrier layer 106 until the stopping layer 104. However, the softer
copper metal typically polishes back at a faster rate than the
surrounding material and then causing dishing in the copper layer
108, as shown in FIG. 1B, the CMP copper layer 108 is provided with
a dished structure below the dotted line of the top surface
thereof. The low k dielectric layer 102 is easily exposed and then
polished during the two CMP processes, due to the dishing
phenomenon of the copper layer 108, even though the barrier-CMP
stopping layer 104 is applied on the low k dielectric layer 102.
The low k dielectric generally carbon-rich, containing at least 90%
carbon element, and copper metal and carbon element have reverse
electricity in a neutral/or acidic slurry employed in the copper
CMP and barrier CMP processes. Therefore, there are many
carbon-rich particles produced and adhered on the exposed copper
surface of the copper layer 108 inlaid into the trench 112 and the
via hole 110, during the two CMP processes, which results in a
process defect.
[0006] Accordingly, it is desirable to provide a method for
effectively remove carbon-rich particles adhered on a copper
surface, especially on the exposed copper surface of a copper/low k
dielectric dual damascene structure, and then alleviate the
drawback of the conventional CMP process for copper/low k
dielectric damascene process.
SUMMARY OF THE INVENTION
[0007] It is one object of the present invention to provide a
method for removing carbon-rich particles adhered on a copper
surface, especially on the exposed copper surface of a copper/low k
dielectric dual damascene structure. After a Cu-CMP process and
barrier CMP process are completed, a chemical buffing polishing
process under a downward force of about 0.5 to 3 psi, using an
acidic aqueous solution, is applied on the exposed copper surface
to effectively remove carbon-rich particles adhered thereon, which
is due to the low k dielectric layer containing at least 90% carbon
element being exposed and then polished during the two CMP
processes, coming from a dishing phenomenon of the copper
layer.
[0008] It is another object of the present invention to provide a
method for removing carbon-rich particles adhered on a copper
surface, especially on the exposed copper surface of a copper/low k
dielectric dual damascene structure. After a Cu-CMP process, a
first chemical buffing polishing process using an acidic aqueous
solution is followed, and a second chemical buffing polishing
process using an acidic aqueous solution is applied after a barrier
CMP process. Both of the two chemical buffing processes are used to
remove carbon-rich particles adhered on the exposed copper surface
during the two CMP processes.
[0009] It is a further object of the present invention to provide a
method for removing carbon-rich particles adhered on a copper
surface, which is suitably applied to a low k material chemical
mechanical polishing process.
[0010] In order to achieve the above objects, the present invention
provides a method for removing carbon-rich particles adhered on a
copper surface, especially on the exposed copper surface of a
copper/low k dielectric dual damascene structure. Firstly,
providing a semiconductor substrate having a substructure
comprising devices formed in the substrate and a metal layer formed
thereon. Then, forming a low k dielectric layer over the substrate.
Subsequently, forming a stopping layer on the low k dielectric
layer. Thereafter, patterning the stopping layer and the low k
dielectric layer to form a plurality of via holes for
interconnects, and then patterning the stopping layer and the low k
dielectric layer to form a plurality of trenches for conductive
lines. Afterward, forming a conformal blanket layer above the
patterned layer of the stopping layer and the low k dielectric
layer as a barrier layer. Following, forming a copper layer over
the barrier layer to fill the via hole and the trench. Then,
performing a copper chemical mechanical polishing process to
planarize the copper layer until the barrier layer. Subsequently,
performing a barrier chemical mechanical polishing process to
remove the barrier layer until the stopping layer. Following,
performing a chemical buffing polishing process under a downward
force of about 0.5 to 3 psi using an acidic aqueous solution to
remove the carbon-rich particles adhered on the exposed copper
surface of the copper layer filled in the trench and the via hole.
Finally, performing a post chemical mechanical polishing cleaning
process to remove away dirt left on the exposed copper surface.
Alternately, a first chemical buffing polishing process is applied
after the Cu-CMP process, and a second chemical buffing polishing
process is performed after the barrier CMP process.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The present invention can be best understood through the
following description and accompanying drawings wherein:
[0012] FIG. 1A depicts a schematic cross sectional view of a
conventional copper/low k dielectric dual damascene structure;
[0013] FIG. 1B depicts a schematic cross sectional view of the
conventional copper/low k dielectric dual damascene structure after
a Cu-CMP process and barrier CMP process, in which a dishing
phenomenon of the exposed copper surface occurs;
[0014] FIG. 2A depicts a flow diagram of the processes of a method
according to one embodiment of the present invention; and
[0015] FIG. 2B depicts a flow diagram of the processes of a method
according to one another embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0016] The present method is suitable for removing carbon-rich
particles adhered on a metal surface. However, in embodiments of
the present invention, a copper/low k dielectric dual damascene
structure, as shown in FIG. 1B, is used as an example for employing
the present method.
[0017] In FIG. 1B, the substrate 100 is a semiconductor substrate
having a substructure comprising devices formed in the substrate
100 and a metal layer formed thereon (not shown in the figure). The
low k dielectric layer 102 is carbon-rich, containing at least 90%
carbon element, and can be formed of spin-on polymer, such as
aromatic hydrocarbons, silk and flare. The low k dielectric layer
102 is shown with a trench 112 and a via hole 110 pattern. The
barrier layer 106 is typically a Ta or TaN layer act as a liner
layer for the trench 112 and the via hole 110 for preventing copper
diffusion to the low k dielectric layer 102. A protection layer
formed of silicon nitride/or silicon carbide on the low k
dielectric layer 102 is served as the stopping layer 104 for the
barrier layer's chemical mechanical polishing process. CMP Cu metal
is shown with a dished structure below the dotted line of the top
surface of the copper layer 108.
[0018] The barrier layer 106 of Ta/or TaN is a blanket layer
conformally covering surfaces both inside and out the trench 112
and via hole 110 area. The physical vapor deposition (PVD)
technique is a preferred method for the considerations of low film
stress, good coverage and good adhesion.
[0019] The copper layer 108 fills into the trench 112 and via hole
110, and can be deposited using PVD, CVD, or electroplating.
Typically, the copper deposition thickness can range from 1 um to
several microns.
[0020] In the usual method of dual damascene, the low k dielectric
layer 108 is patterned twice by the conventional photolithography
and etching method. One forms the via hole 110 for interconnect and
then the second forms the trench 112 for the conductive line, such
as a copper line, in the low k dielectric layer 102.
[0021] Referring to FIG. 2A, after the copper layer 108 is
deposited over the barrier layer 106, a copper chemical mechanical
polishing process 200 is performed to planarize the copper layer
108 until the barrier layer 106. Then, a barrier chemical
mechanical polishing process 202 is followed to remove the barrier
layer 106 until the stopping layer 104. As shown in FIG. 1B, during
these two CMP processes, the low k dielectric layer 102 is easily
exposed and then polished due to the dishing phenomenon of the
copper layer 108, as described above. And then, there are many
carbon-rich particles produced and adhered on the exposed copper
surface, which results in a defect in the dual damascene process.
Therefore, a chemical buffing polishing process 204 using an acidic
aqueous solution under a downward force of about 0.5 to 3 psi is
applied to remove the carbon-rich particles adhered on the exposed
copper surface through a chemical reaction. The acidic aqueous
solution can be a kind of carboxylic acid aqueous solution, such as
an acidic aqueous solution containing citric acid or oxalic acid.
Alternately, the acidic aqueous solution can contain ammomium
carboxylate salt. At final, a post CMP cleaning process is
performed to remove dirt left on the exposed copper surface.
[0022] The low k dielectric layer 102 may have been exposed during
a Cu-CMP process. Therefore, in one another embodiment of the
present invention, referring to FIG. 2B, after a Cu-CMP process
300, a first chemical buffing process 302 using an acidic aqueous
solution under a downward force of about 0.5 to 3 psi, is applied
to remove carbon-rich particles adhered on the exposed copper
surface through a chemical reaction. Subsequently, a barrier CMP
process 304 is performed to remove the barrier layer 106 until the
stopping layer 104, and then a second chemical buffing process
using an acidic aqueous solution under a downward force of about
0.5 to 3 psi is followed to remove carbon-rich particles adhered on
the exposed copper surface. The acidic aqueous solution can be a
kind of aqueous solution containing a carboxylic acid, such as
citric acid or oxalic acid. Alternately, the acidic aqueous
solution can contain ammonium carboxylate salt. Finally, a post CMP
cleaning process is employed to remove dirt left on the exposed
copper surface.
[0023] The preferred embodiments are only used to illustrate the
present invention, not intended to limit the scope thereof. Many
modifications of the preferred embodiments can be made without
departing from the spirit of the present invention.
* * * * *