Semiconductor device manufacturing: process – Chemical etching – Combined with the removal of material by nonchemical means
Reexamination Certificate
2000-12-05
2002-09-24
Everhart, Caridad (Department: 2825)
Semiconductor device manufacturing: process
Chemical etching
Combined with the removal of material by nonchemical means
C438S691000, C438S906000
Reexamination Certificate
active
06455432
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
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.
2. Description of the Prior Art
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
3
N
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
.
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.
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
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.
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.
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.
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.
REFERENCES:
patent: 6140239 (2000-10-01), Avanzino et al.
patent: 6147002 (2000-11-01), Kneer
patent: 6162301 (2000-12-01), Zhang et al.
patent: 6177364 (2001-01-01), Huang
patent: 6200899 (2001-03-01), Fournier
patent: 6218290 (2001-04-01), Schonauer et al.
patent: 6245662 (2001-06-01), Naik et al.
patent: 6251770 (2001-06-01), Uglow et al.
Hsu Chia-Lin
Tsai Teng-Chun
Wei Yung-Tsung
Yang Ming-Sheng
LandOfFree
Method for removing carbon-rich particles adhered on a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for removing carbon-rich particles adhered on a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for removing carbon-rich particles adhered on a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2832635