Abrading – Abrading process – With tool treating or forming
Reexamination Certificate
2000-10-02
2004-10-05
Shakeri, Hadi (Department: 3723)
Abrading
Abrading process
With tool treating or forming
C451S168000, C451S288000, C451S305000, C451S443000, C451S072000
Reexamination Certificate
active
06800020
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to chemical mechanical polishing (CMP) Em systems and techniques for improving the performance and effectiveness of CMP operations. Specifically, the present invention relates to the CUM systems that utilize a web-style conditioner for conditioning pad surfaces.
2. Description of the Related Art
In the fabrication of semiconductor devices, there is a need to perform CMP operations, including polishing, buffing and wafer cleaning. Typically, integrated circuit devices are in the form of multi-level structures. At the substrate level, transistor devices having diffusion regions are formed. In subsequent levels, interconnect metallization lines are patterned and electrically connected to the transistor devices to define the desired functional device. As is well known, patterned conductive layers are insulated from other conductive layers by dielectric materials, such as silicon dioxide. At each metallization level and/or associated dielectric layer, there is a need to planarize the metal and/or dielectric material. Without planarization, fabrication of additional metallization layers becomes substantially more difficult due to the higher variations in the surface topography. In other applications, metallization line patterns are formed in the dielectric material, and then metal CMP operations are performed to remove excess metallization.
CMP systems typically implement belt, orbital, or brush stations in which belts, pads, or brushes are used to polish, buff, and scrub one or both sides of a wafer. Slurry is used to facilitate and enhance the CMP operation. Slurry is most usually introduced onto a moving preparation surface, e.g., belt, pad, brush, and the like, and distributed over the preparation surface as well as the surface of the semiconductor wafer being buffed, polished, or otherwise prepared by the CMP process. The distribution is generally accomplished by a combination of the movement of the preparation surface, the movement of the semiconductor wafer and the friction created between the semiconductor wafer and the preparation surface.
FIG. 1
illustrates an exemplary prior art CMP system
100
. The CMP system
100
of
FIG. 1
is a belt-type system, so designated because the preparation surface is an endless polishing pad
108
mounted on two drums
114
which drive the polishing pad
108
in a rotational motion as indicated by polishing pad rotation directional arrows
116
. A wafer
102
is mounted on a carrier
104
. The carrier
104
is rotated in direction
106
. The rotating wafer
102
is then applied against the rotating polishing pad
108
. Some CMP processes require significant force F to be applied. A platen
112
is provided to stabilize the polishing pad
108
and to provide a solid surface onto which to apply the wafer
102
. Slurry
118
including of typically an aqueous solution containing dispersed abrasive particles (e.g., SiO
2
, Al
2
O
3
, CeO
2
, etc.) is introduced upstream of the wafer
102
. The process of scrubbing, buffing and polishing of the surface of the wafer could be achieved by using either a non-fixed abrasive polishing pad or a fixed abrasive polishing pad. Due to having different characteristics, the conditioning of the non-fixed abrasive polishing pads are to some extent different than that of the fixed abrasive polishing pads. Below are brief descriptions of the conditioning of non-fixed abrasive polishing pads as well as fixed abrasive polishing pads.
The non-fixed abrasive polishing pads are composed of porous or fibrous materials and fixed abrasive particles, which are introduced into the system in the form of an aqueous solution (also known as slurry). As illustrated in
FIG. 1
, after the non-fixed abrasive polishing pad
108
polishes the wafer
102
, the conditioner disk
122
of the conditioning assembly
110
is applied to the surface of the non-fixed abrasive polishing pad
108
thus removing the residue, consisting of abrasive particles of the slurry and the particulates removed from the wafer
102
(which clog the porous
61
surface of the pad
108
). As illustrated in the cross-sectional view of a conditioning assembly
110
of
FIG. 1A-1
, the surface of a conditioner disk
122
includes a diamond array
124
. The non-fixed abrasive polishing pad
108
is conditioned as the conditioner disk
122
and thus the diamond array
124
are moved along a track bar
123
and across the polishing surface of the non-fixed abrasive polishing pad
108
. Accordingly, in non-fixed abrasive polishing pad CMP systems, the conditioner disk
122
removes the particulate materials and the attached slurry materials from the surface of the non-fixed abrasive polishing pad
108
thereby cleaning and roughening the non-fixed abrasive polishing pad
108
as well as exposing a fresh layer of the non-fixed abrasive polishing pad.
Ordinarily, different sizes of conditioning disks can be used to condition the surface of the non-fixed abrasive polishing pad
108
. Furthermore, as some non-fixed abrasive polishing pads require conditioning by extra fine abrasive particles, the conditioning disks may have abrasive particles having various sizes. One example of abrasive particles is defined as diamond arrays, which may be mounted on the carrier disks utilizing different bonding technologies. However, one common problem in utilizing diamond arrays for conditioning the non-fixed abrasive polishing pads is the dislodgment of diamonds of a diamond arrays. As illustrated in
FIG. 1A-2
, the dislodgment of diamonds
124
′ of a diamond array
124
occurs as a result of the extensive wear of the conditioning disk
122
. Furthermore, the dislodgment of the diamonds
124
′ occur irrespective of the size of the carrier disks
122
and the dimensions of the diamonds
124
′ of the diamond arrays
124
and the technology implemented to mount the diamond arrays
124
on the conditioner disks
122
. The dislodged diamonds
124
′ could remain on the polishing pad
108
, could be caught between polishing pad
108
and the wafer
102
during the polishing cycle, and could scratch the surface of the wafer
102
being polished.
Another challenge in utilizing conditioning disks with diamond arrays is maintaining well-kept diamond arrays having very small diamonds. Even after a short wear time of the conditioning disk, these diamonds easily become loose. Even small diamonds being loose on a pad during polishing could cause severe scratching of the surface of the semiconductor wafer. This could create electrical shorts in the electronic circuit devices, and could make some devices on the wafer inoperable. This severely reduces yield. Therefore, conditioning disks should be often replaced to avoid excessive wear. In either situation, the dislodgment of the diamonds
124
′ as well as the extensive wear of the conditioning disk reduce the removal rate of the particulates and the attached slurry. They also increase the overall defects and micro-scratching of wafers during the CMP process. Furthermore, the replacement of the entire conditioner disk is very inconvenient as well as time consuming. Additionally, the CMP system must be taken off-line so as to allow the replacement of the entire conditioner disk or the dislodged diamonds, thereby reducing the throughput of the CMP system.
One particular type of polishing pad, which requires conditioning by extra fine abrasive materials, is a fixed abrasive polishing pad.
FIG. 1B-1
depicts a fixed-abrasive polishing pad
108
having a fixed abrasive polishing layer. Embedded and extended through out the surface of this type of polishing pad are several three-dimensional cylindrical protrusions, defined as “pillars”
108
′. Each pillar
108
′ may have a diameter of approximately about 200 micrometers and an approximate height of about 40 micrometers. The cross-sectional view of the fixed abrasive polishing pad of
FIG. 1B-2
reveals that each pillar
108
′ contains a plurality of abrasive par
Boyd John M.
Mikhaylich Katrina A.
Lam Research Corporation
Martine & Penilla LLP
Shakeri Hadi
LandOfFree
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