Abrading – Abrading process – With tool treating or forming
Reexamination Certificate
2000-04-10
2001-11-06
Eley, Timothy V. (Department: 3723)
Abrading
Abrading process
With tool treating or forming
C451S036000, C451S057000, C451S059000, C451S065000, C451S072000, C451S168000, C451S288000, C451S305000, C451S306000, C451S307000, C451S443000, C451S495000, C451S493000, C451S530000
Reexamination Certificate
active
06312319
ABSTRACT:
FIELD OF THE INVENTION
This invention generally relates to the field of semiconductor processing equipment and particularly to a polishing apparatus. More specifically this invention relates to a polishing media magazine for improved polishing.
BACKGROUND OF THE INVENTION
Polishing a workpiece to produce a mirror-like, defect-free surface has applications in many fields of endeavor. Such polishing processes have become extremely important and widespread, for example, in the fabrication of semiconductor devices. The critical step of polishing a semiconductive wafer or substrate is required at a number of different stages along the varied processes employed to fabricate semiconductor devices.
The manufacture of integrated circuits generally involves an elaborate system of fabricating semiconductor devices on a wafer or substrate and connecting the devices together. The devices are connected by a process generally referred to as metalization, in which connecting lines of metal, often aluminum, are applied by vacuum deposition or other suitable processes.
The performance level of semiconductor devices employing a conventional single metal layer connecting the devices is fast becoming unsuitable. Modem, high performance devices utilize multilevel metal interconnections. Multilevel connections may be constructed by depositing a dielectric or insulating layer over a first metal layer, etching via holes throughout the dielectric layer, and then depositing a second metal layer which fill the via holes to connect with the first metal layer. These devices offer higher device density and shortened interconnection lengths between the devices.
Since each of these metal and dielectric layers have an appreciable thickness, the wafer substrate is left with a non-planar topography as the various layers are patterned on top of one another. This type of non-planarity is often unacceptable in high density devices because the depth of field of the lithographic equipment that is used to print the smaller line width circuits on the wafer does not have a depth of focus sufficient to compensate for even small variations in wafer planarity.
In addition to the non-planarity caused by the fabricated device patterns, in-process wafer polishing, or planarization, must account for variations in overall wafer flatness as well. During the fabrication process, for example, the wafers may become bowed or warped.
In process polishing equipment, therefore, requires the specialized ability to achieve global, uniformly planar wafer surfaces in spite of these topographical wafer defects and variations. Chemical-mechanical polishing has gained wide acceptance as an effective means of achieving the global wafer surface planarity required by advanced devices employing multilayer metalization.
FIG. 1
shows a partial cross section of a typical prior art chemical-mechanical polishing arrangement. A typical device includes a tooling head having a generally circular pressure plate or carrier platen
1
that supports a single substrate or wafer
3
. A carrier film
2
may be interposed between the carrier platen
1
and the wafer
3
to partially accommodate wafer thickness variations. The tooling head is equipped with means to provide a downward force, urging the wafer
3
against a polishing media
5
(typically a circular pad), onto which is fed a polishing fluid
7
. The polishing media is supported by the polishing platen
6
. The polishing fluid
7
may comprise a colloidal suspension of an abrasive and may also comprise of a chemically reactive solution. A containment ring
4
generally surrounds the wafer to prevent it from slipping off the carrier platen
1
during polishing.
Typically, movement of the wafer relative to the pad, in the presence of the chemically reactive and/or abrasive polishing fluid and under pressure imparted by the tooling head, imparts a combination of chemical and mechanical forces to the wafer
3
, the net effect of which is global planarization of the wafer surface. Generally, the polishing platen
6
is rotatable as is the carrier platen
1
. In a typical polishing apparatus, relative movement of the wafer relative to the pad is accomplished by rotating the polishing platen
6
, the carrier platen
1
, or both.
Because the manufacturing plant required to produce semiconductor devices is very costly, it is important that each piece of semiconductor process equipment installed in the fabrication line make economical use of the time required for its particular process and the physical space required for use. For this reason, there is constant pressure to improve total process throughput and reduce the amount of floorspace required for semiconductor process equipment.
In this regard, polishing machines used in the semiconductor device fabrication process are not optimized. Current chemical-mechanical polishing machines do not have the ability to deliver substantially uninterrupted polishing media and have difficulty in uniformly conditioning the polishing media for continued use after a certain amount of polishing has been performed.
Rotating platen machines typically install a circular polishing pad and use it until the pad fails to obtain acceptable results because the pad becomes worn or becomes glazed with impacted polishing fluid and polishing particulate. At that time it is required to interrupt the polishing process and change the polishing pad.
Some polishing machines have employed a conditioning device, such as a spinning head, to condition the pad. The purpose of such conditioning is to create and revitalize the structure on the polishing media that retains the slurry dispersion for the polish process. Conditioning also serves to liberate and remove material impacted into the pad in the course of polish processing. Specific applications of conditioning may serve to planarize the polishing pad as well as cut or form a desired pattern into the polishing surface. Such a pattern is useful, for example, to facilitate uniform slurry distribution over the pad.
In current machines, conditioning is generally performed in the same planar area as the processing area. Typically, when the platen is rotating, a smaller spinning head is moved across the radius of the platen. Because of the inherent surface velocity differentials associated with the spinning head and the rotating platen, it is very difficult to ensure that a constant relative velocity between the rotating platen and the spinning head was accomplished at every point during conditioning. Such a constant relative velocity is required to ensure equal and uniform conditioning.
In addition, conditioning defects are often created as a result of misalignment of the surface of the spinning head to the plane of the polishing media. Even when suitably aligned, once polishing begins the spinning head is subject to substantial and varying friction forces at the conditioning surface. These forces tend to adversely affect the alignment of the head causing an edge of the spinning head to dig into the pad. The inability to provide uniform, defect free conditioning of the polishing pad surface inevitably causes a corresponding degradation in the polish processing results. Furthermore, while these types of conditioning may extend the polishing pad life somewhat, it is still required to install a new pad at a higher than desired frequency.
Another source of concern for the creation of wafer defects as a result of the conditioning is in the advent of conditioning particle(s), or conditioning elements becoming liberated from the conditioning device used, wherein the liberated conditioning elements (i.e. diamond chip) can become imbedded in the polishing media. The imbedded conditioning elements are a primary source of scratch defects found in wafers in the course of process polishing. Given the appearance of wafer scratch defects, the process requires immediate shutdown for replacement of the polishing pad media.
Another area that has not been optimized on current polishing machines is the control and maintenance of polishing fluids. Control and contain
Barber John A.
Donohue Timothy J.
Hoshizaki Jon A.
Lee Lawrence
Meng Ching-Ling
Eley Timothy V.
Thomason Moser & Patterson
LandOfFree
Polishing media magazine for improved polishing does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Polishing media magazine for improved polishing, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Polishing media magazine for improved polishing will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2594003