Abrading – Precision device or process - or with condition responsive... – By optical sensor
Reexamination Certificate
2001-08-30
2003-12-23
Hail, III, Joseph J. (Department: 3723)
Abrading
Precision device or process - or with condition responsive...
By optical sensor
C451S005000, C451S008000, C451S010000, C451S011000, C451S041000, C451S067000, C451S072000, C451S285000, C451S286000, C451S287000, C451S910000
Reexamination Certificate
active
06666749
ABSTRACT:
TECHNICAL FIELD
The present disclosure relates to chemical-mechanical planarizing machines and methods to maintain processing pads and other planarizing media.
BACKGROUND OF THE INVENTION
Mechanical and chemical-mechanical planarizing processes (collectively “CMP”) remove material from the surface of semiconductor wafers, field emission displays or other microelectronic workpieces in the production of microelectronic devices and other products.
FIG. 1
schematically illustrates a CMP machine
10
with a platen
20
, a carrier assembly
30
, and a planarizing pad
40
. The CMP machine
10
may also have an under-pad
25
attached to an upper surface
22
of the platen
20
and the lower surface of the planarizing pad
40
. A drive assembly
26
rotates the platen
20
(indicated by arrow F), or it reciprocates the platen
20
back and forth (indicated by arrow G). Since the planarizing pad
40
is attached to the under-pad
25
, the planarizing pad
40
moves with the platen
20
during planarization.
The carrier assembly
30
controls and protects the workpiece
12
during planarization. The carrier assembly
30
generally has a workpiece holder
32
to pick up, hold and release the workpiece
12
at appropriate stages of the planarizing process, or the workpiece
12
may be attached to a resilient pad
34
in the holder
32
. The holder
32
may be a free-floating wafer carrier, or an actuator assembly
36
may be coupled to the holder
32
to impart axial and/or rotational motion to the workpiece
12
(indicated by arrows H and I, respectively).
The planarizing pad
40
and a planarizing solution
44
on the pad
40
collectively define a planarizing medium that mechanically and/or chemically-mechanically removes material from the surface of the workpiece
12
. The planarizing pad
40
can be a soft pad or a hard pad. The planarizing pad
40
can also be a fixed-abrasive planarizing pad in which abrasive particles are fixedly bonded to a suspension material. In fixed-abrasive applications, the planarizing solution
44
is typically a non-abrasive “clean solution” without abrasive particles.
To planarize the workpiece
12
with the CMP machine
10
, the carrier assembly
30
presses the workpiece
12
face-downward against the polishing medium. More specifically, the carrier assembly
30
generally presses the workpiece
12
against the planarizing solution
44
on a planarizing surface
42
of the planarizing pad
40
, and the platen
20
and/or the carrier assembly
30
moves to rub the workpiece
12
against the planarizing surface
42
. As the workpiece
12
rubs against the planarizing surface
42
, material is removed from the face of the workpiece
12
.
In the highly competitive semiconductor industry, it is desirable to maximize the throughput of CMP processing by producing a planar surface on a workpiece as quickly as possible. The throughput of CMP processing is a function, at least in part, of the polishing rate of the workpiece assembly and the ability to accurately stop CMP processing at a desired endpoint. The polishing rate is a function of several factors, many of which may change during planarization. For example, the condition of the planarizing surface on the planarizing medium can affect the polishing rate. Typically, the polishing rate for a fixed-abrasive pad decreases after planarizing 3 to 10 workpieces. Changes in the polishing rate can also occur at other, unexpected times during planarization thereby reducing the accuracy of stopping a planarizing cycle at a desired endpoint and reducing the consistency of planarity of the workpieces. Therefore, it is generally desirable for CMP processes to provide (a) a uniform polishing rate across the face of a workpiece to enhance the planarity of the finished workpiece surface, and (b) a reasonably consistent polishing rate during a planarizing cycle to enhance the accuracy of determining the endpoint of a planarizing cycle.
CMP processes should consistently and accurately produce a uniformly planar surface on the workpiece to enable precise fabrication of circuits and photo-patterns. During the construction of transistors, contacts, interconnects and other features, many workpieces develop large “step heights” that create highly topographic surfaces. Such highly topographical surfaces can impair the accuracy of subsequent photolithographic procedures and other processes that are necessary for forming sub-micron features. For example, it is difficult to accurately focus photo patterns to within tolerances approaching 0.1 micron on topographic surfaces because sub-micron photolithographic equipment generally has a very limited depth of field. Thus, CMP processes are often used to transform a topographical surface into a highly uniform, planar surface at various stages of manufacturing microelectronic devices on a workpiece.
One factor affecting the uniformity of the workpiece surface is the condition of the planarizing pad. The planarizing surface of the pad can deteriorate after polishing a number of workpieces because waste matter from the workpieces, planarizing solution and/or the pad accumulates on the planarizing surface. The planarizing surface can also deteriorate because rubbing the workpiece against the pad alters the planarizing surface of the pad in a manner that may produce inconsistent results in uniformity. The wear characteristics on the pad, for example, depend upon the density pattern of the workpiece because different types of workpieces produce different wear characteristics on the planarizing surface of the pad.
The effects of workpiece wear on fixed-abrasive pads are particularly problematic. A high density workpiece typically has more topographical variations on the active side of the workpiece than a low density workpiece; therefore, a high density workpiece more aggressively wears the pad than a low density workpiece. As such, the polishing rate for a run of high density workpieces may not drop significantly after planarizing several workpieces. On the other hand, low density workpieces do not aggressively wear the pad surface, and thus they often “passivate” the planarizing surface of the pad. This can quickly reduce the polishing rate of low density workpieces. Therefore, different planarizing pads are generally used to planarize different types of workpieces and/or products in fixed-abrasive CMP. Changing the pad for each type of workpiece, however, is time-consuming and reduces the throughput of using fixed-abrasive pads.
One conventional technique to decrease the variability of CMP processing is “conditioning” the pad to restore the surface of the pad to a consistent state. Non-abrasive planarizing pads are conventionally conditioned with devices that rub an abrasive element on the planarizing surface. For example, one method for conditioning non-abrasive pads is to abrade the planarizing surface with a diamond end-effector. Another method to condition fixed-abrasive or non-abrasive pads involves agitating the pad-slurry-wafer interface using ultrasound to prevent the accumulation of particulate matter on the pad.
U.S. Pat. No. 6,083,085 issued to Lankford discloses a conditioning device for conditioning planarizing media. The conditioning device has a support assembly with a support member and a conditioning head attached to the support member. The support member may be a pivoting arm that carries the conditioning head over the planarizing medium. The conditioning head may have a non-contact conditioning element that transmits a form of non-contact energy to waste matter on the planarizing medium. For example, the non-contact conditioning element can be a mechanical-wave transmitter that transmits mechanical waves that act against waste matter on the planarizing pad to break the bonds between the planarizing medium and the waste matter. U.S. Pat. No. 5,895,550 issued to Andreas discloses a method and apparatus for chemical mechanical polishing that includes an acoustic energy source positioned to transmit acoustic energy into a polishing slurry to break up agglomerated particles
Hail III Joseph J.
McDonald Shantese
Micro)n Technology, Inc.
Perkins Coie LLP
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