Carrier heads, planarizing machines and methods for...

Details Carrier heads, planarizing machines and methods for... Carrier heads, planarizing machines and methods for...

2001-03-16

2003-09-30

Utech, Benjamin L. (Department: 1765)

Etching a substrate: processes

Nongaseous phase etching of substrate

Using film of etchant between a stationary surface and a...

C451S288000, C451S388000, C451S398000, C134S025400, C156S345120, C156S345140

Reexamination Certificate

active

06627098

ABSTRACT:

TECHNICAL FIELD
The present invention relates to carrier heads and methods for forming planar surfaces on microelectronic-device substrate assemblies in mechanical or chemical-mechanical planarizing processes.
BACKGROUND OF THE INVENTION
Mechanical and chemical-mechanical planarizing processes (collectively “CMP”) are used in the manufacturing of microelectronic devices for forming flat surfaces on semiconductor wafers, field emission displays and other types of microelectronic-device substrate assemblies.
FIG. 1
schematically illustrates a portion of an existing planarizing machine
10
having a rotating platen
20
, a carrier assembly
30
and a polishing pad
50
. An under-pad
25
can be attached to an upper surface
22
of the platen
20
for supporting the polishing pad
50
. In many planarizing machines, a drive assembly
26
rotates (arrow A) and/or reciprocates (arrow B) the platen
20
to move the polishing pad
50
during planarization. In other planarizing machines, such as web-format planarizing machines, the platen
20
remains stationary during planarization and the carrier assembly
30
moves a substrate assembly
12
across the polishing pad
50
.
The carrier assembly
30
controls and protects the substrate assembly
12
during planarization. The carrier assembly
30
typically has a drive assembly, a driveshaft
31
coupled to the drive assembly, and a carrier head
33
coupled to the driveshaft
31
. The drive assembly typically rotates and/or translates the carrier head
33
to move the substrate assembly
12
across the polishing pad
50
in a linear, orbital and/or rotational motion.
The particular carrier head
33
illustrated in
FIG. 1
is manufactured by Applied Materials Corporation. This carrier head includes an external housing
34
, a backing plate
40
fixedly attached to the driveshaft
31
, and a bladder
46
attached to the backing plate
40
. The housing
34
has a support member
35
and a retaining ring
37
depending from the support member
35
. A smooth-walled portion of the driveshaft
31
is received in a hole
36
through the support member
35
so that the driveshaft
31
can rotate independently from the housing
34
.
The backing plate
40
of the carrier head
33
includes an annular rim
41
having an inner surface
42
extending around the perimeter of the rim
41
. The inner surface
42
is a straight, vertical wall extending upwardly from the rim
41
. The backing plate
40
also includes a disposable pad
43
adhered to the annular rim
41
. The disposable pad
43
is shaped to have a flat interior portion
44
and a curved perimeter portion
45
curving from the interior portion
44
to the rim
41
. The pad
43
is a thin, low-friction sheet separate from the backing plate
40
that prevents the bladder
46
from sticking to the backing plate
40
during planarization. The backing plate
40
is received in the housing
34
, and a number of inner tubes
49
a
and
49
b
support the housing
34
over the backing plate
40
. The backing plate
40
accordingly rotates directly with drive shaft
31
without necessarily rotating with or moving vertically with the housing
34
.
The bladder
46
is a thin, flexible membrane attached to the backside or the perimeter edge of the backing plate
40
. A fluid conduit
47
through the driveshaft
31
, the backing plate
40
and the pad
43
couples a fluid supply (not shown) with a cell
48
between the bladder
46
and the pad
43
. The fluid supply can drive fluid into the cell
48
to inflate the bladder
46
, or the fluid supply can withdraw fluid from the cell
48
to deflate the bladder
46
.
To planarize the substrate assembly
12
, the carrier head
33
retains the substrate assembly
12
on a planarizing surface
52
of the polishing pad
50
in the presence of a planarizing fluid
60
. The bladder
46
inflates to exert a desired downforce against the substrate assembly
12
, and the carrier head
33
moves and/or rotates the substrate assembly
12
. As the substrate assembly
12
moves across the planarizing surface
52
, abrasive particles and/or chemicals in either the polishing pad
50
or the planarizing solution
60
remove material from the surface of the substrate assembly
12
.
CMP processes must consistently and accurately produce a uniformly planar surface on the substrate assembly to enable precise fabrication of circuits and photo-patterns. One aspect of forming components on semiconductor or other microelectronic-device substrate assemblies is photo-patterning designs to within tolerances as small as approximately 0.1 &mgr;m. Many semiconductor fabrication processes, however, create highly topographic surfaces with large “step heights” that significantly increase the difficulty of forming sub-micron features or photo-patterns to within such small tolerances. Thus, CMP processes are often used to transform a topographical substrate surface into a highly uniform, planar substrate surface (e.g., a “blanket surface”).
In the competitive semiconductor industry, it is also desirable to maximize the throughput of CMP processing by producing a blanket substrate surface as quickly as possible without sacrificing the accuracy of the process. The throughput of CMP processing is a function of several factors, one of which is the ability to accurately form a flat, planar surface across as much surface area on the substrate assembly as possible. Another factor influencing the throughput of CMP processing is the ability to stop planarization at a desired endpoint in the substrate assembly. In a typical CMP process, the desired endpoint is reached when the surface of the substrate is a blanket surface and/or when enough material has been removed from the substrate assembly to form discrete components on the substrate assembly (e.g., shallow trench isolation areas, contacts, damascene lines, etc.). Accurately stopping CMP processing at a desired endpoint is important for maintaining a high throughput because an “under-planarized substrate assembly may need to be re-polished, or an “over-planarized” substrate assembly may be damaged. Thus, CMP processing should be consistent from one wafer to another to accurately form a blanket surface at the desired endpoint.
One drawback of the Applied Materials carrier head
33
shown in
FIG. 1
is that the low-friction pad
43
wears out and needs to be replaced. In a typical application, for example, vertical displacement of the substrate assembly
12
and the backing plate
40
causes the bladder
46
to periodically engage the perimeter of the pad
43
. The contact between the bladder
46
and the pad
43
wears down the perimeter surface of the pad
43
to a point at which the pad
43
must be replaced. Replacing the pad
43
, however, is time-consuming because the bladder
46
and the pad
43
must be removed from the backing plate
40
. Therefore, the Applied Materials carrier head
33
illustrated in
FIG. 1
is subject to downtime that reduces the throughput of CMP processing.
Another drawback of the carrier head
33
is that it may produce inconsistent, non-planar surface features at the edge of a substrate assembly. The planarity of the substrate assembly is a function of, at least in part, the pressure exerted on the substrate assembly by the bladder
46
. The contour of the perimeter region
45
of the low-friction pad
43
may affect the force exerted on the perimeter of the substrate assembly
12
. For example, because the substrate assembly
12
may press the bladder
46
against the perimeter region
45
of the pad
43
during planarization, the contour of the perimeter region
45
can directly affect the force exerted against the perimeter of the substrate assembly
12
. The shape of the perimeter region
45
of the pad
43
, however, may be inconsistent over the life of a single pad
43
or from one pad
43
to another. One reason that the shape of the pad
43
may change is because the perimeter region
45
of the pad
43
compresses after a period of use. Moreover, and even more problematic, the shape of the perimeter r

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