Semiconductor device manufacturing: process – Chemical etching – Combined with the removal of material by nonchemical means
Reexamination Certificate
1999-11-17
2001-10-23
Powell, William A. (Department: 1765)
Semiconductor device manufacturing: process
Chemical etching
Combined with the removal of material by nonchemical means
C216S089000, C438S745000
Reexamination Certificate
active
06306768
ABSTRACT:
TECHNICAL FIELD
This invention relates to methods for planarizing microelectronic substrates; for example, microelectronic substrates having dielectric portions with apertures that support devices such as capacitors.
BACKGROUND
Mechanical and chemical-mechanical planarization processes (“CMP”) are used in the manufacturing of electronic devices for forming a flat surface on semiconductor wafers, field emission displays and many other microelectronic-device substrate assemblies. CMP processes generally remove material from a substrate assembly to create a highly planar surface at a precise elevation in the layers of material on the substrate assembly.
FIG. 1
schematically illustrates an existing web-format planarizing machine
10
for planarizing a substrate
12
. The planarizing machine
10
has a support table
14
with a top-panel
16
at a workstation where an operative portion (A) of a planarizing pad
40
is positioned. The top-panel
16
is generally a rigid plate to provide a flat, solid surface to which a particular section of the planarizing pad
40
may be secured during planarization.
The planarizing machine
10
also has a plurality of rollers to guide, position and hold the planarizing pad
40
over the top-panel
16
. The rollers include a supply roller
20
, first and second idler rollers
21
a
and
21
b
, first and second guide rollers
22
a
and
22
b
, and take-up roller
23
. The supply roller
20
carries an unused or pre-operative portion of the planarizing pad
40
, and the take-up roller
23
carries a used or post-operative portion of the planarizing pad
40
. Additionally, the first idler roller
21
a and the first guide roller
22
a
stretch the planarizing pad
40
over the top-panel
16
to hold the planarizing pad
40
stationary during operation. A motor (not shown) drives at least one of the supply roller
20
and the take-up roller
23
to sequentially advance the planarizing pad
40
across the top-panel
16
. Accordingly, clean pre-operative sections of the planarizing pad
40
may be quickly substituted for used sections to provide a consistent surface for planarizing and/or cleaning the substrate
12
.
The web-format planarizing machine
10
also has a carrier assembly
30
that controls and protects the substrate
12
during planarization. The carrier assembly
30
generally has a substrate holder
32
to pick up, hold and release the substrate
12
at appropriate stages of the planarizing process. Several nozzles
33
attached to the substrate holder
32
dispense a planarizing solution
44
onto a planarizing surface
42
of the planarizing pad
40
. The carrier assembly
30
also generally has a support gantry
34
carrying a drive assembly
35
that translates along the gantry
34
. The drive assembly
35
generally has an actuator
36
, a drive shaft
37
coupled to the actuator
36
, and an arm
38
projecting from the drive shaft
37
. The arm
38
carries the substrate holder
32
via a terminal shaft
39
such that the drive assembly
35
orbits the substrate holder
32
about an axis B-B (as indicated by arrow R
1
). The drive assembly
35
can also rotate the substrate holder
32
about its central axis C-C (as indicated by arrow R
2
).
The planarizing pad
40
and the planarizing solution
44
define a planarizing medium that mechanically and/or chemically-mechanically removes material from the surface of the substrate
12
. The planarizing pad
40
used in the web-format planarizing machine
10
is typically a fixed-abrasive planarizing pad in which abrasive particles are fixedly bonded to a suspension material. In fixed-abrasive applications, the planarizing solution is a “clean solution” without abrasive particles because the abrasive particles are fixedly distributed across the planarizing surface
42
of the planarizing pad
40
. In other applications, the planarizing pad
40
may be a non-abrasive pad without abrasive particles, composed of a polymeric material (e.g., polyurethane) or other suitable materials. The planarizing solutions
44
used with the non-abrasive planarizing pads are typically CMP slurries with abrasive particles and chemicals to remove material from a substrate. Typical abrasive particles include ILD 1300 fumed silica particles, available from Rodel, Inc. of Wilmington, Del. and having a mean cross-sectional dimension of 200 nanometers, or Klebosol 1508-50 colloidal particles, also available from Rodel, Inc. and having a mean cross-sectional dimension of fifty nanometers.
To planarize the substrate
12
with the planarizing machine
10
, the carrier assembly
30
presses the substrate
12
against the planarizing surface
42
of the planarizing pad
40
in the presence of the planarizing solution
44
. The drive assembly
35
then orbits the substrate holder
32
about the axis B-B and/or rotates the substrate holder
32
about the axis C-C to translate the substrate
12
across the planarizing surface
42
. As a result, the abrasive particles and/or the chemicals in the planarizing medium remove material from the surface of the substrate
12
.
The CMP processes should consistently and accurately produce a uniformly planar surface on the substrate assembly to enable precise fabrication of circuits and photo-patterns. During the fabrication of transistors, contacts, interconnects and other features, many substrate assemblies develop large “step heights” that create a highly topographic surface across the substrate assembly. Yet, as the density of integrated circuits increases, it is necessary to have a planar substrate surface at several intermediate processing stages because non-uniform substrate surfaces significantly increase the difficulty of forming sub-micron features. For example, it is difficult to accurately focus photo patterns to within tolerances approaching 0.1 micron on non-uniform substrate surfaces because sub-micron photolithographic equipment generally has a very limited depth of field. Thus, CMP processes are often used to transform a topographical substrate surface into a highly uniform, planar substrate surface.
During one conventional process, capacitors and other electrical components are formed in the microelectronic substrate
12
by first forming an aperture in the substrate
12
and then depositing successive layers of conductive and dielectric materials into the aperture. For example,
FIG. 2A
is a cross-sectional view of a portion of the substrate
12
shown in FIG.
1
. The substrate
12
includes a base dielectric material
50
having two capacitor apertures
51
. The walls of the capacitor apertures
51
are initially coated with a first conductive layer
60
that extends between the adjacent apertures. The substrate
12
is then planarized, using a process such as that discussed above with reference to
FIG. 1
, to remove intermediate portions
56
from between the capacitor apertures
51
. Accordingly, the remaining portions of the conductive layer
60
within each capacitor aperture
51
are electrically isolated from each other.
As shown in
FIG. 2B
, a layer of dielectric material
61
is deposited on the remaining portions of the conductive layer
60
and on the exposed portions of the substrate upper surface
54
. A second conductive layer
62
is deposited on the dielectric material
61
to form capacitors
70
. An insulating material
63
, such as borophosphate silicon glass (BPSG) is disposed on the second conductive layer
62
to fill the remaining space in the capacitor apertures
51
and electrically insulate the capacitors
70
from additional structures subsequently formed on the substrate
12
. After the capacitors
70
are formed, a conductive plug aperture
52
is etched into the substrate
12
and filled with a conductive material to provide a conductive path between layers of the substrate
12
.
One potential problem with the conventional method described above with reference to
FIGS. 1-2B
is that the base dielectric material
50
can crack during the planarization process. For example, the base dielectric material
50
typically includes an o
Micro)n Technology, Inc.
Perkins Coie LLP
Powell William A.
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