U.S. patent application number 11/306913 was filed with the patent office on 2007-07-19 for multi-zone carrier head for chemical mechanical polishing and cmp method thereof.
Invention is credited to Kai-Hung Alex See, Yu-Hsiang Tseng, Jin Yu, Mei-Sheng Zhou, Wen-Zhan Zhou, Zheng Zou.
Application Number | 20070167110 11/306913 |
Document ID | / |
Family ID | 38263830 |
Filed Date | 2007-07-19 |
United States Patent
Application |
20070167110 |
Kind Code |
A1 |
Tseng; Yu-Hsiang ; et
al. |
July 19, 2007 |
MULTI-ZONE CARRIER HEAD FOR CHEMICAL MECHANICAL POLISHING AND CMP
METHOD THEREOF
Abstract
A multi-zone carrier head includes a housing; a retaining ring
secured to a lower edge of the housing; a backing plate having a
plurality of non-concentric pressure zones defined by a plurality
of isolated apertures on the backing plate; wherein the backing
plate has a wafer side and a non-wafer side, the wafer side facing
a backside of a wafer during a CMP operation; and a plurality of
pneumatic bladder for independently controlling pressure exerted in
the respective non-concentric pressure zones on the backside of the
wafer during the CMP operation.
Inventors: |
Tseng; Yu-Hsiang; (Ping-Tung
Hsien, TW) ; See; Kai-Hung Alex; (Singapore, SG)
; Zhou; Mei-Sheng; (Singapore, SG) ; Yu; Jin;
(Singapore, SG) ; Zou; Zheng; (Singapore, SG)
; Zhou; Wen-Zhan; (Singapore, SG) |
Correspondence
Address: |
NORTH AMERICA INTELLECTUAL PROPERTY CORPORATION
P.O. BOX 506
MERRIFIELD
VA
22116
US
|
Family ID: |
38263830 |
Appl. No.: |
11/306913 |
Filed: |
January 16, 2006 |
Current U.S.
Class: |
451/5 |
Current CPC
Class: |
B24B 37/30 20130101 |
Class at
Publication: |
451/005 |
International
Class: |
B24B 51/00 20060101
B24B051/00 |
Claims
1. A multi-zone carrier head for chemical mechanical polishing
(CMP), comprising: a housing; a retaining ring secured to a lower
edge of the housing; a backing plate having a plurality of
non-concentric pressure zones defined by a plurality of isolated
apertures on the backing plate; wherein the backing plate has a
wafer side and a non-wafer side, the wafer side facing a backside
of a wafer during a CMP operation; a pneumatic means for
independently controlling pressure exerted in the respective
non-concentric pressure zones on the backside of the wafer during
the CMP operation; and a pressure-sensing element disposed under
the pneumatic means in the respective non-concentric pressure
zones.
2. The multi-zone carrier head for CMP according to claim 1,
further comprising a backing film attached to the wafer side of the
backing plate, wherein the backing film is disposed between the
backing plate and the backside of the wafer during the CMP
operation.
3. The multi-zone carrier head for CMP according to claim 1,
wherein plurality of isolated apertures on the backing plate
include a central aperture and peripheral apertures surrounding the
central aperture.
4. The multi-zone carrier head for CMP according to claim 1,
wherein the multi-zone carrier head further comprises a diaphragm
seal.
5. The multi-zone carrier head for CMP according to claim 4,
wherein the diaphragm seal is an annular ring of a flexible
material.
6. (canceled)
7. The multi-zone carrier head for CMP according to claim 1,
wherein the pressure-sensing element includes piezo-materials,
piezo-crystals, piezo sensors or piezoelectric ceramic sensors.
8. The multi-zone carrier head for CMP according to claim 1,
wherein the pressure-sensing element is selected from the group
consisting of BaTiO3, AIN, ZnO, lead zirconium titanate, PZT
ceramic (PbZrTi), tantalum oxide (Ta205), and barium strontium
tantanite (BST).
9. The multi-zone carrier head for CMP according to claim 1,
wherein the pressure-sensing element detects topography of the
wafer during the CMP operation and transmits feedback signals to a
control unit.
10. A method for polishing a substrate, comprising: mounting a
substrate into a carrier head, the carrier head comprising a
pneumatic means controlled by a control unit for independently
controlling pressure exerted in respective non-concentric pressure
zones on backside of the substrate and a pressure-sensing element
under the pneumatic means in the respective non-concentric pressure
zones; respectively rotating the carrier head and a polishing pad
on which the substrate is resting; providing a down force on the
substrate; and polishing a material layer of the substrate
away.
11. (canceled)
12. The method of claim 10, wherein the pressure-sensing element
includes piezo-materials, piezo-crystals, piezo sensors or
piezoelectric ceramic sensors.
13. The method of claim 10, wherein the pressure-sensing element is
selected from the group consisting of BaTiO3, AIN, ZnO, lead
zirconium titanate, PZT ceramic (PbZrTi), tantalum oxide (Ta205),
and barium strontium tantanite (BST).
14. The method of claim 10, wherein the pressure-sensing element
detects topography of the substrate during a CMP operation and
transmits feedback signals to a control unit.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates generally to chemical
mechanical polishing of substrates and, more particularly, to a
multi-zone carrier head for chemical mechanical polishing.
[0003] 2. Description of the Prior Art
[0004] In the process of fabricating integrated circuits, it is
essential to form multi-level material layers and structures on a
wafer. However, the prior formations often leave the top surface
topography of an in-process wafer highly irregular. Such
irregularities cause problems when forming the next layer over a
previously formed integrated circuit structure. For example, when
printing a photolithographic pattern having small geometries over
previously formed layers, a very shallow depth of focus is
required. Therefore, there is a need to periodically planarize the
wafer surface.
[0005] One technique for planarizing the surface of a wafer is
chemical mechanical polishing (CMP). In CMP processing, a wafer is
placed face down on a rotating platen. The wafer, held in place by
a carrier or polishing head, independently rotates about its own
axis on the platen. Typically, the head is a floating polishing
head with a flexible membrane. On the surface of the platen is a
polishing pad over which there is dispensed a layer of polishing
slurry. The slurry chemistry is essential to proper polishing.
Typically, it consists of a colloidal solution of silica particles
in a carrier solution.
[0006] Conventional CMP suffers from some problems that need to be
accounted for during the process integration. When polishing a
wafer that has step features, only the top of the features touch
the polishing pad, concentrating the pressure on these contact
points. This increases the polishing rate above that of a blanket
wafer. In addition, it causes non-uniformity in the removal rate
across patterns of different densities due to variations in the
pressure distribution across the pattern. This pattern density
effect on removal rate can cause problems if there are both dense
pattern and very sparse pattern on the wafer surface.
SUMMARY OF THE INVENTION
[0007] In one aspect, the invention is directed to a multi-zone
carrier head for chemical mechanical polishing (CMP). The
multi-zone carrier head includes a housing; a retaining ring
secured to a lower edge of the housing; a backing plate having a
plurality of non-concentric pressure zones defined by a plurality
of isolated apertures on the backing plate; wherein the backing
plate has a wafer side and a non-wafer side, the wafer side facing
a backside of a wafer during a CMP operation; and a plurality of
pneumatic bladder for independently controlling pressure exerted in
the respective non-concentric pressure zones on the backside of the
wafer during the CMP operation.
[0008] In another aspect, the invention is directed to a method for
polishing a substrate or wafer. The method includes the following
steps:
[0009] (a) mounting a substrate into a carrier head, the carrier
head comprising a pneumatic means controlled by a control unit for
independently controlling pressure exerted in respective
non-concentric pressure zones on backside of the substrate;
[0010] (b) rotating the carrier head and a polishing pad on which
the substrate is resting;
[0011] (c) providing a down force on the substrate; and
[0012] (d) polishing a material layer of the substrate away.
[0013] These and other objectives of the present invention will no
doubt become obvious to those of ordinary skill in the art after
reading the following detailed description of the preferred
embodiment that is illustrated in the various figures and
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The accompany drawings are included to provide a further
understanding of the invention, and are incorporated in and
constitute a part of this specification. The drawings illustrate
embodiments of the invention and, together with the description,
serve to explain the principles of the invention. In the
drawings:
[0015] FIG. 1 is a diagram showing a table based CMP tool;
[0016] FIG. 2 is a schematic, cross-sectional diagram illustrating
the structure of a carrier head in accordance with one preferred
embodiment of this invention;
[0017] FIG. 3 illustrates a plane view of the backing plate
according to one preferred embodiment;
[0018] FIG. 4 illustrates a plane view of the backing plate
according to another preferred embodiment; and
[0019] FIG. 5 is a schematic, cross-sectional diagram illustrating
the structure of a carrier head in accordance with another
preferred embodiment of this invention.
DETAILED DESCRIPTION
[0020] FIG. 1 is a diagram showing a table based CMP tool 50. The
table based CMP tool 50 includes a carrier head 52, which holds a
wafer 54, and is attached to a translation arm. In addition, the
table based CMP tool 50 includes a polishing pad 56 that is
disposed above a polishing table 58, which is often referred to as
a polishing platen.
[0021] In operation, the carrier head 52 applies downward force to
the wafer 54, which contacts the polishing pad 56. Reactive force
is provided by the polishing table 58, which resists the downward
force applied by the carrier head 52. A polishing pad 56 is used in
conjunction with slurry to polish the wafer 54. Typically, the
polishing pad 56 comprises foamed polyurethane or a sheet of
polyurethane having a grooved surface. The polishing pad 56 is
wetted with polishing slurry having both an abrasive and other
polishing chemicals. In addition, the polishing table 58 is rotated
about its central axis 60, and the carrier head 52 is rotated about
its central axis 62.
[0022] FIG. 2 is a schematic, cross-sectional diagram illustrating
the structure of a carrier head in accordance with one preferred
embodiment of this invention. As shown in FIG. 2, the carrier head
52 generally includes a housing 150, a retaining ring 152, a
disk-shaped backing plate 154 and a backing film 156.
[0023] The housing 150 can be connected to a drive shaft (not
shown) to rotate therewith during polishing about an axis of
rotation 62, which is substantially perpendicular to the surface of
a polishing pad 56. The housing 150 may be generally circular in
shape to correspond to the circular configuration of the wafer to
be polished. Passages (not shown) may extend through the housing
150 for pneumatic control of the carrier head 52. O-ring may be
used to form airtight seals between the passages through the
housing 150 and passages through the drive shaft.
[0024] The wafer 54 is held in place on the carrier head 52 by the
retaining ring 152. The retaining ring 152 may be a generally
annular ring secured along a lower, outer edge of the housing 150.
The retaining ring 110 defines a pocket area for accommodating the
wafer 54. An inner surface of the retaining ring 152 engages the
wafer 54 to prevent it from escaping from beneath the carrier head
52.
[0025] The backing film 156 is attached to the backing plate 154
between the backing plate 154 and the wafer 54. The backing film
156 cushions the wafer 54 during the polishing and compensates for
slight flatness variations in the wafer 54 or backing plate 154.
The backing film 156 may be made of polymer materials and attached
to the backing plate 154 with a pressure sensitive adhesive, but
not limited thereto.
[0026] In addition, the carrier head 52 may includes a diaphragm
seal 158 that is generally an annular ring of a flexible material.
An outer edge of the diaphragm seal 158 is clamped between the
housing 150 and the retaining ring 152, and the inner edge of the
diaphragm seal 158 is secured to the backing plate 154 by, for
example, a clamp ring (not shown). The diaphragm seal 158 may be
formed of rubber, such as neoprene, an elastomeric-coated fabric,
such as NYLON.TM. or NOMEX.TM., plastic, or a composite material,
such as fiberglass.
[0027] The backing plate 154 may be a flat stainless steel disk
slightly larger than the wafer 54. The backing plate 154 presses
against the backside of the wafer 54 and transfers the polishing
force to the wafer during a CMP operation.
[0028] The backing plate 154 has a plurality of non-concentric
pressure zones defined by an isolated central aperture 162 that is
formed in a central location of the backing plate 154 and a
plurality of isolated peripheral apertures 164 surrounding the
central aperture 162.
[0029] The backing plate 154 has a wafer side and a non-wafer side,
the wafer side facing a backside of the wafer 54 during a CMP
operation. Preferably, the number of the non-concentric pressure
zones is equal to or larger than five.
[0030] FIG. 3 illustrates a plane view of the backing plate 154
according to one preferred embodiment. FIG. 4 illustrates a plane
view of the backing plate 154 according to another preferred
embodiment. In FIG. 3, there are six non-concentric pressure zones
distributed on the backing plate 154, wherein the central aperture
162 is surrounded by the peripheral apertures 164. The central
aperture 162 is circular, while the peripheral apertures 164 are
sector shaped.
[0031] In FIG. 4, there are nine non-concentric pressure zones
distributed on the backing plate 154, wherein the central aperture
162 is square or rectangular. However, it is understood that the
number of the non-concentric pressure zones provided by the backing
plate may exceed nine and the arrangement and distribution of the
non-concentric pressure zones depicted in FIGS. 3 and 4 are
exemplary.
[0032] Referring back to FIG. 2, the carrier head 52 further
comprises a plurality of pneumatic bladders 182 and 184 that are
provided within corresponding central aperture 162 and peripheral
apertures 164 for independently controlling the down force within
each of the non-concentric pressure zones on the back side of the
wafer 54. The inflation or deflation is accomplished by using the
respective passages that connects with air supply or pumps.
[0033] According to another preferred embodiment of this invention,
referring to FIG. 5, the carrier head 52 further comprises
pressure-sensing elements 192 and 194 provided in respective
non-concentric pressure zones. The pressure-sensing element 192 is
installed in the central aperture 162, while the pressure-sensing
elements 194 are installed in respective peripheral apertures
164.
[0034] The pressure-sensing elements 192 and 194 may be
piezo-materials, piezo-crystals, piezo sensors or piezoelectric
ceramic sensors. For example, the pressure-sensing elements 192 and
194 may comprise BaTiO.sub.3, AIN, ZnO, lead zirconium titanate
(PbZrTi) or PZT ceramic, tantalum oxide (Ta.sub.2O.sub.5), barium
strontium tantanite (BST) or the like.
[0035] It is one salient feature of the present invention that the
pressure-sensing elements 192 and 194 can detect the topography of
the wafer surface during a CMP operation and transmit feedback
signals to a control unit of the CMP tool. According to the
feedback signals, the control unit, for example, a computer, which
is capable of controlling the air supply or pumps, can alter, in
real time, the pressure exerted in each non-concentric pressure
zones by means of the pneumatic bladders 182 and 184, thereby
improving uniformity and better planarization.
[0036] Those skilled in the art will readily observe that numerous
modifications and alterations of the device and method may be made
while retaining the teachings of the invention. Accordingly, the
above disclosure should be construed as limited only by the metes
and bounds of the appended claims.
* * * * *