Abrading – Abrading process – With tool treating or forming
Reexamination Certificate
2000-05-31
2002-06-25
Hail, III, Joseph J. (Department: 3723)
Abrading
Abrading process
With tool treating or forming
C451S041000, C451S285000, C451S910000
Reexamination Certificate
active
06409579
ABSTRACT:
TECHNICAL FIELD
The field of the present invention pertains to processes and apparatus related to chemical mechanical polishing operations for fabricating semiconductors and integrated circuits. More particularly, the present invention relates to the field of dispensing slurry on a polish pad and for conditioning a polish pad for chemical mechanical polishing operations.
BACKGROUND ART
Conventional integrated circuits (IC) are fashioned from miniature electrical devices such as resistors, diodes, and transistors. These miniature electrical devices are created by using deposition operations to create layers of material, by using photolithography to create patterns in the wafer, and by using chemical mechanical polishing (CMP) operations to polish away unwanted portions of the layers of material. In order to provide consistent and even layers, a need arises for a method and apparatus that can polish a wafer surface to be very flat.
CMP is the preferred method for planarizing a semiconductor wafer. In particular, CMP flattens out height differences between high spots and low spots on the wafer. This is accomplished via mechanical contact between the wafer and a moving polish pad that is saturated with an abrasive polish slurry. Polishing in this manner is the only technique that provides a smooth topography when examined on a millimeter scale. That is, the wafer is essentially flat when measured over the distance of a millimeter.
Prior art
FIG. 1A
is a plan view of a chemical mechanical polishing (CMP) machine
100
. Prior art
FIG. 1B
is an elevation view of CMP machine
100
. CMP machine
100
picks up a wafer to be polished with a carrier arm
101
and holds it against a rotating polish pad
102
. Polish pad
102
is made of a resilient material and is textured, often with multiple predetermined grooves
103
, to aid the polishing process. Polish pad
102
rotates on a platen, or turntable,
104
located beneath polish pad
102
, at a predetermined speed. A wafer
105
is held in place on polish pad
102
within a carrier ring
112
that is connected to a carrier
106
of carrier arm
101
. The front surface of wafer
105
rests against polish pad
102
. The back surface of wafer
105
is held against a surface of carrier
106
of carrier arm
101
. As polish pad
102
rotates in one direction
114
, e.g. a clockwise direction
114
, carrier
106
itself rotates wafer
105
at a predetermined rate. CMP machine
100
also includes a slurry dispense arm
107
extending across the radius of polish pad
102
. Slurry dispense arm
107
dispenses a flow of polish slurry onto polish pad
102
via port
132
. To improve dispersal of polish slurry over polish pad
102
, slurry dispense arm
107
disperses polish slurry while it traverses across the radius of polish pad
102
in direction
134
.
To aid in maintaining a stable removal rate, CMP machine
100
includes a conditioner assembly
120
. Conditioner assembly
120
includes a conditioner arm
108
, which extends across the radius of polish pad
102
. An end effector
109
is connected to conditioner arm
108
. End effector
109
includes an abrasive conditioning disk
110
that is used to roughen the surface of polish pad
102
. Conditioning disk
110
is rotated by conditioner arm
108
in the same direction as pad
102
, e.g. in a clockwise direction
130
, and is transitionally moved across the radius of polish pad
102
in direction
138
, such that conditioning disk
110
covers the radius of polish pad
102
. In so doing, conditioning disk
110
covers the surface area of polish pad
102
, as polish pad
102
rotates. The pad is conditioned by conditioning assembly
120
to help keep the pad profile as flat as possible. However, there is no guarantee that conditioner assembly
120
actually conditions the polish pad
102
precisely where the wafer contacted the polish pad. If there is a mismatch between the polishing operation, where wafer
105
contacted polish pad
102
, and the conditioning operation, where conditioning disk
110
contacts polish pad
102
, then the pad profile may become skewed. Similarly, if conditioning assembly
120
is biased to a region, it may result in uneven polishing because of the uneven conditioning of polish pad
102
. Furthermore, conditioning assembly
120
can be a source of defect particles. Consequently, a need arises for a method of conditioning a pad that will ensure a consistent and flat pad profile.
A polish pad with a roughened surface has an increased number of micro-pits and gouges in its surface that produces a faster removal rate of material from wafer
105
via increased slurry transfer to the surface of wafer
105
. The surface texture of the polish pad is created from conditioner assembly
120
, which is typically coated with diamonds. Without conditioning, the surface of polish pad
102
is smoothed during the polishing process and removal rate decreases dramatically. Conditioner assembly
120
re-roughens the surface of polish pad
102
, thereby keeping the grooves cleaned out, improving the transport of slurry, and improving the removal rate of material from the wafer.
As described above, the CMP process uses abrasive slurry on a polish pad. The polishing action of the slurry is comprised of an abrasive frictional component and a chemical component. The abrasive frictional component is due to the friction between the surface of the polish pad, the surface of the wafer, and the abrasive particles suspended in the slurry. The chemical component is due to the presence in the slurry of polishing agents that chemically interact with the material of the dielectric layer of wafer
105
. The chemical component of the slurry is used to soften the surface of the dielectric layer to be polished, while the frictional component removes material from the surface of wafer
105
.
As shown by prior art
FIGS. 1A and 1B
, the conventional method of dispensing slurry onto the polish pad uses a separate dedicated device, e.g. slurry dispense arm
107
, that has a control mechanism for moving across the pad to deliver polish slurry across the entire radius of polish pad
102
. This conventional method and apparatus proliferates the control mechanisms, and the complexity of the CMP machine. Consequently, a need arises for an apparatus and method of reducing the complexity of a slurry dispense mechanism for the polishing operation.
Conventional controls attempt to align slurry dispense arm
107
with the anticipated location of the wafer being polished. However, there is no guarantee that slurry dispense arm
107
will provide slurry material precisely where the wafer will contacted the polish pad. If there is a mismatch between the location of the slurry deposited on polish pad
102
, and the location of the wafer contacting polish pad
102
, nearly 270° later, then the pad profile and the polishing rate across wafer
105
may become uneven. Consequently, a collateral need arises in the CMP operation is to improve the uniformity of polish slurry dispensing.
Similarly, as shown by prior art
FIGS. 1A and 1B
, the conventional method of conditioning the polish pad uses a separate dedicated device, e.g. conditioner assembly
120
, that has a control mechanism for circular motion and for rotational motion across the polish pad. This conventional method and apparatus proliferates the control mechanisms and the size of a CMP machine. Consequently, a need arises for an apparatus and method of reducing the complexity of a conditioning mechanism for the polishing operation. A collateral need in the CMP operation is to improve the efficiency of pad conditioning.
In summary, a need arises for a method and apparatus that can create a very flat surface on the wafer. More specifically, a need arises for an apparatus and method of reducing the complexity of a slurry dispense mechanism for a CMP polishing operation. A collateral need arises in the CMP operation to improve the uniformity of polish slurry dispensing. Yet another need arises for an apparatus and method of reducing the complexity of a conditi
Liu Albert H.
White, II Nelson W.
Hail III Joseph J.
Koninklijke Philips Electronics , N.V.
Ojini Anthony
Zawilski Peter
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