Information
-
Patent Grant
-
6749491
-
Patent Number
6,749,491
-
Date Filed
Wednesday, December 26, 200122 years ago
-
Date Issued
Tuesday, June 15, 200420 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Hail, III; Joseph J.
- Ojini; Anthony
Agents
-
CPC
-
US Classifications
Field of Search
US
- 451 5
- 451 41
- 451 297
- 451 296
- 451 311
- 451 499
-
International Classifications
-
Abstract
An apparatus for reducing non-uniform stretch of a belt used in the CMP system is disclosed. The belt that may be used with the apparatus extends between a first roller and a second roller to define a belt loop with an inner surface and an outer surface to be used for CMP. The apparatus includes a compensating roller that has a first end and a second end where the first end and second end extends a width of the belt. The first end and the second end have a first diameter. The center of the roller has a second diameter that is less than the first diameter. The compensating roller has a symmetrically tapered shape that extends between each of the first end and second end to the center. The compensating roller is positioned inside of the belt loop, and is applied to the inner surface of the belt loop to reduce non-uniform stretch of the belt.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to chemical mechanical planarization (CMP) techniques and, more particularly, to the efficient, cost effective, and improved CMP operations.
2. Description of the Related Art
In the fabrication of semiconductor devices, there is a need to perform chemical mechanical planarization (CMP) operations. Typically, integrated circuit devices are in the form of multi-level structures. At the substrate level, transistor devices having diffusion regions are formed. In subsequent levels, interconnect metallization lines are patterned and electrically connected to the transistor devices to define the desired functional device. As is well known, patterned conductive layers are insulated from other conductive layers by dielectric materials, such as silicon dioxide. As more metallization levels and associated dielectric layers are formed, the need to planarize the dielectric material grows. Without planarization, fabrication of further metallization layers becomes substantially more difficult due to the variations in the surface topography. In other applications, metallization line patterns are formed in the dielectric material, and then, metal CMP operations are performed to remove excess metallization.
A chemical mechanical planarization (CMP) system is typically utilized to polish a wafer as described above. A CMP system typically includes system components for handling and polishing the surface of a wafer. Such components can be, for example, an orbital polishing pad, or a linear belt polishing pad. The pad itself is typically made of a polyurethane material or polyurethane in conjunction with other materials such as, for example a stainless steel belt. In operation, the belt pad is put in motion and then a slurry material is applied and spread over the surface of the belt pad. Once the belt pad having slurry on it is moving at a desired rate, the wafer is lowered onto the surface of the belt pad. In this manner, wafer surface that is desired to be planarized is substantially smoothed, much like sandpaper may be used to sand wood. The wafer may then be cleaned in a wafer cleaning system.
FIG. 1A
shows a linear polishing apparatus
10
which is typically utilized in a CMP system. The linear polishing apparatus
10
polishes away materials on a surface of a semiconductor wafer
16
. The material being removed may be a substrate material of the wafer
16
or one or more layers formed on the wafer
16
. Such a layer typically includes one or more of any type of material formed or present during a CMP process such as, for example, dielectric materials, silicon nitride, metals (e.g., aluminum or copper), metal alloys, semiconductor materials, etc. Typically, CMP may be utilized to polish the one or more of the layers on the wafer
16
to planarize a surface layer of the wafer
16
.
The linear polishing apparatus
10
utilizes a polishing belt
12
in the prior art, which moves linearly in respect to the surface of the wafer
16
. The belt
12
is a continuous belt which is cycled by rollers (or spindles)
20
. The rollers are typically driven by a motor so that the rotational motion of the rollers
20
causes the polishing belt
12
to be driven in a motion
22
, which is linear with respect to the wafer
16
. The wafer
16
is held by a wafer carrier
18
. The wafer
16
is typically held in position by mechanical retaining ring and/or by vacuum. The wafer carrier positions the wafer atop the polishing belt
12
so that the surface of the wafer
16
comes in contact with a polishing surface of the polishing belt
12
.
FIG. 1B
shows a side view of the linear polishing apparatus
10
. As discussed above in reference to
FIG. 1A
, the wafer carrier
18
holds the wafer
16
in position over the polishing belt
12
. The polishing belt
12
is a continuous belt typically made up of a polymer material such as, for example, the IC 1000 made by Rodel, Inc. layered upon a supporting layer. The support layer is generally made from a firm material such as stainless steel. The polishing belt
12
is rotated by the rollers
20
which drives the polishing belt in the linear motion
22
with respect to the wafer
16
. In one example, an air bearing platen
24
supports a section of the polishing belt under the region where the wafer
16
is applied. The platen
24
can then be used to apply air against the under surface of the supporting layer. The applied air thus forms an controllable air bearing that assists in controlling the pressure at which the polishing belt
12
is applied against the surface of the wafer
16
.
Unfortunately, in typical CMP systems, when a circular object such as a wafer, for example is pressed down upon a surface, which is rectangularly shaped such as the stretched polishing pad
12
, uneven stretching of the pad surface may occur which is akin to a ripple effect. This is due to uneven nonlinear forces acting on the rectangular surface. A central portion is stretched and the edges of the rectangular surface is not stretched so the sides of the rectangular surface are up. The air bearing platen may be utilized to try to smooth the ripple effects and reduce the uneven stretching by applying higher air pressure to the polishing pad, but this results in significant increase in air consumption and still does not result complete elimination of the ripple effects, especially in the wafer edge area.
FIG. 1C
illustrates the ripple effect in a static environment where a wafer
16
is pressed against a linear polishing pad
12
. A loaded wafer, pressing over the elastic surface of the polishing pad causes a transient pad deformation zone near a wafer edge, which, being accompanied with the wafer relative tangential motion, creates a quickly attenuating longitudinal-transversal pad deformation wave. This results in re-distribution of pad-wafer contact force, affecting the removal rate and resulting in the edge effect. The forces causing the removal rate variations are shown by force arrows
26
and
28
. Removal variations of up to 50% from the average may be observed due to the edge effects.
Linear belt CMP technology as described in
FIGS. 1A and 1B
has a reasonably flexible and stretchable polishing surface. The air bearing pad support utilized in the linear belt CMP provides a capability for manipulation of the pad shape and the contact force distribution enabling the minimizing of the edge effects up to 2 mm of edge exclusion. Unfortunately, one of the significant disadvantages of the air bearing is the circular symmetry of both upper surface and air providing orifices , which leads to high air consumption. During a CMP process, when the wafer
16
is pushed onto the polishing pad
12
, the pad
12
deforms where a plurality of ripples
24
are formed. The ripples
24
are portions of the polishing pad
12
which moves up from its previous position due to the pressure applied by the wafer. The portions of the polishing pad
12
that are moved up exerts greater polishing force on the wafer
16
. The effects of the ripples
24
at the edge of the wafer are especially pronounced resulting in an edge effect (removal variations at the wafer edge) where edge polishing rates are significantly higher than polishing rates at the center of the wafer
16
.
FIG. 1D
shows polishing effects of the ripples that may be formed when the non-rotating (static) wafer
14
is pressed down onto the polishing pad
12
. Therefore, because of the aforementioned ripple effect, certain portions of the wafer as shown by areas
32
are polished more than the remaining areas of the wafer
16
.
FIG. 1E
shows polishing effects of the ripples when an air bearing platen is utilized underneath a polishing pad. In this example, an air bearing platen blowing air underneath a center portion of the polishing pad pushes up on the polishing pad where a center portion of the wafer is typically polished. The ripples are therefore reduced by the air pressure and wafer polishing in the wafer center is not as pronounced as shown in FIG.
1
D. Therefore, less portions of the wafer
14
have uneven polishing. Unfortunately, usage of typical air bearing platen do not enable correction of excessive polishing in a plurality of areas
40
as shown in FIG.
1
E.
As a result, because of the rectangular shape of a typical linear polishing belt and its interaction with a circular distortion from the air bearing creates a non-linear pad stretching field resulting in surface rippling which finally results in uneven polishing of the wafer due to uneven polishing pressure applied by different portions of the polishing pad.
Therefore, there is a need for a method and an apparatus that overcomes the problems of the prior art by having an apparatus that may be utilized to correct stress distribution in a polishing pad so polishing pressure applied by the polishing pad to the wafer is consistent through different sections of the wafer. Such an apparatus additionally stretch the under-stretced belt sections to enable more consistent and effective polishing in a CMP process without requiring large air consumption.
SUMMARY OF THE INVENTION
Broadly speaking, the present invention fills these needs by providing an improved method and apparatus for reducing non-uniform stretch resulting in the evening of the polishing pressure across a wafer by using a profiled roller to manage the polishing forces that a linear polishing belt applies to the wafer during chemical mechanical planarization (CMP) process. The present invention utilizes a profiled roller or a plurality of smaller rollers manipulating the stretch distribution across the polishing belt to compensate for the stretch variations and suppress the rippling effect yielding in a more robust process window and reduced air consumption. It should be appreciated that the present invention can be implemented in numerous ways, including as a process, an apparatus, a system, a device or a method. Several inventive embodiments of the present invention are described below.
In one embodiment, an apparatus for reducing non-uniform stretch of a belt used in the CMP system is disclosed. The belt that may be used with the apparatus extends between a first roller and a second roller to define a belt loop with an inner surface and an outer surface to be used for CMP. The apparatus includes a compensating roller that has a first end and a second end where the first end and second end extends a width of the belt. The first end and the second end have a first diameter. The center of the roller has a second diameter that is less than the first diameter. The compensating roller has a symmetrically tapered shape that extends between each of the first end and second end to the center. The compensating roller is positioned inside of the belt loop, and is applied to the inner surface of the belt loop to reduce non-uniform stretch of the belt.
In another embodiment, an apparatus for reducing non-uniform stretch of a belt used in the CMP system is disclosed. The belt that may be used with the apparatus extends between a first roller and a second roller to define a belt loop with an inner surface and an outer surface to be used for CMP. The apparatus includes a compensating roller that has a first end and a second end. The first end and second end extends the width of the belt. The first end and the second end have a first diameter. The center of the roller has a second diameter that is less than the first diameter. The compensating roller has a symmetrically tapered shape that extends between each of the first end and second end to the center. The apparatus also includes a force applicator coupled to the compensating roller. The force applicator supplies a pressing motion to the compensating roller. The apparatus further includes a system force controller in communication with the force applicator where the system force controller manages an amount of force utilized by the force applicator. The compensating roller is positioned inside of the belt loop, and is configured to be applied to the inner surface of the belt loop so as to reduce non-uniform stretch of the belt.
In yet another embodiment, an apparatus for reducing non-uniform stretch of a belt used in the CMP system is disclosed. The belt that may be used with the apparatus extends between a first roller and a second roller to define a belt loop with an inner surface and an outer surface to be used for CMP. The apparatus includes a first compensating roller positioned inside of the belt loop where the first compensating roller is applied to the inner surface of the belt loop so as to press against a first edge of the belt. The apparatus also includes a second compensating roller positioned inside of the belt loop. The second compensating roller is applied to the inner surface of the belt loop so as to press against a second edge of the belt. The application of the first compensating roller and the second compensating roller to the inner surface of the belt loop reduces non-uniform stretch of the belt.
The advantages of the present invention are numerous. Most notably, by utilizing a CMP system where a profiled roller applies selective force, pressure may be applied to selective areas of a polishing pad to relieve non-uniform stretch and uneven tension across the polishing pad. Therefore, the present invention may normalize planarization polishing pressure across the polishing pad without the need of applying large amounts of air through an air bearing platen. In contrast to the prior art, polishing pressures may be made more consistent in all areas of the wafer by applying force to the edges of the polishing pad to correct the stress distribution of the polishing pad. In addition, air consumption may be optimized with the present invention because an air bearing platen does not have to apply as much as air to even the tension across the polishing pad.
Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be readily understood by the following detailed description in conjunction with the accompanying drawings. To facilitate this description, like reference numerals designate like structural elements.
FIG. 1A
shows a linear polishing apparatus which is typically utilized in a CMP system.
FIG. 1B
shows a side view of the linear polishing apparatus.
FIG. 1C
illustrates the ripple effect in a static environment where a wafer is pressed against a linear polishing pad.
FIG. 1D
shows polishing effects of the ripples that may be formed when the wafer is pressed down onto the polishing pad.
FIG. 1E
shows polishing effects of the ripples when an air bearing platen is utilized underneath a polishing pad.
FIG. 2
shows a CMP system according to one embodiment of the present invention.
FIG. 3A
illustrates a tension compensating apparatus in accordance with one embodiment of the present invention.
FIG. 3B
illustrates a tension compensating apparatus in accordance with one embodiment of the present invention.
FIG. 4
shows a tension compensating apparatus that utilizes two separate rollers in accordance with one embodiment of the present invention.
FIG. 5
shows a tension compensating apparatus that utilizes a plurality of force transmitters in accordance with one embodiment of the present invention.
FIG. 6
shows a graph illustrating the polishing rates of a CMP system using a tension compensating apparatus in accordance with one embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A method and apparatus for correcting the stress distribution of the polishing belt during chemical mechanical planarization (CMP) is provided. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be understood, however, by one of ordinary skill in the art, that the present invention may be practiced without some or all of these specific details. In other instances, well known process operations have not been described in detail in order not to unnecessarily obscure the present invention.
In general terms, the present invention is directed toward utilizing force applying apparatuses to generate displacement and pressure on certain portions of a polishing pad utilized in CMP operations to reduce non-uniform stretch and correct uneven stress distribution across the pad. In preferable embodiments, the method and apparatus involves utilizing a roller or a plurality of rollers to displace and in this way to increase pressure on the under-stretched edges along the width of the polishing belt which significantly reduces rippling of the polishing pad during CMP operations. It should be understood that the polishing belt can include any number of layers, including a single pad material (e.g., polymeric polishing layer), a supported pad material (e.g., a polymeric polishing pad supported by a stainless steel layer), or multi-layer pad materials with cushioning layers (e.g. a polymeric polishing pad over a cushioning layer that is in turn supported by a stainless steel layer), etc. Therefore, the polishing pressure on wafers being processed is more consistent thereby enabling the outer portions of the wafer away from the center to be polished at a substantially the same rate as the center of the wafer.
It should be understood that the present invention may be utilized to correct stress distribution on any type of polishing mechanism such as, for example, a linear polishing CMP apparatus. The present invention may also be utilized to optimize wafer polishing operations involving any size or types of wafers such as, for example, 200 mm semiconductor wafers, 300 mm semiconductor wafers, etc. The present invention therefore can enable optimized, more efficient, and more consistent wafer polishing operations in numerous types of CMP processing systems.
FIG. 2
shows a CMP system
100
according to one embodiment of the present invention. A polishing head
106
may be used to secure and hold the wafer
108
in place during wafer polishing operations. A polishing belt
104
forms a continuous belt loop around rollers
112
a
and
112
b
. The polishing belt
104
, in one embodiment, is a belt type polishing belt utilized in linear CMP systems. The polishing belt
104
is generally rotated in a direction indicated by a direction
110
at a speed of about 400 feet per minute by a first roller
112
a
and a second roller
112
b
, although this speed may vary depending upon the specific CMP operation. As the polishing belt
104
rotates, polishing slurry may be applied and spread over the surface of the polishing belt
104
. The polishing head
106
may then be used to lower the wafer
108
onto the surface of the rotating polishing belt
104
. A platen
116
may support the polishing belt
104
during the polishing process. The platen
116
may utilize any type of bearing such as a gas bearing. Fluid pressure from a fluid source
114
is inputted into the platen
116
by way of a plurality of output holes may be utilized to push up on the polishing belt
104
to control the polishing belt profile. In this manner, the surface of the wafer
108
that is desired to be planarized is substantially smoothed in an even manner.
In some cases, the CMP operation is used to planarize materials such as copper (or other metals), and in other cases, it may be used to remove layers of dielectric or combinations of dielectric and copper. The rate of planarization may be changed by adjusting the polishing pressure. The polishing rate is generally proportional to the amount of polishing pressure applied to the polishing belt against a platen
116
. Although in a preferable embodiment, the platen
116
uses air as a bearing, it should be understood that any other type of fluid may be utilized as the bearing between the platen
116
and the polishing belt
104
. After the desired amount of material is removed from the surface of the wafer
108
, the polishing head
106
may be used to raise the wafer
108
off of the polishing belt
104
. The wafer
108
is then ready to proceed to a wafer cleaning system.
The CMP system
100
includes a tension compensating apparatus
102
that may be placed in any location in the CMP system as long as a profiled roller or a plurality of force applicators (as discussed in reference to
FIGS. 3
,
4
, and
5
below) may be applied to the polishing belt
104
without adversely affecting operations of other parts of the CMP system
100
. The tension compensating apparatus
102
may also be incorporated into other structures within the CMP system
100
. In one embodiment, the tension compensating apparatus
102
is located in a bottom portion of the CMP system
100
below where the platen
116
is located. The configuration of the tension compensating apparatus
102
is discussed further detail in reference to
FIGS. 3-5
.
It should be appreciated that the tension compensating apparatus
102
may apply pressure to any portion of the polishing belt
104
as long as tension across the width of the polishing belt
104
may be made more consistent. In one embodiment, by applying pressure to a first edge
104
a
and a second edge
104
b
along the width of the polishing belt
104
, tension along different sections of the polishing belt
104
may be managed more effectively to enable more efficient and consistent polishing for different sections of the wafer. Pressure applied to the edges
104
a
and
104
b
enables significant reduction of the “ripple” effect that occurs when a rectangular sheet applies pressure to a circular object. This results in optimized wafer polishing due to greater consistency of polishing rates across the wafer as further discussed in reference to FIG.
6
.
FIG. 3A
illustrates a tension compensating apparatus
102
in accordance with one embodiment of the present invention. In this figure, the tension compensating apparatus
102
is shown from a front view (i.e., the line of sight is the axis in the direction of belt travel). In this embodiment, the tension compensating apparatus
102
includes a system force controller
160
that is connected to force applicators
162
a
and
162
b
. The force applicators
162
a
and
162
b
are connected to a spindle
164
which is coupled to a profiled roller
168
. A close-up view
105
of the interface between the profiled roller
168
and the polishing belt
104
is discussed in reference to FIG.
3
B.
The system force controller
160
may determine how much downward pressure, as shown by directions
172
a
and
172
b
, the force applicators
162
a
and
162
b
may apply to the profiled roller
168
which in turn can apply selective pressure to edges
104
a
and
104
b
of the polishing belt
104
. In one embodiment, the system force controller
160
may be a manual force controlling device. In another embodiment, the system force controller
160
may be an automatically operated device utilizing any type of logic that can monitor pressure applied to the polishing belt and that can manage the force applicators
162
a
and
162
b
to supply a force pushing the profiled roller
168
against the belt
104
. It should be understood that profiled roller
168
may also be known as a compensating roller. In this embodiment, by a feedback loop, the tension compensating apparatus
102
may apply force to certain areas of the polishing belt
104
to relieve any uneven tension in the polishing belt. It should be appreciated that the force applicators
162
a
and
162
b
may apply force to the profiled roller
168
by use of any type of force producing device such as, for example, hydraulic actuated pistons, air bladders, piezoelectric, magnetic acuators, etc. controlled in any type of manner. The profiled roller
168
may rotate in a direction
170
which moves in the same direction as the direction of the rotating rollers
112
a
and
112
b
as shown in FIG.
2
. The profiled roller
168
is configured so the ends of the roller
168
apply pressure to edges
104
a
and
104
b
of an inner surface
104
c
of the polishing belt
104
. An outer surface
104
d
is used for polishing purposes. By applying pressure to the edges
104
a
and
104
b
of the polishing belt
104
, the stress distribution through the polishing belt
104
may be made more consistent. As can be seen, a multitude of configurations may be utilized to enable the desired effects of equalized polishing belt tension.
Typically, without use of the tension compensating apparatus
102
, the polishing belt
104
may have tension irregularities. With use of the profiled roller
168
, the edges
104
a
and
104
b
of the polishing belt
104
may stretch the polishing belt from the edges which may even out the stress distribution when the wafer
108
is applied to a surface of the polishing belt
104
. It should be understood that the profiled roller may be configured in any way where pressure can applied to the edges
104
a
and
104
b
of the polishing belt
104
. In one embodiment, the profiled roller
168
has a first end
168
a
and a second end
168
b
which extend along the width of the polishing belt
104
. The ends
168
a
and
168
b
have a same diameter that is larger than a diameter of the center portion
168
c
of the roller
168
. In such an embodiment, the profiled roller
168
has a symmetrically tapered shape extending between each of the first end
168
a
and second end
168
b
to the center
168
c
. Therefore, the middle portion of the profiled roller
168
does not contact the polishing belt
104
. It should be appreciated that the profiled roller
168
may be any dimension which would enable it to apply pressure to the edges
104
a
and
104
b
of the polishing belt
104
. It should also be understood that the profiled roller
168
may be made from any material that may be strong enough and corrosion resistible such as, for example, hard rubber material, polyurethane material, stainless steel, ceramics, and even polymers, to apply correct pressure to the polishing pad
104
so non-uniform tension may be reduced. In another embodiment, the roller
168
may be a “barbell” shape where two are attached by a spindle. Again, the disk section touches the polishing belt
104
but the spindle section does not. The shape and position of the profiled roller
168
may be adjusted to optimize the removal rate profile and air consumption.
FIG. 3B
shows a close-up view
105
of the interface between the profiled roller
168
and the polishing pad
104
in accordance with one embodiment of the present invention. In this embodiment, the profiled roller
168
is used to press down on the the edge
104
b
of the polishing belt
104
. When the edge
104
b
is pressed down, the polishing pad
104
becomes stretched into position
104
′. Once the polishing pad
104
reaches the position
104
′, non-uniform stretch of the polishing belt
104
is reduced. As discussed in reference to
FIG. 6
, the reduction in non-uniform stretch results in more consistent wafer polishing.
FIG. 4
shows a tension compensating apparatus
102
′ that utilizes two separate rollers in accordance with one embodiment of the present invention. The view perspective of
FIG. 4
is the same as described in FIG.
3
. In this embodiment, the tension compensating apparatus
102
′ includes the system force controller
160
which controls force applicators
162
a
′ and
162
b
′ which are coupled to rollers
182
a
and
182
b
respectively. The force applicators
162
a
′ and
162
b
′ may apply different amounts of force to the rollers
182
a
and
182
b
respectively so differing amounts of force may be applied to two different locations of the polishing belt
104
depending on the requirements or adjustments to polishing desired. In one embodiment, the rollers
182
a
and
182
b
are configured to apply force to the edges
104
a
and
104
b
on the inner surface
104
of the polishing belt
104
. Application of force to edges
104
a
and
104
b
can reduce non-uniform stretch (i.e. reduce the rippling effects) of the polishing belt
104
during CMP operations and therefore increase wafer polishing consistency.
FIG. 5
shows a tension compensating apparatus
102
″ that utilizes a plurality of force transmitters
204
in accordance with one embodiment of the present invention. In this embodiment, the tension compensating apparatus
102
″ includes a system force controller
160
that connects and manages a force applicator
202
. The force applicator
202
is coupled to the plurality of force transmitters
204
. The plurality of force transmitters
204
are configured to apply pressure to the inner surface
104
c
of the polishing pad
104
. It should be understood that the plurality of force transmitters
204
may include any number of individual force transmitters. In one embodiment, the plurality of force transmitters
204
are a plurality of air bearing generators. In this embodiment, individual ones of the plurality of air bearing generators are controlled separately by the system force controller through the force applicator
202
thereby enabling different forces to be applied to different portions of the polishing belt
104
by the plurality of air bearing generators. In this embodiment, air may be introduced to the plurality of force transmitters
204
by the force applicator
202
. Each of the plurality of air bearing generators may have a plurality of air holes
204
a
. Therefore, by air injection through the plurality force transmitters
204
, small areas of air bearings may be created by the air flows from the air bearing generators. The air bearings can then push on the inner surface
104
c
of the polishing belt
104
to reduce non-uniform stretch of the polishing belt
104
. By controlling which of the plurality of force transmitters
204
outputs air, pressure may be generated against various sections of the polishing belt
104
. Such flexibility can enable a wide range of polishing belt tension adjustments to adjust for polishing rate variances in different parts of the wafer.
In addition to utilizing air to create pressure on specific parts of the polishing belt
104
, in one embodiment, the plurality of force transmitters can also be mechanically moved up and down to generate pressure on the polishing belt
104
. In yet another embodiment, the plurality of force transmitters may be a plurality of rollers. Each of the plurality of rollers may be similar in structure and functionality to ones as described in reference to FIG.
4
.
FIG. 6
shows a graph
300
illustrating the polishing rates of a CMP system using a tension compensating apparatus
102
in accordance with one embodiment of the present invention. The graph
300
shows a removal rate on the y-axis and a measurement location (as shown as distance from a center of a wafer) on the x-axis. A line
304
shows the relationship between wafer location and polishing rate for a wafer polished using the tension compensating apparatus
102
of the present invention. A line
302
shows polishing rates for a wafer polished by a prior art CMP system. As polishing rates from the center of the wafer (as shown by 0 on the measurement location axis) to the edge of the wafer (as shown by −100 and 100 on the measurement location axis) are measured, the variations in the removal rate (i.e. polishing rate) of the prior art CMP system are much greater than the variations in removal rate of the CMP system with the force application system of the present invention. The present invention is especially effective in reducing polishing variation near the edge of the wafer.
While this invention has been described in terms of several preferred embodiments, it will be appreciated that those skilled in the art upon reading the preceding specifications and studying the drawings will realize various alterations, additions, permutations and equivalents thereof. It is therefore intended that the present invention includes all such alterations, additions, permutations, and equivalents as fall within the true spirit and scope of the invention.
Claims
- 1. In a chemical mechanical planarization (CMP) system, an apparatus for reducing non-uniform stretch of a belt used in the CMP system, the belt extending between a first roller and a second roller to define a belt loop to be used for CMP, the belt loop having an inner surface and an outer surface, the apparatus comprising:a compensating roller having a first end and a second end, the first end and second end extending a width of the belt, the first end and the second end having a first diameter and a center of the roller having a second diameter that is less than the first diameter, the compensating roller having a symmetrically tapered shape extending between each of the first end and second end to the center; wherein the compensating roller is positioned inside of the belt loop, and is configured to be applied to the inner surface of the belt loop so as to reduce non-uniform stretch of the belt.
- 2. In a chemical mechanical planarization (CMP) system, an apparatus for reducing non-uniform stretch of a belt used in the CMP system as recited in claim 1, wherein the belt is a single layer polymeric polishing pad.
- 3. In a chemical mechanical planarization (CMP) system, an apparatus for reducing non-uniform stretch of a belt used in the CMP system as recited in claim 1, wherein the belt is a supported belt with polymeric polishing layer over a stainless steel layer.
- 4. In a chemical mechanical planarization (CMP) system, an apparatus for reducing non-uniform stretch of a belt used in the CMP system as recited in claim 1, wherein the belt is a multilayer belt including a polishing pad, a cushioning layer, and a stainless steel layer.
- 5. In a chemical mechanical planarization (CMP) system, an apparatus for reducing non-uniform stretch of a belt used in the CMP system as recited in claim 1, wherein the compensating roller is configured to apply pressure to a first edge and a second edge of the belt.
- 6. In a chemical mechanical planarization (CMP) system, an apparatus for reducing non-uniform stretch of a belt used in the CMP system as recited in claim 1, wherein a force applicator is configured to supply a pressing motion to push the compensating roller against the belt.
- 7. In a chemical mechanical planarization (CMP) system, an apparatus for reducing non-uniform stretch of a belt used in the CMP system as recited in claim 1, wherein the compensating roller is made from one of a polyurethane material and a hard rubber material.
- 8. In a chemical mechanical planarization (CMP) system, an apparatus for reducing non-uniform stretch of a belt used in the CMP system, the belt extending between a first roller and a second roller to define a belt loop to be used for CMP, the belt loop having an inner surface and an outer surface, the apparatus comprising:a compensating roller having a first end and a second end, the first end and second end extending a width of the belt, the first end and the second end having a first diameter and a center of the roller having a second diameter that is less than the first diameter, the compensating roller having a symmetrically tapered shape extending between each of the first end and second end to the center; a force applicator coupled to the compensating roller, the force applicator configured to supply a pressing motion to the compensating roller; a system force controller in communication with the force applicator, the system force controller being configured to manage an amount of force utilized by the force applicator; and wherein the compensating roller is positioned inside of the belt loop, and is configured to be applied to the inner surface of the belt loop so as to reduce non-uniform stretch of the belt.
- 9. In a chemical mechanical planarization (CMP) system, an apparatus for reducing non-uniform stretch of a belt used in the CMP system as recited in claim 8, wherein the compensating roller is configured to rotate in a direction of the first roller and the second roller.
- 10. In a chemical mechanical planarization (CMP) system, an apparatus for reducing non-uniform stretch of a belt used in the CMP system as recited in claim 8, wherein the belt is a single layer polymeric polishing pad.
- 11. In a chemical mechanical planarization (CMP) system, an apparatus for reducing non-uniform stretch of a belt used in the CMP system as recited in claim 8, wherein the belt is a supported belt with polymeric polishing layer over a stainless steel layer.
- 12. In a chemical mechanical planarization (CMP) system, an apparatus for reducing non-uniform stretch of a belt used in the CMP system as recited in claim 8, wherein the belt is a multilayer belt.
- 13. In a chemical mechanical planarization (CMP) system, an apparatus for reducing non-uniform stretch of a belt used in the CMP system as recited in claim 8, wherein the compensating roller is configured to rotate in a direction of the first roller and the second roller.
- 14. In a chemical mechanical planarization (CMP) system, an apparatus for reducing non-uniform stretch of a belt used in the CMP system as recited in claim 8, wherein the compensating roller is configured to apply pressure to a first edge and a second edge of the belt.
- 15. In a chemical mechanical planarization (CMP) system, an apparatus for reducing non-uniform stretch of a belt used in the CMP system as recited in claim 8, wherein the pressing motion pushes the compensating roller against the belt.
- 16. In a chemical mechanical planarization (CMP) system, an apparatus for reducing non-uniform stretch of a belt used in the CMP system as recited in claim 8, wherein the compensating roller is made from one of a polyurethane material and a hard rubber material.
US Referenced Citations (5)